Manufacturing method of low-cost recyclable spun-bonded non-woven fabric capable of replacing traditional kraft paper

Abstract

The invention relates to the technical field of spunbond non-woven fabric manufacturing, in particular to a low-cost recyclable spunbond non-woven fabric manufacturing method capable of replacing traditional kraft paper, and the method comprises the steps of raw material preparation, melt extrusion, spinning web forming, hot-press shaping, cooling and trimming, post-processing, coiling and forming and the like. Raw materials comprise polypropylene particles, degradable master batches and recycled spunbond non-woven fabric fragments, the recycled fragments are subjected to surface modification treatment, and the degradable master batches contain polylactic acid, a starch-based degradation agent and other components. The non-woven fabric is quantified to 80-120 g / m < 2 > by optimizing processes such as a barrier type screw, infrared preheating and laser trimming and cooperating with water-repellent and antistatic post-treatment, the mechanical properties such as tensile strength, tearing strength and folding resistance are superior to those of traditional kraft paper, the non-woven fabric can be recycled for at least three times, and the degradation period is controllable; the method realizes closed-loop utilization of raw materials, reduces cost and energy consumption, expands application in the fields of packaging, agriculture and the like, and has remarkable economic and environmental benefits.

Description

Technical Field

[0001] The invention relates to the technical field of spunbond nonwoven fabric manufacturing, in particular to a method for manufacturing spunbond nonwoven fabric that is low-cost and recyclable and can replace traditional kraft paper. Background Art

[0002] Traditional kraft paper, a widely used material in packaging, agriculture, logistics, and other fields, is primarily composed of plant fibers, possessing considerable tensile strength and biodegradability. It has long been the mainstream choice for industrial packaging. However, with rising global environmental awareness, the limitations of traditional kraft paper have become increasingly apparent. On the one hand, its production is highly dependent on wood resources, leading to deforestation and ecological pressure. On the other hand, kraft paper suffers from defects such as poor water resistance, low folding strength, and non-recyclability, making it difficult to meet modern industry's demand for high-strength, multifunctional, and sustainable materials.

[0003] The comparative document CN119748998A discloses a method for preparing functional composite non-woven fabrics, which improves the comfort of non-woven fabrics for masks through a double-layer structure and air-freshening particles, but does not involve low-cost recycling and high-strength packaging performance; the comparative document CN111764048A focuses on the recycling of ultra-high molecular weight polyethylene waste to prepare needle-punched non-woven fabrics, emphasizing the recycling of high-performance fibers, but does not solve the problems of degradability and functional post-processing required to replace kraft paper.

[0004] The technical defects of traditional kraft paper are analyzed as follows:

[0005] 1. Resource consumption and environmental burden

[0006] Traditional kraft paper uses wood fiber as its main raw material, and the production process consumes a large amount of forest resources. According to statistics, 2-3 cubic meters of wood are consumed for each ton of kraft paper produced, exacerbating global deforestation and ecological imbalance. In addition, although kraft paper can be degraded after being discarded, it is easy to produce fiber fragment pollution during the degradation process, and the recycling cost is high. The strength of recycled paper will decrease significantly with the number of recycling times (usually it can only be recycled 3-4 times, and the strength retention rate is less than 60%), making it difficult to form an effective closed loop. Although the waste silk recycling technology in the comparative document CN111764048A achieves high-performance fiber recycling, traditional kraft paper lacks a similar efficient recycling system, resulting in serious waste of resources.

[0007] 2. Insufficient physical performance

[0008] Strength and durability defects: The tensile strength (about 60-70N / 5cm in the longitudinal direction) and folding endurance (2000-3000 times) of kraft paper are low. It is easily damaged in heavy-load packaging and multiple folding scenarios, and cannot meet the long-term use requirements in express logistics, industrial packaging bags and other fields.

[0009] Single function: Traditional kraft paper does not have functions such as waterproof and anti-static. It easily absorbs water and softens in a humid environment. There is a risk of electrostatic damage when used for electronic device packaging. The comparative document CN119748998A gives non-woven fabrics water-repellent and air-freshening functions through surface treatment, highlighting the gap in the functionalization of kraft paper.

[0010] 3. Non-recyclable and high cost

[0011] The fiber structure of kraft paper will be severely damaged after multiple processing, resulting in a significant decrease in the performance of recycled paper. In addition, the scraps and waste generated during the production process are difficult to effectively utilize, resulting in waste of raw materials and increased costs.

[0012] 4. Production process and energy consumption issues

[0013] Kraft paper production requires complex processes such as pulping, bleaching, and papermaking, resulting in high energy consumption (approximately 3.5 tons of standard coal per ton of paper) and significant pollution emissions (e.g., black liquor disposal issues). In contrast, spunbond nonwovens, through melt extrusion and hot-rolling, consume less energy and can be further optimized through barrier screws and segmented heating technologies, aligning with the trend toward green manufacturing. Summary of the Invention

[0014] The object of the present invention is to provide a method for manufacturing a spunbond nonwoven fabric that is low-cost and recyclable and can replace traditional kraft paper, so as to solve the problems raised in the above background technology.

[0015] To achieve the above object, the present invention provides the following technical solutions:

[0016] A method for manufacturing a low-cost, recyclable spunbond nonwoven fabric that can replace traditional kraft paper comprises the following steps:

[0017] S1. Raw material preparation: 60-80% polypropylene particles, 10-20% biodegradable masterbatch, and 10-30% recycled spunbond non-woven fabric fragments are mixed uniformly by weight, and the surface of the recycled spunbond non-woven fabric fragments is treated with a silane coupling agent solution with a concentration of 0.5-1.5% and a treatment time of 5-15 minutes;

[0018] S2. Melt extrusion: The mixed raw materials are fed into a screw extruder, melted and plasticized at 180-220°C, and transported to the spinning assembly via a metering pump. The screw extruder adopts a barrier screw with an aspect ratio of 30-35:1 and a screw speed of 150-200 r / min;

[0019] S3, spinning into web: The polypropylene melt is extruded through a spinning die to form a thin stream, which is drawn into monofilaments by a high-speed airflow of 15-25 m / s. The drawing airflow temperature is 60-80°C, and the monofilament diameter is controlled at 1.5-3 μm. The monofilaments are then evenly spread to form a fiber web;

[0020] S4. Hot pressing and shaping: The fiber web is transported to the hot rolling mill. The surface of the hot rolling mill roll is provided with diamond patterns with a pattern depth of 0.1-0.3mm and a pattern density of 20-30 pieces / cm 2 , hot rolling bonding is carried out at 110-150℃ and pressure 0.3-0.8MPa, and the fiber web is infrared preheated before hot rolling at a preheating temperature of 80-100℃;

[0021] S5. Cooling and trimming: The hot-rolled non-woven fabric is cooled by air, and the cooling rate is controlled at 5-10°C / s. The edge burrs are then removed by a laser trimming device. The collected edge materials are crushed into a particle size of 0.5-2mm by a low-temperature grinder and set aside.

[0022] S6. Post-treatment: The cooled non-woven fabric is subjected to water repellent treatment and antistatic treatment in sequence. The water repellent treatment makes the surface contact angle of the non-woven fabric ≥110°, and the antistatic treatment makes the surface resistivity ≤1×10 9 Ω·cm;

[0023] S7, Rolling and forming: The treated non-woven fabric is rolled into a finished product with a weight of 80-120g / m 2 , longitudinal tensile strength ≥80N / 5cm, transverse tensile strength ≥60N, tear strength longitudinal ≥30N, transverse ≥25N.

[0024] Preferably, the degradable masterbatch is composed of the following components by weight: 20-30% polylactic acid PLA, 10-20% starch-based degradation agent, 5-10% maleic anhydride grafted polypropylene compatibilizer, 0.5-1% hindered phenol antioxidant, and the balance is polypropylene carrier.

[0025] Preferably, the preparation method of the recycled spunbond non-woven fabric fragments described in step S1 includes: crushing and screening the waste spunbond non-woven fabric, immersing it in a sodium hydroxide solution with a mass concentration of 1-3%, treating it at 50-70°C for 10-20 minutes to remove surface impurities, washing it with clean water and drying it, and then immersing it in a γ-aminopropyltriethoxysilane solution for surface modification, whereby the surface hydroxyl content of the fragments is increased by 20-30% after modification.

[0026] Preferably, in step S2, the melt pressure of the screw extruder is controlled at 8-12 MPa, and the barrel is heated in three sections, with the temperature of the first section at 180-190°C, the temperature of the second section at 190-210°C, and the temperature of the third section at 210-220°C.

[0027] Preferably, the diameter of the spinneret holes of the spinning die in step S3 is 0.2-0.4 mm, the spinneret holes are distributed in a hexagonal array with an arrangement density of 15-20 holes / cm, and the aspect ratio of the spinneret holes is 8-12:1.

[0028] Preferably, the scrap collected in step S5 is recycled to step S1 at a ratio of 5-15% of the total weight of the new raw materials. When recycled, the scrap and the new raw materials are mixed for ≥10 min and at a mixing speed ≥300 r / min.

[0029] Preferably, the antistatic treatment in step S6 is as follows: the non-woven fabric is immersed in an aqueous solution containing 0.3-0.8% quaternary ammonium salt antistatic agent by a padding process, with the padding rate controlled at 60-80%, and then dried at 90-110° C. for 10-15 minutes.

[0030] Preferably, the finished non-woven fabric has a folding endurance of ≥5000 times, a mass deviation per unit area of ≤±3%, and is recycled at least 3 times through a crushing-melting-spinning process. After recycling, the longitudinal tensile strength retention rate is ≥85%, and the transverse tensile strength retention rate is ≥80%.

[0031] Preferably, the waste finished non-woven fabric is crushed to a particle size of ≤2 mm, and then impurities are removed through a metal detector. Then, the waste finished non-woven fabric is mixed with polypropylene particles and degradable masterbatch at a ratio of 10-30% of the total weight of the new raw materials, and the moisture content of the mixed raw materials is controlled to ≤0.1%.

[0032] Preferably, the finished non-woven fabric is used to replace traditional kraft paper to prepare industrial packaging bags, agricultural seedling bags or express envelopes. The load-bearing capacity of the packaging bags is ≥15kg, and the degradation period of the seedling bags in natural soil is ≥12 months and ≤24 months.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. Significantly reduce costs and resource consumption

[0035] 1. Closed-loop utilization of raw materials

[0036] By recycling waste spunbond non-woven fabric fragments (accounting for 10-30%) and production scraps (recycling ratio 5-15%), the amount of new polypropylene material used can be reduced and the raw material cost can be reduced by 30%-50%.

[0037] Starch-based degraders and polylactic acid (PLA) are introduced into the biodegradable masterbatch, and low-cost natural polymers are used to replace part of the petroleum-based raw materials, further reducing the formulation cost.

[0038] 2. Process energy consumption optimization

[0039] The barrier screw (length-to-diameter ratio 30-35:1) and segmented heating process improve melting efficiency, reducing energy consumption by 15%-20% compared to traditional screws. Infrared preheating of the fiber web (80-100°C) reduces hot rolling energy consumption, and laser trimming technology (replacing mechanical trimming) reduces burr loss to ≤1%.

[0040] 2. High performance alternative to traditional kraft paper

[0041] 1. Comprehensive mechanical properties surpass

[0042] Tensile strength: longitudinal ≥80N / 5cm, transverse ≥60N / 5cm, 14%-33% higher than traditional kraft paper (about 60-70N / 5cm), meeting heavy-load packaging needs.

[0043] The folding endurance is ≥5000 times, far exceeding kraft paper (2000-3000 times) and ordinary non-woven fabrics (3000-4000 times), and is suitable for multiple folding scenarios (such as express envelopes and seedling bags).

[0044] The tearing strength is ≥30N in the longitudinal direction and ≥25N in the transverse direction, with strong puncture resistance, reducing the breakage rate during transportation.

[0045] 2. Expanded application of functional post-processing

[0046] The water-repellent treatment makes the surface contact angle ≥110°, and the waterproof performance is better than kraft paper (contact angle of about 90°), and it can be used for packaging in humid environments (such as fertilizers and agricultural products).

[0047] Antistatic treatment makes the surface resistivity ≤1×10 9 Ω·cm, meeting the electrostatic protection requirements of electronic device packaging and filling the functional gap of kraft paper.

[0048] 3. Environmental sustainability and recycling

[0049] 1. Degradable and low pollution

[0050] The PLA and starch-based degradation agents in the degradable masterbatch control the degradation cycle of non-woven fabrics in natural soil to 12-24 months, avoiding the environmental problems of traditional PP non-woven fabrics (non-degradable) and kraft paper (degradation produces microfibers).

[0051] The surface of the recycled fragments is modified with silane (increasing the hydroxyl content by 20-30%) and a maleic anhydride grafted compatibilizer is used to eliminate interface defects of the recycled material and reduce the waste rate during the production process.

[0052] 2. Efficient recycling system

[0053] Waste non-woven fabrics can be recycled at least three times through "crushing-melting-spinning". After the cycle, the longitudinal strength retention rate is ≥85% and the transverse strength is ≥80%, building a "production-use-recycling" closed loop and breaking the limitation of traditional kraft paper's one-time use.

[0054] 100% recycling of scrap materials, combined with metal detection and moisture content control (≤0.1%), ensures the quality stability of recycled materials and achieves zero waste of resources.

[0055] 4. Process stability and quality controllability

[0056] 1. Precise process parameter design

[0057] Diamond pattern hot rolling roller (depth 0.1-0.3mm, density 20-30 pieces / cm 2 ) Improve the uniformity of fiber web bonding, with the mass deviation per unit area ≤±3%, which is better than the ±5% deviation of kraft paper.

[0058] The hexagonal array distribution of spinneret holes (15-20 holes / cm) and high-speed drawing (15-25m / s) control the diameter of the monofilament to 1.5-3μm, resulting in a dense fiber web structure and a smooth and flawless surface.

[0059] 2. Adaptability to large-scale production

[0060] The parameter range of screw speed 150-200r / min and melt pressure 8-12MPa is compatible with existing spunbond equipment, eliminating the need for large-scale equipment modification and lowering the threshold for industrialization.

[0061] V. Industrial Value and Social Benefits

[0062] Replace traditional kraft paper: "Replace paper with plastic" in industrial packaging bags (load-bearing ≥ 15kg), agricultural seedling bags (degradation cycle controllable), express envelopes and other fields to alleviate the shortage of wood resources.

[0063] Compared with kraft paper production (energy consumption per ton of paper is about 3.5 tons of standard coal), this process reduces energy consumption by more than 40% and significantly reduces carbon emissions, which is in line with the global green manufacturing trend. DETAILED DESCRIPTION

[0064] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0065] A low-cost, recyclable alternative to traditional kraft paper for spunbond nonwovens is described below:

[0066] (1) Raw material preparation and formula design

[0067] Base material: 60-80% polypropylene (PP) particles form the main component, ensuring the basic mechanical properties of the nonwoven fabric. Added to the base material is 10-20% biodegradable masterbatch, which consists of 20-30% polylactic acid (PLA), 10-20% starch-based degrader, 5-10% maleic anhydride grafted polypropylene (MAPP) compatibilizer, 0.5-1% hindered phenolic antioxidant, and the balance being a PP carrier. The PLA and starch-based degrader impart controllable degradability to the material, while the MAPP improves the compatibility between PLA and PP. The antioxidant inhibits oxidative degradation of the raw materials during processing.

[0068] Recycled material processing: After the waste spunbond non-woven fabric is crushed and screened, it is treated with "alkaline washing and impurity removal-silane modification": first immersed in 1-3% sodium hydroxide solution (50-70℃, 10-20min) to remove surface oil and impurities, washed with clean water and dried, and then immersed in 0.5-1.5% γ-aminopropyltriethoxysilane solution (treatment time 5-15min). The silane coupling agent grafting reaction increases the surface hydroxyl content of the fragments by 20-30%, thereby enhancing the interface bonding with the new raw materials.

[0069] (2) Key process steps

[0070] Melt extrusion: Utilizing a barrier screw (length-to-diameter ratio of 30-35:1), three-stage barrel heating (first section: 180-190°C, second section: 190-210°C, third section: 210-220°C), melt pressure controlled at 8-12 MPa, and screw speed at 150-200 r / min. The barrier screw promotes uniform melting of the material, and segmented heating ensures thorough mixing of the recycled and virgin materials, preventing local overheating and degradation.

[0071] Spinning web: The spinning die has spinneret holes with a diameter of 0.2-0.4mm, distributed in a hexagonal array (density 15-20 holes / cm), and an aspect ratio of 8-12:1, ensuring stable extrusion of the melt stream; it is drawn into monofilaments (diameter 1.5-3μm) by a 15-25m / s high-speed airflow (temperature 60-80℃). The fine denier fibers enhance the softness and strength of the non-woven fabric.

[0072] Hot pressing shaping: The surface of the hot rolling mill roll is provided with diamond pattern (depth 0.1-0.3mm, density 20-30 / cm 2 ) Before hot rolling, the fiber web is infrared preheated to 80-100°C, and then bonded at 110-150°C and 0.3-0.8 MPa. The patterned structure enhances mechanical interlocking between fibers, and the preheating treatment evens out the fiber web temperature, improving hot rolling efficiency and bonding uniformity.

[0073] Recycling design: The edge materials after cooling and trimming are crushed to 0.5-2mm at low temperature, and reused in new material mixing at a ratio of 5-15% (mixing time ≥10min, rotation speed ≥300r / min). The waste non-woven fabrics are crushed and metal tested to remove impurities, and then mixed with new material at a ratio of 10-30%, with the moisture content controlled at ≤0.1%, to achieve closed-loop utilization of raw materials and reduce costs.

[0074] Functional post-treatment: Water repellent treatment makes the contact angle of the non-woven fabric surface ≥110° to meet the moisture-proof requirements; antistatic treatment adopts padding 0.3-0.8% quaternary ammonium salt antistatic agent aqueous solution (rolling rate 60-80%, 90-110℃ drying 10-15min), surface resistivity ≤1×10 9 Ω·cm, solving the problem of electrostatic adsorption.

[0075] (3) Product performance indicators

[0076] The finished non-woven fabric produced by this manufacturing method has a quantitative value of 80-120g / m 2 , longitudinal tensile strength ≥80N / 5cm, transverse ≥60N, tear strength longitudinal ≥30N, transverse ≥25N, folding endurance ≥5000 times, unit area mass deviation ≤±3%; can be recycled at least 3 times, longitudinal strength retention rate after cycle ≥85%, transverse ≥80%; when used for agricultural seedling bags, the degradation cycle in natural soil is 12-24 months, meeting the needs of different scenarios.

[0077] Example 1

[0078] Low-cost recyclable spunbond nonwoven fabric (medium parameter combination)

[0079] 1. Raw material preparation

[0080] Polypropylene granules: 70%

[0081] Degradable masterbatch: 15% (PLA 25%, starch-based degradant 15%, maleic anhydride grafted polypropylene compatibilizer 8%, antioxidant 0.8%, balance PP carrier)

[0082] Recycled spunbond nonwoven fabric fragments: 15% (treated with 0.5% silane coupling agent for 10 minutes, the surface hydroxyl content increased by 25%)

[0083] 2. Key process parameters

[0084] Melt extrusion: screw aspect ratio 32:1, three temperature stages (185°C, 200°C, 215°C), screw speed 180r / min, melt pressure 10MPa

[0085] Spinning web: spinneret diameter 0.3 mm, hexagonal array (18 holes / cm), drafting airflow 70°C, speed 20 m / s, single filament diameter 2 μm

[0086] Hot pressing: infrared preheating at 90°C, hot rolling temperature at 130°C, pressure at 0.5 MPa, roller pattern depth at 0.2 mm, density at 25 pieces / cm 2

[0087] Post-treatment: water repellent treatment (1% organic silicon water repellent, surface contact angle 115°) + antistatic treatment (0.5% quaternary ammonium salt, surface resistivity 8×10 8 Ω·cm)

[0088] Recycling of scrap material: recycling ratio 10%, mixing time 15min, speed 400r / min

[0089] 3. Performance testing

[0090] Basis weight: 100g / m 2

[0091] Tensile strength: 90N / 5cm in longitudinal direction, 70N / 5cm in transverse direction

[0092] Tear strength: longitudinal 35N, transverse 30N

[0093] Folding times: 6000 times

[0094] Strength retention after 3 cycles: 88% in longitudinal direction, 83% in transverse direction

[0095] Example 2

[0096] High recycled material ratio example (recycled chips 30%)

[0097] 1. Raw material preparation

[0098] Polypropylene granules: 60%

[0099] Degradable masterbatch: 10% (PLA 20%, starch-based degradant 10%, compatibilizer 5%, antioxidant 0.5%, balance PP carrier)

[0100] Recycled spunbond nonwoven fabric fragments: 30% (treated with 1.5% silane coupling agent for 5 minutes, the surface hydroxyl content increased by 22%)

[0101] 2. Key process parameters

[0102] Melt extrusion: screw aspect ratio 30:1, three temperature stages (180°C, 195°C, 210°C), screw speed 150r / min

[0103] Hot pressing: hot rolling temperature 110℃, pressure 0.3MPa, pattern density 20 / cm 2 Recycling of scrap material: recycling ratio 5%, mixing time 10min, speed 300r / min

[0104] 3. Performance testing

[0105] Basis weight: 80g / m 2

[0106] Tensile strength: 85N / 5cm in longitudinal direction, 65N / 5cm in transverse direction

[0107] Folding times: 5500 times

[0108] Strength retention after 3 cycles: 85% in longitudinal direction, 80% in transverse direction

[0109] Example 3

[0110] High mechanical performance example (low recovery fragments 10%)

[0111] 1. Raw material preparation

[0112] Polypropylene granules: 80%

[0113] Degradable masterbatch: 20% (PLA 30%, starch-based degradant 20%, compatibilizer 10%, antioxidant 1%, balance PP carrier)

[0114] Recycled spunbond nonwoven fabric fragments: 10% (treated with 1% silane coupling agent for 15 minutes, the surface hydroxyl content increased by 30%)

[0115] 2. Key process parameters

[0116] Spinning web: spinneret diameter 0.25mm, drafting airflow 80℃, speed 25m / s, single filament diameter 1.8μm

[0117] Hot pressing: hot rolling temperature 150℃, pressure 0.8MPa, pattern depth 0.3mm

[0118] Post-treatment: water repellent treatment (surface contact angle 120°) + antistatic treatment (surface resistivity 5×10 8 Ω·cm)

[0119] 3. Performance testing

[0120] Basis weight: 120g / m 2

[0121] Tensile strength: 100N / 5cm in longitudinal direction, 80N / 5cm in transverse direction

[0122] Tear strength: longitudinal 40N, transverse 35N

[0123] Folding times: 7000 times

[0124] Strength retention after 3 cycles: 90% in longitudinal direction, 85% in transverse direction

[0125] Example 4

[0126] Example of high recycling of scrap material (recycling ratio 15%)

[0127] 1. Raw material preparation

[0128] Polypropylene granules: 65%

[0129] Degradable masterbatch: 15%

[0130] Recycled spunbond nonwoven scraps: 20% (including 15% newly generated scraps)

[0131] 2. Key process parameters

[0132] Cooling and trimming: laser trimming, edge material crushed to 1mm particle size, recycling ratio 15% Antistatic treatment: 0.8% quaternary ammonium salt, rolling rate 80%, drying temperature 110℃

[0133] 3. Performance testing

[0134] Basis weight: 90g / m 2

[0135] Tensile strength: 88N / 5cm in longitudinal direction, 68N / 5cm in transverse direction

[0136] Surface resistivity: 9×10 8 Ω·cm

[0137] Density deviation after recycling 3 times: ±2.5%

[0138] Comparative Example 1

[0139] Traditional kraft paper alternative (no recycled scraps + ordinary non-woven fabric process)

[0140] Differentiating Material: 100% polypropylene pellets (no recycled scraps, no biodegradable masterbatch)

[0141] Process: Omit silane coupling agent treatment, infrared preheating, and antistatic treatment Hot rolling: Ordinary smooth roller (no pattern), temperature 160°C, pressure 1.0 MPa Performance defects

[0142] Basis weight: 110g / m 2

[0143] Tensile strength: 70N / 5cm in longitudinal direction (↓12.5%), 50N / 5cm in transverse direction (↓16.7%)

[0144] Folding endurance: 3000 times (↓40%)

[0145] Unable to be recycled (fibers break severely after melting)

[0146] Degradability: None (traditional PP non-woven fabrics are non-degradable)

[0147] Comparative Example 2

[0148] Unmodified recycled material + no compatibilizer

[0149] Differences

[0150] Raw materials: Recycled fragments not treated with silane coupling agent, biodegradable masterbatch does not contain compatibilizer (using ordinary PP carrier)

[0151] Process: Screw length-diameter ratio 25:1 (non-barrier screw)

[0152] Performance flaws

[0153] Tensile strength: 75N / 5cm in longitudinal direction (↓6.25%), 55N / 5cm in transverse direction (↓8.3%)

[0154] Tear strength: longitudinal 25N (↓16.7%), transverse 20N (↓20%)

[0155] Surface defects: fiber agglomeration, increased porosity

[0156] Strength retention after one recycling: 70% in the longitudinal direction (↓15%), 65% in the transverse direction (↓15%)

[0157] The key data comparison table of the above four groups of examples and the two groups of comparative examples is shown in the following table, focusing on the extraction of process parameters and finished product performance indicators for quantitative analysis:

[0158] Table 1

[0159]

[0160]

[0161] Data comparative analysis

[0162] 1. Mechanical performance advantages:

[0163] The longitudinal / transverse tensile strength of the embodiments are significantly higher than those of Comparative Example 1 (traditional process) and Comparative Example 2 (unmodified recycling). Among them, the longitudinal tensile strength of Example 3 reaches 100N / 5cm, which is 42.9% higher than that of Comparative Example 1, meeting the high-strength packaging requirements.

[0164] The folding times are all ≥5000 times, far exceeding the 3000 times of comparative example 1 (traditional kraft paper is about 2000-3000 times), proving that the non-woven fabric has better bending resistance.

[0165] 2. Recycling Capability:

[0166] The embodiment achieves a strength retention rate of ≥80% after three cycles through recycled fragment modification and process optimization, while comparative example 1 cannot be recycled due to the lack of a recycling system, and comparative example 2 suffers from a sharp drop in strength (vertical direction ↓15%) after one cycle due to poor interface compatibility.

[0167] 3. Functional processing effect:

[0168] The surface contact angle of the embodiment is ≥110° after water repellent treatment and the surface resistivity is ≤1×10 9 Ω·cm, which meets the needs of moisture-proof, electronic packaging and other scenarios, while the control ratio has not been double-processed and has a single function.

[0169] 4. Environmental protection and cost:

[0170] Example 2 (recycling ratio 30%) and Example 4 (high recycling of scrap) verified the stable performance under high recycled material ratio. However, since Comparative Example 2 did not use compatibilizer and silane modification, it led to fiber agglomeration and increased defect rate, proving the necessity of the interfacial modification technology in the invention.

[0171] The present invention's low-cost, recyclable spunbond nonwoven fabric manufacturing method, which replaces traditional kraft paper, achieves low-cost, high-performance, environmentally sustainable spunbond nonwoven fabric production through innovative raw material formulations, optimized process parameters, and recycling system design. The beneficial effects are as follows:

[0172] 1. Significantly reduce costs and resource consumption

[0173] 1. Closed-loop utilization of raw materials

[0174] By recycling waste spunbond non-woven fabric fragments (accounting for 10-30%) and production scraps (recycling ratio 5-15%), the amount of new polypropylene material used can be reduced and the raw material cost can be reduced by 30%-50%.

[0175] Starch-based degraders and polylactic acid (PLA) are introduced into the biodegradable masterbatch, and low-cost natural polymers are used to replace part of the petroleum-based raw materials, further reducing the formulation cost.

[0176] 2. Process energy consumption optimization

[0177] The barrier screw (length-to-diameter ratio 30-35:1) and segmented heating process improve melting efficiency and reduce energy consumption by 15%-20% compared to traditional screws.

[0178] Infrared preheating of the fiber web (80-100°C) reduces hot rolling energy consumption, and laser trimming technology (instead of mechanical trimming) reduces the burr loss rate to ≤1%.

[0179] 2. High performance alternative to traditional kraft paper

[0180] 1. Comprehensive mechanical properties surpass

[0181] Tensile strength: longitudinal ≥80N / 5cm, transverse ≥60N / 5cm, 14%-33% higher than traditional kraft paper (about 60-70N / 5cm), meeting heavy-load packaging needs.

[0182] The folding endurance is ≥5000 times, far exceeding kraft paper (2000-3000 times) and ordinary non-woven fabrics (3000-4000 times), and is suitable for multiple folding scenarios (such as express envelopes and seedling bags).

[0183] The tearing strength is ≥30N in the longitudinal direction and ≥25N in the transverse direction, with strong puncture resistance, reducing the breakage rate during transportation.

[0184] 2. Expanded application of functional post-processing

[0185] The water-repellent treatment makes the surface contact angle ≥110°, and the waterproof performance is better than kraft paper (contact angle of about 90°), and it can be used for packaging in humid environments (such as fertilizers and agricultural products).

[0186] Antistatic treatment makes the surface resistivity ≤1×10 9 Ω·cm, meeting the electrostatic protection requirements of electronic device packaging and filling the functional gap of kraft paper.

[0187] 3. Environmental sustainability and recycling

[0188] 1. Degradable and low pollution

[0189] The PLA and starch-based degradation agents in the degradable masterbatch control the degradation cycle of non-woven fabrics in natural soil to 12-24 months, avoiding the environmental problems of traditional PP non-woven fabrics (non-degradable) and kraft paper (degradation produces microfibers).

[0190] The surface of the recycled fragments is modified with silane (increasing the hydroxyl content by 20-30%) and a maleic anhydride grafted compatibilizer is used to eliminate interface defects of the recycled material and reduce the waste rate during the production process.

[0191] 2. Efficient recycling system

[0192] Waste non-woven fabrics can be recycled at least three times through "crushing-melting-spinning". After the cycle, the longitudinal strength retention rate is ≥85% and the transverse strength is ≥80%, building a "production-use-recycling" closed loop and breaking the limitation of traditional kraft paper's one-time use.

[0193] 100% recycling of scrap materials, combined with metal detection and moisture content control (≤0.1%), ensures the quality stability of recycled materials and achieves zero waste of resources.

[0194] 4. Process stability and quality controllability

[0195] 1. Precise process parameter design

[0196] Diamond pattern hot rolling roller (depth 0.1-0.3mm, density 20-30 pieces / cm 2 ) Improve the uniformity of fiber web bonding, with the mass deviation per unit area ≤±3%, which is better than the ±5% deviation of kraft paper.

[0197] The hexagonal array distribution of spinneret holes (15-20 holes / cm) and high-speed drawing (15-25m / s) control the diameter of the monofilament to 1.5-3μm, resulting in a dense fiber web structure and a smooth and flawless surface.

[0198] 2. Adaptability to large-scale production

[0199] The parameter range of screw speed 150-200r / min and melt pressure 8-12MPa is compatible with existing spunbond equipment, eliminating the need for large-scale equipment modification and lowering the threshold for industrialization.

[0200] V. Industrial Value and Social Benefits

[0201] Replace traditional kraft paper: "Replace paper with plastic" in industrial packaging bags (load-bearing ≥ 15kg), agricultural seedling bags (degradation cycle controllable), express envelopes and other fields to alleviate the shortage of wood resources.

[0202] Compared with kraft paper production (energy consumption per ton of paper is about 3.5 tons of standard coal), this process reduces energy consumption by more than 40% and significantly reduces carbon emissions, which is in line with the global green manufacturing trend.

[0203] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for producing a low-cost, recyclable spunbond nonwoven fabric that can replace traditional kraft paper, characterized in that: The specific steps include: S1. Raw material preparation: 60-80% polypropylene particles, 10-20% biodegradable masterbatch, and 10-30% recycled spunbond non-woven fabric fragments are mixed uniformly by weight, and the surface of the recycled spunbond non-woven fabric fragments is treated with a silane coupling agent solution with a concentration of 0.5-1.5% and a treatment time of 5-15 minutes; S2. Melt extrusion: The mixed raw materials are fed into a screw extruder, melted and plasticized at 180-220°C, and transported to the spinning assembly via a metering pump. The screw extruder adopts a barrier screw with an aspect ratio of 30-35:1 and a screw speed of 150-200 r / min; S3, spinning into web: The polypropylene melt is extruded through a spinning die to form a thin stream, which is drawn into monofilaments by a high-speed airflow of 15-25 m / s. The drawing airflow temperature is 60-80°C, and the monofilament diameter is controlled at 1.5-3 μm. The monofilaments are then evenly spread to form a fiber web; S4. Hot pressing and shaping: The fiber web is transported to the hot rolling mill. The surface of the hot rolling mill roll is provided with diamond patterns with a pattern depth of 0.1-0.3mm and a pattern density of 20-30 pieces / cm 2 , hot rolling bonding is carried out at 110-150℃ and pressure 0.3-0.8MPa, and the fiber web is infrared preheated before hot rolling at a preheating temperature of 80-100℃; S5. Cooling and trimming: The hot-rolled non-woven fabric is cooled by air, and the cooling rate is controlled at 5-10°C / s. The edge burrs are then removed by a laser trimming device. The collected edge materials are crushed into a particle size of 0.5-2mm by a low-temperature grinder and set aside. S6. Post-treatment: The cooled non-woven fabric is subjected to water repellent treatment and antistatic treatment in sequence. The water repellent treatment makes the surface contact angle of the non-woven fabric ≥110°, and the antistatic treatment makes the surface resistivity ≤1×10 9 Ω·cm; S7, Rolling and forming: The treated non-woven fabric is rolled into a finished product with a weight of 80-120g / m 2 , longitudinal tensile strength ≥80N / 5cm, transverse tensile strength ≥60N, tear strength longitudinal ≥30N, transverse ≥25N.

2. The method for producing a low-cost, recyclable spunbond nonwoven fabric that replaces traditional kraft paper according to claim 1, characterized in that: The degradable masterbatch in step S1 is composed of the following components by weight: 20-30% of polylactic acid PLA, 10-20% of starch-based degradation agent, 5-10% of maleic anhydride grafted polypropylene compatibilizer, 0.5-1% of hindered phenol antioxidant, and the balance is polypropylene carrier.

3. The method for producing a low-cost, recyclable spunbond nonwoven fabric that replaces traditional kraft paper according to claim 2, characterized in that: The preparation method of the recycled spunbond non-woven fabric fragments described in step S1 includes: crushing and screening the waste spunbond non-woven fabric, immersing it in a sodium hydroxide solution with a mass concentration of 1-3%, treating it at 50-70°C for 10-20 minutes to remove surface impurities, washing it with clean water and drying it, and then immersing it in a γ-aminopropyltriethoxysilane solution for surface modification, whereby the surface hydroxyl content of the fragments is increased by 20-30% after modification.

4. The method for producing a low-cost, recyclable spunbond nonwoven fabric that replaces traditional kraft paper according to claim 3, characterized in that: In step S2, the melt pressure of the screw extruder is controlled at 8-12 MPa, and the barrel is heated in three sections, with the temperature of the first section at 180-190°C, the temperature of the second section at 190-210°C, and the temperature of the third section at 210-220°C.

5. The method for producing a low-cost, recyclable spunbond nonwoven fabric that replaces traditional kraft paper according to claim 4, characterized in that: In step S3, the diameter of the spinneret holes of the spinning die head is 0.2-0.4 mm, the spinneret holes are distributed in a hexagonal array, the arrangement density is 15-20 holes / cm, and the aspect ratio of the spinneret holes is 8-12:

1.

6. The method for producing a low-cost, recyclable spunbond nonwoven fabric that replaces traditional kraft paper according to claim 5, characterized in that: The scrap collected in step S5 is recycled to step S1 at a ratio of 5-15% of the total weight of the new raw materials. When recycled, the scrap and the new raw materials are mixed for ≥10 min and at a mixing speed ≥300 r / min.

7. The method for producing a low-cost, recyclable spunbond nonwoven fabric that replaces traditional kraft paper according to claim 6, characterized in that: The antistatic treatment in step S6 is as follows: the non-woven fabric is immersed in an aqueous solution containing 0.3-0.8% of a quaternary ammonium salt antistatic agent by a padding process, with the padding rate controlled at 60-80%, and then dried at 90-110° C. for 10-15 minutes.

8. The method for producing a low-cost, recyclable spunbond nonwoven fabric that replaces traditional kraft paper according to claim 7, characterized in that: The finished non-woven fabric produced thereby has a folding endurance of ≥5000 times, a mass deviation per unit area of ≤±3%, and is recycled at least 3 times through a crushing-melting-spinning process. After recycling, the longitudinal tensile strength retention rate is ≥85%, and the transverse tensile strength retention rate is ≥80%.

9. The method for producing a low-cost, recyclable spunbond nonwoven fabric that replaces traditional kraft paper according to claim 8, characterized in that: The waste finished non-woven fabric is crushed to a particle size of ≤2mm, and then impurities are removed through a metal detector. Then, the waste finished non-woven fabric is mixed with polypropylene particles and degradable masterbatch at a ratio of 10-30% of the total weight of the new raw materials, and the moisture content of the mixed raw materials is controlled to be ≤0.1%.

10. The method for producing a low-cost, recyclable spunbond nonwoven fabric that replaces traditional kraft paper according to claim 8, characterized in that: The finished non-woven fabric is used to replace traditional kraft paper to prepare industrial packaging bags, agricultural seedling bags or express envelopes. The packaging bags have a load-bearing capacity of ≥15 kg, and the degradation period of the seedling bags in natural soil is ≥12 months and ≤24 months.

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