Dialysis Filter Housing Polyester for Chemical Resistance and Molding

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Solution Overview

Problem

Dialysis filter housings require materials with a combination of high impact strength, high glass transition temperature, chemical resistance, hydrolytic stability, and thermoformability, but existing polymers like polycarbonates and polyesters face challenges such as rapid crystallization, poor melt processability, and inadequate chemical resistance.

Innovation Solution

A dialysis filter housing made from a polyester composition comprising terephthalic acid, its esters, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and 1,4-cyclohexanedimethanol, with specific monomer ratios and inherent viscosities, which allows for improved processability and retention of physical properties like toughness and heat resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If PCT polyester is used to produce dialysis filter housings, then chemical resistance and hydrolytic stability are improved, but crystallization rate is too rapid allowing formation of amorphous articles by standard molding processes

Engineering Contradiction:

Improvechemical resistanceVSAvoidmold processability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent modifies the crystallization parameters of PCT by incorporating comonomers (ethylene glycol or isophthalic acid) at controlled levels (0.1-10 mole percent), which extends the crystallization half-time from seconds to minutes while maintaining the chemical resistance and hydrolytic stability of the base PCT polymer

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite polyester system combining PCT base polymer with controlled amounts of comonomers (ethylene glycol or isophthalic acid), achieving a material that exhibits both the desired chemical resistance of PCT and the extended processability required for amorphous molding applications

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If ethylene glycol or isophthalic acid is added to PCT to extend crystallization half-time, then ease of manufacture is improved, but glass transition temperature and impact strength deteriorate

Engineering Contradiction:

Improvecrystallization half-timeVSAvoidimpact strength

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent optimizes the concentration parameter of comonomers to a specific range (0.1-10 mole percent), which is sufficient to extend crystallization half-time to >10 seconds while minimizing the degradation of glass transition temperature and impact strength properties

Inventive Principle:

Principle #35Parameter changes

3Strength

If polycarbonate is used as an alternative material, then impact strength and heat resistance are improved, but melt viscosity is too high for good processability

Engineering Contradiction:

Improveimpact strengthVSAvoidmelt processability

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent modifies the molecular structure parameters of the polyester by incorporating cycloaliphatic glycols and controlling comonomer content, achieving a material with melt viscosity comparable to PCT (not polycarbonate) while maintaining amorphous formability and adequate impact strength

Inventive Principle:

Principle #35Parameter changes

4Ease of manufacture

If high comonomer content is used to extend crystallization half-time, then ease of manufacture is improved, but ductile-to-brittle transition temperature increases

Engineering Contradiction:

Improvecrystallization half-timeVSAvoidductile-to-brittle transition temperature

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The patent precisely controls the comonomer content parameter within 0.1-10 mole percent, which extends crystallization half-time adequately while keeping the ductile-to-brittle transition temperature below 0°C, ensuring the material remains ductile at processing and use temperatures

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7951900B2Dialysis filter housings comprising polyester compositions formed from 2,2,4,4-tetramethyl-1,3-cyclobutanediol and 1,4-cyclohexanedimethanol

Publication Date: 2011.05.31 EASTMAN CHEM CO

AI summary

Described are dialysis filter housings comprising polyester compositions comprising polyesters which comprise (a) a dicarboxylic acid component having terephthalic acid residues; optionally, aromatic dicarboxylic acid residues or aliphatic dicarboxylic acid residues or ester residues thereof; 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues; and 1,4-cyclohexanedimethanol residues.