Flexible Tube for Roller Pumps Using Single-Layer Elastomer
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Solution Overview
Problem
Existing flexible tubes for roller pumps face issues such as leaching of substances, reduced durability due to interlayer peeling, and potential health hazards from plasticizers like DEHP, especially when used with oily fluids in medical, food, and pharmaceutical applications.
Innovation Solution
A flexible tube formed by molding a thermoplastic resin composition into a tubular shape, which exhibits specific physical properties including high strain tolerance up to 300% without fracture, minimal leaching of plasticizers, and resistance to deformation and cracking under repeated crushing and restoration in roller pumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a multilayer structure is used to satisfy mechanical properties, then flexibility and mechanical strength are improved, but interlayer peeling occurs reducing service life
Solution Approach 1:
The patent extracts the harmful multilayer structure and replaces it with a single-layer thermoplastic elastomer composition. This eliminates the interlayer peeling problem while maintaining the required mechanical properties through careful selection of polymer blends and plasticizers.
Solution Approach 2:
The patent uses a composite material approach by blending multiple polymers (polyolefin, polyester elastomer, polyurethane) and plasticizers in specific ratios to achieve the desired mechanical properties in a single-layer structure, avoiding the problems of multilayer construction.
2Ease of manufacture
If polyvinyl chloride with low molecular weight plasticizers is used, then ease of processing is improved, but leaching of harmful substances occurs
Solution Approach 1:
The patent changes the molecular weight parameter of the plasticizer from low (in conventional PVC) to high (3000-5000), which reduces leaching while maintaining processing ease. The plasticizer content is also optimized at 48-93 parts per 100 parts of halogen-containing thermoplastic resin.
Solution Approach 2:
The patent converts the potential harm of plasticizer leaching into a benefit by selecting high molecular weight plasticizers that provide the necessary flexibility and processability while having minimal leaching tendency, thus eliminating the harmful effect while retaining the functional benefit.
3Productivity
If circular flexible tube is used, then internal resistance to fluid flow is minimized, but gaps remain at creased areas causing leaks
Solution Approach 1:
The patent applies local quality by creating non-uniform wall thickness distribution in the tube, with thicker walls at the inner circumference that contacts the roller and thinner walls at the outer circumference. This provides better sealing at the crease area while maintaining overall flow efficiency.
Data Source
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AI summary
This flexible tube is formed by molding a thermoplastic resin composition into a tubular shape, has favorable physical properties for a roller pump or the like, and has high durability. The resin composition does not exhibit fracture until the strain reaches 300% in the stress-strain curve; has a positive value that is obtained by first-order differentiation of an approximation formula for the stress-strain curve in a region up to the fracture point; and exhibits an evaporation residue of 150 µg/ml or less from a leaching solution obtained by immersing the resin composition in n-heptane as a solvent at 25°C for 1 hour. The resin composition is characterized by having a tensile stress of 4.5 to 8.0 MPa at a strain of 100% in the stress-strain curve and a tensile stress within a range from 11.0 to 19.0 MPa at a strain of 300%. The resin composition contains 48 to 93 parts by weight of an adipic acid-based polyester having a weight average molecular weight of 3,500 to 5,500 as a plasticizer with respect to 100 parts by weight of a thermoplastic resin, in particular a halogen-containing thermoplastic resin.