PVC Roller Pump Tube Composition for Stable Flow and Leak Resistance
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Solution Overview
Problem
Existing flexible tubes for roller pumps face issues such as leaks, decreased flow rates, and increased risk of rupture due to substance elution and physical property changes, particularly when used with oily fluids, and are unsuitable for long-term use in medical, food, and pharmaceutical applications.
Innovation Solution
A flexible tube composed of polyvinyl chloride with an average degree of polymerization of 1,500 to 2,500, containing 70 to 100 parts by weight of a polyester plasticizer with a molecular weight of 3,500 to 5,500, and optionally including additives like acrylic and methacrylic resin, ensuring a single-layer structure and minimal substance elution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a circular flexible tube is used for the roller pump, then the flexible tube has easy molding and small fluid resistance, but a gap remains near the fold when crushed, leaks easily occur, and the flexible tube is hardly set under vacuum
Solution Approach 1:
The patent applies asymmetry by changing the tube cross-section from a circular shape to an elliptical shape with a specific aspect ratio. This asymmetric geometry eliminates the gap formation that occurs at folds in circular tubes during crushing, thereby preventing leaks while maintaining manufacturing feasibility through extrusion molding.
2Manufacturing precision
If considerable great welding pressure is applied to eliminate the gap in a circular flexible tube, then the gap is eliminated, but weakening of the flexible tube occurs and the original circular cross-sectional shape is not restored with insufficient elasticity
Solution Approach 1:
The elliptical cross-sectional shape with a specific aspect ratio is designed to naturally conform to the crushing action of the roller pump without requiring high welding pressure. The asymmetric geometry allows the tube to be set under vacuum and maintain seal integrity without applying excessive force that would weaken the tube or prevent elastic recovery.
3Ease of operation
If a polyolefin material is used for the flexible tube, then the flexible tube has good flexibility, but substances other than plasticizer are eluted when oily fluid circulates, physical property changes occur, and flow rate decreases
Solution Approach 1:
The patent changes the material parameter from polyolefin to a specific copolymer composition with controlled plasticizer content and molecular weight. This parameter change ensures that only the plasticizer is eluted (within acceptable limits) while maintaining flexibility and preventing significant physical property changes that would affect flow rate stability during prolonged use with oily fluids.
4Loss of substance
If a chlorine-containing resin with low degree of polymerization is used for the flexible tube, then plasticizer elution is minimal, but the flexible tube is more likely to be extended and water leakage occurs when sandwiched between roller and inner wall surface
Solution Approach 1:
The patent optimizes the degree of polymerization parameter to a specific range (1,500 to 2,500) and controls plasticizer content (70 to 100 parts by weight per 100 parts polyvinyl chloride). This parameter optimization balances plasticizer retention with sufficient mechanical strength and rupture resistance, preventing water leakage when the tube is sandwiched between the roller and inner wall surface during pump operation.
Data Source
AI summary
This flexible tube is suitable for use in a roller pump or the like for fluid transport, does not decrease in flow rate even when used for a long time, and has little risk of leakage due to rupture. This flexible tube is formed by molding a resin composition composed of polyvinyl chloride having an average degree of polymerization of 1500-2500 into a tubular shape. The resin composition contains 70-100 parts by weight of a plasticizer relative to 100 parts by weight of polyvinyl chloride. The evaporation residue of a leaching solution obtained by immersing the resin composition at 25°C for 1 hour by using heptane as a solvent is 1000 µg/ml or less. The plasticizer has a weight-average molecular weight of 3500-5500. The flexible tube has a single-layer structure and can be used for the peristaltic section of a roller pump.