Polyamide moulding composition, in particular for the production of mouldings in the drinking water sector
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Solution Overview
Problem
Current semiaromatic polyamide moulding compositions fail to meet performance requirements for long-term failure tests under internal hydrostatic pressure at elevated temperatures and have high total organic carbon (TOC) values, making them unsuitable for high-temperature drinking water applications.
Innovation Solution
A polyamide moulding composition comprising 25-74.9% semicrystalline semiaromatic nylon-6,T/6,I with specific ratios of terephthalic acid, isophthalic acid, 1,6-diaminohexane, and a phosphorus compound, combined with 25-60% fibrous reinforcing materials and heat stabilizers, excluding copper-containing stabilizers, to achieve enhanced mechanical properties and low TOC values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If semicrystalline semiaromatic polyamides are used for high-temperature applications, then melting point and thermo-mechanical properties are improved, but long-term failure performance under internal hydrostatic pressure at elevated temperatures deteriorates
Solution Approach 1:
The patent uses a composite material system consisting of semicrystalline semiaromatic polyamide (PA 6T/6I) combined with specific additives including phosphorus compounds (0.01-0.5 wt%), nitrogen-containing compounds (0.01-0.5 wt%), and sulfur-containing compounds (0.01-0.5 wt%). This composite approach allows the base polymer to provide high melting point (270-330°C) while the additives modify the molecular structure to improve long-term hydrolytic stability and pressure resistance at elevated temperatures.
Solution Approach 2:
The patent modifies the chemical composition parameters of the polyamide by controlling the molar ratios of monomers (terephthalic acid, isophthalic acid, 1,6-diaminohexane) and adding specific chemical compounds. The phosphorus, nitrogen, and sulfur compounds change the molecular parameters by forming crosslinks or modifying terminal groups, which improves the material's resistance to hydrolysis and maintains mechanical properties under long-term hydrostatic pressure at temperatures up to 80°C.
2Strength
If semicrystalline semiaromatic polyamides are used to improve bursting pressure, then tensile strength is improved, but total organic carbon values increase making them unsuitable for drinking water applications
Solution Approach 1:
The patent converts the potential harm of high TOC values into a benefit by using phosphorus, nitrogen, and sulfur compounds that reduce extractable organic carbon. These additives modify the polymer structure to decrease hydrolysis products and extractable substances, thereby reducing TOC values to below 0.1 mg C/m²d even while maintaining high bursting pressure (above 100 bar at 23°C). This allows the material to meet both mechanical strength requirements and drinking water compatibility standards.
Solution Approach 2:
The patent changes the chemical composition parameters by incorporating specific ratios of terephthalic acid (65-82 mol%), isophthalic acid (18-35 mol%), and 1,6-diaminohexane, along with small amounts of phosphorus (0.01-0.5 wt%), nitrogen (0.01-0.5 wt%), and sulfur (0.01-0.5 wt%) compounds. This precise parameter control optimizes both the mechanical strength (bursting pressure) and the extractable carbon content, achieving a balance between performance and environmental compatibility for drinking water applications.
Data Source
AI summary
A polyamide moulding composition in particular for use for components in the drinking water sector, made of the following constituents:(A) from 25 to 74.9% by weight of at least one semicrystalline, semiaromatic nylon-6,T/6,I, composed of: (a1) from 65 to 82 mol % of terephthalic acid, based on the entirety of the dicarboxylic acids used; (a2) from 18 to 35 mol % of isophthalic acid, based on the entirety of the dicarboxylic acids used; (a3) 1,6-diaminohexane; (a4) at least one monobasic carboxylic acid; (a5) a phosphorus compound; with the first proviso that the molar ratio of the component (a3) to the entirety of the dicarboxylic acids used ((al)+(a2)) is at least 1.04 and at most 1.15; and with the second proviso that the molar ratio of the component (a4) to the component (a3) is in the range from 0.01 to 0.08;(B) from 25 to 60% by weight of fibrous reinforcing materials;(C) from 0 to 30% by weight of particulate fillers;(D) from 0.1 to 2.0% by weight of heat stabilizers, with the proviso that no copper-containing stabilizers are present therein;(E) from 0 to 2% by weight of carbon black;(F) from 0 to 4% by weight of auxiliaries and/or additives differing from C, D and E; where the entirety of the components (A)-(F) makes up 100% by weight.