Polypropylene sling for flexible freight bag and preparation process of polypropylene sling

Abstract

The invention relates to the technical field of polypropylene straps, in particular to a polypropylene strap for a container bag and a preparation process of the polypropylene strap. Modified polypropylene and modified nano titanium dioxide are blended for 10-20 min at the blending temperature of 130-140 DEG C, then polypropylene, high-density polyethylene, talcum powder, a compatilizer, a lubricant and an antioxidant are added and mixed evenly, and a mixture is obtained; and pouring the mixture into an extruder, carrying out melt extrusion to form a film, cutting the film into filaments, carrying out stretching and heat setting to prepare protofilaments, and weaving the protofilaments into a sling through a sling machine to obtain the polypropylene sling for the flexible freight bag. The polypropylene sling for the container bag prepared by the invention not only has excellent mechanical properties, but also has excellent aging resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of polypropylene slings, and particularly to a polypropylene sling for flexible intermediate bulk containers (FIBC) and its preparation process. Background Art

[0002] With the rapid development of the global logistics industry, flexible intermediate bulk containers (FIBC) have become the core packaging tools for transporting large quantities of bulk materials, and their demand has been continuously increasing. Polypropylene (PP) slings have become key components of the load-bearing structure of FIBCs due to their advantages such as light weight, corrosion resistance, and low cost.

[0003] Polypropylene (PP) has become one of the most widely used general plastics due to its low price and good performance. However, due to the tertiary carbon atoms contained in its molecular chain structure being extremely prone to thermal-oxidative degradation and photo-oxidative degradation under the conditions of oxygen, heat, and ultraviolet light, polypropylene exhibits poor anti-aging performance. When used outdoors, its service life is severely shortened, restricting its application range. Although traditional organic anti-aging agents have excellent effects, most of them are small molecules with poor thermal stability, are not resistant to high temperatures, and are prone to denaturation and migration during processing and use, which is not conducive to their application in polymer materials such as PP.

[0004] Therefore, we propose a polypropylene sling for flexible intermediate bulk containers (FIBC) and its preparation process. Summary of the Invention

[0005] The purpose of the present invention is to provide a polypropylene sling for flexible intermediate bulk containers (FIBC) and its preparation process to solve the problems raised in the prior art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A polypropylene sling for flexible intermediate bulk containers (FIBC) comprises the following weight components: 90 - 100 parts of polypropylene, 20 - 30 parts of high-density polyethylene, 5 - 10 parts of modified polypropylene, 10 - 20 parts of modified nano-titanium dioxide, 5 - 15 parts of talcum powder, 3 - 5 parts of compatibilizer, 3 - 8 parts of lubricant, and 0.1 - 1.0 part of antioxidant.

[0008] Further, the preparation method of the modified polypropylene is as follows:

[0009] Mix polypropylene grafted with glycidyl methacrylate, N-(4-aminophenyl) maleimide, and toluene evenly, stir at room temperature for 22 - 24 h, filter, wash, and dry to obtain modified polypropylene.

[0010] Further, the mass ratio of polypropylene grafted with glycidyl methacrylate, N-(4-aminophenyl) maleimide, and toluene is 1:(0.2 - 0.5):(5 - 10).

[0011] Further, the preparation method of the modified nano-titanium dioxide is as follows:

[0012] Step 1: Mix maleic anhydride-modified tea polyphenols and ethanol evenly, add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide, react for 1 - 2 h, then add furfurylamine, and reflux at 80 - 85 °C for 5 - 7 h. After cooling to room temperature, filter, wash, and dry to obtain a furan-based compound;

[0013] Step 2: Ultrasonically disperse nano-titanium dioxide in a mixed solution of absolute ethanol and deionized water, add 3-(methacryloyloxy)propyltrimethoxysilane and mix evenly. Adjust the pH of the system to 4 - 5, and react at 60 - 70 °C for 4 - 6 h. After centrifugation, washing, and drying, obtain double-bonded titanium dioxide;

[0014] Step 3: Mix double-bonded titanium dioxide, sodium dodecyl sulfate, emulsifier OP-10, and deionized water, ultrasonically disperse for 0.5 - 1.0 h, introduce nitrogen, add methyl methacrylate, acrylonitrile, 4-acryloxy-2-hydroxybenzophenone, and the furan-based compound, heat to 65 - 75 °C, add potassium persulfate, and react for 4 - 6 h. After filtration, washing, and drying, obtain the modified nano-titanium dioxide.

[0015] Further, in Step 1, the mass ratio of maleic anhydride-modified tea polyphenols, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and N-hydroxysuccinimide is 1:(0.1 - 0.2):(0.08 - 0.10).

[0016] Further, the mass ratio of maleic anhydride-modified tea polyphenols, furfurylamine, and ethanol is 1:(2 - 4):(10 - 12).

[0017] Further, the preparation steps of the maleic anhydride-modified tea polyphenols are as follows: Mix tea polyphenols and ethyl acetate evenly, add maleic anhydride and pyridine, and react at 45 - 55 °C for 5 - 7 h. After rotary evaporation under reduced pressure, recrystallization, and freeze-drying, obtain maleic anhydride-modified tea polyphenols.

[0018] In the above technical solution, as a natural antioxidant and antibacterial agent, tea polyphenols are graft-modified with maleic anhydride to introduce active double bonds into the tea polyphenol molecules, improve their stability, and can significantly enhance the antioxidant performance of plastics, thereby extending the service life of plastic products. At the same time, the antibacterial properties of tea polyphenols can endow the polypropylene material with antibacterial functions.

[0019] Further, the mass ratio of tea polyphenols, ethyl acetate, maleic anhydride, and pyridine is 1:(40 - 50):(0.5 - 1.0):(0.3 - 0.5).

[0020] Further, in the second step, the mass ratio of nano-titanium dioxide, absolute ethanol, deionized water and 3-(methacryloyloxy)propyltrimethoxysilane is 1:(15 - 20):(3 - 5):(1 - 3).

[0021] Further, in the third step, the modified nano-titanium dioxide is composed of the following components in parts by weight: 10 - 20 parts of double-bonded titanium dioxide, 1 - 2 parts of sodium dodecyl sulfate, 0.1 - 0.5 part of emulsifier OP-10, 200 - 500 parts of deionized water, 10 - 15 parts of methyl methacrylate, 15 - 20 parts of acrylonitrile, 1 - 5 parts of 4-acryloxy-2-hydroxybenzophenone, 5 - 10 parts of furan-based compound, and 1 - 5 parts of potassium persulfate.

[0022] Further, the compatibilizer is one or a mixture of more than one of polypropylene grafted maleic anhydride and polyethylene grafted maleic anhydride.

[0023] Further, the lubricant is one or a mixture of more than one of polypropylene wax, polyethylene wax, silicone masterbatch, polytetrafluoroethylene, and paraffin powder.

[0024] Further, the antioxidant is one or a mixture of more than one of antioxidant 1010, antioxidant 1076, and antioxidant BHT246.

[0025] A preparation process of a polypropylene sling for a flexible intermediate bulk container (FIBC) includes the following steps:

[0026] Blend the modified polypropylene and the modified nano-titanium dioxide for 10 - 20 min at a blending temperature of 130 - 140 °C, then add polypropylene, high-density polyethylene, talcum powder, compatibilizer, lubricant, and antioxidant and mix evenly to obtain a blended material; pour the blended material into an extruder, melt and extrude it into a film, cut the film into filaments, perform stretching and heat setting to make raw filaments, and weave the raw filaments into a sling by a sling machine to obtain the polypropylene sling for a FIBC.

[0027] Further, the temperatures of the first, second, third, and fourth temperature control zones of the extruder are 180 ± 20 °C, 200 ± 20 °C, 220 ± 20 °C, and 240 ± 20 °C respectively, the die head temperature is 220 ± 20 °C, and the screw speed is 20 - 60 r / min.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] For the polypropylene sling for a FIBC and its preparation process of the present invention, through the reaction of the epoxy group in polypropylene grafted glycidyl methacrylate with the amino group in N-(4-aminophenyl)maleimide, the modified polypropylene containing maleimide groups is successfully obtained, providing dynamic crosslinking sites for the subsequent Diels - Alder reaction;

[0030] In the solution, through the EDC / NHS coupling system, the carboxyl group in maleic anhydride modified tea polyphenols reacts with furfurylamine to introduce a furan group, obtaining a furyl compound; meanwhile, 3-(methacryloyloxy)propyltrimethoxysilane is used to modify the surface of nano-titanium dioxide to introduce a double bond; finally, by means of free radical copolymerization, methyl methacrylate (MMA), acrylonitrile (AN), 4-acryloxy-2-hydroxybenzophenone (AHB) and the furyl compound are copolymerized and coated on the surface of nano-titanium dioxide to form an organic layer, which is beneficial to improving its compatibility and dispersibility in the polypropylene matrix (PP), reducing agglomeration, and further improving the mechanical properties, anti-ultraviolet aging property and antioxidant property of the material; among them, the ultraviolet absorption characteristics of acrylonitrile itself and the ultraviolet absorber 4-acryloxy-2-hydroxybenzophenone and the furyl compound act synergistically to jointly improve the anti-ultraviolet performance and antioxidant performance of the material; introducing the furyl compound can undergo a Diels-Alder reaction with maleimide in the modified polypropylene, significantly improving the heat resistance and thermal stability of the material. Specific embodiments

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0032] In this embodiment, polypropylene grafted glycidyl methacrylate: grade D502, sourced from Dongguan Kadar Plastic Raw Materials Co., Ltd.; polypropylene: model is South Korea Hyosung R701; nano-titanium dioxide: rutile type, particle size is 20-50nm, sourced from Bohuasi Nano Technology; talcum powder: particle size is 5000 mesh, sourced from Jiangyin Guangyuan Superfine Powder Co., Ltd.; compatibilizer: polypropylene grafted maleic anhydride, grade is Exxelor PO 1020 Exxon; lubricant: polyethylene wax, model is Honeywell AC-6A; antioxidant: model is antioxidant 1010.

[0033] Unless otherwise specified, the following parts are by mass.

[0034] Example 1: A preparation process for a polypropylene sling for a flexible intermediate bulk container, including the following processes:

[0035] Mix 5 parts of modified polypropylene and 10 parts of modified nano-titanium dioxide for 10 min at a blending temperature of 130°C. Then add 90 parts of polypropylene, 20 parts of high-density polyethylene, 5 parts of talcum powder, 3 parts of compatibilizer, 3 parts of lubricant, and 0.1 part of antioxidant and mix evenly to obtain a blended material. Pour the blended material into an extruder, melt-extrude it into a film, cut it into filaments, and after stretching and heat setting, make the original filaments, and then weave them into slings through a sling machine to obtain polypropylene slings for flexible intermediate bulk containers (FIBCs). The temperatures of the first, second, third, and fourth temperature control zones of the extruder are 180°C, 200°C, 220°C, and 240°C respectively, the die head temperature is 220°C, and the screw speed is 50 r / min.

[0036] The preparation method of the modified polypropylene is as follows:

[0037] Mix 5 parts of polypropylene grafted with glycidyl methacrylate, 1 part of N-(4-aminophenyl) maleimide, and 25 parts of toluene evenly, stir at room temperature for 22 h, filter, wash, and dry to obtain the modified polypropylene.

[0038] The preparation method of the modified nano-titanium dioxide is as follows:

[0039] Step 1: Mix 5 parts of tea polyphenols and 200 parts of ethyl acetate evenly, add 2.5 parts of maleic anhydride and 1.5 parts of pyridine, react at 45°C for 5 h, and after rotary evaporation under reduced pressure, recrystallization, and freeze-drying, obtain maleic anhydride-modified tea polyphenols.

[0040] Mix 5 parts of maleic anhydride-modified tea polyphenols and 50 parts of ethanol evenly, add 0.5 part of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 0.4 part of N-hydroxysuccinimide, react for 1 h, then add 10 parts of furfurylamine, reflux at 80°C for 5 h, cool to room temperature, filter, wash, and dry to obtain a furan-based compound.

[0041] Step 2: Ultrasonically disperse 10 parts of nano-titanium dioxide in a mixed solution of 150 parts of absolute ethanol and 30 parts of deionized water, add 10 parts of 3-(methacryloyloxy)propyltrimethoxysilane and mix evenly, adjust the pH of the system to 4, react at 60°C for 4 h, and after centrifugation, washing, and drying, obtain double-bonded titanium dioxide.

[0042] Step 3: Mix 10 parts of double-bonded titanium dioxide, 1 part of sodium dodecyl sulfate, 0.1 part of emulsifier OP-10, and 200 parts of deionized water, ultrasonically disperse for 0.5 h, introduce nitrogen, add 10 parts of methyl methacrylate, 15 parts of acrylonitrile, 1 part of 4-acryloxy-2-hydroxybenzophenone, and 5 parts of the furan-based compound, raise the temperature to 65°C, add 1 part of potassium persulfate, react for 4 h, filter, wash, and dry to obtain the modified nano-titanium dioxide.

[0043] Example 2: A preparation process of polypropylene sling for flexible intermediate bulk container, including the following processes:

[0044] Blend 8 parts of modified polypropylene and 15 parts of modified nano-titanium dioxide for 15 min at a blending temperature of 135 °C. Then add 95 parts of polypropylene, 25 parts of high-density polyethylene, 10 parts of talcum powder, 4 parts of compatibilizer, 6 parts of lubricant and 0.5 part of antioxidant and mix evenly to obtain a mixture. Pour the mixture into an extruder, melt and extrude it into a film, cut it into filaments, and through stretching and heat setting, make the original filaments, and then weave them into slings by a sling machine to obtain polypropylene slings for flexible intermediate bulk container. The temperatures of the first, second, third, and fourth temperature control zones of the extruder are 180 °C, 200 °C, 220 °C, and 240 °C respectively, the die head temperature is 220 °C, and the screw speed is 50 r / min.

[0045] The preparation method of the modified polypropylene is as follows:

[0046] Mix 8 parts of polypropylene grafted glycidyl methacrylate, 2.4 parts of N-(4-aminophenyl) maleimide and toluene evenly, stir at room temperature for 23 h, filter, wash and dry to obtain modified polypropylene.

[0047] The preparation method of the modified nano-titanium dioxide is as follows:

[0048] Step 1: Mix 3 parts of tea polyphenols and 135 parts of ethyl acetate evenly, add 2.4 parts of maleic anhydride and 1.2 parts of pyridine, react at 50 °C for 6 h, and after reduced pressure rotary evaporation, recrystallization and freeze drying, obtain maleic anhydride modified tea polyphenols.

[0049] Mix 3 parts of maleic anhydride modified tea polyphenols and 33 parts of ethanol evenly, add 0.45 part of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 0.27 part of N-hydroxysuccinimide, react for 1.5 h, then add 9 parts of furfurylamine, reflux and react at 82 °C for 6 h, cool to room temperature, filter, wash and dry to obtain a furanyl compound.

[0050] Step 2: Ultrasonically disperse 15 parts of nano-titanium dioxide in a mixed solution of 270 parts of absolute ethanol and 60 parts of deionized water, add 30 parts of 3-(methacryloyloxy)propyltrimethoxysilane and mix evenly, adjust the pH of the system to 4.5, react at 65 °C for 5 h, and after centrifugation, washing and drying, obtain double-bonded titanium dioxide.

[0051] Step 3: Mix 15 parts of double-bonded titanium dioxide, 1.5 parts of sodium dodecyl sulfate, 0.3 part of emulsifier OP-10 and 400 parts of deionized water, ultrasonically disperse for 0.8 h, introduce nitrogen, add 12 parts of methyl methacrylate, 18 parts of acrylonitrile, 3 parts of 4-acryloxy-2-hydroxybenzophenone and 8 parts of furyl compound, heat up to 70 °C, add 3 parts of potassium persulfate, react for 5 h, filter, wash and dry to obtain modified nano-titanium dioxide.

[0052] Example 3: A preparation process of polypropylene sling for flexible intermediate bulk container, including the following processes:

[0053] Blend 10 parts of modified polypropylene and 20 parts of modified nano-titanium dioxide for 20 min at a blending temperature of 140 °C, then add 100 parts of polypropylene, 30 parts of high-density polyethylene, 15 parts of talc powder, 5 parts of compatibilizer, 8 parts of lubricant and 1.0 part of antioxidant and mix evenly to obtain a mixture; Pour the mixture into an extruder, melt and extrude it into a film, cut it into filaments, and after stretching and heat setting, make the original filaments, and weave them into slings through a sling machine to obtain polypropylene slings for flexible intermediate bulk containers; The temperatures of the first, second, third and fourth temperature control zones of the extruder are 180 °C, 200 °C, 220 °C and 240 °C respectively, the die head temperature is 220 °C, and the screw speed is 50 r / min;

[0054] The preparation method of the modified polypropylene is as follows:

[0055] Mix 10 parts of polypropylene grafted with glycidyl methacrylate, 5 parts of N-(4-aminophenyl) maleimide and 100 parts of toluene evenly, stir at room temperature for 24 h, filter, wash and dry to obtain modified polypropylene;

[0056] The preparation method of the modified nano-titanium dioxide is as follows:

[0057] Step 1: Mix 3 parts of tea polyphenols and 150 parts of ethyl acetate evenly, add 3 parts of maleic anhydride and 1.5 parts of pyridine, react at 55 °C for 7 h, carry out rotary evaporation under reduced pressure, recrystallize and freeze-dry to obtain maleic anhydride-modified tea polyphenols;

[0058] Mix 3 parts of maleic anhydride-modified tea polyphenols and 36 parts of ethanol evenly, add 0.6 part of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 0.3 part of N-hydroxysuccinimide, react for 2 h, then add 12 parts of furfurylamine, reflux and react at 85 °C for 7 h, cool to room temperature, filter, wash and dry to obtain furyl compound;

[0059] Step 2: Ultrasonically disperse 20 parts of nano-titanium dioxide in a mixed solution of 400 parts of absolute ethanol and 100 parts of deionized water. Add 60 parts of 3-(methacryloyloxy)propyltrimethoxysilane and mix evenly. Adjust the pH of the system to 5 and react at 70 °C for 6 h. After centrifugation, washing, and drying, double-bonded titanium dioxide is obtained.

[0060] Step 3: Mix 20 parts of double-bonded titanium dioxide, 2 parts of sodium dodecyl sulfate, 0.5 part of emulsifier OP-10, and 500 parts of deionized water, and ultrasonically disperse for 1.0 h. Introduce nitrogen, add 15 parts of methyl methacrylate, 20 parts of acrylonitrile, 5 parts of 4-acryloxy-2-hydroxybenzophenone, and 10 parts of furanyl compound. Heat up to 75 °C, add 5 parts of potassium persulfate, and react for 6 h. After filtration, washing, and drying, modified nano-titanium dioxide is obtained.

[0061] Comparative Example 1: A preparation process for polypropylene slings for flexible intermediate bulk containers includes the following process:

[0062] Taking Example 2 as the control group, Comparative Example 1 does not add modified polypropylene, and other steps are the same as those in Example 2.

[0063] Comparative Example 2: A preparation process for polypropylene slings for flexible intermediate bulk containers includes the following process:

[0064] Taking Example 2 as the control group, Comparative Example 2 replaces the modified nano-titanium dioxide with nano-titanium dioxide of the same mass, and other steps are the same as those in Example 2.

[0065] Comparative Example 3: A preparation process for polypropylene slings for flexible intermediate bulk containers includes the following process:

[0066] The preparation method of the modified nano-titanium dioxide is as follows:

[0067] Step 1: Mix 3 parts of tea polyphenols and 135 parts of ethyl acetate evenly, add 2.4 parts of maleic anhydride and 1.2 parts of pyridine, and react at 50 °C for 6 h. After rotary evaporation under reduced pressure, recrystallization, and freeze-drying, maleic anhydride-modified tea polyphenols are obtained.

[0068] Mix 3 parts of maleic anhydride-modified tea polyphenols and 33 parts of ethanol evenly, add 0.45 part of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 0.27 part of N-hydroxysuccinimide, and react for 1.5 h. Then add 9 parts of furfurylamine and reflux at 82 °C for 6 h. Cool to room temperature, filter, wash, and dry to obtain a furanyl compound.

[0069] Step 2: Ultrasonically disperse 15 parts of nano-titanium dioxide in a mixed solution of 270 parts of absolute ethanol and 60 parts of deionized water. Add 30 parts of 3-(methacryloyloxy)propyltrimethoxysilane and mix evenly. Adjust the pH of the system to 4.5 and react at 65 °C for 5 h. After centrifugation, washing, and drying, double-bonded titanium dioxide is obtained.

[0070] Step 3: Mix 15 parts of double-bonded titanium dioxide, 1.5 parts of sodium dodecyl sulfate, 0.3 part of emulsifier OP-10, and 400 parts of deionized water, and ultrasonically disperse for 0.8 h. Pass in nitrogen, add 12 parts of methyl methacrylate, 18 parts of acrylonitrile, and 3 parts of 4-acryloxy-2-hydroxybenzophenone. Heat up to 70 °C, add 3 parts of potassium persulfate, and react for 5 h. After filtration, washing, and drying, modified nano-titanium dioxide is obtained.

[0071] Taking Example 2 as the control group, in Comparative Example 3, no furanyl compound will be added, and other steps are the same as those in Example 2.

[0072] Comparative Example 4: A preparation process of polypropylene sling for flexible intermediate bulk container, including the following processes:

[0073] The preparation method of the modified nano-titanium dioxide is as follows:

[0074] Step 1: Mix 3 parts of tea polyphenols and 135 parts of ethyl acetate evenly, add 2.4 parts of maleic anhydride and 1.2 parts of pyridine, and react at 50 °C for 6 h. After rotary evaporation under reduced pressure, recrystallization, and freeze-drying, maleic anhydride-modified tea polyphenols are obtained.

[0075] Mix 3 parts of maleic anhydride-modified tea polyphenols and 33 parts of ethanol evenly, add 0.45 part of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 0.27 part of N-hydroxysuccinimide, and react for 1.5 h. Then add 9 parts of furfurylamine and reflux at 82 °C for 6 h. Cool to room temperature, filter, wash, and dry to obtain the furanyl compound.

[0076] Step 2: Ultrasonically disperse 15 parts of nano-titanium dioxide in a mixed solution of 270 parts of absolute ethanol and 60 parts of deionized water. Add 30 parts of 3-(methacryloyloxy)propyltrimethoxysilane and mix evenly. Adjust the pH of the system to 4.5 and react at 65 °C for 5 h. After centrifugation, washing, and drying, double-bonded titanium dioxide is obtained.

[0077] Step 3: Mix 15 parts of double-bonded titanium dioxide, 1.5 parts of sodium dodecyl sulfate, 0.3 part of emulsifier OP-10, and 400 parts of deionized water, and ultrasonically disperse for 0.8 h. Pass in nitrogen, add 12 parts of methyl methacrylate, 18 parts of acrylonitrile, and 8 parts of the furanyl compound. Heat up to 70 °C, add 3 parts of potassium persulfate, and react for 5 h. After filtration, washing, and drying, modified nano-titanium dioxide is obtained.

[0078] Compared with Example 2, in Comparative Example 4, 4 - allyloxy - 2 - hydroxybenzophenone is not added, and other steps are the same as those in Example 2.

[0079] Detection experiment:

[0080] 1. Tensile property test: Take the films obtained in Examples 1 - 3 and Comparative Examples 1 - 4, and conduct tests according to the standard of GB / T 1040.3 - 2006 "Plastics - Determination of tensile properties - Part 3: Test conditions for films and sheets", with a tensile rate of 10 mm / min.

[0081] 2. Xenon lamp aging test: Refer to the standard of GB / T 16422.2 - 2014, use a xenon lamp as the light source, with an irradiation intensity of 0.51 W / m 2 , the black - standard temperature cycles between 65 °C and 100 °C, the exposure period is 102 min of drying and 18 min of spraying, the test time is 120 h, measure the tensile strength before and after aging, and calculate the change rate of tensile strength.

[0082] The test results are as follows:

[0083] Tensile strength / MPa Tensile strength retention rate / % Example 1 43.4 77.9 Example 2 45.5 80.4 Example 3 44.8 78.5 Comparative Example 1 38.7 70.2 Comparative Example 2 36.0 58.7 Comparative Example 3 40.6 62.8 Comparative Example 4 42.3 64.5

[0084] According to the data in the above table, the following conclusions can be clearly obtained:

[0085] The data of Examples 1 - 3 show that the present invention improves the tensile strength and aging resistance of the material by introducing modified polypropylene and modified nano - titanium dioxide. The data of Example 2 and Comparative Example 1 show that in Comparative Example 1, modified polypropylene is not introduced, and the tensile strength and tensile retention rate of the material decrease significantly; the data of Example 2 and Comparative Example 1 show that compared with nano - titanium dioxide, the modified nano - titanium dioxide prepared by the present invention has better compatibility and aging resistance; the data of Example 2 and Comparative Examples 3 - 4 show that in Comparative Example 3, furyl compounds are not introduced, lacking dynamic cross - linking sites, resulting in a significant decrease in aging resistance and thermal stability, and in Comparative Example 4, 4 - allyloxy - 2 - hydroxybenzophenone is not introduced, resulting in a decrease in ultraviolet resistance, thus leading to a decrease in the aging resistance of the material.

[0086] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above - mentioned exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non - restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes within the meaning and scope of the equivalent elements of the claims in the present invention.

Claims

1. A polypropylene sling for flexible intermediate bulk containers, characterized in that: It includes the following weight components: 90 - 100 parts of polypropylene, 20 - 30 parts of high-density polyethylene, 5 - 10 parts of modified polypropylene, 10 - 20 parts of modified nano-titanium dioxide, 5 - 15 parts of talcum powder, 3 - 5 parts of compatibilizer, 3 - 8 parts of lubricant, and 0.1 - 1.0 part of antioxidant.

2. The polypropylene sling for a flexible intermediate bulk container according to claim 1, wherein: The preparation method of the modified polypropylene is as follows: Mix polypropylene grafted with glycidyl methacrylate, N-(4-aminophenyl) maleimide and toluene evenly, stir at room temperature for 22 - 24 h, filter, wash and dry to obtain modified polypropylene.

3. The polypropylene sling for a flexible intermediate bulk container according to claim 1, wherein: The preparation method of the modified nano-titanium dioxide is as follows: Step 1: Mix maleic anhydride-modified tea polyphenols and ethanol evenly, add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide, react for 1 - 2 h, then add furfurylamine, and reflux at 80 - 85 °C for 5 - 7 h. After cooling to room temperature, filter, wash and dry to obtain a furan-based compound; Step 2: Ultrasonically disperse nano-titanium dioxide in a mixed solution of anhydrous ethanol and deionized water, add 3-(methacryloyloxy)propyltrimethoxysilane and mix evenly. Adjust the pH of the system to 4 - 5, and react at 60 - 70 °C for 4 - 6 h. After centrifugation, washing and drying, obtain double-bonded titanium dioxide; Step 3: Mix double-bonded titanium dioxide, sodium dodecyl sulfate, emulsifier OP-10 and deionized water, ultrasonically disperse for 0.5 - 1.0 h, introduce nitrogen, add methyl methacrylate, acrylonitrile, 4-allyloxy-2-hydroxybenzophenone and furan-based compound, heat up to 65 - 75 °C, add potassium persulfate, and react for 4 - 6 h. After filtration, washing and drying, obtain modified nano-titanium dioxide.

4. The polypropylene sling for flexible intermediate bulk container according to claim 3, characterized in that: The mass ratio of the maleic anhydride-modified tea polyphenols, furfurylamine and ethanol is 1:(2 - 4):(10 - 12).

5. The polypropylene sling for flexible intermediate bulk container according to claim 4, characterized in that: The preparation steps of the maleic anhydride-modified tea polyphenols are as follows: Mix tea polyphenols and ethyl acetate evenly, add maleic anhydride and pyridine, react at 45 - 55 °C for 5 - 7 h, carry out rotary evaporation under reduced pressure, recrystallize and freeze-dry to obtain maleic anhydride-modified tea polyphenols.

6. The polypropylene sling for flexible intermediate bulk container according to claim 3, characterized in that: In the said Step 2, the mass ratio of nano-titanium dioxide, anhydrous ethanol, deionized water and 3-(methacryloyloxy)propyltrimethoxysilane is 1:(15 - 20):(3 - 5):(1 - 3).

7. The polypropylene sling for flexible intermediate bulk container according to claim 3, characterized in that: In the said Step 3, the modified nano-titanium dioxide is composed of the following weight parts of components: 10 - 20 parts of double-bonded titanium dioxide, 1 - 2 parts of sodium dodecyl sulfate, 0.1 - 0.5 part of emulsifier OP-10, 200 - 500 parts of deionized water, 10 - 15 parts of methyl methacrylate, 15 - 20 parts of acrylonitrile, 1 - 5 parts of 4-allyloxy-2-hydroxybenzophenone, 5 - 10 parts of furan-based compound, and 1 - 5 parts of potassium persulfate.

8. The polypropylene sling for flexible intermediate bulk container according to claim 1, characterized in that: The compatibilizer is one or a mixture of polypropylene grafted with maleic anhydride and polyethylene grafted with maleic anhydride.

9. A polypropylene sling for a flexible intermediate bulk container according to claim 1, wherein: The lubricant is one or a mixture of polypropylene wax, polyethylene wax, silicone masterbatch, polytetrafluoroethylene, paraffin powder.

10. A preparation process for polypropylene slings for flexible intermediate bulk containers, characterized in that: It includes the following steps: The modified polypropylene and modified nano-titanium dioxide are blended for 10 - 20 minutes at a blending temperature of 130 - 140 °C. Then, polypropylene, high-density polyethylene, talcum powder, compatibilizer, lubricant and antioxidant are added and mixed evenly to obtain a mixed material. The mixed material is poured into an extruder, melt-extruded into a film, cut into filaments, stretched and heat-set to make raw filaments, and then woven into slings by a sling machine to obtain polypropylene slings for flexible intermediate bulk containers.