Catalyst system, preparation method for ultra-high molecular weight polyethylene, and use of catalyst system

Abstract

The present invention relates to the technical field of olefin polymerization. Disclosed are a catalyst system, a preparation method for ultra-high molecular weight polyethylene , and a use of the catalyst system. The catalyst system comprises a solid catalyst component and an organoaluminum compound; the solid catalyst component comprises titanium, magnesium, an alkoxy compound, phosphorus, and halogen, and the organoaluminum compound comprises organoaluminum I and organoaluminum II, wherein the solid catalyst component does not comprise a silicon dioxide support; the organoaluminum I has a general formula of AlR1R2R3, and in the general formula, R1, R2, and R3 are identical or different and are each independently a C6-C20 hydrocarbyl group; and the organoaluminum II has a general formula of AlR'1R'2R'3, and in the general formula, R'1, R'2, and R'3 are identical to or different from each other and are each independently a C1-C5 hydrocarbyl group. Compared with catalyst systems commonly used in industry, the catalyst system can reduce the influence of temperature on the molecular weight of the produced ultra-high molecular weight polyethylene and / or maintain the polymerization activity of the catalyst system for a long time.

Description

Catalyst system, method of making and use of ultra-high molecular weight polyethylene TECHNICAL FIELD

[0001] The present invention belongs to the field of olefin polymerization catalysts, and in particular to a catalyst system for preparing polyethylene, a method of making ultra-high molecular weight polyethylene using the same and its use for preparing polyethylene. BACKGROUND

[0002] Ultra-high molecular weight polyethylene (UHMWPE) refers to a linear structure thermoplastic engineering plastic with a relative molecular mass of 1.5 million or more, which has many excellent properties such as high strength, high modulus, low temperature resistance, wear resistance, chemical corrosion resistance, anti-adhesion, self-lubrication and excellent insulation, etc. that other engineering plastics cannot match, and can be applied in the fields of textile, papermaking, packaging, chemical industry, military industry, medical treatment and aerospace, etc.

[0003] Ultra-high molecular weight polyethylene is particularly suitable for producing parts that require high physical properties, such as transmission gears, artificial joint parts, etc. In addition, it can also be used to produce high-strength fibers due to its high strength modulus and high tensile strength. Ultra-high molecular weight polyethylene products are increasingly attracting people's attention and attention, and among them, ultra-high molecular weight polyethylene resins with relatively large molecular mass are widely demanded due to their higher strength, higher modulus and more excellent wear resistance.

[0004] Currently, ultra-high molecular weight polyethylene is mainly produced by ethylene polymerization reaction using a Ziegler-Natta catalyst system, and therefore the performance of the polymerization product mainly depends on the type and structure of the catalyst. The Ziegler-Natta catalyst system comprises two parts of a solid catalyst and a cocatalyst, wherein the solid catalyst mostly adopts a catalyst component with magnesium, titanium and halogen as basic components, and the cocatalyst is generally selected from triethylaluminum.

[0005] With the progress of the synthesis technology of ultra-high molecular weight polyethylene, the synthesis process tends to be specialized. For example, in order to improve the wear resistance or the characteristics of higher strength and modulus of the material, an ultra-high molecular weight polyethylene resin with a larger molecular weight is required. It is known that the molecular weight of polyethylene decreases with the increase of the polymerization temperature. Therefore, in the industrial production of ultra-high molecular weight polyethylene using a Ziegler-Natta catalyst, the temperature is generally controlled at 50-70℃. A lower polymerization temperature can result in a polymer with a higher molecular weight, but at the same time, the polymerization activity is reduced. Under the current industrial production conditions, the polymer product with a higher molecular weight is generally prepared at a lower polymerization temperature. However, for industrial production, since the polymerization of ethylene is highly exothermic, it is difficult to maintain a low polymerization temperature in the industrial production of ultra-high molecular weight polyethylene. The heat removal capacity of the reactor is high, which requires high cost investment and high energy consumption, is not conducive to the rational use of resources, and cannot meet the requirements of green enterprises. In the industrial production of ultra-high molecular weight polyethylene, it would be advantageous to provide a catalyst system and a method for producing ultra-high molecular weight polyethylene at a high temperature (70-90℃), reducing the effect of temperature on the molecular weight of the produced ultra-high molecular weight polyethylene and / or maintaining the polymerization activity of the catalyst system for a long time. Reducing the effect of temperature on the molecular weight of the polymer product can make the molecular weight of the polyethylene polymer more stable, which is conducive to improving the quality of the ultra-high molecular weight polyethylene product.

[0006] The present application provides a catalyst system and a polymerization method, which can reduce the effect of temperature on the molecular weight of the produced ultra-high molecular weight polyethylene and / or maintain the polymerization activity of the catalyst system for a long time.

[0007] SUMMARY

[0008] The object of the present application is to provide a catalyst system for preparing polyethylene, in particular ultra-high molecular weight polyethylene, a method for preparing polyethylene, in particular ultra-high molecular weight polyethylene, using the same, and the use thereof in the polymerization of ethylene. The catalyst system of the present application, when used to catalyze the polymerization of ethylene to produce polyethylene, in particular ultra-high molecular weight polyethylene, at a high temperature (70-90℃), can reduce the effect of temperature changes on the molecular weight of the ultra-high molecular weight polyethylene and / or maintain the polymerization activity of the catalyst system for a long time, compared with the commonly used catalyst system in industry.

[0009] In a first aspect of the present application, a catalyst system is provided, which comprises a solid catalyst component and an organoaluminum compound; the solid catalyst component comprises titanium element, magnesium element, alkoxy compound, phosphorus element and halogen; and the organoaluminum compound comprises organoaluminum I and organoaluminum II, wherein the solid catalyst component does not comprise a silica carrier, wherein the organoaluminum I has the general formula AlR1R2R3, wherein R1, R2, R3 are the same or different, each independently is C6-C20 alkyl or C6-C20 aryl, and the organoaluminum II has the general formula AlR4R5R6, wherein R4, R5, R6 are the same or different, each independently is C1-C20 alkyl or C6-C20 aryl. 20hydrocarbyl groups; and wherein the organoaluminum II has the general formula AIR'1R'2R'3, wherein R'1, R'2, and R'3, are the same or different from each other, each independently a C1 to C5 hydrocarbyl group.

[0010] In a second aspect of the present application, there is provided the use of the catalyst system of the present application in an ethylene polymerization reaction, preferably in reducing the effect of temperature variation on the molecular weight of ultra-high molecular weight polyethylene in an ethylene polymerization reaction.

[0011] In a third aspect of the present application, there is provided a method for preparing ultra-high molecular weight polyethylene, the method comprising polymerizing ethylene in an inert solvent in the presence of the catalyst system of the present application to produce ultra-high molecular weight polyethylene. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 shows the activity of different catalyst systems as a function of time. DETAILED DESCRIPTION

[0013] The present application provides a catalyst system comprising a solid catalyst component and an organoaluminum compound; the solid catalyst component comprises titanium element, magnesium element, alkoxy compound, phosphorus element, and halogen; and the organoaluminum compound comprises organoaluminum I and organoaluminum II; wherein the solid catalyst component does not comprise a silica support, wherein the organoaluminum I has the general formula AIR1R2R3, wherein R1, R2, and R3, are the same or different from each other, each independently a C6 to C 20 hydrocarbyl groups; and wherein the organoaluminum II has the general formula AIR'1R'2R'3, wherein R'1, R'2, and R'3, are the same or different from each other, each independently a C1 to C5 hydrocarbyl group.

[0014] The catalyst system of the present application belongs to the Ziegler-Natta catalyst system used in ethylene polymerization.

[0015] In the present application, "does not comprise a silica support" means that the solid catalyst component does not comprise a silica support intentionally added, but does not exclude trace amounts of silica present as an impurity. Preferably, the silica is present in an amount of less than 0.5% by weight based on the weight of the solid catalyst component, more preferably, the silica is present in an amount of less than 0.1% by weight, most preferably, the solid catalyst component does not comprise a silica support at all.

[0016] In some embodiments, in the organoaluminum I, R1, R2, R3, are each independently a C6 to C 20 alkyl group, preferably a C6 to C 20 linear alkyl group.

[0017] In some embodiments, R1, R2, R3in the organoaluminum I are each independently a C6-C 12 alkyl group, preferably a C6-C 10 alkyl group, preferably a C6-C8alkyl group.

[0018] In some embodiments, the organoaluminum I is selected from at least one of tri-n-hexylaluminum, tri-n-octylaluminum, tri-n-decylaluminum, tri(dodecyl)aluminum, tri(tetradecyl)aluminum, tri(hexadecyl)aluminum, tri(octadecyl)aluminum, and tri(eicosyl)aluminum, more preferably tri-n-hexylaluminum and / or tri-n-octylaluminum.

[0019] In some embodiments, the organoaluminum II is selected from one or more of trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, and triisobutylaluminum, more preferably triethylaluminum and / or triisobutylaluminum.

[0020] In some embodiments, the organoaluminum compound comprises one or more of tri-n-hexylaluminum, tri-n-octylaluminum, and tri-n-decylaluminum, and one or more of trimethylaluminum, triethylaluminum, and triisobutylaluminum, preferably comprises one or more of tri-n-hexylaluminum and tri-n-octylaluminum, and one or more of triethylaluminum and triisobutylaluminum, more preferably comprises tri-n-hexylaluminum and triethylaluminum, or tri-n-octylaluminum and triethylaluminum.

[0021] In some embodiments, the molar ratio of the organoaluminum I and the organoaluminum II is (0.01-100):1, preferably (0.02-50):1, more preferably (0.1-10):1, more preferably (1-8):1, more preferably (3-6):1, even more preferably (4-5):1.

[0022] In some embodiments, the molar ratio of the total aluminum in the organoaluminum compound to titanium in the solid catalyst component is (5-5000):1, preferably (20-500):1, more preferably (100-400):1, even more preferably (200-300):1.

[0023] In some embodiments, the catalyst system is prepared by mixing the solid catalyst component and the organoaluminum compound.

[0024] In some embodiments, the content of the titanium element is 1-15 wt%, the content of the magnesium element is 10-30 wt%, the content of the phosphorus element is 0.01-1 wt%, the content of the alkoxy compound is 1-10 wt%, and the content of the halogen is 40-70 wt%, based on the total weight of the solid catalyst component.

[0025] In some embodiments, the content of the titanium element is 2wt% to 10wt%, the content of the magnesium element is 15wt% to 25wt%, the content of the phosphorus element is 0.1wt% to 0.8wt%, the content of the alkoxy compound is 2wt% to 8wt%, and the content of the halogen is 50wt% to 65wt%, based on the total weight of the solid catalyst component.

[0026] In some embodiments, the average particle size of the solid catalyst component is 2 to 10 microns, preferably 3 to 8 microns.

[0027] In some embodiments, the bulk density of the solid catalyst component is 0.3 to 0.5 g / ml, preferably 0.35 to 0.45 g / ml.

[0028] In the present application, the average particle size of the solid catalyst component is determined by a Mastersizer 2000 instrument (Malvern, UK), and the bulk density of the solid catalyst component is determined according to ASTM D1895-96.

[0029] In some embodiments, the titanium element is from a titanium compound, which can be various titanium compounds commonly used in the preparation of solid components of olefin polymerization catalysts. For example, the general formula of the titanium compound can be Ti(OR) a X b , wherein R is a C1 to C 14 aliphatic hydrocarbon group or a C6 to C 14 aromatic hydrocarbon group, X is a halogen atom, a is an integer of 0 to 4, b is an integer of 0 to 4, and a+b=3 or a+b=4.

[0030] In some embodiments, preferably, the titanium compound is selected from at least one of titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, titanium tetrabutoxide, titanium tetraethoxide, titanium chloride triethoxide, titanium dichloride diethoxide, titanium chloride monoethoxide, and titanium trichloride.

[0031] In some embodiments, the magnesium element is from a magnesium compound, which is selected from one of magnesium dihalide, a derivative of magnesium dihalide in which one halogen atom in the molecular formula is replaced by a hydrocarbon group or a halogen hydrocarbon oxy group, specifically including but not limited to magnesium chloride.

[0032] In some embodiments, the alkoxy compound is from an organic alcohol compound, which is selected from at least one of C1 to C8 linear or branched alcohols, preferably methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-octanol, and isooctanol.

[0033] In some embodiments, the phosphorus element is from an organic phosphorus compound selected from a hydrocarbyl or halogenated hydrocarbyl ester of orthophosphoric acid, a hydrocarbyl or halogenated hydrocarbyl ester of phosphorous acid.

[0034] In some embodiments, preferably, the organic phosphorus compound is selected from trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, tributyl phosphite, benzyl phosphite.

[0035] The solid catalyst component can be prepared using various methods known in the art.

[0036] In some embodiments, the method for preparing the solid catalyst component comprises:

[0037] dissolving a magnesium compound in a solvent system containing at least one organic epoxy compound, at least one organic phosphorus compound, at least one organic alcohol compound, and at least one inert diluent;

[0038] adding a co-precipitant, then lowering the system temperature and adding a titanium compound to obtain a suspension system containing a solid component;

[0039] raising the system temperature, and filtering, washing, and drying the suspension system to obtain the solid catalyst component.

[0040] For example, the solid catalyst component of the present application can be prepared by referring to CN112724284B or CN112724290B.

[0041] The number of times of adding the titanium compound is not particularly limited in the present application, which can be one, two, three, or more times; however, the titanium compound is added slowly dropwise each time.

[0042] In some embodiments, the organic epoxy compound is selected from at least one of an oxide of a C2-C8 aliphatic olefin or diene, an oxide of a C2-C8 halogenated aliphatic olefin or diene, a glycidyl ether, and an internal ether. Preferably, the organic epoxy compound is selected from oxirane, oxetane, butylene oxide, butadiene oxide, butadiene dioxide, epichlorohydrin, methyl glycidyl ether, and diglycidyl ether.

[0043] In some embodiments, the inert diluent is selected from at least one of hexane, heptane, octane, decane, benzene, toluene, xylene, or derivatives thereof.

[0044] In some embodiments, the co-precipitant is selected from at least one of organic acid, organic acid anhydride, organic ether, organic ketone, preferably at least one of acetic anhydride, phthalic anhydride, succinic anhydride, maleic anhydride, pyromellitic dianhydride, acetic acid, propionic acid, butyric acid, acrylic acid, methacrylic acid, acetone, methyl ethyl ketone, benzophenone, dimethyl ether, diethyl ether, dipropyl ether, dibutyl ether, amyl ether.

[0045] The second aspect of the present application provides use of the above-mentioned catalyst system in ethylene polymerization reaction. Preferably, the second aspect of the present application provides use of the catalyst system of the present application in ethylene polymerization reaction to reduce the influence of temperature change on the molecular weight of ultra-high molecular weight polyethylene.

[0046] As known in the art, in the industrial production of ultra-high molecular weight polyethylene, the molecular weight of the ultra-high molecular weight polyethylene decreases with the increase of polymerization temperature, and thus the change of temperature will have an influence on the molecular weight of the ultra-high molecular weight polyethylene. The catalyst system of the present application can reduce the influence of temperature on the molecular weight of the produced ultra-high molecular weight polyethylene and / or maintain the polymerization activity of the catalyst system for a long time. Reducing the influence of temperature on the molecular weight of the polymerization product can make the molecular weight of the polyethylene polymer more stable, which is beneficial to improve the quality of the ultra-high molecular weight polyethylene product.

[0047] In some embodiments, the catalyst system is suitable for use in slurry polymerization of ethylene, preferably for producing ultra-high molecular weight polyethylene at high temperature of 70-80°C.

[0048] In some embodiments, the solvent in the slurry polymerization of ethylene is selected from linear or branched alkanes, preferably hexane, heptane, octane, decane or derivatives thereof.

[0049] In some embodiments, the ultra-high molecular weight polyethylene has a viscosity average molecular weight of 4-6 million.

[0050] In some embodiments, the polymerization temperature is 70-90°C, preferably 70-80°C.

[0051] In some embodiments, the polymerization pressure is 0.05-10 MPa, preferably 0.1-5 MPa.

[0052] The third aspect of the present application provides a method for preparing ultra-high molecular weight polyethylene, which comprises polymerizing ethylene in an inert solvent in the presence of the catalyst system of the present application to produce ultra-high molecular weight polyethylene.

[0053] In some embodiments, the polymerization temperature is 70-90°C, preferably 70-80°C.

[0054] In some embodiments, the ultra-high molecular weight polyethylene can have a viscosity average molecular weight of 4-6 million.

[0055] In some embodiments, the polymerization pressure can be 0.05-10 MPa, preferably 0.1-5 MPa.

[0056] In some embodiments, the inert solvent can be selected from linear or branched alkanes, preferably hexane, heptane, octane, decane or derivatives thereof.

[0057] The present application has the following advantages:

[0058] Compared with the catalyst system of the prior art, the catalyst system of the present application is less sensitive to changes in polymerization temperature; that is, when the polymerization temperature changes, the change in the molecular weight of the polyethylene, particularly the ultra-high molecular weight polyethylene, prepared using the catalyst system of the present application (calculated in percentage) is significantly smaller than the change in the molecular weight of the polyethylene prepared using the catalyst system of the prior art. In addition, the catalyst system of the present application can maintain polymerization activity for a long time; that is, the polymerization activity remains stable or substantially stable over time. Therefore, the catalyst system of the present application can reduce the influence of temperature fluctuations on the molecular weight of the polymer during polymerization, providing a polyethylene product with improved molecular weight uniformity.

[0059] Examples

[0060] The following describes the examples of the present application in detail. It should be understood that the examples described herein are only for illustration and explanation of the present application, and are not intended to limit the present application.

[0061] In the following examples:

[0062] The activity of the catalyst is expressed as the mass of ethylene converted into product per unit mass of catalyst, with the unit being kilograms of polymer per gram of catalyst.

[0063] In the present application, the viscosity average relative molecular mass (M η ) of the polymer is determined by viscosity method according to standard GB / T1632.3-2010.

[0064] Preparation of solid catalyst component

[0065] Into a reaction kettle, 4.8 g of magnesium chloride, 55 ml of toluene, 3.0 ml of epichlorohydrin, 3.6 ml of tributyl phosphate, and 7.6 ml of ethanol were added, and the reaction was carried out at 55°C with stirring at 450 rpm for one hour. Then, 0.8 g of phthalic anhydride was added, and the reaction was carried out for one more hour. The temperature was lowered to -10°C, and 40 ml of titanium tetrachloride was added dropwise. The temperature was gradually raised to 80°C, and the reaction was carried out at this temperature for one hour. The mother liquor was filtered off, and the residue was washed twice with 60°C toluene (120 ml) and four times with hexane. The solid catalyst component Z1 was obtained by vacuum drying.

[0066] Into a 250 ml three-necked flask, 1.5 g of titanium tetrachloride, 4.0 g of magnesium chloride, and 100 ml of tetrahydrofuran were sequentially added, and the temperature was raised to 65°C with stirring. The reaction was carried out at this temperature for three hours, and then the temperature was lowered to 35°C. The mother liquor was used as it was. Into another 250 ml three-necked flask, 6 g of silica gel (Cabot Corporation TS-610, particle size: 0.02 to 0.1 μm) was added, and the temperature-lowered mother liquor was added. The temperature was maintained at 35°C, and the stirring was carried out for one hour. The silica gel-mixed mother liquor was spray-dried using a spray dryer under the following conditions: inlet temperature: 195°C, and outlet temperature: 110°C. The solid catalyst component Z2 was obtained.

[0067] Examples 1 to 15 and Comparative Examples 1 to 15, 25 to 34

[0068] Into a 48-channel parallel pressure reactor (reaction volume: 20 ml), the reactor was replaced with ethylene at room temperature, and organoaluminum I and organoaluminum II were added to the reactor. The temperature was maintained, and the ethylene pressure was controlled at 0.3 MPa. Then, the solid catalyst component Z1 was added to the reactor, and the polymerization reaction was carried out at this temperature for two hours.

[0069] Comparative Examples 16 to 24, 35 to 40

[0070] Into a 48-channel parallel pressure reactor (reaction volume: 20 ml), the reactor was replaced with ethylene at room temperature, and organoaluminum I and organoaluminum II were added to the reactor. The temperature was maintained, and the ethylene pressure was controlled at 0.3 MPa. Then, the solid catalyst component Z2 was added to the reactor, and the polymerization reaction was carried out at this temperature for one hour.

[0071] Examples 16 to 27 and Comparative Examples 41 to 46

[0072] Into a 48-channel parallel pressure reactor (reaction volume: 20 ml), the reactor was replaced with ethylene at room temperature, and organoaluminum I and organoaluminum II were added to the reactor. The temperature was maintained, and the ethylene pressure was controlled at 0.3 MPa. Then, the solid catalyst component Z1 was added to the reactor, and the polymerization reaction was carried out at this temperature.

[0073] The polymerization activities and product properties of the above examples and comparative examples are shown in Tables 1-3 and Figure 1.

[0074] Table 1

[0075] Note 1: TEAL is triethylaluminum;

[0076] TIBA is triisobutylaluminum;

[0077] THAL is tri-n-hexylaluminum;

[0078] TOAL is tri-n-octylaluminum;

[0079] THDAL is trihexadecylaluminum.

[0080] Note 2: The molar ratio of aluminum element in the cocatalyst to titanium element in the solid catalyst component n(Al) / n(Ti) = 250.

[0081] From the experimental results, it can be found that when the long and short chain organoaluminum are used in combination (Examples 1-9), the viscosity average molecular weight decreases by a maximum of 22% when the polymerization temperature is increased from 70°C to 80°C; while the viscosity average molecular weight decreases by 50% when the currently used cocatalysts triethylaluminum or triisobutylaluminum systems (Comparative Examples 1-6) are used. In comparison with the use of long chain organoaluminum alone (Comparative Examples 7-15), the viscosity average molecular weight decreases slowly while maintaining a high polymerization activity, meeting the requirements of industrial applications. For the catalyst systems containing silicon (Comparative Examples 16-24), the viscosity average molecular weight decreases more for the long and short chain organoaluminum combination and the long chain organoaluminum system than for the short chain organoaluminum system, indicating that the influence of organoaluminum on the viscosity average molecular weight against temperature fluctuation is related to the catalyst system.

[0082] Table 2

[0083] Note 3: The polymerization temperature is 80°C.

[0084] From the experimental results, it can be found that when the long and short chain organoaluminum are used in combination (Examples 10-15), the viscosity average molecular weight decreases by a maximum of 7% when the aluminum-titanium ratio is increased from 100 to 350; while the viscosity average molecular weight decreases by 24% when the currently used cocatalysts triethylaluminum or triisobutylaluminum systems (Comparative Examples 25-28) are used. In comparison with the use of long chain organoaluminum alone (Comparative Examples 29-34), the viscosity average molecular weight decreases slowly while maintaining a high polymerization activity, meeting the requirements of industrial applications. For the catalyst systems containing silicon (Comparative Examples 35-40), the viscosity average molecular weight decreases more for the long and short chain organoaluminum combination than for the long chain organoaluminum and short chain organoaluminum systems, indicating that the influence of organoaluminum on the viscosity average molecular weight against aluminum-titanium ratio fluctuation is related to the catalyst system.

[0085] Table 3

[0086] Note 4: The mole ratio of aluminum element in the cocatalyst to titanium element in the solid catalyst component n(Al) / n(Ti) = 250; polymerization temperature 80°C.

[0087] From the experimental results, it can be found that the long and short chain organoaluminum complex (Examples 16-27) has stable activity with the extension of polymerization time; the long chain organoaluminum system also has stable activity, but the overall activity is too low (Comparative Examples 41-43). The cocatalyst triethylaluminum system currently used in industry (Comparative Examples 44-46) gradually decays with the extension of polymerization time.

[0088] Therefore, the polymerization system of long and short chain organoaluminum complex has better temperature stability, aluminum-titanium ratio stability and longer polymerization life.

[0089] Any numerical values recited herein include all values from the lower value and up to the higher value. In this respect, the disclosure as contained herein is also expressly intended to cover all such replacement values. Ranges provided herein are intended to include any and all sub-ranges of the range. For example, a range of 2 to 10 inclusive is intended to include any and all sub-ranges between and including the minimum value of 2 and the maximum value of 10, that is, all sub-ranges beginning with a minimum value equal to or greater than 2 and ending with a maximum value equal to or less than 10, and all sub-ranges beginning with a minimum value equal to or greater than 2 and ending with a maximum value equal to or less than 10, as well as all sub-ranges beginning and ending with values between 2 and 10 inclusive. The same applies to ranges recited with respect to other values such as temperature, pressure, time and the like. With respect to non-integer values, one having ordinary skill in the art will understand that the values are to be taken as provided herein, with the same degree of precision. For example, a value recited as 2.5 is to be taken to the same degree of precision as 2.5000, and so on. This is merely an example and is in no way intended to limit the present disclosure. In this application, the use of "about" is intended to describe or approximate a value, and is not meant to be limited to a precise value. Any numerical value, however, can explicitly exclude any value outside the stated range unless otherwise specifically indicated.

[0090] It should be noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting the present application. Having described at least one of the embodiments of the present application in detail, various modifications and improvements will readily occur to those skilled in the art. Such modifications and improvements are intended to be within the scope of the present application. Although the present application has been described in detail with reference to particular methods, materials and embodiments, it should be understood that the application is not limited to such disclosed embodiments. Instead, it extends to any alternative embodiments and modifications within the scope and spirit of the present application, and as described in the claims.

Claims

1. A catalyst system characterized in that, The catalyst system comprises a solid catalyst component and an organoaluminum compound; the solid catalyst component comprises titanium element, magnesium element, alkoxy compound, phosphorus element and halogen; and the organoaluminum compound comprises organoaluminum I and organoaluminum II; The solid catalyst component does not comprise a silica carrier; wherein said organoaluminum I has the general formula AIR1R2R3, wherein R1, R2and R3are the same or different from each other, each independently a C6to C 20 hydrocarbyl group; and wherein said organoaluminum II has the general formula AIR'1R'2R'3, wherein R'1, R'2and R'3are the same or different from each other, each independently a C1to C5hydrocarbyl group.

2. The catalyst system of claim 1, wherein, R1, R2and R3are each independently a C6to C20alkyl group, preferably a C6to C 20 straight chain alkyl group; preferably, the organoaluminum I is selected from at least one of tri-n-hexylaluminum, tri-n-octylaluminum, tri-n-decylaluminum, tri(dodecyl)aluminum, tri(tetradecyl)aluminum, tri(hexadecyl)aluminum, tri(octadecyl)aluminum, and tri(eicosyl)aluminum; 20 R1, R2and R3are each independently a C6to C20alkyl group, preferably a C6to C 20 straight chain alkyl group; preferably, the organoaluminum I is selected from at least one of tri-n-hexylaluminum, tri-n-octylaluminum, tri-n-decylaluminum, tri(dodecyl)aluminum, tri(tetradecyl)aluminum, tri(hexadecyl)aluminum, tri(octadecyl)aluminum, and tri(eicosyl)aluminum; 20 R1, R2and R3are each independently a C6to C20alkyl group, preferably a C More preferably, R1, R2and R3are each independently C6to C 12 alkyl, more preferably C6to C 10 alkyl, more preferably C6to C8alkyl.

3. Catalyst system according to claim 1 or 2, characterized in that The organoaluminum II is selected from one or more of trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum and triisobutylaluminum.

4. The catalyst system according to any one of claims 1 to 3, characterized in that, The molar ratio of the organoaluminum I and organoaluminum II is (0.01-100):1, preferably (0.02-50):1, and more preferably (0.1-10):

1.

5. The catalyst system according to any one of claims 1 to 4, characterized in that, The molar ratio of total aluminum in the organoaluminum compound to titanium in the solid catalyst component is (5-5000):1, preferably (20-500):

1.

6. The catalyst system according to any one of claims 1 to 5, characterized in that, The content of the titanium element is 1wt%-15wt%, the content of the magnesium element is 10wt%-30wt%, the content of the phosphorus element is 0.01wt%-1wt%, the content of the alkoxy compound is 1wt%-10wt%, and the content of the halogen is 40wt%-70wt%, based on the total weight of the solid catalyst component; Preferably, the content of the titanium element is 2wt%-10wt%, the content of the magnesium element is 15wt%-25wt%, the content of the phosphorus element is 0.1wt%-0.8wt%, the content of the alkoxy compound is 2wt%-8wt%, and the content of the halogen is 50wt%-65wt%, based on the total weight of the solid catalyst component.

7. The catalyst system according to any one of claims 1 to 6, characterized in that, The average particle size of the solid catalyst component is 2-10 microns, preferably 3-8 microns; And / or, the bulk density of the solid catalyst component is 0.3-0.5 g / ml, preferably 0.35-0.45 g / ml.

8. The catalyst system according to any one of claims 1 to 7, characterized in that, The titanium element comes from a titanium compound of general formula Ti(OR) a X b , in which R is a C1-C 14 aliphatic hydrocarbon group or a C6-C 14 aromatic hydrocarbon group, X is a halogen atom, a is an integer from 0 to 4, b is an integer from 0 to 4, and a+b = 3 or 4; preferably, the titanium compound is chosen from at least one of titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, titanium tetrabutoxide, titanium tetraethoxide, titanium monochlorotriethoxide, titanium dichlorodiethoxide, titanium trichloroethoxide, and titanium trichloride; And / or, the magnesium element is from a magnesium compound, wherein the magnesium compound is selected from at least one of magnesium dihalide and a derivative of magnesium dihalide formula in which one halogen atom is replaced by a hydrocarbon group or a halogen hydrocarbon oxy group, preferably magnesium chloride; And / or, the alkoxy compound is from an organic alcohol compound, and the organic alcohol compound is selected from at least one of C1-C8 linear or branched alcohol, preferably methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-octanol, isooctanol; And / or, the phosphorus element is from an organic phosphorus compound, and the organic phosphorus compound is selected from at least one of hydrocarbon or halogen hydrocarbon ester of orthophosphoric acid, hydrocarbon or halogen hydrocarbon ester of phosphorous acid; preferably, the organic phosphorus compound is selected from trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, tributyl phosphite and benzyl phosphite.

9. The catalyst system according to any one of claims 1 to 8, characterized in that, The preparation method of the solid catalyst component comprises: dissolving the magnesium compound in a solvent system containing at least one organic epoxy compound, at least one organic phosphorus compound, at least one organic alcohol compound and at least one inert diluent; adding a co-precipitant, then reducing the system temperature and adding a titanium compound to obtain a suspension system containing the solid catalyst component; ​ The solid catalyst component is obtained by filtering, washing and drying the suspension system at an elevated temperature.

10. The catalyst system of claim 9, wherein, The organic epoxide compound is selected from at least one of the group consisting of C2-C8 aliphatic olefin or diene oxide, C2-C8 halogenated aliphatic olefin or diene oxide, glycidyl ether and internal ether; preferably, the organic epoxide compound is selected from at least one of the group consisting of oxirane, oxetane, butylene oxide, butadiene oxide, butadiene dioxide, epichlorohydrin, methyl glycidyl ether and diglycidyl ether; and / or, the inert diluent is selected from at least one of the group consisting of hexane, heptane, octane, decane, benzene, toluene, xylene, or derivatives thereof; and / or, the co-leaching agent is selected from at least one of the group consisting of organic acid, organic acid anhydride, organic ether, organic ketone, preferably at least one of the group consisting of acetic anhydride, phthalic anhydride, succinic anhydride, maleic anhydride, pyromellitic dianhydride, acetic acid, propionic acid, butyric acid, acrylic acid, methacrylic acid, acetone, methyl ethyl ketone, benzophenone, dimethyl ether, diethyl ether, dipropyl ether, dibutyl ether, amyl ether.

11. Use of the catalyst system according to any one of claims 1 to 10 in an ethylene polymerization reaction, preferably for reducing the effect of temperature variation on the molecular weight of ultra-high molecular weight polyethylene.

12. Use according to claim 11, characterized in that, The catalyst system is used in a slurry polymerization reaction of ethylene, preferably for producing ultra-high molecular weight polyethylene at a temperature of 70-90°C.

13. Use according to claim 12, characterized in that, The solvent in the slurry polymerization reaction is selected from linear or branched alkanes, preferably hexane, heptane, octane, decane or derivatives thereof; and / or, the ultra-high molecular weight polyethylene has a viscosity average molecular weight of 4-6 million; and / or, the polymerization reaction is carried out at a temperature of 70-90°C, preferably 70-80°C; and / or, the polymerization reaction is carried out at a pressure of 0.05-10 MPa, preferably 0.1-5 MPa.

14. A process for the preparation of ultra-high molecular weight polyethylene, characterized in that, The preparation method comprises polymerizing ethylene in an inert solvent in the presence of the catalyst system according to any one of claims 1 to 10 to produce ultra-high molecular weight polyethylene.

15. The preparation method according to claim 14, characterized in that, The ultra-high molecular weight polyethylene has a viscosity average molecular weight of 4-6 million; and / or, the polymerization reaction is carried out at a temperature of 70-90°C, preferably 70-80°C and / or, the polymerization reaction is carried out at a pressure of 0.05-10 MPa, preferably 0.1-5 MPa. and / or, the inert solvent is selected from linear or branched alkanes, preferably hexane, heptane, octane, decane or derivatives thereof.

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