Melt pumps and screen changers for PUR adhesive extrusion production lines
Within PUR adhesive extrusion production lines, melt pumps and dual-column screen changers form a core “filtration-conveyance-regulation” technology chain through precise delivery, pressure stabilization, impurity filtration, and continuous production assurance. This significantly enhances production efficiency, product quality, and process stability.
I. Melt Pumps: Core Components for PUR Adhesive Conveyance and Pressure Control
Precision Conveyance and Pressure Stability
As a positive displacement pump, the melt pump employs gear meshing to quantitatively convey high-viscosity PUR adhesive from reactors or storage tanks to filling heads with ±0.5% precision. Its volumetric design eliminates pressure fluctuations inherent in traditional screw pumps, preventing pre-polymerization reactions caused by shear-induced overheating and ensuring consistent curing performance. For instance, within a 50-500 kg/h capacity range, the melt pump adjusts speed (0-100 rpm stepless variation) via real-time pressure sensor feedback to accommodate adhesives of varying viscosities (500-20,000 cPs). Its synchronized metering system maintains a mixing ratio error of ≤1% between the main pump and curing agent pump.
Corrosion Resistance and Self-Lubrication Design
Gear sets utilize nitrided steel or tool steel with carburized hardened surfaces (hardness HRC60+), resisting corrosion from isocyanate components in PUR adhesives. Segmented heating design in pump bodies, coupled with PID temperature control systems, maintains optimal processing temperatures of 80-120°C for adhesives. Combination mechanical seals and inert gas protection prevent moisture ingress that could cause gelation.
II. Dual-Column Screen Changer: Impurity Filtration and Continuous Production Assurance
Non-Stop Screen Changing Technology
The dual-column screen changer employs a dual-channel filtration design. While one set of screens operates, the other can be cleaned or replaced. Controlled by a hydraulic or pneumatic system, the switching process takes only seconds, ensuring zero disruption to production continuity. For instance, when the working filter becomes clogged and the pressure differential exceeds 0.3MPa, the system automatically switches to the standby filter column. The replaced filter can be cleaned during production, reducing downtime by approximately 30% and boosting production efficiency by 15-20%.
High-Efficiency Filtration and Degassing System
The dual-channel design expands filtration area to meet high-output demands. The degassing system thoroughly removes gases from the material, preventing gas ingress into the product during screen changes and enhancing product quality. Screen mesh size is matched to adhesive viscosity and impurity content (typically 80-120 mesh). Premium 316L stainless steel ensures corrosion resistance, while O-rings and sealing systems withstand high temperatures and pressures to prevent leakage.
III. Technical Synergy and Process Optimization
“Filtration-Conveyance-Control” Chain
The melt pump precisely controls flow and pressure, eliminating feeding fluctuations and optimizing melt homogenization to enhance adhesive performance. The dual-column screen changer intercepts impurities to guarantee purity, enabling non-stop screen changes via dual-column, dual-station operation to maintain continuous production. Together, they form a closed-loop control system. For instance, pressure closed-loop control synergizes with the synchronous metering system to ensure mixing ratio error ≤1%, meeting high-precision production requirements.
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