The Entire Production Process of Polypropylene Spunbond Nonwoven Cold and Wind-Proof Plant Covers

1. Raw Material Selection: High-quality polypropylene (PP) chips serve as the foundation for production. PP chips with appropriate melt flow rate (MFR) are selected. Generally, PP chips with an MFR ranging from 20 to 40 g/10min are used for spunbond nonwoven production. PP chips within this range exhibit good fluidity during the melt extrusion process, ensuring the quality of fiber formation. Meanwhile, to enhance the anti-ultraviolet and anti-aging properties of the plant covers, an appropriate amount of anti-UV masterbatch is added to the raw materials. To give the products specific colors, color masterbatch is also incorporated. These additives need to be thoroughly mixed with the PP chips in precise proportions.

2. Drying Treatment: Polypropylene chips are prone to absorbing moisture. If the moisture content is too high, bubbles and fiber breakage may occur during the high-temperature melting process, affecting product quality. Therefore, the raw materials must be pretreated in a drying equipment. Typically, they are dried at a temperature of 80 - 100°C for 4 - 6 hours, reducing the moisture content of the chips to below 0.03% to ensure the smooth progress of subsequent production.

1. Melt Extrusion: The dried polypropylene chips are fed into a screw extruder. Driven by the screw, the chips are conveyed forward along the screw groove. Simultaneously, they are heated by the external heat of the barrel and the frictional heat generated by the screw, gradually melting as the temperature rises. When the temperature reaches 220 - 260°C, the PP chips are completely melted into a melt with good fluidity. The melt is accurately metered by a metering pump and then extruded through the spinneret holes of the spinneret, forming fine streams of melt filaments. The shape and arrangement of the spinneret holes on the spinneret determine the morphology and specifications of the fibers. Common spinneret hole shapes include circular and trilobal.

2. Cooling and Drawing: The melt filaments extruded from the spinneret are rapidly cooled and solidified in the air, and are further cooled and shaped by a side-blowing device. Subsequently, the filaments enter the drawing device. Under the action of high-speed airflow or mechanical drawing, the filaments are quickly stretched and thinned, causing the polypropylene molecular chains to orient and align along the axial direction of the fibers, improving the strength and crystallinity of the fibers. The draw ratio is generally controlled between 30 and 60 times to obtain an appropriate fiber linear density. Usually, the linear density of the produced spunbond fibers is between 1.5 - 3.0 decitex (dtex).

3. Web Laying: The drawn fibers are evenly laid on the forming curtain by the airflow to form a continuous fiber web. During the web formation process, parameters such as the fiber laying speed, airflow direction, and flow rate are controlled to adjust the weight per unit area (grammage) and uniformity of the fiber web. To ensure the cold and wind-proof effect of the plant covers, the grammage of the fiber web is generally controlled between 50 - 120 g/㎡, and the coefficient of variation of uniformity needs to be kept at a low level to ensure stable product performance.

1. Design and Layout: According to the sizes of different plants and usage scenarios, the shape and dimensions of the plant covers are designed using computer-aided design (CAD) software. Common shapes include circular, square, and cylindrical. To facilitate installation and use, structures such as zippers, openings, and ties are also designed. After the design is completed, the nonwoven fabric rolls are laid out, and the cutting plan is rationally planned to improve material utilization and reduce waste generation.

2. Cutting: The hot-rolled polypropylene spunbond nonwoven fabric is cut using cutting equipment. Commonly used cutting equipment includes automatic cutting beds, laser cutting machines, and ultrasonic cutting machines. Automatic cutting beds use blades for cutting, which is suitable for large-scale cutting of regular shapes and has a lower cost; laser cutting machines use laser beams to melt or vaporize the nonwoven fabric for cutting, featuring high cutting accuracy and neat edges, especially suitable for cutting complex shapes; ultrasonic cutting machines fuse the edges of the nonwoven fabric through high-frequency vibration, preventing the edges from fraying, and providing good cutting quality and high efficiency.

1. Edge Treatment: To prevent the edges of the plant covers from wearing and fraying, the cut edges need to be treated. Common edge treatment methods include hot melt edge sealing, edge binding, and edge folding. Hot melt edge sealing uses high temperature to melt and bond the edges of the nonwoven fabric, forming smooth sealed edges; edge binding wraps the edges with fabric strips to increase edge strength; edge folding folds the edges inward and sews them to make the edges neater.

2. Accessory Installation: According to the design requirements, accessories such as zippers, hook-and-loop fasteners, and ties are installed on the plant covers. Zippers facilitate the opening and closing of the plant covers; hook-and-loop fasteners and ties are used to fix the plant covers, enabling them to tightly wrap the plants and enhance the cold and wind-proof effect. During the installation process, it is necessary to ensure that the accessories are firmly attached, and the stitching is even and dense to avoid problems such as thread breakage and cracking.

3. Ventilation Hole Processing: To ensure the ventilation requirements of the plants inside the covers and prevent diseases caused by excessive humidity, ventilation holes are processed at appropriate positions on the plant covers. The ventilation holes can be made by stamping, laser drilling, or other methods. The size, quantity, and distribution of the holes are designed according to the types of plants and the usage environment.

1. Quality Inspection: Comprehensive quality inspections are carried out on the completed plant covers. Appearance inspection mainly checks for stains, damage, color differences, and other issues; physical property tests include tensile strength, tear strength, and burst strength tests to ensure that the plant covers can withstand a certain amount of external force; functional tests simulate the actual usage environment to test their cold and wind-proof performance and air permeability. Only products that meet all the standards can proceed to the next step.

2. Packaging and Warehousing: The qualified products are folded and packaged. Commonly used packaging materials include plastic bags and cartons. Information such as product names, specifications, usage instructions, and production dates is marked on the packaging for easy storage, transportation, and sales. The packaged plant covers are neatly stacked in the warehouse, waiting for delivery to customers.