Pressurized Mold Cavity Injection Molding PET Plate-Out

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Solution Overview

Problem

Conventional injection molding of polymers with high melting and processing temperatures, such as PET, experiences significant plate-out due to the deposition of low molecular weight additives on the mold surfaces, leading to costly production delays and reduced productivity.

Innovation Solution

The process involves pressurizing the mold cavity with a non-reactive gas or vapor during the injection molding of PET, which reduces the deposition of additives by maintaining the additives in solution and preventing their sublimation onto the mold surfaces, thereby minimizing plate-out.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional injection molding is used for PET with high melting temperature, then the polymer can be processed, but plate-out occurs on mold surfaces causing production delays

Engineering Contradiction:

Improveproduction continuityVSAvoidcleaning time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent introduces an inert atmosphere (nitrogen or carbon dioxide gas) into the mold cavity during injection molding to prevent plate-out of low molecular weight additives on mold surfaces. The inert gas creates a non-oxidizing environment that prevents the additives from depositing on the mold, thereby eliminating cleaning requirements and maintaining continuous production.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

Solution Approach 2:

The patent changes the atmospheric parameters within the mold cavity by introducing pressurized inert gas. This parameter change (from air to inert atmosphere) fundamentally alters the deposition behavior of additives, preventing plate-out without requiring changes to the polymer material or mold design.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If low molecular weight additives are used to improve gas barrier properties, then oxygen and carbon dioxide permeation is reduced, but plate-out occurs on mold surfaces

Engineering Contradiction:

Improvegas barrier performanceVSAvoidplate-out deposition

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The inert atmosphere prevents the low molecular weight additives from interacting with oxygen in the air, which eliminates the plate-out mechanism while preserving the additives' gas barrier functionality in the final product.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

Solution Approach 2:

The inert gas acts as an intermediary environment between the molten polymer and the mold surface, preventing direct contact and deposition of additives on the mold while allowing the polymer to be properly formed.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If mold cleaning is performed frequently to remove plate-out, then mold surface quality is maintained, but productivity decreases

Engineering Contradiction:

Improvemold surface qualityVSAvoidproduction rate

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

By maintaining an inert atmosphere throughout the molding process, the patent eliminates plate-out formation at its source, thereby maintaining mold surface quality without requiring intermittent cleaning operations that interrupt production.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

Solution Approach 2:

The inert atmosphere is maintained continuously throughout the molding process, providing ongoing protection against plate-out rather than requiring periodic interruptions for cleaning. This continuous protection ensures both surface quality and production efficiency.

Inventive Principle:

Principle #20Continuity of useful action

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

This approach significantly extends the running time of the injection molding apparatus by reducing plate-out, allowing for longer processing runs without the need for frequent cleaning and maintaining product quality.

Implementation Method 1

pressurizing the mold cavity with a non-reactive gas or vapor during the injection molding of PET, which reduces the deposition of additives by maintaining the additives in solution and preventing their sublimation onto the mold surfaces

Methodology Applied

Scientific EffectPressure Increase: Pressure Increase

Implementation Method 2

maintaining the additives in solution and preventing their sublimation onto the mold surfaces

Methodology Applied

Scientific EffectSublimation: Sublimation

Data Source

PatentUS7790077B2Pressurized tooling for injection molding and method of using

Publication Date: 2010.09.07 THE COCA COLA CO

AI summary

The present invention relates to an apparatus and process for injection molding polymer articles that reduces deposition of additives on the apparatus. Specifically, pressurizing of the mold cavity with a pressurized gas reduces the deposition of low molecular weight additives on the apparatus. Embodiments of the invention also include an apparatus for injection molding polymer articles comprising at least one pressurized gas inlet for introducing a pressurized gas into the mold cavity.