Extrudable PET Blend Melt Strength and Recyclability

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Solution Overview

Problem

Current PET resins used in extrusion blow molding face challenges such as poor melt strength, leading to parason sagging and poor material distribution, and high molecular weight PET resins suffer from thermal degradation and increased costs, while branched PET copolymers affect recyclability due to amorphous nature.

Innovation Solution

A polyester blend comprising a slow crystallizing polyester copolymer base component and a crystallizable polyester component, with added chain extenders or branching agents, to enhance melt strength and crystallinity, facilitating recyclability and process stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If high molecular weight PET (I.V. ≥ 1.0 dl/g) is used to increase melt strength, then parason sagging is prevented, but processing temperature must be increased causing thermal degradation, yellowness, and higher costs

Engineering Contradiction:

Improvemelt strengthVSAvoidthermal degradation

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent changes the molecular architecture parameter from linear to branched structure, achieving high melt strength without requiring high processing temperatures. The branching structure provides entanglement and strength at lower temperatures, avoiding thermal degradation while maintaining parason stability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite molecular structure by incorporating branched copolymer chains into the PET matrix. This composite approach combines the strength benefits of high molecular weight PET with the processability advantages of lower temperature processing, as the branched structure provides melt strength through physical entanglement rather than requiring high temperature

Inventive Principle:

Principle #40Composite materials

2Ease of operation

If branched PET copolymers (e.g., EB062) are used to increase melt strength, then processing is improved, but crystallization is suppressed creating amorphous resin that causes sticking and agglomeration during recycling

Engineering Contradiction:

ImproveprocessabilityVSAvoidcrystallinity

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by creating a heterogeneous structure with both crystallizable and amorphous regions. The branched copolymer segments provide amorphous regions for processability while leaving sufficient linear PET segments to form crystallizable domains, achieving local optimization of both properties

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent carefully controls the branching parameter (level of copolymer incorporation) to maintain a balance between amorphous and crystalline regions. By limiting the copolymer content and controlling branch frequency, the resin maintains enough crystallinity to prevent sticking during recycling while retaining improved processability from the branched structure

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If bottle grade PET (I.V. 0.72-0.84 dl/g) is used for beverage bottles, then good processability is achieved, but melt strength is insufficient causing parason sagging and poor material distribution

Engineering Contradiction:

ImproveprocessabilityVSAvoidmelt strength

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The patent introduces curvature/branching into the linear polymer chains. The branched structure creates a more complex three-dimensional configuration that increases inter-chain entanglement and melt strength, while maintaining the processability characteristics of bottle-grade PET through controlled branching rather than high molecular weight

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 blend achieves sufficient melt strength for extrusion blow molding, reduces sticking and agglomeration, and allows for higher recyclability, enabling the production of containers with improved clarity and physical properties without the drawbacks of amorphous resins.

Implementation Method 1

the polyester blend should also have sufficient crystallinity to reduce sticking and agglomeration, which makes the polyester blend conducive to recycling

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Implementation Method 2

Methodology Applied

Scientific EffectPolymer chain extension and branching:

Data Source

PatentUS8080191B2Extrudable polyethylene terephthalate blend

Publication Date: 2011.12.20 PEPSICO INC

AI summary

A polymer blend has a base and blend components. The base and blend components could be a branched slow crystallizing PET and a faster crystallizing PET, respectively. The ratio of base and blend components result in a block copolymer, the melt processing time and branching or chain extender levels can be can be tailored to impart the polymer blend with sufficient melt strength and crystallization rates, such that it is slow enough during the blow molding process to produce a clear article and yet fast enough during the subsequent PET recycling process making it suitable for extrusion processes as well as for recycling. The combination of materials can be used to form monolayer or multilayer articles.