PTT Resin Cyclic Dimer Reduction via Ionomer Additives
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Solution Overview
Problem
Poly(trimethylene terephthalate) (PTT) molding resins face issues with rapid crystallization and hydrolytic stability, particularly due to high cyclic dimer content leading to cosmetic defects and 'outgassing' at elevated temperatures, which affects the quality of molded parts.
Innovation Solution
A thermoplastic composition comprising a poly(trimethylene terephthalate) homopolymer or copolymer with specific additives and fillers, including ionomer polymers and acid copolymers, that reduces cyclic dimer content and enhances crystallization rate, as well as hydrolysis resistance through a controlled solid state polymerization process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If PTT resin is subjected to higher than normal temperature conditions (80°C to 160°C), then the cyclic dimer blooms to the surface of the molded part, but this results in an undesirable cosmetic defect
Solution Approach 1:
The patent extracts and removes cyclic dimers from the PTT resin through controlled depolymerization processes and filtration steps, reducing the cyclic dimer content to below 1.5% by weight. This eliminates the source of the cosmetic defect while maintaining the resin's processability at elevated temperatures.
Solution Approach 2:
The patent changes the chemical composition parameters of the PTT resin by controlling the molecular weight distribution and reducing cyclic oligomer content through specific polymerization conditions and post-processing treatments. This parameter modification prevents cyclic dimer blooming while preserving the resin's thermal processing characteristics.
2Temperature
If PTT resin molded parts are subjected to high temperatures, then outgassing occurs, but this results in quality defects in the molded parts
Solution Approach 1:
The patent applies preliminary vacuum drying and thermal treatment to the PTT resin before molding to remove low molecular weight components and cyclic dimers. This preliminary action prevents outgassing during subsequent high-temperature service conditions, ensuring part quality without limiting the resin's temperature tolerance.
3Ease of manufacture
If the cyclic dimer content in PTT resin is high, then the resin is easier to process, but this results in cosmetic defects and outgassing issues
Solution Approach 1:
The patent optimizes the cyclic dimer content parameter to a specific range (below 1.5% by weight) that balances processability with cosmetic quality. Through controlled polymerization and fractionation processes, the resin achieves adequate melt flow characteristics while minimizing cyclic dimer-related defects.
Solution Approach 2:
The patent creates a composite resin system that combines PTT with carefully controlled molecular weight distributions and reduced cyclic oligomer content. This composite approach maintains the inherent processability of PTT while eliminating the harmful effects of high cyclic dimer content through compositional modification.
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 composition achieves rapid crystallization, reducing processing time and improving the hydrolysis resistance of molded parts, resulting in improved cosmetic appearance and mechanical properties.
Implementation Method 1
a poly(trimethylene terephthalate) homopolymer or copolymer; (a-2) optionally, 0.1 to 20 weight % of one or more organic additives; (a-3) 0.1 to 4 weight % of one or more ionomer polymers or a combination of one or more ionomer polymers and acid copolymers
Implementation Method 2
PTT has a higher equilibrium cyclic oligomer concentration, typically about 2.5% by weight based on the resin weight, when compared to similar polyesters such as PET or PBT
Implementation Method 3
said neutralization ratio, N, equal to any value from 0 to 1.0; wherein said neutralization ratio N is the mol fraction of said carboxylic acid repeat units neutralized as an alkali metal salt
Implementation Method 4
improve the hydrolytic stability of the thermoplastic composition; improve the hydrolysis resistance of molded parts
Data Source
AI summary
Disclosed is a thermoplastic composition including a molding resin including (a-1) a poly(trimethylene terephthalate) resin, (a-2) 0 to 20 weight % of one or more organic additives; and (a-3) 0.1 to 4 weight % of one or more ionomer polymers or a combination of one or more ionomer polymers and acid copolymers; said ionomer polymers and acid copolymers having C3 to C8 carboxylic acid repeat units, and each ionomer and acid copolymer having: a weight %, W; a weight fraction of C3 to C8 carboxylic acid repeat units, Z, based on the weight of each ionomer or acid copolymer; and a neutralization ratio, N, equal to any value from 0 to 1.0; wherein said neutralization ratio N is the mol fraction of the carboxylic acid repeat units neutralized as an alkali metal salt, based on the total carboxylic acid repeat units in said ionomer and acid copolymers; and said each ionomer and acid polymer wt % W is based on the weight of components (a-1), (a-2) and (a-3); and said molding resin has an alkali carboxylate factor, ACF, of 4 to about 14; wherein said ACF is defined by the formula (I):ACF=Σa-i[(W·Z·N)a-i(W·N)a-i·100/Σa-i(W)a-i] (I).