Polyamide Molding Composition with Amino End Groups for Hydrolysis Stability
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Solution Overview
Problem
Existing processes for producing polyamide moulding compositions used in pipes for transporting fluids suffer from reduced hydrolysis stability due to the introduction of carboxyl end groups from masterbatches, which also lead to undesirable increases in molecular weight and difficulties in precise metering.
Innovation Solution
A process involving a polyamide moulding composition with predominantly amino end groups, combined with a masterbatch containing a compound with at least two carbonate units and a polyetheramide, is used to produce mouldings with increased melt stiffness and minimized carboxyl end groups, ensuring hydrolysis stability by limiting the reaction of the additive during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a masterbatch containing a compound with carbonate units and polyamide with carboxyl end groups is used to increase molecular weight, then melt stiffness is improved, but hydrolysis stability deteriorates due to increased carboxyl end groups
Solution Approach 1:
The patent changes the chemical parameter of the polyamide by ensuring at least 50% of end groups are amino groups rather than carboxyl groups. This parameter change allows the condensation reaction to proceed while minimizing harmful carboxyl group formation, thus improving melt stiffness while maintaining hydrolysis stability.
Solution Approach 2:
The patent uses a composite system combining polyamide with specific end group composition and polyetheramide in the masterbatch. This composite approach allows the additive to function effectively for molecular weight increase while the controlled end group composition prevents excessive carboxyl group formation that would harm hydrolysis stability.
2Measurement precision
If polyamide with high amino end group content is used in the masterbatch, then precise metering is improved, but molecular weight increases undesirably during masterbatch production
Solution Approach 1:
The patent uses polyamide with at least 50% amino end groups, which is a partial action approach. This sufficient but not excessive amino group content allows precise metering and adequate reaction control without causing undesirable molecular weight increase that would occur with higher amino group content.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting moulding compositions exhibit improved hydrolysis stability and melt stiffness with precise metering of additives, suitable for large pipes and other applications, while maintaining material properties even when exposed to strongly extractive media.
Implementation Method 1
a compound having at least two carbonate units is used as additive to increase the molecular weight. The additive reacts with amino end groups of the polyamide to couple chains.
Implementation Method 2
the mixture is mixed as a melt with the introduction of shear
Data Source
AI summary
A polyamide molding composition is condensed up in the melt by means of a masterbatch containing a compound having at least two carbonate units and also a polyetheramide in which at least 50% of the end groups are present as amino end groups, whereupon the melt mixture is discharged and solidified to give a molding composition or a molding. The product obtained has an increased amino end group content and consequently an improved hydrolysis resistance.