Polypropylene material for packing belt and preparation method thereof

Abstract

The invention discloses a polypropylene material for a packing belt and a preparation method of the polypropylene material, and belongs to the technical field of compositions of high-molecular compounds. The polypropylene material comprises polypropylene, an ethylene-acetic acid copolymer, polyethylene wax, an antioxidant, a filler and a silicon-containing slipping agent. Compared with the prior art, the material disclosed by the invention shows excellent brittleness resistance and lubricating property in a low-temperature environment, effectively avoids the fracture risk of the cold-chain food packing belt under a low-temperature condition, and remarkably reduces the friction coefficient, so that the cold-chain food packing belt is suitable for a high-speed automatic packing machine, the durability and reliability of the cold-chain food packing belt are improved, and the service life of the cold-chain food packing belt is prolonged. The method has wide application prospects and remarkable economic benefits, and is particularly suitable for packaging requirements of cold-chain food.

Description

Technical Field

[0001] This invention relates to the field of polymer composition technology, and more particularly to a polypropylene material for packing tape and its preparation method. Background Technology

[0002] With the rapid development of the cold chain logistics industry, higher requirements have been placed on the low-temperature toughness and abrasion resistance of packaging materials for temperature-sensitive products such as food and pharmaceuticals. As a key packaging consumable, strapping needs to maintain its resistance to brittleness in environments below -30°C and withstand the mechanical friction of high-speed automatic strapping machines. However, traditional polypropylene (PP) strapping is prone to brittle fracture at low temperatures and has a high dynamic friction coefficient, leading to low strapping efficiency, increased strapping breakage rate, and difficulty in meeting the reliability requirements of cold chain scenarios.

[0003] Currently, mainstream technologies primarily improve PP performance by adding toughening agents (such as POE and EPDM) or lubricants (stearates and amide-based slip agents). However, significant drawbacks remain. While adding elastomers like POE and EPDM can enhance low-temperature toughness, it significantly sacrifices the material's tensile strength. Traditional polypropylene strapping tends to become brittle at low temperatures, leading to breakage during use and impacting packaging reliability. This is particularly true in cold chain food packaging, where low temperatures place higher demands on the strapping's toughness and resistance to brittleness. Furthermore, existing polypropylene strapping, due to its high coefficient of friction, is prone to slippage or jamming in high-speed automatic strapping machines, affecting packaging efficiency. Additionally, the high coefficient of friction increases strapping wear, reducing its lifespan. While some composite materials improve material performance to some extent, their complex manufacturing processes and high costs limit their large-scale application.

[0004] For example, Chinese patent application CN119241948A discloses an antistatic packing strap and its preparation method, focusing on antistatic function but failing to address low-temperature brittleness; another Chinese patent application CN112143096A discloses a lightweight PP packing strap and its molding and processing method, reducing weight through process optimization, but not overcoming the bottleneck of the material's intrinsic properties. Existing technologies struggle to simultaneously balance key properties such as low-temperature toughness, tensile strength, lubrication stability, and transparency. There is an urgent need for a packing strap material that combines high toughness at low temperatures, stable low friction, and long-term anti-migration properties. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a polypropylene material for packing straps and a method for preparing the same. By optimizing the preparation process of the silicone-containing lubricant, a uniform and stable lubricating layer is formed on the surface of the polypropylene material, significantly reducing the coefficient of friction and enhancing the material's toughness under low-temperature conditions, effectively suppressing brittle fracture.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A polypropylene material for packing straps comprises the following components in parts by weight: 70-85 parts polypropylene, 8-15 parts ethylene-acetic acid copolymer, 1-2 parts polyethylene wax, 1-2 parts antioxidant, 3-8 parts filler, and 1-3 parts silicone-containing slip agent.

[0007] The preparation method of the silicone-containing slip agent is as follows: S1. The acid ester compound is reacted with urea in methanol at low temperature, followed by crystallization, filtration, extraction, washing and vacuum distillation to obtain the pretreated product; S2. The pretreated material and silane compound are refluxed in the presence of a platinum-carbon catalyst, followed by centrifugation to remove the catalyst and vacuum distillation to remove excess silane compound, thereby obtaining the silicon-containing slip agent.

[0008] The preparation method of the polypropylene material used for packing straps is as follows: Polypropylene, ethylene-acetic acid copolymer, polyethylene wax, antioxidant, filler, and silicone-containing slip agent are added to a high-speed mixer and stirred at room temperature to form a dry mixture. The mixture is then added to a single-screw extruder and kneaded and plasticized in a molten state. The mixture is then extruded through a die into a strip preform and introduced into a water cooling tank to obtain polypropylene material.

[0009] The filler is at least one of nano-calcium carbonate, talc powder, mica powder, kaolin, montmorillonite, and silica.

[0010] The antioxidant is at least one of antioxidant 1076, antioxidant 168, and antioxidant 264.

[0011] The stirring speed is 400-800 rpm at room temperature for 5-10 minutes.

[0012] The temperature gradient of the single-screw extruder is 180-190℃ in the feeding section, 200-210℃ in the plasticizing section, and 210-230℃ in the die section. The screw speed is controlled at 40-80 rpm. The extruder is mixed and plasticized in a molten state for 4-8 minutes and then extruded through the die.

[0013] The cooling water temperature in the water cooling tank is controlled at 30-50℃, and the cooling time is about 30-60 seconds.

[0014] The preparation method of the silicone-containing slip agent is as follows, in parts by weight: S1. Mix 80-110 parts of the ester compound with 270-300 parts of urea, add 400-600 parts of methanol, stir in a water bath for 1-5 hours, refrigerate to crystallize, filter under vacuum, extract the filtrate with petroleum ether, separate the organic phase, wash with water 1-3 times, remove the solvent by vacuum distillation, and obtain the pretreated product. S2. Mix 80-90 parts of the pretreated material prepared in step S1 with 30-50 parts of silane compound, add 1-2 parts of platinum activated carbon catalyst, reflux and stir at 100-120℃ for 5-10 hours, centrifuge at 4000-6000rpm for 5-15min to remove the catalyst, and remove excess silane compound by vacuum distillation to obtain the product, a silicon-containing slip agent.

[0015] The ester compound is at least one of methyl erucic acid and methyl ricinoleate.

[0016] The silane compound is at least one of triethoxysilane, dimethylethylsilane, and triisopropylsilane.

[0017] The functions of each substance in the preparation method of the silicone-containing slip agent are as follows: Ester compounds serve as core reactants, providing unsaturated fatty acid methyl ester groups for inclusion in urea to enrich unsaturation.

[0018] Urea reacts with acid ester compounds at low temperatures, selectively encapsulating and separating saturated components.

[0019] Methanol, as a solvent, promotes the mixing of urea and ester compounds, ensuring that the inclusion process is carried out efficiently at low temperatures.

[0020] Petroleum ether separates the organic phase during the extraction step, effectively removing urea inclusion complexes and extracting the target unsaturated components.

[0021] Water is used to wash the extracted organic phase, remove water-soluble impurities and residual solvents, and ensure the purity of the pretreated product.

[0022] The pretreated material serves as a reaction matrix, providing unsaturated bonds to react with silane compounds, introducing silicon groups to impart lubricating properties.

[0023] Silane compounds undergo catalytic addition reactions with the unsaturated bonds of the pretreated material to form Si-C or Si-OC bonds, which reduces surface friction and enhances slip properties.

[0024] Platinum-carbon catalysts catalyze the reaction of silanes with unsaturated bonds, accelerating the reaction rate and increasing product conversion.

[0025] This method purifies unsaturated esters through urea encapsulation in step S1, followed by catalytic introduction of silicon groups in step S2. The resulting silicon-containing slip agent significantly improves the lubrication properties and low-temperature toughness of polypropylene materials. The synergistic effect of the various substances ensures the high efficiency of the reaction and the stability of the product properties.

[0026] Compared with existing technologies, it has the following advantages: 1) This invention optimizes the preparation process of silicone-containing slip agents, enabling them to form a uniform and stable lubricating layer on the surface of polypropylene materials, which significantly reduces the dynamic friction coefficient of the materials. It is particularly suitable for high-speed automatic packaging machines, improving packaging efficiency and reliability.

[0027] 2) The specific components in the silicone slip agent of this invention interact with the polypropylene matrix, enhancing the toughness of the material under low-temperature conditions and effectively inhibiting brittle fracture. It is particularly suitable for the packaging needs of cold chain food, ensuring the durability and reliability of the packing straps in low-temperature environments.

[0028] 3) The preparation method of the silicone-containing slip agent of the present invention is simple and efficient. The synergistic effect of each component ensures the high efficiency of the reaction and the stability of the product performance. At the same time, it improves the processing stability and production efficiency of polypropylene materials, and has significant economic benefits and broad application prospects. Detailed Implementation

[0029] Main source of materials: Polypropylene, item number: B4902, brand: Sinopec Yanshan.

[0030] Ethylene-acetic acid copolymer, grade: 1316, brand: Hanwha, South Korea.

[0031] Antioxidant 168, product model: RIANOX® 168, brand: Rianlon.

[0032] Polyethylene wax, item number: AC-6A, brand: Honeywell (USA).

[0033] Nano calcium carbonate, product specifications: 1200 mesh, item number: 01, Lingshou County Marble Mineral Products Processing Plant.

[0034] Platinum activated carbon catalyst, model: HS-100, brand: Heraeus Precious Metals.

[0035] All other raw materials used in the embodiments and comparative examples of this invention are commercially available products.

[0036] Example 1

[0037] A method for preparing a polypropylene material for packing straps is as follows, in parts by weight: 78 parts of polypropylene, 12 parts of ethylene-acetic acid copolymer, 1.8 parts of polyethylene wax, 1.2 parts of antioxidant 168, 5 parts of nano-calcium carbonate, and 2 parts of silicone-containing slip agent were added to a high-speed mixer and stirred at 600 rpm for 8 minutes at room temperature to form a dry mixture. The mixture was then added to a single-screw extruder, with the extruder temperature gradient set as follows: feed section 185℃, plasticizing section 205℃, and die section 220℃. The screw speed was controlled at 60 rpm. The mixture was kneaded and plasticized in a molten state for 6 minutes and then extruded through the die into a strip preform. The extruded strip preform was then introduced into a water cooling tank, with the cooling water temperature controlled at 40℃ and the cooling time approximately 50 seconds, to obtain the polypropylene material.

[0038] The preparation method of the silicone-containing slip agent is as follows, in parts by weight: S1. Mix 95 parts of methyl ricinoleate with 285 parts of urea, add 500 parts of methanol, stir in a water bath at 0°C for 3 hours, refrigerate to crystallize, filter under vacuum, extract the filtrate with petroleum ether, separate the organic phase, wash with water 3 times, remove the solvent by vacuum distillation, and obtain the pretreated product. S2. Mix 83 parts of the pretreated material prepared in step S1 with 40 parts of dimethyl ethyl silane, add 1.7 parts of platinum activated carbon catalyst, reflux and stir at 110°C for 8 hours, centrifuge at 5000 rpm for 10 min to remove the catalyst, and remove excess silane compounds by vacuum distillation to obtain the product, a silicon-containing slip agent.

[0039] Example 2

[0040] The preparation method of a polypropylene material for packing straps is basically the same as that in Example 1, except that the preparation method of the silicone-containing slip agent is different.

[0041] The preparation method of the silicone-containing slip agent is as follows, in parts by weight: S1. Mix 95 parts of methyl erucic acid with 285 parts of urea, add 500 parts of methanol, stir in a water bath at 0°C for 3 hours, refrigerate to crystallize, filter under vacuum, extract the filtrate with petroleum ether, separate the organic phase, wash with water 3 times, remove the solvent by vacuum distillation, and obtain the pretreated product. S2. Mix 83 parts of the pretreated material prepared in step S1 with 40 parts of dimethyl ethyl silane, add 1.7 parts of platinum activated carbon catalyst, reflux in an oil bath at 110°C for 8 hours, centrifuge at 5000 rpm for 10 minutes to remove the catalyst, and remove excess silane compounds by vacuum distillation to obtain the product, a silicon-containing slip agent.

[0042] Example 3

[0043] The preparation method of a polypropylene material for packing straps is basically the same as that in Example 1, except that the preparation method of the silicone-containing slip agent is different.

[0044] The preparation method of the silicone-containing slip agent is as follows, in parts by weight: S1. Mix 95 parts of methyl ricinoleate with 285 parts of urea, add 500 parts of methanol, stir in a water bath at 0°C for 3 hours, refrigerate to crystallize, filter under vacuum, extract the filtrate with petroleum ether, separate the organic phase, wash with water 3 times, remove the solvent by vacuum distillation, and obtain the pretreated product. S2. Mix 83 parts of the pretreated material prepared in step S1 with 40 parts of triisopropylsilane, add 1.7 parts of platinum activated carbon catalyst, reflux in an oil bath at 110°C for 8 hours, centrifuge at 5000 rpm for 10 minutes to remove the catalyst, and remove excess silane compounds by vacuum distillation to obtain the product, a silicon-containing slip agent.

[0045] Example 4

[0046] The preparation method of a polypropylene material for packing straps is basically the same as that in Example 1, except that the preparation method of the silicone-containing slip agent is different.

[0047] The preparation method of the silicone-containing slip agent is as follows, in parts by weight: S1. Mix 95 parts of methyl ricinoleate with 285 parts of urea, add 500 parts of methanol, stir in a water bath at 0°C for 3 hours, refrigerate to crystallize, filter under vacuum, extract the filtrate with petroleum ether, separate the organic phase, wash with water 3 times, remove the solvent by vacuum distillation, and obtain the pretreated product. S2. Mix 83 parts of the pretreated material prepared in step S1 with 40 parts of triethoxysilane, add 1.7 parts of platinum activated carbon catalyst, reflux in an oil bath at 110°C for 8 hours, centrifuge at 5000 rpm for 10 minutes to remove the catalyst, and remove excess silane compounds by vacuum distillation to obtain the product, a silicon-containing slip agent.

[0048] Comparative Example 1 The preparation method of a polypropylene material for packing straps is basically the same as that in Example 1, except that the preparation method of the silicone-containing slip agent is different.

[0049] The preparation method of the silicone-containing slip agent is as follows, in parts by weight: S1. Mix 95 parts of methyl linoleate with 285 parts of urea, add 500 parts of methanol, stir in a water bath at 0°C for 3 hours, refrigerate to crystallize, filter under vacuum, extract the filtrate with petroleum ether, separate the organic phase, wash with water 3 times, remove the solvent by vacuum distillation, and obtain the pretreated product. S2. Mix 83 parts of the pretreated material prepared in step S1 with 40 parts of dimethyl ethyl silane, add 1.7 parts of platinum activated carbon catalyst, reflux in an oil bath at 110°C for 8 hours, centrifuge at 5000 rpm for 10 minutes to remove the catalyst, and remove excess silane compounds by vacuum distillation to obtain the product, a silicon-containing slip agent.

[0050] Comparative Example 2 The preparation method of a polypropylene material for packing straps is basically the same as that in Example 1, except that the preparation method of the silicone-containing slip agent is different.

[0051] The preparation method of the silicone-containing slip agent is as follows, in parts by weight: S1. Mix 95 parts of methyl ricinoleate with 285 parts of urea, add 500 parts of methanol, stir in a water bath at 0°C for 3 hours, refrigerate to crystallize, filter under vacuum, extract the filtrate with petroleum ether, separate the organic phase, wash with water 3 times, remove the solvent by vacuum distillation, and obtain the pretreated product. S2. Mix 83 parts of the pretreated material prepared in step S1 with 40 parts of triethylsilane, add 1.7 parts of platinum activated carbon catalyst, reflux in an oil bath at 110°C for 8 hours, centrifuge at 5000 rpm for 10 minutes to remove the catalyst, and remove excess silane compounds by vacuum distillation to obtain the product, a silicon-containing slip agent.

[0052] Comparative Example 3 The preparation method of a polypropylene material for packing straps is basically the same as that in Example 1, except that the silicone-containing slip agent is not added.

[0053] Test Example 1 Static friction coefficient test: The static friction coefficients of the polypropylene materials for packing straps prepared in Examples 1-4 and Comparative Examples 1-3 of this invention were tested using a friction coefficient tester; the test results are shown in Table 1.

[0054] Experimental protocol static friction coefficient Example 1 0.07 Example 2 0.09 Example 3 0.12 Example 4 0.08 Comparative Example 1 0.15 Comparative Example 2 0.11 Comparative Example 3 0.23 Test Example 2 Low-temperature toughness test: The polypropylene materials for packing straps prepared in Examples 1-4 and Comparative Examples 1-3 of this invention were tested according to the test method of ISO 180-2019 "Plastics - Determination of Izod impact strength". The test temperature was -30℃ and the test was performed with an A-notch. The test results are shown in Table 2.

[0055] Experimental protocol Low-temperature toughness (KJ / m²) Example 1 5.9 Example 2 5.7 Example 3 4.8 Example 4 5.3 Comparative Example 1 4.5 Comparative Example 2 4.1 Comparative Example 3 3.2 In Example 1, the silicone-containing slip agent prepared using methyl ricinoleate exhibited superior static friction coefficient and low-temperature toughness in polypropylene materials. This is likely due to the interaction between the polar hydroxyl groups of methyl ricinoleate and dimethyl ethyl silane, which significantly enhances the anchoring effect of the slip agent in the polypropylene matrix, preventing migration and precipitation. This results in a uniform and dense lubricating layer on the material surface, greatly reducing frictional resistance. Simultaneously, the plasticizing effect of the hydroxyl groups weakens the intermolecular forces of polypropylene, improving chain segment mobility at low temperatures and inhibiting brittle fracture. In contrast, methyl erucic acid in Example 2, although containing long carbon chains, lacks polar anchoring groups, making it prone to separation from the matrix at low temperatures, resulting in a slightly higher friction coefficient and slightly weaker toughness. Furthermore, methyl linoleate in Comparative Example 1 contains multiple double bonds, which are easily oxidized during processing to generate polar groups, disrupting the uniformity of the lubricating layer, significantly increasing the friction coefficient. The oxidation products also become stress concentration points, exacerbating low-temperature crack propagation and resulting in the lowest impact strength.

[0056] Dimethyl ethyl silane contains two low-surface-energy methyl groups, which can oriented to form a uniform lubricating layer on the polypropylene surface, significantly reducing frictional resistance. Simultaneously, the ethyl groups provide moderate steric hindrance, preventing migration and precipitation, and ensuring the stability of the lubricating layer. In contrast, triisopropyl silane suffers from uneven dispersion and hindered chain segment movement due to excessive steric hindrance from its large isopropyl groups; while triethoxy silane's polar ethoxy groups enhance hydrogen bonding with nano-calcium carbonate, its high polarity weakens surface lubrication efficiency and increases chain segment rigidity; and triethyl silane's long-chain migration and precipitation create weak areas that induce stress concentration. None of these three methods match the balanced advantage of dimethyl ethyl silane in lubrication and low-temperature toughness.

Claims

1. A polypropylene material for packing straps, characterized in that, It includes the following components by weight: 70-85 parts polypropylene, 8-15 parts ethylene-acetic acid copolymer, 1-2 parts polyethylene wax, 1-2 parts antioxidant, 3-8 parts filler, and 1-3 parts silicone-containing slip agent; The preparation method of the silicone-containing slip agent is as follows: S1. The acid ester compound is reacted with urea in methanol at low temperature, followed by crystallization, filtration, extraction, washing and vacuum distillation to obtain the pretreated product; S2. The pretreated material and silane compound are refluxed in the presence of a platinum-carbon catalyst, followed by centrifugation to remove the catalyst and vacuum distillation to remove excess silane compound, thereby obtaining the silicon-containing slip agent.

2. A method for preparing the polypropylene material for packing straps as described in claim 1, characterized in that, The method is as follows: Polypropylene, ethylene-acetic acid copolymer, polyethylene wax, antioxidant, filler, and silicone-containing slip agent are added to a high-speed mixer and stirred at room temperature to form a dry mixture. The mixture is then added to a single-screw extruder and kneaded and plasticized in a molten state. The mixture is then extruded through a die into a strip preform and introduced into a water cooling tank to obtain polypropylene material.

3. The method for preparing the polypropylene material for packing straps as described in claim 2, characterized in that, The filler is at least one of nano-calcium carbonate, talc powder, mica powder, kaolin, montmorillonite, and silica.

4. The method for preparing the polypropylene material for packing straps as described in claim 2, characterized in that, The antioxidant is at least one of antioxidant 1076, antioxidant 168, and antioxidant 264.

5. The method for preparing the polypropylene material for packing straps as described in claim 2, characterized in that, The stirring speed is 400-800 rpm at room temperature for 5-10 minutes.

6. The method for preparing the polypropylene material for packing straps as described in claim 2, characterized in that, The temperature gradient of the single-screw extruder is 180-190℃ in the feeding section, 200-210℃ in the plasticizing section, and 210-230℃ in the die section. The screw speed is controlled at 40-80 rpm. The extruder is mixed and plasticized in a molten state for 4-8 minutes and then extruded through the die.

7. The method for preparing the polypropylene material for packing straps as described in claim 2, characterized in that, The cooling water temperature in the water cooling tank is controlled at 30-50℃, and the cooling time is about 30-60 seconds.

8. The method for preparing the polypropylene material for packing straps as described in claim 2, characterized in that, The preparation method of the silicone-containing slip agent is as follows, in parts by weight: S1. Mix 80-110 parts of the ester compound with 270-300 parts of urea, add 400-600 parts of methanol, stir in a water bath for 1-5 hours, refrigerate to crystallize, filter under vacuum, extract the filtrate with petroleum ether, separate the organic phase, wash with water 1-3 times, remove the solvent by vacuum distillation, and obtain the pretreated product. S2. Mix 80-90 parts of the pretreated material prepared in step S1 with 30-50 parts of silane compound, add 1-2 parts of platinum activated carbon catalyst, reflux and stir at 100-120℃ for 5-10 hours, centrifuge at 4000-6000rpm for 5-15min to remove the catalyst, and remove excess silane compound by vacuum distillation to obtain the product, a silicon-containing slip agent.

9. The method for preparing the polypropylene material for packing straps as described in claim 8, characterized in that, The ester compound is at least one of methyl erucic acid and methyl ricinoleate.

10. The method for preparing the polypropylene material for packing straps as described in claim 8, characterized in that, The silane compound is at least one of triethoxysilane, dimethylethylsilane, and triisopropylsilane.