Polyester Elastomer Composition for Stable Hollow Extrusion
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Solution Overview
Problem
Conventional thermoplastic polyester elastomers face challenges in achieving stable extrusion moldability and extrusion molding stability, particularly due to increased viscosity during processing, which complicates the production of hollow and long molded articles like cables and hoses with uniform thickness, while also lacking comprehensive heat, weather, and water resistance.
Innovation Solution
A thermoplastic polyester elastomer is developed with a hard segment made from aromatic dicarboxylic acid and aliphatic or alicyclic diol, and a soft segment primarily composed of aliphatic polycarbonate, which is end-capped with a reactive compound like polycarbodiimide to control melt viscosity and residence stability within specific ranges, ensuring improved extrusion moldability and resistance to heat, weather, and water.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an aliphatic carbonate is used as a soft segment to improve heat resistance and water resistance, then heat aging resistance and water resistance are improved, but the viscosity increases at the time of extrusion molding making it extremely difficult to control the melt viscosity
Solution Approach 1:
The patent applies parameter changes by precisely controlling the acid value within a specific range (10-30 eq/ton) and controlling the melt viscosity at low shear rate to be within a specific range (500-2000 Pa·s). These parameter optimizations resolve the contradiction by adjusting the chemical and rheological properties of the elastomer to achieve both heat aging resistance and extrusion moldability.
Solution Approach 2:
The patent uses a composite material approach by combining a hard segment (crystalline polyester) with a soft segment (aliphatic polycarbonate) in a segmented structure. This composite segmentation allows the material to exhibit both the heat resistance of the hard segment and the flexibility of the soft segment, while the controlled acid value ensures proper processing characteristics.
2Reliability
If an aliphatic carbonate is used as a soft segment to improve heat resistance, then heat aging resistance is improved, but the viscosity increases making it extremely difficult to stably produce hollow and long molded articles with uniform thickness
Solution Approach 1:
The patent resolves this contradiction by changing the rheological parameters of the material. By controlling the melt viscosity at low shear rate to be within 500-2000 Pa·s and controlling the acid value to 10-30 eq/ton, the material achieves stable flow characteristics during extrusion molding, enabling uniform thickness production while maintaining heat aging resistance.
Data Source
AI summary
The present invention aims to provide a thermoplastic polyester elastomer having particularly excellent extrusion moldability and extrusion molding stability, from which a hollow and long molded article can be stably produced with a uniform thickness for a long time. A polyester elastomer comprising a hard segment made of a polyester constituted of an aromatic dicarboxylic acid and an aliphatic or alicyclic diol and a soft segment made of an aliphatic polycarbonate, wherein the hard segment and the soft segment are bonded to each other, wherein the polyester elastomer is at least partially end-capped with a reactive compound, wherein the reactive compound comprises a polycarbodiimide, wherein the polyester elastomer has an acid value of 15 eq/ton or less, and wherein, under a condition of 230° C., the polyester elastomer satisfies (i) the melt viscosity at a shear rate of 10/sec after a preheating time of 5 minutes is 1,800 Pa·s or more, and the melt viscosity at a shear rate of 1,000/sec after a preheating time of 5 minutes is 800 Pa·s or less; and (ii) a ratio of the melt viscosity measured at a shear rate of 10/sec after a preheating time of 5 minutes to the melt viscosity measured at a shear rate of 10/sec after a preheating time of 25 minutes is 0.7 to 1.3.