Polyethylene resin for producing film material as well as preparation method and application of polyethylene resin

Abstract

The invention provides polyethylene resin for producing a film material as well as a preparation method and application of the polyethylene resin. The polyethylene resin has multimodal molecular weight distribution, the weight-average molecular weight is larger than or equal to 290000 g / mol, the molecular weight distribution is 28-40, the resin density is 0.950-0.956 g / cm < 3 >, and the melt index under the load of 5.0 kg is 0.15-0.35 g / 10 min. The multimodal polyethylene resin is obtained by polymerizing ethylene homopolymerization and copolymerization in more than two series reaction stages in the presence of a Ziegler-Natta catalyst system. The multimodal polyethylene resin has excellent mechanical properties, fewer fish eyes and excellent falling dart impact strength, and is suitable for preparing blow-molded film material products.

Description

Technical Field

[0001] This invention relates to a multimodal polyethylene resin, and more particularly to a multimodal polyethylene resin prepared using a Ziegler-Natta catalyst for producing film materials with excellent mechanical properties and few fisheyes, as well as its preparation method and applications. Background Technology

[0002] High-density polyethylene (HDPE) film possesses excellent chemical stability, impermeability, and resistance to environmental stress cracking. It also boasts high mechanical properties and good processability, exhibiting toughness at both high and low temperatures and the ability to be thinned. It is widely used in shopping bags, garbage bags, and food packaging. However, when using Ziegler-Natta catalysts to produce HDPE film, issues arise such as low catalyst activity, leading to surface roughness, numerous fisheyes, and film breakage during extrusion molding, thus affecting the product performance of the film.

[0003] Therefore, there is still a need in the art to provide a high-density polyethylene resin with various densities and melt indices, a multi-peak molecular weight distribution, suitable for blown film applications.

[0004] To ensure that the molecular weight distribution can be adjusted more flexibly according to the performance of the product to be prepared, a polyethylene with a multi-peak molecular weight distribution has been developed. The polyethylene comprises a first ethylene polymer component having a first molecular weight, a second ethylene polymer component having a second molecular weight greater than the first molecular weight, and a third ethylene polymer component having a third molecular weight greater than the first molecular weight. Summary of the Invention

[0005] Therefore, addressing the problems existing in the prior art, this invention provides a method for directly catalyzing polymerization using a titanium-containing Ziegler-Natta catalyst in multiple reactors connected in series. Furthermore, by varying the amounts of hydrogen (a chain transfer agent) and comonomers used in the reaction, a multimodal polyethylene resin with specific melt index, molecular weight, and molecular weight distribution can be prepared. The titanium-containing Ziegler-Natta catalyst of this invention exhibits high activity, and the prepared multimodal polyethylene resin possesses excellent mechanical properties. The film products prepared using this multimodal polyethylene resin have fewer fisheye defects.

[0006] One objective of this invention is to provide a polyethylene resin for producing film materials, which has a multi-peak molecular weight distribution.

[0007] The multimodal polyethylene resin for producing film materials described in this invention has excellent mechanical properties. This multimodal polyethylene resin comprises a low molecular weight fraction (homopolymer unit fraction) and a high molecular weight fraction (copolymer unit fraction), exhibiting a multimodal molecular weight distribution.

[0008] The weight-average molecular weight M of the multi-peak polyethylene resin described in this invention wGreater than or equal to 290,000 g / mol, preferably greater than or equal to 300,000 g / mol; number-average molecular weight M n Greater than or equal to 9000 g / mol, preferably greater than or equal to 10000 g / mol; its molecular weight distribution M w / M n The value is 28–40, preferably 29–38.

[0009] The polyethylene resin of the present invention has a particle size of 100μm to 500μm for 85.0wt% or more, a particle size of less than 63μm for 3.0wt% or less, and a particle size of greater than 800μm for 0.5wt% or less.

[0010] Furthermore,

[0011] The multi-peaked polyethylene resin of the present invention has a melt index of 0.15 to 0.35 g / 10 min under a load of 5.0 kg, preferably 0.19 to 0.33 g / 10 min.

[0012] The density range of the multi-peak polyethylene resin described in this invention is 0.950–0.956 g / cm³. 3 Preferably, it is 0.951–0.955 g / cm³. 3 .

[0013] According to one aspect of the technical solution of the present invention, the weight-average molecular weight of the low molecular weight fraction (i.e., the ethylene homopolymer unit fraction) of the multimodal polyethylene resin is greater than or equal to 40,000 g / mol, preferably greater than or equal to 41,000 g / mol; its molecular weight distribution M w / M n The value is 5 to 15, preferably 6 to 14; its density is greater than or equal to 0.9670 g / cm³. 3 Preferably, it is greater than or equal to 0.9675 g / cm³. 3 The melt flow index is 95–130 g / 10 min under a load of 1.2 kg, preferably 96–125 g / 10 min.

[0014] According to one aspect of the present invention, the multimodal polyethylene resin contains copolymer units derived from comonomers copolymerized with ethylene. The comonomers of the copolymer units include α-olefin monomers.

[0015] Further, the comonomer is preferably CH2=CHR; wherein R is preferably a linear or branched alkane having 1 to 10 carbon atoms; the comonomer is more preferably at least one of propylene, butene-1, pentene-1, hexene-1, octene-1, and decene-1, and most preferably at least one of hexene-1, butene-1, and octene-1.

[0016] According to one aspect of the technical solution of the present invention, the multi-peak polyethylene of the present invention has good mechanical properties and its film products have fewer fisheyes.

[0017] The tensile yield stress of the multi-peaked polyethylene resin of the present invention is greater than or equal to 21 MPa, preferably greater than or equal to 22 MPa.

[0018] The nominal tensile strain of the multi-peaked polyethylene resin of the present invention is greater than or equal to 700%, preferably greater than or equal to 710%.

[0019] The fish-eye (number per 1520cm) film product prepared from the multi-peak polyethylene resin of the present invention 3 The number of fish eyes (0.8 mm) is less than or equal to 8, preferably equal to 0; the number of fish eyes (number / 1520 cm) in the film product prepared by the multi-peak polyethylene resin is less than or equal to 8. 3 The thickness (0.4 mm) is less than or equal to 40, preferably less than or equal to 20, further preferably less than or equal to 8, and most preferably less than or equal to 4.

[0020] The dart impact strength of the film product prepared by the multi-peak polyethylene resin of the present invention is greater than or equal to 105g, preferably greater than or equal to 110g, and most preferably greater than or equal to 115g.

[0021] A second object of the present invention is to provide a method for preparing the polyethylene resin used in the production of film materials.

[0022] The method for preparing multimodal polyethylene resin according to the present invention includes a series of ethylene homopolymerization and ethylene copolymerization reactions, in the presence of a titanium-containing Ziegler-Natta catalyst system to prepare the polyethylene resin. Preferably, the method of the present invention is carried out in two or more reactors operating in series.

[0023] The series of ethylene homopolymerization and ethylene copolymerization reactions may include the following reaction stages; wherein both the ethylene homopolymerization and ethylene copolymerization reactions may be carried out in one or more stages; preferably, the ethylene homopolymerization reaction is carried out in one stage and the ethylene copolymerization reaction is carried out in two stages; more preferably, the series of ethylene homopolymerization and ethylene copolymerization reactions include one ethylene homopolymerization reaction stage and two subsequent ethylene copolymerization reaction stages.

[0024] According to one aspect of the technical solution of the present invention, the method for preparing multi-peak polyethylene resin of the present invention includes the following steps:

[0025] The first stage of ethylene homopolymerization reaction includes the homopolymerization of ethylene monomers in the presence or absence of hydrogen in the presence of a Ziegler-Natta catalyst system containing titanium, to obtain a stream containing ethylene homopolymer.

[0026] The obtained ethylene homopolymer has a weight-average molecular weight greater than or equal to 40,000 g / mol, preferably greater than or equal to 41,000 g / mol, and a molecular weight distribution of 5–15, preferably 6–14; the ethylene homopolymer has a melt index of 95–130 g / 10 min under a load of 1.2 kg, preferably 96–125 g / 10 min; and the ethylene homopolymer has a density greater than or equal to 0.9670 g / cm³. 3 Preferably, it is greater than or equal to 0.9675 g / cm³. 3 .

[0027] In the second and third stages of ethylene copolymerization, under conditions of the presence or absence of hydrogen, ethylene monomers and the stream containing ethylene homopolymer obtained in the above stages are added to the comonomer to carry out a copolymerization reaction, thereby producing an ethylene copolymer component and obtaining the multimodal polyethylene resin.

[0028] Preferably, the second stage of ethylene copolymerization involves copolymerizing the stream containing ethylene homopolymer obtained in the previous stage with ethylene monomers, comonomers, and optionally hydrogen to obtain a stream containing ethylene copolymers.

[0029] Preferably, the third stage is an ethylene copolymerization reaction: the stream containing ethylene copolymer obtained in the previous stage is further copolymerized with ethylene monomer and comonomer to obtain the polyethylene resin.

[0030] The preparation method described above includes a series of ethylene homopolymerization and ethylene copolymerization reactions. By controlling the hydrogen-to-ethylene ratio and the ethylene copolymerization conditions, two molecular weight distribution structures containing a low molecular weight portion (homogeneous portion) and a high molecular weight portion (copolymerized portion) are obtained, thereby obtaining the multi-peak polyethylene resin.

[0031] More specifically, the preparation method described in this invention:

[0032] The reaction temperature of the first stage ethylene homopolymerization reaction is 78-90℃, preferably 82-87℃; the reaction pressure is about 0.7-1.1MPa, preferably 0.80-1.0MPa.

[0033] The reaction temperature of the second-stage ethylene copolymerization reaction is 78–88°C, preferably 80–84°C; the reaction pressure is 0.08–0.30 MPa, preferably 0.1–0.25 MPa.

[0034] The reaction temperature of the third-stage ethylene copolymerization reaction is 78–90°C, preferably 80–86°C; the reaction pressure is 0.08–0.30 MPa, preferably 0.10–0.25 MPa.

[0035] Preferably, the first stage of ethylene homopolymerization is carried out in the presence of hydrogen, and the molar ratio (% / %) of hydrogen to ethylene in the ethylene homopolymerization stage is 6.5 to 7.5, more preferably 6.5 to 7.4. The hydrogen-ethylene molar ratio (% / %) described in this invention is the ratio of the molar percentage concentration of hydrogen (mol%) to the molar percentage concentration of ethylene (mol%) in actual production.

[0036] Preferably, the second-stage ethylene copolymerization reaction is carried out in the presence of hydrogen, and the hydrogen-ethylene molar ratio (%) in the ethylene copolymerization reaction stage is 0.01-0.15, preferably 0.03-0.09.

[0037] Preferably, the third-stage ethylene copolymerization reaction is carried out in the presence of hydrogen; the hydrogen-ethylene molar ratio (%) in the ethylene copolymerization reaction stage is 0.10-0.35, preferably 0.11-0.30.

[0038] Preferably, the molar ratio (% / %) of the comonomer to ethylene in the second-stage ethylene copolymerization reaction is 0.001 to 0.03, more preferably 0.003 to 0.02, and even more preferably 0.003 to 0.015.

[0039] Preferably, the molar ratio (% / %) of the comonomer to ethylene in the third-stage ethylene copolymerization reaction is 0.02 to 0.10, more preferably 0.03 to 0.09.

[0040] The molar ratio (%) of comonomer to ethylene described in this invention is the ratio of the molar percentage concentration (mol%) of comonomer to the molar percentage concentration (mol%) of ethylene in actual production.

[0041] The packing material of the catalyst, the flow rate of each stage, or the range of reaction time are routinely adjusted and selected according to the actual reactor load.

[0042] Preferably, the melt index of the ethylene copolymer obtained in the second stage is 0.5 to 1.1 g / 10 min under a 5.0 kg load, and more preferably 0.60 to 0.95 g / 10 min.

[0043] Preferably, the melt index of the third-stage polyethylene resin powder is 0.3 to 0.8 g / 10 min under a 5.0 kg load, and more preferably 0.35 to 0.65 g / 10 min.

[0044] In the preparation method of multi-peak polyethylene resin described in this invention, the same catalyst system is used for the first-stage ethylene homopolymerization reaction, the second-stage ethylene copolymerization reaction, and the third-stage ethylene copolymerization reaction. Specifically, the three-stage reactor only needs to inject the catalyst during the first-stage homopolymerization reaction; the second and third-stage copolymerization reactions do not require re-injection of the catalyst.

[0045] The preparation method of the titanium-containing Ziegler-Natta catalyst system in the preparation method of the multi-peak polyethylene resin of the present invention can adopt existing methods in the prior art.

[0046] Preferably, in the preparation method of the multi-peak polyethylene resin of the present invention, the titanium-containing Ziegler-Natta catalyst system includes the following components: (1) magnesium-containing compound; (2) organophosphorus compound; (3) organoalcohol compound; (4) organoepoxide compound; (5) precipitation aid; (6) silicon-containing compound; (7) titanium-containing compound.

[0047] The titanium-containing Ziegler-Natta catalyst system of this invention involves forming a magnesium complex from a magnesium-containing compound in a solvent system containing organophosphorus compounds, organoepoxide compounds, and organoalcohol compounds. Typically, this magnesium complex is a homogeneous and transparent solution. The magnesium complex is then reacted with a precipitation aid, a silicon-containing compound, and a titanium-containing compound to form the catalyst system.

[0048] The components of the titanium-containing Ziegler-Natta catalyst system include:

[0049] The magnesium-containing compound preferably has the general formula Mg(OR1). p X 1(2-p) Magnesium-containing compounds. In the formula, R1 represents C1 to C2. 20 Saturated or unsaturated straight-chain or branched hydrocarbon groups or C3-C6 groups 20 The cyclic hydrocarbon group; X1 is a halogen, preferably chlorine, and p is an integer and 0≤p≤2.

[0050] Further, the magnesium-containing compound is preferably selected from at least one of magnesium chloride, magnesium bromide, magnesium chloromethoxy, magnesium chloroethoxy, magnesium chloroisopropoxy, magnesium chlorobutoxy, magnesium chlorooctoxy, magnesium diethoxy, magnesium dipropoxy, magnesium dibutoxy, magnesium dioctoxy, magnesium isopropoxy, magnesium butoxy, magnesium n-octoxy, and magnesium 2-ethylhexyloxy; more preferably selected from at least one of magnesium chloride, magnesium diethoxy, magnesium dipropoxy, magnesium dibutoxy, and magnesium dioctoxy; and most preferably selected from magnesium chloride and / or magnesium diethoxy.

[0051] The organophosphorus compound is preferably selected from at least one of the following: a hydrocarbon ester of orthophosphoric acid, a hydrocarbon ester of phosphorous acid, a halohydrocarbon ester of orthophosphoric acid, and a halohydrocarbon ester of phosphorous acid; more preferably selected from at least one of the following: triethyl phosphate, tributyl phosphate, triisooctyl phosphate, triphenyl phosphate, triethyl phosphite, tributyl phosphite, and di-n-butyl phosphite.

[0052] The organic epoxy compound is preferably selected from at least one of C2-C8 aliphatic olefins, C2-C8 aliphatic dienes, C2-C8 halogenated aliphatic olefins, or C2-C8 halogenated aliphatic dienes oxides, glycidyl ethers, and internal ethers; preferably selected from at least one of ethylene oxide, propylene oxide, butane oxide, butadiene oxide, butadiene dioxide, epichlorohydrin, tetrahydrofuran, methyl glycidyl ether, and diglycidyl ether; most preferably epichlorohydrin and / or tetrahydrofuran.

[0053] The organic alcohol compound is preferably a straight-chain, branched, or cycloalkyl alcohol with 1 to 10 carbon atoms or an aryl alcohol with 6 to 20 carbon atoms, wherein the hydrogen atoms in the organic alcohol compound may optionally be replaced by halogen atoms; the organic alcohol compound is more preferably selected from at least one of ethanol, propanol, butanol, 2-ethylhexanol, and glycerol; and most preferably selected from at least one of ethanol, butanol, and 2-ethylhexanol.

[0054] The solvent system for the magnesium complex may optionally contain an inert diluent, typically an aromatic or alkane compound. Aromatic compounds include benzene, toluene, xylene, monochlorobenzene, dichlorobenzene, trichlorobenzene, monochlorotoluene, and their derivatives. Alkanes include one or a mixture of straight-chain alkanes, branched alkanes, or cycloalkanes with 3 to 20 carbon atoms, such as butane, pentane, hexane, cyclohexane, heptane, etc., as long as they facilitate the dissolution of magnesium halides. The aforementioned inert diluents may be used alone or in combination.

[0055] The precipitation aid has the structure shown in formula (I):

[0056]

[0057] In formula (I), X2 is a halogen atom, and R2 and R3 are independently hydrogen, hydroxyl, amino, aldehyde, carboxyl, acyl, halogen atom, or substituted or unsubstituted C1-C2 atoms. 10 The hydrocarbon group and substituents are selected from hydroxyl, amino, aldehyde, carboxyl, acyl, halogen, and other heteroatoms. Preferably, the precipitant is at least one of a phenylsilane compound or its derivative.

[0058] According to some embodiments of the present invention, the compound in formula (I) is selected from, but not limited to, at least one of the following compounds: phenylmonofluorosilane, phenyldifluorosilane, phenyltrifluorosilane, phenylmonochlorosilane, phenyldichlorosilane, phenyltrichlorosilane, phenylmonobromosilane, phenyldibromosilane, phenyltribromosilane, phenylmonoiodosilane, phenyldiiodosilane, phenyltriiodosilane, methylphenylfluorosilane, methylphenylchlorosilane, methylphenylbromosilane, methylphenyliodosilane, dimethylphenylfluorosilane, dimethylphenylchlorosilane, dimethylphenylbromosilane, dimethylphenylbromosilane, dimethylphenylfluorosilane, dimethylphenylchloro ...chlorosilane, dimethylphenylfluorosilane, dimethylphenylchlorosilane, dimethylphenylbromosilane, dimethylphenylchlorosilane, dimethylphenylfluorosilane, dimethylphenylchlorosilane, dimethylphenylbromosilane, dimethyl Methylphenyliodosilane, methyldiphenylfluorosilane, methyldiphenylchlorosilane, methyldiphenylbromosilane, methyldiphenyliodosilane, methylethylphenylfluorosilane, methylethylphenylchlorosilane, methylethylphenylbromosilane, methylethylphenyliodosilane, methylvinylphenylchlorosilane, diethylphenylchlorosilane, methylethynylphenylchlorosilane, methyln-propylphenylchlorosilane, methylisopropylphenylchlorosilane, diisopropylphenylchlorosilane, methyl tert-butylphenylchlorosilane, divinylphenylchlorosilane, methyln-butylphenylchlorosilane, ethyln-propylphenyl methylchlorosilane, methylallylphenylchlorosilane, methyldiphenylchlorosilane, methyl-2-methylpropylphenylchlorosilane, methyl-n-pentylphenylchlorosilane, di-n-butylphenylchlorosilane, ethyldiphenylchlorosilane, methyl-n-hexylphenylchlorosilane, di-tert-butylphenylchlorosilane, methyl-4-butenylphenylchlorosilane, diisobutylphenylchlorosilane, vinylcyclopropylphenylchlorosilane, ethynyldiphenylchlorosilane, diallylphenylchlorosilane, propyldiphenylchlorosilane, triphenylchlorosilane, methylcyclohexylphenylchlorosilane, tert-butyldiphenylchlorosilane, olefin Propyl diphenylchlorosilane, n-butyl diphenylchlorosilane, methyl-1-cyclopentadienylphenylchlorosilane, methylphenyl-1-naphthylchlorosilane, methylphenyl-2-thienylchlorosilane, 4-butyl diphenylchlorosilane, ethylphenyl-1-naphthylchlorosilane, 3-methyl-1-butenyl diphenylchlorosilane, vinylphenyl-1-naphthylchlorosilane, methylphenyl-4-morpholinylchlorosilane, methylphenyl-3-benzocyclobutylchlorosilane, methylphenylhydroxychlorosilane, ethylphenylhydroxychlorosilane, phenylhydroxydichlorosilane, phenyldihydroxychlorosilane.

[0059] The silicon-containing compound is preferably an organosilicon compound without active hydrogen atoms, and its general formula is R. 4x R 5y Si(OR6) Z R4, R5, and R6 may be the same or different. R4 and R5 are hydrocarbon groups or halogens with 1 to 10 carbon atoms, respectively. R6 is a hydrocarbon group with 1 to 10 carbon atoms. x, y, and z are positive integers, 0≤x≤2, 0≤y≤2, 0≤z≤4, and x+y+z=4.

[0060] The silicon-containing compound is more preferably selected from silicon tetrachloride, silicon tetrabromide, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetra(2-ethylhexyloxy)silane, ethyltrimethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, n-propyltriethoxysilane, n-propyltrimethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, cyclopentyltrimethoxysilane, cyclopentyltriethoxysilane, and 2-methylcyclopentyl Trimethoxysilane, 2,3-dimethylcyclopentyltrimethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, tert-butyltriethoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, cyclohexyltriethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane Methoxysilane, phenyltriethoxysilane, monochlorotrimethoxysilane, monochlorotriethoxysilane, ethyltriisopropoxysilane, vinyltributoxysilane, trimethylphenoxysilane, methyltrienylpropoxysilane, vinyltriacetylsilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diisopropyldimethoxysilane, diisopropyldiethoxysilane, tert-butylmethyldimethoxysilane, tert-butylmethyldiethoxysilane, tert-pentylmethyldiethoxysilane, dicyclopentyl At least one of dimethoxysilane, dicyclopentyldiethoxysilane, methylcyclopentyldiethoxysilane, methylcyclopentyldiethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, tricyclopentylmethoxysilane, tricyclopentylethoxysilane, dicyclopentylmethylmethoxysilane, and cyclopentyldimethylmethoxysilane; preferably at least one of tetraethoxysilane, tetramethoxysilane, tetrabutoxysilane, and silicon tetrachloride; most preferably selected from tetraethoxysilane and / or silicon tetrachloride.

[0061] The titanium-containing compound preferably has the general formula Ti(OR7). a X 3b The titanium-containing compound, wherein R7 is an aliphatic hydrocarbon group or aromatic hydrocarbon group having 1 to 14 carbon atoms, X3 is a halogen, a is 0, 1 or 2, b is an integer from 1 to 4, and a+b=3 or 4; the titanium-containing compound is more preferably selected from at least one of titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, titanium tetrabutoxy, titanium tetraethoxy, titanium monochlorotriethoxy, titanium trichloride, titanium dichlorodiethoxy, and titanium trichloromonoethoxy, most preferably selected from at least one of titanium tetrachloride, titanium tetraethoxy, and titanium tetrabutoxy, and most preferably titanium tetrachloride.

[0062] The components of the titanium-containing Ziegler-Natta catalyst system of the present invention, based on each mole of magnesium compound in the magnesium complex, are as follows: silicon compound: 0.05-1 mole, preferably 0.1-0.5 mole, for example, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 mole; precipitation aid: 0.01-5 mole, preferably 0.01-3 mole, for example, 0.01, 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 mole; titanium compound: 1-15 mole, preferably 2-10 mole, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 mole.

[0063] In the solvent system for forming the magnesium complex in the titanium-containing Ziegler-Natta catalyst system of the present invention, the organic epoxy compound is 0.2 to 10 moles, preferably 0.3 to 4 moles, for example, 0.2, 0.3, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 moles per mole of magnesium compound; the organic phosphorus compound is 0.1 to 10 moles, preferably 0.2 to 4 moles, for example, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 moles per mole of magnesium compound; and the organic alcohol compound is 0.1 to 10 moles, preferably 1 to 4 moles, for example, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 moles per mole of magnesium compound.

[0064] Preferably, the titanium-containing Ziegler-Natta catalyst system of the present invention is prepared by a method comprising the following steps:

[0065] (1) Under inert gas protection, the magnesium-containing compound is dissolved in a solvent system containing the organic epoxy compound and the organic phosphorus compound to form a homogeneous solution of the magnesium complex at a dissolution temperature of 50–90°C. The organic alcohol compound is added during or after solution formation to obtain a magnesium complex reaction solution. The magnesium complex reaction solution and a precipitation aid are then reacted until the reaction is complete, typically for 0.5–6 hours, preferably 1–6 hours.

[0066] (2) The reaction solution obtained in the above steps is brought into contact with the titanium-containing compound at a temperature of -30℃ to 20℃, and the silicon-containing compound is introduced before, after, or during the reaction; the mixture is then slowly heated to 60 to 110℃, and solids gradually precipitate and form particles. The reaction is allowed to proceed until it is complete, generally for 0.5 to 10 hours, preferably 0.5 to 6 hours.

[0067] Alternatively, some of the precipitation aid can be added in step (1), and the remaining precipitation aid can be added together with the silicon-containing compound in step (2).

[0068] The process may then include: (3) removing unreacted material and solvent from the mixture (i.e., the product after the reaction in step (2)) to obtain the titanium-containing Ziegler-Natta catalyst system.

[0069] Unreacted materials and solvents can be removed using conventional methods in the prior art, such as filtration. Furthermore, it is preferable to use an inert diluent, such as hexane, to wash the reaction products to obtain the titanium-containing Ziegler-Natta catalyst system.

[0070] The multi-peak polyethylene resin of the present invention can also be used with titanium-containing Ziegler-Natta catalyst system during polymerization reaction, and a co-catalyst commonly used in ethylene polymerization reaction, such as an organoaluminum co-catalyst, can be added in the usual amount.

[0071] The method for preparing multimodal polyethylene resin of the present invention employs slurry polymerization, wherein ethylene polymerization is carried out in at least two slurry reactors connected in series. The series-connected reactors yield high-molecular-weight polyethylene (i.e., the ethylene copolymer portion) and low-molecular-weight polyethylene (i.e., the ethylene homopolymer portion) with different molecular weights, and the two types of polyethylene can be well reacted and mixed in the reactors.

[0072] The slurry polymerization medium can be any common slurry polymerization medium, including at least one of the following: isobutane, hexane, heptane, cyclohexane, naphtha, raffinate, hydrogenated gasoline, kerosene, benzene, toluene, xylene, and other saturated aliphatic hydrocarbons or aromatic hydrocarbons, etc.

[0073] Hydrogen is typically used as a molecular weight regulator to adjust the molecular weight of the final polymer.

[0074] A third objective of this invention is to provide a polyethylene resin obtained by the aforementioned preparation method.

[0075] A fourth objective of this invention is to provide a film product prepared from the polyethylene resin described herein. The film prepared from this multi-peak polyethylene resin exhibits excellent mechanical properties, including excellent nominal strain at tensile break, and effectively reduces the number of fisheyes in the prepared film, making it suitable for blow molding of film products.

[0076] The multimodal polyethylene resin for producing membrane materials described in this invention is prepared using a titanium-containing Ziegler-Natta catalyst system in multiple reactors connected in series. This catalyst system has advantages such as controllable particle size distribution, narrow particle size distribution, high catalytic activity, and excellent copolymerization performance. The multimodal polyethylene resin prepared by the titanium-based catalyst of this invention has adjustable molecular weight, good mechanical properties, and few gel points.

[0077] The multimodal polyethylene resin prepared using the titanium-containing Ziegler-Natta catalyst system of this invention has the characteristics of good particle morphology and concentrated particle size distribution, mainly concentrated in the range of 100μm to 500μm (more than 85%, preferably more than 90%, of which the particle size is in the range of 100μm to 500μm), with low fine powder content, and particles smaller than 3.0% having a particle size of less than 63μm. It also exhibits good flowability, which is beneficial for processing. Furthermore, the film material prepared from the multimodal polyethylene resin of this invention has controllable molecular weight and molecular weight distribution, resulting in excellent processing performance. The unique resin structure of the multimodal polyethylene resin of this invention gives the prepared film material excellent mechanical properties, high melt strength, and fewer fisheyes. The multimodal polyethylene resin of this invention has a melt index of 0.15 to 0.35 g / 10min, preferably 0.19 to 0.33 g / 10min, and a density of 0.950 to 0.956 g / cm³. 3 It is very suitable for preparing membrane products. Detailed Implementation

[0078] The present invention will now be described in detail with reference to the embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0079] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0080] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0081] The polymer-related data in the examples were obtained using the following test methods:

[0082] (1) Resin tensile properties: determined according to the method described in GB / T 1040.2-2006, with a test speed of 50 mm / min.

[0083] (2) Melt mass flow rate (also known as melt index, MI): Measured using a CEAST 7026 melt indexer at 190°C and a load of 1.2 kg or 5.0 kg, according to the method described in ASTM D1238-2038. For both the resin after ethylene homopolymerization and the resin after ethylene copolymerization, a normal die was used for melt index determination.

[0084] (3) Resin density: determined according to the method described in GB / T 1033.2-2010.

[0085] (4) Molecular weight (M) w M n M z ) and molecular weight distribution M w / M n All results were obtained by gel permeation chromatography (GPC). Specifically, a Polymer Laboratories PL-GPC 220 gel permeation chromatograph, connected to a Polymerchar SA IR5 infrared detector, was used. The chromatographic column consisted of three tandem PLgel 13μm Olexis columns. The solvent and mobile phase were 1,2,4-trichlorobenzene (containing 250 ppm of the antioxidant 2,6-dibutyl-p-cresol). The column temperature was 150℃, and the flow rate was 1.0 mL / min. Universal standardization was performed using PL's EasiCal PS-1 narrow-distribution polystyrene standard.

[0086] (5) Particle size distribution of resin powder: The particle size distribution of resin powder was investigated by using a German Retsch sieve analyzer.

[0087] (6) Fish eyes shall be tested according to GB / T 11115-2009.

[0088] (7) The impact strength of the dart shall be tested in accordance with the method of GB / T 9639.1-2008.

[0089] Example 1

[0090] (1) Preparation of the titanium-containing Ziegler-Natta catalyst system:

[0091] Preparation method of solid catalyst: In a reactor fully purged with high-purity nitrogen, 4.4 g of magnesium dichloride, 80 mL of toluene, 4.0 mL of epichlorohydrin, 4.0 mL of tributyl phosphate, and 6.4 mL of ethanol were added sequentially. The mixture was heated to 70 °C with stirring. After the solid completely dissolved to form a homogeneous solution, the reaction was carried out for 2 hours. Then, 1.0 mL of phenyltrichlorosilane was added dropwise. The system was cooled to -15 °C, and 50 mL of titanium tetrachloride was slowly added dropwise while stirring for 0.5 hours. Then, 3.6 mL of tetraethoxysilane was added, and the reaction was carried out for 1 hour. The temperature was slowly raised to 85 °C, and the reaction was carried out for 2 hours. Stirring was stopped, and the mixture was allowed to stand. The suspension quickly separated into layers. The supernatant was removed, and the mixture was washed four times with hexane and dried with high-purity nitrogen to obtain a titanium-containing Ziegler-Natta catalyst system with good flowability and narrow particle size distribution.

[0092] (2) Polymerization reaction:

[0093] The polymerization reaction is carried out in three slurry reactors connected in series.

[0094] The titanium-containing Ziegler-Natta catalyst system and co-catalyst (triethylaluminum) obtained above were continuously fed into the first reactor through a catalyst storage tank to complete the first stage of ethylene homopolymerization. The polymerization temperature in the first reactor was 84.1℃, and the reaction pressure was 0.91MPa. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a diluent. The ethylene addition rate was 13.22 t / h, and the hydrogen addition rate was 26.5 kg / h, with a hydrogen / ethylene molar ratio (%) of 6.80, yielding ethylene homopolymer. The ethylene homopolymer prepared in the first reactor had a melt index of 118 g / 10 min (1.2 kg load) and a density of 0.9678 g / cm³. 3 The weight-average molecular weight is 4.28 × 10⁻⁶. 4 g / mol, with a molecular weight distribution of 8.73.

[0095] The ethylene-containing homopolymer stream from the first reactor enters the second reactor; the polymerization temperature in the second reactor is 82.0℃, and the reaction pressure is 0.143 MPa. In the feed to the second reactor, the ethylene feed rate is 12.28 t / h; the hydrogen / ethylene molar ratio (%) is 0.058; and the butene-1 / ethylene molar ratio (%) is 0.0037. The ethylene-containing copolymer stream from the second reactor enters the third reactor; the polymerization temperature in the third reactor is 82.5℃, and the reaction pressure is 0.214 MPa. In the feed to the third reactor, the ethylene feed rate is 5.2 t / h, and the butene-1 comonomer feed rate is 198.1 kg / h; the hydrogen / ethylene molar ratio (%) is 0.193; and the butene-1 / ethylene molar ratio (%) is 0.039. After the reaction in the third reactor, the multi-peak polyethylene resin obtained has a molecular weight (M). w 34.35×10 4 M n 1.06×10 4 M w / M n The melting point is 32.4; the melt index is 0.21 g / 10 min; and the density is 0.9522 g / cm³. 3 Specific test data for the basic and mechanical properties of the resin are shown in Tables 1-3.

[0096] Example 2

[0097] (1) Preparation of the titanium-containing Ziegler-Natta catalyst system:

[0098] Preparation method of solid catalyst: In a reactor fully purged with high-purity nitrogen, 4.4 g of magnesium dichloride, 80 mL of toluene, 4.0 mL of epichlorohydrin, 6.0 mL of tributyl phosphate, and 3.4 mL of ethanol were added sequentially. The mixture was heated to 65 °C with stirring. After the solid completely dissolved to form a homogeneous solution, the reaction was allowed to proceed for 1.5 hours. Then, 0.8 mL of phenyltrichlorosilane was added. The system was cooled to -10 °C, and 65 mL of titanium tetrachloride was slowly added dropwise, with stirring for 0.5 hours. Then, 4.0 mL of tetraethoxysilane was added, and the reaction was allowed to proceed for 1 hour. The temperature was slowly raised to 85 °C, and the reaction was allowed to proceed for 2 hours. Stirring was stopped, and the mixture was allowed to stand. The suspension quickly separated into layers. The supernatant was removed, and the mixture was washed four times with hexane and dried with high-purity nitrogen to obtain a titanium-containing Ziegler-Natta catalyst system with good flowability and narrow particle size distribution.

[0099] (2) Polymerization reaction:

[0100] The polymerization reaction is carried out in three slurry reactors connected in series.

[0101] The titanium-containing Ziegler-Natta catalyst system and co-catalyst (triethylaluminum) obtained above were continuously fed into the first reactor through a catalyst storage tank to complete the first stage of ethylene homopolymerization. The polymerization temperature in the first reactor was 84.0℃, and the reaction pressure was 0.86MPa. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a diluent. The ethylene addition rate was 13.09 t / h, and the hydrogen addition rate was 25.98 kg / h, with a hydrogen / ethylene molar ratio (%) of 6.52, yielding ethylene homopolymer. The ethylene homopolymer prepared in the first reactor had a melt index of 103 g / 10 min (1.2 kg load) and a density of 0.967 g / cm³. 3 The weight-average molecular weight is 4.37 × 10⁻⁶. 4 g / mol, with a molecular weight distribution of 8.65.

[0102] The ethylene-containing homopolymer stream from the first reactor enters the second reactor; the polymerization temperature in the second reactor is 82.0℃, and the reaction pressure is 0.142 MPa. In the feed to the second reactor, the ethylene feed rate is 9.62 t / h; the hydrogen / ethylene molar ratio (%) is 0.063; and the butene-1 / ethylene molar ratio (%) is 0.010. The ethylene-containing copolymer stream from the second reactor enters the third reactor; the polymerization temperature in the third reactor is 81.9℃, and the reaction pressure is 0.17 MPa. In the feed to the third reactor, the ethylene feed rate is 5.72 t / h, and the butene-1 comonomer feed rate is 210.2 kg / h; the hydrogen / ethylene molar ratio (%) is 0.121; and the butene-1 / ethylene molar ratio (%) is 0.048. After the reaction in the third reactor, the multi-peak polyethylene resin obtained has a molecular weight (M). w 32.41×104 M n 1.07×10 4 M w / M n The value is 30.29; the melt index is 0.22 g / 10 min; and the density is 0.9523 g / cm³. 3 Specific test data for the basic and mechanical properties of the resin are shown in Tables 1-3.

[0103] Example 3

[0104] (1) Preparation of the titanium-containing Ziegler-Natta catalyst system:

[0105] Preparation method of solid catalyst: In a reactor fully purged with high-purity nitrogen, 4.4 g of magnesium dichloride, 70 mL of toluene, 2.5 mL of epichlorohydrin, 4.0 mL of tributyl phosphate, and 6.4 mL of ethanol were added sequentially. The mixture was heated to 70 °C with stirring. After the solid completely dissolved to form a homogeneous solution, the reaction was carried out for 2 hours. Then, 0.8 mL of methylethylphenylchlorosilane was added dropwise. The system was cooled to -20 °C, and 50 mL of titanium tetrachloride was slowly added dropwise while stirring for 0.5 hours. Then, 3.0 mL of tetraethoxysilane was added, and the reaction was carried out for 1 hour. The temperature was slowly raised to 85 °C, and the reaction was carried out for 2 hours. Stirring was stopped, and the mixture was allowed to stand. The suspension quickly separated into layers. The supernatant was removed, and the mixture was washed four times with hexane and dried with high-purity nitrogen to obtain a titanium-containing Ziegler-Natta catalyst system with good flowability and narrow particle size distribution.

[0106] (2) Polymerization reaction:

[0107] The polymerization reaction is carried out in three slurry reactors connected in series.

[0108] The titanium-containing Ziegler-Natta catalyst system and co-catalyst (triethylaluminum) obtained above were continuously fed into the first reactor through a catalyst storage tank to complete the first stage of ethylene homopolymerization. The polymerization temperature in the first reactor was 84.5℃, and the reaction pressure was 0.92MPa. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a diluent. The ethylene addition rate was 13.22 t / h, and the hydrogen addition rate was 29.2 kg / h, with a hydrogen / ethylene molar ratio (%) of 7.15, yielding ethylene homopolymer. The ethylene homopolymer prepared in the first reactor had a melt index of 125 g / 10 min (1.2 kg load) and a density of 0.9677 g / cm³. 3 The weight-average molecular weight is 4.22 × 10⁻⁶. 4 g / mol, with a molecular weight distribution of 8.89.

[0109] The ethylene-containing homopolymer stream from the first reactor enters the second reactor; the polymerization temperature in the second reactor is 82.1℃, and the reaction pressure is 0.155MPa. In the feed to the second reactor, the ethylene feed rate is 12.28 t / h; the hydrogen / ethylene molar ratio (%) is 0.062; and the butene-1 / ethylene molar ratio (%) is 0.0038. The ethylene-containing copolymer stream from the second reactor enters the third reactor; the polymerization temperature in the third reactor is 82.5℃, and the reaction pressure is 0.224MPa. In the feed to the third reactor, the ethylene feed rate is 5.2 t / h, and the butene-1 comonomer feed rate is 199.5 kg / h; the hydrogen / ethylene molar ratio (%) is 0.212; and the butene-1 / ethylene molar ratio (%) is 0.041. After the reaction in the third reactor, the multi-peak polyethylene resin obtained has a molecular weight (M). w 35.58×10 4 M n 1.01×10 4 M w / M n The melting point is 35.22; the melt index is 0.22 g / 10 min; and the density is 0.9521 g / cm³. 3 Specific test data for the basic and mechanical properties of the resin are shown in Tables 1-3.

[0110] Comparative Example 1

[0111] Multimodal polyethylene resin was prepared using imported industrial catalyst Z509.

[0112] The polymerization reaction is carried out in three slurry reactors connected in series.

[0113] The titanium-containing Ziegler-Natta catalyst system and co-catalyst (triethylaluminum) obtained above were continuously fed into the first reactor through a catalyst storage tank to complete the first stage of ethylene homopolymerization. The polymerization temperature in the first reactor was 84.2℃, and the reaction pressure was 1.05MPa. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a diluent. The ethylene addition rate was 12.46 t / h, and the hydrogen addition rate was 36.0 kg / h, with a hydrogen / ethylene molar ratio (%) of 4.39, yielding ethylene homopolymer. The ethylene homopolymer prepared in the first reactor had a melt index of 103 g / 10 min (1.2 kg load) and a density of 0.967 g / cm³. 3 The weight-average molecular weight is 4.32 × 10⁻⁶. 4 g / mol, with a molecular weight distribution of 8.61.

[0114] The ethylene-containing homopolymer stream from the first reactor enters the second reactor; the polymerization temperature in the second reactor is 82.50℃, and the reaction pressure is 0.176 MPa. In the feed to the second reactor, the ethylene feed rate is 8.75 t / h; the hydrogen / ethylene molar ratio (%) is 0.037; and the butene-1 / ethylene molar ratio (%) is 0.01. The ethylene-containing copolymer stream from the second reactor enters the third reactor; the polymerization temperature in the third reactor is 84.50℃, and the reaction pressure is 0.29 MPa. In the feed to the third reactor, the ethylene feed rate is 5.38 t / h, and the butene-1 comonomer feed rate is 248 kg / h; the hydrogen / ethylene molar ratio (%) is 0.22; and the butene-1 / ethylene molar ratio (%) is 0.56. After the reaction in the third reactor, the multi-peak polyethylene resin obtained has a molecular weight (M). w 30.99×10 4 M n 1.06×10 4 M w / M n The melting point was 29.24; the melt index was 0.22 g / 10 min; and the density was 0.9524 g / cm³. 3 Specific test data for the basic and mechanical properties of the resin are shown in Tables 1-3.

[0115] Comparative Example 2

[0116] (1) Preparation of the titanium-containing Ziegler-Natta catalyst system:

[0117] Preparation method of solid catalyst: In a reactor fully purged with high-purity nitrogen, 4.4 g of magnesium dichloride, 70 mL of toluene, 2.5 mL of epichlorohydrin, 4.0 mL of tributyl phosphate, and 6.4 mL of ethanol were added sequentially. The mixture was heated to 70 °C with stirring. After the solid completely dissolved to form a homogeneous solution, the reaction was carried out for 2 hours. Then, 0.8 mL of methylethylphenylchlorosilane was added dropwise. The system was cooled to -20 °C, and 50 mL of titanium tetrachloride was slowly added dropwise while stirring for 0.5 hours. Then, 3.0 mL of tetraethoxysilane was added, and the reaction was carried out for 1 hour. The temperature was slowly raised to 85 °C, and the reaction was carried out for 2 hours. Stirring was stopped, and the mixture was allowed to stand. The suspension quickly separated into layers. The supernatant was removed, and the mixture was washed four times with hexane and dried with high-purity nitrogen to obtain a titanium-containing Ziegler-Natta catalyst system with good flowability and narrow particle size distribution.

[0118] (2) Polymerization reaction:

[0119] The polymerization reaction is carried out in three slurry reactors connected in series.

[0120] The titanium-containing Ziegler-Natta catalyst system and co-catalyst (triethylaluminum) obtained above were continuously fed into the first reactor through a catalyst storage tank to complete the first stage of ethylene homopolymerization. The polymerization temperature in the first reactor was 85.0℃, and the reaction pressure was 0.93MPa. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a diluent. The ethylene addition rate was 13.23 t / h, and the hydrogen addition rate was 33.58 kg / h, with a hydrogen / ethylene molar ratio (%) of 7.55, yielding ethylene homopolymer. The ethylene homopolymer prepared in the first reactor had a melt index of 135 g / 10 min (1.2 kg load) and a density of 0.9678 g / cm³. 3 The weight-average molecular weight is 4.20 × 10⁻⁶. 4 g / mol, with a molecular weight distribution of 9.18.

[0121] The ethylene-containing homopolymer stream from the first reactor enters the second reactor; the polymerization temperature in the second reactor is 82.2℃, and the reaction pressure is 0.158 MPa. In the feed to the second reactor, the ethylene feed rate is 12.30 t / h; the hydrogen / ethylene molar ratio (%) is 0.065; and the butene-1 / ethylene molar ratio (%) is 0.0038. The ethylene-containing copolymer stream from the second reactor enters the third reactor; the polymerization temperature in the third reactor is 82.5℃, and the reaction pressure is 0.225 MPa. In the feed to the third reactor, the ethylene feed rate is 5.22 t / h, and the butene-1 comonomer feed rate is 99.75 kg / h; the hydrogen / ethylene molar ratio (%) is 0.256; and the butene-1 / ethylene molar ratio (%) is 0.021. After the reaction in the third reactor, the multi-peak polyethylene resin obtained has a molecular weight (M). w 29.85×10 4 M n It is 0.96×10 4 M w / M n The melting point is 31.09; the melt index is 0.36 g / 10 min; and the density is 0.9560 g / cm³. 3 Specific test data for the basic and mechanical properties of the resin are shown in Tables 1-3.

[0122] Table 1. Particle size distribution of resin powder and catalyst activity

[0123]

[0124] Table 2. Basic Properties of Resins

[0125] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 <![CDATA[M n (10 4 )]]> 1.06 1.07 1.01 1.06 0.96 <![CDATA[M w (10 4 )]]> 34.35 32.41 35.58 30.99 29.85 <![CDATA[M z (10 4 )]]> 198.45 191.01 199.87 186.38 175.39 <![CDATA[M w / M n ]]> 32.40 30.29 35.22 29.24 31.09 Melt flow index (g / 10min) (5kg) 0.21 0.22 0.22 0.22 0.36 <![CDATA[Density (g / cm 3 )]]> 0.9522 0.9523 0.9521 0.9524 0.9560

[0126] Table 3. Mechanical properties of resin

[0127] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Tensile yield stress (MPa) 25.3 25.9 25.5 24.8 26.2 Elongation at break (%) 821 790 834 760 549 <![CDATA[Fish eyes, number / 1520 cm 3 0.8 mm]]> 0 0 0 12 0 <![CDATA[Fish eyes, number / 1520 cm 3 0.4 mm]]> 2 4 4 24 4 Impact intensity of the dart, g 125 118 132 110 92

[0128] As can be seen from the data in Tables 1-3, the titanium-containing Ziegler-Natta catalyst prepared by the method provided by this invention exhibits high catalytic activity in ethylene polymerization in reactions involving three or more tandem connections. Its activity is more than 50% higher than that of the reference industrial imported catalyst, and it demonstrates good copolymerization performance. It can produce multi-peak polyethylene resin with good particle morphology, fewer small particles, a concentrated polymer resin particle size distribution mainly between 100 μm and 500 μm, and good flowability. The multi-peak polyethylene resin prepared by the method provided by this invention has higher tensile elongation at break, dart impact strength, and fewer fisheyes compared to the comparative polyethylene resin, making it suitable for blow-molded film products.

Claims

1. A polyethylene resin for producing film materials, having a multi-peak molecular weight distribution; wherein the weight-average molecular weight of the polyethylene resin is greater than or equal to 290,000 g / mol, preferably greater than or equal to 300,000 g / mol; the molecular weight distribution is 28-40, preferably 29-38; wherein the particle size of the polyethylene resin is 100 μm to 500 μm for more than 85.0 wt% of the particles, less than 63 μm for less than 3.0 wt% of the particles, and greater than 800 μm for less than 0.5 wt% of the particles.

2. The polyethylene resin according to claim 1, characterized in that: The density of the polyethylene resin is 0.950–0.956 g / cm³. 3 Preferably, it is 0.951–0.955 g / cm³. 3 ; and / or, The polyethylene resin has a melt index of 0.15–0.35 g / 10 min under a 5.0 kg load, preferably 0.19–0.33 g / 10 min; and / or, The number-average molecular weight of the polyethylene resin is greater than or equal to 9000 g / mol, preferably greater than or equal to 10000 g / mol.

3. The polyethylene resin according to claim 1, characterized in that: The weight-average molecular weight of the ethylene homopolymer portion of the polyethylene resin is greater than 40,000 g / mol, preferably greater than or equal to 41,000 g / mol; and / or, The molecular weight distribution of the ethylene homopolymer portion of the polyethylene resin is 5–15, preferably 6–14; and / or, The density of the ethylene homopolymer portion of the polyethylene resin is greater than or equal to 0.9670 g / cm³. 3 Preferably, it is greater than or equal to 0.9675 g / cm³. 3 ; and / or, The melt index of the ethylene homopolymer portion of the polyethylene resin is 95–130 g / 10 min under a 1.2 kg load, preferably 96–125 g / 10 min.

4. The polyethylene resin according to claim 1, characterized in that: The polyethylene resin contains copolymer units, and the comonomers of the copolymer units include α-olefin monomers; Preferably, the comonomer has the structural formula CH2=CHR, where R is a linear or branched alkane having 1 to 10 carbon atoms; more preferably, the comonomer is at least one selected from propylene, butene-1, pentene-1, hexene-1, octene-1, and decene-1.

5. The polyethylene resin according to any one of claims 1 to 4, characterized in that: The tensile yield stress of the polyethylene resin is greater than or equal to 21 MPa, preferably greater than or equal to 22 MPa; and / or, The nominal tensile strain of the polyethylene resin is greater than or equal to 700%, preferably greater than or equal to 710%. And / or, The film product made of polyethylene resin has fish eyes (number per 1520cm). 3 (0.8mm) less than or equal to 8, preferably equal to 0; and / or, The film product made of polyethylene resin has fish eyes (number per 1520cm). 3 (0.4mm) less than or equal to 40, preferably less than or equal to 20, most preferably less than or equal to 8; and / or, The polyethylene resin-based film product has a dart impact strength greater than or equal to 105g, preferably greater than or equal to 110g, and most preferably greater than or equal to 115g.

6. A method for preparing polyethylene resin for producing film materials according to any one of claims 1 to 5, comprising preparing the polyethylene resin in the presence of a titanium-containing Ziegler-Natta catalyst system through a series of ethylene homopolymerization and ethylene copolymerization reactions.

7. The method for preparing polyethylene resin according to claim 6, characterized in that... Includes the following steps: The first stage of ethylene homopolymerization involves homopolymerizing ethylene monomers with optional hydrogen in the presence of a titanium-containing Ziegler-Natta catalyst system to obtain a stream containing ethylene homopolymer. Second stage ethylene copolymerization reaction: The stream containing ethylene homopolymer obtained in the previous stage is copolymerized together with ethylene monomers, comonomers and optional hydrogen to obtain a stream containing ethylene copolymers. The third stage is the ethylene copolymerization reaction: the stream containing ethylene copolymer obtained in the previous stage is further copolymerized with ethylene monomer and comonomer to obtain the polyethylene resin.

8. The preparation method according to claim 7, characterized in that: The reaction temperature of the first-stage ethylene homopolymerization reaction is 78–90°C, preferably 82–87°C; the reaction pressure is 0.7–1.1 MPa, preferably 0.8–1.0 MPa; and / or, The first stage of ethylene homopolymerization is carried out in the presence of hydrogen; wherein the molar ratio of hydrogen to ethylene is preferably 6.5–7.5, more preferably 6.5–7.4; and / or, The density of the ethylene homopolymer obtained from the first stage of ethylene homopolymerization is greater than or equal to 0.967 g / cm³. 3 Preferably, it is greater than or equal to 0.968 g / cm³. 3 ; and / or, The melt index of the ethylene homopolymer obtained from the first-stage ethylene homopolymerization reaction is 95–130 g / 10 min, preferably 96–125 g / 10 min, under a load of 1.2 kg; and / or, The weight-average molecular weight of the ethylene homopolymer obtained from the first-stage ethylene homopolymerization reaction is greater than or equal to 40,000 g / mol, preferably greater than or equal to 41,000 g / mol; and / or, The molecular weight distribution of the ethylene homopolymer obtained from the first stage of ethylene homopolymerization reaction is 5 to 15.

9. The preparation method according to claim 7, characterized in that: The reaction temperature for the second-stage ethylene copolymerization reaction is 78–88°C, preferably 80–84°C; the reaction pressure is 0.08–0.30 Pa, preferably 0.1–0.25 MPa; and / or, The second-stage ethylene copolymerization reaction is carried out in the presence of hydrogen; wherein the molar ratio of hydrogen to ethylene is preferably 0.01–0.15, more preferably 0.03–0.09; and / or, In the second stage of the ethylene copolymerization reaction, the molar ratio of comonomer to ethylene is 0.001–0.03, preferably 0.003–0.02; and / or, The melt index of the ethylene copolymer obtained in the second stage is 0.5 to 1.1 g / 10 min under a load of 5.0 kg, preferably 0.60 to 0.95 g / 10 min.

10. The preparation method according to claim 7, characterized in that: The reaction temperature for the third-stage ethylene copolymerization reaction is 78–90°C, preferably 80–86°C; the reaction pressure is 0.08–0.30 MPa, preferably 0.10–0.25 MPa; and / or, The third-stage ethylene copolymerization reaction is carried out in the presence of hydrogen; wherein the molar ratio of hydrogen to ethylene is preferably 0.10–0.35, more preferably 0.11–0.30; and / or, The molar ratio of comonomer to ethylene in the third-stage ethylene copolymerization reaction is 0.02–0.10, preferably 0.03–0.09; and / or, The melt flow index of the third-stage polyethylene resin powder is 0.3–0.8 g / 10 min under a 5.0 kg load, preferably 0.35–0.65 g / 10 min.

11. The preparation method according to claim 6, characterized in that: The titanium-containing Ziegler-Natta catalyst system comprises the following components: (1) a magnesium-containing compound; (2) an organophosphorus compound; (3) an organoalcohol compound; (4) an organoepoxide compound; (5) a precipitation aid; (6) a silicon-containing compound; and (7) a titanium-containing compound. The catalyst system is formed by forming a magnesium complex in a solvent system containing an organophosphorus compound, an organoepoxide compound, and an organoalcohol compound, and by reacting the magnesium complex with the precipitation aid, the silicon-containing compound, and the titanium-containing compound.

12. The preparation method according to claim 11, characterized in that: The magnesium-containing compound is selected from compounds with the general formula Mg(OR1). p X 1(2-p) Magnesium-containing compounds; where R1 is C1~C 20 Saturated or unsaturated straight-chain or branched hydrocarbon groups, C3-C 20 The cyclic hydrocarbon group; X1 is a halogen, preferably chlorine, p is an integer and 0≤p≤2; the magnesium-containing compound is preferably selected from at least one of magnesium chloride, magnesium bromide, magnesium chloromethoxy, magnesium chloroethoxy, magnesium chloroisopropoxy, magnesium chlorobutoxy, magnesium chlorooctoxy, magnesium diethoxy, magnesium dipropoxy, magnesium dibutoxy, magnesium dioctoxy, magnesium isopropoxy, magnesium butoxy, magnesium n-octoxy, and magnesium 2-ethylhexyloxy; and / or, The organophosphorus compound is selected from at least one of the following: alkyl esters of orthophosphoric acid, alkyl esters of phosphorous acid, haloalkyl esters of orthophosphoric acid, and haloalkyl esters of phosphorous acid; the organophosphorus compound is preferably selected from at least one of triethyl phosphate, tributyl phosphate, triisooctyl phosphate, triphenyl phosphate, triethyl phosphite, tributyl phosphite, and di-n-butyl phosphite; and / or, The organic epoxy compound is selected from at least one of C2-C8 aliphatic olefins, C2-C8 aliphatic dienes, C2-C8 halogenated aliphatic olefins, or oxides, glycidyl ethers, and internal ethers of C2-C8 halogenated aliphatic dienes; the organic epoxy compound is preferably selected from at least one of ethylene oxide, propylene oxide, butane oxide, butadiene oxide, butadiene dioxide, epichlorohydrin, tetrahydrofuran, methyl glycidyl ether, and diglycidyl ether; and / or, The organic alcohol compound is a straight-chain, branched, or cycloalkyl alcohol with 1 to 10 carbon atoms, or an aryl alcohol with 6 to 20 carbon atoms, wherein the hydrogen atoms in the organic alcohol compound may optionally be substituted with halogen atoms; the organic alcohol compound is preferably selected from at least one of ethanol, propanol, butanol, 2-ethylhexanol, and glycerol; and / or, The precipitation aid has the structure shown in formula (I): In formula (Ⅰ), X2 is a halogen atom, and R2 and R3 are independently hydrogen, hydroxyl, amino, aldehyde, carboxyl, acyl, halogen atom, or substituted or unsubstituted C1-C1 atoms. 10 The hydrocarbon group, with substituents selected from hydroxyl, amino, aldehyde, carboxyl, acyl, halogen, and other heteroatoms; preferably, the co-precipitant is at least one of phenylsilane compounds or their derivatives; more preferably, the co-precipitant is selected from phenylmonofluorosilane, phenyldifluorosilane, phenyltrifluorosilane, phenylmonochlorosilane, phenyldichlorosilane, phenyltrichlorosilane, phenylmonobromosilane, phenyldibromosilane, phenyltribromosilane, phenylmonoiodosilane, phenyldiiodosilane, phenyltriiodosilane, methylphenylfluorosilane, methylphenylchlorosilane, methylphenylbromosilane, methylphenyliodosilane, dimethyl Phenylacetylfluorosilane, dimethylphenylchlorosilane, dimethylphenylbromosilane, dimethylphenyliodosilane, methyldiphenylfluorosilane, methyldiphenylchlorosilane, methyldiphenylbromosilane, methyldiphenyliodosilane, methylethylphenylfluorosilane, methylethylphenylchlorosilane, methylethylphenylbromosilane, methylethylphenyliodosilane, methylvinylphenylchlorosilane, diethylphenylchlorosilane, methylethynylphenylchlorosilane, methyln-propylphenylchlorosilane, methylisopropylphenylchlorosilane, diisopropylphenylchlorosilane, methyl tert-butylphenylchlorosilane, divinylphenylchlorosilane, methyln-butyl... methyl phenylchlorosilane, ethyl n-propyl phenylchlorosilane, methyl allyl phenylchlorosilane, methyl diphenylchlorosilane, methyl-2-methylpropyl phenylchlorosilane, methyl n-pentyl phenylchlorosilane, di-n-butyl phenylchlorosilane, ethyl diphenylchlorosilane, methyl n-hexyl phenylchlorosilane, di-tert-butyl phenylchlorosilane, methyl-4-butenyl phenylchlorosilane, diisobutyl phenylchlorosilane, vinylcyclopropyl phenylchlorosilane, ethynyl diphenylchlorosilane, diallyl phenylchlorosilane, propyl diphenylchlorosilane, triphenylchlorosilane, methylcyclohexyl phenylchlorosilane, tert-butyl diphenylchlorosilane At least one of allyl diphenylchlorosilane, n-butyl diphenylchlorosilane, methyl-1-cyclopentadienylphenylchlorosilane, methylphenyl-1-naphthylchlorosilane, methylphenyl-2-thienylchlorosilane, 4-butyl diphenylchlorosilane, ethylphenyl-1-naphthylchlorosilane, 3-methyl-1-butenyl diphenylchlorosilane, vinylphenyl-1-naphthylchlorosilane, methylphenyl-4-morpholinylchlorosilane, methylphenyl-3-benzocyclobutylchlorosilane, methylphenylhydroxychlorosilane, ethylphenylhydroxychlorosilane, phenylhydroxydichlorosilane, and phenyl dihydroxychlorosilane; and / or, The silicon-containing compound is an organosilicon compound without active hydrogen atoms, and its general formula is R. 4x R 5y Si(OR6) Z R4, R5, and R6 may be the same or different. R4 and R5 are hydrocarbon groups or halogens with 1 to 10 carbon atoms, and R6 is a hydrocarbon group with 1 to 10 carbon atoms. x, y, and z are positive integers, 0 ≤ x ≤ 2, 0 ≤ y ≤ 2, 0 ≤ z ≤ 4, and x + y + z = 4. The silicon-containing compound is preferably selected from silicon tetrachloride, silicon tetrabromide, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetra(2-ethylhexyloxy)silane, ethyltrimethoxysilane, and ethyltriethoxysilane. Alkane, methyltrimethoxysilane, methyltriethoxysilane, n-propyltriethoxysilane, n-propyltrimethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, cyclopentyltrimethoxysilane, cyclopentyltriethoxysilane, 2-methylcyclopentyltrimethoxysilane, 2,3-dimethylcyclopentyltrimethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane tert-Butyltriethoxysilane, n-Butyltrimethoxysilane, n-Butyltriethoxysilane, Isobutyltrimethoxysilane, Isobutyltriethoxysilane, Cyclohexyltriethoxysilane, Cyclohexyltrimethoxysilane, Phenyltrimethoxysilane, Phenyltriethoxysilane, Monochlorotrimethoxysilane, Monochlorotriethoxysilane, Ethyltriisopropoxysilane, Vinyltributoxysilane, Trimethylphenoxysilane, Methyltrienylpropoxysilane, Vinyltriacetylsilane, Dimethyldimethoxysilane, Dimethyldiethoxysilane At least one of the following: diisopropyldimethoxysilane, diisopropyldiethoxysilane, tert-butylmethyldimethoxysilane, tert-butylmethyldiethoxysilane, tert-pentylmethyldiethoxysilane, dicyclopentyldimethoxysilane, dicyclopentyldiethoxysilane, methylcyclopentyldiethoxysilane, methylcyclopentyldimethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, tricyclopentylmethoxysilane, tricyclopentylethoxysilane, dicyclopentylmethylmethoxysilane, and cyclopentyldimethylmethoxysilane; and / or, The general formula of the titanium-containing compound is Ti(OR7). a X 3b In the formula, R7 is an aliphatic hydrocarbon group or aromatic hydrocarbon group with 1 to 14 carbon atoms, X3 is a halogen, a is 0, 1 or 2, b is an integer from 1 to 4, and a+b=3 or 4; the titanium-containing compound is preferably selected from at least one of titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, titanium tetrabutoxy, titanium tetraethoxy, titanium monochlorotriethoxy, titanium trichloride, titanium dichlorodiethoxy, and titanium trichloromonoethoxy.

13. The preparation method according to claim 11, characterized in that: The components of the titanium-containing Ziegler-Natta catalyst system, based on the amount of magnesium compound per mole in the magnesium complex, are as follows: silicon compound: 0.05–1 mole, preferably 0.1–0.5 mole; precipitation aid: 0.01–5 moles, preferably 0.01–3 moles; titanium compound: 1–15 moles, preferably 2–10 moles. In the solvent system for forming the magnesium complex in the titanium-containing Ziegler-Natta catalyst system, the organic alcohol compound is 0.1 to 10 moles per mole of magnesium compound, preferably 1 to 4 moles. The organic epoxy compound is 0.2 to 10 moles, preferably 0.3 to 4 moles; the organophosphorus compound is 0.1 to 10 moles, preferably 0.2 to 4 moles.

14. The polyethylene resin obtained by the preparation method according to any one of claims 6 to 13.

15. A film product made of polyethylene resin according to any one of claims 1 to 5 and claim 14.

Images