Ultrahigh molecular weight polyethylene, polyethylene composition, polyethylene resin and preparation method and application thereof

Abstract

The invention relates to the field of ultra-high molecular weight polyethylene, and discloses ultra-high molecular weight polyethylene, polyethylene resin, a polyethylene composition and a preparation method and application thereof. The molecular chain of the ultra-high molecular weight polyethylene contains a chain segment A and a branched chain B; wherein the chain segment A is provided by an ethylene monomer, and the branch chain B is provided by an alpha-olefin monomer with the carbon atom number of 3-6; on the basis of the total weight of the ultra-high molecular weight polyethylene, the content of the chain segment A is 99-99.95 wt%, and the content of the branched chain B is 0.05-1 wt%. The ultra-high molecular weight polyethylene has the characteristics of low element residue content and low molecular chain entanglement density, and the polyethylene resin prepared from the ultra-high molecular weight polyethylene has excellent impact strength on the premise of meeting the wear resistance requirement (the mortar wear rate is less than or equal to 110%).

Description

Technical Field

[0001] The present invention relates to the field of ultra-high molecular weight polyethylene, and particularly relates to an ultra-high molecular weight polyethylene, a polyethylene composition, a polyethylene resin, and a preparation method and application thereof. Background Art

[0002] With the aging of the world's population, the increase in high-strength sports injuries, and the impact of factors such as diet and environment on the body, clinical medicine has put forward higher requirements for the performance of artificial joint implant materials. The demand from patients is increasing day by day, and the potential market is huge.

[0003] Among many human joint implant materials, UHMWPE composite materials have a hardness close to that of natural bones, excellent biomechanical properties and biocompatibility, are resistant to friction and wear, and do not cause any other allergic reactions. It is an ideal artificial joint material.

[0004] This product belongs to a small and high-end imported raw material replacement. Compared with general-grade UHMWPE, the annual consumption is not large, but the added value is extremely high. Due to the high price of imported UHMWPE artificial joint profile materials, the price is as high as 2 million - 5 million yuan / ton, which is hundreds of times the price of non-medical UHMWPE products (selling price: 15,000 - 20,000 yuan / ton). The high import cost increases the production cost of medical device enterprises and greatly increases the national medical insurance and patient medical burden.

[0005] CN107936164A discloses an ultra-high molecular weight polyethylene and its manufacturing method and application. By copolymerizing with α-olefins, the introduction of a large amount of comonomers reduces the impact performance and wear rate of the polymer, but the impact performance can only adopt the standard of ordinary polyethylene.

[0006] CN109694439A discloses a preparation method of ultra-high molecular weight polyethylene. Using a copolymerization process, its molecular weight does not exceed 3 million, and the impact strength does not exceed 50 kJ / m 2 .

[0007] The impact strength of the above ultra-high molecular weight polyethylene is relatively low and cannot meet the requirements for use in artificial joints. Moreover, as an artificial joint implant material, ultra-high molecular weight polyethylene has extremely high requirements for biocompatibility. During the preparation of UHMWPE, the residual amounts of the catalyst are required to be Ti ≤ 40 ppm, Al ≤ 20 ppm, and Cl ≤ 30 ppm.

[0008] Therefore, it is urgent to develop an ultra-high molecular weight polyethylene material with excellent performance for use in human joints. Summary of the Invention

[0009] The object of the present invention is to overcome the problems of low impact strength and high wear rate of ultra-high molecular weight polyethylene in the prior art, and to provide an ultra-high molecular weight polyethylene, a polyethylene resin, a polyethylene composition, and a preparation method and application thereof. The ultra-high molecular weight polyethylene has the characteristics of low elemental residue content and low molecular chain entanglement density, and the polyethylene resin prepared from the polyethylene composition containing the ultra-high molecular weight polyethylene has excellent impact strength on the premise of meeting the wear resistance requirement (mortar wear rate ≤ 110%).

[0010] To achieve the above object, in the first aspect of the present invention, an ultra-high molecular weight polyethylene is provided, which is characterized in that the molecular chain of the ultra-high molecular weight polyethylene contains a chain segment A and a branch chain B;

[0011] Among them, the chain segment A is provided by an ethylene monomer, and the branch chain B is provided by an α-olefin monomer with 3 to 6 carbon atoms;

[0012] Based on the total weight of the ultra-high molecular weight polyethylene, the content of the chain segment A is 99 - 99.95 wt%, and the content of the branch chain B is 0.05 - 1 wt%.

[0013] In the second aspect of the present invention, a preparation method of an ultra-high molecular weight polyethylene is provided, which is characterized in that the method includes the following steps:

[0014] S1. In the presence of a solvent, a first ethylene, a main catalyst, and a cocatalyst are mixed evenly, and a first polymerization reaction is carried out to obtain an ethylene homopolymer;

[0015] S2. After mixing the above ethylene homopolymer, a second ethylene, and an α-olefin with 3 to 6 carbon atoms, a second polymerization reaction is carried out to obtain the ultra-high molecular weight polyethylene;

[0016] Among them, based on the total monomer addition amount, the addition amount of the first ethylene is 1 - 10 kg / h; the addition amount of the second ethylene is 10 - 50 kg / h, and the addition amount of the α-olefin with 3 to 6 carbon atoms is 0.01 - 0.5 kg / h.

[0017] In the third aspect of the present invention, an ultra-high molecular weight polyethylene prepared by the preparation method provided in the second aspect is provided.

[0018] In the fourth aspect of the present invention, a polyethylene composition is provided, which is characterized in that the composition includes the ultra-high molecular weight polyethylene provided in the third aspect and an antioxidant.

[0019] In the fifth aspect of the present invention, a method for preparing a polyethylene resin is provided, which is characterized in that the method includes: mixing the polyethylene composition provided in the fourth aspect to obtain a mixture, and then carrying out molding and demolding on the mixture to obtain the polyethylene resin.

[0020] The sixth aspect of the present invention provides a polyethylene resin prepared by the method provided in the fifth aspect.

[0021] The seventh aspect of the present invention provides an application of the ultra-high molecular weight polyethylene provided in the first aspect or the third aspect, the polyethylene composition provided in the fourth aspect, and the polyethylene resin provided in the sixth aspect in artificial joint implant materials.

[0022] Through the above technical solutions, the ultra-high molecular weight polyethylene, polyethylene resin, polyethylene composition provided by the present invention, and their preparation methods and applications obtain the following beneficial technical effects:

[0023] The ultra-high molecular weight polyethylene provided by the present invention contains specific contents of segment A and segment B, has the characteristic of low molecular chain entanglement density, and the polyethylene resin prepared from the polyethylene of the ultra-high molecular weight polyethylene has excellent impact strength on the premise of meeting the wear resistance requirement (mortar wear rate ≤ 110%). Detailed Embodiments

[0024] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0025] The first aspect of the present invention provides an ultra-high molecular weight polyethylene, characterized in that the molecular chain of the ultra-high molecular weight polyethylene contains segment A and side chain B;

[0026] Among them, segment A is provided by ethylene monomer, and side chain B is provided by an α-olefin monomer with 3 to 6 carbon atoms;

[0027] Based on the total weight of the ultra-high molecular weight polyethylene, the content of segment A is 99 - 99.95 wt%, and the content of side chain B is 0.05 - 1 wt%.

[0028] According to the present invention, based on the total weight of the ultra-high molecular weight polyethylene, the content of segment A is 99.3 - 99.8 wt%, and the content of side chain B is 0.2 - 0.7 wt%.

[0029] According to the present invention, the content of Ti in the ultra-high molecular weight polyethylene is ≤ 30 ppm, the content of Al is ≤ 20 ppm, and the content of Cl is ≤ 30 ppm.

[0030] In the present invention, when the elemental contents of Ti, Al, and Cl in the ultra-high molecular weight polyethylene meet the above ranges respectively, the polyethylene resin prepared from the ultra-high molecular weight polyethylene has good biocompatibility when applied to human joints.

[0031] Further, in the ultra-high molecular weight polyethylene, the content of Ti is ≤27 ppm, the content of Al is ≤18 ppm, and the content of Cl is ≤25 ppm.

[0032] In the present invention, when the elemental contents of Ti, Al, and Cl meet the above ranges respectively, the comprehensive performance of the polyethylene resin prepared from the ultra-high molecular weight polyethylene is better.

[0033] According to the present invention, the entanglement density of the molecular chains of the ultra-high molecular weight polyethylene is ≤600 mol / m 3 .

[0034] In the present invention, when the entanglement density of the molecular chains of the ultra-high molecular weight polyethylene meets the above range, it is beneficial to the diffusion of molecular chains during the processing, and can further improve the impact strength of the material.

[0035] Further, the entanglement density of the molecular chains of the ultra-high molecular weight polyethylene is 300 - 521 mol / m 3 .

[0036] According to the present invention, the intrinsic viscosity of the ultra-high molecular weight polyethylene at 135 °C is 1800 - 3800 mL / g, preferably 2200 - 3200 mL / g.

[0037] In the present invention, the unit of the intrinsic viscosity is mL / g, and it can also be converted to dL / g. For example, 3800 mL / g is equal to 38 dL / g.

[0038] According to the present invention, the viscosity-average molecular weight of the ultra-high molecular weight polyethylene is 2.8 million - 8 million, preferably 3.8 million - 7.5 million.

[0039] In the present invention, when the intrinsic viscosity and the viscosity-average molecular weight of the ultra-high molecular weight polyethylene meet the above ranges, the material has good abrasion resistance.

[0040] The second aspect of the present invention provides a method for preparing ultra-high molecular weight polyethylene, which is characterized in that the method includes the following steps:

[0041] S1. In the presence of a solvent, mix the first ethylene, the main catalyst, and the cocatalyst evenly, and carry out the first polymerization reaction to obtain an ethylene homopolymer;

[0042] S2. After mixing the above ethylene homopolymer, the second ethylene, and the α-olefin having 3 to 6 carbon atoms, a second polymerization reaction is carried out to obtain the ultra-high molecular weight polyethylene;

[0043] Among them, based on the total monomer addition amount, the addition amount of the first ethylene is 1 - 10 kg / h; the addition amount of the second ethylene is 10 - 50 kg / h, and the addition amount of the α-olefin having 3 to 6 carbon atoms is 0.01 - 0.5 kg / h.

[0044] In the present invention, there is no particular requirement for the solvent. For example, it can be selected from hydrocarbons: pentane, cyclopentane, hexane, cyclohexane, heptane, octane, hexane, heptane, cyclohexane, benzene, toluene, and xylene;

[0045] ethers: dimethoxyethane, diethylene glycol dimethyl ether, tetrahydrofuran, dioxane, and tert-butyl methyl ether;

[0046] alcohols: methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, 1-butanol, 2-butanol, and tert-butanol;

[0047] ketones: acetone, methyl ethyl ketone, and isobutyl methyl ketone;

[0048] amides: dimethylformamide, dimethylacetamide, and N-methylpyrrolidone.

[0049] In the present invention, the solvent is preferably at least one of hexane, pentane, and isobutane.

[0050] According to a preferred embodiment of the present invention, the addition amount of the first ethylene is 5 - 10 kg / h; the addition amount of the second ethylene is 16 - 30 kg / h.

[0051] According to a preferred embodiment of the present invention, the addition amount of the α-olefin having 3 to 6 carbon atoms is 0.4 - 0.5 kg / h.

[0052] In the present invention, at least one of the α-olefins having 3 to 6 carbon atoms.

[0053] According to a preferred embodiment of the present invention, the α-olefin is propylene.

[0054] Furthermore, the α-olefin having 3 to 6 carbon atoms is added in any one or several polymerization reactors of the second polymerization reaction.

[0055] According to the present invention, the conditions of the first polymerization reaction include: a polymerization temperature of 20 - 50 °C, a polymerization pressure of 0.2 - 2 MPa, and a polymerization time of 0.1 - 0.8 h.

[0056] According to the present invention, the conditions for the second polymerization reaction include: a polymerization temperature of 30 - 110 °C, a polymerization pressure of 0.3 - 4 MPa, and a polymerization time of 0.5 - 4 h.

[0057] In the present invention, when the conditions of the first polymerization reaction and the second polymerization reaction satisfy the above ranges, the ultra-high molecular weight polyethylene prepared has the characteristics of high polymerization reaction efficiency and low molecular chain entanglement density.

[0058] According to the present invention, the first polymerization reaction is a batch polymerization reaction, and the second polymerization reaction is a continuous polymerization reaction.

[0059] Further, the first polymerization reaction includes 2 - 3 reaction vessels connected in parallel.

[0060] Further, the second polymerization reaction includes 1 - 3 reaction vessels connected in series.

[0061] Even further, the second polymerization reaction includes 2 - 3 reaction vessels connected in series.

[0062] In the present invention, when the first polymerization reaction and the second polymerization reaction satisfy the above forms, the ultra-high molecular weight polyethylene prepared has the advantages of strong molecular weight controllability and high molecular weight.

[0063] According to the present invention, the main catalyst is a Ti-containing compound, preferably titanium halide and / or Ti(OR) n X 4-n , where R is an alkyl group with 1 - 5 carbon atoms, n is an integer from 1 to 3, and X is a halogen.

[0064] According to an embodiment of the present invention, the catalyst activity of the main catalyst > 10 kgPE / gCat.

[0065] According to an embodiment of the present invention, the cocatalyst is selected from at least one of alkyl aluminum, sesquialkyl aluminum halide, and alkyl aluminum oxane.

[0066] According to the present invention, the mass ratio of the main catalyst to the first ethylene is 1:1×10 4 -2.5×10 4 , preferably 1:1.5×10 4 -2.2×10 4 .

[0067] According to the present invention, the molar ratio of the cocatalyst calculated as aluminum to the main catalyst calculated as titanium is 15 - 60:1, preferably 25 - 40:1.

[0068] In the present invention, when the addition amounts of the main catalyst and the cocatalyst meet the above ranges, the resulting ultra-high molecular weight polyethylene has a low elemental content and better biocompatibility.

[0069] According to a particularly preferred embodiment of the present invention, the method comprises the following steps:

[0070] First polymerization reaction: including 2 - 3 reactors in parallel, adding a solvent, a main catalyst, a cocatalyst, and ethylene into each reactor respectively, and carrying out a polymerization reaction to obtain an ethylene homopolymer;

[0071] Second polymerization reaction: including 1 - 3 reactors in series, adding the above ethylene homopolymer into the first reactor, continuously adding ethylene, and adding an α-olefin monomer to carry out the second polymerization reaction I. The product of the first reactor enters the second reactor to carry out the second polymerization reaction II to obtain ultra-high molecular weight polyethylene;

[0072] Wherein, the addition amount of the first ethylene is 1 - 10 kg / h; the addition amount of the second ethylene is 10 - 50 kg / h, and the addition amount of the α-olefin with 3 - 6 carbon atoms is 0.01 - 0.5 kg / h.

[0073] The third aspect of the present invention provides an ultra-high molecular weight polyethylene prepared by the preparation method provided in the second aspect.

[0074] The fourth aspect of the present invention provides a polyethylene composition, characterized in that the composition comprises the ultra-high molecular weight polyethylene provided in the third aspect and an antioxidant;

[0075] Based on the total weight of the composition, the dosage of the ultra-high molecular weight polyethylene is 97 - 99.5 wt%, and the dosage of the antioxidant is 0.5 - 3 wt%.

[0076] In the present invention, when the dosage of the polyethylene composition meets the above range, the resulting polyethylene resin has a higher impact strength on the premise of meeting the wear resistance requirement (mortar wear rate ≤ 110%).

[0077] According to the present invention, the antioxidant comprises component A and / or component B.

[0078] According to an embodiment of the present invention, it is at least one selected from tocopherol, tocotrienol, tocopherol acetate, tocopherol succinate, tocopherol nicotinate, tocopherol linoleate, tocopherol phosphate, tocopherol retinoate, and tocopherol palmitate.

[0079] According to an embodiment of the present invention, the component B is selected from ascorbyl palmitate and / or retinol.

[0080] According to an embodiment of the present invention, the mass ratio of component A to component B is 1:0.1 - 1.

[0081] According to a preferred embodiment of the present invention, the mass ratio of component A to component B is 0.2 - 0.8.

[0082] The fifth aspect of the present invention provides a method for preparing a polyethylene resin, characterized in that the method includes: mixing the polyethylene composition provided in the fourth aspect to obtain a mixture, and then performing molding and demolding on the mixture to obtain the polyethylene resin.

[0083] According to the present invention, the molding includes the following processes: sequentially performing pretreatment, molding treatment, first cooling, post-treatment, and second cooling on the above-mentioned mixture.

[0084] In the present invention, the steps of the post-treatment enable the molecular chains to be fully untangled and recrystallized, release the internal stress of the material, and form a uniform profile without internal structural defects.

[0085] According to the present invention, the conditions of each step in the molding process include: pretreatment temperature 150 - 210 °C, pretreatment pressure 5 - 10 MPa, and pretreatment time 5 - 15 min.

[0086] According to the present invention, the conditions of the molding treatment include: molding temperature 210 - 300 °C, molding pressure 15 - 25 MPa, and pressure holding time 2 - 5 h.

[0087] According to a preferred embodiment of the present invention, the conditions of the molding treatment are preferably: molding temperature 220 - 250 °C, molding pressure 16 - 20 MPa, and pressure holding time 3 - 4 h.

[0088] According to the present invention, the conditions of the first cooling include: cooling at a rate of 5 - 10 °C / min to 130 - 180 °C.

[0089] According to the present invention, the conditions of the post-treatment include: keeping the temperature at 130 - 180 °C for 2 - 3 h.

[0090] According to the present invention, the conditions of the second cooling include: cooling at a rate of 10 - 20 °C / min to room temperature.

[0091] In the present invention, during the first cooling, post-treatment, and second cooling, the pressure remains unchanged.

[0092] According to the present invention, when the conditions of each step in the molding process meet the above ranges, the prepared polyethylene resin has the characteristics of good crystal uniformity in the crystalline region and elimination of stress concentration.

[0093] The sixth aspect of the present invention provides a polyethylene resin prepared by the method provided in the fifth aspect.

[0094] The seventh aspect of the present invention provides an application of the ultra-high molecular weight polyethylene provided in the first aspect or the third aspect, the polyethylene composition provided in the fourth aspect, and the polyethylene resin provided in the sixth aspect in artificial joint implant materials.

[0095] The present invention will be described in detail below through examples. In the following preparation examples or examples,

[0096] The viscosity-average molecular weight was determined by the intrinsic viscosity using a high-temperature Ubbelohde viscometer according to the standard of ASTM D4020-18, and calculated using the following formula 1:

[0097] M η = 5.37×10 4 × [η] 1.37 ; (Formula 1)

[0098] The entanglement density of molecular chains was obtained by the rubber elasticity theory, and the entanglement molecular weight M e was obtained using formula 2, and the entanglement density υ e was obtained using formula 3:

[0099]

[0100]

[0101] where ρ is the density of the polymer in the molten state, R is the universal gas constant, T is the absolute temperature under the test conditions, and G e is the shear plateau modulus;

[0102] The residual amounts of Ti, Al, and Cl were tested using an X-ray fluorescence spectrometer;

[0103] The notched Izod impact strength of the simply supported beam was tested according to GB / T 21461.2-2008, with a pendulum energy of 50 J and a double-notch specimen;

[0104] The mortar wear rate was tested according to GB / T 4020-18, and the reference sample was Ticona GUR 4120;

[0105] The branched chain content of ultra-high molecular weight polyethylene was obtained by high-resolution solid nuclear magnetic resonance method;

[0106] The raw materials used in the examples and comparative examples are all commercially available products.

[0107] Unless otherwise specified, the following intrinsic viscosities were measured at 135 °C.

[0108] Preparation Example 1

[0109] First polymerization reaction: Two identical batch stirred polymerization reactors are connected in parallel. In the presence of the solvent hexane, ethylene, the main catalyst titanium tetrachloride, and the co-catalyst triethylaluminum are added to the two reactors respectively. Among them, the addition amount of ethylene is 5 kg / h, the main catalyst is 1.5 g / h, and the molar ratio of the co-catalyst calculated by aluminum to the main catalyst calculated by titanium is 30:1. The polymerization reaction is carried out at 40 °C and 0.4 MPa for 0.4 h to obtain ethylene homopolymer;

[0110] Second polymerization reaction: Two continuous stirred polymerization reactors are connected in series. The above-mentioned ethylene homopolymer is added to the first reactor, and ethylene is continuously added with an addition amount of 30 kg / h. At the same time, propylene is added with an addition amount of 0.3 kg / h. The polymerization temperature is 80 °C, the polymerization pressure is 1.5 MPa, and the polymerization time is 1.5 h. The product of the first reactor enters the second reactor, with a polymerization temperature of 80 °C, a polymerization pressure of 1.5 MPa, and ethylene is continuously added with an addition amount of 30 kg / h, and the polymerization time is 1.5 h. Ultra-high molecular weight polyethylene A1 is obtained.

[0111] The intrinsic viscosity, viscosity-average molecular weight, content of chain segment A, content of branch chain B, Ti content, Al content, Cl content, and molecular chain entanglement density of the ultra-high molecular weight polyethylene A1 are shown in Table 1.

[0112] Preparation Example 2

[0113] The method is the same as that of Preparation Example 1, except that the polymerization temperature of the first polymerization reaction is 30 °C and the polymerization pressure is 0.5 MPa to obtain ultra-high molecular weight polyethylene A2.

[0114] The intrinsic viscosity, viscosity-average molecular weight, content of chain segment A, content of branch chain B, Ti content, Al content, Cl content, and molecular chain entanglement density of the ultra-high molecular weight polyethylene A2 are shown in Table 1.

[0115] Preparation Example 3

[0116] The method is the same as that of Preparation Example 1, except that the polymerization time of the first polymerization reaction is 0.6 h to obtain ultra-high molecular weight polyethylene A3.

[0117] The intrinsic viscosity, viscosity-average molecular weight, content of chain segment A, content of branch chain B, Ti content, Al content, Cl content, and molecular chain entanglement density of the ultra-high molecular weight polyethylene A3 are shown in Table 1.

[0118] Preparation Example 4

[0119] The method is the same as that of Preparation Example 1, except that the polymerization temperature in the second stage of the polymerization reaction is 90 °C and the polymerization pressure is 1.2 MPa to obtain ultra-high molecular weight polyethylene A4.

[0120] The intrinsic viscosity, viscosity-average molecular weight, content of chain segment A, content of branch chain B, Ti content, Al content, Cl content, and molecular chain entanglement density of the ultra-high molecular weight polyethylene A4 are shown in Table 1.

[0121] Preparation Example 5

[0122] In the same manner as in Preparation Example 1, except that the three reactors for the second polymerization reaction are connected in series. That is, the ethylene homopolymer obtained from the first polymerization reaction is added to the first reactor, ethylene is continuously added at a rate of 15 kg / h, and propylene is added at a rate of 0.3 kg / h. The polymerization temperature is 80 °C, the polymerization pressure is 1.5 MPa, and the polymerization time is 1.5 h. The product of the first reactor enters the second reactor, ethylene is continuously added at a rate of 15 kg / h, the polymerization temperature is 80 °C, the polymerization pressure is 1.5 MPa, and the polymerization time is 1.5 h. The product of the second reactor enters the third reactor, ethylene is continuously added at a rate of 15 kg / h, the polymerization temperature is 80 °C, the polymerization pressure is 1.5 MPa, and the polymerization time is 1.5 h. The total polymerization reaction time of the continuous reactors is 4.5 h to obtain ultra-high molecular weight polyethylene A5.

[0123] The intrinsic viscosity, viscosity-average molecular weight, content of chain segment A, content of branch chain B, Ti content, Al content, Cl content, and molecular chain entanglement density of the ultra-high molecular weight polyethylene A5 are shown in Table 1.

[0124] Preparation Example 6

[0125] In the same manner as in Preparation Example 1, except that there is only one reactor for the second polymerization reaction and the polymerization duration is 1.5 h to obtain ultra-high molecular weight polyethylene A6.

[0126] The intrinsic viscosity, viscosity-average molecular weight, content of chain segment A, content of branch chain B, Ti content, Al content, Cl content, and molecular chain entanglement density of the ultra-high molecular weight polyethylene A6 are shown in Table 1.

[0127] Preparation Example 7

[0128] In the same manner as in Preparation Example 1, except that the amount of propylene added in the second polymerization reaction is 0.5 kg / h to obtain ultra-high molecular weight polyethylene A7.

[0129] The intrinsic viscosity, viscosity-average molecular weight, content of chain segment A, content of branch chain B, Ti content, Al content, Cl content, and molecular chain entanglement density of the ultra-high molecular weight polyethylene A7 are shown in Table 1.

[0130] Preparation Example 8

[0131] In the same manner as in Preparation Example 1, except that the polymerization reaction solvent is pentane and propylene is replaced by 1-butene to obtain ultra-high molecular weight polyethylene A8.

[0132] The intrinsic viscosity, viscosity-average molecular weight, content of segment A, content of branched chain B, Ti content, Al content, Cl content, and molecular chain entanglement density of the said A8 are shown in Table 1.

[0133] Preparation Example 9

[0134] In accordance with the method of Preparation Example 1, except that the polymerization duration of the first polymerization reaction is 1 h, to obtain ultra-high molecular weight polyethylene A9.

[0135] The intrinsic viscosity, viscosity-average molecular weight, content of segment A, content of branched chain B, Ti content, Al content, Cl content, and molecular chain entanglement density of the said ultra-high molecular weight polyethylene A9 are shown in Table 1.

[0136] Preparation Example 10

[0137] In accordance with the method of Preparation Example 1, except that in the second polymerization reaction, the reaction temperature is 130 °C, to obtain ultra-high molecular weight polyethylene A10.

[0138] The intrinsic viscosity, viscosity-average molecular weight, content of segment A, content of branched chain B, Ti content, Al content, Cl content, and molecular chain entanglement density of the said A10 are shown in Table 1.

[0139] Preparation Example 11

[0140] In accordance with the method of Preparation Example 1, except that the molar ratio of the cocatalyst based on aluminum to the main catalyst based on titanium is 80:1, to obtain ultra-high molecular weight polyethylene A11.

[0141] The intrinsic viscosity, viscosity-average molecular weight, content of segment A, content of branched chain B, Ti content, Al content, Cl content, and molecular chain entanglement density of the said A11 are shown in Table 1.

[0142] Comparative Preparation Example 1

[0143] In accordance with the method of Preparation Example 1, except that both the first polymerization reaction and the second polymerization reaction have only one polymerization kettle. The product of the first polymerization kettle enters the second polymerization kettle, the polymerization temperature is 80 °C, the polymerization pressure is 1.5 MPa, ethylene is continuously added, the addition amount is 15 kg / h, and propylene is added, the addition amount is 0.3 kg / h. To obtain ultra-high molecular weight polyethylene D1.

[0144] The intrinsic viscosity, viscosity-average molecular weight, content of segment A, content of branched chain B, Ti content, Al content, Cl content, and molecular chain entanglement density of the said ultra-high molecular weight polyethylene D1 are shown in Table 1.

[0145] Comparative Preparation Example 2

[0146] In accordance with the method of Preparation Example 1, except that propylene was not added in the polymerization reaction, ultra-high molecular weight polyethylene D2 was obtained.

[0147] The intrinsic viscosity, viscosity-average molecular weight, content of chain segment A, content of branched chain B, Ti content, Al content, Cl content, and molecular chain entanglement density of the ultra-high molecular weight polyethylene D2 are shown in Table 1.

[0148] Comparative Preparation Example 3

[0149] In accordance with the method of Preparation Example 1, except that the addition amount of propylene was 1 kg / h, ultra-high molecular weight polyethylene D3 was obtained.

[0150] The intrinsic viscosity, viscosity-average molecular weight, content of chain segment A, content of branched chain B, Ti content, Al content, Cl content, and molecular chain entanglement density of D3 are shown in Table 1.

[0151] Comparative Preparation Example 4

[0152] In accordance with the method of Preparation Example 1, except that propylene was replaced with 1-octene, and as a result, the polymerization product agglomerated and the polymerization failed.

[0153] Table 1

[0154]

[0155] It can be seen from Table 1 that the ultra-high molecular weight polyethylenes A1 - A10 provided by the present invention have low element residue amounts, molecular chain entanglement densities, and high intrinsic viscosities and viscosity-average molecular weights.

[0156] Among them, in preferred Examples 1 - 4, the molecular chain entanglement density ≤ 521 mol / m 3 , and at the same time, the intrinsic viscosity ≥ 2200 g / mL, and the viscosity-average molecular weight ≥ 3.8 million.

[0157] Example 1

[0158] Take 99 wt% of the ultra-high molecular weight polyethylene A1 obtained in Preparation Example 1, add a total of 1 wt% of a mixture of tocopherol and ascorbyl palmitate (mass ratio of tocopherol to ascorbyl palmitate 1:0.5). After blending, add it to a molding press. The pretreatment conditions are: preheating temperature 190 °C, pre-pressure 10 MPa, preheating time 10 min; the molding conditions are: molding temperature 250 °C, molding pressure 20 MPa, pressure holding for 4 h; perform the first cooling, with the first cooling rate of 10 °C / min, cool to 150 °C, keep the molding pressure at 20 MPa unchanged, pressure holding for 2 h, and perform post-treatment. The condition is to cool to room temperature at a rate of 20 °C / min and then demold to obtain polyethylene resin P1.

[0159] The notched Izod impact strength and mortar wear rate of the polyethylene resin P1 are shown in Table 2.

[0160] Example 2-11

[0161] In accordance with the method of Example 1, except that Preparation Example 1 was replaced with Preparation Examples 2-11, polyethylene resins P2-P11 were prepared.

[0162] The notched Izod impact strength and mortar wear rate of the P2-P11 are shown in Table 2.

[0163] Example 12

[0164] In accordance with the method of Example 1, except that after preheating, the molding temperature was 280 °C, the pressure was 15 MPa, and the pressure holding time was 3 h, polyethylene resin P12 was obtained.

[0165] The notched Izod impact strength and mortar wear rate of the P12 are shown in Table 2.

[0166] Example 13

[0167] In accordance with the method of Example 1, except that after the first cooling, post-treatment and the second cooling were not carried out, and the product was directly demolded to obtain polyethylene resin P13.

[0168] The notched Izod impact strength and mortar wear rate of the P13 are shown in Table 2.

[0169] Example 14

[0170] In accordance with the method of Example 1, except that the amount of the ultra-high molecular weight polyethylene A1 was 100 wt%, and no antioxidant was added, polyethylene resin P14 was prepared.

[0171] The notched Izod impact strength and mortar wear rate of the P14 are shown in Table 2.

[0172] Example 15

[0173] In accordance with the method of Example 1, except that the molding pressure was replaced with 10 MPa and the pressure holding time was 1 h, polyethylene resin P15 was prepared.

[0174] The notched Izod impact strength and mortar wear rate of the P15 are shown in Table 2.

[0175] Example 16

[0176] In accordance with the method of Example 1, except that the temperature was raised to 170 °C at a rate of 10 °C / min, held for 1 h, and then cooled to room temperature at a rate of 3 °C / min and demolded to obtain polyethylene resin P16.

[0177] The notched Izod impact strength of the simply supported beam of P16 and the mortar wear rate are shown in Table 2.

[0178] Comparative Examples 1-3

[0179] In accordance with the method of Example 1, except that Preparation Example 1 was replaced with Comparative Preparation Examples 1-3, polyethylene resins DP1-DP3 were prepared.

[0180] The notched Izod impact strength of the simply supported beam of DP1-DP3 and the mortar wear rate are shown in Table 2.

[0181] Table 2

[0182]

[0183]

[0184] It can be seen from the results in Table 2 that by using the preparation methods of ultra-high molecular weight polyethylene and ultra-high molecular weight polyethylene resin provided by the present invention, Examples 1-16 obtained good technical effects. Specifically, without significantly reducing the notched Izod impact strength of the simply supported beam, the mortar wear rate ≤ 138%, and among them, the mortar wear rates of Examples 1-5 were all < 100%. Among them, in Example 11, due to the large amount of cocatalyst added, the residual amount of catalyst Cl was relatively high.

[0185] Furthermore, for Examples 1-4 that meet the preferred technical solutions of the present invention, while the mortar wear rates were all < 95%, the notched Izod impact strength of the simply supported beam did not decrease significantly, all > 170 kJ / m 2 , and the residual amounts of the catalyst were all relatively low.

[0186] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A ultra-high molecular weight polyethylene, characterized in that, The molecular chain of the ultra-high molecular weight polyethylene contains segment A and side chain B; Among them, segment A is provided by ethylene monomers, and side chain B is provided by α-olefin monomers with 3 to 6 carbon atoms; Based on the total weight of the ultra-high molecular weight polyethylene, the content of segment A is 99-99.95 wt%, and the content of side chain B is 0.05-1 wt%.

2. The ultra-high molecular weight polyethylene according to claim 1, wherein Based on the total weight of the ultra-high molecular weight polyethylene, the content of segment A is 99.3-99.8 wt%, and the content of side chain B is 0.2-0.7 wt%; Preferably, the content of Ti in the ultra-high molecular weight polyethylene is ≤30 ppm, the content of Al is ≤20 ppm, and the content of Cl is ≤30 ppm; Preferably, in the ultra-high molecular weight polyethylene, the content of Ti is ≤27 ppm, the content of Al is ≤18 ppm, and the content of Cl is ≤25 ppm; Preferably, the entanglement density of the molecular chains of the ultra-high molecular weight polyethylene is ≤ 600 mol / m 3 ; Preferably, the molecular chain entanglement density of the ultra-high molecular weight polyethylene is 300-521 mol / m 3 .

3. The ultra-high molecular weight polyethylene according to claim 1 or 2, wherein, The intrinsic viscosity of the ultra-high molecular weight polyethylene at 135 °C is 1800-3800 mL / g, preferably 2200-3200 mL / g; Preferably, the viscosity-average molecular weight of the ultra-high molecular weight polyethylene is 2.8 million - 8 million, preferably 3.8 million - 7.5 million.

4. A preparation method of ultra-high molecular weight polyethylene, characterized in that, The method includes the following steps: S1. In the presence of a solvent, mix first ethylene, a main catalyst, and a cocatalyst evenly, and carry out a first polymerization reaction to obtain an ethylene homopolymer; S2. After mixing the above ethylene homopolymer, second ethylene, and α-olefins with 3 to 6 carbon atoms, carry out a second polymerization reaction to obtain the ultra-high molecular weight polyethylene; Among them, the addition amount of the first ethylene is 1-10 kg / h; the addition amount of the second ethylene is 10-50 kg / h, and the addition amount of the α-olefins with 3 to 6 carbon atoms is 0.01-0.5 kg / h.

5. The preparation method according to claim 4, wherein, The conditions of the first polymerization reaction include: polymerization temperature 20-50 °C, polymerization pressure 0.2-2 MPa, and polymerization time 0.1-0.8 h; Preferably, the conditions of the second polymerization reaction include: polymerization temperature 30-110 °C, polymerization pressure 0.3-4 MPa, and polymerization time 0.5-4 h.

6. The preparation method according to claim 4 or 5, wherein The first polymerization reaction is a batch polymerization reaction, and the second polymerization reaction is a continuous polymerization reaction; Preferably, the first polymerization reaction includes 2-3 reaction kettles connected in parallel; Preferably, the second polymerization reaction includes 1-3 reaction kettles connected in series.

7. The preparation method according to any one of claims 4-6, wherein, The main catalyst is a Ti-containing compound, preferably titanium halide and / or Ti(OR) n X 4-n ; wherein, R is an alkyl group with 1-5 carbon atoms, n is an integer of 1-3, and X is a halogen Preferably, the cocatalyst is selected from at least one of alkyl aluminum, sesquialkyl aluminum halide, and alkyl aluminum oxane; Preferably, the mass ratio of the main catalyst to the first ethylene is 1:1×10 4 -2.5×10 4 , preferably 1:1.5×10 4 -2.2×10 4 ; Preferably, the molar ratio of the cocatalyst based on aluminum to the main catalyst based on titanium is 15-60:1, preferably 25-40:

1.

8. An ultra-high molecular weight polyethylene prepared by the preparation method according to any one of claims 4-7.

9. A polyethylene composition, characterized in that, The composition includes the ultra-high molecular weight polyethylene according to any one of claims 1-3 and 8 and an antioxidant; Based on the total weight of the composition, the dosage of the ultra-high molecular weight polyethylene is 97-99.5 wt%, and the dosage of the antioxidant is 0.5-3 wt%.

10. The polyethylene composition according to claim 9, wherein, The antioxidant contains component A and / or component B; Preferably, the component A is selected from at least one of tocopherol, tocotrienol, tocopheryl acetate, tocopheryl succinate, tocopheryl nicotinate, tocopheryl linoleate, tocopheryl phosphate, tocopheryl retinoate, and tocopheryl palmitate; Preferably, the component B is selected from ascorbyl palmitate and / or retinol; Preferably, the mass ratio of the component A to the component B is 1:0.1 - 1.

11. A method for preparing a polyethylene resin, characterized in that, The method includes: mixing the polyethylene composition according to claim 9 or 10 to obtain a mixture, and then performing molding and demolding on the mixture to obtain the polyethylene resin.

12. The method according to claim 11, wherein, The molding includes the following processes: sequentially performing pretreatment, molding treatment, first cooling, post-treatment, and second cooling on the mixture.

13. The method according to claim 12, wherein, The conditions of the pretreatment include: pretreatment temperature 150 - 210°C, pretreatment pressure 5 - 10 MPa, and pretreatment time 5 - 15 min; Preferably, the conditions of the molding treatment include: molding temperature 210 - 300°C, molding pressure 15 - 25 MPa, and holding pressure time 2 - 5 h; Preferably, the conditions of the first cooling include: cooling at a rate of 5 - 10°C / min to 130 - 180°C; Preferably, the conditions of the post-treatment include: heat preservation at 130 - 180°C for 2 - 3 h; Preferably, the conditions of the second cooling include: cooling at a rate of 10 - 20°C / min to room temperature.

14. A polyethylene resin prepared by the method according to any one of claims 11 - 13.

15. Use of the ultra-high molecular weight polyethylene according to any one of claims 1 - 3 or 8, the polyethylene composition according to claim 9 or 10, and the polyethylene resin according to claim 14 in artificial joint implant materials.

Images