Polyethylene resin composition, preparation method thereof and bottle cap product

Abstract

The invention discloses a polyethylene resin composition, a preparation method thereof and a bottle cap product, and belongs to the technical field of high polymer materials. The polyethylene resin composition provided by the invention comprises an ethylene homopolymer and an ethylene and 1-hexene copolymer, crystallization elution classification CEF results of the polyethylene resin composition comprise that F1 (70-85 DEG C) is 1-10%, and F2 (50-65 DEG C) is 1-5%; and the soluble substance distribution width index SDBI of the polyethylene resin composition is 20-30 DEG C. The polyethylene resin composition provided by the invention has a specific crystal leaching grading result and a specific soluble substance distribution width index; the specific molecular structure enables the crystallization rate of the polyethylene resin composition to be more uniform and internal stress generation to be reduced, so that the stress cracking resistance of a resin product is improved, good balance of rigidity, toughness and molding contractibility is realized, and the polyethylene resin composition is more suitable for bottle cap products.

Description

Technical Field

[0001] This application relates to the field of polymer materials technology, and more specifically, to a polyethylene resin composition, its preparation method, and a bottle cap product. Background Technology

[0002] Injection molding or compression molding can be used to manufacture plastic products with relatively complex shapes, and is particularly suitable for manufacturing bottle caps for food or beverage applications. When the polymer resin used to make bottle caps is melt-injected or compression-molded into a mold, especially in multi-channel molds, the resin needs to have high fluidity or a relatively slow crystallization and solidification rate. However, polyethylene resin, especially high-density polyethylene resin, has an extremely fast crystallization rate, which is difficult to adjust in practical applications. Therefore, the melt index of polyethylene resin can be adjusted to give the resin higher fluidity, thereby meeting the production efficiency requirements of bottle cap production during injection molding and compression molding. However, high fluidity often comes at the cost of mechanical properties. Any reduction in the fluidity of polyethylene resin will increase production time and reduce production efficiency, which is unacceptable for the fast-moving consumer goods industry. Another important property of bottle cap products is their stress crack resistance. High stress crack resistance not only reduces the possibility of mechanical or structural failure of the product during its lifespan, but also allows for thinner bottle caps, producing lightweight bottle caps, reducing raw material consumption, significantly saving costs, reducing plastic usage, and improving environmental benefits. However, increased stress crack resistance usually leads to a decrease in mechanical strength, such as tensile strength.

[0003] In existing technologies, differences in the component structures of polyethylene resin compositions lead to segregation and crystallization. This causes crystallization shrinkage and internal stress during the rapid cooling process of the injection mold, affecting the long-term stress cracking resistance and dimensional stability of the final product. Disclosed polyethylene resin compositions, in an effort to improve environmental stress cracking resistance, increase rigidity, thereby disrupting the rigidity-toughness balance of the resin composition. Alternatively, polyethylene resin compositions may improve impact resistance and stress cracking resistance by adjusting the polymer molecular weight and polymer component content, but without considering the material's processing properties and shrinkage during the molding process.

[0004] Therefore, existing technologies for injection-molded or compression-molded bottle caps do not achieve the desired balance between the material's rigidity and toughness, resistance to stress cracking, and shrinkage properties during the molding process. Summary of the Invention

[0005] The main objective of this application is to provide a polyethylene resin composition, its preparation method, and a bottle cap product, in order to solve the problem that polyethylene resin in the prior art cannot simultaneously achieve a balance between rigidity and toughness, resistance to stress cracking, and molding shrinkage performance.

[0006] To achieve the above objectives, according to one aspect of this application, a polyethylene resin composition is provided, comprising an ethylene homopolymer and an ethylene-1-hexene copolymer;

[0007] The crystallization elution fractionation (CEF) results of the polyethylene resin composition include:

[0008] F1 (70~85℃) = 1~10%, F2 (50~65℃) = 1~5%; and the soluble distribution width index SDBI of the polyethylene resin composition = 20~30℃.

[0009] Furthermore, the CEF results include: F1 (70–85℃) = 3–7%, F2 (50–65℃) = 2–4%.

[0010] Furthermore, SDBI = 23–26°C.

[0011] Furthermore, the molecular weight distribution of the polyethylene resin composition simultaneously satisfies the following conditions:

[0012] M w / M n =10~20; M z / M w ≥4.0; M z+1 / M z ≥2.0; and, lg(M) 80 ) / lg(M 50 )≥1.125,lg(M 50 ) / lg(M 20 )≥1.135.

[0013] Furthermore, M w / M n =13~16; M z / M w ≥4.5; M z+1 / M z ≥2.5; and, lg(M) 80 ) / lg(M 50 )≥1.135,lg(M 50 ) / lg(M 20 )≥1.140.

[0014] Furthermore, the content of ethylene homopolymer in the polyethylene resin composition is 45-55 wt%; the content of ethylene-1-hexene copolymer in the polyethylene resin composition is 45-55 wt%.

[0015] Furthermore, the density of the ethylene homopolymer is 0.965–0.970 g / cm³. 3 .

[0016] Furthermore, the density of the ethylene homopolymer is 0.965–0.968 g / cm³. 3 .

[0017] Furthermore, the density of the polyethylene resin composition is 0.955–0.965 g / cm³. 3 .

[0018] Furthermore, the density of the polyethylene resin composition is 0.958–0.962 g / cm³. 3 .

[0019] Furthermore, the melt flow rate of the ethylene homopolymer was 20–60 g / 10 min; the measurement conditions were: temperature 190 °C and load 2.16 kg.

[0020] Furthermore, the melt flow rate of the ethylene homopolymer was 40–55 g / 10 min; the measurement conditions were: temperature 190 °C and load 2.16 kg.

[0021] Furthermore, the melt flow rate of the polyethylene resin composition is 2.5–4.0 g / 10 min; the measurement conditions are: temperature 190 °C and load 2.16 kg.

[0022] Furthermore, the melt flow rate of the polyethylene resin composition is 2.7–3.6 g / 10 min; the measurement conditions are: temperature 190 °C and load 2.16 kg.

[0023] Furthermore, after the polyethylene resin composition has been molded and cooled for 48 hours, the molding shrinkage rate parallel to the melt flow direction is ≤2.0, and the molding shrinkage rate perpendicular to the melt flow direction is ≤0.8.

[0024] Furthermore, after the polyethylene resin composition has been molded and cooled for 48 hours, the molding shrinkage rate parallel to the melt flow direction is ≤1.5, and the molding shrinkage rate perpendicular to the melt flow direction is ≤0.6.

[0025] Furthermore, after the polyethylene resin composition has been molded and cooled for 72 hours, the molding shrinkage rate parallel to the melt flow direction is ≤2.2, and the molding shrinkage rate perpendicular to the melt flow direction is ≤1.0.

[0026] Furthermore, after the polyethylene resin composition has been molded and cooled for 72 hours, the molding shrinkage rate parallel to the melt flow direction is ≤1.8, and the molding shrinkage rate perpendicular to the melt flow direction is ≤0.8.

[0027] Furthermore, the ESCR of the polyethylene resin composition is ≥400 hours.

[0028] Furthermore, the ESCR of the polyethylene resin composition is ≥600 hours.

[0029] Furthermore, the FNCT of the polyethylene resin composition is ≥30 hours; measurement conditions: stress 4.0 MPa, temperature 80℃.

[0030] Furthermore, the FNCT of the polyethylene resin composition is ≥40 hours; measurement conditions: stress 4.0 MPa, temperature 80℃.

[0031] Furthermore, the notched impact strength of the simply supported beam of the polyethylene resin composition is ≥12.0 kJ / m. 2 .

[0032] Furthermore, the notched impact strength of the simply supported beam of the polyethylene resin composition is ≥15.0 kJ / m. 2 .

[0033] Furthermore, the tensile yield stress of the polyethylene resin composition is ≥22.0 MPa.

[0034] Furthermore, the tensile yield stress of the polyethylene resin composition is ≥25.0 MPa.

[0035] Furthermore, the nominal tensile strain at break of the polyethylene resin composition is ≥400%.

[0036] Furthermore, the nominal tensile strain at break of the polyethylene resin composition is ≥550%.

[0037] According to a second aspect of this application, a method for preparing the above-mentioned polyethylene resin composition is provided, comprising:

[0038] Step S1: Ethylene I and hydrogen I are reacted in the presence of catalyst I to obtain stream I containing ethylene homopolymer; wherein, the feed ratio of ethylene I to hydrogen I is 1 kg / h: (8.1 g / h ~ 15.0 g / h);

[0039] Step S2: Stream I, ethylene II, hydrogen II and 1-hexene are reacted in the presence of catalyst II to obtain stream II containing ethylene homopolymer and ethylene-hexene copolymer; wherein the feed ratio of ethylene II, hydrogen II and 1-hexene is 1 kg / h:(0.5 g / h~2.5 g / h):(101 g / h~200 g / h);

[0040] Step S3: Separate and dry the material II sequentially to obtain polymer powder, i.e., polyethylene resin composition.

[0041] Furthermore, in step S1, the feed ratio of ethylene I to hydrogen I is 1 kg / h:(10.0 g / h ~ 12.0 g / h).

[0042] Further, in step S2, the feed ratio of ethylene II, hydrogen II, and 1-hexene is 1 kg / h:(1.0 g / h to 2.0 g / h):(120 g / h to 180 g / h).

[0043] Furthermore, the conditions for reaction I include: a reaction temperature of 80–95°C, a reaction pressure of 1.4–2.0 MPa, and a reaction time of 10–100 min.

[0044] Furthermore, the conditions for reaction I include: a reaction temperature of 82–92 °C, a reaction pressure of 1.5–1.9 MPa, and a reaction time of 20–40 min.

[0045] Furthermore, the conditions for reaction II include: a reaction temperature of 85–100°C, a reaction pressure of 1.4–2.0 MPa, and a reaction time of 10–100 min.

[0046] Furthermore, the conditions for reaction II include: a reaction temperature of 86–95 °C, a reaction pressure of 1.5–1.9 MPa, and a reaction time of 20–40 min.

[0047] Furthermore, catalyst I and catalyst II are Ziegler-Natta catalysts, respectively.

[0048] Furthermore, catalyst I and catalyst II are used in combination with a co-catalyst, which is a metallic alkyl aluminum compound.

[0049] Furthermore, the system of reaction I contains an inert solvent; the inert solvent is an alkane solvent.

[0050] Furthermore, the inert solvent is selected from at least one of pentane, hexane, heptane, and octane.

[0051] Furthermore, in step S3, the polyethylene resin composition contains, in addition to polymer powder, at least one of antioxidant, ultraviolet absorber, antistatic agent, slip agent and nucleating agent.

[0052] Furthermore, reaction I is carried out in reactor I, and reaction II is carried out in reactor II, with reactor I and reactor II connected in series; reactor I and reactor II are slurry reactors, respectively.

[0053] According to a third aspect of this application, a bottle cap article is provided, wherein the material of the bottle cap article is the above-described polyethylene resin composition or the polyethylene resin composition prepared by the above-described preparation method.

[0054] Compared with the prior art, this application has the following beneficial effects:

[0055] The polyethylene resin composition of this application is composed of ethylene homopolymer and ethylene-1-hexene copolymer; the polyethylene resin composition has specific crystallization rinsing classification results and specific soluble content distribution width index; this specific molecular structure makes the polyethylene resin composition crystallization rate more uniform, reduces internal stress generation, thereby improving the stress cracking resistance of resin products and achieving a good balance with rigidity, toughness and molding shrinkage; making it more suitable for bottle cap products. Detailed Implementation

[0056] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0057] As mentioned in the background section, using polyethylene resin compositions as materials for bottle caps cannot achieve a good balance between the material's rigidity and toughness, stress cracking resistance, and shrinkage performance during the molding process. For polyethylene resin, lower density leads to higher stress cracking, which in turn results in lower tensile strength, significantly reducing rigidity and thus affecting the sealing strength of the bottle cap and limiting its thinning. Therefore, for injection-molded or compression-molded bottle caps, a good balance must be achieved between rigidity and toughness, stress cracking resistance, and shrinkage performance during the molding process.

[0058] According to one aspect of this application, a polyethylene resin composition is provided, the polyethylene resin composition comprising an ethylene homopolymer and an ethylene-1-hexene copolymer;

[0059] The crystallization elution fractionation (CEF) results of the polyethylene resin composition include:

[0060] F1 (70~85℃) = 1~10%, F2 (50~65℃) = 1~5%; and,

[0061] The soluble distribution width index (SDBI) of the polyethylene resin composition is 20–30 °C.

[0062] For example, Tw=∫T·w(T)dT,∫w(T)dT=1;

[0063] T is the rinsing temperature; T w t is the weight-average rinsing temperature; w(T) is the content of each component at each temperature.

[0064] The crystallization-elution fractionation (CEF) technique described in this application includes two temperature cycles: heating and cooling. During the cooling crystallization process in CEF, a small amount of solvent is pumped through the chromatographic column. When the crystallization temperature of one fraction is reached, that fraction crystallizes and deposits on the column. Other fractions dissolved in the solvent continue to move along the column until they are separated at other crystallization temperatures. Therefore, CEF minimizes the co-crystallization effect by separating fractions with different crystallization properties within the chromatographic column.

[0065] In the CEF grading results: F1 (70–85℃) represents the fraction content at rinsing temperatures between 70 and 85℃, and F2 (50–65℃) represents the fraction content at rinsing temperatures between 50 and 65℃; F1 (70–85℃) = 1–10%, for example, any value among 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%, or any range between two; F2 (50–65℃) = 1–5%, for example, any value among 1%, 2%, 3%, 4%, and 5%, or any range between two. By controlling these two fractions within appropriate ranges, the composition of multimodal polyethylene resin compositions composed of ethylene homopolymer and ethylene-hexene copolymer can be controlled, significantly improving the rigidity-toughness balance of the multimodal polyethylene resin composition and providing excellent resistance to environmental stress cracking.

[0066] The Soluble Distribution Width Index (SDBI) represents the distribution width of soluble components and can be determined using crystallization leaching fractionation (CEF) technology. When the distribution width is less than 20°C, it indicates that the components are concentrated in highly crystalline components, resulting in low molecular chain content in the connecting crystalline regions and deterioration of the resin composition's crack resistance. When the distribution width is greater than 30°C, the excessively wide component distribution causes uneven mixing of multiple components, leading to segregation and crystallization, which reduces the resin composition's crack resistance and also affects molding shrinkage performance. The SDBI of the polyethylene resin composition in this application is within the range of 20–30°C, for example, any value or any range between 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, and 30°C. Controlling the SDBI of the polyethylene composition within this range achieves a good balance between material rigidity and toughness, stress crack resistance, and molding shrinkage, making it more suitable for bottle cap materials.

[0067] The polyethylene resin composition of this application is composed of ethylene homopolymer and ethylene-hexene copolymer; the polyethylene resin composition has a specific crystallization rinsing classification result and a specific soluble content distribution width index; this specific molecular structure makes the polyethylene resin composition crystallization rate more uniform, reduces internal stress generation, thereby improving the stress cracking resistance of resin products and achieving a good balance with rigidity, toughness and molding shrinkage; making it more suitable for bottle cap products.

[0068] To optimize the balance between rigidity and toughness, stress cracking resistance and molding shrinkage of the polyethylene resin composition; to optimize the molecular structure of the polyethylene resin composition; in some embodiments, CEF: F1 (70-85°C) = 3-7%, F2 (50-65°C) = 2-4%; SDBI = 23-26°C.

[0069] Polymers are long chains formed by chemical bonds between repeating units (monomers). Unlike low-molecular-weight compounds, polymers do not have a fixed molecular weight; instead, they are mixtures of homologues with different molecular weights. Therefore, polymer molecular weight is an average value, a concept of distribution. Chain length is usually expressed as the molecular weight of the polymer chain, related to the relative molecular weight of the monomers and the number of monomers in the chain. However, all synthetic polymers are polydisperse, containing polymer chains of varying lengths, so the molecular weight of a polymer is not a single value, but rather a range of polymer chain lengths and molecular weights. Therefore, the molecular weight of a polymer must be described by calculating the average molecular weight of all polymer chains in the sample.

[0070] Among them, M w It is the weight-average molecular weight, relative to the number-average molecular weight M. n M w When determining the average molecular weight, the molecular weight of the single chain is compared with M. w The contribution is also taken into account; the greater the quality of the chain, the greater the contribution to M. w The greater the contribution, the higher the value; its calculation formula is M. w =Σ(N i ×M i 2 ) / ΣN i M i , where N i Indicates a molecular weight of M i The number of polymer molecules present in the sample. M z Z-mean molecular weight is a method for calculating average molecular weight; its calculation formula is M... z =Σ(N i ×M i 3 ) / ΣN i M i 2 M z+1 It is the Z+1 average molecular weight, and its calculation formula is M. z+1 =Σ(N i ×M i 4 ) / ΣN i M i 3 .

[0071] The distribution width index refers to the ratio of the relative molecular masses at I(M) = 80%, I(M) = 50%, and I(M) = 20% on the polymer's relative molecular mass integral distribution curve. Three relative molecular mass values ​​are taken from the curve: lg(M) 20 ), lg(M 50 ) and lg(M 80 ), where the subscript represents the mass fraction. lg(M 20 This indicates that 20% of the sample has a relative molecular mass in the range of M. 20 The following; lg(M 50 This indicates that 50% of the mass of the sample has a relative molecular mass in the range of M. 50 The following; lg(M 80 This indicates that 80% of the mass of the sample has a relative molecular mass in the range of M. 80 The following uses lg(M) 80 ) / lg(M 50 ) represents the distribution width of the high molecular weight portion, expressed as lg(M 50 ) / lg(M 20 The ) represents the distribution width of the low molecular weight fraction. The above molecular weight distribution parameters were determined using high-temperature gel permeation chromatography (GPC).

[0072] This application discovers the M of multimodal polyethylene resin compositions. z Relative to M w The ratio (M) z / M w M z+1 Relative to M z The ratio (M) z+1 / M z ), lg(M 80 ) / lg(M 50 The ratio of ) and lg(M) 50 ) / lg(M 20 The ratio of M to Toughness is related to the balance between stiffness and toughness and resistance to stress cracking. Specifically, by considering these ratios (M... z / M w ), (M z+1 / M z ), lg(M 80 ) / lg(M 50 ) and lg(M 50 ) / lg(M 20 Setting it within a specific range can ensure that the resin composition performs well in environmental stress cracking resistance (ESCR) and full notch creep test (FNCT) tests, which can prove its high stress cracking resistance.

[0073] To simultaneously balance ESCR, stiffness / toughness, and molding shrinkage properties, the molecular weight distribution characteristics of the polyethylene resin composition are controlled; in some embodiments, the molecular weight distribution of the polyethylene resin composition simultaneously satisfies the following condition: M w / M n =10~20; for example, M w / M n The ratio is any value from 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or a range between any two; for example, M w / M n =13~16. M z / M w ≥4.0; for example, M z / M w =4.0~5.5; furthermore, M z / M w ≥4.5; for example, M z / M w =4.5~5.5. M z+1 / M z ≥2.0; for example, M z+1 / M z =2.0~3.1; furthermore, M z+1 / M z ≥2.5; for example, M z+1 / M z =2.5~3.1. lg(M 80 ) / lg(M 50 )≥1.125, for example, lg(M 80 ) / lg(M 50 ) = 1.125 ~ 1.140; further, lg(M 80 ) / lg(M 50 )≥1.135; for example, lg(M 80 ) / lg(M 50 ) = 1.125~1.140. lg(M 50 ) / lg(M 20 )≥1.135; for example, lg(M 50 ) / lg(M 20 ) = 1.135~1.145; further, lg(M 50 ) / lg(M 20 )≥1.140; for example, lg(M 50 ) / lg(M 20The molecular weight distribution parameters are 1.140 to 1.145. By controlling these parameters within the specified range, the polymer exhibits high fluidity, which improves the moldability and high-speed processability of the product. Simultaneously, it maintains good ESCR and rigidity, contributing to the mechanical properties of the product.

[0074] To balance the stress cracking resistance, rigidity and toughness, and shrinkage properties during molding of the polyethylene resin composition, the proportions of each component in the composition are controlled. In some embodiments, the content of ethylene homopolymer in the polyethylene resin composition is 45-55 wt%, for example, any value or a range between 45%, 48%, 50%, 52%, and 55%; the content of ethylene copolymer in the polyethylene resin composition is 45-55 wt%, for example, any value or a range between 45%, 48%, 50%, 52%, and 55%. This application selects hexene as a comonomer. Compared with propylene and 1-butene, 1-hexene has a longer butyl branch, which increases the content of ligand molecules between crystal regions. When stress causes the ligand molecules to slip, they can be effectively fixed, strengthening the connection between crystal regions. This helps to improve the rigidity-toughness balance, stress crack resistance, and molding shrinkage performance of the polyethylene composition. By controlling the ratio of ethylene homopolymer and ethylene copolymer with different structural compositions, multi-peak polyethylene resin compositions can be formed, which can significantly improve the rigidity-toughness balance and stress crack resistance of polyethylene resin, achieving a good balance with molding shrinkage performance.

[0075] To further balance the stress cracking resistance, stiffness, toughness, and shrinkage properties of the polyethylene resin composition, the densities of the ethylene homopolymer and the polyethylene composition were optimized. In some embodiments, the density of the ethylene homopolymer was 0.965–0.970 g / cm³. 3 For example, 0.965, 0.966, 0.967, 0.968, 0.969, 0.970 g / cm³ 3 Any value in the range or any range between the two; for example, 0.965~0.968g / cm³. 3 The density of the polyethylene resin composition is 0.955–0.965 g / cm³. 3 ;0.955, 0.956, 0.957, 0.958, 0.959, 0.960, 0.961, 0.963, 0.963, 0.964, 0.965g / cm 3 Any value in the range or any range between the two; for example, 0.958–0.962 g / cm³. 3 By controlling the density of the ethylene homopolymer and polyethylene composition within the aforementioned range, it is helpful for the polyethylene resin composition to achieve a balance between stress crack resistance and rigidity / toughness, while also exhibiting a low shrinkage rate during the molding process.

[0076] To optimize the processing performance of the polyethylene resin composition and control the melt flow rate, in some embodiments, the melt flow rate of the ethylene homopolymer is 20–60 g / 10 min; for example, any value or a range between 20, 25, 30, 35, 40, 45, 50, 55, and 60 g / 10 min; preferably 40–55 g / 10 min; measurement conditions: temperature 190°C, load 2.16 kg. The melt flow rate of the polyethylene resin composition is 2.5–4.0 g / 10 min, for example, any value or a range between 2.5, 3.0, 3.5, and 4.0 g / 10 min; for example, 2.7–3.6 g / 10 min; measurement conditions: temperature 190°C, load 2.16 kg. A melt flow rate within the above range not only ensures high resin fluidity, which is beneficial for high-speed molding, but also provides good stress cracking resistance and rigidity.

[0077] In some embodiments, the molding shrinkage of the polyethylene resin composition after molding and cooling for 48 hours, parallel to the melt flow direction, is ≤2.0, for example, 1.1 to 2.0; further, the molding shrinkage is ≤1.5, for example, 1.10 to 1.50. The molding shrinkage perpendicular to the melt flow direction is ≤0.8, for example, 0.42 to 0.80; further, the molding shrinkage is ≤0.6, for example, 0.42 to 0.60. The molding shrinkage of the polyethylene resin composition after molding and cooling for 72 hours, parallel to the melt flow direction, is ≤2.2, for example, 1.32 to 2.0; further, the molding shrinkage is ≤1.8, for example, 1.32 to 1.8. The molding shrinkage perpendicular to the melt flow direction is ≤1.0, for example, 0.60 to 1.0; further, the molding shrinkage is ≤0.8, for example, 0.6 to 0.8. The polyethylene resin composition exhibits an ESCR ≥ 400 hours; for example, 400–700 hours; further, an ESCR ≥ 600 hours; for example, 600–700 hours. The polyethylene resin composition also exhibits a FNCT ≥ 30 hours; for example, 30–58 hours; further, an FNCT ≥ 40 hours; for example, 40–58 hours. Measurement conditions: stress 4.0 MPa, temperature 80°C. Due to the specific molecular structure described above, the polyethylene resin composition achieves excellent ESCR while also possessing good rigidity and toughness, as well as low molding shrinkage.

[0078] In some embodiments, the notched impact strength of the polyethylene resin composition is ≥12.0 kJ / m. 2 For example, 12.5–18.0 kJ / m 2 Further ≥15.0 kJ / m 2 For example, 15.0~18.0kJ / m 2The tensile yield stress of the polyethylene resin composition is ≥22.0 MPa; for example, 22.0–26.0 MPa; further ≥25.0 MPa; for example, 25.0–26.0 MPa; and the nominal tensile strain at break of the polyethylene resin composition is ≥400%; for example, 430–605%; further ≥550%; for example, 550–600%. Due to the specific molecular structure described above, the polyethylene resin composition exhibits excellent mechanical properties.

[0079] According to a second aspect of this application, a method for preparing the above-mentioned polyethylene resin composition is provided, comprising:

[0080] Step S1: Ethylene I and hydrogen I are reacted in the presence of catalyst I to obtain stream I containing ethylene homopolymer; wherein, the feed ratio of ethylene I to hydrogen I is 1 kg / h: (8.1 g / h ~ 15.0 g / h);

[0081] Step S2: Stream I, ethylene II, hydrogen II and 1-hexene are reacted in the presence of catalyst II to obtain stream II containing ethylene homopolymer and ethylene-hexene copolymer; wherein the feed ratio of ethylene II, hydrogen II and 1-hexene is 1 kg / h:(0.5 g / h~2.5 g / h):(101 g / h~200 g / h);

[0082] Step S3: Separate and dry the material II sequentially to obtain polymer powder, i.e., polyethylene resin composition.

[0083] In step S1 of this application, when the feed rate of ethylene I is 1 kg / h, the feed rate of hydrogen I is any value or a range between any two of 8.1, 8.5, 9.0, 9.5, 10, 10.5, 11, 11.5, 12.0, 12.5, 13.0, 13.5, 14, 14.5, and 15.0 g / h; in step S2, when the feed rate of ethylene II is 1 kg / h, the feed rate of hydrogen II is any value or a range between any two of 0.5, 1.0, 1.5, 2.0, and 2.5 g / h; and the feed rate of 1-hexene is any value or a range between any two of 101, 105, 110, 120, 130, 140, 150, 160, 170, 180, 190, and 200 g / h.

[0084] In some embodiments, in step S1, the feed ratio of ethylene I to hydrogen I is 1 kg / h:(10.0 g / h to 12.0 g / h); in step S2, the feed ratio of ethylene II, hydrogen II, and 1-hexene is 1 kg / h:(1.0 g / h to 2.0 g / h):(120 g / h to 180 g / h). Further optimization of the ethylene / hydrogen weight ratio and the ethylene / hydrogen / hexene weight ratio helps to obtain ideal polymer molecular weight, molecular weight distribution, CEF classification results, SDBI, crystallinity, and density, resulting in a polyethylene resin composition with ideal structure and properties. This polyethylene composition with a specific molecular structure exhibits good stress cracking resistance, rigidity and toughness, and molding shrinkage, achieving an effective balance between mechanical properties and processability.

[0085] In some embodiments, the conditions for reaction I include: a reaction temperature of 80–95°C, a reaction pressure of 1.4–2.0 MPa, and a reaction time of 10–100 min; further, a reaction temperature of 82–92°C, a reaction pressure of 1.5–1.9 MPa, and a reaction time of 20–40 min; even further, a reaction temperature of 86–90°C, a reaction pressure of 1.6–1.8 MPa, and a reaction time of 24–36 min. The conditions for reaction II include: a reaction temperature of 85–100°C, a reaction pressure of 1.4–2.0 MPa, and a reaction time of 10–100 min; further, a reaction temperature of 86–95°C, a reaction pressure of 1.5–1.9 MPa, and a reaction time of 20–40 min; even further, a reaction temperature of 88–92°C, a reaction pressure of 1.6–1.8 MPa, and a reaction time of 250–35 min. Optimizing the reaction temperature, reaction pressure, and reaction time in the first and second stages allows for more precise control of the molecular structure of the polyethylene resin composition, resulting in good mechanical properties and processability.

[0086] This application employs the aforementioned sequential polymerization method, in which the first ethylene homopolymer component and the second ethylene copolymer component are prepared in a method comprising at least two reactors in series. Specifically, the term sequential polymerization indicates that the reaction mixture (i.e., the first ethylene homopolymer component and unreacted monomers) from the first reactor is conveyed, preferably directly to the second reactor, to obtain the second ethylene copolymer component. The method of this application includes at least a first reactor and a second reactor; the method may include at least one additional polymerization reactor following the second reactor; preferably, it consists of two polymerization reactors (i.e., the first reactor and the second reactor); the reactors are typically selected from slurry reactors and gas-phase reactors; the first reactor is preferably a first slurry reactor, and can be any continuous or simply stirred batch reactor or loop reactor carried out in bulk polymerization or slurry polymerization; the second reactor is preferably a second slurry reactor; possible subsequent one or more polymerization reactors are preferably slurry reactors.

[0087] This application allows the addition of hydrogen gas in the first reactor to control the molecular weight of the ethylene homopolymer component obtained in the first reactor, thereby controlling the melt mass flow rate of the ethylene homopolymer component; it also allows control of the molecular weight of the ethylene copolymer component in the second reactor, thereby controlling the melt mass flow rate of the ethylene copolymer. Using the aforementioned weight ratio of ethylene to 1-hexene, a molecular structure with ideal CEF elution fractionation and SDBI can be obtained, along with suitable crystallinity and density, resulting in a resin with suitable rigidity and toughness, stress crack resistance, and low molding shrinkage. Through the synergistic effect of the respective material weight ratios in the first and second reactors, the polyethylene resin composition containing ethylene homopolymer and ethylene-hexene copolymer achieves the expected crystallization elution fractionation and soluble content distribution width index (SDBI); thus, the polyethylene composition exhibits good stress crack resistance and rigidity / toughness while also having a low molding shrinkage; this material is more advantageous for the processing and use of bottle cap products.

[0088] In some embodiments, slurry polymerization is carried out in an inert solvent, typically a hydrocarbon solvent, such as at least one selected from pentane, hexane, heptane, and octane. Polymerization is carried out in the presence of an olefin polymerization catalyst; the catalyst can be any catalyst capable of preparing the desired ethylene polymer; suitable catalysts are transition metal-based Ziegler-Natta (ZN) catalysts, metallocene catalysts, and / or non-metallocene catalysts; preferably, a Ziegler-Natta (ZN) catalyst. The Ziegler-Natta (ZN) catalyst comprises magnesium compounds, aluminum compounds, and titanium compounds, optionally supported on a support; wherein the support can be an inorganic oxide support, such as silica, alumina, titanium dioxide, silica-alumina, and silica-titanium dioxide. Preferably, the support is silica.

[0089] The magnesium compound is 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 butyl-octyl magnesium, magnesium n-octyloxy, and magnesium 2-ethylhexyloxy.

[0090] The aluminum compound is selected from at least one of triethylaluminum, diethylaluminum chloride, diethylaluminum chloride, sesquiethylaluminum, diisobutylaluminum chloride, triisobutylaluminum chloride, diisopropylaluminum chloride, methylpropylaluminum chloride, and diphenylaluminum chloride.

[0091] The titanium compound is a halogenated titanium compound 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. Titanium tetrachloride is a preferred titanium compound.

[0092] In some embodiments, the catalyst can be prepared by sequentially contacting a support with the aforementioned compounds, or by first preparing solutions from the components and then contacting the solutions with the support. Preferably, the Ziegler-Natta catalyst (ZN) is used in conjunction with an activator; the activator is used as a co-catalyst. Suitable activators are metallic alkyl compounds, and particularly alkylaluminum compounds; these compounds include alkylaluminum halides, such as ethylaluminum dichloride, diethylaluminum chloride, ethylaluminum sesquichloride, dimethylaluminum chloride, etc.; they also include trialkylaluminum compounds, such as trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, and tri-n-octylaluminum. In addition, they include alkyl aluminum oxides, such as methylaluminoxane (MAO), hexaisobutylaluminoxane (HIBAO), and tetraisobutylaluminoxane (TIBAO); other alkyl aluminum compounds, such as diisobutylaluminum hydride, may also be used; the preferred activator is trialkylaluminum, particularly triethylaluminum, trimethylaluminum, and triisobutylaluminum; the amount of activator used depends on the specific catalyst and activator; typically, the amount of triethylaluminum is such that the molar ratio of aluminum to transition metal (e.g., Al / Ti) is 3 to 300 mol / mol, preferably 5 to 50 mol / mol.

[0093] In some embodiments, in step S3, the polyethylene resin composition, in addition to containing polymer powder, also includes at least one of an antioxidant, an ultraviolet absorber, an antistatic agent, a slip agent, and a nucleating agent. The antioxidant is a compound that prevents the polyethylene resin from decomposing due to heat, light, oxygen, etc.; it can be selected from phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, hydroxylamine antioxidants, metal passivators, etc., preferably phenolic antioxidants, phosphorus antioxidants, or sulfur antioxidants.

[0094] Phenolic antioxidants can be selected from 2,6-di-tert-butyl-4-methylphenol, tetra[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane, tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol ester, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 3,9-bis[2-{3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetra[ oxaspiro[5·5]undecane, 1,3,5-tris-2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]ethyl isocyanurate, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate, pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxybenzyl) ... [3,5-di-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], triethylene glycol-bis-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2'-dithio-diethylidene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2'-methylene-bis-(4-methyl-6-tert-butylphenol), 2,2'-methylene-bis-(4-ethyl-6-tert-butylphenol), 2,2'-methylene The antioxidants include 2,2'-ethylidene-bis-(4,6-di-tert-butylphenol), 2,2'-butylidene-bis-(4-methyl-6-tert-butylphenol), 4,4'-butylidene-bis(3-methyl-6-tert-butylphenol), 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 2,4-di-tert-pentyl-6-(1-(3,5-di-tert-pentyl-2-hydroxyphenyl)ethyl)phenyl acrylate, and tocopherols. The content of phenolic antioxidants is typically 0.01 to 2 parts by weight relative to 100 parts by weight of the polyethylene resin composition, preferably 0.01 to 0.5 parts by weight.

[0095] Phosphorus-based antioxidants can be selected from tris(nonylphenyl) phosphite, tris(2,4-di-tert-butylphenyl) phosphite, distearate pentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis(2,4-di-tert-butyl-6-methylphenyl) pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, bis(2,4-di-tert-butyl-6-methylphenyl) pentaerythritol diphosphite, and bis(2,4-di-tert-butyl-6-methylphenyl) pentaerythritol diphosphite. Pentaerythritol diphosphite (2,4-di-tert-butylphenyl)-4,4'-biphenylene diphosphite, 2,2'-methylenebis(4,6-di-tert-butylphenyl)2-ethylhexyl phosphite, 2,2'-ethoxybis(4,6-di-tert-butylphenyl)fluorophosphite, bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite, 2-(2,4,6-tri-tert-butylphenyl) )-5-ethyl-5-butyl-1,3,2-dioxaphosphacyclohexane, 2,2',2"-nitro[triethyl-tris(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-diyl)phosphite, 2,4,8,10-tetra-tert-butyl-6-[3-(3-methyl-4-hydroxy-5-tert-butylphenyl)propoxy]dibenzo[d,f][1,3,2]dioxane Phosphorus-based antioxidants, etc., are preferred. Tris(2,4-di-tert-butylphenyl) phosphite or 2,4,8,10-tetra-tert-butyl-6-[3-(3-methyl-4-hydroxy-5-tert-butylphenyl)propoxy]dibenzo[d,f][1,3,2]dioxane is preferred. The content of the phosphorus-based antioxidant is typically 0.01 to 2 parts by weight relative to 100 parts by weight of the polyethylene resin composition, preferably 0.01 to 0.5 parts by weight.

[0096] The sulfur-based antioxidant can be selected from dilauryl 3,3'-thiodipropionate, tridecyl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearate 3,3'-thiodipropionate, lauryl stearate 3,3'-thiodipropionate, pentaerythritol tetra(3-lauryl thiopropionate), bis[2-methyl-4-(3-n-alkyl(C12-C14)thiopropionoxy)-5-tert-butylphenyl] sulfide, etc. Preferred are dilauryl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, or distearate 3,3'-thiodipropionate. The amount of sulfur-based antioxidant relative to 100 parts by weight of the polyethylene resin composition is typically 0.01 to 2 parts by weight, preferably 0.01 to 0.5 parts by weight.

[0097] The slip agent can be used in conjunction with a polyethylene resin composition to facilitate sliding between the resin compositions when they come into contact, especially to facilitate sliding between resin components such as bottle caps, thereby simplifying handling. The slip agent can be selected from various known aliphatic acid amide compounds, particularly saturated aliphatic acid amides and unsaturated aliphatic acid bisamides. Saturated aliphatic acid amides are selected from palmitamide, stearamide, docosamide, etc., with docosamide being preferred. Unsaturated aliphatic acid amides are selected from oleamide, erucamide, etc., with erucamide being preferred. Saturated aliphatic acid bisamides are selected from ethylene bispalmitamide, ethylene bisstearamide, hexamethylene bisstearamide, etc., with ethylene bisstearamide being preferred. The unsaturated aliphatic diamide is selected from ethylene dioleamide, hexamethylene dioleamide, N,N”-dioleoyl sebacate, etc.; ethylene dioleamide is preferred. Two or more of the above-mentioned slip agents can be used together. When two or more slip agents are used together, it is preferred to use a complex composed of an unsaturated aliphatic acid amide and a saturated or unsaturated aliphatic acid diamide. The content of the slip agent is generally 0.05 to 0.35 parts by weight relative to 100 parts by weight of the polyethylene resin composition, preferably 0.1 to 0.25 parts by weight.

[0098] Nucleating agents can be used in conjunction with polyethylene resin compositions. When used in appropriate amounts with the polyethylene resin composition, these nucleating agents increase the crystallization rate while providing a more uniform crystal distribution and size, resulting in more uniform melt crystallization behavior during the processing of articles formed based on the polyethylene resin composition, and also improving the rigidity of the articles. The nucleating agents are selected from calcium 1,2-cyclohexanedicarboxylate and / or sodium 4-[(4-chlorobenzoyl)amino]benzoate. The nucleating agent content is typically 0.01 to 0.30 parts by weight relative to 100 parts by weight of the polyethylene resin composition, preferably 0.05 to 0.20 parts by weight.

[0099] According to a third aspect of this application, a bottle cap article is provided, the material of which is the above-described polyethylene resin composition or a polyethylene resin composition prepared by the above-described preparation method. The multi-peaked polyethylene resin composition of this application can be used to form any molded article; container articles such as bottles, caps, and closures; transport packaging such as boxes, baskets, cabinets, etc.; household utensils such as buckets, food containers, and sinks; and thin-walled packaging articles such as open plastic containers for frozen or fresh food.

[0100] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0101] The raw materials used in the embodiments of this application are all existing technologies and are commercially available.

[0102] CEF fractionation: Crystallization elution fractionation curves were obtained using a Crystallization Elution Fractionation (CEF) instrument from Polymer Char, Spain. Approximately 10 mg of sample was dissolved in o-dichlorobenzene at 160 °C for 90 min, then cooled to 95 °C at a rate of 30 °C / min for stabilization. Crystallization was then carried out at a rate of 2 °C / min to 35 °C, while the column was slowly flushed by a liquid phase pump at a rate of 0.05 mL / min. After crystallization, elution was initiated at a rate of 4 °C / min and 1 mL / min to 150 °C. The sample information during the elution process was recorded using an IR-5 infrared detector, yielding the crystallization elution fractionation curves.

[0103] Molecular weight and distribution: High-temperature gel permeation chromatography (GPC) was used. The sample was dissolved in 1,2,4-trichlorobenzene at a concentration of 1.0 mg / mL. The test temperature was 150℃, and the solution flow rate was 1.0 mL / min. A standard curve was established using the molecular weight of polystyrene as an internal reference. The molecular weight and molecular weight distribution of the sample were calculated based on the elution time, and the weight-average molecular weight (M) was calculated. W Z-average molecular weight (M) z Z+1 average molecular weight (M) Z+1 ).

[0104] Melt mass flow rate (MFR): Tested in accordance with GB / T 3682-2018.

[0105] Density: Tested in accordance with GB / T 1033.2-2010.

[0106] Notched impact strength: determined according to the method specified in GB / T 1043.1-2008.

[0107] Tensile properties: determined according to the method specified in GB / T 1040.2-2006.

[0108] Environmental stress cracking resistance (ESCR): Tested according to GB / T 1842-2008, using condition B.

[0109] Molding shrinkage: Determined according to the method specified in GB / T 17037.4-2003. The test specimens were stored at room temperature (23±2℃) and their dimensions were measured at 48 hours and 72 hours. The molding shrinkage rates parallel and perpendicular to the melt flow direction were calculated.

[0110] Full-notch creep test (FNCT): A full-notch creep test is performed according to ISO 16770 at a stress of 4.0 MPa and a temperature of 80°C. Specifically, the sample used for FNCT is a cuboid with dimensions of 10 × 10 × 100 mm, obtained by grinding a plate with a thickness of 15 mm. Then, notches with a depth of 1.5 mm are formed on the four sides of the sample, and a stress of 4.0 MPa is applied to the sample in a 10% Igepal solution at 80°C. The time taken until the sample breaks is then measured.

[0111] Example 1

[0112] A method for preparing a resin composition includes the following steps:

[0113] Catalyst Preparation: 90 kg of toluene was added to a reactor thoroughly purged with high-purity nitrogen. Then, 50 kg of butyloctylmagnesium in heptane was added to the reactor. Next, 160 kg of 99.9% 2-ethyl-1-hexanol was introduced into the reactor at a flow rate of 20 kg / h to form a complex. The molar ratio of butyloctylmagnesium to 2-ethyl-1-hexanol was 1:1.8. 300 kg of silica activated in nitrogen at 600 °C was charged into the catalyst preparation reactor. At room temperature, 400 kg of 20% silica diluted in 600 L of pentane was added to the reactor over 1 hour. The temperature was then raised to 40 °C while stirring the treated silica for 1.5 hours. The silica was dried at 50 °C for 10 hours. Then, 670 kg of the complex prepared as described above was added over 10 minutes at 25 °C. Finally, 90 kg of pentane was added to the reactor over 10 minutes at 25 °C. The slurry was stirred at 50°C for 10 hours. Finally, 56 kg of TiCl4 was added at 50°C over 0.5 hours. The slurry was then stirred at 40°C for 5 hours. The catalyst was then obtained by purging with nitrogen.

[0114] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 567 g / h (1:8.1) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 80 °C, the reaction pressure was 1.4 MPa, and the reaction time was 20 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0115] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 85°C, and the reaction pressure is 1.4 MPa. The feed rate to the second reactor is 85.5 kg / h for ethylene, 47.75 g / h for hydrogen, and 8635.5 g / h for the comonomer 1-hexene (1:0.5:101). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor, and the slurry is dried to obtain the final polymer powder.

[0116] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0117] Example 2

[0118] The difference between Example 2 and Example 1 is that the preparation process of the resin composition is different;

[0119] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 686 g / h (1:9.8) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 95°C, the reaction pressure was 2.0 MPa, and the reaction time was 60 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0120] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization reaction temperature in the second reactor is 100℃, and the reaction pressure is 2.0 MPa. The feed rate to the second reactor is 80.2 kg / h for ethylene, 200.5 g / h for hydrogen, and 16040 g / h for the comonomer 1-hexene (1:2.5:200). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor and dried to obtain the final polymer powder.

[0121] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0122] Example 3

[0123] The difference between Example 3 and Example 1 is that the preparation process of the resin composition is different;

[0124] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 700 g / h (1:10) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 86 °C, the reaction pressure was 1.6 MPa, and the reaction time was 30 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0125] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 88°C, and the reaction pressure is 1.6 MPa. The feed rate to the second reactor is 77.2 kg / h for ethylene, 100.4 g / h for hydrogen, and 10036 g / h for 1-hexene (1:1.3:130). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor, and the slurry is dried to obtain the final polymer powder.

[0126] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0127] Example 4

[0128] The difference between Example 4 and Example 1 is that the preparation process of the resin composition is different;

[0129] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate at 70 kg / h, and the hydrogen feed rate at 665 g / h (1:9.5) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 83 °C, the reaction pressure was 1.4 MPa, and the reaction time was 28 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0130] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 86°C, and the reaction pressure is 1.5 MPa. The feed rate to the second reactor is 84.5 kg / h for ethylene, 202.8 g / h for hydrogen, and 9295 g / h for the comonomer 1-hexene (1:2.4:110). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor and dried to obtain the final polymer powder.

[0131] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0132] Example 5

[0133] The difference between Example 5 and Example 1 is that the preparation process of the resin composition is different;

[0134] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 770 g / h (1:11) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 88 °C, the reaction pressure was 1.7 MPa, and the reaction time was 28 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0135] The ethylene-containing homopolymer stream from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 89°C, and the reaction pressure is 1.7 MPa. The feed rates for the second reactor are 78.1 kg / h of ethylene, 156.2 g / h of hydrogen, and 9372 g / h of 1-hexene (1:2:120) as the comonomer. This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor, and the slurry is dried to obtain the final polymer powder.

[0136] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0137] Example 6

[0138] The difference between Example 6 and Example 1 is that the preparation process of the resin composition is different;

[0139] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 840 g / h (1:12) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 90 °C, the reaction pressure was 1.8 MPa, and the reaction time was 35 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0140] The ethylene-containing homopolymer stream from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 91°C, and the reaction pressure is 1.8 MPa. The feed rates for the second reactor are 86.5 kg / h for ethylene, 86.5 g / h for hydrogen, and 15570 g / h for 1-hexene (1:1:180). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor, and the slurry is dried to obtain the final polymer powder.

[0141] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0142] Example 7

[0143] The difference between Example 7 and Example 1 is that the preparation process of the resin composition is different;

[0144] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate at 70 kg / h, and the hydrogen feed rate at 602 g / h: (1:8.6) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 82°C, the reaction pressure was 1.5 MPa, and the reaction time was 30 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0145] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 86°C, and the reaction pressure is 1.5 MPa. The feed rate to the second reactor is 80.5 kg / h for ethylene, 48.3 g / h for hydrogen, and 8450.5 g / h for the comonomer 1-hexene (1:0.6:105). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor, and the slurry is dried to obtain the final polymer powder.

[0146] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0147] Example 8

[0148] The difference between Example 8 and Example 1 is that the preparation process of the resin composition is different;

[0149] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 616 g / h (1:8.8) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 93 °C, the reaction pressure was 1.9 MPa, and the reaction time was 50 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0150] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 95°C, and the reaction pressure is 1.9 MPa. The feed rate to the second reactor is 74.2 kg / h for ethylene, 163.24 g / h for hydrogen, and 14098 g / h for the comonomer 1-hexene (1:2.2:190). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor and dried to obtain the final polymer powder.

[0151] The polymer powder was mixed with 0.1% of antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The amounts of both antioxidants added were based on 100% of the mass of the resin composition.

[0152] Example 9

[0153] The difference between Example 9 and Example 1 is that the preparation process of the resin composition is different;

[0154] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 805 g / h (1:11.5) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 90 °C, the reaction pressure was 1.75 MPa, and the reaction time was 36 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0155] The ethylene homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 91°C, and the reaction pressure is 1.8 MPa. The feed rate to the second reactor is 75.2 kg / h for ethylene, 60.2 g / h for hydrogen, and 12458 g / h for 1-hexene (1:0.8:165). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor and dried to obtain the final polymer powder.

[0156] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0157] Example 10

[0158] The difference between Example 10 and Example 1 is that the preparation process of the resin composition is different;

[0159] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 980 g / h (1:14) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 82 °C, the reaction pressure was 1.5 MPa, and the reaction time was 38 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0160] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 86°C, and the reaction pressure is 1.5 MPa. The feed rate to the second reactor is 70.5 kg / h for ethylene, 63.45 g / h for hydrogen, and 8107.5 g / h for the comonomer 1-hexene (1:0.9:115). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor, and the slurry is dried to obtain the final polymer powder.

[0161] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0162] Example 11

[0163] The difference between Example 11 and Example 1 is that the preparation process of the resin composition is different;

[0164] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 945 g / h (1:13.5) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 92 °C, the reaction pressure was 1.9 MPa, and the reaction time was 40 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0165] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 92°C, and the reaction pressure is 1.9 MPa. The feed rate to the second reactor is 70.0 kg / h for ethylene, 105 g / h for hydrogen, and 10500 g / h for 1-hexene (1:1.5:150) to obtain the second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor and dried to obtain the final polymer powder.

[0166] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0167] Example 12

[0168] The difference between Example 12 and Example 1 is that the preparation process of the resin composition is different;

[0169] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 1050 g / h (1:15) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 81 °C, the reaction pressure was 1.45 MPa, and the reaction time was 40 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0170] The ethylene-containing homopolymer stream from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 85°C, and the reaction pressure is 1.5 MPa. The feed rates for the second reactor are 68.5 kg / h for ethylene, 65.1 g / h for hydrogen, and 8083 g / h for 1-hexene (1:0.95:118). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor, and the slurry is dried to obtain the final polymer powder.

[0171] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0172] Comparative Example 1

[0173] The difference between Comparative Example 1 and Example 1 is that the preparation process of the resin composition is different;

[0174] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 350 g / h (1:5) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 84 °C, the reaction pressure was 0.55 MPa, and the reaction time was 45 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0175] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization reaction temperature in the second reactor is 75°C, and the reaction pressure is 0.15 MPa. The feed rate to the second reactor is 66.5 kg / h for ethylene, 20 g / h for hydrogen, and 5985 g / h for the comonomer 1-hexene (1:0.3:90). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor and dried to obtain the final polymer powder.

[0176] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0177] Comparative Example 2

[0178] The difference between Comparative Example 2 and Example 1 is that the preparation process of the resin composition is different;

[0179] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate at 70 kg / h, and the hydrogen feed rate at 385 g / h (1:5.5) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 88°C, the reaction pressure was 0.8 MPa, and the reaction time was 30 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0180] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 75°C, and the reaction pressure is 0.20 MPa. The feed rate to the second reactor is 65.5 kg / h for ethylene, 18.34 g / h for hydrogen, and 13428 g / h for the comonomer 1-hexene (1:0.28:205). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor, and the slurry is dried to obtain the final polymer powder.

[0181] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0182] Comparative Example 3

[0183] The difference between Comparative Example 3 and Example 1 is that the preparation process of the resin composition is different;

[0184] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 357 g / h (1:5.1) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 81 °C, the reaction pressure was 0.55 MPa, and the reaction time was 55 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0185] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization reaction temperature in the second reactor is 73°C, and the reaction pressure is 0.25 MPa. The feed rate to the second reactor is 60.5 kg / h for ethylene, 24.2 g / h for hydrogen, and 5748 g / h for the comonomer 1-hexene (1:0.4:95). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor and dried to obtain the final polymer powder.

[0186] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0187] Comparative Example 4

[0188] The difference between Comparative Example 4 and Example 1 is that the preparation process of the resin composition is different;

[0189] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 357 g / h (1:5.1) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 88 °C, the reaction pressure was 0.6 MPa, and the reaction time was 45 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0190] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 72°C, and the reaction pressure is 0.35 MPa. The feed rate to the second reactor is 70.5 kg / h for ethylene, 17.63 g / h for hydrogen, and 14805 g / h for the comonomer 1-hexene (1:0.25:210). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor, and the slurry is dried to obtain the final polymer powder.

[0191] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0192] Comparative Example 5

[0193] The difference between Comparative Example 5 and Example 1 is that the preparation process of the resin composition is different;

[0194] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 350 g / h (1:5) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 83 °C, the reaction pressure was 0.9 MPa, and the reaction time was 40 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0195] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 72°C, and the reaction pressure is 0.25 MPa. The feed rate to the second reactor is 68.5 kg / h for ethylene, 13.7 g / h for hydrogen, and 5823 g / h for the comonomer 1-hexene (1:0.2:85). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor and dried to obtain the final polymer powder.

[0196] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0197] Comparative Example 6

[0198] The difference between Comparative Example 6 and Example 1 is that the preparation process of the resin composition is different;

[0199] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 357 g / h (1:5.1) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 89 °C, the reaction pressure was 0.7 MPa, and the reaction time was 35 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0200] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 70°C, and the reaction pressure is 0.20 MPa. The feed rate to the second reactor is 59.2 kg / h for ethylene, 23.7 g / h for hydrogen, and 13320 g / h for the comonomer 1-hexene (1:0.4:225). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor, and the slurry is dried to obtain the final polymer powder.

[0201] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0202] Comparative Example 7

[0203] The difference between Comparative Example 7 and Example 1 is that the preparation process of the resin composition is different;

[0204] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 315 g / h (1:4.5) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 88 °C, the reaction pressure was 0.55 MPa, and the reaction time was 45 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0205] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 72°C, and the reaction pressure is 0.35 MPa. The feed rate to the second reactor is 74.5 kg / h for ethylene, 37.3 g / h for hydrogen, and 17880 g / h for 1-hexene (1:0.5:240). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor and dried to obtain the final polymer powder.

[0206] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0207] Comparative Example 8

[0208] The difference between Comparative Example 8 and Example 1 is that the preparation process of the resin composition is different;

[0209] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 1680 g / h (1:24) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 86 °C, the reaction pressure was 0.55 MPa, and the reaction time was 51 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0210] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 70°C, and the reaction pressure is 0.35 MPa. The feed rate to the second reactor is 62.5 kg / h for ethylene, 281.25 g / h for hydrogen, and 14375 g / h for the comonomer 1-hexene (1:4.5:230). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor and dried to obtain the final polymer powder.

[0211] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0212] Comparative Example 9

[0213] The difference between Comparative Example 9 and Example 1 is that the preparation process of the resin composition is different;

[0214] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 490 g / h (1:7) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 82 °C, the reaction pressure was 0.35 MPa, and the reaction time was 45 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0215] The ethylene-containing homopolymer stream obtained from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 75°C, and the reaction pressure is 0.30 MPa. The feed rate to the second reactor is 75.5 kg / h for ethylene, 15.1 g / h for hydrogen, and 16232.5 g / h for the comonomer 1-hexene (1:0.2:215). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor, and the slurry is dried to obtain the final polymer powder.

[0216] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0217] Comparative Example 10

[0218] The difference between Comparative Example 10 and Example 1 is that the preparation process of the resin composition is different;

[0219] Resin composition preparation: The process was carried out continuously in two slurry reactors connected in series. The ZN catalyst prepared by the above method was continuously fed into the first reactor at a rate of 15.1 mmol / h, the co-catalyst (triethylaluminum) at a rate of 150 mmol / h, the ethylene feed rate of 70 kg / h, and the hydrogen feed rate of 504 g / h (1:7.2) to complete the first stage of homopolymerization of ethylene, yielding the first ethylene polymer. The polymerization reaction temperature in the first reactor was 81 °C, the reaction pressure was 0.75 MPa, and the reaction time was 55 min. Hydrogen was added to the feed of the first reactor as a molecular weight regulator, and hexane was used as a solvent at a feed rate of 150 kg / h.

[0220] The ethylene-containing homopolymer stream from the first reactor is fed into the second reactor. The polymerization temperature in the second reactor is 69°C, and the reaction pressure is 0.20 MPa. The feed rate to the second reactor is 72.5 kg / h for ethylene, 18.2 g / h for hydrogen, and 15950 g / h for 1-hexene (1:0.25:220). This yields a second ethylene copolymer. The solvent is separated from the slurry discharged from the second reactor, and the slurry is dried to obtain the final polymer powder.

[0221] The polymer powder was mixed with 0.1% of the antioxidants pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.1% of tris(2,4-di-tert-butylphenyl) phosphite, and then melt-extruded and granulated to obtain a multi-peak polyethylene resin composition. The addition of both antioxidants was based on 100% of the mass of the resin composition.

[0222] Performance testing:

[0223] Based on the aforementioned evaluation and analysis methods, the resin compositions prepared in each of the above embodiments and comparative examples were subjected to corresponding performance tests, and the specific results are shown in Tables 1, 2 and 3 below.

[0224] Table 1

[0225]

[0226]

[0227] Table 2

[0228]

[0229]

[0230] Table 3

[0231]

[0232] As shown in Table 1, the polyethylene resin compositions of Examples 1-12 of this application possess specific microscopic molecular chain structures. For example, the crystallization leaching fractionation (CEF) results of the polyethylene resin compositions include: F1 (70-85°C) = 1-10%, F2 (50-65°C) = 1-5%; and the soluble content distribution width index (SDBI) = 20-30°C. Further, M... w / M n =10~20; M z / M w =4.0~5.5; M z+1 / M z =2.0~3.1; lg(M 80 ) / lg(M 50 ) = 1.125 ~ 1.140, lg(M 50 ) / lg(M 20 = 1.135~1.145. Furthermore, the density of the ethylene homopolymer is 0.965~0.970 g / cm³. 3 The density of the polyethylene resin composition is 0.955–0.965; furthermore, the melt flow rate of the ethylene homopolymer is 20–60 g / 10 min; the melt flow rate of the polyethylene resin composition is 2.5–4.0 g / 10 min.

[0233] The macroscopic properties of the polyethylene resin compositions in Tables 2 and 3 are derived from the microscopic molecular chain structure characteristics of the polyethylene resin compositions in Table 1. For example: after molding and cooling for 48 hours, the molding shrinkage parallel to the melt flow direction of the polyethylene resin composition is ≤2.0, and the molding shrinkage perpendicular to the melt flow direction is ≤0.8; after molding and cooling for 72 hours, the molding shrinkage parallel to the melt flow direction is ≤2.2, and the molding shrinkage perpendicular to the melt flow direction is ≤1.0. The tensile yield stress of the polyethylene resin composition is 22–26 MPa; the nominal tensile strain at break of the polyethylene resin composition is 430–605%; and the notched impact strength of the simply supported beam of the polyethylene resin composition is 12.5–18 kJ / m. 2 The ESCR of the polyethylene resin composition is 400–700 hours; the FNCT of the polyethylene resin composition is 40–58 hours.

[0234] In contrast, the microscopic molecular chain structures of the polyethylene resin compositions in Comparative Examples 1-10 of Table 1 differ from those of this application. The macroscopic properties of the polyethylene resin compositions in Tables 2 and 3 are derived from the microscopic molecular chain structure characteristics of the polyethylene resin compositions in Table 1. For example, the tensile yield stress of the polyethylene resin composition is 17-20 MPa; the notched impact strength of the simply supported beam of the polyethylene resin composition is 9.5-11 kJ / m. 2 Its mechanical properties are significantly lower than those of Examples 1-12. The ESCR of the polyethylene resin composition is 280-330 hours; its stress crack resistance is significantly lower than that of Examples 1-12. The FNCT of the polyethylene resin composition is 23-28 hours; its flow properties are also significantly lower than those of this application. The average molding shrinkage of the polyethylene resin composition parallel to the melt flow direction after 48 hours is >3.0, and the average molding shrinkage in the perpendicular direction is >1.3; the average molding shrinkage in the parallel direction after 72 hours is >3.5, and the average molding shrinkage in the perpendicular direction is >1.7. By comparison, it can be seen that the overall molding shrinkage of the polyethylene resin compositions in the comparative examples is significantly greater than that of this application. It can be seen that the microscopic molecular structure of the polyethylene compositions prepared in Comparative Examples 1-10 is different from that of this application, and therefore, it is impossible to simultaneously achieve good stress crack resistance, rigidity-toughness balance, and low molding shrinkage in terms of performance.

[0235] Examples 1-12 of this application achieve excellent stress cracking resistance (ESCR), excellent rigidity-toughness balance, and low molding shrinkage by finely controlling the molecular chain microstructure of the polyethylene resin composition.

[0236] 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.

[0237] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0238] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A polyethylene resin composition, characterized in that, The polyethylene resin composition comprises ethylene homopolymer and ethylene-1-hexene copolymer; The crystallization elution fractionation (CEF) results of the polyethylene resin composition include: F1 (70~85℃) = 1~10%, F2 (50~65℃) = 1~5%; and, The soluble distribution width index (SDBI) of the polyethylene resin composition is 20–30 °C.

2. The polyethylene resin composition according to claim 1, characterized in that, The CEF results include: F1 (70-85℃) = 3-7%, F2 (50-65℃) = 2-4%; and SDBI = 23-26℃.

3. The polyethylene resin composition according to claim 1 or 2, characterized in that, The molecular weight distribution of the polyethylene resin composition simultaneously satisfies the following conditions: M w / M n = 10 to 20; M z / M w ≥ 4.0; M z+1 / M z ≥ 2.0; and lg(M 80 ) / lg(M 50 ) ≥ 1.125, lg(M 50 ) / lg(M 20 ) ≥1.135； Preferably, M w / M n =13~16; M z / M w ≥4.5; M z+1 / M z ≥2.5; and lg(M) 80 ) / lg(M 50 )≥1.135, lg(M 50 ) / lg(M 20 )≥1.140。 4. The polyethylene resin composition according to any one of claims 1 to 3, characterized in that, The content of the ethylene homopolymer in the polyethylene resin composition is 45-55 wt%; the content of the ethylene-1-hexene copolymer in the polyethylene resin composition is 45-55 wt%.

5. The polyethylene resin composition according to any one of claims 1 to 4, characterized in that, The density of the ethylene homopolymer is 0.965–0.970 g / cm³. 3 The preferred value is 0.965–0.968 g / cm³. 3 ; And / or, the density of the polyethylene resin composition is 0.955 to 0.965 g / cm³. 3 The preferred value is 0.958–0.962 g / cm³. 3 .

6. The polyethylene resin composition according to any one of claims 1 to 5, characterized in that, The melt mass flow rate of the ethylene homopolymer is 20–60 g / 10 min; preferably 40–55 g / 10 min; measurement conditions: temperature 190 °C, load 2.16 kg; And / or, the melt flow rate of the polyethylene resin composition is 2.5 to 4.0 g / 10 min; preferably 2.7 to 3.6 g / 10 min; measurement conditions: temperature 190°C, load 2.16 kg.

7. The polyethylene resin composition according to any one of claims 1 to 6, characterized in that, The molding shrinkage rate of the polyethylene resin composition after molding and cooling for 48 hours is ≤2.0 in the direction parallel to the melt flow and ≤0.8 in the direction perpendicular to the melt flow; preferably, the molding shrinkage rate of the polyethylene resin composition after molding and cooling for 48 hours is ≤1.5 in the direction parallel to the melt flow and ≤0.6 in the direction perpendicular to the melt flow. And / or, the molding shrinkage of the polyethylene resin composition after molding and cooling for 72 hours is ≤2.2 in the direction parallel to the melt flow and ≤1.0 in the direction perpendicular to the melt flow; preferably, the molding shrinkage of the polyethylene resin composition after molding and cooling for 72 hours is ≤1.8 in the direction parallel to the melt flow and ≤0.8 in the direction perpendicular to the melt flow.

8. The polyethylene resin composition according to any one of claims 1 to 7, characterized in that, The polyethylene resin composition has an ESCR of ≥400 hours; preferably, the ESCR is ≥600 hours.

9. The polyethylene resin composition according to any one of claims 1 to 8, characterized in that, The FNCT of the polyethylene resin composition is ≥30 hours; preferably, FNCT is ≥40 hours; measurement conditions: stress is 4.0 MPa, temperature is 80°C.

10. The polyethylene resin composition according to any one of claims 1 to 9, characterized in that, The notched impact strength of the simply supported beam of the polyethylene resin composition is ≥12.0 kJ / m. 2 Preferably, the notched impact strength of the simply supported beam is ≥15.0 kJ / m. 2 ; And / or, the tensile yield stress of the polyethylene resin composition is ≥22.0 MPa; preferably, the tensile yield stress of the polyethylene resin composition is ≥25.0 MPa; And / or, the nominal tensile strain at break of the polyethylene resin composition is ≥400%; preferably, the nominal tensile strain at break of the polyethylene resin composition is ≥550%.

11. A method for preparing a polyethylene resin composition according to any one of claims 1 to 10, characterized in that, include: Step S1: Ethylene I and hydrogen I are reacted I in the presence of catalyst I to obtain stream I containing ethylene homopolymer; wherein, the feed ratio of ethylene I to hydrogen I is 1 kg / h: (8.1 g / h ~ 15.0 g / h); Step S2: The feed stream I, ethylene II, hydrogen II, and 1-hexene are reacted in the presence of catalyst II to obtain feed stream II containing the ethylene homopolymer and the ethylene-hexene copolymer; wherein the feed ratio of ethylene II, hydrogen II, and 1-hexene is 1 kg / h:(0.5 g / h to 2.5 g / h):(101 g / h to 200 g / h); Step S3: Separate and dry the material II sequentially to obtain polymer powder, namely the polyethylene resin composition.

12. The method for preparing the polyethylene resin composition according to claim 11, characterized in that, In step S1, the feed ratio of ethylene I to hydrogen I is 1 kg / h: (10.0 g / h ~ 12.0 g / h); And / or, in step S2, the feed ratio of ethylene II, hydrogen II, and 1-hexene is 1 kg / h: (1.0g / h~2.0g / h): (120g / h~180g / h).

13. The method for preparing the polyethylene resin composition according to claim 11 or 12, characterized in that, The conditions for reaction I include: a reaction temperature of 80–95°C, a reaction pressure of 1.4–2.0 MPa, and a reaction time of 10–100 min; preferably, the conditions for reaction I include: a reaction temperature of 82–92°C, a reaction pressure of 1.5–1.9 MPa, and a reaction time of 20–40 min. And / or, the conditions for reaction II include: a reaction temperature of 85–100°C, a reaction pressure of 1.4–2.0 MPa, and a reaction time of 10–100 min; preferably, the conditions for reaction II include: a reaction temperature of 86–95°C, a reaction pressure of 1.5–1.9 MPa, and a reaction time of 20–40 min.

14. The method for preparing the polyethylene resin composition according to any one of claims 11 to 13, characterized in that, Catalyst I and catalyst II are Ziegler-Natta catalysts, respectively. And / or, catalyst I and catalyst II are used in combination with a co-catalyst, wherein the co-catalyst is a metallic alkyl aluminum compound; And / or, the system of reaction I contains an inert solvent; the inert solvent is an alkane solvent; preferably, the inert solvent is selected from at least one of pentane, hexane, heptane and octane; And / or, in step S3, the polyethylene resin composition, in addition to containing the polymer powder, also includes at least one of an antioxidant, an ultraviolet absorber, an antistatic agent, a slip agent, and a nucleating agent; And / or, reaction I is carried out in reactor I, reaction II is carried out in reactor II, and reactor I and reactor II are connected in series; reactor I and reactor II are slurry reactors respectively.

15. A bottle cap product, characterized in that, The material of the bottle cap product is the polyethylene resin composition according to any one of claims 1 to 10 or the polyethylene resin composition prepared by the preparation method according to any one of claims 11 to 14.

Images