A low odor high order polypropylene material, a preparation method thereof and an article thereof

Abstract

The application provides a low-odor high-order polypropylene material, a preparation method thereof and an article. The polypropylene material comprises the following raw materials in percentage by mass: polypropylene powder: 95%-99%; active tackifier: 0.8%-1.6%; stabilizer: 0.4%-0.8%; acid absorbent: 0.2%-2.0%. The polypropylene powder has a melt index of 1-50 g / 10 min, a particle size of 0.6-8 μm, and a mass percentage of powder with a particle size of less than or equal to 1.5 μm of greater than or equal to 60%. The active tackifier is an aliphatic peroxydicarbonate organic peroxide. The polypropylene material has a melt index of 4.0-6.0 g / 10 min. The obtained material has a reduced melt index and significantly improved tensile strength, bending strength and impact strength, and has a PV3900 odor grade of less than or equal to 4.5, and can be widely applied in the fields of automobiles, household appliances, packaging and gardens, and greatly improves the recycling times of polypropylene.

Description

Technical Field

[0001] This invention relates to the field of polymer modified materials technology, specifically to a low-odor high-order polypropylene material, its preparation method, and the product thereof. Background Technology

[0002] Polypropylene (PP), one of the five major general-purpose thermoplastics, is lightweight, cost-effective, and recyclable, widely used in industries such as automotive, home appliances, packaging, agriculture, forestry, and horticulture. Under the dual-carbon development model, polypropylene recycling has become the mainstream development direction in the industry. However, polypropylene molecules are rich in tertiary carbon sites, making them highly susceptible to β-chain scission under heat and shear. After multiple processing steps, the molecular weight continues to decrease, and the melt viscosity and melt strength decrease significantly. Subsequent injection molding and extrusion molding processes are prone to molding defects such as dripping, uneven wall thickness, product cracking, and shrinkage marks, severely limiting the high-value application of recycled polypropylene.

[0003] Existing recycled polypropylene modification technologies have three typical drawbacks:

[0004] Japanese patent JP7267975B2: It uses a blend of terpene resin, C5-C9 petroleum resin and stearate as a viscosity reducer. It only improves the odor and impurities of recycled materials, but has no molecular chain repair effect. It cannot improve the molecular weight and melt strength of polypropylene. It is only suitable for low-performance general-purpose products and cannot solve the core pain point of performance degradation after multiple processing.

[0005] Chinese patent CN107540935B: Modification of PP with maleic anhydride grafted with BIPB (2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane) relies on peroxide free radicals to achieve graft compatibilization. However, BIPB has small steric hindrance and a too fast decomposition rate, which can easily cause deep degradation of polypropylene and further reduce the molecular weight. It is only suitable for ultra-high flowability thin-walled small parts and cannot repair the mechanical and melt strength loss of recycled materials.

[0006] Chinese patent CN115260651A: Recycled PP crosslinked and toughened by polyethylene + waterborne polyurethane relies on flexible components to improve impact toughness, but rigidity and flexural modulus are greatly reduced, heat resistance is damaged, and the overall strength of the material is significantly lost, making it unsuitable for high-rigidity applications such as automotive structural parts and heavy-duty appliance shells.

[0007] In summary, existing modification systems have three common technical shortcomings: ① Conventional peroxides easily cause excessive degradation of PP, making it impossible to increase molecular weight; ② They only improve odor or single toughness, failing to simultaneously repair viscosity, melt strength, and tensile / flexural mechanical properties; ③ The modified odor level is too high, failing to meet the stringent low-odor standard of PV3900 for automotive interiors; ④ The reaction interface is not optimized for powdered polypropylene, resulting in insufficient contact between additives and the matrix and low modification efficiency. Summary of the Invention

[0008] To address the problems of existing technologies, this invention provides a low-odor, high-grade polypropylene material and its preparation method. The resulting material exhibits a lower melt index, significantly improved tensile / flexural / impact strength, and a PV3900 odor rating ≤ 4.5. It can be widely used in the automotive, home appliance, packaging, and landscaping industries, greatly increasing the number of polypropylene recycling cycles. This invention's polypropylene material overcomes the shortcomings of existing recycled polypropylene, such as molecular weight and melt strength degradation after multiple processing, easy excessive degradation, strong odor, and poor mechanical repair effects.

[0009] The technical solution of the present invention is as follows: This invention provides a low-odor, high-grade polypropylene material comprising the following raw materials by weight percentage: Polypropylene powder: 95%–99%; Active thickener: 0.8%–1.6%; Stabilizer: 0.4%–0.8%; Acid absorbent: 0.2%–2.0%; The polypropylene powder has a melt index of 1–50 g / 10 min, a particle size of 0.6–8 μm, and a particle size ≤1.5 μm accounts for ≥60% of the powder by mass. The active thickener is an aliphatic peroxydicarbonate organic peroxide; The melt flow index of the polypropylene material is 4.0 to 6.0 g / 10min.

[0010] Furthermore, the polypropylene material has a tensile strength ≥35 MPa, a flexural strength ≥36 MPa, a flexural modulus ≥1600 MPa, and a notched impact strength ≥5.0 kJ / m²; the PV3900 odor rating is ≤4.5.

[0011] More preferably, the polypropylene material has a melt index of 4.0–6.0 g / 10 min, a tensile strength of 35–40 MPa, a flexural strength of 36–42 MPa, a flexural modulus of 1600–1800 MPa, and a notched impact strength of 5.0–8.0 kJ / m²; and the PV3900 has an odor rating of 4.2–4.5.

[0012] Furthermore, the active thickener has a molecular weight of 500-800 Da.

[0013] Furthermore, the active thickener is di(hexadecyl)dicarbonate peroxide.

[0014] Furthermore, the stabilizer is any one of hindered phenolic antioxidants, phosphite antioxidants, and their compound systems.

[0015] Further, the stabilizer is obtained by compounding β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester (antioxidant 1076), pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010), and tris[2,4-di-tert-butylphenyl] phosphite (antioxidant 168); preferably, the mass ratio of the three is 1:1:2 to 1:1:4; Alternatively, the stabilizer may be obtained by compounding pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010) and tris[2,4-di-tert-butylphenyl] phosphite (antioxidant 168); preferably, the mass ratio of the two is 1:1 to 1:3.

[0016] Furthermore, the acid absorbent is selected from at least one of calcium stearate, zinc stearate, magnesium stearate, hydrotalcite, and zinc oxide; preferably calcium stearate.

[0017] The present invention also provides a method for preparing the aforementioned low-odor high-order polypropylene material, comprising the following steps: Step S1: Premixing Put all raw materials into a horizontal mixer and mix them evenly; Step S2: Feeding The mixture is fed into the twin-screw main feed hopper, and inert gas is introduced from the first zone of the extruder; Step S3: Extrusion Plasticization A co-rotating twin-screw extruder is used, with the main screw speed set to 300–400 r / min and the main feed rate set to 300–500 kg / h; Step S4: Cooling and pelletizing The extruded strips are cooled by water and dried by air knife, and then granulated to obtain polypropylene granules.

[0018] Furthermore, in step S1, the horizontal mixer rotates at a speed of 60–200 r / min and is stirred for 5–15 min.

[0019] Furthermore, in step S2, the inert gas is at least one of nitrogen and carbon dioxide.

[0020] Furthermore, in step S2, the flow rate of the inert gas is 25–50 L / min.

[0021] Furthermore, in step S3, the twin-screw extruder is equipped with 14 temperature zones along the hopper to the die head, plus the die head. The temperature control of each zone is as follows: Zone 1: 140-170 ℃; Zone 2: 170-190 ℃; Zones 3-11: 200-220 ℃; Zones 12-13: 200-210 ℃; Zone 14: 190-200 ℃; Die head: 190-200 ℃.

[0022] Furthermore, in step S3, the twin screws adopt a combination of high-shear front zone and low-shear rear zone conveying screws; the front zone is low-temperature enhanced to strengthen the contact reaction between powder and peroxide, while the rear zone reduces shear degradation and ensures molecular chain recombination.

[0023] Furthermore, in step S3, the twin-screw extruder is divided into three sections along the material conveying direction: zone 1 (feeding and premixing section), zone 2-3 (melting and chain extension reaction section), and zone 4-8 (devouring and conveying section).

[0024] Furthermore, in step S3, the screw in zones 1-3 includes a 56 / 56 small-lead feed thread, a 45° engagement shear block, and a 60° engagement shear block. The total length of the high-shear elements accounts for 40%-60% of the total length of the screw in zones 1-3. Zones 1-3 serve as the core reaction section, relying on moderate high shear to achieve uniform mixing of powdered PP and macromolecular peroxide, providing the free radical reaction conditions required for chain extension.

[0025] Furthermore, in step S3, the screw in zones 4 to 8 is equipped with 1 to 3 sets of 45° meshing shear blocks, and the total length of the strong shearing element accounts for 5% to 15% of the total length of the screw in zones 4 to 8; preferably, the screw in zones 4 to 8 has no 60° meshing shear blocks and no toothed disc elements.

[0026] Furthermore, in step S3, the main body of zones 4 to 8 consists of 72 / 72 and 96 / 96 large lead positive feed threads, with the feed thread length accounting for 85% to 95% of the total length of this section.

[0027] Furthermore, in step S3, a reverse flow blocking block is set at the position corresponding to the exhaust port of zone 4, and a large lead conveying thread with a length of ≥3 times the length of the flow blocking block is connected downstream of the reverse flow blocking block.

[0028] Furthermore, in step S3, the gap between the screw in zones 4 to 8 and the inner wall of the barrel is 0.25 to 0.35 mm, and the gap in zones 1 to 3 is 0.15 to 0.20 mm.

[0029] In this invention, from the exhaust port of zone 4 of the twin-screw extruder to the die head of zone 8, most of the toothed discs and 60° large shear angle meshing blocks are removed, leaving only a small number of low shear 45° meshing blocks. The long-lead forward conveying threaded element is the main component, which reduces the material shear rate and mechanical shear heat, while reserving sufficient conveying space. Inert gas is used to remove small molecule odor byproducts from the exhaust port, avoiding secondary degradation of PP caused by high-temperature shearing.

[0030] Furthermore, in step S4, the polypropylene particles have a diameter of 2-4 mm and a length of 3-5 mm.

[0031] The present invention also provides a polypropylene molded article, which is made of the aforementioned low-odor high-grade polypropylene material; the molded article includes any one of automotive interior and exterior components, household appliance housings, packaging and transportation plastic parts, or garden construction plastic parts.

[0032] Furthermore, the automotive interior and exterior trim components can be any one of the following: dashboard, door panel, bumper, or roof rack.

[0033] Furthermore, the appliance housing can be any one of a washing machine housing, an air conditioner housing, or a refrigerator plastic accessory.

[0034] Furthermore, the plastic components used in garden construction can be any one of plastic railings, garden pots, or outdoor landscape panels.

[0035] The beneficial effects of this invention are as follows: 1. This invention uses a sterically hindered aliphatic peroxydicarbonate with a molecular weight of 500-800 Da, which has a slow decomposition rate and can gently stimulate polypropylene tertiary carbon free radicals, promoting the coupling and recombination of short-chain molecules, increasing the weight-average molecular weight and narrowing the molecular weight distribution. Combined with a low-shear screw structure in zone 4 and inert nitrogen to isolate oxygen, it avoids mechanical shear degradation and thermo-oxidative degradation of long molecular chains after chain extension. Compared with a blank control without active thickener, the melt index of the product is significantly reduced, proving that the molecular chains are effectively lengthened, forming a non-crosslinked, repeatedly processable high-order polypropylene molecular structure, completely solving the inherent problem of continuous molecular weight decline in polypropylene after repeated heat processing.

[0036] 2. The screw of this invention significantly reduces strong shearing elements from the exhaust port in zone 4, eliminates all 60° meshing blocks and toothed discs, and mainly uses a large lead feed thread in the later section. The proportion of shearing elements is controlled at 5% to 15%, which effectively reduces the shear rate and frictional heat and avoids secondary molecular chain breakage. The reverse flow blocking block in zone 4 forms a thin layer of melt, which is continuously purged with 25 to 50 L / min of inert nitrogen. On the one hand, it isolates oxygen to inhibit oxidative degradation, and on the other hand, it quickly removes small molecule volatiles.

[0037] 3. The melt index of the modified product of this invention is stably controlled at 4.0–6.0 g / 10min, far lower than the 7.0 g / 10min of the unmodified blank material, and the melt viscosity and melt strength are significantly improved. After three repeated extrusion cycles, the melt index increase is ≤15%, far superior to the increase of more than 40% of ordinary recycled materials, demonstrating excellent recycling performance. The high melt strength is suitable for various molding processes such as thick-walled automotive structural parts, sheet extrusion, and large-scale plastic garden components, solving the problems of numerous molding defects and limited application scenarios of recycled polypropylene.

[0038] 4. Existing technologies rely solely on the physical masking of odors with resin, or involve extensive chain breakage during modification, generating volatile small molecules such as aldehydes, ketones, and alkanes, resulting in high odor levels that cannot meet the stringent low-odor requirements of automotive interiors. Conventional processing systems without inert gas protection can achieve an odor level of 5.0. This invention utilizes a triple odor-suppressing mechanism: ① Slow decomposition of macromolecular peroxides reduces the generation of odor-causing small molecules from drastic chain breakage; ② A combination of hindered phenol / phosphite composite antioxidants and acid absorbers inhibits thermo-oxidative oxidation and adsorbs acidic volatiles; ③ A low-shear screw in the later stage reduces mechanical chain breakage and odor generation, while inert gas continuously purges and removes volatiles. All embodiments achieve an odor level ≤ 4.5, with the optimal solution reaching as low as 4.2, meeting the PV3900 low-odor standard for automotive interiors and suitable for high-end automotive and home appliance interior materials.

[0039] 5. Compared with the blank comparative example 1, the optimal solution of the present invention increases the tensile strength from 31 MPa to 39 MPa, the flexural modulus from 1200 MPa to 1800 MPa, and the notched impact strength from 4.0 kJ / m² to 8.0 kJ / m², with a significant simultaneous improvement in tensile, flexural, and impact properties; and can be blended with a high proportion of low-temperature grinding recycled polypropylene (the blending amount can reach 40%), and the comprehensive mechanical properties after modification are better than ordinary new polypropylene, taking into account both the requirements of circular economy and the mechanical use requirements of high-end structural components. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the existing conventional screw component layout.

[0041] Figure 2 This is a schematic diagram of the optimized twin-screw component arrangement according to the present invention. Detailed Implementation

[0042] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0043] The polypropylene powder used was purchased from Sinopec Petrochemical Company.

[0044] The recycled polypropylene used was purchased from Qingdao Hailuyuan Company and ground under low temperature and inert atmosphere, with ash content ≤0.5% and mesh size controlled between 100-300 mesh.

[0045] The active thickener used was di(hexadecyl)dicarbonate peroxide, which was purchased from Noryon Chemicals Ltd.

[0046] The stabilizers used are hindered phenolic antioxidant 1010, hindered phenolic antioxidant 1076 and phosphite antioxidant 168 from Lianlong Chemical Co., Ltd., in a ratio of 1:1:2.

[0047] The acid absorbent used was purchased from Huamingtai Technology Co., Ltd.

[0048] Compressed nitrogen and carbon dioxide are commercially available.

[0049] All embodiments adopt Figure 2 The arrangement of twin-screw components is shown.

[0050] In the diagram, sections 1 to 8 represent the eight barrel sections of the extruder, with the exhaust port located above section 5. Figure 1 (Existing screw): 60° meshing blocks and toothed disc strong shearing elements are densely arranged in sections 4 to 8; Figure 2 (Screw of the present invention): The 60° engagement block and toothed disc are removed in sections 4 to 8, with only a small number of 45° engagement blocks. The main body is a long-distance, large-lead conveying thread. A reverse flow blocking element is added at the exhaust port of section 4.

[0051] Example 1 A low-odor, high-grade polypropylene material is provided, composed of the following raw materials by weight percentage: Polypropylene powder 98.6%; Active thickener 0.8%; Stabilizer 0.4%; Calcium stearate 0.2%; The polypropylene powder has a melt index of 1–50 g / 10 min, a particle size of 0.6–8 μm, and a particle size ≤1.5 μm accounts for ≥60% of the powder by mass. The polypropylene material has a melt index of 5.8 g / 10min, a tensile strength of 35 MPa, a flexural strength of 36 MPa, a flexural modulus of 1600 MPa, a notched impact strength of 5.5 kJ / m², and an odor grade of 4.5.

[0052] The preparation method is as follows: Step S1: Premixing After weighing the materials, put them into a horizontal mixer and stir continuously for 10 minutes at a speed of 80 r / min. Step S2: Feeding The well-mixed material is fed into the twin-screw main feed hopper, and nitrogen gas is introduced from the first zone of the extruder at a flow rate of 30 L / min. Step S3: Extrusion Plasticization A co-rotating twin-screw extruder is used, with the main screw speed set at 350 r / min and the main feed rate set at 300 kg / h. The twin-screw extruder has 14 temperature zones along the hopper to the die head, and the temperature control of each zone is as follows: 160℃, 200℃, 210℃, 210℃, 210℃, 220℃, 220℃, 220℃, 220℃, 210℃, 210℃, 200℃, 200℃. Step S4: Cooling and pelletizing The extruded strip from the twin-screw extruder die is pulled, then cooled and dried in a cooling water tank and by an air knife before being conveyed to a pelletizer for pelletizing, resulting in cylindrical modified polypropylene granules with a length of 3-5 mm and a diameter of 2.5-4 mm.

[0053] Example 2 A low-odor, high-grade polypropylene material is provided, composed of the following raw materials by weight percentage: 58% polypropylene powder, 40.6% recycled polypropylene; Active thickener 0.8%; Stabilizer 0.4%; Calcium stearate 0.2%; The melt index of polypropylene powder and recycled polypropylene powder is 1-50 g / 10min, the particle size is 0.6-8μm, and the mass percentage of powder with a particle size ≤1.5μm is ≥60%; The polypropylene material has a melt index of 5.0 g / 10min, a tensile strength of 36 MPa, a flexural strength of 37 MPa, a flexural modulus of 1650 MPa, a notched impact strength of 5.3 kJ / m², and an odor grade of 4.5.

[0054] The preparation method is as follows: Step S1: Premixing After weighing the materials, put them into a horizontal mixer and stir continuously for 10 minutes at a speed of 80 r / min. Step S2: Feeding The well-mixed material is fed into the twin-screw main feed hopper, and nitrogen gas is introduced from the first zone of the extruder at a flow rate of 30 L / min. Step S3: Extrusion Plasticization A co-rotating twin-screw extruder is used, with the main screw speed set at 350 r / min and the main feed rate set at 300 kg / h. The twin-screw extruder has 14 temperature zones along the hopper to the die head, and the temperature control of each zone is as follows: 160℃, 200℃, 210℃, 210℃, 210℃, 220℃, 220℃, 220℃, 220℃, 210℃, 210℃, 200℃, 200℃. Step S4: Cooling and pelletizing The extruded strip from the twin-screw extruder die is pulled, then cooled and dried in a cooling water tank and by an air knife before being conveyed to a pelletizer for pelletizing, resulting in cylindrical modified polypropylene granules with a length of 3-5 mm and a diameter of 2.5-4 mm.

[0055] Example 3 A low-odor, high-grade polypropylene material is provided, composed of the following raw materials by weight percentage: 58% polypropylene powder, 40.4% recycled polypropylene powder; Active thickener 1.0%; Stabilizer 0.4%; Calcium stearate 0.2%; The melt index of polypropylene powder and recycled polypropylene powder is 1-50 g / 10min, the particle size is 0.6-8μm, and the mass percentage of powder with a particle size ≤1.5μm is ≥60%; The polypropylene material has a melt index of 4.8 g / 10min, a tensile strength of 37 MPa, a flexural strength of 40 MPa, a flexural modulus of 1700 MPa, a notched impact strength of 6.0 kJ / m², and an odor grade of 4.5.

[0056] The preparation method is as follows: Step S1: Premixing After weighing the materials, put them into a horizontal mixer and stir continuously for 10 minutes at a speed of 80 r / min. Step S2: Feeding The well-mixed material is fed into the twin-screw main feed hopper, and nitrogen gas is introduced from the first zone of the extruder at a flow rate of 30 L / min. Step S3: Extrusion Plasticization A co-rotating twin-screw extruder is used, with the main screw speed set at 350 r / min and the main feed rate set at 300 kg / h. The twin-screw extruder has 14 temperature zones along the hopper to the die head, and the temperature control of each zone is as follows: 160℃, 200℃, 210℃, 210℃, 210℃, 220℃, 220℃, 220℃, 220℃, 210℃, 210℃, 200℃, 200℃. Step S4: Cooling and pelletizing The extruded strip from the twin-screw extruder die is pulled, then cooled and dried in a cooling water tank and by an air knife before being conveyed to a pelletizer for pelletizing, resulting in cylindrical modified polypropylene granules with a length of 3-5 mm and a diameter of 2.5-4 mm.

[0057] Example 4 A low-odor, high-grade polypropylene material is provided, composed of the following raw materials by weight percentage: 58% polypropylene powder, 40.1% recycled polypropylene powder; Active thickener 1.3%; Stabilizer 0.4%; Calcium stearate 0.2%; The melt index of polypropylene powder and recycled polypropylene powder is 1-50 g / 10min, the particle size is 0.6-8μm, and the mass percentage of powder with a particle size ≤1.5μm is ≥60%; The polypropylene material has a melt index of 4.0 g / 10min, a tensile strength of 39 MPa, a flexural strength of 42 MPa, a flexural modulus of 1800 MPa, a notched impact strength of 8.0 kJ / m², and an odor grade of 4.2.

[0058] The preparation method is as follows: Step S1: Premixing After weighing the materials, put them into a horizontal mixer and stir continuously for 10 minutes at a speed of 80 r / min. Step S2: Feeding The well-mixed material is fed into the twin-screw main feed hopper, and nitrogen gas is introduced from the first zone of the extruder at a flow rate of 30 L / min. Step S3: Extrusion Plasticization A co-rotating twin-screw extruder is used, with the main screw speed set at 350 r / min and the main feed rate set at 300 kg / h. The twin-screw extruder has 14 temperature zones along the hopper to the die head, and the temperature control of each zone is as follows: 160℃, 200℃, 210℃, 210℃, 210℃, 220℃, 220℃, 220℃, 220℃, 210℃, 210℃, 200℃, 200℃. Step S4: Cooling and pelletizing The extruded strip from the twin-screw extruder die is pulled, then cooled and dried in a cooling water tank and by an air knife before being conveyed to a pelletizer for pelletizing, resulting in cylindrical modified polypropylene granules with a length of 3-5 mm and a diameter of 2.5-4 mm.

[0059] Example 5 A low-odor, high-grade polypropylene material is provided, composed of the following raw materials by weight percentage: 58% polypropylene powder, 39.8% recycled polypropylene powder; Active thickener 1.6%; Stabilizer 0.4%; Calcium stearate 0.2%; The melt index of polypropylene powder and recycled polypropylene powder is 1-50 g / 10min, the particle size is 0.6-8μm, and the mass percentage of powder with a particle size ≤1.5μm is ≥60%; The polypropylene material has a melt index of 6.0 g / 10min, a tensile strength of 36 MPa, a flexural strength of 39 MPa, a flexural modulus of 1700 MPa, a notched impact strength of 5.0 kJ / m², and an odor rating of 4.3.

[0060] The preparation method is as follows: Step S1: Premixing After weighing the materials, put them into a horizontal mixer and stir continuously for 10 minutes at a speed of 80 r / min. Step S2: Feeding The well-mixed material is fed into the twin-screw main feed hopper, and nitrogen gas is introduced from the first zone of the extruder at a flow rate of 30 L / min. Step S3: Extrusion Plasticization A co-rotating twin-screw extruder is used, with the main screw speed set at 350 r / min and the main feed rate set at 300 kg / h. The twin-screw extruder has 14 temperature zones along the hopper to the die head, and the temperature control of each zone is as follows: 160℃, 200℃, 210℃, 210℃, 210℃, 220℃, 220℃, 220℃, 220℃, 210℃, 210℃, 200℃, 200℃. Step S4: Cooling and pelletizing The extruded strip from the twin-screw extruder die is pulled, then cooled and dried in a cooling water tank and by an air knife before being conveyed to a pelletizer for pelletizing, resulting in cylindrical modified polypropylene granules with a length of 3-5 mm and a diameter of 2.5-4 mm.

[0061] Example 6 A low-odor, high-grade polypropylene material is provided, composed of the following raw materials by weight percentage: 58% polypropylene powder, 40.1% recycled polypropylene powder; Active thickener 1.3%; Stabilizer 0.4%; Calcium stearate 0.2%; The melt index of polypropylene powder and recycled polypropylene powder is 1-50 g / 10min, the particle size is 0.6-8μm, and the mass percentage of powder with a particle size ≤1.5μm is ≥60%; The polypropylene material has a melt index of 6.0 g / 10min, a tensile strength of 36 MPa, a flexural strength of 41 MPa, a flexural modulus of 1800 MPa, a notched impact strength of 8.0 kJ / m², and an odor grade of 4.5.

[0062] The preparation method is as follows: Step S1: Premixing After weighing the materials, put them into a horizontal mixer and stir continuously for 10 minutes at a speed of 80 r / min. Step S2: Feeding The well-mixed material is fed into the twin-screw main feed hopper, and nitrogen gas is introduced from the first zone of the extruder at a flow rate of 50 L / min. Step S3: Extrusion Plasticization A co-rotating twin-screw extruder is used, with the main screw speed set at 350 r / min and the main feed rate set at 300 kg / h. The twin-screw extruder has 14 temperature zones along the hopper to the die head, and the temperature control of each zone is as follows: 160℃, 200℃, 210℃, 210℃, 210℃, 220℃, 220℃, 220℃, 220℃, 210℃, 210℃, 200℃, 200℃. Step S4: Cooling and pelletizing The extruded strip from the twin-screw extruder die is pulled, then cooled and dried in a cooling water tank and by an air knife before being conveyed to a pelletizer for pelletizing, resulting in cylindrical modified polypropylene granules with a length of 3-5 mm and a diameter of 2.5-4 mm.

[0063] Example 7 A low-odor, high-grade polypropylene material is provided, composed of the following raw materials by weight percentage: 58% polypropylene powder, 40.1% recycled polypropylene powder; Active thickener 1.3%; Stabilizer 0.4%; Calcium stearate 0.2%; The melt index of polypropylene powder and recycled polypropylene powder is 1-50 g / 10min, the particle size is 0.6-8μm, and the mass percentage of powder with a particle size ≤1.5μm is ≥60%; The polypropylene material has a melt index of 5.5 g / 10min, a tensile strength of 36 MPa, a flexural strength of 39 MPa, a flexural modulus of 1700 MPa, a notched impact strength of 5.0 kJ / m², and an odor grade of 4.2.

[0064] The preparation method is as follows: Step S1: Premixing After weighing the materials, put them into a horizontal mixer and stir continuously for 10 minutes at a speed of 80 r / min. Step S2: Feeding The well-mixed material is fed into the twin-screw main feed hopper, and nitrogen gas is introduced from the first zone of the extruder at a flow rate of 30 L / min. Step S3: Extrusion Plasticization A co-rotating twin-screw extruder is used, with the main screw speed set at 350 r / min and the main feed rate set at 300 kg / h. The twin-screw extruder has 14 temperature zones along the hopper to the die head, and the temperature control of each zone is as follows: 180℃, 200℃, 210℃, 210℃, 210℃, 220℃, 220℃, 220℃, 220℃, 210℃, 210℃, 200℃, 200℃. Step S4: Cooling and pelletizing The extruded strip from the twin-screw extruder die is pulled, then cooled and dried in a cooling water tank and by an air knife before being conveyed to a pelletizer for pelletizing, resulting in cylindrical modified polypropylene granules with a length of 3-5 mm and a diameter of 2.5-4 mm.

[0065] Example 8 A low-odor, high-grade polypropylene material is provided, composed of the following raw materials by weight percentage: 58% polypropylene powder, 40.1% recycled polypropylene powder; Active thickener 1.3%; Stabilizer 0.4%; Calcium stearate 0.2%; The melt index of polypropylene powder and recycled polypropylene powder is 1-50 g / 10min, the particle size is 0.6-8μm, and the mass percentage of powder with a particle size ≤1.5μm is ≥60%; The polypropylene material has a melt index of 5.6 g / 10min, a tensile strength of 37 MPa, a flexural strength of 41 MPa, a flexural modulus of 1750 MPa, a notched impact strength of 6.5 kJ / m², and an odor rating of 4.3.

[0066] The preparation method is as follows: Step S1: Premixing After weighing the materials, put them into a horizontal mixer and stir continuously for 10 minutes at a speed of 80 r / min. Step S2: Feeding The well-mixed material is fed into the twin-screw main feed hopper, and nitrogen gas is introduced from the first zone of the extruder at a flow rate of 30 L / min. Step S3: Extrusion Plasticization A co-rotating twin-screw extruder is used, with the main screw speed set at 350 r / min and the main feed rate set at 300 kg / h. The twin-screw extruder has 14 temperature zones along the hopper to the die head, and the temperature control of each zone is as follows: 130℃, 200℃, 210℃, 210℃, 210℃, 220℃, 220℃, 220℃, 220℃, 210℃, 210℃, 200℃, 200℃. Step S4: Cooling and pelletizing The extruded strip from the twin-screw extruder die is pulled, then cooled and dried in a cooling water tank and by an air knife before being conveyed to a pelletizer for pelletizing, resulting in cylindrical modified polypropylene granules with a length of 3-5 mm and a diameter of 2.5-4 mm.

[0067] Comparative Example 1 A polypropylene material is provided, comprising the following raw materials in weight percentages: 58% polypropylene powder, 41.4% recycled polypropylene powder; Stabilizer 0.4%; Calcium stearate 0.2%; The melt index of polypropylene powder and recycled polypropylene powder is 1-50 g / 10min, the particle size is 0.6-8μm, and the mass percentage of powder with a particle size ≤1.5μm is ≥60%.

[0068] The preparation method is as follows: Step S1: Premixing After weighing the materials, put them into a horizontal mixer and stir continuously for 10 minutes at a speed of 80 r / min. Step S2: Feeding The well-mixed material is fed into the twin-screw main feed hopper, and nitrogen gas is introduced from the first zone of the extruder at a flow rate of 30 L / min. Step S3: Extrusion Plasticization A co-rotating twin-screw extruder is used, with the main screw speed set at 350 r / min and the main feed rate set at 300 kg / h. The twin-screw extruder has 14 temperature zones along the hopper to the die head, and the temperature control of each zone is as follows: 160℃, 200℃, 210℃, 210℃, 210℃, 220℃, 220℃, 220℃, 220℃, 210℃, 210℃, 200℃, 200℃. Step S4: Cooling and pelletizing The extruded strip from the twin-screw extruder die is pulled, then cooled and dried in a cooling water tank and by an air knife before being conveyed to a pelletizer for pelletizing, resulting in cylindrical modified polypropylene granules with a length of 3-5 mm and a diameter of 2.5-4 mm.

[0069] Comparative Example 2 A polypropylene material is provided, comprising the following raw materials in weight percentages: 98% polypropylene powder; Stabilizer 0.4%; Calcium stearate 0.2%; The polypropylene powder has a melt index of 1–50 g / 10 min, a particle size of 0.6–8 μm, and a particle size ≤1.5 μm accounts for ≥60% of the powder by mass.

[0070] The preparation method is as follows: Step S1: Premixing After weighing the materials, put them into a horizontal mixer and stir continuously for 10 minutes at a speed of 80 r / min. Step S2: Feeding The well-mixed material is fed into the twin-screw main feed hopper, and nitrogen gas is introduced from the first zone of the extruder at a flow rate of 30 L / min. Step S3: Extrusion Plasticization A co-rotating twin-screw extruder is used, with the main screw speed set at 350 r / min and the main feed rate set at 300 kg / h. The twin-screw extruder has 14 temperature zones along the hopper to the die head, and the temperature control of each zone is as follows: 160℃, 200℃, 210℃, 210℃, 210℃, 220℃, 220℃, 220℃, 220℃, 210℃, 210℃, 200℃, 200℃. Step S4: Cooling and pelletizing The extruded strip from the twin-screw extruder die is pulled, then cooled and dried in a cooling water tank and by an air knife before being conveyed to a pelletizer for pelletizing, resulting in cylindrical modified polypropylene granules with a length of 3-5 mm and a diameter of 2.5-4 mm.

[0071] Comparative Example 3 A polypropylene material is provided, comprising the following raw materials in weight percentages: Polypropylene powder 56.2%, recycled polypropylene powder 41.4%; Active thickener 1.8%; Stabilizer 0.4%; Calcium stearate 0.2%; The melt index of polypropylene powder and recycled polypropylene powder is 1-50 g / 10min, the particle size is 0.6-8μm, and the mass percentage of powder with a particle size ≤1.5μm is ≥60%.

[0072] The preparation method is as follows: Step S1: Premixing After weighing the materials, put them into a horizontal mixer and stir continuously for 10 minutes at a speed of 80 r / min. Step S2: Feeding The well-mixed material is fed into the twin-screw main feed hopper, and nitrogen gas is introduced from the first zone of the extruder at a flow rate of 30 L / min. Step S3: Extrusion Plasticization A co-rotating twin-screw extruder is used, with the main screw speed set at 350 r / min and the main feed rate set at 300 kg / h. The twin-screw extruder has 14 temperature zones along the hopper to the die head, and the temperature control of each zone is as follows: 130℃, 200℃, 210℃, 210℃, 210℃, 220℃, 220℃, 220℃, 220℃, 210℃, 210℃, 200℃, 200℃. Step S4: Cooling and pelletizing The extruded strip from the twin-screw extruder die is pulled, then cooled and dried in a cooling water tank and by an air knife before being conveyed to a pelletizer for pelletizing, resulting in cylindrical modified polypropylene granules with a length of 3-5 mm and a diameter of 2.5-4 mm.

[0073] Table 1 Material Test Results

[0074] As can be seen from Table 1, in Examples 1, 2, 3, 4, and 5, the viscosity of the material first increases and then decreases as the amount of active thickener increases. Among them, Example 4 has the best overall performance and the most significant decrease in melt index when the amount of active thickener added is 1.3%.

[0075] As can be seen from Examples 4, 7, and 8, the processing temperature in Zone 1 has a significant impact on material properties, with the most significant increase in material viscosity occurring at 160°C.

[0076] Comparing Example 4 with Comparative Examples 1, 2, and 3, adding an appropriate amount of active tackifier can significantly reduce the melt index of the material, improve its viscosity and mechanical properties, and even surpass the mechanical properties of the original resin. However, adding too much active tackifier can actually increase the melt index and reduce the impact resistance of the material. Nitrogen gas has a significant protective effect on the reaction system and reduces odor.

[0077] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A low-odor, high-grade polypropylene material, characterized in that, It contains the following percentages by weight of raw materials: Polypropylene powder: 95%–99%; Active thickener: 0.8%–1.6%; Stabilizer: 0.4%–0.8%; Acid absorbent: 0.2%–2.0%; The polypropylene powder has a melt index of 1–50 g / 10 min, a particle size of 0.6–8 μm, and a particle size ≤1.5 μm accounts for ≥60% of the powder by mass. The active thickener is an aliphatic peroxydicarbonate organic peroxide; The melt flow index of the polypropylene material is 4.0 to 6.0 g / 10min.

2. The low-odor high-grade polypropylene material according to claim 1, characterized in that, The polypropylene material has a tensile strength ≥35 MPa, a flexural strength ≥36 MPa, a flexural modulus ≥1600 MPa, and a notched impact strength ≥5.0 kJ / m²; the PV3900 odor rating is ≤4.

5. Preferably, the polypropylene material has a melt index of 4.0–6.0 g / 10 min, a tensile strength of 35–40 MPa, a flexural strength of 36–42 MPa, a flexural modulus of 1600–1800 MPa, and a notched impact strength of 5.0–8.0 kJ / m²; and the PV3900 has an odor rating of 4.2–4.

5.

3. The low-odor high-grade polypropylene material according to claim 1 or 2, characterized in that, The active tackifier has a molecular weight of 500-800 Da; preferably, the active tackifier is di(hexadecyl)dicarbonate peroxide.

4. The low-odor high-grade polypropylene material according to claim 1 or 2, characterized in that, The stabilizer is any one of hindered phenolic antioxidants, phosphite antioxidants, and their compound systems; And / or, the stabilizer is obtained by compounding β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester (antioxidant 1076), pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010), and tris[2,4-di-tert-butylphenyl] phosphite (antioxidant 168); preferably, the mass ratio of the three is 1:1:2 to 1:1:4; Alternatively, the stabilizer may be a compound of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010) and tris[2,4-di-tert-butylphenyl] phosphite (antioxidant 168); preferably, the mass ratio of the two is (1:1 to 1:3). And / or, the acid absorber is selected from at least one of calcium stearate, zinc stearate, magnesium stearate, hydrotalcite, and zinc oxide; preferably calcium stearate.

5. A method for preparing a low-odor high-order polypropylene material according to any one of claims 1 to 3, characterized in that, Includes the following steps: Step S1: Premixing Put all raw materials into a horizontal mixer and mix them evenly; Step S2: Feeding The mixture is fed into the twin-screw main feed hopper, and inert gas is introduced from the first zone of the extruder; Step S3: Extrusion Plasticization A co-rotating twin-screw extruder is used, with the main screw speed set to 300–400 r / min and the main feed rate set to 300–500 kg / h; Step S4: Cooling and pelletizing The extruded strips are cooled by water and dried by air knife, and then granulated to obtain polypropylene granules.

6. The preparation method according to claim 4, characterized in that, In step S1, the horizontal mixer rotates at a speed of 60–200 r / min and is stirred for 5–15 min.

7. The preparation method according to claim 5, characterized in that, In step S2, the inert gas is at least one of nitrogen and carbon dioxide; And / or, in step S2, the flow rate of the inert gas is 25-50 L / min; And / or, in step S3, the twin-screw extruder is equipped with 14 temperature zones + die head along the hopper to the die head, and the temperature control of each zone is as follows: Zone 1: 140~170 ℃; Zone 2: 170–190 ℃; Zones 3–11: 200–220 ℃; Zones 12–13: 200–210 ℃; Zone 14: 190–200 ℃; Machine head: 190~200 ℃.

8. The preparation method according to claim 5, characterized in that, In step S3, the twin-screw extruder is divided into three sections along the material conveying direction: zone 1 (feeding and premixing section), zone 2-3 (melting and chain extension reaction section), and zone 4-8 (devouring and conveying section). Preferably, in step S3, the screw in zones 1 to 3 includes a 56 / 56 small lead feed thread, a 45° engagement shear block, and a 60° engagement shear block, with the total length of the strong shearing element accounting for 40% to 60% of the total length of the screw in zones 1 to 3; Preferably, in step S3, the screw in zones 4 to 8 is provided with 1 to 3 sets of 45° meshing shear blocks, and the total length of the strong shearing element accounts for 5% to 15% of the total length of the screw in zones 4 to 8; more preferably, the screw in zones 4 to 8 has no 60° meshing shear blocks and no toothed disc elements. More preferably, in step S3, the main body of zones 4 to 8 consists of 72 / 72 and 96 / 96 large lead positive feed threads, and the length of the feed thread accounts for 85% to 95% of the total length of this section; More preferably, in step S3, a reverse flow blocking block is set at the position corresponding to the exhaust port of zone 4, and a large lead conveying thread with a length of ≥3 times the length of the flow blocking block is connected downstream of the reverse flow blocking block. More preferably, in step S3, the gap between the screw in zones 4 to 8 and the inner wall of the barrel is 0.25 to 0.35 mm, and the gap between zones 1 to 3 is 0.15 to 0.20 mm.

9. The preparation method according to claim 8, characterized in that, In step S4, the polypropylene particles have a diameter of 2-4 mm and a length of 3-5 mm.

10. A polypropylene molded article, characterized in that, The molded article is made from any of the low-odor high-grade polypropylene materials described in claims 1 to 4; the molded article includes any one of automotive interior and exterior trim components, household appliance housings, packaging and transportation plastic parts, or garden construction plastic parts.

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