Linear low density polyethylene as well as preparation method and application thereof

Abstract

The invention relates to the field of polyethylene, and discloses linear low-density polyethylene as well as a preparation method and application thereof. The linear low-density polyethylene contains a structure as shown in a formula (1), R1 is C2-C20 alpha-alkylene, R2 is C1-C20 straight chain, branched chain or isomerized alkyl and is a main chain of the linear low-density polyethylene, m is an integer of 1-10, k is an integer of 0-18, n is an integer of 1-7, and the density of the linear low-density polyethylene is 0.910-0.940 g / cm < 3 >; in the linear low density polyethylene, the molar percentage content of Si atoms is 0.0001-0.1%.

Description

Technical Field

[0001] This invention relates to the field of polyethylene, and more specifically to a linear low-density polyethylene, its preparation method, and its applications. Background Technology

[0002] Polyethylene can be classified into high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and ultra-high molecular weight polyethylene (UHMWPE) according to its structure and polymerization method. LDPE obtained through free radical polymerization contains a large number of long-chain branched (LCB) and short-chain branched (SCB) structures. SCBs impart low crystallinity and good ductility to LDPE, but its hardness, stiffness, and strength are relatively poor. LCBs give LDPE good processing properties, thus LDPE products are widely used in packaging fields such as films and plastic bags. However, due to the lack of precise control in free radical polymerization, LDPE is usually a mixture with a wide molecular weight distribution and uneven branching structure, limiting its further development.

[0003] The discovery of Philips and Ziegler-Natta catalysts in the early 1950s enabled coordination polymerization of ethylene. Based on Ziegler-Natta catalysts, ethylene can be copolymerized with small amounts of α-olefins (such as 1-butene, 1-hexene, 1-octene, etc.) to produce LLDPE, which has properties very similar to LDPE, but with much lower production costs. Furthermore, the branching density of LLDPE can be adjusted to some extent by changing the concentration of α-olefin comonomers, resulting in better tensile, impact, and tensile strength.

[0004] Compared to traditional Ziegler-Natta catalysts, metallocene catalysts possess advantages such as high catalytic activity, a single active center, and uniform copolymer composition distribution, leading to their application in numerous fields including films and pipes. However, metallocene LLDPE exhibits a narrow molecular weight distribution, resulting in poor processing performance. To address this issue, the industry typically uses a blend of metallocene LLDPE and a small amount of LDPE for processing. This leverages the long-chain branched structure of LDPE to increase the degree of entanglement between macromolecules in the molten state, thereby improving the resin's melt processing performance. However, on the other hand, LDPE also contains a large number of short-chain branched structures, leading to slower crystallization rates and decreased crystallinity, making the product prone to breakage during storage, transportation, and use.

[0005] Introducing long-chain branched structures directly into metallocene polyethylene can effectively improve its processing performance and avoid other problems introduced by blending LDPE.

[0006] Currently, there are four main approaches to introducing long-chain branched structures into metallocene polyethylene: (1) post-modification; (2) hydrogenation modification of unsaturated compounds; (3) catalytic polymerization; and (4) bifunctional comonomer branching agent method. Among them, the post-modification method mainly obtains polyethylene with long-chain branched or cross-linked structures through high-energy ray irradiation or melt grafting. It can also control the degree of branching and melt strength, but there are still many difficulties in engineering technology and the production cost is high. In addition, the hydrogenation modification of unsaturated compounds currently mainly uses hydrogenation modification of polybutadiene, but the cost of polybutadiene modification is too high and cannot be realized in conventional polyolefin plants. In the catalytic polymerization method, some metallocene catalysts can generate vinyl macromonomers through β-H elimination. The newly inserted in-situ copolymerization yields long-chain branched polyethylene, but the degree of branching is low, and it cannot directly achieve good improvement in mechanical properties. In addition, the bifunctional comonomer branching agent method generally uses non-conjugated -α,ω-dienes (such as 1,5-hexadiene, 1,7-octadiene, 1,9-decadiene, etc.) as comonomers to participate in ethylene polymerization, which can effectively produce long-chain branched structures, but there are problems such as low comonomer utilization efficiency, difficulty in removal, easy intramolecular cyclization, and impact on polymer properties. Therefore, it is also difficult to apply to large-scale polyethylene production.

[0007] How to prepare linear low-density polyethylene with excellent mechanical and optical properties, while significantly improving its melt strength and other processing properties, is one of the technical problems that urgently need to be solved in this field. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of poor processing performance of linear low-density polyethylene in the prior art, and to provide a low-density polyethylene, its preparation method and application, which simultaneously possesses excellent melt processing performance, optical properties and mechanical properties.

[0009] To achieve the above objectives, the present invention provides a linear low-density polyethylene, wherein the linear low-density polyethylene contains the structure shown in formula (1).

[0010]

[0011] Wherein, R1 is a C2-C20 α-olefin group, and R2 is a C1-C20 straight-chain, branched, or isomerized alkyl group. The main chain is linear low-density polyethylene, where m is an integer from 1 to 10, k is an integer from 0 to 18, and n is an integer from 1 to 7.

[0012] The linear low-density polyethylene has a density of 0.910-0.940 g / cm³. 3 ;

[0013] In the linear low-density polyethylene, the molar percentage of Si atoms is 0.0001-1‰.

[0014] Preferably, R1 is a C4-C10 α-olefinic group, R2 is a C1-C8 straight-chain, branched, or isomerized alkyl group, m is an integer from 1 to 5, k is an integer from 4 to 6, and n is an integer from 1 to 5.

[0015] Preferably, the linear low-density polyethylene has a Si atom molar percentage content of 0.1-1‰.

[0016] Preferably, the linear low-density polyethylene has a density of 0.910-0.925 g / cm³. 3 .

[0017] Preferably, the weight-average molecular weight of the low-density polyethylene is 1×10⁻⁶. 4 ~2×10 7 g / mol; more preferably 1×10 g / mol; 4 ~1×10 6 g / mol.

[0018] Preferably, the molecular weight distribution of the polyethylene is 2-20, more preferably 2-5.

[0019] Preferably, the low-density polyethylene contains 0.1-5 long branches per 10,000 carbon atoms; more preferably, it contains 1-5 long branches per 10,000 carbon atoms.

[0020] Preferably, the maximum load of the linear low-density polyethylene is 140-400N; more preferably, it is 140-350N.

[0021] Preferably, the tensile strength of the linear low-density polyethylene is 15-40 MPa; more preferably, it is 15-30 MPa.

[0022] Preferably, the elastic modulus of the linear low-density polyethylene is 50-150 MPa; more preferably, it is 60-100 MPa.

[0023] Preferably, the melt strength of the linear low-density polyethylene is 10-45 cN; more preferably, it is 10-20 cN.

[0024] Preferably, the linear low-density polyethylene has a crystallinity greater than 30%; more preferably, it has a crystallinity of 30-40%.

[0025] A second aspect of the present invention provides a method for preparing linear low-density polyethylene, wherein the method includes:

[0026] 1) In the presence of a catalyst, ethylene monomer, α-olefin and ω-olefin dihalosilanes undergo polymerization to obtain the polymerization product;

[0027] 2) The polymerization product undergoes a hydrolysis-condensation reaction.

[0028] The catalyst is a metallocene catalyst, and the amount of the α-olefin is 1-10 parts by weight relative to 100 parts by weight of ethylene monomer, and the amount of the ω-olefin dihalosilane is 0.001-5 parts by weight.

[0029] Preferably, the metallocene catalyst has a Cp x R y MX z The structure is an organometallic compound, wherein Cp is a substituted or unsubstituted cyclopentadienyl group and its derivatives; R is a structural bridge providing stereorigor between two Cp groups, preferably one or more of dimethylsilyl bridges, methyl bridges, ethyl bridges and isopropyl bridges; M is a group 4, 5 and 6 transition metal; X is a halogen or a hydrocarbon group having 120 carbon atoms; x is 1 or 2, y is 0 or 1, z is 2 or 3, and the sum of x and z is equal to the oxidation state of the transition metal.

[0030] Preferably, the metallocene catalyst is one or more of bis(2-phenyl-indenyl)zirconium dichloride, dicyclopentadienylzirconium dichloride, or tetramethylindenyl titanium trichloride.

[0031] Preferably, the ω-olefinic dihalosilane is selected from the general formula R 1 SiX2R 2 One or more of the compounds; in the general formula, R 1 An olefinic group with 220 carbon atoms and a terminal olefinic double bond, R 2 X is a straight-chain, branched, or isomerized alkyl group with 1-20 carbon atoms, and X is a halogen.

[0032] Preferably, the ω-olefinic dihalosilane is selected from 1,1-dodecenylmethyldichlorosilane, 1,1-dodecenylethyldichlorosilane, 1,1-dodecenyldichlorosilane, etc. The following are one or more of the following: dodecenylisopropyldichlorosilane, 9-decenylmethyldichlorosilane, 9-decenylethyldichlorosilane, 9-decenylbutyldichlorosilane, 8-nonenylmethyldichlorosilane, 8-nonenylethyldichlorosilane, 7-octenylmethyldichlorosilane, 7-octenylethyldichlorosilane, 7-octenyloctyldichlorosilane, 6-heptenylmethyldichlorosilane, 6-heptenylethyldichlorosilane, 5-hexenylmethyldichlorosilane, 5-hexenylethyldichlorosilane, 4-pentenylmethyldichlorosilane, 4-pentenylethyldichlorosilane, 3-butenylmethyldichlorosilane, 3-butenylethyldichlorosilane, 7-octenyloctyldichlorosilane, 5-hexenylcyclohexyldichlorosilane, and 5-hexenylhexyldichlorosilane.

[0033] Preferably, the α-olefin has 3-10 carbon atoms, more preferably 4-8.

[0034] Preferably, the α-olefin is selected from one or more of 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene.

[0035] Preferably, the polymerization reaction in step 1) is carried out in the presence of a co-catalyst.

[0036] Preferably, the cocatalyst is selected from one or more alkylaluminoxane compounds or organoborides.

[0037] Preferably, the polymerization reaction in step 1) is carried out in the presence of hydrogen gas;

[0038] Preferably, the amount of hydrogen used is 10 parts by weight or less relative to 100 parts by weight of ethylene monomer.

[0039] Preferably, in step 1), the conditions for the polymerization reaction include: a temperature of 0-100℃, a time of 0.05-5h, and a pressure of 0.1-1MPa.

[0040] Preferably, the conditions for the hydrolysis-condensation reaction include: a temperature of 50-120°C and a time of 0.2-12 h.

[0041] The third aspect of the present invention provides linear low-density polyethylene prepared by the method described in the second aspect of the present invention.

[0042] The fourth aspect of the present invention provides the use of the linear low-density polyethylene described in the first and / or third aspects of the present invention as an extrusion foaming material or in film manufacturing.

[0043] Through the above technical solution, the linear low-density polyethylene provided by the present invention has an H-type long-chain branched structure, which can effectively improve the melt processing performance of polyethylene, thereby exhibiting strong fluidity in subsequent extrusion and injection molding processes, making it easy to process, and the prepared product has a smooth surface without defects such as bubbles and shrinkage cavities.

[0044] In addition, the linear low-density polyethylene provided by this invention also has excellent mechanical and optical properties, making it very suitable for use as an extrusion foaming raw material or for film manufacturing.

[0045] On the other hand, in the above-mentioned method for preparing linear low-density polyethylene provided by the present invention, a metallocene catalyst is first used to catalyze the polymerization reaction of ethylene monomer, α-olefin and ω-olefin dihalosilane. The monomer utilization rate is high and the polymerization performance is excellent during the polymerization process. Subsequently, a hydrolysis-condensation reaction is carried out to hydrolyze the hydrolyzable groups bonded to halogen atoms into silanols, which are then further condensed into siloxanes, thereby realizing the generation of long-chain branched structures. Moreover, the method of the present invention only needs to introduce a small amount of ω-olefin dihalosilane to generate sufficient long-chain branching, and finally introduces H-type long-chain branched structures into the polyethylene main chain, thereby significantly improving the melt strength of polyethylene and further improving its mechanical and optical properties.

[0046] The preparation method described in this invention is simple and can be directly implemented in conventional polyethylene plants, making it highly suitable for large-scale industrial production. Attached Figure Description

[0047] Figure 1 It is the polyethylene prepared in Example 1. 1 H-NMR spectrum;

[0048] Figure 2 The polyethylene prepared in Comparative Example 1 1 H-NMR spectrum;

[0049] Figure 3 This is a comparison graph of the rheological properties of polyethylene prepared in Example 1 and Comparative Example 1.

[0050] Figure 4 The tensile rheological curves of the polyethylene prepared in Example 1 and Comparative Example 1 at 180°C are shown.

[0051] Figure 5 This is a comparison graph showing the light transmittance of polyethylene prepared in Example 1 and Comparative Example 1.

[0052] Figure 6 This is a comparison graph showing the tensile test results of polyethylene prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0053] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0054] A first aspect of the present invention provides a linear low-density polyethylene, the linear low-density polyethylene having the structure shown in formula (1).

[0055]

[0056] Wherein, R1 is a C2-C20 α-olefin group, and R2 is a C1-C20 straight-chain, branched, or isomerized alkyl group. The linear low-density polyethylene backbone is defined as follows: m is an integer from 1 to 10, k is an integer from 0 to 18, and n is an integer from 1 to 7. The molar percentage of Si atoms in the linear low-density polyethylene is 0.0001-1‰.

[0057] According to a first aspect of the present invention, the linear low-density polyethylene has an H-type long-chain branched structure in the polyethylene main chain, which not only improves the melt strength of the linear low-density polyethylene and effectively improves its processing performance, but also results in linear low-density polyethylene with high crystallinity and excellent mechanical and optical properties.

[0058] It should be understood that in the above formula (1), The structure shown is a short branch introduced into the linear low-density polyethylene chain through α-olefin. Equation (1) only schematically shows its position and quantity in the linear low-density polyethylene for ease of understanding and explanation, but its specific position and quantity are not limited by Equation (1).

[0059] Furthermore, those skilled in the art will understand that in the structure shown in formula (1) of the present invention, either the upper or lower polyethylene main chain can be used as the main chain to include... The structure shown and the other polyethylene main chain connected by this structure are branched structures (or long branches).

[0060] In this invention, the H-type long-chain branched structure is formed by the hydrolytic condensation of ω-olefinic dihalosilanes. This is achieved by further condensation of molecular chains with dihalosilanes on their side chains after hydrolysis to form silanols, resulting in a structure where -Si-O-Si- bridges connect polyethylene molecules. The method for introducing the structure shown in formula (1) will be described in detail in the second aspect of this invention and will not be repeated here.

[0061] In this invention, R1 is a C2-C20 α-olefin group. Specific examples of the C2-C20 α-olefin group include, but are not limited to, vinyl, propenyl, 1-butenyl, 1-pentenyl, 1-hexenyl, 1-heptenyl, 1-octenyl, 1-nonenyl, 1-decenyl, 1-undecenyl, 1-dodecenyl, 1-tetrenyl, 1-tetradecenyl, 1-pentadecenyl, 1-hexadecenyl, 1-heptadecenyl, 1-heptadecenyl, 1-octadecenyl, 1-nonadecenyl, and 1-eicoseneyl.

[0062] According to a preferred embodiment of the present invention, in the structure shown in formula (1), R1 is an α-olefin group of C4-C20, more preferably an α-olefin group of C4-C15, and even more preferably an α-olefin group of C4-C12.

[0063] In a particularly preferred embodiment of the invention, R1 is selected from 1-hexenyl and / or 1-octenyl.

[0064] In this invention, R2 is a straight-chain, branched, or isomerized alkyl group of C1-C20. Specific examples of the straight-chain, branched, or isomerized alkyl groups of C1-C20 include, but are not limited to, methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, cyclohexyl, etc.

[0065] According to a preferred embodiment of the present invention, R2 is a straight-chain, branched, or isomerized alkyl group of C1-C10, more preferably a straight-chain, branched, or isomerized alkyl group of C1-C6; further preferably a straight-chain, branched, or isomerized alkyl group of C1-C3, and particularly preferably an alkyl group of C1-C2.

[0066] In a particularly preferred embodiment of the invention, R2 is selected from one or more of methyl, hexyl, cyclohexyl and octyl.

[0067] In this invention, m is an integer from 1 to 10. For example, m can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0068] In a preferred embodiment of the present invention, m is an integer from 1 to 5.

[0069] In this invention, k is an integer from 0 to 18. For example, k can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18.

[0070] In a preferred embodiment of the present invention, k is an integer between 4 and 6.

[0071] In a particularly preferred embodiment of the invention, k is 4.

[0072] In this invention, n is an integer from 1 to 7. For example, n can be 1, 2, 3, 4, 5, 6, or 7.

[0073] In a preferred embodiment of the present invention, n is an integer from 1 to 5.

[0074] According to the present invention, the molar percentage of Si atoms in the linear low-density polyethylene is preferably 0.0001-1‰, more preferably 0.1-1‰. If the molar percentage of Si atoms in the linear low-density polyethylene exceeds the above range, cross-linking may occur, making the resulting linear low-density polyethylene polymer insoluble and infusible, affecting its processing performance. Conversely, if the molar percentage of Si atoms in the linear low-density polyethylene is lower than the above range, it is insufficient to produce the long-chain branched structure described in the present invention, making it difficult to effectively improve the melt processing performance, mechanical properties, and optical properties of the obtained linear low-density polyethylene product.

[0075] In this invention, the density of the linear low-density polyethylene can be 0.910-0.940 g / cm³. 3 The preferred value is 0.910-0.925 g / cm³. 3 .

[0076] Furthermore, in this invention, the weight-average molecular weight of the linear low-density polyethylene can be 1×10⁻⁶. 4 ~2×10 7 g / mol; preferably 1×10 4 ~1×10 6 g / mol.

[0077] Furthermore, the molecular weight distribution of the polyethylene described in this invention can be, for example, 2-20, preferably 2-5.

[0078] According to the present invention, the linear low-density polyethylene contains 0.1-5 long branches per 10,000 carbon atoms; more preferably, it contains 1-5 long branches per 10,000 carbon atoms. By introducing the above-mentioned proportion of long branches, the processing performance of the resulting polyethylene product can be improved while maintaining a narrow molecular weight distribution, without causing cross-linking between polymer molecules.

[0079] In addition, as mentioned above, by including the structure shown in formula (1) in the polyethylene main chain, the mechanical and optical properties of linear low-density polyethylene can be significantly improved.

[0080] As for the aforementioned mechanical properties, all parameters, including maximum load, tensile strength, and elastic modulus, have been significantly improved and enhanced.

[0081] Specifically, the maximum load of the linear low-density polyethylene can be 140-400N; more preferably 140-350N. This ensures that the prepared polyethylene products possess excellent impact strength, maintain sufficient toughness and flexibility, and significantly extend their service life.

[0082] In this invention, the tensile strength of the linear low-density polyethylene can be 15-40 MPa; more preferably 15-30 MPa. This allows the prepared polyethylene products to exhibit excellent tensile strength in various applications, capable of withstanding large tensile and compressive forces while maintaining product integrity and safety. Such polyethylene materials are highly suitable for manufacturing films, pipes, and other products.

[0083] In this invention, the elastic modulus of the linear low-density polyethylene can be 50-150 MPa; more preferably 60-100 MPa. This results in the linear low-density polyethylene possessing excellent rigidity and resistance to deformation, leading to polyethylene products with excellent durability and resistance to deformation.

[0084] Furthermore, compared to existing linear low-density polyethylene, the linear low-density polyethylene described in the first aspect of this invention has excellent melt strength, for example, the melt strength of the linear low-density polyethylene can be 10-45 cN; more preferably 10-20 cN. This results in polyethylene possessing excellent processing and molding properties, being less prone to deformation during processing, and exhibiting excellent impact resistance.

[0085] In addition, the linear low-density polyethylene described in the first aspect of the present invention has a crystallinity greater than 30%; more preferably 30-40%.

[0086] Please refer to the following examples for the test methods of the above performance.

[0087] The linear low-density polyethylene provided in the first aspect of the present invention, by having the structure shown in formula (1), not only can the polyethylene material have excellent optical and mechanical properties, but also can significantly improve the processing performance of the material, thereby meeting the requirements for subsequent processing into a variety of products.

[0088] A second aspect of the present invention provides a method for preparing linear low-density polyethylene, the method comprising:

[0089] 1) In the presence of a catalyst, ethylene monomer, α-olefin and ω-olefin dihalosilanes undergo polymerization to obtain the polymerization product;

[0090] 2) The polymerization product undergoes a hydrolysis-condensation reaction.

[0091] The catalyst is a metallocene catalyst, and the amount of the α-olefin is 1-10 parts by weight relative to 100 parts by weight of ethylene monomer, and the amount of the ω-olefin dihalosilane is 0.001-5 parts by weight.

[0092] According to a second aspect of the present invention, a metallocene catalyst is used to polymerize ethylene monomer, α-olefin, and ω-olefin-based dihalosilane to obtain a polymerization product. Subsequently, a hydrolysis-condensation reaction is performed to generate siloxanes in the polyethylene backbone, thereby introducing a long-branched structure into the linear low-density polyethylene backbone. This method is not only simple and easy to implement, but also has a high utilization rate of ω-olefin-based dihalosilane, ultimately resulting in a structure where polyethylene molecules are linked by Si-O-Si bridging. Ultimately, not only can linear low-density polyethylene with excellent mechanical and optical properties be obtained, but the processing performance of conventional metallocene polyethylene can also be effectively improved.

[0093] The preparation method of linear low-density polyethylene according to the second aspect of the present invention will be described in detail below.

[0094] First, the ω-olefinic dihalosilane used in the second aspect of the present invention will be described.

[0095] In this invention, the ω-olefinic dihalosilane can be selected from the general formula R 1 SiX2R 2 One or more of the compounds, wherein R is a general formula. 1 R is an olefinic group with 220 carbon atoms and a terminal olefinic double bond. 2 X is a straight-chain, branched, or isomerized alkyl group having 1 to 20 carbon atoms, and X is a halogen (including fluorine, chlorine, bromine, and iodine). The two Xs in the general formula may be the same or different.

[0096] In a preferred embodiment of the present invention, the above-described general formula R, representing ω-olefinic dihalosilanes, 1 SiX2R 2 In the middle, R 1 It is a C4-20 α-olefin group, more preferably a C4-12 α-olefin group; R 2 The alkyl group is a C1 10 straight-chain branched or isomerized alkyl group, more preferably a C1 3 straight-chain branched or isomerized alkyl group; X is Cl or Br, more preferably Cl, and the two X's in the general formula can be the same or different. By selecting the above-mentioned ω-olefinic dihalosilane for polymerization, it is beneficial to further improve the melt strength of the prepared linear low-density polyethylene.

[0097] In this invention, specific examples of the ω-olefinic dihalosilane may be selected from 1,1-dodecenylmethyldichlorosilane, 1,1-dodecenylethyldichlorosilane, 1,1-dodecenyldichlorosilane, etc. The following are one or more of the following: dodecenylisopropyldichlorosilane, 9-decenylmethyldichlorosilane, 9-decenylethyldichlorosilane, 9-decenylbutyldichlorosilane, 8-nonenylmethyldichlorosilane, 8-nonenylethyldichlorosilane, 7-octenylmethyldichlorosilane, 7-octenylethyldichlorosilane, 7-octenyloctyldichlorosilane, 6-heptenylmethyldichlorosilane, 6-heptenylethyldichlorosilane, 5-hexenylmethyldichlorosilane, 5-hexenylethyldichlorosilane, 4-pentenylmethyldichlorosilane, 4-pentenylethyldichlorosilane, 3-butenylmethyldichlorosilane, 3-butenylethyldichlorosilane, 7-octenyloctyldichlorosilane, 5-hexenylcyclohexyldichlorosilane, and 5-hexenylhexyldichlorosilane.

[0098] In a preferred embodiment of the present invention, the ω-olefinic dihalosilane is selected from one or more of 5-hexenylmethyldichlorosilane, 5-hexenylethyldichlorosilane, 5-hexenylcyclohexyldichlorosilane, 7-octenylmethyldichlorosilane, and 7-octenyloctyldichlorosilane. This further improves the melt strength of the prepared polyethylene and allows the prepared polyethylene to possess both excellent mechanical and optical properties.

[0099] Next, the α-olefin used in the second aspect of the present invention will be described.

[0100] In this invention, the α-olefin refers to a monoolefin with a double bond at the end of the molecular chain, and its number of carbon atoms is not particularly limited, for example, it can be 3-10. In this invention, preferably, the number of carbon atoms of the α-olefin is 4-8.

[0101] The α-olefin described in the second aspect of the present invention may be selected, for example, from one or more of 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene. Preferably, it is selected from one or more of 1-butene, 1-hexene, and 1-octene.

[0102] In addition, in this invention, a metallocene catalyst is selected to carry out the polymerization reaction of ethylene monomer, α-olefin and ω-olefin dihalosilane, thereby introducing a long-chain branched structure as shown in formula (1) of the first aspect of this invention into polyethylene, effectively improving the processing performance of the resulting linear low-density polyethylene, while improving mechanical and optical properties.

[0103] The metallocene catalyst used in this invention will be described in detail below.

[0104] In this invention, there are no special requirements for the metallocene catalyst; various conventional metallocene catalysts in the field can be widely used.

[0105] In this invention, the metallocene catalyst can be a catalyst with Cp x R y MX z Organometallic compounds with a specific structure.

[0106] Wherein, Cp is a substituted or unsubstituted cyclopentadienyl group and its derivatives (such as indenyl or fluorenyl); the substituents on the Cp derivative are independently selected from hydrogen, C1, C2, C3, C4, C5, C6, C7, C8, C9 ... 10 Alkyl groups and 5- or 7-membered cycloalkyl groups, wherein the cycloalkyl group itself may contain a C1- or C6-membered alkyl group, or a C6- or C7-membered cycloalkyl group. 15 The aryl or aralkyl group is used as a substituent, wherein the two adjacent groups may further form an unsaturated ring of 4 to 15 carbon atoms, or Si(R)3, where R can be, for example, a C1-C10 alkyl, a C6-C15 aryl, or a C3-C10 cycloalkyl, and more specifically, for example, Ph, Bz, Naph, BzInd, Me, Et, n-Pr, iso-Pr, n-Bu, and tertiary Bu, but is not limited to these structures.

[0107] Cp x R y MX z In the structure, R is a structural bridge that provides three-dimensional rigidity between the two Cp bridges. Specifically, R can be one or more of the following: dimethylsilyl bridge, methyl bridge, ethyl bridge, and isopropyl bridge.

[0108] Cp x R y MX z In the structure, M is a transition metal of group 4, 5 and 6, specifically, for example, one or more of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum and tungsten.

[0109] Cp x R y MX z In the structure, X is a halogen or a hydrocarbon group with 120 carbon atoms.

[0110] Additionally, Cp x R y MX z In the structure, x is 1 2, y is 0 1, z is 2 3, and the sum of x + z is equal to the oxidation state of the transition metal.

[0111] On the other hand, the metallocene catalyst described in this invention can be a supported catalyst or an unsupported catalyst.

[0112] The supported type involves metallocene catalysts supported on porous inorganic supports treated with alkylaluminoxanes. Suitable examples of supports include magnesium halides, silica, alumina, aluminum silicate, or mixtures thereof. The supported metallocene catalysts are typically dispersed in an inert solvent, which can be: aliphatic hydrocarbon solvents such as hexane, heptane, and cyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; or halogenated hydrocarbon solvents such as dichloromethane and chloroform.

[0113] As a preferred embodiment of the present invention, the metallocene catalyst may include, for example, bis(2-phenyl-indenyl)zirconia, dicyclopentadienylzirconia, tetramethylindenyl titanium trichloride, ethylbis(1-indenyl)titanium dichloride, ethylbis(1-indenyl)zirconia, dimethylsilylbis(1-indenyl)zirconia, dimethylsilylbis(2,5-dimethyl-4-(2-methylphenyl)-1-indenyl)zirconia, dimethylsilylbis(1-indenyl)hafnium dichloride, dimethylsilylbis(2-methyl-4-phenyl-1-indenyl)zirconia, dimethylsilylbis(2-methyl-4-phenyl-1-indenyl)hafnium dichloride, dimethylsilylbis(2-methyl-4,5-benzoindenyl)titanium dichloride, dimethylsilylbis(2-methyl-4,5-benzoindenyl)titanium dichloride, and dimethylsilylbis(2-methyl-4,5-benzoindenyl)titanium dichloride. Benzoindyl)zirconium dichloride, di-11-methylsilylbis(2-methyl-4,6-diisopropylindyl)zirconium dichloride, dimethylsilylbis(2-ethyl-4-phenyl-1-indyl)hafnium dichloride, dimethylsilylbis(2-ethyl-4-naphthyl-1-indyl)zirconium dichloride, dimethylsilylbis(2,5-dimethyl-4-(2,5-dimethylphenyl)-1-thienocyclopentadienyl)zirconium dichloride, dimethylsilylbis(2,5-dimethyl-4-(2-methylphenyl)-1-thienocyclopentadienyl)zirconium dichloride.

[0114] Furthermore, the preparation and use methods of metallocene catalysts are well known in the art, and will not be described in detail here.

[0115] Next, the method for preparing linear low-density polyethylene according to the second aspect of the present invention will be described.

[0116] According to the present invention, in step 1), in the presence of a metallocene catalyst, ethylene monomer, α-olefin and ω-olefin dihalosilane are subjected to a polymerization reaction to obtain the polymerization product.

[0117] The amount of α-olefin used is not particularly limited and can be determined according to the amount of ethylene monomer participating in the polymerization. For example, relative to 100 parts by weight of ethylene monomer, the amount of α-olefin used can be 1-10 parts by weight, preferably 2-5 parts by weight. By controlling the amount of α-olefin within the above range, the number of short-chain branched structures introduced by the α-olefin can be controlled, thereby regulating the crystallinity of the product and improving its mechanical, optical, and other properties.

[0118] Furthermore, in this invention, the amount of ω-olefin-based dihalosilane can be determined based on the amount of ethylene monomer participating in the polymerization. For example, relative to 100 parts by weight of ethylene monomer, the amount of ω-olefin-based dihalosilane can be 0.001-5 parts by weight, preferably 0.05-0.1 parts by weight. By controlling the amount of ω-olefin-based dihalosilane within the above range, long-chain branched structures can be effectively generated (improving the melt processing performance, mechanical properties, optical properties, etc. of the product) while preventing gel formation and reducing production costs.

[0119] In this invention, there is no particular limitation on the amount of the metallocene catalyst used. For example, the amount of the metallocene catalyst relative to 100 parts by weight of ethylene monomer is 1 × 10⁻⁶. -6 ~1×10 -2 The preferred weight percentage is 1×10 -5 ~1×10 -2 Parts by weight.

[0120] Furthermore, in a preferred embodiment of the present invention, the polymerization reaction in step 1) is carried out in the presence of a co-catalyst.

[0121] In this invention, the cocatalyst may be selected from one or more of alkylaluminoxane compounds or organoborides.

[0122] The alkylaluminoxane compound is not particularly limited in this invention, and may be, for example, methylaluminoxane, modified methylaluminoxane (including modified methylaluminoxane obtained by partially substituting methyl groups of methylaluminoxane with ethyl and / or isobutyl groups; modified methylaluminoxane prepared from boron compounds, silyl ethers, and polar organic compounds containing P, N, S, or O), ethylaluminoxane, isobutylaluminoxane, tert-butylaluminoxane, etc.

[0123] The organoboronide is not particularly limited in this invention; for example, it can be B(C6F5)3 or [Ph3C]. + [B(C6F5)4] and [PhNH(Me)2] + [B(C6F5)4] At least one of them.

[0124] According to a preferred embodiment of the present invention, the cocatalyst is modified methylaluminoxane.

[0125] Furthermore, there is no particular limitation on the amount of the co-catalyst in this invention, and it can be determined based on the amount of the metallocene catalyst.

[0126] For example, when the cocatalyst is an alkylaluminoxane compound, the molar ratio of the cocatalyst (calculated as Al) to the metallocene catalyst (calculated as transition metal M) can be Al:M = 10 50000:1, preferably 100 5000:1.

[0127] For example, when the cocatalyst is an organoboronide, the molar ratio of the cocatalyst (calculated as B) to the metallocene catalyst (calculated as transition metal M) can be B:M = 0.1100:1, preferably 0.510:1.

[0128] Furthermore, in order to adjust the molecular weight of the linear low-density polyethylene and to give it better processing properties, the polymerization reaction is preferably carried out in the presence of hydrogen.

[0129] In this case, there is no particular limitation on the amount of hydrogen used. For example, relative to 100 parts by weight of the ethylene monomer, the amount of hydrogen used can be less than 10 parts by weight, preferably 0.1-1 parts by weight.

[0130] In addition, in this invention, the polymerization reaction in step 1) is preferably carried out using a slurry polymerization process.

[0131] When a slurry polymerization process is used, the polymerization reaction is carried out in the presence of an organic solvent. The organic solvent is one that does not participate in the polymerization reaction and in which the polymer formed by the polymerization reaction is insoluble.

[0132] The solvent may be, for example, a C1-C10 alkane or a C6-C8 aromatic hydrocarbon. More specifically, the solvent may be selected from one or more of n-heptane, n-hexane, cyclohexane, n-pentane, and toluene, and the present invention does not limit it.

[0133] According to the present invention, in step 1), the conditions for the polymerization reaction may include: a temperature of 0-100°C, a time of 0.05-5 h, and a pressure of 0.1-1 MPa. Preferably, the conditions for the polymerization reaction include: a temperature of 1080°C, a time of 0.14 h, and a pressure of 0.01-0.6 MPa.

[0134] In this invention, after obtaining the polymerization product through the polymerization reaction described in step 1), in step 2), the polymerization product undergoes a hydrolysis-condensation reaction, thereby further forming a long branched structure in the polyethylene main chain.

[0135] According to the present invention, in the hydrolysis-condensation reaction described in step 2), the amount of water used is excessive, as long as it is sufficient to allow the polymer to undergo sufficient hydrolysis-condensation through SiCl bonds.

[0136] Furthermore, the water can be used in the form of liquid water or in the form of water vapor; the present invention does not limit this.

[0137] According to the present invention, in step 2), the conditions for the hydrolysis-condensation reaction may include: a temperature of 50-120°C and a time of 0.2-12h; preferably, the conditions for the hydrolysis-condensation reaction include: a temperature of 70-110°C and a time of 0.25-2h.

[0138] Furthermore, according to a second aspect of the present invention, the method may further include the steps of drying and extruding granulation of the hydrolysis condensation product obtained in step 2).

[0139] The drying method is not particularly limited and can be any conventional method and condition used in the field for drying. For example, vacuum drying can be carried out at a temperature of 40-100°C, which will not be elaborated here.

[0140] Furthermore, the present invention does not impose any particular limitations on the extrusion granulation method and conditions. For example, the extrusion granulation conditions may include: a temperature of 160-200°C and an extruder speed of 10-50 r / min.

[0141] Therefore, through the second aspect of the present invention, linear low-density polyethylene can be prepared. The linear low-density polyethylene obtained thereby introduces a long-chain branched structure into the polyethylene main chain, which has excellent melt strength, as well as excellent mechanical and optical properties. For specific properties, please refer to the relevant physicochemical property parameters of the linear low-density polyethylene described in the first aspect of the present invention, which will not be repeated here.

[0142] The third aspect of the present invention provides linear low-density polyethylene prepared by the method described in the second aspect of the present invention.

[0143] Furthermore, the linear low-density polyethylene described in the third aspect of the present invention possesses the aforementioned features and properties of the linear low-density polyethylene described in the first aspect of the present invention, which will not be repeated here.

[0144] The fourth aspect of the present invention provides the use of the linear low-density polyethylene described in the first aspect of the present invention and / or the linear low-density polyethylene described in the third aspect of the present invention as an extrusion foaming material or in film manufacturing.

[0145] As described above, the linear low-density polyethylene provided by the present invention has an H-type long-chain branched structure, thereby having excellent melt strength. In addition, it has excellent mechanical and optical properties, including maximum load, tensile strength, elastic modulus and melt strength, and is therefore very suitable for use as an extrusion foaming raw material or for film manufacturing.

[0146] The present invention will be described in detail below through embodiments, but the present invention is not limited to the above embodiments.

[0147] In the following examples, the weight-average molecular weight and molecular weight distribution of polyethylene were tested using a PL220 high-temperature gel permeation chromatograph from Agilent Technologies, Inc.

[0148] The number of long-chain branches per 10,000 carbon atoms in polyethylene was determined using a Bruker AVANCE III 500WB nuclear magnetic resonance spectrometer for proton NMR spectroscopy. The molar percentage of Si atoms in the polyethylene (hereinafter referred to as Si content) was calculated by comparing the peak area ratio of the signal peak at a chemical shift of 0.23 ppm to that at chemical shifts of 1.0–1.9 ppm.

[0149] The density of polyethylene was measured using an AR124CN electronic balance equipped with a density testing function, according to the method of GB / T1033.1-2008. Ethanol was used as a reference solution. All samples were extruded into strips before testing to ensure that air bubbles in the polymer were completely removed. Each sample was tested three times and the average value was taken.

[0150] The transmittance of polyethylene was tested using a Lambda 1050+ UV-Vis-NIR spectrophotometer from Perkin Elmer, USA. The transmittance scanning wavelength range was 200–2500 nm, and the film thickness was 100 μm.

[0151] The maximum load, tensile strength, and elastic modulus of polyethylene were tested using an INSTRON 3365 universal tensile testing machine from INSTRON Corporation, USA, at a tensile rate of 50 mm / min. The tensile specimens were prepared and tested according to GB / T 1040.2 5A standard.

[0152] The melt strength of polyethylene was tested using a Goettfert Rheotens 71.97 melt strength tester. The extruder was a single-screw extruder (length-to-diameter ratio 20, outlet diameter 2mm, extruder temperature 190℃, screw speed 30rpm). The initial traction speed of the Rheotens 71.97 melt strength tester was 20mm / s, and the acceleration was 120mm / s². 2 ;

[0153] The melting temperature and crystallinity of polyethylene were tested using a differential scanning calorimeter (TA) model Q2000, according to the method in GB / T 19466-2004.

[0154] The metallocene catalyst 1 is (2-Ph-Ind)2ZrCl2 (prepared according to the method described in Ye Jianding, Preparation of Metallocene Catalyst [2-Ph-Ind]2ZrCl2 and its Catalytic Study on Ethylene / 1-Hexene Copolymerization [D], Zhejiang University, 2005).

[0155] The metallocene catalyst 2 is Cp2ZrCl2 supported on TiO2 nanotubes (prepared according to the method described in Hu Zhang, Preparation of Supported Metallocene Catalysts and Catalytic Ethylene Polymerization [D], Hunan University, 2012).

[0156] The metallocene catalyst 3 is Me4IndTiCl3 supported on spherical MgCl2 (prepared according to the method described in Li Xianzong, Preparation of Supported Monotitanium Catalysts and Their Catalytic Study on Olefin Polymerization [D], Beijing University of Chemical Technology, 2002).

[0157] Example 1

[0158] 1) Under vacuum, ethylene gas was introduced into a 2L reactor until atmospheric pressure was reached. Then, at 80°C, 1L of n-hexane, 0.0005mol of triisobutylaluminum, 0.2g of 5-hexenylmethyldichlorosilane, 15g of 1-hexene, and 100mg of metallocene catalyst 1 were added sequentially. 0.15g of hydrogen gas was introduced, followed by ethylene. The reaction was carried out at a pressure of 0.6MPa (300g of ethylene monomer was used), with the reaction temperature controlled at 80°C and the reaction time at 0.25 hours. The remaining gas in the reactor was then vented, and the polymerization product was obtained by filtration.

[0159] 2) The obtained polymerization product was subjected to hydrolysis and condensation reaction with excess 110°C steam for 20 min to obtain the hydrolysis and condensation product.

[0160] 3) The obtained hydrolysis-condensation reaction product was vacuum dried at 70°C and extruded into granules to obtain 279g of polyethylene.

[0161] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0162] In addition, the proton NMR spectrum of the polyethylene obtained in Example 1 was characterized using a Bruker AVANCE III 500WB superconducting NMR spectrometer.

[0163] Figure 1 The polyethylene prepared in Example 1 1The H-NMR spectrum showed that a signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and C=C double bond signal peaks of ω-olefin dihalosilanes that were not inserted into the polyethylene backbone but participated in hydrolysis were detected near 5.0 and 5.9 ppm. Thus, the polyethylene with the structure shown in formula (1) prepared in Example 1 can be identified.

[0164] Example 2

[0165] The procedure is carried out according to the method of Example 1, except that...

[0166] In step 1), 5-hexenylmethyldichlorosilane is replaced with the same weight of 7-octenylmethyldichlorosilane.

[0167] The final yield was 265g of polyethylene.

[0168] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0169] The polyethylene prepared in Example 2 was measured using the same method as in Example 1. 1 The H-NMR spectrum showed that a signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and C=C double bond signal peaks of ω-olefinic dihalosilanes that were not inserted into the polyethylene backbone but participated in hydrolysis were detected near 5.0 and 5.9 ppm. Thus, it can be confirmed that Example 2 also obtained polyethylene with the structure shown in formula (I).

[0170] Example 3

[0171] The procedure is carried out according to the method of Example 1, except that...

[0172] In step 1), 5-hexenylmethyldichlorosilane is replaced with the same weight of 5-hexenylhexyldichlorosilane.

[0173] The final yield was 273g of polyethylene.

[0174] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0175] The polyethylene prepared in Example 3 was measured using the same method as in Example 1. 1 The H-NMR spectrum showed that a signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and C=C double bond signal peaks of ω-olefinic dihalosilanes that were not inserted into the polyethylene backbone but participated in hydrolysis were detected near 5.0 and 5.9 ppm. Thus, it can be confirmed that Example 3 also obtained polyethylene with the structure shown in formula (I).

[0176] Example 4

[0177] The procedure is carried out according to the method of Example 1, except that...

[0178] In step 1), 5-hexenylmethyldichlorosilane is replaced with the same weight of 5-hexenylcyclohexyldichlorosilane.

[0179] The final yield was 277g of polyethylene.

[0180] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0181] The polyethylene prepared in Example 4 was measured using the same method as in Example 1. 1 The H-NMR spectrum showed that a signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and C=C double bond signal peaks of ω-olefinic dihalosilanes that were not inserted into the polyethylene backbone but participated in hydrolysis were detected near 5.0 and 5.9 ppm. Thus, it can be confirmed that Example 4 also obtained polyethylene with the structure shown in formula (I).

[0182] Example 5

[0183] The procedure is carried out according to the method of Example 1, except that...

[0184] In step 1), 5-hexenylmethyldichlorosilane is replaced with the same weight of 7-octenyloctyldichlorosilane.

[0185] The final yield was 281g of polyethylene.

[0186] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0187] The polyethylene prepared in Example 5 was measured using the same method as in Example 1. 1 The H-NMR spectrum showed that a signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and C=C double bond signal peaks of ω-olefinic dihalosilanes that were not inserted into the polyethylene backbone but participated in hydrolysis were detected near 5.0 and 5.9 ppm. Thus, it can be confirmed that Example 5 also obtained polyethylene with the structure shown in formula (I).

[0188] Example 6

[0189] The procedure is carried out according to the method of Example 1, except that...

[0190] In step 1), metallocene catalyst 1 is replaced with metallocene catalyst 2 of the same weight.

[0191] The final yield was 232g of polyethylene.

[0192] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0193] The polyethylene prepared in Example 6 was measured using the same method as in Example 1. 1 The H-NMR spectrum showed that a signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and C=C double bond signal peaks of ω-olefinic dihalosilanes that were not inserted into the polyethylene backbone but participated in hydrolysis were detected near 5.0 and 5.9 ppm. Thus, it can be confirmed that Example 6 also obtained polyethylene with the structure shown in formula (I).

[0194] Example 7

[0195] The procedure is carried out according to the method of Example 2, except that...

[0196] In step 1), metallocene catalyst 1 is replaced with metallocene catalyst 2 of the same weight.

[0197] The final yield was 237g of polyethylene.

[0198] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0199] The polyethylene prepared in Example 7 was measured using the same method as in Example 1. 1 The H-NMR spectrum showed that a signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and C=C double bond signal peaks of ω-olefinic dihalosilanes that were not inserted into the polyethylene backbone but participated in hydrolysis were detected near 5.0 and 5.9 ppm. Thus, it can be confirmed that Example 7 also obtained polyethylene with the structure shown in formula (I).

[0200] Example 8

[0201] The method described in Example 3 is followed, except that...

[0202] In step 1), metallocene catalyst 1 is replaced with metallocene catalyst 2 of the same weight.

[0203] The final yield was 217g of polyethylene.

[0204] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0205] The polyethylene prepared in Example 8 was measured using the same method as in Example 1. 1The H-NMR spectrum showed that a signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and C=C double bond signal peaks of ω-olefinic dihalosilanes that were not inserted into the polyethylene backbone but participated in hydrolysis were detected near 5.0 and 5.9 ppm. Thus, it can be confirmed that Example 8 also obtained polyethylene with the structure shown in formula (I).

[0206] Example 9

[0207] The procedure was carried out according to the method in Example 4, except that...

[0208] In step 1), metallocene catalyst 1 is replaced with metallocene catalyst 2 of the same weight.

[0209] The final yield was 241g of polyethylene.

[0210] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0211] The polyethylene prepared in Example 9 was measured using the same method as in Example 1. 1 The H-NMR spectrum showed that a signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and C=C double bond signal peaks of ω-olefinic dihalosilanes that were not inserted into the polyethylene backbone but participated in hydrolysis were detected near 5.0 and 5.9 ppm. Thus, it can be confirmed that Example 9 also obtained polyethylene with the structure shown in formula (I).

[0212] Example 10

[0213] The procedure is carried out according to the method in Example 5, except that...

[0214] In step 1), metallocene catalyst 1 is replaced with metallocene catalyst 2 of the same weight.

[0215] The final yield was 227g of polyethylene.

[0216] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0217] The polyethylene prepared in Example 10 was measured using the same method as in Example 1. 1 The H-NMR spectrum showed that a signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and C=C double bond signal peaks of ω-olefinic dihalosilanes that were not inserted into the polyethylene backbone but participated in hydrolysis were detected near 5.0 and 5.9 ppm. Thus, it can be confirmed that Example 10 also obtained polyethylene with the structure shown in formula (I).

[0218] Example 11

[0219] The procedure is carried out according to the method of Example 1, except that...

[0220] In step 1), metallocene catalyst 1 is replaced with metallocene catalyst 3 of the same weight.

[0221] The final yield was 257g of polyethylene.

[0222] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0223] The polyethylene prepared in Example 11 was measured using the same method as in Example 1. 1 The H-NMR spectrum showed that a signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and C=C double bond signal peaks of ω-olefinic dihalosilanes that were not inserted into the polyethylene backbone but participated in hydrolysis were detected near 5.0 and 5.9 ppm. Thus, it can be confirmed that Example 11 also obtained polyethylene with the structure shown in formula (I).

[0224] Comparative Example 1

[0225] The procedure is carried out according to the method of Example 1, except that...

[0226] In step 1), 5-hexenylmethyldichlorosilane was not added.

[0227] The final yield was 268g of polyethylene.

[0228] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0229] The polyethylene prepared in Comparative Example 1 was measured using the same method as in Example 1. 1 H-NMR spectrum, such as Figure 2 As shown. The results indicate that the polyethylene prepared in Comparative Example 1... 1 In the H-NMR spectrum, no signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and no signal peak of C=C double bond of ω-olefin dihalosilanes that did not insert into the polyethylene main chain but participated in hydrolysis was detected near 5.0 and 5.9 ppm, indicating that the polyethylene does not have the structure shown in formula (1).

[0230] Comparative Example 2

[0231] The procedure is carried out according to the method of Example 6, except that...

[0232] In step 1), 5-hexenylmethyldichlorosilane was not added.

[0233] The final yield was 225g of polyethylene.

[0234] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0235] The polyethylene prepared in Comparative Example 2 was measured using the same method as in Example 1. 1 H-NMR spectrum. The results show that the polyethylene prepared in Comparative Example 2... 1 In the H-NMR spectrum, no signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and no signal peak of C=C double bond of ω-olefin dihalosilanes that did not insert into the polyethylene main chain but participated in hydrolysis was detected near 5.0 and 5.9 ppm, indicating that the polyethylene does not have the structure shown in formula (1).

[0236] Comparative Example 3

[0237] The procedure is carried out according to the method of Example 11, except that...

[0238] In step 1), 5-hexenylmethyldichlorosilane was not added.

[0239] The final yield was 255g of polyethylene.

[0240] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0241] The polyethylene prepared in Comparative Example 3 was measured using the same method as in Example 1. 1 H-NMR spectrum. The results show that the polyethylene prepared in Comparative Example 3... 1 In the H-NMR spectrum, no signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and no signal peak of C=C double bond of ω-olefin dihalosilanes that did not insert into the polyethylene main chain but participated in hydrolysis was detected near 5.0 and 5.9 ppm, indicating that the polyethylene does not have the structure shown in formula (1).

[0242] Comparative Example 4

[0243] The procedure is carried out according to the method of Example 1, except that...

[0244] In step 1), 5-hexenylmethyldichlorosilane is replaced with the same weight of tetramethylsilane.

[0245] The final yield was 271g of polyethylene.

[0246] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0247] The polyethylene prepared in Comparative Example 4 was measured using the same method as in Example 1. 1 H-NMR spectrum. The results show that the polyethylene prepared in Comparative Example 4...1 In the H-NMR spectrum, no signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and no signal peak of C=C double bond of ω-olefin dihalosilanes that did not insert into the polyethylene main chain but participated in hydrolysis was detected near 5.0 and 5.9 ppm, indicating that the polyethylene does not have the structure shown in formula (1).

[0248] Comparative Example 5

[0249] The procedure is carried out according to the method of Example 1, except that...

[0250] In step 1), 5-hexenylmethyldichlorosilane is replaced with the same weight of tetrachlorosilane.

[0251] The final yield was 276g of polyethylene.

[0252] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0253] The polyethylene prepared in Comparative Example 5 was measured using the same method as in Example 1. 1 H-NMR spectrum. The results show that the polyethylene prepared in Comparative Example 5... 1 In the H-NMR spectrum, no signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and no signal peak of C=C double bond of ω-olefin dihalosilanes that did not insert into the polyethylene main chain but participated in hydrolysis was detected near 5.0 and 5.9 ppm, indicating that the polyethylene does not have the structure shown in formula (1).

[0254] Comparative Example 6

[0255] The procedure is carried out according to the method of Example 11, except that...

[0256] In step 1), 5-hexenylmethyldichlorosilane is replaced with the same weight of tetramethylsilane.

[0257] The final yield was 259g of polyethylene.

[0258] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0259] The polyethylene prepared in Comparative Example 6 was measured using the same method as in Example 1. 1 H-NMR spectrum. The results show that the polyethylene prepared in Comparative Example 6... 1In the H-NMR spectrum, no signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and no signal peak of C=C double bond of ω-olefin dihalosilanes that did not insert into the polyethylene main chain but participated in hydrolysis was detected near 5.0 and 5.9 ppm, indicating that the polyethylene does not have the structure shown in formula (1).

[0260] Comparative Example 7

[0261] The procedure is carried out according to the method of Example 11, except that...

[0262] In step 1), 5-hexenylmethyldichlorosilane is replaced with the same weight of tetrachlorosilane.

[0263] The final yield was 262g of polyethylene.

[0264] The physical and chemical properties of the polyethylene prepared above were tested, and the test results are shown in Table 1.

[0265] The polyethylene prepared in Comparative Example 7 was measured using the same method as in Example 1. 1 H-NMR spectrum. The results show that the polyethylene prepared in Comparative Example 7... 1 In the H-NMR spectrum, no signal peak of H atoms in the -Si-CH2- structure was detected at 0.23 ppm, and no signal peak of C=C double bond of ω-olefin dihalosilanes that did not insert into the polyethylene main chain but participated in hydrolysis was detected near 5.0 and 5.9 ppm, indicating that the polyethylene does not have the structure shown in formula (1).

[0266]

[0267] As shown in Table 1, various metallocene catalysts (metallocene catalysts 1, 2, and 3) can all achieve the preparation of linear low-density polyethylene as described in this invention, and all of them introduce long branches and Si atoms into the polyethylene main chain. 1 H-NMR spectroscopy confirmed the existence of the structure shown in formula (1) in the prepared polyethylene.

[0268] Furthermore, the linear low-density polyethylene prepared in the embodiments of the present invention, even with a narrow molecular weight distribution, can still have a melt strength of over 13 cN, demonstrating that it has excellent processing performance that is significantly better than the polyethylene products in the comparative examples that do not have the structure shown in formula (1) of the present invention.

[0269] Furthermore, even when using different types of metallocene catalysts, the linear low-density polyethylene prepared by the method of the present invention can achieve further improved mechanical properties such as maximum load, tensile strength, and elastic modulus, and the storage modulus is significantly improved.

[0270] Test case

[0271] Test Example 1 - Small Amplitude Oscillation Shear Rheological Properties Test

[0272] In addition, the rheological properties of the polyethylene obtained in Example 1 and Comparative Example 1 were tested using a TA AR2000 rheometer.

[0273] The test conditions were: temperature 180℃, frequency range 500~0.01rad / s, strain 3.0% (within the linear viscoelastic region), 25mm flat plate fixture, plate gap 1mm, and nitrogen protection.

[0274] The results are as follows Figure 3 As shown. By Figure 3 It can be seen that, compared with the storage modulus of Comparative Example 1, the storage modulus of Example 1 is significantly increased in the low-frequency end region, indicating that the melt processing performance of the polymer prepared by the present invention is significantly improved.

[0275] Test Example 2 - Tensile Rheological Properties Test

[0276] The tensile rheological properties of polyethylene prepared in Example 1 and Comparative Example 1 were tested using a TA ARES-G2 rotational rheometer. Specifically, an UXF rotor was used for the test, and the tensile rate was set to 1 s. -1 0.1s -1 0.01s -1 The test sample is 22mm long, 10mm wide, and 1mm thick.

[0277] The viscosity of the polyethylene prepared in Example 1 and Comparative Example 1 was plotted against time at different stretching rates, as shown in the figure. Figure 4 As shown.

[0278] Depend on Figure 4 It can be seen that the polyethylene prepared by the method of Example 1 exhibits significant melt tensile strain hardening.

[0279] Test Example 3 - Light Transmittance Test

[0280] The transmittance of polyethylene prepared in Example 1 and Comparative Example 1 was tested using a Lambda 1050+ UV-Vis-NIR spectrophotometer from Perkin Elmer, USA. Specifically, the scanning wavelength range was selected as 200-2500 nm, and the test sample was a 0.1 mm thick film. The results are as follows: Figure 5 As shown.

[0281] Depend on Figure 5 It can be seen that the polyethylene prepared in Example 1 has improved transmittance in the visible light, near-ultraviolet light, and near-infrared light wavelength ranges.

[0282] Test Example 4 - Tensile Mechanical Property Test

[0283] Using an INSTRON 3365 universal tensile testing machine from INSTRON Corporation (USA), and following the method in GB / T 1040.2, samples of polyethylene prepared in Example 1 and Comparative Example 1 were prepared and tested. The results are as follows: Figure 6 As shown.

[0284] Depend on Figure 6 It can be seen that the polyethylene obtained in Example 1 has good mechanical properties, including high maximum load, yield strength and tensile strength.

[0285] 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 inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A linear low-density polyethylene, characterized in that, The linear low-density polyethylene contains the structure shown in formula (1). Wherein, R1 is a C2-C20 α-olefin group, and R2 is a C1-C20 straight-chain, branched, or isomerized alkyl group. The main chain is linear low-density polyethylene, where m is an integer from 1 to 10, k is an integer from 0 to 18, and n is an integer from 1 to 7. The linear low-density polyethylene has a density of 0.910-0.940 g / cm³. 3 ; In the linear low-density polyethylene, the molar percentage of Si atoms is 0.0001-1‰.

2. The linear low-density polyethylene according to claim 1, wherein, R1 is an α-olefinic group of C4-C10, R2 is a straight-chain, branched or isomerized alkyl group of C1-C8, m is an integer from 1 to 5, k is an integer from 4 to 6, and n is an integer from 1 to 5. Preferably, the linear low-density polyethylene has a Si atom molar percentage content of 0.1-1‰.

3. The linear low-density polyethylene according to claim 1 or 2, wherein, The linear low-density polyethylene has a density of 0.910-0.925 g / cm³. 3 ; Preferably, the weight-average molecular weight of the low-density polyethylene is 1×10⁻⁶. 4 ~2×10 7 g / mol; more preferably 1×10 g / mol; 4 ~1×10 6 g / mol; Preferably, the molecular weight distribution of the polyethylene is 2-20, more preferably 2-5; Preferably, the low-density polyethylene contains 0.1-5 long branches per 10,000 carbon atoms; more preferably, it contains 1-5 long branches per 10,000 carbon atoms.

4. The linear low-density polyethylene according to any one of claims 1-3, wherein, The maximum load of the linear low-density polyethylene is 140-400N; more preferably 140-350N. Preferably, the tensile strength of the linear low-density polyethylene is 15-40 MPa; more preferably, it is 15-30 MPa. Preferably, the elastic modulus of the linear low-density polyethylene is 50-150 MPa; more preferably, it is 60-100 MPa. Preferably, the melt strength of the linear low-density polyethylene is 10-45 cN; more preferably, it is 10-20 cN. Preferably, the linear low-density polyethylene has a crystallinity greater than 30%; more preferably, it has a crystallinity of 30-40%.

5. A method for preparing linear low-density polyethylene, characterized in that, The method includes: 1) In the presence of a catalyst, ethylene monomer, α-olefin and ω-olefin dihalosilanes undergo polymerization to obtain the polymerization product; 2) The polymerization product undergoes a hydrolysis-condensation reaction. The catalyst is a metallocene catalyst, and the amount of the α-olefin is 1-10 parts by weight relative to 100 parts by weight of ethylene monomer, and the amount of the ω-olefin dihalosilane is 0.001-5 parts by weight.

6. The preparation method according to claim 5, wherein, The metallocene catalyst has a Cp x R y MX z Organometallic compounds with a structure Wherein, Cp is a substituted or unsubstituted cyclopentadienyl group and its derivatives; R is a three-dimensional rigid structural bridge between two Cp, preferably one or more of dimethylsilicon bridge, methyl bridge, ethyl bridge and isopropyl bridge; M is a transition metal of groups 4, 5, and 6; X is a halogen or a hydrocarbon group having 120 carbon atoms; x is 1 or 2, y is 0 or 1, z is 2 or 3, and the sum of x and z is equal to the oxidation state of the transition metal; Preferably, the metallocene catalyst is one or more of bis(2-phenyl-indenyl)zirconium dichloride, dicyclopentadienylzirconium dichloride, or tetramethylindenyl titanium trichloride.

7. The preparation method according to claim 5 or 6, wherein, The ω-olefinic dihalosilane is selected from the general formula R. 1 SiX2R 2 One or more of the compounds; In the general formula, R 1 R is an olefinic group with 220 carbon atoms and a terminal olefinic double bond. 2 X is a straight-chain, branched, or isomerized alkyl group with 120 carbon atoms, and X is a halogen. Preferably, the ω-olefinic dihalosilane is selected from 1,1-dodecenylmethyldichlorosilane, 1,1-dodecenylethyldichlorosilane, 1,1-... Dodecenylisopropyl dichlorosilane, 9-decenylmethyl dichlorosilane, 9-decenylethyl dichlorosilane, 9-decenylbutyl dichlorosilane, 8-nonenylmethyl dichlorosilane, 8-nonenylethyl dichlorosilane, 7-octenylmethyl dichlorosilane, 7-octenylethyl dichlorosilane, 7-octenyloctyl dichlorosilane, 6-heptenylmethyl dichlorosilane, 6-heptenylethyl dichlorosilane, 5-hexenylmethyl dichlorosilane, 5-hexenylethyl dichlorosilane, 4-pentenylmethyl dichlorosilane, 4-pentenylethyl dichlorosilane, 3-butenylmethyl dichlorosilane, 3-butenylethyl dichlorosilane, 7-octenyloctyl dichlorosilane, 5-hexenylcyclohexyl dichlorosilane, and 5-hexenylhexyl dichlorosilane; Preferably, the α-olefin has 3-10 carbon atoms, more preferably 4-8; Preferably, the α-olefin is selected from one or more of 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene.

8. The preparation method according to any one of claims 5-7, wherein, The polymerization reaction described in step 1) is carried out in the presence of a co-catalyst; Preferably, the cocatalyst is selected from one or more alkylaluminoxane compounds or organoborides; Preferably, the polymerization reaction in step 1) is carried out in the presence of hydrogen gas; Preferably, the amount of hydrogen used is 10 parts by weight or less relative to 100 parts by weight of ethylene monomer.

9. The method according to any one of claims 5-7, wherein, In step 1), the conditions for the polymerization reaction include: temperature of 0-100℃, time of 0.05-5h, and pressure of 0.1-1MPa; Preferably, the conditions for the hydrolysis-condensation reaction include: a temperature of 50-120°C and a time of 0.2-12 hours.

10. The linear low-density polyethylene prepared by the method of any one of claims 5-9.

11. The use of linear low-density polyethylene as described in any one of claims 1-4 and claim 10 as an extrusion foaming material or in film manufacturing.

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