In the recycled plastics commodity market, not all PET flakes are valued equally. The pricing hierarchy is strictly dictated by downstream application requirements. At the upper echelon of mechanical recycling sits the production of fiber grade rPET flakes. These materials are not destined for low-tier packaging strapping or thick injection molding; they are engineered for the chemical spinning of Polyester Staple Fiber (PSF) or continuous filament yarns.

Khi các nhà sản xuất dệt kéo nhựa polymer qua các lỗ kim spinneret vi mô (thường dưới 0,3 mm đường kính), độ dung sai về vật chất và hóa học hầu như bằng không. Bất kỳ sai lệch nào trong tính toàn vẹn của polymer sẽ dẫn đến đứt sợi, tắc nghẽn nhanh của bộ lọc chảy, và thời gian ngừng sản xuất đắt đỏ. Vì vậy, tiêu chuẩn chất lượng của mảnh rPET cấp sợi không mang tính chủ quan; nó được xác định bởi giới hạn đo lường chặt chẽ về các chất ô nhiễm cụ thể.

Ba chỉ số chất lượng bất di bất dịch

To classify as fiber grade rPET flakes, the output from a washing line must typically pass strict laboratory analysis focusing on three primary failure points:

1. The Thermal Threat: PVC Contamination (< 50 PPM) Polyvinyl Chloride (PVC) is the absolute enemy of polyester spinning. Because PVC and PET have similar melting points but vastly different thermal degradation profiles, any PVC present in the extruder will burn and release hydrochloric acid. This acid acts as a catalyst, aggressively degrading the PET molecular chain, turning the melt brown, and severely reducing its intrinsic viscosity (IV). Controlling PVC content in PET flakes requires rigorous upstream intervention. It cannot be washed away; it must be physically removed through manual sorting or optical separation before the material ever enters the heavy-duty PET crusher.

2. The Chemical Residue: pH Level (< 8) Heavy-duty cleaning requires aggressive saponification. High-capacity recycling lines utilize caustic soda (NaOH) in a hot wash PET line to dissolve organic oils and stubborn adhesives. However, if this highly alkaline solution remains on the plastic, it will cause chemical hydrolysis during downstream melting. To achieve fiber grade, the pH value of the final flake must be neutralized to below 8. This is mechanically achieved through aggressive scouring inside high-speed friction washers, followed by multi-stage deep-water rinsing tanks that dilute and isolate the chemical carryover.

3. The Physical Barrier: Moisture Content (< 1%) PET is a hygroscopic material, meaning it absorbs water. If the moisture content exceeds 1% (or even 0.5% for ultra-fine filaments), the water molecules will react with the PET polymer chains at extrusion temperatures (around 280°C). This thermal hydrolysis sharply drops the molecular weight, resulting in brittle fibers that break under tension.

Cấu hình cơ học cho kiểm soát độ ẩm

Việc đưa độ ẩm xuống từ quá trình rửa hoàn toàn ngâm xuống dưới 1% đòi hỏi cơ sở sấy chuyên dụng. Phơi tự nhiên ở môi trường là không thể trong môi trường công nghiệp.

Based on Shuliy Group’s engineering configurations, the initial stage utilizes a centrifugal dryer (operating with a 37kw motor for 3000kg/h capacities). The intense G-force generated by the rotor strips away up to 98% of the surface water. However, to guarantee the strict parameter required for fiber grade rPET flakes, the material must then be transported through a thermal drying pipeline. Injecting hot air (typically through a 15-to-20-meter pipe system) evaporates the remaining microscopic moisture trapped within the flake crevices.

Ultimately, producing fiber-grade material is not about having Máy giặt that clean plastic. It is about operating a synchronized chemical and mechanical system designed to strictly control PVC parts-per-million, neutralize pH, and eradicate moisture.