Causes and countermeasures of the impact of CP spinning online color filament addition on production environment
In the chemical fiber textile field such as polyester filament, the melt direct spinning online color masterbatch addition technology for colored yarn production is increasingly chosen by major polyester manufacturers due to its ability to leverage the unique characteristics of older production lines and enhance their added value. This technology achieves uniform online coloring of the melt by precisely injecting color masterbatch into the melt delivery pipeline, directly spinning various colored yarns, thereby eliminating the complex processes involved in traditional chip dyeing. However, in actual large-scale production, the online addition process for colored yarn spinning can have multidimensional negative impacts on the production environment and concurrently produced normal white yarn products. If not properly controlled, it can easily lead to color differences, defects, downgrades in white yarn, or even trigger quality incidents across the entire production line. Today, we will focus on discussing the root causes of this process's impact on the production environment and normal white yarn, and propose targeted prevention and control measures.
一、Reasons for the impact of online addition of colored spinning filaments via melt direct spinning on the production environment and normal white filaments
（1）Color masterbatch dust and melt debris pollute the production environment
When adding color masterbatch online, the processes of material unpacking, metering, and conveying generate colored dust and fine melt fragments, which disperse into the workshop production environment. On one hand, the air conditioning supply and equipment operation airflow in the production workshop carry these colored pollutants, causing them to spread and adhere to key production areas such as the spinning box, components, duct, and winding equipment, forming long-term pollution sources. On the other hand, partially unmelted agglomerated pigment particles and degraded melt fragments float with the production airflow and fall into the melt pipelines or the inlet of spinning components in the white filament production area, directly interfering with the white filament production process.
（2）Residual melt in the pipeline causes color contamination
Melt direct spinning production lines are mostly single-line multi-station setups with frequent product switching. After online addition of colored filaments, colored melt easily remains in the melt transport pipelines, static mixers, and metering pump chambers. Even with pipeline cleaning, if not thorough, residual colored melt and colorants can mix with the subsequent virgin melt for white filament production, causing hidden color contamination in white filaments. Particularly when switching from light-colored filaments to white filaments or after high-concentration masterbatch addition, pipeline residue increases, raising the risk of color contamination. This directly leads to quality defects in white filaments such as color spots, colored streaks, and uneven coloration.
（3）Equipment cross-contamination causes fluctuations in white filament quality
Core equipment such as spinning assemblies, spinnerets, and melt filters are prone to residual cross-contamination of colorants during the switch between colored and white filament production, as well as during equipment disassembly and cleaning. If components used in colored filament production are not thoroughly cleaned, residual colored melt and colorants may degrade under high temperature and pressure. When these components are reused in white filament production, the degraded residues can be extruded with the melt, forming colored defects. Additionally, if operational tools, cleaning equipment, and transport devices in the workshop are not used in designated areas, they can directly introduce colored contaminants into white filament production stations, leading to appearance defects and abnormal dyeing in white filaments.
（4）Fluctuations in production process parameters exacerbate pollution dispersion
When adding masterbatch online, process parameters such as melt temperature, pressure, conveying speed, and colorant addition ratio differ from those in white filament production. Improper parameter control can lead to issues such as melt backflow, colorant overflow, and degraded melt precipitation: fluctuations in melt pressure may cause leakage of colored melt at pipeline joints or metering pump seals, dripping onto white filament spinning positions; excessively high temperatures can cause degradation and volatilization of colorants, generating colored fumes that adhere to the chimney and cooling air system, contaminating the white filament formation process with cooling air and resulting in oil-stained or discolored filaments in white filaments.
（5）Cross-contamination between cooling air and exhaust gas recirculation system
The cooling air system in the spinning workshop operates in a full-circulation mode. During colored yarn production, colored volatiles and fine fiber dust generated can mix into the cooling air circulation system. Without partitioned control, cooling air containing pollutants will be directly delivered to the white yarn production area, adhering to the surface of the yarn bundles during the cooling and forming stage. This not only affects the appearance and cleanliness of the white yarn but also leads to non-compliance in subsequent weaving and dyeing performance. Additionally, incomplete treatment of production exhaust gases can cause secondary deposition of pollutants within the workshop, increasing the risk of white yarn contamination.
二、Production Environment Optimization for Melt-Direct Spinning Online Dope-Dyed Yarn and Countermeasures for White Yarn Protection
（1）Implement zonal isolation production to block pollution transmission pathways
1、Physical Partition Control: Physically isolate the production stations for colored yarns from those for white yarns. Use transparent dust-proof partitions and independent enclosures to delineate dedicated production zones. Establish separate access channels for personnel and materials, strictly prohibit unauthorized cross-regional movement, and achieve complete spatial separation of colored and white yarn production areas.
2、 Independent airflow control: Install separate cooling air systems and exhaust collection devices for the colored yarn production area to prevent mixing with cooling air from the white yarn area; the white yarn production area uses positive pressure ventilation to prevent backflow of contaminated air from the colored yarn area, blocking cross-contamination of dust and volatile substances at the source.
（2）Strengthen the cleaning of melt pipelines and equipment to eliminate residual contamination
1、Fine pipeline cleaning: Before switching from colored filament production to white filament production, use special cleaning materials and high-temperature cleaning processes to thoroughly clean the melt pipeline, mixer, and metering pump. Monitor the color of the discharged melt throughout the process until the discharge is completely transparent and free of any discoloration; regularly perform deep disassembly and cleaning of the pipeline to remove degraded residual colorants adhering to the inner walls.
2、Dedicated equipment management: Specialized spinning components, spinnerets, and filters are used for the production of colored and white filaments, with clear identification to prevent cross-use. Component disassembly and cleaning are performed using dedicated tools in an independent cleaning area. After passing high-temperature calcination, ultrasonic cleaning, and pressure testing, the components can be used for white filament production.
（3）Standardize material and site management to control dust pollution sources
1、Closed treatment of colorants: The entire process of color masterbatch unpacking, metering, and conveying adopts closed automated equipment to reduce manual operation links. Material feeding is completed within a negative pressure dust removal device to avoid the dispersion of colored dust. Materials are stored in sealed containers and placed in designated areas exclusive to colored filaments to prevent dust diffusion.
2、 Fine-grained workshop cleaning: Implement a graded cleaning system, prioritizing the colored fiber area. Use dust-free wiping and negative pressure vacuuming methods to promptly remove colored dust and polymer residue from equipment surfaces, floors, and air ducts. Operators must strictly follow zoning dress codes and segregated tool placement to eliminate cross-contamination risks.
（四）Precisely regulate process parameters and stabilize production conditions
1、Unify basic process standards: During colored filament production, keep basic parameters such as melt temperature, pressure, and conveying speed consistent with white filament production parameters as much as possible to reduce melt leakage and colorant overflow caused by parameter fluctuations; optimize the colorant addition method by adopting a precise metering injection system to avoid the formation of agglomerated particles.
2、Real-time monitoring of pollution risks: Install dust and volatile substance monitoring equipment in the white silk production area to monitor production environment indicators in real-time; monitor the appearance and color of white silk filaments online. Once abnormalities are detected, immediately investigate pollution sources in the colored silk area and take timely action.
（五）Improve waste gas and waste material treatment, optimize the overall production environment
1、Classified treatment of exhaust gas: The exhaust gas from colored yarn production is collected separately, then purified, deodorized, and dedusted before discharge to prevent volatile compounds from causing cyclic pollution; regularly clean the cooling air filter and exhaust gas treatment devices to ensure filtration efficiency and avoid the accumulation of pollutants.
2、Timely disposal of production waste: Waste filaments, scraps, and cleaning residues generated during colored filament production must be sealed and stored, and promptly removed from the workshop. It is strictly prohibited to pile them in the white filament area to prevent secondary pollution caused by waste degradation.
三、Conclusion
The production environment control of the melt direct spinning online color filament addition process focuses on preventing cross-contamination of normal white filaments by colored pollutants. Production enterprises must establish a refined prevention and control system across the entire process, including spatial zoning, equipment management, process regulation, and on-site cleaning. This approach aims to leverage the process advantages of color filament production while minimizing its negative impact on the production environment and white filament products. The goal is to achieve stable simultaneous production of colored and white filaments, improve overall product qualification rates and production economic efficiency, and promote the green and high-quality development of chemical fiber spinning production.
