Polypropylene and its use, a process and an apparatus for the continuous production of polypropylene

Abstract

The application relates to the technical field of polymers, and discloses a kind of polypropylene and its application, a kind of method and device for continuously preparing polypropylene.The method comprises the following steps: (1) introducing a first monomer composition into a first reactor to carry out a first polymerization reaction in the presence of catalyst I, to obtain a first stream; (2) introducing the first stream and a first part of a second monomer composition into a second reactor to carry out a second polymerization reaction in the presence of catalyst II, to obtain a second stream; (3) introducing the second stream and a second part of the second monomer composition into a first gas-phase reactor to carry out a third polymerization reaction, to obtain a third stream; (4) introducing the third stream and a third part of the second monomer composition into a second gas-phase reactor to carry out a fourth polymerization reaction.The polypropylene material prepared by the method has good shear resistance and dimensional stability, and also has excellent aging resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of polymer technology, in particular to a kind of polypropylene and its application, a kind of continuous preparation method and device of polypropylene. BACKGROUND

[0002] Polypropylene (Polypropylene, for short PP) is widely used thermoplastic general-purpose plastic, in 1957 began commercial production, in recent years has become one of the fastest growing synthetic materials in the world. Compared with other general-purpose plastics, polypropylene has good comprehensive performance, such as yield strength, tensile strength and elastic modulus is high, electrical insulation and heat resistance is good, continuous use temperature can reach 120 DEG C, stress cracking resistance and chemical resistance is better, etc.

[0003] However, polypropylene also has some shortcomings, such as melt shear resistance, size inhomogeneity in post-processing process, so that its application range is limited to a certain extent. Therefore, how to strengthen the interaction between polypropylene chain has been an important content of polypropylene research.

[0004] At present, long-chain branched structure is often introduced by reaction extrusion method, by introducing functional monomers such as pentaerythritol triacrylate into its interior, although this method can overcome the defect of size inhomogeneity in polypropylene processing process to a certain extent, but small molecules may be left in the material after processing by this method, which is easy to cause material rupture in long-term aging process, and the defect of insufficient shear resistance of polypropylene cannot be overcome.

[0005] Therefore, it is of great significance to develop a method for preparing polypropylene material with good shear resistance and processing stability. SUMMARY

[0006] The purpose of the present application is to solve the problem of shear thinning in the processing of polypropylene in the prior art and the size inhomogeneity of the product.

[0007] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a method for continuous preparation of polypropylene, which is carried out in a device containing at least two gas phase reactors connected in series, comprising:

[0008] (1) introducing a first monomer composition into a first reactor in the presence of catalyst I to carry out a first polymerization reaction, to obtain a first stream;

[0009] (2) introducing the first stream and a first part of a second monomer composition into a second reactor in the presence of catalyst II to carry out a second polymerization reaction, to obtain a second stream;

[0010] (3) introducing the second stream and a second part of the second monomer composition into a first gas phase reactor to perform a third polymerization reaction, to obtain a third stream;

[0011] (4) introducing the third stream and a third part of the second monomer composition into a second gas phase reactor to perform a fourth polymerization reaction;

[0012] The catalyst I is a Ziegler-Natta catalyst, and the catalyst II is a supported metallocene catalyst;

[0013] The first monomer composition contains propylene and a diene, and the diene is at least one selected from unsymmetrical α dienes of C5-C 16 ;

[0014] The second monomer composition contains propylene and ethylene, and the weight ratio of the first part of the second monomer composition, the second part of the second monomer composition and the third part of the second monomer composition is 1:0.5-2:0.1-1.

[0015] The second aspect of the present application provides a polypropylene prepared by the method of the first aspect.

[0016] The third aspect of the present application provides an application of the polypropylene of the second aspect in injection molding parts.

[0017] The fourth aspect of the present application provides a device for continuously preparing polypropylene, which comprises:

[0018] A first reactor, wherein a catalyst I inlet, a first monomer composition inlet and a first stream outlet are arranged on the first reactor;

[0019] A second reactor, wherein a catalyst II inlet, a first part of a second monomer composition inlet, a second stream outlet and a first stream inlet in communication with the first stream outlet are arranged on the second reactor;

[0020] A first gas phase reactor, wherein a second part of a second monomer composition inlet, a third stream outlet and a second stream inlet in communication with the second stream outlet are arranged on the first gas phase reactor;

[0021] A second gas phase reactor, wherein the second gas phase reactor is connected in series with the first gas phase reactor, and a third part of a second monomer composition inlet, a fourth stream outlet and a third stream inlet in communication with the third stream outlet are arranged on the second gas phase reactor.

[0022] The polypropylene material prepared by the method of the present application not only has good melt shear stability and processing product dimensional stability, but also has excellent aging resistance. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a topography photo of the catalyst after the first polymerization reaction;

[0024] Figure 2 is a scanning electron microscope photo of the polypropylene product prepared in Example 1 of the present application at 1000x;

[0025] Figure 3 is a plot of the relationship between the tangent loss value and the shear frequency of the polypropylene products prepared in Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0026] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are provided as approximate descriptions of the ranges and are understood to be open-ended. Each range is a continuum of values between the upper and lower limits thereof and encompass every value and subrange within that range. Any single value in a range or the upper or lower limit thereof can be combined with any other episode value or limit to create a new range or in combination with any other episode value or limit to create a new range. The application is not to be limited in scope by any precise data point or any set of data points disclosed herein as merely being exemplary measures.

[0027] In the present application, the pressure is all gauge pressure unless otherwise stated.

[0028] As mentioned above, the first aspect of the present application provides a method for continuously preparing polypropylene, which is carried out in a device comprising at least two gas phase reactors connected in series, comprising:

[0029] (1) introducing a first monomer composition into the first reactor in the presence of catalyst I to carry out a first polymerization reaction, to obtain a first stream;

[0030] (2) introducing the first stream and a first part of a second monomer composition into the second reactor in the presence of catalyst II to carry out a second polymerization reaction, to obtain a second stream;

[0031] (3) introducing the second stream and a second part of the second monomer composition into the first gas phase reactor to carry out a third polymerization reaction, to obtain a third stream;

[0032] (4) introducing the third stream and a third part of the second monomer composition into the second gas phase reactor to carry out a fourth polymerization reaction;

[0033] The catalyst I is a Ziegler-Natta type catalyst, and the catalyst II is a supported metallocene catalyst;

[0034] The first monomer composition comprises propylene and a diene, and the diene is at least one selected from the group consisting of non-symmetrical alpha dienes of C5-C 16

[0035] ​The second monomer composition contains propylene and ethylene, and the weight ratio of the first part of the second monomer composition, the second part of the second monomer composition and the third part of the second monomer composition is 1:0.5-2:0.1-1.

[0036] Preferably, the diene is selected from at least one of C5-C 10 Preferably, the diene is selected from at least one of C5-C

[0037] According to a particularly preferred embodiment, the diene is selected from at least one of 7-methyl-1,6-octadiene, 9-methyl-1,8-decadiene, 2-methyl-1,4-pentadiene. The inventors have found that in this preferred case, polypropylene products with better shear stability can be prepared.

[0038] Preferably, the weight ratio of the first part of the second monomer composition, the second part of the second monomer composition and the third part of the second monomer composition is 1:0.6-0.8:0.5-0.7. The inventors have found that in this preferred case, polypropylene products with more uniform size can be prepared.

[0039] Preferably, in the first monomer composition, the molar ratio of the propylene and the diene is 1:0.01-0.2, more preferably 1:0.06-0.12. The inventors have found that in this preferred case, polypropylene products with better performance can be obtained.

[0040] Preferably, in the first part of the second monomer composition, the molar ratio of the propylene and the ethylene is 1:0.01-0.5, more preferably 1:0.01-0.3.

[0041] Preferably, in the second part of the second monomer composition, the molar ratio of the propylene and the ethylene is 1:0.01-0.3, more preferably 1:0.01-0.1.

[0042] Preferably, in the third part of the second monomer composition, the molar ratio of the propylene and the ethylene is 1:0.1-0.3, more preferably 1:0.1-0.2.

[0043] Preferably, in step (1), in the first reactor, the mass ratio of the propylene to the catalyst I is 50000-70000:1.

[0044] Preferably, in step (1), the conditions of the first polymerization reaction at least include: temperature is minus 10℃ to 10℃, pressure is 50-60bar, average residence time is 0.5-6h.

[0045] Preferably, in step (1), the method further comprises: solid-liquid separation after mixing the product from the first polymerization reaction with the first solvent.

[0046] Preferably, in step (1), the first solvent is ethanol and propane with a content weight ratio of 1:2-6.

[0047] Preferably, in step (2), the mass ratio of the propylene to the catalyst II in the second reactor is 30000-150000:1.

[0048] Preferably, in step (2), the conditions of the second polymerization reaction at least include: a temperature of 80-100℃, a pressure of 22-35 bar, and an average residence time of 0.5-3h.

[0049] Preferably, in step (3), the conditions of the third polymerization reaction at least include: a temperature of 80-100℃, a pressure of 22-35 bar, and an average residence time of 1-3h.

[0050] Preferably, in step (4), the conditions of the fourth polymerization reaction at least include: a temperature of 75-90℃, a pressure of 15-25 bar, and an average residence time of 1-2h.

[0051] Preferably, the catalyst I contains an organic aluminum compound, an external electron donor compound, an internal electron donor compound, and a titanium-containing solid active center component.

[0052] Preferably, in the catalyst I, the content molar ratio of the organic aluminum compound calculated based on aluminum element to the titanium-containing solid active center component calculated based on titanium element is 1-10:1.

[0053] Preferably, the internal electron donor compound is a phthalate ester compound and / or an ether compound.

[0054] Preferably, the organic aluminum compound is selected from at least one of triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, and trihexylaluminum.

[0055] Preferably, the external electron donor compound is selected from at least one of 2-ethyl-2-butyl-1,3-dimethoxypropane, cyclohexylmethyl dimethoxysilane, diisopropyl dimethoxysilane, diisobutyl dimethoxysilane, tetraethoxysilane, diphenyl dimethoxysilane, and methylcyclohexyl dimethoxysilane.

[0056] According to a particularly preferred specific embodiment, the catalyst I is a MgCl2 supported catalyst or a VOCl3-AlEt2Cl catalyst.

[0057] Preferably, the catalyst II comprises a procatalyst, a cocatalyst and a support.

[0058] Preferably, the procatalyst is a zirconocene complex of dicyclopentadiene.

[0059] Preferably, the cocatalyst is selected from at least one of MAO, EAO, IBAO and TBAO.

[0060] Preferably, the support is silica or magnesium chloride.

[0061] According to one particularly preferred embodiment, the catalyst II is a MAO-B(C6F5)3 catalyst.

[0062] The present application does not have any particular requirement for the preparation method of the catalyst II, and the catalyst II can be prepared by a method known in the art, for example, the catalyst II is prepared by fixing a homogeneous metallocene catalyst on a support.

[0063] As described above, the second aspect of the present application provides a polypropylene prepared by the method of the first aspect.

[0064] As described above, the third aspect of the present application provides an application of the polypropylene of the second aspect in injection molding parts.

[0065] As described above, the fourth aspect of the present application provides an apparatus for continuously preparing a polypropylene, which comprises:

[0066] a first reactor, wherein a catalyst I inlet, a first monomer composition inlet and a first stream outlet are arranged on the first reactor;

[0067] a second reactor, wherein a catalyst II inlet, a first part of a second monomer composition inlet, a second stream outlet and a first stream inlet in communication with the first stream outlet are arranged on the second reactor;

[0068] a first gas phase reactor, wherein a second part of the second monomer composition inlet, a third stream outlet and a second stream inlet in communication with the second stream outlet are arranged on the first gas phase reactor;

[0069] a second gas phase reactor, wherein the second gas phase reactor is connected in series with the first gas phase reactor, and a third part of the second monomer composition inlet, a fourth stream outlet and a third stream inlet in communication with the third stream outlet are arranged on the second gas phase reactor.

[0070] According to one particularly preferred embodiment, the first reactor and the second reactor are both loop reactors.

[0071] According to one particularly preferred embodiment, the first gas phase reactor and the second gas phase reactor are both fluidized bed reactors.

[0072] The present application will be described in detail below by way of examples. In the following examples, the various raw materials used are commercially available, unless otherwise specified.

[0073] The first polymerization reaction is carried out in a small loop reactor, the second polymerization reaction is carried out in a slurry loop reactor, and the third and fourth polymerization reactions are carried out in gas phase fluidized bed reactors;

[0074] Propylene: purity of 99.95wt%, produced by Beijing Yanshan Petrochemical Co., Ltd. of China Petroleum and Chemical Corporation;

[0075] Ethylene: purity of 99.95wt%, produced by Beijing Yanshan Petrochemical Co., Ltd. of China Petroleum and Chemical Corporation;

[0076] Diolefin-1: 7-methyl-1,6-octadiene, purchased from Hubei Qifei Pharmaceutical Chemical Co., Ltd.;

[0077] Diolefin-2: 2-methyl-1,4-pentadiene, purchased from Aldrich Reagent Company;

[0078] Catalyst I-1: the internal electron donor is di-n-butyl phthalate, the external electron donor compound is 2-ethyl-2-butyl-1,3-dimethoxypropane, and the organic aluminum compound is triethylaluminum. The content molar ratio of the titanium-containing solid active center component calculated based on titanium element and the organic aluminum compound calculated based on aluminum element is 1:3;

[0079] Catalyst I-2: similar to catalyst-1, except that the external electron donor compound is cyclohexylmethyl dimethoxysilane;

[0080] Catalyst I-3: similar to catalyst-1, except that the external electron donor compound is diisobutyl dimethoxysilane;

[0081] Catalyst II-1: MAO-B(C6F5)3 catalyst, purchased from DOW Chemical Company, USA;

[0082] The polymer-related data in the examples and comparative examples are obtained according to the following test methods:

[0083] Melt flow rate: detected according to the method specified in national standard GB / T 3682-2000;

[0084] Shore hardness: detected according to the method specified in national standard GB / T 2411-2008, 15 seconds reading;

[0085] Tensile yield stress: the method is detected according to the national standard GB / T 1040.2-2006;

[0086] Oxidation induction time: the method is detected according to the national standard GB / T 17391-1998, and the test temperature is 210℃;

[0087] Yellow index: the method is detected according to the standard HG / T 3862-2006;

[0088] Specular gloss: the method is detected according to the national standard GB / T 8807-1988; the total shrinkage (Sγ p ) parallel to the melt flow direction and the total shrinkage (Sγ n ) perpendicular to the melt flow direction are detected according to the national standard GB / T 17037.4-2003.

[0089] Example 1

[0090] The embodiment provides a method for continuously preparing polypropylene, and the method comprises the following steps:

[0091] (1) introducing propylene and diene-1 with a molar ratio of 1:0.1 into a small loop reactor under the conditions of a temperature of 0℃ and a pressure of 50 bar, adding catalyst I-1 to perform a first polymerization reaction, wherein the mass ratio of the propylene to the catalyst I-1 is 50000:1, the average residence time of polymerization is 3h, polypropylene particles are obtained, the polypropylene particles are mixed with a first solvent (1wt% ethanol and 99wt% propane with a content weight ratio of 1:3) and then filtered to obtain a first stream containing the polypropylene particles;

[0092] (2) introducing a first part of a second monomer composition (propylene and ethylene with a molar ratio of 1:0.2) and the first stream obtained in the foregoing into a slurry loop reactor under the conditions of a temperature of 80℃ and a pressure of 22 bar, and adding catalyst II-1 to perform a second polymerization reaction, wherein the mass ratio of the propylene to the catalyst II-1 is 100000:1, the average residence time of polymerization is 1h, and a second stream is obtained;

[0093] (3) introducing the second stream obtained in the foregoing and a second part of the second monomer composition (propylene and ethylene with a molar ratio of 1:0.1) into a first gas-phase fluidized bed reactor under the conditions of a temperature of 80℃ and a pressure of 22 bar to perform a third polymerization reaction, and the average residence time of polymerization is 1.5h;

[0094] (4) introducing the second stream and the third part of the second monomer composition (molar ratio of propylene and ethylene is 1:0.1) obtained in the preceding step into a second gas-phase fluidized bed reactor for a fourth polymerization reaction at a temperature of 75°C and a pressure of 15 bar, with a polymerization average residence time of 1.5 h, to obtain a polypropylene S1;

[0095] The first part of the second monomer composition, the second part of the second monomer composition and the third part of the second monomer composition are used in a weight ratio of 1:0.6:0.6.

[0096] The properties of the obtained product are shown in Table 1.

[0097] Example 2

[0098] The present example provides a method for continuously preparing polypropylene, which comprises:

[0099] (1) introducing propylene and diene-2 in a molar ratio of 1:0.08 into a small loop reactor at a temperature of minus 10°C and a pressure of 60 bar, adding catalyst I-2 for a first polymerization reaction, wherein the mass ratio of the propylene to catalyst I-2 is 70000:1, and the polymerization average residence time is 2 h, and then mixing the polypropylene particles with a first solvent (1wt% ethanol and 99wt% propane in a content weight ratio of 1:5) and filtering to obtain a first stream containing polypropylene particles;

[0100] (2) introducing a first part of a second monomer composition (molar ratio of propylene and ethylene is 1:0.3) and the first stream obtained in the preceding step into a slurry loop reactor at a temperature of 100°C and a pressure of 35 bar, and adding catalyst II-1 for a second polymerization reaction, wherein the mass ratio of the propylene to catalyst II-1 is 90000:1, and the polymerization average residence time is 0.5 h, to obtain a second stream;

[0101] (3) introducing the second stream obtained in the preceding step and a second part of the second monomer composition (molar ratio of propylene and ethylene is 1:0.05) into a first gas-phase fluidized bed reactor for a third polymerization reaction at a temperature of 90°C and a pressure of 35 bar, with a polymerization average residence time of 2 h;

[0102] (4) introducing the second stream obtained in the preceding step and a third part of the second monomer composition (molar ratio of propylene and ethylene is 1:0.2) into a second gas-phase fluidized bed reactor for a fourth polymerization reaction at a temperature of 90°C and a pressure of 25 bar, with a polymerization average residence time of 1.7 h, to obtain a polypropylene S2;

[0103] The first part of the second monomer composition, the second part of the second monomer composition, and the third part of the second monomer composition are used in a weight ratio of 1:0.8:0.5.

[0104] The properties of the resulting product are shown in Table 1.

[0105] Example 3

[0106] The present example provides a method for continuously preparing polypropylene, the method comprising:

[0107] (1) introducing propylene and diene-2 in a molar ratio of 1:0.06 into a small loop reactor at a temperature of 10°C and a pressure of 55 bar, adding catalyst I-3 to perform a first polymerization reaction, wherein the mass ratio of the propylene to catalyst I-3 is 50000:1, and the average residence time of polymerization is 1 h, and then performing contact mixing of the polypropylene particles with a first solvent (1 wt% ethanol and 99 wt% propane in a content weight ratio of 1:5) and filtering to obtain a first stream containing polypropylene particles;

[0108] (2) introducing a first part of a second monomer composition (propylene and ethylene in a molar ratio of 1:0.1) and the first stream obtained above into a slurry loop reactor at a temperature of 90°C and a pressure of 30 bar, and adding catalyst II-1 to perform a second polymerization reaction, wherein the mass ratio of the propylene to catalyst II-1 is 50000:1, and the average residence time of polymerization is 1 h, to obtain a second stream;

[0109] (3) introducing the second stream obtained above and a second part of the second monomer composition (propylene and ethylene in a molar ratio of 1:0.01) into a first gas-phase fluidized bed reactor at a temperature of 100°C and a pressure of 28 bar to perform a third polymerization reaction, and the average residence time of polymerization is 2 h;

[0110] (4) introducing the second stream obtained above and a third part of the second monomer composition (propylene and ethylene in a molar ratio of 1:0.15) into a second gas-phase fluidized bed reactor at a temperature of 80°C and a pressure of 20 bar to perform a fourth polymerization reaction, and the average residence time of polymerization is 1 h, to obtain polypropylene S3;

[0111] The first part of the second monomer composition, the second part of the second monomer composition, and the third part of the second monomer composition are used in a weight ratio of 1:0.7:0.6.

[0112] The properties of the resulting product are shown in Table 1.

[0113] Example 4

[0114] This example refers to the method of example 3, except that in step (1) the molar ratio of the propylene to the diene-1 used in step (1) is 1 :0.01.

[0115] The remaining steps are the same as in example 3 to obtain polypropylene S4.

[0116] The properties of the obtained product are shown in table 1.

[0117] Example 5

[0118] This example refers to the method of example 3, except that in step (1) the molar ratio of the propylene to the diene-1 used in step (1) is 1 :0.19.

[0119] The remaining steps are the same as in example 3 to obtain polypropylene S5.

[0120] The properties of the obtained product are shown in table 1.

[0121] Example 6

[0122] This example refers to the method of example 3, except that the weight ratio of the first portion of the second monomer composition, the second portion of the second monomer composition and the third portion of the second monomer composition is 1 :0.5:0.8.

[0123] The remaining steps are the same as in example 3 to obtain polypropylene S6.

[0124] The properties of the obtained product are shown in table 1.

[0125] Example 7

[0126] This example refers to the method of example 3, except that the weight ratio of the first portion of the second monomer composition, the second portion of the second monomer composition and the third portion of the second monomer composition is 1 :0.5:0.1.

[0127] The remaining steps are the same as in example 3 to obtain polypropylene S7.

[0128] The properties of the obtained product are shown in table 1.

[0129] Comparative example 1 (using screw extrusion method)

[0130] This comparative example uses a screw extrusion method to prepare polypropylene, the specific steps include:

[0131] (1) 0.1 g of initiator dicumyl peroxide, 1 g of grafting monomer pentaerythritol triacrylate and 0.1 g of radical activity regulator zinc dithiocarbamate are dissolved in an appropriate amount of acetone to obtain a mixed solution:

[0132] (2) Then the obtained mixture was evenly sprayed on the surface of 100 g of polypropylene particles, antioxidant B215 was added and mixed evenly, and then placed in a vacuum oven at 80°C for 2 hours, and then added into a twin-screw extruder with a screw length-diameter ratio of 35, the temperature of each section of the extruder was 160°C, 170°C, 175°C, 170°C, and 165°C, the screw rotation speed was 70 r / min, to obtain polypropylene DS1. The properties of the obtained product are shown in Table 1.

[0133] Comparative Example 2

[0134] The present comparative example refers to the method of Example 3, except that the weight ratio of the amount of use of the first part of the second monomer composition, the second part of the second monomer composition, and the third part of the second monomer composition is 1:0.3:2.

[0135] The remaining steps are the same as those of Example 3, to obtain polypropylene DS2.

[0136] The properties of the obtained product are shown in Table 1.

[0137] Comparative Example 3

[0138] The present comparative example refers to the method of Example 3, except that the weight ratio of the amount of use of the first part of the second monomer composition, the second part of the second monomer composition, and the third part of the second monomer composition is 1:3:0.01.

[0139] The remaining steps are the same as those of Example 3, to obtain polypropylene DS3.

[0140] The properties of the obtained product are shown in Table 1.

[0141] Table 1

[0142]

[0143] Table 1 (continued)

[0144]

[0145]

[0146] As can be seen from the results in Table 1, the polypropylene prepared by the method of the present application has a high long-chain branch content and a high melt tensile tension, and at the same time, the melt index of the polypropylene prepared in the examples of the present application does not change substantially before and after screw extrusion, while the melt index in the comparative examples is greatly improved, indicating that the polypropylene prepared by the method of the present application has excellent dimensional stability.

[0147] Test Example 1

[0148] The polypropylene products obtained in the examples and comparative examples were injection molded to prepare the desired samples, and the samples were post-processed respectively. The thermal elongation permanent deformation properties of the post-treated polypropylene samples were then tested. The specific test results are shown in Table 2.

[0149] The post-treatment method is: treating the sample in water vapor at 120°C for 30 minutes.

[0150] The thermal expansion permanent deformation performance is tested using the method specified in the national standard GB / T 2951-2008.

[0151] Table 2

[0152] Hot set permanent deformation / % Example 1 0 Example 2 0 Example 3 0 Example 4 0 Example 5 -0.3 Example 6 -0.4 Example 7 -0.2 Comparative Example 1 -7.85 Comparative Example 2 -8.23 Comparative Example 3 -3.67

[0153] It can be seen from the results in Table 2 that, under the conditions of preferred diene species, the polypropylene prepared by the method of the present invention exhibits more excellent elastomeric properties.

[0154] Test Example 2

[0155] The polypropylene products prepared in Example 1, Example 3, Example 5 and Comparative Example 1 were tested for glue yield. The specific test results are shown in Table 3.

[0156] The method for detecting the amount of glue output is to use an extruder from Maillefer to extrude the polypropylene material in a molten state at a speed of 5-50 rpm, and to weigh the extrudate at this speed at a fixed time.

[0157] Table 3

[0158] Average gum output / g / min Example 1 Example 3 Example 5 Comparative Example 1 5 rpm 95 117 120 141 10 rpm 192 210 205 252 15 rpm 265 267 269 363 20 rpm 330 344 351 455 25 rpm 379 400 401 523 30 rpm 431 448 435 589 35 rpm 480 483 479 663 40 rpm 531 545 509 748 45 rpm 580 590 550 825 50 rpm 600 620 570 916

[0159] As can be seen from Table 3, the average glue output of the polypropylene prepared by the method of the present invention increases with the increase of the screw speed, and shows an overall stable growth. However, the average glue output of the polypropylene prepared in Comparative Example 1 increases significantly with the increase of the screw speed, indicating that the polypropylene polymer chain prepared in Comparative Example 1 is broken after shearing.

[0160] The present invention provides, by way of example, a morphological photograph of the catalyst after the first polymerization reaction of the present invention, scanning electron microscope images of the polypropylene product slices prepared in Example 1 of the present invention at 1000× and 2000×, and a graph showing the relationship between the loss tangent value and the shear frequency of the polypropylene products prepared in Example 1 of the present invention and Comparative Example 1, respectively. Figures 1-3 .

[0161] in, Figure 1 This is a morphology photograph of the catalyst after the first polymerization reaction of the present invention. Figure 2is a scanning electron microscope image of the polypropylene product slice prepared in Example 1 of the present application at 1000x, Figure 3 is a graph showing the relationship between the tangent of the loss angle and the shear frequency of the polypropylene product prepared in Example 1 and Comparative Example 1 of the present application.

[0162] From Figure 1 It can be seen from the above that, after the first polymerization reaction, the catalyst is a spherical solid as a whole, the surface of the particles is rough and has pores, and the size is uniform.

[0163] From Figure 2 It can be seen from the above that the polypropylene product slice prepared in Example 1 presents a cross-network structure, the amorphous part in the molecular chain is dissolved, and the remaining part is a propylene copolymer structure.

[0164] Figure 3 In the above, (a) is a graph showing the relationship between the tangent of the loss angle and the shear frequency of the polypropylene product prepared in Comparative Example 1, and (b) is a graph showing the relationship between the tangent of the loss angle and the shear frequency of the polypropylene product prepared in Comparative Example 1. The sample melt rheological behavior research was carried out on an AR2000 flat rheometer of TA Instruments Company, and the dynamic shear test conditions were as follows: the shear frequency range was 500-0.01 rad / s.

[0165] From Figure 3 It can be seen from the above that the polymer molecular chain structure of the polypropylene product prepared by the method of the present application has changed, and has more excellent elastic properties.

[0166] The above describes the preferred embodiments of the present application in detail, but the present application is not limited thereto. Within the technical concept scope of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as the disclosed content of the present application, and all fall within the protection scope of the present application.

Claims

1. A method for continuously preparing polypropylene, characterized in that: The method is carried out in an apparatus comprising at least two gas phase reactors connected in series, comprising: (1) In the presence of catalyst I, introducing a first monomer composition into a first reactor to carry out a first polymerization reaction to obtain a first stream; (2) In the presence of catalyst II, introducing the first stream and the first portion of the second monomer composition into a second reactor to carry out a second polymerization reaction to obtain a second stream; (3) introducing the second stream and the second portion of the second monomer composition into the first gas phase reactor to carry out a third polymerization reaction to obtain a third stream; (4) introducing the third stream and the third portion of the second monomer composition into a second gas phase reactor to carry out a fourth polymerization reaction; The catalyst I is a Ziegler-Natta catalyst, and the catalyst II is a supported metallocene catalyst; The first monomer composition contains propylene and diene, and the diene is selected from C5-C 16 At least one of the asymmetric α-dienes; in the first monomer composition, the molar ratio of the propylene to the diene is 1:0.06-0.12; The second monomer composition contains propylene and ethylene, and the weight ratio of the first part of the second monomer composition, the second part of the second monomer composition and the third part of the second monomer composition is 1:0.6-0.8:0.5-0.

7.

2. The method according to claim 1, wherein The diene is selected from C5-C 10 At least one of the asymmetric alpha dienes.

3. The method according to claim 1 or 2, characterized in that The diene is selected from at least one of 7-methyl-1,6-octadiene, 9-methyl-1,8-decadiene, and 2-methyl-1,4-pentadiene.

4. The method according to claim 1 or 2, wherein: In the first part of the second monomer composition, the molar ratio of the propylene to the ethylene is 1:0.01-0.

5.

5. The method according to claim 4, wherein In the first part of the second monomer composition, the molar ratio of the propylene to the ethylene is 1:0.01-0.

3.

6. The method according to claim 5, wherein: In the second part of the second monomer composition, the molar ratio of the propylene to the ethylene is 1:0.01-0.

3.

7. The method according to claim 6, wherein: In the second part of the second monomer composition, the molar ratio of the propylene to the ethylene is 1:0.01-0.

1.

8. The method according to claim 7, wherein: In the third part of the second monomer composition, the molar ratio of the propylene to the ethylene is 1:0.1-0.

3.

9. The method according to claim 8, wherein In the third part of the second monomer composition, the molar ratio of the propylene to the ethylene is 0.1-0.

2.

10. The method according to claim 1 or 2, wherein: In step (1), the conditions of the first polymerization reaction include at least: a temperature of -10°C to 10°C, a pressure of 50-60 bar, and an average residence time of 0.5-6 hours.

11. The method according to claim 1 or 2, wherein: In step (2), the conditions of the second polymerization reaction include at least: a temperature of 80-100° C., a pressure of 22-35 bar, and an average residence time of 0.5-3 h.

12. The method according to claim 1 or 2, wherein: In step (3), the conditions of the third polymerization reaction include at least: a temperature of 80-100° C., a pressure of 22-35 bar, and an average residence time of 1-3 h.

13. The method according to claim 1 or 2, wherein: In step (4), the conditions of the fourth polymerization reaction include at least: a temperature of 75-90° C., a pressure of 15-25 bar, and an average residence time of 1-2 h.

14. The method according to claim 1 or 2, wherein: The catalyst I contains an organic aluminum compound, an external electron donor compound, an internal electron donor compound, and a titanium-containing solid active center component.

15. The method according to claim 14, wherein In the catalyst I, the molar ratio of the organic aluminum compound calculated as aluminum element to the titanium-containing solid active center component calculated as titanium element is 1-10:

1.

16. The method according to claim 14, wherein The internal electron donor compound is a phthalate ester and / or ether compound.

17. The method according to claim 14, wherein: The organoaluminum compound is at least one selected from triethylaluminum, triisobutylaluminum, tri-n-butylaluminum and trihexylaluminum.

18. The method according to claim 14, wherein The external electron donor compound is selected from at least one of 2-ethyl-2-butyl-1,3-dimethoxypropane, cyclohexylmethyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, tetraethoxysilane, diphenyldimethoxysilane, and methylcyclohexyldimethoxysilane.

19. The method according to claim 1 or 2, wherein: The catalyst II contains a main catalyst, a co-catalyst and a carrier.

20. The method according to claim 19, wherein The main catalyst is a dicyclopentadiene zirconium complex.

21. The method according to claim 19, wherein The co-catalyst is selected from at least one of MAO, EAO, IBAO and TBAO.

22. The method according to claim 19, wherein The carrier is silicon dioxide or magnesium chloride.

23. Polypropylene obtained by the process according to any one of claims 1 to 22.

24. Use of the polypropylene according to claim 23 in injection molded parts.

25. A device for continuously preparing polypropylene, characterized in that: The device is used to implement the method for continuously preparing polypropylene according to any one of claims 1 to 22, and the device comprises: A first reactor, wherein the first reactor is provided with a catalyst I inlet, a first monomer composition inlet, and a first logistics outlet; a second reactor, wherein the second reactor is provided with a catalyst II inlet, a first portion of a second monomer composition inlet, a second logistics outlet, and a first logistics inlet connected to the first logistics outlet; a first gas phase reactor, wherein the first gas phase reactor is provided with an inlet for the second portion of the second monomer composition, a third logistics outlet, and a second logistics inlet communicating with the second logistics outlet; The second gas phase reactor is connected in series with the first gas phase reactor, and is provided with an inlet for the third portion of the second monomer composition, a fourth logistics outlet, and a third logistics inlet connected to the third logistics outlet.

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