Propylene polymer directly prepared from polymerization reaction and preparation method thereof

Abstract

The invention belongs to the technical field of propylene polymerization, and particularly relates to a propylene polymer directly prepared by polymerization reaction and a preparation method thereof, and the method comprises the following steps: (i) in the presence of a polymerization catalyst and hydrogen, propylene or propylene and optional one or more comonomers are subjected to a first-stage (co) polymerization reaction for 0.1-10 hours, preparing a material flow containing a polypropylene-I component; (ii) continuing to polymerize at least a portion or all of the stream containing the polypropylene-I component in a line located outside the reactor in the presence of a hydrogenation catalyst for 0.01-3 hours; then stopping the reaction to obtain a propylene polymer containing an ultra-high molecular weight polypropylene component; wherein the molar ratio of the hydrogenation catalyst to the total hydrogen in the reactor is 1 / 10000-1 / 100. According to the invention, the properties (including melt strength, tensile strength, impact strength, bending strength and the like) of a polypropylene product are remarkably improved while good processability is maintained.

Description

Technical Field

[0001] The invention belongs to the technical field of propylene polymerization, and in particular relates to a propylene polymer with significantly improved performance directly prepared from a polymerization reaction and a preparation method thereof. Background Art

[0002] The performance of polypropylene is directly related to its molecular weight, molecular weight distribution width, molecular chain stereoregularity, type and content of comonomers, etc. Generally, the molecular chain structure of polypropylene is linear and semi-crystalline, and the molecular weight of common polypropylene is relatively small (100,000 to 300,000 or 400,000). Studies have shown that with the increase of molecular weight, the rigidity, toughness and melt strength of polypropylene will be improved; adding high molecular weight polypropylene components to ordinary polypropylene can widen the molecular weight distribution, improve the crystallization rate and processing performance. However, if the proportion of high molecular weight polypropylene components is too high, the processability of the material will decrease rapidly. If the difference between the molecular weight of the added component and the molecular weight of ordinary polypropylene is too large, it will also lead to problems with dispersion uniformity due to compatibility.

[0003] In this regard, some improvement studies have been conducted in this field.

[0004] Patent documents CN102134291A, CN102884093A, CN102816269A and CN105623077A all disclose a method of using two reactors in series, using a traditional Ziegler-Natta catalyst, asymmetric addition of external electron donors and asymmetric hydrogen regulation technology, and directly polymerizing in the reactor to obtain a propylene homopolymer or propylene-ethylene copolymer with a wide molecular weight distribution and high melt strength; first, a dicyclopentyldimethoxysilane (D-donor) type hydrogen-insensitive, high isotacticity external electron donor is added to the first reactor to prepare a high molecular weight propylene homopolymer or copolymer under hydrogen-free or low hydrogen conditions; then a large amount of tetraethoxysilane (TEOS) type hydrogen-sensitive external electron donor is added to the second reactor to prepare a low molecular weight propylene homopolymer or copolymer under high hydrogen concentration, and finally a propylene homopolymer, random copolymer or impact copolymer product with a melt index of 2.0 to 3.0 g / 10 min and a melt strength of 0.8 to 1.0 N is obtained. In this method, the load ratio of the two reactors is 30:70 to 70:30.

[0005] In the methods disclosed in the prior art as above, whether it is asymmetric hydrogenation or the method of adding an external electron donor, there are great limitations. When an external electron donor with a lower hydrogen adjustment sensitivity is used in the catalyst system, although a higher molecular weight polymer can be obtained when producing a higher molecular weight component, when producing a lower molecular weight component, due to its insensitivity to hydrogen adjustment, an extremely high hydrogen content is required to meet the actual requirements; and when an external electron donor with a higher hydrogen adjustment sensitivity is used in the catalyst system, although the amount of hydrogen used is less when producing a lower molecular weight component, when producing a higher molecular weight component, its molecular weight cannot meet the requirements, thereby affecting the mechanical properties of the final product. As a result, it has to rely on a complex process, that is, matching external electron donors with different hydrogen adjustment sensitivities and hydrogen concentrations in different reactors to achieve the purpose of preparing high melt strength polypropylene.

[0006] Patent documents US 6875826B1 and US 7365136B2 both disclose a method for preparing a propylene homopolymer or copolymer that can be used for foaming and thermoforming. In a series of annular tube-gas phase polymerization reactors, the same Ziegler-Natta or metallocene catalyst and the same external electron donor (dicyclopentyldimethoxysilane or cyclohexylmethyldimethoxysilane) are selected to prepare a wide distribution polypropylene by changing the amount of hydrogen in different reactors. Usually, no hydrogen is added in the first reactor to produce a high molecular weight component with MFR<0.1g / 10min, and the weight proportion is 5-50wt%; an appropriate amount of hydrogen is added in the second reactor to produce medium and low molecular weight components with MFR>0.5g / 10min, and the weight proportion is 50-95wt%; the obtained polypropylene has the characteristics of high melt strength. Although it is possible to try to adjust the load ratio of the two reactors to 5:95-95:5, due to the difficulty of such a design in actual operation, the proportion of high molecular weight components in the embodiment is controlled to be not less than 20%.

[0007] Patent documents US9556288B2 and US9403921B2 mention that in a dual-reactor series polyolefin production process, the slurry at the outlet of the first reactor passes through a separator to separate part of the chain transfer agent, thereby reducing the concentration of the chain transfer agent in the material. The material then enters the second reactor to continue reacting to generate higher molecular weight components. No mention is made of the use of a hydrogenation catalyst to reduce the hydrogen in the material.

[0008] The methods of the prior art all have a common defect, that is, the content of the generated high molecular weight component is relatively high, generally above 15%. If the content of the high molecular weight polymer component in the polypropylene product is too high, the processability of the obtained polypropylene material will be affected.

[0009] In view of this, it becomes a topic worthy of research to continue to explore the process and method of preparing polypropylene with excellent processability and high melt strength by direct polymerization. Summary of the invention

[0010] In view of some problems existing in the prior art for preparing polypropylene, the object of the present invention is to provide a propylene polymer directly prepared from a polymerization reaction and a preparation method thereof; by setting a pipeline outside the reactor at the end of the polymerization reaction and adding a hydrogenation catalyst thereto and continuing the polymerization reaction, a polypropylene product containing a relatively low content of ultra-high molecular weight components is obtained, while maintaining good processing performance, the performance of the polypropylene product (including melt strength, tensile strength, impact strength, flexural strength, etc.) is significantly improved.

[0011] In order to achieve the above object, the present invention provides the following technical solutions:

[0012] In a first aspect, a propylene polymer directly obtained from a polymerization reaction is provided, wherein the propylene polymer comprises an ultra-high molecular weight polypropylene component having a molecular weight MW ≥ 10,000,000;

[0013] The content of the ultra-high molecular weight polypropylene component is 0.03-5.00wt% (e.g., 0.04wt%, 0.05wt%, 0.06wt%, 0.08wt%, 0.10wt%, 0.20wt%, 0.50wt%, 1.00wt%, 2.50wt%, 4.00wt%), preferably 0.05-2.00wt%;

[0014] The ratio of the number average molecular weight Mn of the ultrahigh molecular weight polypropylene component to the peak molecular weight Mp of the propylene polymer is Mn (MW ≥ 10,000,000) / Mp ≥ 10, for example, 15, 20, 35, 40, 50, 60, 80, 100, 120, 150, preferably ≥ 30.

[0015] According to the propylene polymer provided by the present invention, in some embodiments, the melt strength of the propylene polymer is greater than or equal to 2.0 cN, for example, 2.5 cN, 4 cN, 5 cN, 8 cN, 10 cN, 15 cN, preferably 2.5-10 cN.

[0016] According to the propylene polymer provided by the present invention, in some embodiments, the melt flow rate MFR of the propylene polymer is 0.01g / 10min to 10000g / 10min (for example, 0.05g / 10min, 0.1g / 10min, 0.5g / 10min, 1g / 10min, 5g / 10min, 10g / 10min, 50g / 10min, 100g / 10min, 400g / 10min, 500g / 10min, 1000g / 10min, 5000g / 10min), preferably 0.1g / 10min to 300g / 10min, more preferably 0.5g / 10min to 200g / 10min.

[0017] In a second aspect, there is provided a method for preparing a propylene polymer directly from a polymerization reaction, using two or more polymerization reaction stages arranged in sequence; the method comprising the steps of:

[0018] (i) in the presence of a polymerization catalyst and hydrogen, propylene or propylene and optionally one or more comonomers are subjected to a first stage (co)polymerization reaction for 0.1 to 10 hours (e.g., 0.5 hours, 1 hour, 2 hours, 4 hours, 8 hours) to prepare a stream containing a polypropylene-I component;

[0019] (ii) after the first stage (co)polymerization reaction, at least a portion or all of the stream containing the polypropylene-I component (the stream may include propylene, hydrogen, polypropylene component I, polymerization catalyst, etc.) is further polymerized in a pipeline located outside the reactor in the presence of a hydrogenation catalyst for 0.01-3 hours (e.g., 0.05 hours, 0.1 hours, 0.2 hours, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours) to obtain an ultra-high molecular weight polypropylene (UHMWPP) component having a molecular weight MW ≥ 10,000,000;

[0020] Then, the reaction is stopped to obtain the propylene polymer containing an ultra-high molecular weight polypropylene (UHMWPP) component;

[0021] The molar ratio of the hydrogenation catalyst to the total amount of hydrogen contained in the polymerization system is 1 / 10000-1 / 100, for example, 1 / 8000, 1 / 6000, 1 / 5000, 1 / 4000, 1 / 2000, 1 / 1000, 1 / 500, 1 / 200, 1 / 150, preferably 1 / 10000-1 / 1000.

[0022] According to the preparation method provided by the present invention, in the polymerization reaction, propylene monomer can be polymerized, or propylene monomer and one or more comonomers can be copolymerized. In some embodiments, the comonomer can be ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-nonene, 1-decene, etc., or a mixture of any two or more of these comonomers.

[0023] In the present invention, the polymerization catalyst used in propylene (co)polymerization includes but is not limited to Ziegler-Natta type catalysts, and such catalysts may generally include:

[0024] (a) an active solid catalyst component, preferably a titanium-containing solid catalyst active component; (b) an organoaluminum compound as a co-catalyst component; and optionally, (c) an external electron donor component.

[0025] The ratio of the active solid catalyst component to the organoaluminum compound can be 1:5 to 1:400 (e.g., 1:10, 1:50, 1:120, 1:200, 1:300), preferably 1:25 to 1:100, calculated by Ti / Al molar ratio.

[0026] The optional active solid catalyst component (active main catalyst component) includes commercially available SUG catalyst, SAL catalyst, or other catalysts containing both titanium chloride and magnesium chloride, etc.

[0027] The organoaluminum compound as the co-catalyst component is preferably an alkylaluminum compound, more preferably a trialkylaluminum, such as triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, methylaluminoxane (MAO), modified methylaluminoxane (MMAO), and the like.

[0028] The compound used as the external electron donor component can be various electron donating compounds, including but not limited to alkoxy-substituted silane compounds; for example, its general formula is SiR n (OR') 4-n , where:

[0029] 0≤n≤2,

[0030] R and R' are the same or different, and are independently selected from an alkyl group, a cycloalkyl group, an aryl group, a haloalkyl group, a nitrogen-containing group, etc. R can also be a halogen or a hydrogen atom; specifically, they may include but are not limited to tetramethoxysilane, tetraethoxysilane (TEOS), dimethyldimethoxysilane, dimethyldiethoxysilane, methyl tert-butyldimethoxysilane, methylisopropyldimethoxysilane, diphenoxydimethoxysilane, vinyltrimethoxysilane, methylcyclohexyldimethoxysilane, ethylcyclohexyldimethoxysilane, di-n-propyldimethoxysilane, diisopropyldimethoxysilane, di-n-butyldimethoxysilane, diisobutyldimethoxysilane, alkane, di-tert-butyldimethoxysilane, dicyclopentyldimethoxysilane (D-donor), cyclopentyltrimethoxysilane, isopropyltrimethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, ethyltriethoxysilane, diethylaminotriethoxysilane, cyclohexylpyrrolidinedimethoxysilane, bis(pyrrolidine)-dimethoxysilane, bis(perhydroisoquinoline)dimethoxysilane, 2-ethylpiperidinyl-2-tert-butyldimethoxysilane, (1,1,1-trifluoro-2-propyl)-2-ethylpiperidinyldimethoxysilane and (1,1,1-trifluoro-2-propyl)-methyldimethoxysilane, etc. Preferred are dicyclopentyldimethoxysilane (D-donor), methylcyclohexyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, tetraethoxysilane (TEOS), and diethylaminotriethoxysilane.

[0031] The amount of the external electron donor component in the polymerization catalyst can be selected according to conventional methods in the art and will not be described in detail here.

[0032] In some embodiments, the hydrogenation catalyst is a mixture of a metal organic compound and an alkyl aluminum compound.

[0033] In some embodiments, the metal organic compound has a general formula of R(R')-MX(X'), wherein:

[0034] R, R' are each independently an unsubstituted or substituted cyclopentadienyl, indenyl, or fluorenyl group, wherein the substituent is preferably selected from methyl, ethyl, propyl, butyl, or cycloalkyl group;

[0035] M is a transition metal element, preferably one or more selected from Fe, Ti, Zr, Cr and Mn;

[0036] X, X' are each independently a halogen atom, an alkyl group or an alkoxy group;

[0037] In some embodiments, in the mixture, the molar ratio of aluminum in the alkyl aluminum compound to the metal organic compound ranges from 5.5 to 10.0:1 (e.g., 6.0:1, 6.5.0:1, 7.0:1, 7.5:1, 8.5:1, 9.0:1, 9.5:1), preferably 5.5 to 8.0:1.

[0038] In some embodiments, the metal organic compound is selected from one or more of bis(cyclopentadienyl)titanium dichloride, bis(cyclopentadienyl)titanium dibromide, bis(cyclopentadienyl)methoxytitanium chloride, bis(cyclopentadienyl)ethoxytitanium chloride, bis(cyclopentadienyl)phenoxytitanium chloride, bis(cyclopentadienyl)dimethyltitanium, bis(cyclopentadienyl)diethyltitanium, diindenyltitanium dichloride, diindenyltitanium dibromide, diindenyldimethyltitanium, diindenyldiethyltitanium, bis(cyclopentadienyl)zirconium dichloride, bis(cyclopentadienyl)zirconium dibromide, bis(cyclopentadienyl)dimethylzirconium and bis(cyclopentadienyl)diethylzirconium, preferably selected from one or two of bis(cyclopentadienyl)titanium dichloride and bis(cyclopentadienyl)diethyltitanium, more preferably Cp2TiCl2.

[0039] In some embodiments, the alkylaluminum compound is selected from one or more of trimethylaluminum, triethylaluminum, tributylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, tridecylaluminum, dimethylaluminum monochloride, diethylaluminum monochloride, dibutylaluminum monochloride, diisobutylaluminum monochloride, methylaluminoxane (MAO) and modified methylaluminoxane (MMAO), preferably selected from triethylaluminum and / or methylaluminoxane.

[0040] In some embodiments, the hydrogenation catalyst is a mixture of Cp2TiCl2 and an alkyl aluminum compound; wherein the molar ratio of aluminum in the alkyl aluminum compound to Cp2TiCl2 is in the range of 5.5-10.0:1 (e.g., 6.0:1, 6.5.0:1, 7.0:1, 7.5:1, 8.5:1, 9.0:1, 9.5:1), preferably 5.5-8.0:1.

[0041] In some embodiments, the polymerization reaction time of step (i) is 0.2-5 hours (eg, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 4 hours), preferably 0.3-3 hours.

[0042] In some embodiments, the polymerization reaction temperature of step (i) is 40-250°C (eg, 60°C, 80°C, 100°C, 180°C, 240°C), preferably 50-200°C.

[0043] The present invention selectively adds a hydrogenation catalyst to the material outlet of the propylene polymerization reaction end (outside a single reactor or multiple series reactors for propylene polymerization) or any point on the transmission pipeline of the powder obtained in the first polymerization stage into the silo and continues the polymerization reaction, removes the chain transfer agent hydrogen remaining in the powder by a small amount of hydrogenation catalyst, and the reaction material no longer enters any reactor.

[0044] In some embodiments, in step (ii), the length of the pipeline outside the reactor is 0.1 to 50 meters, for example, 0.5 meters, 1 meter, 2 meters, 4 meters, 5 meters, 10 meters, 20 meters, or 40 meters.

[0045] The pipeline may include a pipeline as a polymerization reaction site outside a single reactor or multiple series reactors for propylene polymerization and a connecting pipeline connected to a subsequent separation device. The material of the pipeline may be a conventional material in the art.

[0046] In some embodiments, in step (ii), a discharge pipeline is provided at the end outside a single reactor or outside multiple reactors in series, and the hydrogenation catalyst is added to the discharge pipeline and the polymerization reaction is continued. In the present invention, the material stream to which the hydrogenation catalyst is added in the discharge pipeline is no longer returned to the reactor, but directly enters the product with the material, and does not affect the polymerization reaction in the single reactor or multiple reactors in series.

[0047] A hydrogenation catalyst is added to an outlet pipeline outside a single reactor or multiple reactors connected in series, and the outlet pipeline is used as an additional polymerization reaction site, so that the material flow containing the polypropylene-I component discharged from the reactor of the first polymerization stage contacts with the hydrogenation catalyst and enters a gas / solid separator through a connecting pipeline of a certain length, and then undergoes catalyst deactivation and degassing treatment to obtain a propylene polymer product.

[0048] The hydrogenation catalyst may be added continuously or in pulses.

[0049] In some embodiments, the polymerization reaction time of step (ii) is 0.08-2 hours (eg, 0.1 hours, 0.5 hours, 1 hour, 1.8 hours), preferably 0.1-1.5 hours.

[0050] In some embodiments, the polymerization reaction temperature of step (ii) is 0-250°C (eg, 10°C, 30°C, 40°C, 50°C, 100°C, 150°C, 180°C, 240°C), preferably 20-200°C.

[0051] The melt strength of the propylene polymer prepared by the preparation method as described above is greater than or equal to 2.0 cN, preferably 2.5-10 cN, for example, 2.5 cN, 4 cN, 5 cN, 8 cN, 10 cN, 15 cN.

[0052] The propylene polymer prepared by the preparation method as described above has a melt flow rate MFR of 0.01 g / 10min to 10000 g / 10min (for example, 0.05 g / 10min, 0.1 g / 10min, 0.5 g / 10min, 1 g / 10min, 5 g / 10min, 10 g / 10min, 50 g / 10min, 100 g / 10min, 400 g / 10min, 500 g / 10min, 1000 g / 10min, 5000 g / 10min), preferably 0.1 g / 10min to 300 g / 10min, and more preferably 0.5 g / 10min to 200 g / 10min.

[0053] The propylene polymer prepared by the preparation method as described above contains an ultra-high molecular weight component; the molecular weight MW of the ultra-high molecular weight component is ≥10,000,000, for example, 1,000,000,000≥molecular weight MW≥10,000,000. The content of the ultra-high molecular weight component is 0.03-5.00wt% (for example, 0.04wt%, 0.05wt%, 0.06wt%, 0.08wt%, 0.10wt%, 0.20wt%, 0.50wt%, 1.00wt%, 2.50wt%, 4.00wt%), preferably 0.05-2.00wt%. The ratio of the number average molecular weight Mn of the ultrahigh molecular weight component to the peak molecular weight Mp of the propylene polymer is Mn (MW ≥ 10,000,000) / Mp ≥ 10, for example, 15, 20, 30, 40, 50, 60, 80, 100, 120, 150, preferably ≥ 30.

[0054] The outlet material of the propylene polymerization reactor contains polypropylene powder, catalyst, electron donor, propylene, comonomer, hydrogen, a small amount of propane, a small amount of nitrogen, etc. Usually, such material is still in the conditions that meet the polymerization, the catalyst still has polymerization activity, and there are certain concentrations of polymerization monomer and hydrogen in the environment, so the polymerization reaction can continue. The inventor of the present invention has found through exploration that adding a small amount of hydrogenation catalyst (such as about one thousandth to one ten-thousandth of the total hydrogen in the system) to the material at this time can consume the hydrogen in the material to the maximum extent, so that the propylene monomer and comonomer in the reactor continue to polymerize in the absence of hydrogen or near the absence of hydrogen to generate ultra-high molecular weight polypropylene or copolymer components.

[0055] Since the present invention adds a high-efficiency hydrogenation catalyst into the pipeline at the end of the polymerization reaction, it does not affect the normal operation and index control of the polymerization reactor, and can cleverly solve the shortcomings of the prior art. In addition, by selecting the position for adding the hydrogenation catalyst, the residence time of the material in the discharge pipeline (i.e., the polymerization reaction time in the presence of the hydrogenation catalyst) and related polymerization reaction conditions can be flexibly adjusted, and the amount of ultra-high molecular weight polypropylene component generated in the product can be flexibly controlled, thereby regulating the proportion of the ultra-high molecular weight polypropylene component in the final polypropylene product.

[0056] Compared with the prior art, the excellent effects of the technical solution of the present invention are at least:

[0057] By adding a small amount of hydrogenation catalyst to the powder containing the polypropylene-I component discharged from the reactor in the discharge pipeline outside the polymerization reactor at the end of the polymerization reaction, the hydrogen chain transfer agent remaining in the powder can be quickly removed, so that the propylene monomer entrained in the polypropylene powder continues to polymerize under nearly hydrogen-free conditions before separation to generate a small amount of ultra-high molecular weight polypropylene (UHMWPP) component with a molecular weight MW ≥ 10,000,000. The GPC test results show that the final product contains the UHWMPP component; by adjusting the residence time (polymerization reaction time) of the material in the reaction site of the second polymerization stage and the polymerization reaction conditions, the generation amount of the ultra-high molecular weight polypropylene component can be flexibly adjusted to control it within a low content range. The molecular weight distribution is slightly broadened to avoid the negative impact of excessive high molecular weight component content on processability; and by adjusting the amount of hydrogenation catalyst, the molecular weight of the ultra-high molecular weight polypropylene component can be adjusted to reach a molecular weight of 10,000,000 or above; thereby, a series of polypropylene products containing ultra-high molecular weight polypropylene components and different compositions can be prepared, while maintaining good processability, the performance of polypropylene products (including melt strength, tensile strength, impact strength, flexural strength, etc.) is significantly improved, higher application standards can be met, and the application fields such as extrusion foaming, coating, blow molding and thermoforming can be expanded.

[0058] Since the amount of hydrogenation catalyst and the amount of alkyl aluminum therein are controlled within a suitable range, the effect of alkyl aluminum as a chain transfer agent on the molecular weight of the ultra-high molecular weight component can be reduced, and the catalyst residue in the product can also be reduced. DETAILED DESCRIPTION

[0059] 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 described herein. For those who do not specify specific conditions in the embodiments, they are carried out according to normal conditions or the conditions recommended by the manufacturer.

[0060] <Source of raw materials>

[0061] In each example and comparative example, the catalyst A used was prepared according to Example 5 described in patent application CN101054424A, and the Ti content in the catalyst A was 3.0 wt%.

[0062] In each embodiment and comparative example, the preparation steps of the titanocene hydrogenation catalyst used are as follows: under a nitrogen atmosphere, titanocene dichloride and triethylaluminum (triethylaluminum is present in the form of a 1.0 mol / L n-hexane solution) are mixed at different molar ratios at room temperature for at least 24 hours to prepare multiple groups of mixed liquids, i.e., titanocene hydrogenation catalysts; then, 1.0 ml of each mixed liquid is taken, 33 ml of n-hexane is added to dilute and then used.

[0063] In each embodiment and comparative example, the reaction environment, material concentration, etc. in the reactor after the reaction in step (i) is completed are substantially the same as the reaction environment and material concentration, etc. in the pipeline outside the reactor. Therefore, the residence time of the material in the reactor after the hydrogenation catalyst is added in step (ii) is controlled to be the same as the residence time in the pipeline outside the reactor. The reaction effects in these two cases are substantially the same. Those skilled in the art may believe that the situation of introducing a hydrogenation catalyst into a pipeline outside the reactor can be simulated.

[0064] In each embodiment and comparative example, the relevant data of the obtained polymer product are obtained according to the following test methods:

[0065] (1) Melt flow rate (MFR): The sample to be tested was tested according to ASTM D1238;

[0066] (2) Xylene soluble content XS, wt%: The samples were tested using a fully automatic xylene soluble content tester (CRYSTEX QC) from Polymer Char Company;

[0067] (3) Molecular weight and its distribution: The samples were tested using a high temperature gel permeation chromatograph (GPC-IR6) from Polymer Char.

[0068] (4) Melt strength: The samples were tested using a RH7-2 capillary rheometer + balance from Malvern Instruments.

[0069] (5) Mechanical properties

[0070] Tensile strength: tested in accordance with GB / T 1040.2-2006;

[0071] Bending strength: tested in accordance with GB / T 9341-2008;

[0072] Impact test: Tested in accordance with GB / T 1843-2008.

[0073] Example 1

[0074] The propylene polymerization reaction was carried out in a 5L stainless steel polymerization kettle, and the specific steps were as follows:

[0075] (i) First, the reactor was purged with purified nitrogen (water <1 ppm, oxygen <1 ppm); then, 2.2 L of liquid propylene and 0.125 mol of hydrogen were added in sequence at room temperature, and the system was heated to 70° C.;

[0076] Before the temperature of the reactor reaches 70° C., 2.0 ml of a 0.5 M triethylaluminum heptane solution, 0.4 ml of a 0.5 M D-donor hexane solution and 8.1 mg of catalyst A are mixed for 5 minutes to obtain a mixture. When the temperature of the reactor reaches 70° C., the mixture is injected into the reactor through a catalyst feed pipe and a reaction timer is started to perform a polymerization reaction to generate a material flow containing a polypropylene component I.

[0077] (ii) After the reaction was carried out for 60 minutes, 25.5 ml (concentration of 4.9×10 -6 mol / ml) prepared titanocene hydrogenation catalyst (molar ratio of titanocene dichloride to triethylaluminum is 1:6), continue to maintain the temperature at 70°C and start the reaction timing, simulate the reaction in the outlet pipeline outside the reactor, in the environment including propylene, hydrogen, polypropylene component I, polymerization catalyst and other materials, and continue the reaction time for 5 minutes (i.e., in this way, simulate: the material obtained from the polymerization reaction in step i in the presence of the hydrogenation catalyst stays in the outlet pipeline outside the reactor for 5 minutes);

[0078] Then, the unreacted materials are vented, the temperature is lowered, and the reaction is stopped;

[0079] (iii) The obtained polypropylene product was vacuum dried at 30° C. for 2 hours, and then the dried polypropylene product was subjected to a performance test. The test results are shown in Table 1.

[0080] Example 2

[0081] The method and conditions for the propylene polymerization reaction are the same as those of Example 1, except that the time for the simulated material to continue reacting in the outlet pipeline outside the reactor in step (ii) is changed to 30 minutes.

[0082] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 1.

[0083] Example 3

[0084] The method and conditions for the propylene polymerization reaction are the same as those of Example 1, except that the amount of hydrogenation catalyst added in step (ii) is changed to 2.55 ml (i.e., its amount is one ten-thousandth of the total amount of hydrogen), and the time for the simulated material to continue reacting in the outlet pipeline outside the reactor is still 5 minutes.

[0085] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 1.

[0086] Example 4

[0087] The method and conditions for the propylene polymerization reaction are the same as those of Example 1, except that the amount of hydrogenation catalyst added in step (ii) is changed to 2.55 ml (i.e., its amount is one ten-thousandth of the total amount of hydrogen), and the time for the simulated material to continue reacting in the outlet pipeline outside the reactor is changed to 30 minutes.

[0088] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 1.

[0089] Comparative Example 1

[0090] The propylene polymerization reaction was carried out in a 5L stainless steel polymerization kettle, and the specific steps were as follows:

[0091] (i) First, the reactor was purged with purified nitrogen (water <1 ppm, oxygen <1 ppm); then, 2.2 L of liquid propylene and 0.125 mol of hydrogen were added in sequence at room temperature, and the system was heated to 70° C.;

[0092] Before the temperature of the reactor reaches 70° C., 2.0 ml of 0.5 M alkylaluminum heptane solution, 0.4 ml of 0.5 M D-donor hexane solution and 8.1 mg of catalyst A are mixed for 5 minutes to obtain a mixture, and when the temperature of the reactor reaches 70° C., the mixture is injected into the reactor through the catalyst feed pipe and the reaction timer is started to carry out a polymerization reaction;

[0093] (ii) After 65 minutes of reaction, the unreacted material was vented, the temperature was lowered, and the reaction was stopped;

[0094] (iii) The obtained polypropylene product was vacuum dried at 30° C. for 2 hours, and then the dried polypropylene product was subjected to a performance test. The test results are shown in Table 1.

[0095] Comparative Example 2

[0096] The method and conditions for the propylene polymerization reaction were the same as those of Comparative Example 1, except that after 90 minutes of reaction, the unreacted materials were vented, the temperature was lowered, and the reaction was stopped.

[0097] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 1.

[0098] Comparative Example 3

[0099] The propylene polymerization reaction was carried out in a 5L stainless steel polymerization kettle, and the specific steps were as follows:

[0100] (i) First, the reactor was purged with purified nitrogen (water <1 ppm, oxygen <1 ppm); then, 2.2 L of liquid propylene was added at room temperature without adding hydrogen, and the system was heated to 70° C.;

[0101] Before the temperature of the reactor reaches 70° C., 2 ml of 0.5 M alkylaluminum heptane solution, 0.4 ml of 0.5 M D-donor hexane solution and 8.1 mg of catalyst A are mixed for 5 minutes to obtain a mixture. When the temperature of the reactor reaches 70° C., the mixture is injected into the reactor through the catalyst feed pipe and the reaction timer is started to carry out polymerization reaction;

[0102] (ii) After 60 minutes of reaction, the materials were vented, the temperature was lowered, and the reaction was stopped;

[0103] (iii) The polypropylene product was taken out and vacuum dried at 30° C. for 2 hours, and then the dried polypropylene product was subjected to performance testing. The test results are shown in Table 1.

[0104] Table 1

[0105]

[0106]

[0107] Example 5

[0108] The copolymerization of propylene and ethylene was carried out in a 5L stainless steel polymerization reactor. The specific steps are as follows:

[0109] (i) First, the reactor was purged with purified nitrogen (water <1 ppm, oxygen <1 ppm); then, 2.2 L of liquid propylene and 0.20 mol of hydrogen were added in sequence at room temperature, and the system was heated to 60° C.;

[0110] Before the temperature of the reactor reaches nearly 60° C., ethylene is introduced into the reactor at a flow rate of 20 g / h, and 2.0 ml of a pre-prepared 0.5 M triethylaluminum heptane solution, 0.4 ml of a 0.5 M D-donor hexane solution and 8.1 mg of catalyst A are mixed for 5 minutes. When the temperature of the reactor reaches 60° C., the obtained mixture is injected into the reactor through a catalyst feed pipe and a reaction timer is started to perform a polymerization reaction to generate a material flow containing a polypropylene component I.

[0111] (ii) After the reaction was carried out for 60 minutes, 4.0 ml (concentration of 4.9×10 -6mol / ml) prepared titanocene hydrogenation catalyst (the molar ratio of titanocene dichloride to triethylaluminum is 1:6), continue to maintain the temperature at 60°C and start the reaction timing, simulate the reaction in the outlet pipeline outside the reactor, in the environment including propylene, hydrogen, polypropylene component I, polymerization catalyst and other materials, and continue the reaction time for 10 minutes (that is, in this way, simulate: the reaction material obtained by the polymerization reaction in step i in the presence of the hydrogenation catalyst stays in the outlet pipeline outside the reactor for 10 minutes);

[0112] Then, the unreacted materials are vented, the temperature is lowered, and the reaction is stopped;

[0113] (iii) The polypropylene product was taken out and vacuum dried at 30° C. for 2 hours, and then the dried polypropylene product was subjected to performance testing. The test results are shown in Table 2.

[0114] Example 6

[0115] The method and conditions for the copolymerization of propylene and ethylene are the same as those of Example 5, except that the time for the simulated material to continue reacting in the outlet pipeline outside the reactor in step (ii) is changed to 30 minutes.

[0116] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 2.

[0117] Example 7

[0118] The method and conditions for the copolymerization of propylene and ethylene are the same as those of Example 5, except that the time for the simulated material to continue reacting in the outlet pipeline outside the reactor in step (ii) is changed to 60 minutes.

[0119] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 2.

[0120] Comparative Example 4

[0121] The copolymerization of propylene and ethylene was carried out in a 5L stainless steel polymerization reactor. The specific steps are as follows:

[0122] (i) First, the reactor was purged with purified nitrogen (water <1 ppm, oxygen <1 ppm); then, 2.2 L of liquid propylene and 0.20 mol of hydrogen were added in sequence at room temperature, and the system was heated to 60° C.;

[0123] Before the temperature of the reactor reaches nearly 60° C., ethylene is introduced into the reactor at a flow rate of 20 g / h, and 2.0 ml of a pre-prepared 0.5 M triethylaluminum heptane solution, 0.4 ml of a 0.5 M D-donor hexane solution and 8.1 mg of catalyst A are mixed for 5 minutes. When the temperature of the reactor reaches 60° C., the obtained mixture is injected into the reactor through a catalyst feed pipe and a reaction timer is started to carry out a polymerization reaction;

[0124] (ii) After 60 minutes of reaction, the materials were vented, the temperature was lowered, and the reaction was stopped;

[0125] (iii) The polypropylene product was taken out and vacuum dried at 30° C. for 2 hours, and then the dried polypropylene product was subjected to performance testing. The test results are shown in Table 2.

[0126] Example 8

[0127] The method and conditions for propylene polymerization are the same as those of Example 1, except that the ratio of hydrogenation catalyst to total hydrogen (mol / mol) is 1 / 10000; and the molar ratio of alkyl aluminum to titanocene in the hydrogenation catalyst is 8.

[0128] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 3.

[0129] Example 9

[0130] The method and conditions for propylene polymerization are the same as those of Example 1, except that the ratio of hydrogenation catalyst to total hydrogen (mol / mol) is 1 / 10000; and the molar ratio of alkyl aluminum to titanocene in the hydrogenation catalyst is 10.

[0131] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 3.

[0132] Example 10

[0133] The method and conditions for propylene polymerization were the same as those of Example 1, except that the amount of hydrogenation catalyst was changed, and the ratio of hydrogenation catalyst to total hydrogen (mol / mol) was 1:5000.

[0134] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 3.

[0135] Comparative Example 5

[0136] The method and conditions for the propylene polymerization reaction were the same as those of Example 8, except that the molar ratio of alkyl aluminum to titanocene in the hydrogenation catalyst was 1.5. The mixed solution of this hydrogenation catalyst had obvious precipitation and was not suitable for the second stage polymerization reaction.

[0137] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 3.

[0138] Comparative Example 6

[0139] The method and conditions for the propylene polymerization reaction were the same as those of Example 1, except that the molar ratio of the alkyl aluminum to the titanocene in the hydrogenation catalyst was 4.

[0140] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 3.

[0141] Table 2

[0142]

[0143] Table 3

[0144]

[0145]

[0146] As in the above embodiments, a single reactor is used and the reaction is divided into two stages to simulate the polymerization reaction conditions of a reaction device with a discharge line in industrial production: the first polymerization reaction stage simulates a normal polymerization reaction in a reactor corresponding to industrial production, and the second polymerization reaction stage simulates a polymerization reaction in which a hydrogenation catalyst is introduced into a discharge line arranged at the end of the device in industrial production (i.e., the end of the polymerization reaction).

[0147] As can be seen from Table 1, the amount of hydrogenation catalyst used in Examples 1 and 2 is one thousandth of the total molar amount of hydrogen in the system. Example 1 produces a polypropylene product containing 0.037wt% of ultra-high molecular weight components, whose melt strength is 1.5 times that of the product obtained in Example 1, the bending strength is increased by about 2.6%, and the impact strength is increased by about 3.5%. Example 2 produces a polypropylene product containing 0.058wt% of ultra-high molecular weight components, whose melt strength is 3 times that of the product obtained in Example 2, the tensile strength is increased by 12.1%, the bending strength is increased by 5.5%, and the impact strength is increased by about 80.3%.

[0148] In Example 3 and Example 4, the amount of hydrogenation catalyst used is one ten-thousandth of the total molar amount of hydrogen in the system, which can also improve the performance of the polypropylene product.

[0149] In Comparative Example 3, no hydrogen was added during the polymerization process. Although a final product containing a certain amount of ultra-high molecular weight components was obtained, Mn (logMW ≥ 7) / Mp = 8.3 was too small, and the content of the high molecular weight polypropylene component was too high, which was not conducive to the processing performance of the product.

[0150] From the data in Table 2, it can be seen that compared with Comparative Example 4, the content of ultra-high molecular weight components in the products obtained in Examples 5 to 7 in which propylene and ethylene are copolymerized increases to 0.08%, 0.47% and 1.66%, respectively, and the comprehensive performance of the products is improved. The performance test of the product obtained in Example 6 also shows high melt strength and good mechanical properties.

[0151] As can be seen from the data in Table 3, when the molar ratio of alkyl aluminum to titanocene in the hydrogenation catalyst is 8 or 10, the alkyl aluminum is slightly excessive, and the product melt index is only slightly increased, which can be used to play the role of hydrogenation catalyst; when the molar ratio of alkyl aluminum to titanocene in the hydrogenation catalyst is less than 4, the alkyl aluminum cannot completely dissolve titanocene, and at this time, titanocene cannot effectively play the hydrogenation effect; when the molar ratio of alkyl aluminum to titanocene is 1.5, there is obvious precipitation, which is not suitable for achieving the effect of the present invention. When the molar ratio of hydrogenation catalyst / total hydrogen (mol / mol) is 1 / 5000, the hydrogenation effect is better than when the molar ratio of the two is 1 / 10000, and the obtained polymer product melt index is lower.

[0152] In the products prepared in each embodiment, the average molecular weight Mn (logMW ≥ 7) of the UHMWPP component contained therein is much higher than the peak molecular weight Mp of the obtained product, and the ratio of Mn (logMW ≥ 7) / Mp is higher than 10, or even higher than 30 (see Table 1-3), and the processing performance is good.

[0153] Therefore, the present invention introduces a relatively low content of ultra-high molecular weight components into the propylene polymer product, thereby significantly improving the mechanical properties of the polypropylene product while maintaining good processing performance.

[0154] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the spirit of the present invention.

Claims

1. A propylene polymer directly obtained from a polymerization reaction, characterized in that The propylene polymer comprises an ultra-high molecular weight polypropylene component with a molecular weight MW ≥ 10,000,000; The content of the ultra-high molecular weight polypropylene component is 0.03-5.00wt%, preferably 0.05-2.00wt%; The ratio of the number average molecular weight Mn of the ultra-high molecular weight polypropylene component to the peak molecular weight Mp of the propylene polymer is Mn (MW ≥ 10,000,000) / Mp ≥ 10, preferably ≥ 30.

2. The propylene polymer according to claim 1, characterized in that The melt strength of the propylene polymer is greater than or equal to 2.0 cN; and / or The propylene polymer has a melt flow rate MFR of 0.01 to 10000 g / 10 min, preferably 0.1 to 300 g / 10 min, and more preferably 0.5 to 200 g / 10 min.

3. A method for preparing a propylene polymer directly obtained from a polymerization reaction, characterized in that: Using two or more polymerization stages arranged in sequence; the method comprises the following steps: (i) in the presence of a polymerization catalyst and hydrogen, propylene or propylene and one or more optional comonomers are subjected to a first stage (co)polymerization reaction for 0.1 to 10 hours to prepare a stream containing a polypropylene-I component; (ii) after the first stage (co)polymerization reaction, at least a portion or all of the stream containing the polypropylene-I component is further polymerized in a pipeline located outside the reactor in the presence of a hydrogenation catalyst for 0.01 to 3 hours to obtain an ultra-high molecular weight polypropylene (UHMWPP) component having a molecular weight MW ≥ 10,000,000; Then, the reaction is stopped to obtain the propylene polymer containing an ultra-high molecular weight polypropylene (UHMWPP) component; The molar ratio of the hydrogenation catalyst to the total amount of hydrogen contained in the polymerization system is 1 / 10000-1 / 100, preferably 1 / 10000-1 / 1000.

4. The preparation method according to claim 3, characterized in that: The hydrogenation catalyst is a mixture of a metal organic compound and an alkyl aluminum compound; The general formula of the metal organic compound is R(R')-MX(X'), wherein: R, R' are each independently an unsubstituted or substituted cyclopentadienyl, indenyl, or fluorenyl group, wherein the substituent is preferably selected from methyl, ethyl, propyl, butyl, or cycloalkyl group; M is a transition metal element, preferably one or more selected from Fe, Ti, Zr, Cr and Mn; X, X' are each independently a halogen atom, an alkyl group or an alkoxy group; In the mixture, the molar ratio of aluminum in the alkyl aluminum compound to the metal organic compound is in the range of 5.5-10.0:1, preferably 5.5-8.0:

1.

5. The preparation method according to claim 3, characterized in that: The metal organic compound is selected from one or more of bis(cyclopentadienyl)titanium dichloride, bis(cyclopentadienyl)titanium dibromide, bis(cyclopentadienyl)methoxytitanium chloride, bis(cyclopentadienyl)ethoxytitanium chloride, bis(cyclopentadienyl)phenoxytitanium chloride, bis(cyclopentadienyl)dimethyltitanium, bis(cyclopentadienyl)diethyltitanium, diindenyltitanium dichloride, diindenyltitanium dibromide, diindenyldimethyltitanium, diindenyldiethyltitanium, bis(cyclopentadienyl)zirconium dichloride, bis(cyclopentadienyl)zirconium dibromide, bis(cyclopentadienyl)dimethylzirconium and bis(cyclopentadienyl)diethylzirconium, preferably one or two of bis(cyclopentadienyl)titanium dichloride and bis(cyclopentadienyl)diethyltitanium; and / or The alkyl aluminum compound is selected from one or more of trimethyl aluminum, triethyl aluminum, tributyl aluminum, triisobutyl aluminum, trihexylaluminum, trioctylaluminum, tridecylaluminum, dimethylaluminum monochloride, diethylaluminum monochloride, dibutylaluminum monochloride, diisobutylaluminum monochloride, methylaluminoxane (MAO) and modified methylaluminoxane (MMAO), preferably selected from triethylaluminum and / or methylaluminoxane.

6. The preparation method according to claim 3, characterized in that: The hydrogenation catalyst is a mixture of Cp2TiCl2 and an alkyl aluminum compound; wherein the molar ratio of aluminum in the alkyl aluminum compound to Cp2TiCl2 is in the range of 5.5-10.0:1, preferably 5.5-8.0:

1.

7. The preparation method according to claim 3, characterized in that: The polymerization reaction time of step (i) is 0.2-5 hours, preferably 0.3-3 hours; and / or The polymerization reaction temperature of step (i) is 40-250°C, preferably 50-200°C.

8. The preparation method according to claim 3, characterized in that: In step (ii), the length of the pipeline outside the reactor is 0.1 to 50 meters.

9. The preparation method according to claim 3, characterized in that: In step (ii), a discharge pipeline is arranged outside a single reactor or outside the end of multiple reactors connected in series, and the hydrogenation catalyst is added into the discharge pipeline to continue the polymerization reaction.

10. The preparation method according to claim 3, characterized in that: The polymerization reaction time of step (ii) is 0.08-2 hours, preferably 0.1-1.5 hours; and / or The polymerization reaction temperature of step (ii) is 0-250°C, preferably 20-200°C.

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