Propylene polymer containing ultra-high molecular weight component and preparation method thereof

Abstract

The invention belongs to the technical field of propylene polymerization, and particularly relates to a propylene polymer containing ultra-high molecular weight components and a preparation method thereof. The method comprises the following steps: (i) in the presence of a polymerization catalyst and hydrogen, propylene or propylene and a comonomer are subjected to a first-stage (co) polymerization reaction for 0.1-10 hours to prepare a material flow containing a polypropylene-I component; (ii) after the first polymerization reaction is finished, reducing the amount of hydrogen to 20 wt% or below of the initial amount through separation treatment and / or replacement treatment; then a hydrogenation catalyst is introduced, and polymerization reaction is continued for 0.01-3 hours; stopping the reaction to obtain the propylene polymer containing the ultra-high molecular weight polypropylene component; the molar ratio of the hydrogenation catalyst to the residual hydrogen is 1 / 10000 to 1 / 100. According to the prepared polypropylene containing the ultra-high molecular weight component, the melt strength is remarkably improved, and meanwhile, the mechanical property, the processability and the like of the polypropylene are obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of propylene polymerization, and in particular relates to a propylene polymer containing an ultra-high molecular weight component and a preparation method thereof. Background Art

[0002] 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 to 400,000).

[0003] The performance of polypropylene is directly related to its molecular weight, molecular weight distribution width, molecular chain stereoregularity, type and content of comonomers, etc. 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 and 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 be rapidly reduced.

[0004] In view of this, some improvement studies have been conducted in this field.

[0005] Patent document CA1241196A discloses that in the first stage of polymerization, propylene is polymerized in the absence of hydrogen to prepare a high molecular weight polypropylene with an intrinsic viscosity [η] of 8 to 13 dl / g, and the high molecular weight polypropylene accounts for 15 to 50 wt% of the total amount of the final polypropylene resin composition; then, in the second stage, two or more polymerization reactors are used to polymerize propylene to prepare a low molecular weight polypropylene with an intrinsic viscosity [η] of less than 8 dl / g, and the melt flow rate (MFR) of the final polypropylene resin composition is 0.01 to 5 g / 10 min, and the load ratio of the two reactors is 85:15 to 50:50. The obtained polypropylene composition has high melt strength and can be used for blow molding, vacuum molding, calendaring molding, foaming or extrusion molding, etc.

[0006] 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.

[0007] However, both asymmetric hydrogenation and the method of adding an external electron donor have 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. 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.

[0008] Patent document US10544237B2 proposes a method suitable for the production of polypropylene containing different molecular weight components in series by two or more slurry liquid phase polymerization reactors; wherein the first reactor normally adds hydrogen to produce a low molecular weight polypropylene component, and all or part of the streams discharged from the first reactor directly contact a hydrogenation catalyst to remove all or part of the hydrogen to form a stream with a low hydrogen concentration, and directly enter the second and above reactors or return to the first reactor to undergo polymerization without undergoing a low-pressure gas-liquid flash process, thereby producing a high molecular weight polypropylene component, thereby manufacturing a propylene homopolymer or copolymer with a bimodal distribution characteristic. This type of method is suitable for slurry liquid phase propylene polymerization process, and does not undergo a low-pressure gas-liquid flash separation process. Due to the high hydrogen concentration in the discharge material of the first reactor, a large amount of propylene is converted into propane through the action of a hydrogenation catalyst, which affects the production load of the downstream reactor and the subsequent gas separation process.

[0009] 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. The use of a hydrogenation catalyst is not mentioned.

[0010] The above-mentioned methods for producing high melt strength polypropylene by direct polymerization in various reactors all have various problems. Without changing the external electron donor and only asymmetrically adjusting hydrogen, the amount of hydrogen used is too large, the adjustment range is limited, the reactor is stuck at the edge, the operation risk is high, the molecular weight distribution of the obtained polypropylene is not wide enough, and the processing performance is poor; at the same time, asymmetrically adjusting the external electron donor and hydrogen, there is a large amount of external electron donor, complex operation of the two reactors, difficulty in load adjustment, the proportion of high molecular weight components is higher than 30wt%, the distribution width is not enough, and the product processing performance is poor. In the method of using a hydrogenation catalyst to produce a high molecular weight component, due to the high hydrogen concentration in the material stream, the amount of hydrogenation catalyst used is large, resulting in a large amount of propylene converted into propane, causing waste, and affecting the reactor production load and subsequent gas separation process, reducing production efficiency.

[0011] The above methods have a common defect that the content of the generated high molecular weight component is relatively high, generally above 15 wt %. If the content of the high molecular weight polymer component is too high, the processability of the obtained polypropylene material will be affected.

[0012] In view of this, continuing to explore the process and method of preparing polypropylene with excellent performance by direct polymerization has become a topic worthy of research. Summary of the invention

[0013] In view of some problems existing in the prior art for preparing polypropylene, the purpose of the present invention is to provide a propylene polymer containing an ultra-high molecular weight component and a preparation method thereof; the polypropylene containing an ultra-high molecular weight component is prepared by further reacting the material obtained by the first polymerization reaction in the presence of a hydrogenation catalyst after replacement or separation, and the obtained propylene polymer product has significantly improved melt strength, tensile strength, impact strength, bending modulus and processing performance; the preparation method can produce many series of new high-performance polypropylene products, and the mechanical properties of the obtained products are significantly improved, and the cost is significantly reduced.

[0014] In order to achieve the above object, the present invention provides the following technical solutions:

[0015] In a first aspect, a propylene polymer containing an ultra-high molecular weight component is provided, wherein the propylene polymer contains an ultra-high molecular weight polypropylene (UHMWPP) component, and the molecular weight of the ultra-high molecular weight polypropylene (UHMWPP) component is MW ≥ 10,000,000;

[0016] In the propylene polymer, the content of the ultra-high molecular weight polypropylene (UHMWPP) component is 0.03-10.0wt% (for example, 0.05wt%, 0.08wt%, 0.10wt%, 0.12wt%, 0.15wt%, 0.20wt%, 0.40wt%, 0.50wt%, 0.80wt%, 1.00wt%, 1.20wt%, 1.50wt%, 2.00wt%, 2.50wt%, 4.00wt%, 6.00wt%, 8.00wt%), preferably 0.20-5.0wt%;

[0017] The ratio of the number average molecular weight Mn of the ultrahigh molecular weight polypropylene (UHMWPP) component to the peak molecular weight Mp of the propylene polymer is Mn (MW ≥ 10,000,000) / Mp ≥ 10, for example, 12, 15, 20, 40, 50, 60, 80, 100, preferably ≥ 20.

[0018] According to the propylene polymer provided by the present invention, in some embodiments, the melt strength of the propylene polymer is ≥2.0 cN (for example, 3.0 cN, 5.0 cN, 8.0 cN, 10 cN, 15 cN), preferably ≥3.0 cN.

[0019] In some embodiments, the melt flow rate (MFR) of the propylene polymer is from 0.01 g / 10 min to 10000 g / 10 min (e.g., 0.05 g / 10 min, 0.2 g / 10 min, 0.4 g / 10 min, 0.5 g / 10 min, 1.0 g / 10 min, 5.0 g / 10 min, 10 g / 10 min, 50 g / 10 min, 100 g / 10 min, 150 g / 10 min, 350 g / 10 min, 500 g / 10 min, 1000 g / 10 min, 5000 g / 10 min), preferably from 0.1 g / 10 min to 300 g / 10 min, and more preferably from 0.1 g / 10 min to 200 g / 10 min.

[0020] In a second aspect, there is provided a method for preparing a propylene polymer containing an ultrahigh molecular weight component, using two or more polymerization reaction stages arranged in sequence; the method comprising the steps of:

[0021] (i) in the presence of a polymerization catalyst and hydrogen, propylene or propylene and one or more comonomers are subjected to a first stage (co)polymerization reaction in a reactor for 0.1 to 10 hours (e.g., 0.5 hours, 1 hour, 2 hours, 5 hours, 8 hours) to prepare a stream containing a polypropylene-I component;

[0022] (ii) after the first polymerization reaction, the amount of hydrogen in the system is reduced to 20 wt% or less (e.g., 18 wt%, 15 wt%, 12 wt%, 10 wt%, 5 wt%, 2 wt%) of its initial amount by separation treatment and / or replacement treatment; then a hydrogenation catalyst is introduced into the system, and the polymerization reaction is continued for 0.01-3 hours (e.g., 0.05 hours, 0.1 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;

[0023] Then, the reaction is stopped to obtain the propylene polymer containing an ultra-high molecular weight polypropylene (UHMWPP) component;

[0024] The molar ratio of the hydrogenation catalyst to the residual hydrogen in the system is 1 / 10000 to 1 / 100 (e.g., 1 / 10000, 1 / 8000, 1 / 5000, 1 / 1000, 1 / 500, 1 / 400, 1 / 200), preferably 1 / 10000 to 1 / 1000.

[0025] 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, or a mixture of any two or more of these comonomers.

[0026] 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:

[0027] (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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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:

[0032] 0≤n≤2,

[0033] 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.

[0034] 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.

[0035] In some embodiments, the hydrogenation catalyst is a mixture of a metal organic compound and an alkyl aluminum compound.

[0036] In some embodiments, the metal organic compound has a general formula of R(R')-MX(X'), wherein:

[0037] 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;

[0038] M is a transition metal element, preferably one or more selected from Fe, Ti, Zr, Cr and Mn;

[0039] X, X' are each independently a halogen atom, an alkyl group or an alkoxy group;

[0040] 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, 6.5:1, 7.0:1, 7.5:1, 8.0:1, 8.5:1, 9.0:1, 9.5:1), preferably 5.5 to 8.0:1.

[0041] 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.

[0042] 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.

[0043] 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, 6.5:1, 7.0:1, 7.5:1, 8.0:1, 8.5:1, 9.0:1, 9.5:1), preferably 5.5-8.0:1.

[0044] The two or more polymerization reaction stages arranged in sequence in the present invention can be carried out in a first reactor and a second reactor arranged in sequence by connecting two or more gas phase reactors in series, or by connecting a liquid phase stirred tank / slurry loop reactor and a gas phase reactor in series. For the two polymerization reaction stages, the polymerization reaction can be carried out in a first reactor and a second reactor arranged in sequence.

[0045] In the first reactor, a normal propylene polymerization reaction can be carried out using a combination of a Ziegler-Natta catalyst and different external electron donors, or a metallocene catalyst. An efficient "gas lock" displacement separation device or a flash separation device can be provided between the first reactor and the second reactor, which can reduce the amount of hydrogen in the reaction system to 20wt% or less of its initial amount.

[0046] After the discharge material discharged from the first reactor is separated by replacement or flash separation, the content of unreacted monomer and chain transfer agent (hydrogen) in the system is greatly reduced; on this basis, an appropriate amount of hydrogenation catalyst is added (to further remove residual hydrogen in the feed stream), and the propylene monomer can continue to polymerize under conditions close to no hydrogen or very little hydrogen to generate an ultra-high molecular weight polypropylene component.

[0047] The timing of adding the hydrogenation catalyst is, for example, directly adding the hydrogenation catalyst at the terminal outlet of the first reactor after efficient separation by an air lock device or flash distillation and then entering the second and subsequent reactors for polymerization reaction, or adding the hydrogenation catalyst at the inlet of the second reactor (or at the outlet of the second and subsequent reactors for a system with multiple reactors) after efficient separation by an air lock device or flash distillation and then carrying out polymerization reaction. In this way, in the stream containing the polypropylene-I component obtained after the first polymerization stage, the propylene monomer continues to undergo polymerization reaction under nearly hydrogen-free conditions, and the polypropylene finally obtained is a propylene polymer product containing a high molecular weight polypropylene component.

[0048] In some embodiments, the polymerization reaction time of step (i) is 0.2-5 hours (eg, 0.5 hours, 1.0 hours, 1.5 hours, 1.8 hours), preferably 0.3-2 hours.

[0049] In some embodiments, the polymerization reaction temperature of step (i) is 40-250°C (eg, 45°C, 60°C, 80°C, 100°C, 150°C, 180°C, 220°C), preferably 50-200°C.

[0050] In some embodiments, in step (ii), the amount of hydrogen in the system is reduced to 20 wt% or less of its initial amount (e.g., 15 wt%, 12 wt%, 10 wt%, 8 wt%, 5 wt%, 2 wt%), preferably 10 wt% or less.

[0051] In some embodiments, the polymerization reaction time of step (ii) is 0.08-2 hours (e.g., 0.15 hours, 0.3 hours, 0.5 hours, 1.0 hours, 1.8 hours), preferably 0.1-1.5 hours;

[0052] In some embodiments, the polymerization reaction temperature of step (ii) is 0-250°C (eg, 10°C, 30°C, 50°C, 80°C, 100°C, 150°C, 180°C, 220°C), preferably 20-200°C.

[0053] The propylene polymer prepared according to the preparation method of the present invention has a melt flow rate (MFR) of 0.01 g / 10min to 10000 g / 10min, for example, 0.1 g / 10min, 0.4 g / 10min, 1.0 g / 10min, 5.0 g / 10min, 10 g / 10min, 50 g / 10min, 100 g / 10min, 150 g / 10min, 350 g / 10min, 500 g / 10min, 1000 g / 10min, 5000 g / 10min, preferably 0.1 g / 10min to 300 g / 10min, more preferably 0.1 g / 10min to 200 g / 10min.

[0054] The propylene polymer prepared according to the preparation method of the present invention has a melt strength of ≥2.0 cN (e.g., 3.0 cN, 5.0 cN, 8.0 cN, 10 cN, 15 cN), preferably ≥3.0 cN, for example, 3.0 cN to 10.0 cN.

[0055] According to the preparation method of the present invention, in the propylene polymer, the molecular weight MW of the ultra-high molecular weight polypropylene (UHMWPP) component is ≥10,000,000, for example, 1,000,000,000≥molecular weight MW≥10,000,000.

[0056] In the propylene polymer, the content of the ultra-high molecular weight polypropylene (UHMWPP) component is 0.03-10.0wt% (for example, 0.05wt%, 0.08wt%, 0.10wt%, 0.12wt%, 0.15wt%, 0.20wt%, 0.40wt%, 0.50wt%, 0.80wt%, 1.00wt%, 1.20wt%, 1.50wt%, 2.00wt%, 2.50wt%, 4.00wt%, 8.00wt%), preferably 0.20-5.00wt%.

[0057] The ratio of the number average molecular weight Mn of the ultrahigh molecular weight polypropylene (UHMWPP) component to the peak molecular weight Mp of the propylene polymer is Mn(MW≥10,000,000) / Mp≥10, for example, 12, 15, 20, 30, 40, 50, 60, 80, 100, preferably ≥20.

[0058] The present invention is applicable to propylene gas phase polymerization, slurry polymerization, solution polymerization or various combined polymerization processes, and is particularly applicable to polymerization processes in which there are gas lock device displacement separation or flash separation steps between each reactor. For example, in two or more propylene gas phase polymerization series reactors, the first reactor can use Ziegler-Natta catalyst or metallocene catalyst to carry out propylene polymerization under normal hydrogen concentration, and then the material obtained in the first reactor is discharged from the first reactor, and after one or more efficient displacement separation or gas-liquid-solid flash separation by the gas lock device, 80wt% or more of hydrogen and unreacted monomers can be removed, and then enter the second reactor; at the same time, a small amount of hydrogenation catalyst is injected into the second and above reactors to remove a small amount of hydrogen remaining in the powder; in this way, a polymerization reaction occurs under nearly hydrogen-free conditions in the second and above reactors to generate an ultra-high molecular weight polypropylene (UHMWPP) component, and finally a propylene polymer product with a controllable content of the ultra-high molecular weight polypropylene (UHMWPP) component can be obtained.

[0059] The present invention does not require the use of complex matching of different external electron donors, does not require the use of a large amount of hydrogen, and does not require the use of a large amount of hydrogenation catalyst, and can cleverly overcome the technical barriers of the prior art to prepare a polypropylene product with an ultra-high molecular weight component in a suitable content range, and its comprehensive performance is improved.

[0060] Compared with the prior art, the excellent effects of the technical solution of the present invention are at least:

[0061] In the present invention, since an air lock device or a flash device is arranged after the first polymerization reaction stage, the residual hydrogen in the material discharged from the first reactor is small, and then a hydrogenation catalyst is added to the discharged material, so that the amount of propylene converted into propane can be controlled at a very low level, and the loss of monomer raw materials is small; and the adding position of the hydrogenation catalyst is flexible, the reactor load adjustment range is large, and the content of the required ultra-high molecular weight polypropylene component can be controlled in proportion without affecting the normal operation of the device;

[0062] After separation and replacement, the material coming out of the first reactor (which includes the relatively low molecular weight polypropylene powder generated in the first reactor, monomer propylene, hydrogen, polymerization catalyst, alkyl aluminum, optional external electron donor, a small amount of inert components, etc.) will usually drop in temperature by 5 to 10°C. At this time, adding a hydrogenation catalyst to the material before it enters the subsequent reaction device can further remove the residual hydrogen, and the material will continue to undergo polymerization reaction at a temperature 5 to 10°C lower than that of the subsequent reaction device; the lower the polymerization temperature, the higher the molecular weight of the generated polypropylene component; therefore, the presence of the separation or replacement device, in addition to reducing the hydrogen content, also helps the material coming out of the first reactor to continue to react for a period of time at a relatively lower temperature, which helps to generate a higher molecular weight of the ultra-high molecular weight polypropylene component in the final propylene polymer product;

[0063] By adjusting the residence time of the material in the presence of the hydrogenation catalyst, the content of the ultra-high molecular weight component (such as controlled at 0.03-10.0 wt%), the content of the comonomer, the melt index and the molecular weight distribution of the product can be flexibly controlled; and by adjusting the dosage of the hydrogenation catalyst, the molecular weight of the ultra-high molecular weight polypropylene component can be controlled to reach a molecular weight MW of 10,000,000 or above, thereby preparing a series of high melt strength polypropylenes containing ultra-high molecular weight polypropylene components and different compositions, while maintaining good processing performance, significantly improving the performance of polypropylene products (including melt strength, tensile strength, impact strength, flexural modulus, etc.).

[0064] The amount of alkyl aluminum in the hydrogenation catalyst is controlled within a suitable range, which can reduce the effect of alkyl aluminum as a chain transfer agent on the molecular weight of the ultra-high molecular weight component while achieving the hydrogenation effect; the amount of the hydrogenation catalyst is also controlled within a suitable range, reducing the catalyst residue in the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 A comparison chart of the GPC test results of the products obtained in Example 1 and Comparative Example 1 is shown;

[0066] Figure 2 A comparison chart of the GPC test results of the products obtained in Example 3 and Comparative Example 2 is shown;

[0067] Figure 3 A comparison chart of the GPC test results of the products obtained in Example 4 and Comparative Example 3 is shown. DETAILED DESCRIPTION

[0068] 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.

[0069] <Source of raw materials>

[0070] 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 catalyst A was 3.0wt%. The catalyst B used was prepared according to Example 3 described in patent application CN101054424A, and the Ti content in catalyst B was 2.4wt%.

[0071] 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.

[0072] In each embodiment and comparative example, the relevant data of the obtained polymer product are obtained according to the following test methods:

[0073] (1) Melt flow rate (MFR): The sample to be tested was tested according to ASTM D1238;

[0074] (2) Xylene soluble content XS, wt%: The samples were tested using a fully automatic xylene soluble content tester (CRYSTEX QC) from Polymer Char Company;

[0075] (3) Molecular weight and its distribution: The samples were tested using a high temperature gel permeation chromatograph (GPC-IR6) from Polymer Char.

[0076] (4) Melt strength: The samples were tested using a RH7-2 capillary rheometer + balance from Malvern Instruments.

[0077] (5) Mechanical properties

[0078] Tensile strength: tested in accordance with GB / T 1040.2-2006;

[0079] Flexural modulus: tested in accordance with GB / T 9341-2008;

[0080] Impact test: Tested in accordance with GB / T 1843-2008.

[0081] Example 1

[0082] The propylene polymerization reaction was carried out in a 5L stainless steel polymerization kettle, and the specific steps were as follows:

[0083] (i) First, the reactor was purged with purified nitrogen (water <1 ppm, oxygen <1 ppm); then, 2.2 L of liquid propylene and 0.12 mol of hydrogen were added in sequence at room temperature, and the system was heated to 70° C.;

[0084] Before the temperature of the reactor reaches 70° C., 2.0 ml of 0.5 M triethylaluminum 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 the first polymerization reaction stage;

[0085] (ii) After 60 minutes of reaction, the gas in the reactor was vented; after the gas in the reactor was vented, 0.012 mol of hydrogen and 1.5 L of liquid propylene were added to the reactor, and when the system was heated to 70° C., 0.24 ml (0.0012 mmol) of a hexane solution of a prepared titanocene hydrogenation catalyst (wherein the molar ratio of titanocene dichloride to triethylaluminum was 1 / 6) was added from the catalyst feed pipe and the reaction was continued at 70° C. for 5 minutes;

[0086] That is, by venting the gas in the reactor and then re-adding a certain ratio of propylene and hydrogen to simulate: in a system with two reactors in series, the amount of hydrogen is reduced to 10wt% of its initial amount, and the materials can continue to react in the second reactor at 70°C in the presence of a hydrogenation catalyst for 5 minutes;

[0087] Then, discharge the materials, cool down, and stop the reaction;

[0088] (iii) The polypropylene product obtained in the reactor 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.

[0089] Example 2

[0090] The method and conditions for the propylene polymerization reaction were the same as those of Example 1, except that the polymerization time of introducing a hexane solution of the titanocene hydrogenation catalyst and continuing the reaction at 70° C. in step (ii) was changed to 30 minutes.

[0091] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 1.

[0092] Example 3

[0093] The method and conditions for the propylene polymerization reaction were the same as those of Example 1, except that the polymerization time of introducing a hexane solution of the titanocene hydrogenation catalyst and continuing the reaction at 70° C. in step (ii) was changed to 60 minutes.

[0094] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 1.

[0095] Comparative Example 1

[0096] The propylene polymerization reaction was carried out in a 5L stainless steel polymerization kettle, and the specific steps were as follows:

[0097] (i) First, the reactor was purged with purified nitrogen (water <1 ppm, oxygen <1 ppm); then, 2.2 L of liquid propylene and 0.12 mol of hydrogen were added in sequence at room temperature, and the system was heated to 70° C.;

[0098] 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. 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 the first polymerization reaction stage;

[0099] (ii) After 60 minutes of reaction, the gas in the reactor was vented; after the gas in the reactor was completely vented, 0.012 mol of hydrogen and 1.5 L of liquid propylene were added to the reactor, and when the system was heated to 70° C., the reaction was continued for 5 minutes;

[0100] That is, the reaction was simulated by venting the gas in the reactor and then refilling propylene and hydrogen in a certain ratio: in a system with two reactors in series, the amount of hydrogen was reduced to 10 wt% of its initial amount, and the materials continued to react at 70° C. for 5 minutes in the second reactor;

[0101] Then, discharge the materials, cool down, and stop the reaction;

[0102] (iii) The polypropylene product obtained in the reactor 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.

[0103] Comparative Example 2

[0104] The method and conditions for the propylene polymerization reaction are the same as those of Comparative Example 1, except that 0.012 mol of hydrogen and 1.5 L of liquid propylene are added in step (ii), and when the system is heated to 70°C, the polymerization time for the continued reaction is changed to 60 minutes.

[0105] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 1.

[0106] Example 4

[0107] The propylene polymerization reaction was carried out in a 5L stainless steel polymerization kettle, and the specific steps were as follows:

[0108] (i) First, the reactor was purged with purified nitrogen (water <1 ppm, oxygen <1 ppm); then, 2.2 L of liquid propylene and 0.048 mol of hydrogen were added in sequence at room temperature, and then the system was heated to 70° C.;

[0109] 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 TEOS hexane solution and 8.1 mg of catalyst B 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 the first polymerization reaction stage;

[0110] (ii) After 60 minutes of reaction, the gas in the reactor was vented; after the gas in the reactor was vented, 0.0048 mol of hydrogen and 1.5 L of liquid propylene were added to the reactor, and when the system was heated to 70° C., 0.1 ml (0.00048 mmol) of a hexane solution of a prepared titanocene hydrogenation catalyst (wherein the molar ratio of titanocene dichloride to triethylaluminum was 1 / 6 mol / mol) was added from the catalyst feed pipe and the reaction was continued at 70° C. for 60 minutes;

[0111] That is, by venting the gas in the reactor and then re-adding a certain ratio of propylene and hydrogen to simulate: in a system with two reactors in series, the amount of hydrogen is reduced to 10wt% of its initial amount, and the materials can continue to react in the second reactor at 70°C in the presence of a hydrogenation catalyst for 60 minutes;

[0112] Then, discharge the materials, cool down, and stop the reaction;

[0113] (iii) The polypropylene product obtained in the reactor 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.

[0114] Comparative Example 3

[0115] The propylene polymerization reaction was carried out in a 5L stainless steel polymerization reactor, and the specific steps were as follows:

[0116] (i) First, the reactor was purged with purified nitrogen (water <1 ppm, oxygen <1 ppm); then, 2.2 L of liquid propylene and 0.048 mol of hydrogen were added in sequence at room temperature, and the system was heated to 70° C.;

[0117] 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 TEOS hexane solution and 8.1 mg of catalyst B 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 the first polymerization reaction stage;

[0118] (ii) After the reaction time is 60 minutes, the gas in the reactor is vented; after the gas in the reactor is completely vented, 0.0048 mol of hydrogen and 1.5 L of liquid propylene are added to the reactor, and when the system is heated to 70° C., the reaction is continued for 60 minutes;

[0119] That is, the reaction was simulated by venting the gas in the reactor and then re-adding a certain ratio of propylene and hydrogen: the amount of hydrogen in the system of two reactors in series was reduced to 10wt% of its initial amount, and the materials continued to react at 70°C for 60 minutes in the second reactor;

[0120] Then, discharge the materials, cool down, and stop the reaction;

[0121] (iii) The polypropylene product obtained in the reactor 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.

[0122] Table 1

[0123]

[0124]

[0125] In Comparative Example 1-3, after the polymerization reaction was carried out for 60 minutes (first polymerization stage), the reaction atmosphere was replaced, and the polymerization reaction was continued under the condition that the amount of hydrogen was 10wt% of its initial amount (second polymerization stage). In Example 1-4, after the polymerization reaction was carried out for 60 minutes (first polymerization stage), the reaction atmosphere was replaced, and the polymerization reaction was continued under the condition that the amount of hydrogen was 10% of its initial amount and a titanocene hydrogenation catalyst was used (second polymerization stage).

[0126] From the data in Table 1, it can be seen that in Comparative Examples 1-3, even in the second stage polymerization process after 90% of the hydrogen in the system was removed, the content of high molecular weight components in the obtained polypropylene product was extremely low or basically absent. However, after using a very small amount of hydrogenation catalyst, a certain amount of ultra-high molecular weight polypropylene (UHMWPP) component was obviously generated in the second stage polymerization process; and as the polymerization time of the second stage of polymerization was extended, the content of the UHMWPP component increased. The increase in the content of the UHMWPP component can be observed from the GPC test (such as Figure 1-3 As shown). Compared with the comparative example, the melt strength of the polypropylene product obtained in each embodiment is 2 to 10 times that of the comparative example, the tensile strength is increased by about 5 to 15%, the flexural modulus is increased by about 8 to 20%, and the impact strength is increased by about 10 to 30%. More importantly, after the ultra-high molecular weight component that significantly improves the performance of polypropylene is introduced in this way by the present invention, the melt index of the product is not greatly changed, and the processability of the material is not affected.

[0127] Figure 1-3 A comparison chart of the GPC test results of the products obtained from Example 1 and Comparative Example 1, Example 3 and Comparative Example 2, and Example 4 and Comparative Example 3 is shown; it can be seen from the accompanying figure that with the increase of the second stage polymerization time, the GPC curve shifts to the right, indicating an increase in molecular weight; in the second stage polymerization, the introduction of the hydrogenation catalyst leads to the generation of a certain content of ultra-high molecular weight components.

[0128] Embodiment 5:

[0129] The method and conditions for the propylene polymerization reaction are the same as those of Example 1, except that the molar ratio of the alkyl aluminum to the titanocene in the hydrogenation catalyst is 8.

[0130] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 2.

[0131] Embodiment 6:

[0132] 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 10.

[0133] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 2.

[0134] Embodiment 7:

[0135] The method and conditions for propylene polymerization were the same as those of Example 1, except that the amount of hydrogenation catalyst added was changed, and the molar ratio of hydrogenation catalyst / hydrogen added after venting (mol / mol) was 1:5000.

[0136] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 2.

[0137] Comparative Example 4:

[0138] The method and conditions for the propylene polymerization reaction were similar to those of Example 1, 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.

[0139] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 2.

[0140] Comparative Example 5:

[0141] 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.

[0142] The dried polypropylene product was subjected to performance tests. The test results are shown in Table 2.

[0143] Table 2

[0144]

[0145]

[0146] As can be seen from the data in Table 2, 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 increases slightly, 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 now 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 / addition of hydrogen (mol / mol) after venting is 1 / 5000, the hydrogenation effect is better than 1 / 10000, and the obtained polymer product melt index is lower.

[0147] In the polypropylene products obtained in each embodiment, the average molecular weight Mn (logMW ≥ 7) of the generated UHMWPP 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 (see Tables 1 & 2).

[0148] 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.

[0149] 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 containing an ultra-high molecular weight component, characterized in that The propylene polymer contains an ultra-high molecular weight polypropylene (UHMWPP) component, and the molecular weight MW of the ultra-high molecular weight polypropylene (UHMWPP) component is ≥10,000,000; In the propylene polymer, the content of the ultra-high molecular weight polypropylene (UHMWPP) component is 0.03-10.0wt%, preferably 0.20-5.0wt%; The ratio of the number average molecular weight Mn of the ultra-high molecular weight polypropylene (UHMWPP) component to the peak molecular weight Mp of the propylene polymer is Mn (MW ≥ 10,000,000) / Mp ≥ 10, preferably ≥ 20.

2. The propylene polymer according to claim 1, characterized in that The melt strength of the propylene polymer is ≥2.0 cN, preferably ≥3.0 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 0.1 to 200 g / 10 min.

3. A method for preparing a propylene polymer containing an ultra-high molecular weight component, 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 comonomers are subjected to a first stage (co)polymerization reaction in a reactor for 0.1 to 10 hours to prepare a stream containing a polypropylene-I component; (ii) after the first polymerization reaction, reducing the amount of hydrogen in the system to 20 wt% or less of its initial amount by separation treatment and / or replacement treatment; then introducing a hydrogenation catalyst into the system, and continuing the polymerization reaction for 0.01-3 hours to obtain an ultra-high molecular weight polypropylene (UHMWPP) component with 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 residual hydrogen in the system is 1 / 10000 to 1 / 100, preferably 1 / 10000 to 1 / 1000.

4. The method according to claim 1, 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 method according to claim 4, 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 method according to claim 1, 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 method according to claim 1, characterized in that The polymerization reaction time of step (i) is 0.2-5 hours, preferably 0.3-2 hours.

8. The method according to any one of claims 1 to 7, characterized in that The polymerization temperature of step (i) is 40-250°C, preferably 50-200°C; and / or The polymerization reaction temperature of step (ii) is 0-250°C, preferably 20-200°C.

9. The method according to any one of claims 1 to 8, characterized in that In step (ii), the amount of hydrogen in the system is reduced to 20 wt% or less, preferably 10 wt% or less, of its initial amount.

10. The method according to any one of claims 1 to 9, characterized in that The polymerization reaction time of step (ii) is 0.08-2 hours, preferably 0.1-1.5 hours.

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