HYFabricsupply is a professional non-woven fabric manufacturer of high quality Polypropylene Non-woven Fabric, Polyester spunbonded non-woven fabric, Spunlaced non-woven fabric,and more.
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The production of polypropylene spunbond nonwovens is a systematic process involving raw material characteristics, equipment technology, and environmental control. Multiple key parameters directly affect the physical properties, appearance quality, and production stability of the products. The main influencing parameters are sorted out from the core production links as follows:
Melt Flow Rate (MFR) of Polypropylene Granules
It is a core indicator affecting spinning stability. Generally, granules with an MFR of 20-40g/10min (test condition: 230℃/2.16kg) are selected.
Too low MFR (<20): Poor melt fluidity, which is prone to wire breakage and uneven fiber thickness during spinning, leading to fluctuations in the strength of nonwovens;
Too high MFR (>40): Low melt viscosity, fibers are easy to be too thin and stick to the web, affecting the uniformity of web laying, and at the same time, the tensile strength of the product decreases.
Raw Material Purity and Impurity Content
The ash content in granules should be ≤0.05%, and the moisture content should be ≤0.05%. Excessive impurities or moisture will lead to "crystal points" (impurity aggregation) or bubbles during spinning, damage the continuity of fibers, and reduce the appearance quality and strength of products.
Screw Extrusion Temperature
It is controlled in multiple sections (feeding section, compression section, metering section), with an overall range usually 180-230℃, which needs to match the MFR of raw materials:
Low MFR granules need to increase the temperature (210-230℃) to ensure melt fluidity;
High MFR granules need to reduce the temperature (180-200℃) to avoid excessive degradation.
Excessive temperature fluctuations will lead to unstable melt viscosity, causing deviations in fiber linear density (more than ±5%).
Spinning Temperature and Spinneret Parameters
The temperature of the spinning box should be 5-10℃ higher than the outlet temperature of the screw (usually 220-240℃) to ensure uniform extrusion of the melt;
The number of spinneret holes (such as 1000-3000 holes/m) and hole diameter (0.2-0.4mm) determine the number of fibers and initial linear density: small hole diameter results in fine fibers (such as 1.5-3dtex) but is easy to block; large hole diameter results in coarse fibers (3-5dtex) and the product feels hard.
Melt Pressure
Controlled by a metering pump, it is usually stable at 10-20MPa. Pressure fluctuations will lead to uneven extrusion, resulting in uneven fiber thickness, and ultimately affecting the uniformity of nonwoven weight (required deviation ≤3%).
Drawing Air Speed and Air Pressure
They are core control parameters of the spunbond process. The melt filaments are stretched by high-speed air flow (usually 50-100m/s):
Too low air speed: Insufficient drawing, resulting in coarse fibers and low strength (breaking strength <20N/5cm);
Too high air speed: Excessive stretching of fibers is easy to break, or fiber entanglement (appearance of "cotton knots") due to air flow disturbance.
The air pressure needs to match the air speed (usually 0.2-0.5MPa) to ensure drawing stability.
Cooling Conditions
The temperature (15-25℃) and humidity (40%-60%) of the cooling air affect the fiber solidification speed: too low temperature will cause the melt to cool suddenly, resulting in low fiber crystallinity and decreased strength; too high humidity is easy to cause dew on the fiber surface, affecting the web laying effect.
Cooling air mode (side blowing/ring blowing): Side blowing is suitable for wide-width production, and the uniformity of air temperature (deviation ≤±2℃) needs to be controlled to avoid differences in fiber transverse performance.
Web Laying Speed and Uniformity
The web laying speed needs to match the spinning and drawing speed (usually 10-30m/min): too fast speed will lead to thin fiber web and low weight; too slow speed will lead to too thick fiber accumulation and insufficient consolidation.
The web laying uniformity is controlled by the "cross-laying" or "random-laying" process, requiring the longitudinal/transverse weight deviation ≤5%, otherwise it will lead to insufficient local strength of the product.
Hot Rolling Consolidation Parameters (for Hot-Rolled Spunbond)
Hot rolling temperature: Set according to the melting point of the fiber (usually 120-160℃). Homopolymer PP needs to be 10-20℃ higher than copolymer PP. Too low temperature will result in weak fiber bonding and low peel strength; too high temperature will lead to excessive fiber melting, making the product hard and reducing air permeability (air permeability reduction >20%).
Hot rolling pressure: Usually 5-20MPa. Insufficient pressure will lead to few bonding points and low strength; excessive pressure will compact the fiber web and reduce bulkiness.
Hot rolling roll speed: Synchronous with the production line speed. The speed difference will cause stretching deformation of the fiber web, resulting in wrinkles or dimensional deviation.
3.Hot Air Consolidation Parameters (for Hot Air Spunbond)
Hot air temperature (130-180℃) and air volume: Temperature determines fiber bonding strength, and air volume affects heat transfer efficiency. It is necessary to ensure that hot air penetrates the fiber web (penetration rate ≥90%), otherwise there will be local unconsolidated areas.
Weight (Quantitative)
It is a core indicator, usually 10-200g/m²: For low weight (<20g/m²), the drawing and web laying accuracy need to be controlled to avoid holes; for high weight (>100g/m²), the hot rolling pressure or hot air time needs to be increased to ensure sufficient consolidation.
Production Speed
It affects efficiency and stability, usually 50-200m/min: During high-speed production, the melt supply, drawing air speed, and consolidation energy need to be increased simultaneously, otherwise problems such as wire breakage and poor consolidation are easy to occur.
Post-Treatment Parameters
Hydrophilic treatment: The spray amount (1-5g/m²) and drying temperature (80-120℃) affect the hydrophilic effect, requiring the water absorption height ≥10mm within 30s (GB/T 24218.6 standard).
Antistatic treatment: The concentration of antistatic agent added (0.5%-2%) should be moderate. Too high concentration will cause the product to be sticky, and too low concentration will result in insufficient antistatic effect (surface resistance >10¹¹Ω).
The production workshop needs to control:
Ambient temperature (20-30℃): Avoid temperature fluctuations leading to changes in the melting state of raw materials;
Cleanliness (Class 10000 or above): Reduce dust pollution to the spinneret holes and reduce the wire breakage rate (required wire breakage times ≤1 time/hour);
Air pressure (slight positive pressure 5-10Pa): Prevent external pollutants from entering the spinning area.
The production parameters of polypropylene spunbond nonwovens need to form a "linked control": the raw material MFR determines the spinning temperature, the drawing air speed affects the fiber fineness, the consolidation parameters are related to the product strength, and the environmental and speed parameters ensure production stability. In actual production, it is necessary to optimize the combination through "parameter-performance" corresponding tests (such as adjusting the hot rolling temperature → testing the breaking strength) to meet the needs of different application scenarios (such as hygiene products requiring softness and high air permeability, geotextiles requiring high strength and tear resistance, and frost cloth requiring anti-aging properties).
