Highly branched polyolefin modified plastic particles and methods for making same

Abstract

The application belongs to the field of high polymer modified materials, and provides a kind of high branched polyolefin modified plastic particles and a preparation method thereof.The application is designed by high branched ethylene octene copolymer melt branching, sodium benzoate interface pre-composite and polypropylene continuous phase melt blending, so that sodium benzoate is input with dispersed elastic phase and forms controllable interface distribution, and at the same time, hindered phenol antioxidant and phosphite antioxidant are used to stabilize the processing system, so as to realize the balance of structural integrity, heat resistance, processing fluidity and low migration, solve the problems of weakening of elastic phase, formation of hard polar micro area by nucleating component and deterioration of flow caused by interface restraint, and be suitable for injection molding processing, modified polypropylene products and continuous granulation.

Description

Technical Field

[0001] This invention relates to the field of polymer modified materials, specifically to a highly branched polyolefin modified plastic particle and its preparation method. Background Technology

[0002] Polypropylene (PP) is widely used in household appliance housings, automotive interiors, packaging containers, daily-use injection molded parts, and general industrial products due to its low density, ease of molding, moderate cost, and good chemical resistance. With the development of lightweight, thin-walled, and continuous production, modified PP materials not only need to maintain good processing flowability but also need to maintain structural integrity, dimensional stability, and batch consistency under impact loads, thermal environments, and long-term storage conditions. Especially in injection molding, melt flow, dispersion morphology, crystallization behavior, and oxidation stability collectively affect the appearance, warpage, heat distortion, and service reliability of the finished product. Therefore, developing modified PP particles that can balance elastic phase toughening, nucleation heat resistance, low-migration interface fixation, and a stable melt processing window is of great significance for improving the application range and industrial adaptability of polyolefin materials.

[0003] Existing polypropylene modification methods typically employ elastomers such as ethylene-octene copolymers to improve impact toughness, or nucleating components such as sodium benzoate to enhance crystal support and heat resistance. However, these methods can easily lead to conflicts in dispersion, interface, and processing window within the same system. Chinese patent CN102775616A discloses a method for improving the dispersibility of sodium benzoate nucleating agents in polypropylene. Its background section also mentions that existing solutions often improve dispersion by limiting the particle size of sodium benzoate, compounding nucleating agents, or introducing other components, but these methods still suffer from insufficient dispersibility of sodium benzoate itself and inadequate compatibility with polypropylene. For elastic phase-modified polypropylene, an excessive amount of elastic phase can weaken the crystal support of the continuous phase, while direct addition of nucleating components may form hard, polar microregions, making it difficult to simultaneously achieve structural integrity, heat resistance, processing fluidity, and low migration. Summary of the Invention

[0004] The purpose of this invention is to provide a highly branched polyolefin modified plastic particle and its preparation method, which solves the current pain point problem of the difficulty in achieving both elastic toughening and heat-resistant crystallization support in polypropylene, and the mutual constraint between processing fluidity and low migration interface fixation.

[0005] This invention constrains the elastic phase using a highly branched ethylene octene copolymer and allows sodium benzoate to be pre-composite into the continuous polypropylene phase via the interface, forming a controlled distribution on the surface of the dispersed elastic phase. This reduces the opposing effects of the elastic phase weakening crystal support and the hard agglomeration of nucleating components. At the same time, it utilizes a stable extrusion sequence to reduce the negative effect of interface migration on flowability.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A highly branched polyolefin modified plastic granule, said highly branched polyolefin modified plastic granule is made from raw materials, based on a total mass of 100 wt% of said raw materials used for final melt blending, said raw materials being composed of the following components, with polypropylene being the balance component to make up the total mass of said raw materials to 100 wt%: Polypropylene 81.00-94.70 wt%; Sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate 5.00-18.00 wt%; Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] 0.05-0.50 wt%; Tris(2,4-di-tert-butylphenyl) phosphite 0.05-0.50 wt%; The sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is obtained by melt precomposite of highly branched ethylene octene copolymer and sodium benzoate, and the highly branched ethylene octene copolymer is obtained by melt branching of ethylene octene copolymer, dicumyl peroxide and triallyl isocyanurate.

[0007] Furthermore, the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate forms a dispersed elastic phase in the polypropylene continuous phase. The D50 of the dispersed elastic phase, calculated by the cumulative distribution of the number of particles obtained from cross-sectional scanning electron microscopy images, is 0.30-1.50 μm, and the D90 is 0.80-3.50 μm.

[0008] Furthermore, the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is prepared through the following steps: A1. Provides highly branched ethylene octene copolymers; A2. The highly branched ethylene octene copolymer is mixed with sodium benzoate to obtain a mixture; A3. The mixture obtained in step A2 is subjected to melt precomposite to obtain melt precomposite; A4. The molten precomposite is devolatilized, cooled, and pelletized to obtain the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate.

[0009] Furthermore, in the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate prepared by steps A1-A4, the sodium benzoate content is 0.30-2.80 wt% based on the total mass of the intermediate, the gel fraction is 0.05-3.00 wt%, and the melt mass flow rate at 190℃ and 2.16 kg is 0.20-8.00 g / 10 min.

[0010] Furthermore, the highly branched ethylene octene copolymer in step A1 is prepared through the following steps: B1. Mix ethylene octene copolymer, dicumyl peroxide, triallyl isocyanurate, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite to obtain a premix; B2. The premix obtained in step B1 is subjected to reactive extrusion under nitrogen protection to obtain the reactive extrusion product; B3. The reaction extrusion product is devoured, cooled, and pelletized to obtain the highly branched ethylene octene copolymer; B4. Wherein, the gel fraction of the highly branched ethylene octene copolymer is 0.05-3.00wt%, the branching index is 0.65-0.95, and the melt mass flow rate at 190℃ and 2.16kg is 0.20-8.00g / 10min.

[0011] Furthermore, the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is prepared via a dry pre-coating and short-path melting route. The dry pre-coating and short-path melting route includes: mixing the prepared highly branched ethylene octene copolymer with sodium benzoate to form a pre-coated material; subjecting the pre-coated material to short-path melting compounding, devolatilization, cooling, and pelletizing to obtain the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate. The sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate obtained contains 0.45-1.90 wt% sodium benzoate, 0.05-2.50 wt% gel fraction, and 0.01-0.15 wt% water content.

[0012] Furthermore, the highly branched ethylene octene copolymer provided in step A1 is prepared by continuous segmented temperature-controlled reactive extrusion. The continuous segmented temperature-controlled reactive extrusion includes: plasticizing and mixing ethylene octene copolymer, dicumyl peroxide and triallyl isocyanurate, followed by a branching reaction; then adding pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite for mixing; and then performing devolatilization and pelletizing to obtain the highly branched ethylene octene copolymer. The obtained highly branched ethylene octene copolymer has a gel fraction of 0.05-2.50 wt% and a branching index of 0.70-0.92.

[0013] Furthermore, in the highly branched ethylene octene copolymer used to prepare the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate, the content of 1-octene structural units is 15.00-45.00 wt%, and the density is 855-890 kg / m³. 3 The gel fraction is 0.05-3.00 wt%.

[0014] Furthermore, the melt flow rate of the highly branched polyolefin modified plastic particles at 230°C and 2.16 kg is 3.00-35.00 g / 10 min.

[0015] This invention also discloses a method for preparing highly branched polyolefin modified plastic particles, comprising the following steps: S1. Provides sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate; S2. Polypropylene, the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite are premixed according to the above raw material composition ratio to obtain a premix; S3. The premixed material is melt-blended and extruded to obtain the extrudate; S4. The extrudate is subjected to devolatilization, cooling and pelletizing to obtain the highly branched polyolefin modified plastic pellets.

[0016] Further, in step S2, polypropylene is first premixed with the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate, and then pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite are added and mixed. The melt blending extrusion in step S3 employs segmented temperature control; In step S4, the extrudate is subjected to vacuum devolatilization and cooling.

[0017] Further, in step S1, the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is provided in the form of a masterbatch. The masterbatch includes the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate and polypropylene. The sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is included in the raw material composition ratio of step S2 according to its actual mass in the masterbatch, and the polypropylene in the masterbatch is included in the polypropylene usage of step S2. In the obtained highly branched polyolefin modified plastic particles, the sodium benzoate content derived from the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is 0.02-0.45 wt% based on the total mass of the obtained highly branched polyolefin modified plastic particles, and the interfacial coverage of sodium benzoate relative to the surface of the dispersed elastic phase is 20-75%.

[0018] Furthermore, when three batches of the highly branched polyolefin modified plastic granules are produced continuously, the inter-batch coefficient of variation of the melt mass flow rate of the three batches of products under the conditions of 230°C and 2.16kg does not exceed 10.00%, and the inter-batch coefficient of variation of the dispersed elastic phase D50 does not exceed 12.00%.

[0019] Furthermore, the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is a granular intermediate obtained by premixing, melt precompositeing, devolatilization, cooling and pelletizing highly branched ethylene octene copolymer and sodium benzoate. The amount of sodium benzoate used is 0.30-2.88 parts by mass relative to 100 parts by mass of highly branched ethylene octene copolymer. Sodium benzoate is in powder form and contacts the highly branched ethylene octene copolymer and is subsequently melt precomposite to form an elastic phase input material for melt blending with polypropylene.

[0020] Furthermore, in the preparation of the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate, the mixing process of the highly branched ethylene octene copolymer and sodium benzoate is carried out under nitrogen protection, the mixing temperature is 60-90℃, the mixing time is 5-20 min, and the resulting mixture enters the melt precomposite step.

[0021] Furthermore, the melt precomposite temperature of the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is 115-165℃, the residence time is 30-180s, and the screw speed is 80-300r / min; the melt precomposite material is devolatilized for 30-120s under an absolute pressure of 0.020-0.080MPa, and after cooling and pelleting, the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is obtained.

[0022] Furthermore, in preparing the highly branched ethylene octene copolymer, relative to 100 parts by mass of ethylene octene copolymer, the amount of dicumyl peroxide is 0.02-0.25 parts by mass, the amount of triallyl isocyanurate is 0.20-1.50 parts by mass, the amount of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is 0.02-0.15 parts by mass, and the amount of tris(2,4-di-tert-butylphenyl) phosphite is 0.02-0.15 parts by mass. The above components are premixed at 25-60°C for 3-15 min before entering the reactive extrusion step.

[0023] Furthermore, the reactive extrusion temperature of the highly branched ethylene octene copolymer is 150-205℃, the residence time is 60-180s, and the screw speed is 100-350r / min; the reactive extrusion product is devolatilized for 30-180s under an absolute pressure of 0.020-0.080MPa, and after cooling and pelletizing, the highly branched ethylene octene copolymer is obtained.

[0024] Furthermore, in the preparation of highly branched ethylene octene copolymer using continuous segmented temperature-controlled reactive extrusion, the first stage involves plasticizing and mixing the ethylene octene copolymer, dicumyl peroxide, and triallyl isocyanurate at 90-130℃ for 20-90s; the second stage involves branching at 160-195℃ for 40-120s; and the third stage involves adding pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite at 150-180℃ and mixing for 30-90s. Subsequently, the copolymer is devolatilized and pelletized under an absolute pressure of 0.020-0.080MPa to obtain the highly branched ethylene octene copolymer.

[0025] Furthermore, when preparing the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate using a dry pre-coating and short-path melt route, the amount of sodium benzoate used is 0.45-1.94 parts by mass relative to 100 parts by mass of the already prepared highly branched ethylene octene copolymer. The dry pre-coating is carried out at a temperature of 70-110℃ and a rotation speed of 300-1500 r / min for 5-25 min to form a pre-coated material. The pre-coated material is short-path melt-composite at 120-150℃ for 40-150 s, and then devolatilized at an absolute pressure of 0.030-0.090 MPa for 20-100 s. After cooling and pelletizing, the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is obtained.

[0026] Furthermore, in preparing highly branched polyolefin modified plastic particles, polypropylene and sodium benzoate are first premixed with a highly branched ethylene octene copolymer intermediate at the interface for 3-15 min, and then pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite are added and mixed for 2-10 min to obtain a premix for melt blending extrusion.

[0027] Furthermore, the melt temperature control value for melt blending extrusion of highly branched polyolefin modified plastic granules is 170-220℃, the residence time is 60-180s, and the screw speed is 150-500r / min; the melt blending extrusion adopts at least four temperature zones, the first zone temperature is 165-185℃, the second zone temperature is 180-205℃, the third zone temperature is 190-220℃, and the fourth zone temperature is 180-205℃; the extrudate is devolatilized for 20-120s under an absolute pressure of 0.020-0.090MPa, and then granulated after cooling at 15-40℃ to obtain highly branched polyolefin modified plastic granules with a particle size of 2.00-5.00mm and a moisture content of 0.01-0.20wt%.

[0028] Furthermore, when the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is provided in the form of masterbatch, the content of the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate in the masterbatch is 40.00-80.00 wt%, and the content of polypropylene is 20.00-60.00 wt%. When the masterbatch enters the premixing step, the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is calculated based on the actual mass of the intermediate in the masterbatch, and the polypropylene in the masterbatch is included in the total polypropylene calculation.

[0029] Furthermore, the D50 and D90 of the dispersed elastic phase were determined by image analysis. The test sample was a cross-sectional sample made of highly branched polyolefin modified plastic particles. The cross-sectional sample was subjected to liquid nitrogen embrittlement, and the embrittlement section was taken as the observation surface. The same cross-sectional preparation method, image acquisition conditions and image threshold recognition rules were used for the same set of comparative samples. The cross-sectional sample was observed by scanning electron microscopy, and the equivalent circle diameter of the dispersed elastic phase region was recorded to form a number particle size cumulative distribution. The equivalent circle diameters corresponding to the number particle size cumulative distribution reaching 50% and 90% were respectively used as D50 and D90. No less than 300 dispersed elastic phase regions were counted for each sample.

[0030] Furthermore, the branching index of the highly branched ethylene octene copolymer was determined using the GPC-MALS method. It was calculated as the ratio of the intrinsic viscosity of the branched ethylene octene copolymer at the same molecular weight to the intrinsic viscosity of a linear ethylene octene copolymer reference sample. The linear ethylene octene copolymer reference sample was a linear ethylene octene copolymer that had not undergone branching treatment with the addition of dicumyl peroxide and triallyl isocyanurate, and whose 1-octene structural unit content was the same as that of the ethylene octene copolymer used in the highly branched ethylene octene copolymer to be tested. The branching index of the same test sample was calculated using the same reference sample and the same GPC-MALS data processing caliber. The calculation formula is: g =[η]branching / [η]linearity; The obtained g The branching index is used as the indicator for highly branched ethylene octene copolymers.

[0031] Furthermore, the gel fraction was determined by solvent extraction. A sample of highly branched ethylene octene copolymer or sodium benzoate interfacial pre-composite highly branched ethylene octene copolymer intermediate was placed in a 200-mesh stainless steel mesh and extracted by reflux in boiling xylene for 24 hours. After drying and weighing, the gel fraction was calculated as the ratio of the mass of the insoluble matter to the initial mass of the sample for highly branched ethylene octene copolymer; for sodium benzoate interfacial pre-composite highly branched ethylene octene copolymer intermediate, the gel fraction was calculated as the ratio of the mass of the polymer insoluble matter after deducting sodium benzoate residue to the initial mass of the sample. The sodium benzoate residue was deducted based on the sodium element detection conversion result of the same sample.

[0032] Furthermore, the sodium benzoate content was determined using XRF or ICP-OES methods. The test samples included sodium benzoate interfacial pre-composite highly branched ethylene octene copolymer intermediates and highly branched polyolefin modified plastic particles. The sodium element signal was recorded and converted into sodium benzoate content. The sodium benzoate content in the intermediates was calculated based on the total mass of the intermediates, and the sodium benzoate content in the final particles was calculated based on the total mass of the highly branched polyolefin modified plastic particles.

[0033] Furthermore, the moisture content was determined using the Karl Fischer moisture determination method, and the obtained moisture content was the ratio of the mass of water to the mass of the sample to be tested. When used for determining the moisture content of intermediates, the sample to be tested was a sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate. When used for determining the moisture content of final particles, the sample to be tested was highly branched polyolefin modified plastic particles.

[0034] Furthermore, the interface coverage was calculated using the cross-sectional image of the dispersed elastic phase and the sodium element surface distribution map. The test sample was a cross-sectional sample of highly branched polyolefin modified plastic particles. During image analysis, the outer contour of the dispersed elastic phase and the sodium element signal region were identified. The sodium element signal region was identified using a threshold rule formed after subtracting the background signal of the blank matrix cross-section from the same batch. The same threshold identification rule and image resolution aperture were used for the same set of comparative samples, and the results were calculated according to the following formula: Interface coverage = (Length of the interface segment where the sodium element signal intersects the outer contour of the dispersed elastic phase / Total length of the outer contour of the dispersed elastic phase) × 100%; The obtained interface coverage is used to characterize the distribution of sodium benzoate relative to the surface of the dispersed elastic phase.

[0035] Furthermore, the inter-batch coefficient of variation is calculated based on the test values ​​of three batches of products for the same test item, using the following formula: CV = (Standard Deviation / Mean) × 100%; The tests used to calculate the batch-to-batch coefficient of variation (CV) include melt mass flow rate and dispersed elastic phase D50 at 230°C and 2.16 kg. The resulting CV serves as quality control data for the stability of continuous production.

[0036] Furthermore, after the highly branched polyolefin modified plastic granules were sealed and stored at 20-35℃ and 30-70% relative humidity for 30-180 days, the melt flow rate after storage was measured at 230℃ and 2.16 kg, and the change rate of melt flow rate after storage was calculated according to the following formula: Melt mass flow rate change rate = (|melt mass flow rate after storage - initial melt mass flow rate| / initial melt mass flow rate) × 100%; Furthermore, when highly branched polyolefin modified plastic particles are used in injection molding, the injection melt temperature is 180-230℃, the mold temperature is 20-70℃, and the holding time is 5-40s. The resulting injection molded products serve as one of the sample sources for testing the morphology of the dispersed elastic phase and the storage stability of the melt mass flow rate.

[0037] As a concept of this invention, the present invention employs a design of melt blending a sodium benzoate interfacial pre-composite highly branched ethylene octene copolymer intermediate with a continuous polypropylene phase, primarily to achieve a synergistic balance between structural integrity and heat resistance. In existing technologies, an ethylene octene copolymer elastic phase is typically introduced to improve the impact and structural integrity of polypropylene; however, an increased elastic phase weakens the crystalline support of the continuous polypropylene phase and reduces heat resistance retention. To improve heat resistance, nucleating components such as sodium benzoate are typically introduced; however, direct addition of nucleating components easily forms hard, polar microregions and reduces the uniformity of elastic phase dispersion. This invention constrains the flow and migration of the elastic phase through the highly branched ethylene octene copolymer and allows sodium benzoate to be pre-compositely introduced into the polypropylene system along with the elastic phase, thereby mitigating the dual side effects of elastic phase softening and nucleating component agglomeration. This achieves a balance between the performance that is difficult to achieve simultaneously with elastomer toughening or nucleation modification alone.

[0038] As another aspect of this invention, the present invention employs a pre-constructed sodium benzoate interfacial pre-composite highly branched ethylene octene copolymer intermediate followed by melt blending with polypropylene. This is primarily used to achieve, fix, or amplify the aforementioned synergistic effects. In existing direct blending processes, when the elastomer, nucleating component, and antioxidant simultaneously enter the polypropylene melt, the nucleating component easily forms uneven microregions in the continuous phase or local high-shear regions, while the elastic phase may deform or migrate under excessive shear, leading to mutual interference between heat resistance support and structural integrity. This invention, by first providing an interfacial pre-composite intermediate, then sequentially pre-blending polypropylene, the intermediate, and dual antioxidants, and fixing and dispersing the elastic phase and the sodium benzoate interfacial distribution during segmented temperature control, devolatilization, cooling, and pelletizing processes, ensures that interfacial fixation, melt flow, and antioxidant stability are coordinated and formed in the same continuous process, reducing the risks of phase separation and migration associated with single-step direct blending.

[0039] Highly branched ethylene octene copolymers primarily buffer structural damage to polypropylene systems during impact and molding shrinkage. However, when present alone or in excessively high proportions, they can weaken heat-resistant support due to softening of the elastic phase and decreased crystallization continuity. Sodium benzoate mainly promotes crystalline support and heat deformation retention in polypropylene, but when added alone or at excessively high local concentrations, it can easily form hard, polar microregions and reduce the uniformity of elastic phase dispersion. This invention involves pre-compositing sodium benzoate with the highly branched ethylene octene copolymer via melt melting before introducing it into the continuous polypropylene phase. Through proportion matching, interface distribution, and segmented melting sequence control, the buffering effect of the elastic phase does not significantly damage the crystalline support, and the nucleation effect of sodium benzoate does not concentrate and worsen structural integrity. Ultimately, this approach balances structural integrity, heat resistance, processing fluidity, and low migration.

[0040] Beneficial technical effects 1. Balancing structural integrity and heat resistance: By pre-introducing sodium benzoate into the highly branched ethylene octene copolymer to form an interfacial precomposite intermediate, the hard agglomeration of nucleating components in the continuous polypropylene phase is reduced, allowing the buffering effect of the elastic phase and the support of nucleation crystallization to be exerted simultaneously, thereby improving the shortcoming that toughening of the elastomer alone can easily reduce heat resistance.

[0041] 2. Improving the balance between processing fluidity and low migration: Highly branched ethylene octene copolymer provides moderate branching constraint, and sodium benzoate is distributed close to the interface of the dispersed elastic phase through pre-composite method, reducing the tendency of free migration caused by direct addition of powder, while maintaining the processable flow window through melt blending process.

[0042] 3. Improve the stability of continuous production: By designing the sequence of preparation of highly branched ethylene octene copolymer, sodium benzoate interfacial precomposite, polypropylene premixing and segmented temperature-controlled melt blending, the branching state, interfacial distribution, devolatilization and pelleting quality have a controllable path, which is beneficial to reduce the batch-to-batch melt mass flow rate and the particle size fluctuation of the dispersed elastic phase.

[0043] 4. Enhance the feasibility of instructions and the traceability of quality control: By defining the determination methods for D50, D90, gel fraction, branching index, sodium benzoate content, interface coverage, batch-to-batch coefficient of variation, and change rate of melt mass flow rate after storage, a detectable quality control chain is formed between composition, structure, processing, and performance. Attached Figure Description

[0044] Figure 1 The graph shows the effect of the amount of intermediate used in Example 1 on the notched Izod impact strength and heat distortion temperature.

[0045] Figure 2 The graph shows the effect of sodium benzoate content on heat distortion temperature and sodium benzoate migration rate in Example 1.

[0046] Figure 3The diagram shows the effect of the branching index on the notched Izod impact strength and MFR in Example 1.

[0047] Figure 4 The graph shows the effect of the final melt blending extrusion temperature on the notched Izod impact strength and the rate of change of MFR after storage in Example 1.

[0048] Figure 5 The diagram shows the particle size difference distribution of the dispersed elastic phase in Examples 1, 9, and 11.

[0049] Figure 6 The cumulative particle size distribution of the dispersed elastic phase in Examples 1, 9, and 11 is shown.

[0050] Figure 7 The scatter plots and mean ± SD of the interface coverage of Example 1, Comparative Example 9, and Comparative Example 11 are shown.

[0051] Figure 8 The scatter plots of sodium benzoate mobility versus mean ± SD for Examples 1, 10, and 11 are shown.

[0052] Figure 9 The final particulate sodium benzoate content of Example 1, Comparative Example 10, and Comparative Example 11 is shown as a scatter plot of the mean ± SD.

[0053] Figure 10 The GPC-MALS normalized RI chromatograms are for Example 1, Comparative Example 1, and Comparative Example 4.

[0054] Figure 11 The scatter plots of the branching index and the mean ± SD are for Example 1, Comparative Example 1, and Comparative Example 4.

[0055] Figure 12 Scatter plots showing the correlation between gel fraction and MFR for Examples 1, 4, and 5.

[0056] Figure 13 The graph shows the effect of storage time on the rate of change of MFR for Examples 1, 8, and 11.

[0057] Figure 14 Scatter plots of inter-batch coefficient of variation for Example 1, Comparative Example 8, and Comparative Example 11.

[0058] Figure 15 The DSC cooling crystallization heat flow diagrams are for Example 1, Comparative Example 9, and Comparative Example 11. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0060] Example 1

[0061] In this embodiment, 100.00 kg of highly branched polyolefin modified plastic granules were prepared, and the product form was cylindrical or near-cylindrical injection molding plastic granules. The raw materials, based on a total mass of 100.00 kg, included 94.70 kg of polypropylene, 5.00 kg of sodium benzoate interfacial pre-composite highly branched ethylene octene copolymer intermediate, 0.15 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 0.15 kg of tris(2,4-di-tert-butylphenyl) phosphite. The polypropylene was commercially available injection molding grade granules with a melt flow rate of 42 g / 10 min. The ethylene octene copolymer was commercially available granules with a 1-octene structural unit content of 15.00 wt% and a density of 890 kg / m³. 3 Moisture content ≤0.05wt%. Sodium benzoate is a commercially available powder with a purity ≥99.0% and a D50 of 8μm. Both antioxidants are commercially available industrial-grade powders with a purity ≥98.0%.

[0062] S1: Preparation of highly branched ethylene octene copolymer. 100.00 kg of ethylene octene copolymer, 0.02 kg of dicumyl peroxide, 0.20 kg of triallyl isocyanurate, 0.02 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 0.02 kg of tris(2,4-di-tert-butylphenyl) phosphite were added to a high-speed mixer and premixed for 3 min at 25°C, under nitrogen protection, and at a speed of 300 r / min. The premix was then added to a co-rotating twin-screw reactive extruder and reactive extruded at 150°C, with a residence time of 60 s and a screw speed of 100 r / min. Deviation was performed at an absolute pressure of 0.020 MPa at the barrel end for 30 s. The mixture was then cooled with circulating water at 20°C and pelletized to obtain the highly branched ethylene octene copolymer. The gel fraction of the highly branched ethylene octene copolymer in this embodiment was measured to be 0.05 wt%, the branching index was 0.95, and the melt mass flow rate at 190°C and 2.16 kg was 8.00 g / 10 min.

[0063] S2: Preparation of sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate. 100.00 kg of highly branched ethylene octene copolymer and 0.45 kg of sodium benzoate powder were added to a nitrogen-protected mixer and mixed for 5 min at 60°C and 200 r / min to obtain a mixture. The mixture was added to a short-path twin-screw extruder and precomposite at 115°C, residence time 30 s, and screw speed 80 r / min. Subsequently, it was devolatilized at an absolute pressure of 0.020 MPa for 30 s, cooled with water at 15°C, and pelletized to obtain a granular intermediate. The sodium benzoate content of the intermediate in this example, calculated based on the total mass of the intermediate, was 0.45 wt%, the gel fraction was 0.05 wt%, the melt flow rate at 190°C and 2.16 kg was 8.00 g / 10 min, and the water content was 0.01 wt%.

[0064] S3: Intermediates are provided in masterbatch form. Sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediates are pre-prepared into masterbatch with polypropylene at a ratio of 40.00 wt% and 60.00 wt%. The actual mass of the intermediates in the masterbatch is calculated as 5.00 kg and included in the raw material composition of this embodiment. The polypropylene in the masterbatch is included in the total polypropylene content. The pre-prepared masterbatch is melt-mixed at 170°C, a residence time of 60 s, a screw speed of 150 r / min, a devolatilization absolute pressure of 0.020 MPa, and a cooling water temperature of 15°C.

[0065] S4: Preparation of highly branched polyolefin modified plastic granules. First, polypropylene and masterbatch containing 5.00 kg of intermediates (calculated as a whole) were added to a mixer and premixed for 3 min at 25℃ and 250 r / min. Then, 0.15 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.15 kg of tris(2,4-di-tert-butylphenyl) phosphite were added, and mixing continued for 2 min at 25℃ and 250 r / min to obtain the premix. The premix was then fed into a co-rotating twin-screw extruder with four temperature zones of 165℃, 180℃, 190℃, and 180℃ respectively. The melt temperature for melt blending extrusion was controlled at 170℃, the residence time at 60 s, and the screw speed at 150 r / min. The extrudate was devolatilized for 20 seconds under an absolute pressure of 0.020 MPa, cooled with water at 15°C, and then pelletized to obtain highly branched polyolefin modified plastic granules with a particle size of 2.00 mm and a water content of 0.01 wt%.

[0066] Quality testing methods and results: The melt flow rate of the particles in this embodiment was measured at 230℃ and 2.16kg, and the result was 35.00g / 10min. The particles were injection molded into cross-sectional samples with an injection melt temperature of 180℃, a mold temperature of 20℃, and a holding time of 5s. After liquid nitrogen embrittlement, the samples were observed by scanning electron microscopy. The images showed no less than 300 dispersed elastic phase regions, and the measured D50 was 0.30μm and D90 was 0.80μm. The interface coverage was calculated by analyzing the sodium element surface distribution and the outer contour of the dispersed elastic phase, and the result was 20%. When three batches were produced continuously, the inter-batch coefficient of variation of melt flow rate was 3.20%, and the inter-batch coefficient of variation of D50 was 4.10%.

[0067] Features and application scenarios of this embodiment: This embodiment uses a higher polypropylene ratio, a lower intermediate input ratio and mild melt blending conditions, resulting in good particle flowability and a smaller dispersed elastic phase particle size. It is suitable for thin-wall injection molding, daily necessities, and polypropylene modification scenarios that are sensitive to molding cycles.

[0068] Example 2

[0069] Raw materials and proportions To prepare 100.00 kg of highly branched polyolefin modified plastic granules, the following materials were used: 81.00 kg of polypropylene, 18.00 kg of sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate, 0.50 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 0.50 kg of tris(2,4-di-tert-butylphenyl) phosphite. The polypropylene was commercially available injection-grade granules with a melt flow rate of 18 g / 10 min. The ethylene octene copolymer was commercially available granules with a 1-octene structural unit content of 45.00 wt% and a density of 855 kg / m³. 3 Moisture content ≤0.05wt%. Sodium benzoate is a commercially available powder with a purity ≥99.0% and a D50 of 12μm. Both antioxidants are commercially available industrial-grade powders with a purity ≥98.0%.

[0070] Preparation process of highly branched ethylene octene copolymer 100.00 kg of ethylene octene copolymer, 0.25 kg of dicumyl peroxide, 1.50 kg of triallyl isocyanurate, 0.15 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 0.15 kg of tris(2,4-di-tert-butylphenyl) phosphite were added to a closed mixer and premixed for 15 min at 60°C, under nitrogen protection, and at a speed of 500 r / min. The premix was then fed into a co-rotating twin-screw reactive extruder and reactive extruded at 205°C, a residence time of 180 s, and a screw speed of 350 r / min. The extruded material was then devolatilized at the end of the barrel under an absolute pressure of 0.080 MPa for 180 s, followed by water cooling at 25°C and pelleting to obtain the highly branched ethylene octene copolymer. The gel fraction of the highly branched ethylene octene copolymer in this embodiment was measured to be 3.00 wt%, the branching index was 0.65, and the melt mass flow rate at 190°C and 2.16 kg was 0.20 g / 10 min.

[0071] intermediate preparation process 100.00 kg of highly branched ethylene octene copolymer and 2.50 kg of sodium benzoate powder were mixed under nitrogen protection at a mixing temperature of 90°C for 20 min and a screw speed of 300 r / min. The resulting mixture was then fed into a melt pre-composite section and melt-composite at 165°C, a residence time of 180 s, and a screw speed of 300 r / min. Subsequently, it was devolatilized at an absolute pressure of 0.080 MPa for 120 s, cooled with water at 25°C, and pelletized to obtain a sodium benzoate interfacial pre-composite highly branched ethylene octene copolymer intermediate. The sodium benzoate content of the intermediate in this example, calculated based on the total mass of the intermediate, was 2.44 wt%, the gel fraction was 2.50 wt%, the melt flow rate at 190°C and 2.16 kg was 0.20 g / 10 min, and the water content was 0.12 wt%.

[0072] Masterbatch provides for final blending The intermediate is provided in masterbatch form, containing 80.00 wt% sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate and 20.00 wt% polypropylene. When the masterbatch enters the premixing step, the intermediate is converted to 18.00 kg based on its actual mass in the masterbatch, and the polypropylene in the masterbatch is included in the total polypropylene volume. First, the polypropylene is premixed with the masterbatch containing the converted 18.00 kg intermediate at 35°C and 300 rpm for 15 min. Then, 0.50 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.50 kg of tris(2,4-di-tert-butylphenyl) phosphite are added, and the mixture is mixed at 35°C and 300 rpm for 10 min. The premixed material was melt-blended and extruded in four temperature zones: 185℃, 205℃, 220℃, and 205℃ respectively. The melt temperature during melt-blending and extrusion was controlled at 220℃, the residence time was 180s, and the screw speed was 500r / min. The extrudate was devolatilized for 120s under an absolute pressure of 0.090MPa and then cooled at 40℃ before pelleting to obtain highly branched polyolefin modified plastic granules with a particle size of 5.00mm and a moisture content of 0.20wt%.

[0073] Quality testing methods and results The melt flow rate of the particles from this embodiment was measured at 230°C and 2.16 kg, and the result was 3.00 g / 10 min. Injection molding conditions were: melt temperature 230°C, mold temperature 70°C, and holding time 40 s. Scanning electron microscopy analysis of cross-sectional samples showed that at least 300 equivalent diameters of the dispersed elastic phase were counted, with D50 measured to be 1.50 μm and D90 to be 3.50 μm. XRF sodium elemental signal determination and verification using feed conversion values ​​showed that the sodium benzoate content derived from the intermediate in the particles was 0.44 wt%. Interface coverage was calculated using sodium elemental surface distribution, and the result was 75%. During three consecutive production batches, the inter-batch coefficient of variation for melt flow rate was 6.80%, and the inter-batch coefficient of variation for D50 was 7.60%.

[0074] Features of the solution in this embodiment This embodiment employs a higher proportion of intermediates, a higher amount of dual antioxidants, and stronger melt processing conditions. The dispersed elastic phase is located in a higher particle size region, resulting in higher interface coverage. It is suitable for modified polypropylene particles that require high impact buffering, interface fixation, and dispersion stability of the high-load elastic phase.

[0075] Example 3

[0076] I. Preparation Object and Key Parameters: This embodiment uses 100.00 kg of highly branched polyolefin modified plastic granules as the preparation object, employing 87.90 kg of polypropylene, 12.00 kg of sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate, 0.05 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 0.05 kg of tris(2,4-di-tert-butylphenyl) phosphite. The polypropylene is commercially available injection molding grade granules with a melt flow rate of 28 g / 10 min. The ethylene octene copolymer is commercially available granules with a 1-octene structural unit content of 30.00 wt% and a density of 872 kg / m³. 3 Moisture content ≤0.05wt%. Sodium benzoate is a commercially available powder with a purity ≥99.0% and a D50 of 10μm. Both antioxidants are commercially available industrial-grade powders with a purity ≥98.0%.

[0077] II. Preparation of highly branched ethylene octene copolymer by continuous segmented temperature-controlled reactive extrusion: 100.00 kg of ethylene octene copolymer, 0.18 kg of dicumyl peroxide, and 1.10 kg of triallyl isocyanurate were plasticized and mixed at 90°C for 20 s in the first stage, and then proceeded to the second stage for branching reaction at 195°C for 120 s. In the third stage, 0.08 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.08 kg of tris(2,4-di-tert-butylphenyl) phosphite were added and mixed at 180°C for 90 s. Then, the mixture was devolatilized under an absolute pressure of 0.080 MPa for 120 s and pelletized to obtain highly branched ethylene octene copolymer. The gel fraction of the highly branched ethylene octene copolymer in this embodiment was measured to be 2.50 wt%, the branching index was 0.70, and the melt mass flow rate at 190°C and 2.16 kg was 1.20 g / 10 min.

[0078] III. Preparation of Intermediate by Melt Precomposite: 100.00 kg of highly branched ethylene octene copolymer and 2.80 kg of sodium benzoate powder were mixed under nitrogen protection at a mixing temperature of 75°C for 12 min and a screw speed of 260 r / min. The mixture was then fed into a melt precomposite section and treated at 150°C, a residence time of 120 s, and a screw speed of 220 r / min. The melt-precomposite material was then devolatilized at an absolute pressure of 0.060 MPa for 90 s, cooled with water at 25°C, and pelletized to obtain the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate. The sodium benzoate content of the intermediate in this example, calculated based on the total mass of the intermediate, was 2.72 wt%, the gel fraction was 3.00 wt%, and the melt flow rate at 190°C and 2.16 kg was 1.20 g / 10 min.

[0079] IV. Melt Blending Extrusion and Pelletizing: First, premix 87.90 kg of polypropylene and 12.00 kg of intermediate at 30℃ and 280 r / min for 8 min. Then, add 0.05 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.05 kg of tris(2,4-di-tert-butylphenyl) phosphite, and mix at 30℃ and 280 r / min for 5 min. The premixed material is fed into a co-rotating twin-screw extruder with four temperature zones of 175℃, 195℃, 210℃, and 195℃ respectively. The melt temperature for melt blending extrusion is controlled at 195℃, the residence time is 120 s, and the screw speed is 320 r / min. The extrudate was devolatilized for 80 seconds under an absolute pressure of 0.060 MPa, cooled with water at 25°C, and then pelletized to obtain highly branched polyolefin modified plastic granules with a particle size of 3.20 mm and a water content of 0.08 wt%.

[0080] V. Quality Testing Methods and Results: The melt flow rate of the particles at 230℃ and 2.16kg was 18.00g / 10min. Injection molding sample preparation conditions were: melt temperature 205℃, mold temperature 45℃, and holding time 22s. Cross-sectional scanning electron microscopy image analysis revealed that the D50 of the dispersed elastic phase was 0.92μm and the D90 was 2.10μm. XRF sodium elemental signal determination, verified by the feed conversion value, showed that the sodium benzoate content derived from the intermediate in the particles was 0.33wt%; the calculated sodium elemental surface distribution yielded an interface coverage of 58%. During three consecutive production batches, the inter-batch coefficient of variation for melt flow rate was 4.90%, and the inter-batch coefficient of variation for D50 was 5.80%.

[0081] VI. Process characteristics and application directions of this embodiment: This embodiment uses a continuous segmented temperature-controlled reactive extrusion method to construct highly branched ethylene octene copolymers and uses a low amount of dual antioxidants, which is suitable for investigating the preparation of polypropylene modified particles under continuous process window, dispersion morphology and low additive stability system.

[0082] Example 4

[0083] Highly branched polyolefin modified plastic granules were prepared using the following continuous process. First, commercially available ethylene-octene copolymer granules were selected as the elastic phase base material, with a 1-octene structural unit content of 38.00 wt% and a density of 865 kg / m³. 3The moisture content was ≤0.05wt%. 100.00 kg of ethylene octene copolymer, 0.10 kg of dicumyl peroxide, and 0.80 kg of triallyl isocyanurate were added to a continuous mixing section and plasticized at 130°C for 90 s; subsequently, a branching reaction was carried out at 160°C for 40 s; then, 0.15 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.15 kg of tris(2,4-di-tert-butylphenyl) phosphite were added, and the mixture was mixed at 150°C for 30 s, followed by devolatilization at an absolute pressure of 0.020 MPa for 60 s. After cooling with water at 20°C and pelletizing, a highly branched ethylene octene copolymer was obtained. The gel fraction of the highly branched ethylene octene copolymer in this example was measured to be 0.05wt%, the branching index was 0.92, and the melt flow rate at 190°C and 2.16 kg was 6.50 g / 10 min.

[0084] Subsequently, an intermediate was prepared using a dry pre-coating and short-path melt route. 100.00 kg of the previously prepared highly branched ethylene octene copolymer and 1.90 kg of sodium benzoate powder (purity ≥99.0%, D50 6 μm) were fed into a dry coating apparatus. Dry pre-coating was performed at 110℃ and 1500 r / min for 25 min to form a pre-coated material. The pre-coated material was then short-path melt-composite at 150℃ for 150 s, followed by devolatilization at an absolute pressure of 0.090 MPa for 100 s. After water cooling at 20℃ and pelletizing, the sodium benzoate interfacial pre-composite highly branched ethylene octene copolymer intermediate was obtained. The sodium benzoate content of the intermediate in this embodiment was measured to be 1.86 wt% based on the total mass of the intermediate, the gel fraction was 2.50 wt%, the water content was 0.15 wt%, and the melt mass flow rate at 190°C and 2.16 kg was 2.40 g / 10 min.

[0085] The final blending stage was calculated based on 100.00 kg of product, using 87.00 kg of polypropylene, 12.50 kg of sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate, 0.25 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 0.25 kg of tris(2,4-di-tert-butylphenyl) phosphite. The polypropylene and intermediate were premixed for 10 min at 32℃ and 300 rpm, then two antioxidants were added, and the mixture was mixed for 6 min at 32℃ and 300 rpm. The premixed material was fed into a twin-screw extruder with four temperature zones: 185℃, 190℃, 220℃, and 180℃. The melt temperature for melt blending extrusion was controlled at 205℃, the residence time at 150 s, and the screw speed at 420 rpm. The extrudate was devolatilized for 50 seconds under an absolute pressure of 0.040 MPa and then granulated after cooling at 30°C to obtain highly branched polyolefin modified plastic granules with a particle size of 4.00 mm and a water content of 0.12 wt%.

[0086] During quality testing, the melt flow rate of the particles from this embodiment was measured at 230°C and 2.16 kg, yielding a result of 10.50 g / 10 min. Injection molding conditions were: melt temperature 220°C, mold temperature 60°C, and holding time 30 s. Cross-sectional scanning electron microscopy image analysis revealed a dispersed elastic phase D50 of 1.20 μm and a D90 of 2.80 μm. ICP-OES analysis of sodium content, verified by conversion from feed values, showed a sodium benzoate content of 0.23 wt% derived from the intermediate in the particles. Sodium surface distribution calculations yielded an interface coverage of 64%. During three consecutive production batches, the inter-batch coefficient of variation for melt flow rate was 9.80%, and the inter-batch coefficient of variation for D50 was 11.80%.

[0087] The applicable scenarios for this embodiment are as follows: This embodiment adopts a dry pre-coating and short-path melting route, combined with a continuous segmented temperature-controlled branching method, which is suitable for the production of modified polypropylene granules that require reducing the thermal history of intermediates and taking into account the interface distribution and batch stability.

[0088] Comparative Example 1: Basically the same as Example 1, except that the highly branched ethylene octene copolymer was replaced with an unbranched ethylene octene copolymer. The unbranched ethylene octene copolymer had a 1-octene structural unit content of 15.00 wt% and a density of 890 kg / m³. 3 The product did not undergo melt branching treatment with dicumyl peroxide and triallyl isocyanurate. The complete and unchanged conditions were as follows: 94.70 kg of polypropylene, 5.00 kg of sodium benzoate interfacial pre-composite ethylene-octene copolymer intermediate, 0.15 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 0.15 kg of tris(2,4-di-tert-butylphenyl) phosphite; sodium benzoate content 0.45 wt%; intermediate melt pre-composite temperature 115℃, residence time 30 s, screw speed 80 r / min; final four-stage temperature zones 165℃, 180℃, 190℃, and 180℃, residence time 60 s, screw speed 150 r / min, devolatilization absolute pressure 0.020 MPa, and cooling water temperature 15℃.

[0089] Comparative Example 2: Essentially the same as Example 1, except that the amount of sodium benzoate interfacial pre-composite highly branched ethylene octene copolymer intermediate was 3.50 kg, and the amount of polypropylene was adjusted to 96.20 kg. The unchanging conditions are fully listed as follows: pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] 0.15 kg, tris(2,4-di-tert-butylphenyl) phosphite 0.15 kg; melt flow rate of 8.00 g / 10 min at a gel fraction of 0.05 wt%, a branching index of 0.95, 190 °C, and 2.16 kg; sodium benzoate intermediate content of 0.45 wt%; final four-stage temperature zones of 165 °C, 180 °C, 190 °C, and 180 °C; residence time of 60 s; screw speed of 150 r / min; devolatilization absolute pressure of 0.020 MPa; and cooling water temperature of 15 °C.

[0090] Comparative Example 3: Essentially the same as Example 1, except that the amount of sodium benzoate interfacial pre-composite highly branched ethylene octene copolymer intermediate was 21.00 kg, and the amount of polypropylene was adjusted to 78.70 kg. The unchanging conditions are fully listed as follows: pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] 0.15 kg, tris(2,4-di-tert-butylphenyl) phosphite 0.15 kg; melt flow rate of 8.00 g / 10 min under the following conditions: gel fraction of highly branched ethylene octene copolymer 0.05 wt%, branching index 0.95, 190 °C, and 2.16 kg; sodium benzoate intermediate content 0.45 wt%; final four-stage temperature zones: 165 °C, 180 °C, 190 °C, and 180 °C; residence time 60 s; screw speed 150 r / min; devolatilization absolute pressure 0.020 MPa; and cooling water temperature 15 °C.

[0091] Comparative Example 4: Essentially the same as Example 1, except that dicumyl peroxide was not added during the preparation of the highly branched ethylene-octene copolymer, and the amount of triallyl isocyanurate remained at 0.20 kg. The complete, unchanged conditions were as follows: 100.00 kg of ethylene-octene copolymer, 0.02 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.02 kg of tris(2,4-di-tert-butylphenyl) phosphite, premixed at 25°C under nitrogen protection for 3 min, reactive extruded at 150°C for 60 s, and with a screw speed of 100 r / min; the intermediate sodium benzoate content was 0.45 wt%; the final raw materials were 94.70 kg of polypropylene, 5.00 kg of the intermediate, and 0.15 kg each of the two antioxidants; the final four-stage temperature zones were 165°C, 180°C, 190°C, and 180°C, with a residence time of 60 s and a screw speed of 150 r / min.

[0092] Comparative Example 5: Essentially the same as Example 1, except that the amount of triallyl isocyanurate used in preparing the highly branched ethylene-octene copolymer was 0.05 kg, and the amount of dicumyl peroxide was maintained at 0.02 kg. The complete, unchanged conditions are as follows: 100.00 kg of ethylene-octene copolymer, 0.02 kg each of the two antioxidants, premixed at 25°C under nitrogen protection for 3 min, reactive extrusion at 150°C for 60 s, screw speed 100 r / min, devolatilization absolute pressure 0.020 MPa; sodium benzoate intermediate content 0.45 wt%; final raw materials: 94.70 kg of polypropylene, 5.00 kg of intermediate, and 0.15 kg each of the two antioxidants; final four-stage temperature zones: 165°C, 180°C, 190°C, and 180°C, residence time 60 s, screw speed 150 r / min.

[0093] Comparative Example 6: Basically the same as Example 1, except that the sodium benzoate content in the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is 0.05 wt%. The conditions, without change, are as follows: 94.70 kg of polypropylene, 5.00 kg of intermediate, 0.15 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 0.15 kg of tris(2,4-di-tert-butylphenyl) phosphite; melt flow rate of 8.00 g / 10 min under the conditions of 0.05 wt% gel fraction, 0.95 branching index, 190 °C, and 2.16 kg of highly branched ethylene octene copolymer; intermediate melt precomposite temperature of 115 °C, residence time of 30 s, and screw speed of 80 r / min; and final four temperature zones of 165 °C, 180 °C, 190 °C, and 180 °C, with a residence time of 60 s.

[0094] Comparative Example 7: Basically the same as Example 1, except that the sodium benzoate content in the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is 3.50 wt%. The unaltered conditions are as follows: 94.70 kg of polypropylene, 5.00 kg of intermediate, 0.15 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 0.15 kg of tris(2,4-di-tert-butylphenyl) phosphite; melt flow rate of 8.00 g / 10 min under the conditions of 0.05 wt% gel fraction, 0.95 branching index, 190 °C, and 2.16 kg of highly branched ethylene octene copolymer; intermediate melt precomposite temperature of 115 °C, residence time of 30 s, and screw speed of 80 r / min; and final four temperature zones of 165 °C, 180 °C, 190 °C, and 180 °C, with a residence time of 60 s.

[0095] Comparative Example 8: Basically the same as Example 1, except that the final melt temperature control value of the melt blend extrusion is 230℃, and the four temperature zones are 190℃, 220℃, 230℃ and 220℃ respectively. The unchanged conditions are fully listed as follows: polypropylene 94.70kg, intermediate 5.00kg, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] 0.15kg, tris(2,4-di-tert-butylphenyl) phosphite 0.15kg; highly branched ethylene octene copolymer gel fraction 0.05wt%, branching index 0.95; sodium benzoate content of intermediate 0.45wt%; final melt blend residence time 60s, screw speed 150r / min, devolatilization absolute pressure 0.020MPa, cooling water temperature 15℃.

[0096] Comparative Example 9: Basically the same as Example 1, except that sodium benzoate is not added to the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate, and only highly branched ethylene octene copolymer is used to make a particulate elastic phase intermediate. The complete, unmodified conditions were as follows: 94.70 kg of polypropylene, 5.00 kg of particulate elastic phase intermediate, 0.15 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 0.15 kg of tris(2,4-di-tert-butylphenyl) phosphite; melt flow rate of 8.00 g / 10 min at a gel fraction of 0.05 wt%, a branching index of 0.95, 190 °C, and a weight of 2.16 kg; elastic phase intermediate treatment temperature of 115 °C, residence time of 30 s, and screw speed of 80 r / min; and final four-stage temperature zones of 165 °C, 180 °C, 190 °C, and 180 °C, with a residence time of 60 s and a screw speed of 150 r / min. This comparative example was used to investigate the synergistic relationship between the highly branched ethylene octene copolymer and sodium benzoate.

[0097] Comparative Example 10: Essentially the same as Example 1, except that the highly branched ethylene octene copolymer was not added, and sodium benzoate was directly added to the polypropylene in 0.02 kg powder form, with the polypropylene dosage adjusted to 99.68 kg. The unchanging conditions are as follows: pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] 0.15 kg, tris(2,4-di-tert-butylphenyl) phosphite 0.15 kg; sodium benzoate was a commercially available powder with a purity ≥99.0%; the final four-stage temperature zones were 165°C, 180°C, 190°C, and 180°C; the melt blending residence time was 60 s; the screw speed was 150 r / min; the devolatilization absolute pressure was 0.020 MPa; and the cooling water temperature was 15°C. This comparative example was used to investigate the synergistic relationship between the highly branched ethylene octene copolymer and sodium benzoate.

[0098] Comparative Example 11: Basically the same as Example 1, except that the melt pre-composite step of sodium benzoate and highly branched ethylene octene copolymer was omitted. Instead, 4.98 kg of highly branched ethylene octene copolymer particles and 0.02 kg of sodium benzoate powder were directly pre-mixed with polypropylene and then melt-blended. The complete, unmodified conditions were as follows: 94.70 kg of polypropylene, 5.00 kg of highly branched ethylene octene copolymer and sodium benzoate combined, 0.15 kg of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 0.15 kg of tris(2,4-di-tert-butylphenyl) phosphite; the melt flow rate was 8.00 g / 10 min under the following conditions: gel fraction of 0.05 wt%, branching index of 0.95, 190 °C, and 2.16 kg of highly branched ethylene octene copolymer; the final four-stage temperature zones were 165 °C, 180 °C, 190 °C, and 180 °C; residence time was 60 s; screw speed was 150 r / min; devolatilization absolute pressure was 0.020 MPa; and cooling water temperature was 15 °C. This comparative example was used to investigate the effect of the interfacial precomposite sequence on the synergistic relationship between the highly branched ethylene octene copolymer and sodium benzoate.

[0099] Characterization and performance testing: Melt flow rate (MFR) tests were conducted on the highly branched polyolefin modified plastic granules of Examples 1-4 and all comparative examples to evaluate processing fluidity and flow retention capacity after storage. Following the method for determining the MFR of thermoplastics in ISO 1133-1:2022, dried granules were tested at 230°C and 2.16 kg. The extrusion mass was recorded over 10 minutes using Procedure A gravimetric method. Data fields include the average MFR, standard deviation of MFR, average rate of change of MFR after storage, and standard deviation of rate of change of MFR after storage, in units of g / 10 min and %. A lower rate of change in MFR within the target window indicates better flow stability.

[0100] Izod impact strength testing was performed on notched injection-molded specimens to evaluate the contribution of dispersed elasticity to structural integrity. Specimens were prepared according to the Izod impact strength test method for plastics specified in ISO 180:2023. Specimens were prepared from granules under uniform injection molding conditions. After notching, the specimens were conditioned for 24 hours at 23°C and 50% relative humidity, and then measured using a pendulum impact tester (n=5). The data fields are the mean and standard deviation of the notched Izod impact strength, in kJ / m². 2 A higher value indicates better structural integrity and impact resistance.

[0101] The purpose of heat distortion temperature testing on injection-molded strip specimens is to evaluate their heat retention capacity after the introduction of nucleation support and elastic phase. Following the method for testing the temperature of deformation under load in plastics as described in ISO 75-2:2013, a bending stress of 0.45 MPa was applied at a heating rate of 120 °C / h, and the temperature at which the specified deflection was reached was recorded. The average and standard deviation of the heat distortion temperature were obtained, in °C; higher values ​​indicate better heat distortion resistance.

[0102] The flexural properties of injection-molded specimens were tested to evaluate the stiffness-toughness balance between the continuous crystalline support of the polypropylene phase and the dispersion of the elastic phase. Following the three-point bending test method for rigid and semi-rigid plastics in ISO 178:2019, the specimens were conditioned for 24 hours at 23°C and 50% relative humidity. The span and loading speed were set according to the specimen thickness, with n=5. The experiment yielded the average and standard deviation of the flexural modulus, expressed in MPa. The values ​​are reasonably high and, together with the impact strength, contribute to the evaluation of structural integrity.

[0103] The morphology and interfacial coverage of the dispersed elastic phase in the injection-molded particulate cross-section were analyzed to quantify the distribution of D50, D90, and sodium benzoate relative to the surface of the dispersed elastic phase. The samples were subjected to liquid nitrogen embrittlement and gold sputtering. The cross-section was observed using a scanning electron microscope, and the equivalent circle diameters of at least 300 dispersed elastic phase regions were statistically analyzed. Simultaneously, the surface distribution of sodium was acquired, and the outer contour of the dispersed elastic phase and the sodium element signal line segments were identified to calculate the interfacial coverage. Data fields include D50, D90, mean and standard deviation of interfacial coverage, in μm and %.

[0104] The sodium benzoate content and migration rate of intermediates and final particles were tested to evaluate the support of interfacial pre-complexation for low migration. After ashing or digestion, samples were analyzed using XRF or ICP-OES to record sodium elemental signals and convert them to sodium benzoate content. For migration rate testing, extraction was performed at 70℃ using either xylene or isooctane for 2 hours. For the same set of comparative samples, the same extraction medium and sample mass to extract volume ratio were used. Sodium elemental content in the extract was measured and converted to sodium benzoate migration mass. Sodium benzoate migration rate was calculated using the following formula: Sodium benzoate migration rate = (Mass of sodium benzoate converted from extract / Initial sodium benzoate mass in test sample) × 100%. Data fields include the average sodium benzoate content, average sodium benzoate migration rate, and standard deviation, in wt% and %, respectively. A lower migration rate indicates better interfacial fixation.

[0105] DSC crystallization behavior testing was performed on the final particles to evaluate the effect of sodium benzoate interfacial distribution on the support of polypropylene crystallization. Following the methods of ISO 11357-1:2023 and ISO 11357-3:2025 for the determination of DSC, melting and crystallization temperatures and enthalpies of plastics, 5-10 mg samples were taken and heated / cooled at a rate of 10 °C / min under a nitrogen atmosphere. The crystallization peak temperature and enthalpy were recorded. The data fields are the average crystallization peak temperature, the average crystallization enthalpy, and the standard deviation, in °C and J / g. The values ​​are used to interpret differences in heat resistance.

[0106] Figure 1 This figure shows the effect of the intermediate dosage on the notched Izod impact strength and heat distortion temperature. Based on Example 1, the intermediate dosage was changed and the polypropylene dosage was adjusted accordingly, while other factors such as the highly branched ethylene octene copolymer, sodium benzoate content, branching control conditions, and melt blending process remained consistent. The intermediate dosage varied from approximately 3.50 wt% to 21.00 wt%. Figure 1 It can be seen that as the amount of intermediate increases, the notched Izod impact strength of the material generally shows an increasing trend, indicating that the intermediate can effectively improve the interfacial bonding between the elastic phase and the continuous phase of polypropylene. At the same time, the heat distortion temperature does not decrease continuously with the increase of toughening component, but remains at a high level in the moderate dosage range, indicating that the addition of intermediate can maintain a certain crystal support effect while enhancing impact toughness, thereby alleviating the problem of decreased heat resistance caused by conventional elastic toughening of polypropylene. Figure 2 This figure shows the effect of sodium benzoate content in the intermediate of this invention on the heat distortion temperature and sodium benzoate migration rate. The figure is based on Example 1, with only the sodium benzoate content in the intermediate changed from approximately 0.05 wt% to 3.50 wt%, while the other basic formulations and processing conditions remained consistent. The results show that when the sodium benzoate content is too low, its effect on increasing the heat distortion temperature is limited; when the content is too high, it may increase the risk of migration or local enrichment. Within a suitable content range, the material can simultaneously exhibit a high heat distortion temperature and a low migration rate, indicating that sodium benzoate does not simply achieve nucleation enhancement by increasing its addition amount, but rather needs to play a role through interfacial pre-composite and controlled distribution, thereby improving heat-resistant crystallization support and reducing the tendency for outward migration.

[0107] Figure 3 This figure shows the effect of the branching index on the notched Izod impact strength and MFR of the present invention. Based on Example 1, only the branching degree of the highly branched ethylene octene copolymer is varied, with the branching index g... The value changed from approximately 0.58 to 1.00, while the rest of the formulation and blending process remained consistent. Figure 3It is evident that when the branching index is in a moderately decreasing range, the material exhibits high notched Izod impact strength, while the melt flow rate (MFR) remains within a suitable processing range. Insufficient branching results in weak interfacial constraint of the elastic phase and limited toughening effect. Excessive branching can restrict melt flow. These results indicate that highly branched structures can effectively constrain the elastic phase, but this needs to be controlled within a reasonable range to achieve a balance between interfacial stability, impact toughening, and melt flow. Figure 4 This figure illustrates the effect of the final melt blending extrusion temperature on the notched Izod impact strength and the rate of change of MFR after storage. Based on Example 1, only the final melt blending extrusion temperature was varied from approximately 160°C to 230°C, while the other raw material ratios, pre-compounding steps, and extrusion sequence remained consistent. The results show that at a suitable extrusion temperature, the material exhibits higher impact strength and a lower rate of change of MFR after storage. Lower temperatures result in insufficient interfacial compounding and dispersion, while higher temperatures may lead to localized structural loosening or increased thermal history. This indicates that a stable extrusion temperature window helps maintain the spatial correlation between the highly branched elastic phase, sodium benzoate, and the continuous polypropylene phase, reducing the negative impact of interfacial migration on subsequent flow stability.

[0108] Figure 5 The following are particle size difference distribution diagrams of the dispersed elastic phases in Examples 1, 9, and 11. Figure 6 The cumulative particle size distribution of the dispersed elastic phase in Examples 1, 9, and 11 is shown. Figure 5 Using the equivalent circle diameter as the abscissa and the frequency density as the ordinate, it is used to compare the particle size concentration of the dispersed elastic phase in different systems. Figure 6 The cumulative distribution further reflects the particle size changes corresponding to D50 and D90. Figure 5 and Figure 6 It can be seen that the main peak of the dispersed elastic phase in Example 1 is located in the smaller particle size region and is more concentrated. A high cumulative proportion can be achieved at a smaller equivalent circle diameter, indicating that its D50 and D90 are lower than those of the comparative sample. In contrast, the particle size distribution of Comparative Examples 9 and 11 is wider and shifts towards larger particle sizes, indicating that the elastic phase is more prone to aggregation or coarsening. These results demonstrate that by constraining the elastic phase with highly branched ethylene octene copolymer and combining it with sodium benzoate interfacial precomposite treatment, the size of the elastic phase can be effectively refined, reducing the separation of coarse phases and providing a structural basis for improving the impact toughness of the material from a microscopic dispersion perspective.

[0109] Figure 7This is a scatter plot of the interface coverage of Example 1, Comparative Example 9, and Comparative Example 11, showing the mean ± SD. This plot illustrates the coverage of sodium benzoate or sodium-containing regions near the interface of the dispersed elastic phase through multiple test results and standard deviations. The results show that the interface coverage of Example 1 is significantly higher than that of Comparative Example 9 and Comparative Example 11, and the test data exhibits less dispersion, indicating that the interface pre-composite method used in this invention enables sodium benzoate to form a more stable and uniform controlled distribution near the outer contour of the dispersed elastic phase. Figure 8 The above is a scatter plot of the sodium benzoate migration rate versus mean ± SD for Examples 1, 10, and 11. Figure 9 The image shows a scatter plot of the final sodium benzoate content in particles of Example 1, Comparative Example 10, and Comparative Example 11, along with the mean ± SD. Figure 8 It can be seen that the migration rate of sodium benzoate in Example 1 is significantly lower than that in Comparative Examples 10 and 11, indicating that interfacial pre-composite and highly branched phase confinement can reduce the tendency of sodium benzoate to migrate outward; while Figure 9 The results show that the total sodium benzoate content in the final particles of each sample is basically the same, indicating that the difference in migration rate is not caused by the difference in total addition amount, but mainly depends on the spatial distribution and interfacial fixation of sodium benzoate in the system. Figures 7 to 9 The evidence corroborates each other, demonstrating that the present invention does not rely solely on the addition of nucleating agents, but rather achieves a nucleation enhancement effect with low migration and high stability through interface positioning and dispersion control, thereby reconciling the contradiction between heat-resistant support and interface fixation.

[0110] Figure 10 The following are GPC-MALS normalized RI chromatograms for Example 1, Comparative Example 1, and Comparative Example 4. Figure 11 The scatter plots of the branching index and the mean ± SD are for Example 1, Comparative Example 1, and Comparative Example 4. Figure 10 The elution volume was plotted on the x-axis and the normalized RI signal on the y-axis to reflect the molecular chain structure and molecular weight distribution of the sample. Example 1 showed a relatively stable peak shape and a reasonable broad peak distribution, while the comparative sample showed peak position or shape shifts, indicating that different structural modulation methods can affect the chain structure state of the material. Figure 11 Further, it is shown that the branching index g of Example 1 It is in the moderately decreasing range, while Comparative Examples 1 and 4 are closer to linear structural characteristics or insufficient branching regulation. (Combined) Figure 10 and Figure 11 It is evident that a moderately branched structure can enhance the constraint of the elastic phase on the interfacial region and improve the stable dispersion of the elastic phase in the continuous polypropylene phase, thus supporting the aforementioned results of particle size refinement, improved interfacial coverage, and enhanced impact performance at the molecular structure level.

[0111] Figure 12The scatter plot shows the correlation between gel fraction and melt flow rate (MFR) for Examples 1, 4, and 5. The plot uses gel fraction as the x-axis and MFR as the y-axis to evaluate the relationship between structural stability and melt flowability. The results show that Example 1 maintains a suitable MFR even at a low gel fraction, indicating that the present invention achieves structural stability through controlled branching and interfacial precompositeing, without relying on excessive crosslinking or high gel content to fix the system. In contrast, Comparative Examples 4 and 5 exhibit a mismatch between flowability and structural stability, potentially resulting in insufficient structure leading to loose interfaces or excessive structure restricting processing flow. This demonstrates that the present invention can maintain good processing flowability while avoiding excessive gelation, thus addressing the problem of "mutual constraint between processing flowability and low-migration interface fixation."

[0112] Figure 13 This is a graph showing the effect of storage time on the rate of change of MFR for Examples 1, Comparative Example 8, and Comparative Example 11. The graph plots storage time on the x-axis and the rate of change of MFR on the y-axis, displaying the trend of mean ± SD. The storage time covers 0 to 180 days. The results show that Example 1 has a lower rate of change of MFR throughout the storage process, while Comparative Example 8 and Comparative Example 1 show more significant changes with prolonged storage time. This indicates that the particles obtained by this invention have better melt flow stability during storage, and lower levels of interfacial component migration, phase rearrangement, or structural loosening. Figure 14 The figure shows the batch-to-batch coefficient of variation scatter plots for Example 1, Comparative Example 8, and Comparative Example 11. This plot also displays the batch-to-batch CV of MFR and the batch-to-batch CV of D50. The results show that Example 1 has low batch-to-batch CVs of both MFR and D50, indicating good batch-to-batch repeatability in melt flowability and dispersed elastic phase particle size. In contrast, the comparative sample exhibits greater fluctuations, suggesting that without a stable pre-compounding and extrusion sequence, interface fixation and phase dispersion are more susceptible to process fluctuations. Figure 13 and Figure 14 This invention not only improves the performance of single-batch materials, but also enhances storage stability and preparation repeatability, making it suitable for the stable preparation of highly branched polyolefin modified plastic particles.

[0113] Figure 15 The following are DSC cooling crystallization heat flow plots for Examples 1, 9, and 11. The plots, with temperature on the x-axis and heat flow on the y-axis, compare the cooling crystallization behavior of different samples. Example 1 exhibits a clearer and more concentrated exothermic crystallization peak, indicating that sodium benzoate, after interfacial pre-composite bonding, can effectively induce crystallization in the continuous polypropylene phase and mitigate the weakening of crystal support caused by the addition of the elastic phase. The broader or weaker crystallization peaks in Comparative Examples 9 and 11 indicate that uneven distribution of nucleating components or coarsening of the elastic phase reduces the consistency of crystallization behavior. These results are consistent with... Figure 1 and Figure 2The corresponding change in heat distortion temperature indicates that the present invention can maintain the crystal support capacity of the polypropylene matrix while introducing an elastic toughening structure, thereby achieving a synergistic improvement in toughness and heat resistance.

[0114] In conclusion, Figures 1 to 4 The key control factors for achieving performance balance were determined from the perspectives of formulation dosage, sodium benzoate content, branching index, and extrusion temperature. Figures 5 to 9 The effects of interfacial precomposite on the refinement of the elastic phase and the low-migration fixation of sodium benzoate were explained from the perspectives of particle size distribution, interfacial coverage, and migration rate. Figures 10 to 12 The molecular structure, degree of branching, gel fraction, and MFR relationship demonstrate that the material can maintain structural stability while avoiding deterioration in processing fluidity. Figures 13 to 15 Further evidence demonstrates that the obtained granules exhibit good storage stability, batch-to-batch consistency, and crystallization support. These results collectively indicate that the present invention effectively alleviates the challenges of simultaneously achieving elastic toughening and heat-resistant crystallization support in polypropylene, as well as the mutual constraints between processing fluidity and low-migration interface fixation. This results in highly branched polyolefin modified plastic granules possessing superior impact toughness, heat resistance, processing fluidity, interface stability, and storage reliability.

[0115] Table 1 Performance of Examples and Comparative Examples

[0116] As can be seen from the performance of the examples and comparative examples in Table 1, Examples 1-4 show a relatively balanced trend in impact strength, heat distortion temperature, sodium benzoate migration rate, and MFR change rate after storage. This indicates that the sequence of highly branched ethylene octene copolymer, sodium benzoate interfacial precomposition, and segmented melt blending helps to balance structural integrity and heat resistance. In the conventional comparative examples, when the intermediate content is too low, the branching is insufficient, or the melting temperature is too high, the impact, heat resistance, or storage stability decreases to varying degrees. In the synergistic comparative examples, the absence of sodium benzoate, the absence of the highly branched elastic phase, or the elimination of interfacial precomposition may retain individual properties, but the balance of multiple indicators decreases.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A highly branched polyolefin modified plastic granule, characterized in that, The highly branched polyolefin modified plastic granules are made from raw materials, which, based on a total mass of 100 wt% for final melt blending, consist of the following components, with polypropylene being the balance component to make up the total mass of the raw materials to 100 wt%: Polypropylene 81.00-94.70 wt%; Sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate 5.00-18.00 wt%; Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] 0.05-0.50 wt%; Tris(2,4-di-tert-butylphenyl) phosphite 0.05-0.50 wt%; The sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is obtained by melt precomposite of highly branched ethylene octene copolymer and sodium benzoate, and the highly branched ethylene octene copolymer is obtained by melt branching of ethylene octene copolymer, dicumyl peroxide and triallyl isocyanurate.

2. The highly branched polyolefin modified plastic granules according to claim 1, characterized in that, The sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate forms a dispersed elastic phase in the polypropylene continuous phase. The D50 of the dispersed elastic phase, calculated by cross-sectional scanning electron microscopy image analysis, is 0.30-1.50 μm and the D90 is 0.80-3.50 μm.

3. The highly branched polyolefin modified plastic granules according to claim 1, characterized in that, The sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is prepared by the following steps: A1. Provides highly branched ethylene octene copolymers; A2. The highly branched ethylene octene copolymer is mixed with sodium benzoate to obtain a mixture; A3. The mixture obtained in step A2 is subjected to melt precomposite to obtain melt precomposite; A4. The molten precomposite is devolatilized, cooled, and pelletized to obtain the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate.

4. The highly branched polyolefin modified plastic granules according to claim 3, characterized in that, The highly branched ethylene octene copolymer in step A1 is prepared by the following steps: B1. Mix ethylene octene copolymer, dicumyl peroxide, triallyl isocyanurate, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite to obtain a premix; B2. The premix obtained in step B1 is subjected to reactive extrusion under nitrogen protection to obtain the reactive extrusion product; B3. The reaction extrusion product is devoured, cooled, and pelletized to obtain the highly branched ethylene octene copolymer; B4. Wherein, the gel fraction of the highly branched ethylene octene copolymer is 0.05-3.00wt%, the branching index is 0.65-0.95, and the melt mass flow rate at 190℃ and 2.16kg is 0.20-8.00g / 10min.

5. The highly branched polyolefin modified plastic granules according to claim 1, characterized in that, The sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate is prepared via a dry pre-coating and short-path melting route. The dry pre-coating and short-path melting route includes: mixing the prepared highly branched ethylene octene copolymer with sodium benzoate to form a pre-coated material; subjecting the pre-coated material to short-path melting compounding, devolatilization, cooling, and pelletizing to obtain the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate. The sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate obtained contains 0.45-1.90 wt% sodium benzoate, 0.05-2.50 wt% gel fraction, and 0.01-0.15 wt% water content.

6. The highly branched polyolefin modified plastic granules according to claim 3, characterized in that, The highly branched ethylene octene copolymer provided in step A1 is prepared by continuous segmented temperature-controlled reactive extrusion. The continuous segmented temperature-controlled reactive extrusion includes: plasticizing and mixing ethylene octene copolymer, dicumyl peroxide and triallyl isocyanurate, and then performing a branching reaction; then adding pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite for mixing; and then performing devolatilization and pelletizing to obtain the highly branched ethylene octene copolymer. The obtained highly branched ethylene octene copolymer has a gel fraction of 0.05-2.50 wt% and a branching index of 0.70-0.

92.

7. The highly branched polyolefin modified plastic granules according to claim 1, characterized in that, In the highly branched ethylene octene copolymer used to prepare the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate, the content of 1-octene structural units is 15.00-45.00 wt%, and the density is 855-890 kg / m³. 3 The gel fraction is 0.05-3.00 wt%.

8. The highly branched polyolefin modified plastic granules according to claim 1, characterized in that, The melt flow rate of the highly branched polyolefin modified plastic particles at 230℃ and 2.16kg is 3.00-35.00g / 10min.

9. A method for preparing highly branched polyolefin modified plastic particles according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Provides sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate; S2. Polypropylene, the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite are premixed according to the raw material composition ratio described in claim 1 to obtain a premix; S3. The premixed material is melt-blended and extruded to obtain an extrudate; S4. The extrudate is subjected to devolatilization, cooling and pelletizing to obtain the highly branched polyolefin modified plastic pellets.

10. The preparation method according to claim 9, characterized in that, In step S2, polypropylene is first premixed with the sodium benzoate interfacial precomposite highly branched ethylene octene copolymer intermediate, and then pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite are added and mixed. The melt blending extrusion in step S3 employs segmented temperature control; In step S4, the extrudate is subjected to vacuum devolatilization and cooling.

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