Preparation method of high-performance polyester safety protection net

Abstract

This invention relates to a method for preparing a high-performance polyester safety net, belonging to the technical field of polyester fiber. The preparation method includes the following steps: (1) staged heating to 215℃ and holding at a constant temperature for 16 hours for deep viscosity enhancement; (2) mixing viscosity enhancement chips, color masterbatch, and flame retardant according to the formula; (3) extruding the mixture, melting and removing impurities, and then high-pressure spinning; (4) water cooling the melt to form nascent yarn, which is then stretched in hot water and heat-dried for shaping; (5) pressing the monofilaments and then winding them to form high-strength PET yarn; (6) warp weaving the raw yarn to form a mesh fabric; (7) cutting, sewing, riveting, and threading ropes into the mesh fabric to make a safety net. This invention improves the intrinsic viscosity and molecular weight of polyester chips through solid-phase polycondensation and chain extension viscosity enhancement technology, improves the hydrolysis resistance of polyester fiber, optimizes the spinning process to reduce thermal degradation, improves the utilization efficiency of raw materials, and reduces raw material loss during the production process.

Description

Technical Field

[0001] This invention belongs to the technical field of polyester fibers, and specifically relates to a method for preparing a high-performance polyester safety net. Background Technology

[0002] Safety nets are essential labor protection equipment on construction sites and are also widely used in high-altitude and overhead operations such as shipbuilding, ship repair, and bridge construction. The standard GB5725-2009 "Safety Nets" specifies clear requirements for their strength, weather resistance, and impact resistance. Currently, safety nets on the domestic and international markets are mainly made of polypropylene and polyethylene. These products have significant performance defects: polypropylene has poor heat resistance and light resistance, and is prone to oxidation and decomposition outdoors, resulting in nets with low impact resistance; polyethylene has poor heat resistance, low elongation at break, and high brittleness, making it prone to cracking during molding and processing, and its knot strength tends to drop sharply. Neither of these materials can meet the requirements for high-quality safety nets.

[0003] Polyester (PET) fiber possesses excellent mechanical properties, good chemical stability, and superior heat and light resistance, making it an ideal raw material to replace polypropylene and polyethylene in the preparation of safety nets. However, existing polyester fiber and safety net preparation technologies have several problems: First, conventional polyester monofilaments lack sufficient strength, making it difficult to balance fiber strength and elongation with lightweight properties, limiting their use to low-end products such as sunshade nets and bird nets. Second, polyester fiber has a limiting oxygen index of only 21%~22%, classifying it as a flammable material with no flame-retardant properties, thus failing to meet the fire resistance requirements of safety nets. Third, excessive damage to polyester fibers occurs during the warp knitting and weaving processes of safety nets, leading to a decline in the quality and performance of the final product. Fourth, systematic solutions have not yet been developed for technologies such as the control of physical property parameters during polyester chip processing and the thermal degradation control of melt spinning, affecting the preparation of high-strength functionalized polyester fibers.

[0004] In existing technologies, the modification of polyester fibers and the forming of safety nets mostly employ conventional processes, lacking a comprehensive optimized design for the entire process to meet the specific needs of safety net applications. The integration of techniques such as polyester chip adhesion enhancement, functional modification, and low-damage forming has not been achieved, resulting in polyester safety nets that struggle to simultaneously achieve high strength, high durability, flame retardancy, and lightweight properties, thus failing to fully replace low-end polypropylene and polyethylene safety net products. Therefore, there is an urgent need in this field for a comprehensive, high-quality polyester safety net manufacturing method to address these technical deficiencies and improve the overall performance of polyester safety nets. Summary of the Invention

[0005] To address the technical problems of low strength and poor durability in existing polyester fiber modified protective nets, this invention provides a method for preparing a high-performance polyester safety protective net to solve these problems. High strength of polyester chips is achieved through solid-phase polycondensation and chain extension to increase viscosity. Functional modifications such as flame retardancy, coloring, and aging resistance of polyester fibers are completed through online additive technology. The high-viscosity polyester melt spinning process is optimized to reduce thermal degradation. Simultaneously, low-damage warp knitting / weaving forming technology for the protective net is developed, forming a complete process technology system from polyester chips to finished protective nets. This results in a polyester safety protective net that combines high strength, high durability, flame retardancy, and lightweight properties.

[0006] The technical solution of this invention is as follows: A method for preparing a high-performance polyester safety net includes the following steps: (1) Take polyester chips, wash and dry them.

[0007] (2) To address the problem of insufficient strength in polyester monofilaments, polyester chips were treated with a solid-state polycondensation process. The chips underwent a deep viscosity-enhancing treatment, with the following steps: heating from room temperature to 180°C for 2.5 hours; then heating from 180°C to 200°C for 3 hours; then heating from 200°C to 215°C for another 3.5 hours; and finally maintaining a constant temperature of 215°C for 16 hours. Through solid-state polycondensation (SSP) treatment, the intrinsic viscosity of the polyester chips was significantly improved. This indicates that the solid-state polycondensation process exhibits excellent viscosity-enhancing effects. Mechanistically, the 215°C treatment temperature selected in this invention is close to the melting point of polyester. Under the long-term high-temperature action, the mobility of molecular chain segments is greatly enhanced, which is conducive to the diffusion and removal of small molecule byproducts generated by the polycondensation reaction within the solid phase. The effective removal of byproducts breaks the reaction equilibrium, promoting further polymerization and growth of molecular chains, thereby providing the necessary high-viscosity matrix for the preparation of high-strength industrial yarns. In addition, the low standard deviation and dispersion of the data verify the stability of the process and ensure the reliability of the experimental results.

[0008] (3) The polyester chips obtained in step (1) after solid-phase polycondensation are mixed with color masterbatch and flame retardant; the proportions of each component during mixing are as follows: 96%~98% of the polyester chips after solid-phase polycondensation, 1%~3% of the color masterbatch, and 0.5%~2% of the flame retardant.

[0009] (4) The ingredients obtained in step (3) are fed into the plastic extruder, heated and melted by the heater in sections, and the impurities in the melt are separated by the monomer switching filter device. The melt is sent into the spinning box by the spinning metering pump and extruded by the spinning assembly under high pressure.

[0010] (5) The melt extruded by the spinning assembly under high pressure is cooled in a cold water bath to generate 16~115 filaments of nascent filament. After being wound by cold rollers, it is stretched 3~5 times by two seven-axis stretching machines in a hot water tank to enhance the tensile strength of the single filament. Then, it is high-temperature sizing by a seven-axis setting machine in a hot oven at 200℃~240℃.

[0011] (6) After the drawn and shaped monofilaments pass through the wire pressing device, they are collected and wound into the winding head by the winding machine to form PET filaments with high tensile strength.

[0012] (7) The winding head is loaded into the warp knitting machine to divide the yarn bundle into single filaments and thread them into the guide ring to weave into a mesh, thus obtaining a high-performance polyester safety net.

[0013] Furthermore, the cut mesh fabric is sewn, riveted, and strung with ropes to create a safety net.

[0014] Furthermore, in step (2), the intrinsic viscosity of the polyester chips after solid-phase polycondensation is ≥0.841dL / g and the moisture content is ≤50ppm.

[0015] Furthermore, the flame retardant is a phosphorus-based flame retardant, including aluminum diethylphosphonate, ammonium polyphosphate, and melamine polyphosphate.

[0016] Furthermore, in step (1), the polyester chips can be made from recycled waste polyester bottles as raw materials, which are crushed, cleaned, and pretreated to obtain polyester chips that meet the requirements.

[0017] Furthermore, in step (5), the heating zones are: Zone 1 170℃~175℃, Zone 2 190℃~195℃, Zone 3 220℃~240℃, Zone 4 260℃~270℃, Zone 5 280℃~290℃, and Zone 6 280℃~290℃.

[0018] Furthermore, in step (4), the high-pressure extrusion pressure is 8~14MPa.

[0019] Furthermore, in step (5), the water temperature in the hot water tank is 85℃~97℃.

[0020] The beneficial effects of this invention are as follows: (1) This invention improves the intrinsic viscosity and molecular weight of polyester chips through solid-phase polycondensation and chain extension and thickening technology, improves the hydrolysis resistance of polyester fibers, optimizes the spinning process to reduce thermal degradation, improves the utilization efficiency of raw materials, and reduces raw material loss in the production process.

[0021] (2) The polyester safety net prepared by the present invention has the characteristics of high strength, high durability, flame retardancy and lightweight. All performance indicators meet and exceed the requirements of national standards. It can completely replace the low-end polypropylene and polyethylene safety net products on the market and solve the problems of poor weather resistance, insufficient strength and low safety guarantee coefficient of traditional products.

[0022] (3) The present invention uses phosphorus-based flame retardants, high color fastness masterbatches and other additives for online modification, realizing a multifunctional composite of flame retardancy and coloring, avoiding fiber damage caused by post-finishing processes, and reducing environmental pollution. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0024] Example 1 Research on solid-state polycondensation of polyester chips Polyester chips are taken and subjected to a deep adhesion-enhancing treatment. The specific process is as follows: Polyester chips were placed in a reactor and heated from room temperature to 180°C over 2.5 hours; then from 180°C to 200°C over 3 hours; then from 200°C to 215°C over another 3.5 hours; finally, the temperature was maintained at 215°C for 16 hours. After cooling, solid-state polycondensation polyester chips were obtained. The following tests were performed on the obtained solid-state polycondensation polyester chips.

[0025] (1) The polyester chips after solid-state polycondensation were titrated with a potassium hydroxide-ethanol standard solution. The results showed that the end carboxyl content of the original chips was 26 mol / t, and the end carboxyl content of the chips after treatment at 215℃ for 16 h was 22 mol / t. Calculations showed that the end carboxyl content of the chips after solid-state polycondensation decreased by 15% compared with the original chips. The decrease in end carboxyl content indicates that an effective chain extension reaction occurred in the system, and the molecular weight increased. However, the reaction kinetics were relatively slow at this temperature.

[0026] (2) Thermogravimetric (TG) experiments were conducted on the polyester chips after solid-state polycondensation. The TG data of the chips in nitrogen are shown in Table 1 below.

[0027] Table 1 - TG data of slices in nitrogen

[0028] As can be seen from the test data in Table 1, the T value of the slice... 5% All samples were processed at 437℃~438℃ with very minor fluctuations. Despite prolonged treatment, the main molecular structure remained intact, with no significant oxidation or degradation reactions observed. Furthermore, T... 5% The higher temperature indicates that the polyester material has excellent thermal stability, which allows for better processing in subsequent spinning processes.

[0029] Maximum decomposition temperature T max The temperature gradually decreased from 478.88℃ to 473.57℃, indicating that vinyl ester (VE) groups and acetaldehyde (AA) are formed during the degradation process, altering the thermal stability. The char residue at 700℃, R... 700 The gradual increase indicates that cross-linking reactions may occur during solid-phase polycondensation, and carbonization reactions are more likely to occur at high temperatures.

[0030] (3) The results of the differential scanning calorimeter test are shown in Table 2.

[0031] Table 2 - Differential Scanning Calorimeter Test Results

[0032] A single heating process records all the heat treatment processes the sample undergoes in the reactor (such as solid-state polycondensation, SSP). This reflects the current processing state of the sample. As the temperature and time of solid-state polycondensation increase, the melting point gradually rises. Therefore, the prolonged high-temperature treatment during solid-state polycondensation allows sufficient time for the PET molecular chains to rearrange, forming thicker and more complete grains.

[0033] With the enhancement of solid-state polycondensation conditions, a greater degree of supercooling is required during melt cooling to induce crystallization, significantly delaying the crystallization process. Simultaneous analysis of the crystallization enthalpy reveals a gradual decrease with time and temperature, indicating a reduction in the cooling crystallization ability of the slices after solid-state polycondensation.

[0034] Research on phosphorus-based flame retardants (1) Take phosphorus flame retardant (aluminum diethylphosphinate (AlPi): melamine polyphosphate (MPP): high degree of polymerization type II APP ternary phosphorus nitrogen compound masterbatch = 6:3:1) and conduct thermogravimetric (TG) test on phosphorus flame retardant. The TG data of phosphorus flame retardant in nitrogen are shown in Table 3 below.

[0035] Table 3 - TG data of phosphorus-based flame retardants in nitrogen gas

[0036] As can be seen from the test data in Table 3, the T of the flame retardant 5% The temperature was 400.77℃, indicating that it has good thermal stability within the conventional PET melt processing range. maxAt 460.22℃, it is beneficial to exert the flame-retardant effect during the heating stage. In addition, R 700 Reaching 17.285%, it has the effect of condensing into charcoal, thus better exerting its flame-retardant effect.

[0037] (2) The results of the differential scanning calorimeter test are shown in Table 4.

[0038] Table 4 - Differential Scanning Calorimeter Test Results

[0039] The DSC curves of the flame retardant masterbatch show two melting endothermic peaks during both the first and second heating processes, possibly attributed to the presence of crystal groups with different layer thicknesses. The cooling curve shows a high-temperature crystallization peak with a sharp peak, indicating strong nucleation ability and a high crystallization temperature.

[0040] Example 2 A method for preparing a high-performance polyester safety net includes the following steps: (1) Take polyester chips, wash and dry them.

[0041] (2) The polyester chips were subjected to solid-state polycondensation and deep viscosity enhancement treatment. The process was as follows: the temperature was raised from room temperature to 180°C in 2.5 hours; then raised from 180°C to 200°C in 3 hours; then raised from 200°C to 215°C in 3.5 hours; and finally held at 215°C for 16 hours. The intrinsic viscosity of the polyester chips after solid-state polycondensation was 1.020 dL / g and the moisture content was 50 ppm.

[0042] (3) The polyester chips obtained in step (2) after solid-state polycondensation are mixed with color masterbatch and flame retardant, including the following components by weight percentage: 97% polyester chips after solid-state polycondensation, 2% color masterbatch (G4272A for polyester) and 1% flame retardant.

[0043] (4) The ingredients obtained in step (3) are fed into a plastic extruder and heated and melted by a heater in sections. The heating sections are: Zone 1 170℃~175℃, Zone 2 190℃~195℃, Zone 3 220℃~240℃, Zone 4 260℃~270℃, Zone 5 280℃~290℃, and Zone 6 280℃~290℃. Impurities in the melt are separated by a monomer switching filter. The melt is fed into the spinning box by a spinning metering pump at a conveying pressure of 10MPa and extruded under high pressure by a 192~400 hole spinneret of the spinning assembly.

[0044] (5) The melt extruded by the spinning assembly under high pressure is cooled in a cold water bath at 50℃~55℃ to generate 16~115 filaments of nascent filament. After being wound by cold rollers, it is stretched 3~5 times by two seven-axis drawing machines in an 85℃ hot water bath, thereby enhancing the tensile strength of the single filament. Then, it is high-temperature sizing by a seven-axis setting machine in a hot oven at 220℃.

[0045] (6) After the drawn and shaped monofilaments pass through the wire pressing device, they are collected and wound into the winding head by the winding machine to form PET filaments with high tensile strength.

[0046] (7) The winding head is loaded into the warp knitting machine to divide the yarn bundle into single filaments and thread them into the guide ring to weave into a mesh.

[0047] (8) The cut mesh is sewn, riveted, and roped to make a safety net.

[0048] Example 3 A method for preparing a high-performance polyester safety net includes the following steps: (1) Take the recycled waste polyester bottles, crush and clean them, and obtain polyester chips that meet the requirements after pretreatment.

[0049] (2) The polyester chips were subjected to solid-state polycondensation and deep viscosity enhancement treatment. The process was as follows: the temperature was raised from room temperature to 180°C in 2.5 hours; then raised from 180°C to 200°C in 3 hours; then raised from 200°C to 215°C in 3.5 hours; and finally held at 215°C for 16 hours. The intrinsic viscosity of the polyester chips after solid-state polycondensation was 1.020 dL / g and the moisture content was 50 ppm.

[0050] (3) The polyester chips obtained from solid-state polycondensation in step (2) are mixed with color masterbatch and flame retardant, including the following components by weight percentage: 98% polyester chips obtained from solid-state polycondensation, 1.5% color masterbatch (G4272A for polyester) and 0.5% flame retardant.

[0051] (4) The ingredients obtained in step (3) are fed into a plastic extruder and heated and melted by a heater in sections. The heating sections are: Zone 1 170℃~175℃, Zone 2 190℃~195℃, Zone 3 220℃~240℃, Zone 4 260℃~270℃, Zone 5 280℃~290℃, and Zone 6 280℃~290℃. Impurities in the melt are separated by a monomer switching filter. The melt is fed into the spinning box by a spinning metering pump at a conveying pressure of 10MPa and extruded under high pressure by a 192~400 hole spinneret of the spinning assembly.

[0052] (5) The melt extruded by the spinning assembly under high pressure is cooled in a cold water bath at 50℃~55℃ to generate 16~115 filaments of nascent filament. After being wound by cold rollers, it is stretched 3~5 times by two seven-axis drawing machines in a hot water bath at 86℃, thereby enhancing the tensile strength of the single filament. Then, it is high-temperature sizing by a seven-axis setting machine in a hot oven at 220℃.

[0053] (6) After the drawn and shaped monofilaments pass through the wire pressing device, they are collected and wound into the winding head by the winding machine to form PET filaments with high tensile strength.

[0054] (7) The winding head is loaded into the warp knitting machine to divide the yarn bundle into single filaments and thread them into the guide ring to weave into a mesh.

[0055] (8) The cut mesh is sewn, riveted, and roped to make a safety net.

[0056] Test case Eight products were randomly selected from the products prepared in Examples 2 and 3, and their performance was tested according to the standard GB5725-2025. The test results are shown below: 1. Appearance and structural design inspection

[0057] 2. Static mechanical strength test of the netting

[0058] 3. Flame retardant performance test

[0059] 4. Impact resistance test Test conditions: Impact energy ≥1550±20J, 100kg standard test weight, impacting the geometric center of the net.

[0060] Judgment requirements: The net rope, edge rope, and tie rope must not be broken.

[0061] Actual test results: The products prepared in Examples 2 and 3 were subjected to impact tests. The net body was not torn, the side ropes and net ropes were not broken, and the weight did not penetrate the net body. They met the standard requirements and were judged to be qualified.

[0062] 5. Penetration resistance test Test conditions: 5kg sharp penetrating rod, impact energy ≥155±5J.

[0063] Standard requirement: The penetrating rod must not penetrate the net.

[0064] Test results: After testing, the products prepared in Examples 2 and 3 showed no through holes in the mesh, only slight indentations on the surface, and were deemed qualified.

[0065] 6. Corrosion resistance (metal ring, GB / T 10125 neutral salt spray 48h) Standard requirements: Metal parts must be free of red rust and obvious corrosion; Test results: All eyelet buckles and metal accessories of the products prepared in Examples 2 and 3 were tested for 48 hours with no rust or oxidation spots, and were deemed qualified.

[0066] 7. Weather resistance test Test cycle: 4h light exposure / 4h condensation cycle, light exposure temperature 60℃; static strength was retested after aging, and the rate of decrease in mechanical properties was calculated.

[0067] Limit: Intensity reduction rate ≤ 20%.

[0068] Test results: The product prepared in Example 2 had a strength reduction rate of 11.3% after aging.

[0069] The product prepared in Example 3 had a strength reduction rate of 12.7% after aging.

[0070] After testing, the products prepared in Examples 2 and 3 both met the requirement of ≤20%, and the mechanical property decay was controllable during long-term outdoor use; at the same time, the phosphorus-based flame retardant did not migrate or precipitate, and the flame retardant performance was retested after aging, with afterflame and smoldering still at 0s, indicating long-term stable flame retardancy.

[0071] In summary, after testing, the high-performance polyester warp-knitted safety net prepared by the online blending and spinning process of solid-phase tackifying PET cutting and phosphorus-nitrogen compound flame retardant of this invention meets all the technical requirements of the new version of the mandatory national standard GB 5725-2025 in all test items. Its mechanical strength, flame retardancy, weather resistance, impact resistance and corrosion resistance are all superior to conventional PE / PP safety nets on the market.

[0072] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for preparing a high-performance polyester safety net, characterized in that, Includes the following steps: (1) The polyester chips have undergone deep adhesion enhancement treatment; (2) The polyester chips obtained from solid-state polycondensation in step (1) are mixed and melted with color masterbatch and flame retardant; (3) The ingredients obtained in step (2) are fed into the plastic extruder, heated and melted by the heater in sections, and the melt is sent into the spinning box by the spinning metering pump and extruded by the spinning assembly under high pressure. (4) The melt extruded by the spinning assembly under high pressure is cooled in a cold water bath to generate 16~115 filaments of raw filament. After being wound by cold rollers, it is stretched by two seven-axis drawing machines through a hot water tank, and then shaped by a seven-axis setting machine through a hot drying oven at high temperature. (5) After the drawn and shaped monofilaments pass through the wire pressing device, they are collected and wound into the winding head by the winding machine to form PET filaments with high tensile strength; (6) The winding head is loaded into the warp knitting machine to divide the yarn bundle into single filaments and thread them into the guide ring to weave into a mesh, thus obtaining a high-performance polyester safety net.

2. The method for preparing the high-performance polyester safety net as described in claim 1, characterized in that, In step (1), recycled waste polyester bottles can be used as raw materials for polyester chips. After crushing, cleaning and pretreatment, polyester chips that meet the requirements are obtained.

3. The method for preparing the high-performance polyester safety net as described in claim 1, characterized in that, The deep adhesion enhancement process for polyester chips is as follows: the polyester chips are heated from room temperature to 180℃ for 2.5 hours; then heated from 180℃ to 200℃ for 3 hours; then heated from 200℃ to 215℃ for another 3.5 hours; and finally kept at 215℃ for 16 hours.

4. The method for preparing the high-performance polyester safety net as described in claim 1, characterized in that, In step (1), the intrinsic viscosity of the polyester chips after solid-phase polycondensation is ≥0.841dL / g and the moisture content is ≤50ppm.

5. The method for preparing the high-performance polyester safety net as described in claim 1, characterized in that, The flame retardant is a phosphorus-based or halogenated flame retardant.

6. The method for preparing the high-performance polyester safety net as described in claim 1, characterized in that, In step (3), the high-pressure extrusion pressure is 8~14MPa.

7. The method for preparing the high-performance polyester safety net as described in claim 1, characterized in that, In step (4), the heating zones are: Zone 1 170℃~175℃, Zone 2 190℃~195℃, Zone 3 220℃~240℃, Zone 4 260℃~270℃, Zone 5 280℃~290℃, and Zone 6 280℃~290℃.

8. The method for preparing the high-performance polyester safety net as described in claim 1, characterized in that, In step (4), after being wound by cold rollers, the material is stretched 3 to 5 times by two seven-axis stretching machines through a hot water tank.

9. The method for preparing the high-performance polyester safety net as described in claim 1, characterized in that, In step (4), the high-temperature setting temperature is 200℃~240℃.

10. The method for preparing the high-performance polyester safety net as described in claim 1, characterized in that, In step (4), the water temperature in the hot water tank is 85℃~97℃.

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