Co-injection Molded Plastic Articles Structural Barrier Layer

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Solution Overview

Problem

In injection molding processes, achieving adhesion between the interior core layer and skin layers of plastic articles without the need for adhesives is challenging, as the barrier and skin materials often do not adhere to each other effectively, necessitating the use of adhesives to ensure cohesion and prevent delamination.

Innovation Solution

The method involves controlling the volumetric flow ratio of inner and outer polymeric streams during the molding process to form cohesion members that structurally interlock the interior core layer with the skin layers, eliminating or reducing the need for adhesives by shifting the interior core stream along specific streamlines within the mold cavity, thereby enhancing adhesion and preventing delamination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If adhesives are added to improve adhesion between interior core layer and skin layers, then bond strength is improved, but device complexity and manufacturing complexity increase

Engineering Contradiction:

Improveadhesion strengthVSAvoidmolding process complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the adhesive component from the molding process by using flow control to create structural interlocking features (protrusions and recesses) directly in the polymeric materials. This removes the need for separate adhesive materials and simplifies the manufacturing process while maintaining bond strength through mechanical interlocking.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the chemical bonding mechanism of adhesives with a mechanical interlocking system. By controlling the volumetric flow ratio during injection molding, structural features such as protrusions and recesses are formed that mechanically interlock the interior core layer with the skin layers, substituting chemical adhesion with mechanical connection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Stability of the object's composition

If adhesives are used to bond layers, then cohesion is improved, but loss of substance increases due to adhesive material consumption

Engineering Contradiction:

Improvelayer cohesionVSAvoidadhesive material consumption

Core Design Contradiction:

Stability of the object's compositionVSLoss of substance

Solution Approach 1:

The patent removes the adhesive substance entirely from the system by using flow-controlled polymeric materials to create structural interlocking features. This eliminates material consumption associated with adhesives while maintaining layer cohesion through mechanical integration of the layers during the molding process.

Inventive Principle:

Principle #2Taking out (Extraction)

3Strength

If volumetric flow ratio is controlled to form cohesion members, then adhesion is improved without adhesives, but manufacturing precision requirements increase

Engineering Contradiction:

Improveinterlayer adhesionVSAvoidflow control precision

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent changes the volumetric flow ratio parameter during the injection molding process to create structural interlocking features. By dynamically adjusting the flow ratio between different polymeric materials, the process forms protrusions and recesses that provide mechanical interlocking, achieving adhesion through controlled material flow rather than chemical bonding.

Inventive Principle:

Principle #35Parameter changes

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 effectively secures the interior core layer to the skin layers without adhesives, improving the cohesion and resistance to delamination, and reducing the need for adhesive compounds in the molding process, while also allowing for cosmetic effects and material differentiation in the final product.

Implementation Method 1

The combined stream is then forced along the annular pathways of the mold cavity to form a molded plastic article

Methodology Applied

Scientific EffectPressure-driven flow: Pressure Gradient

Implementation Method 2

The combined stream includes an annular interior core stream sandwiched between an annular inner stream and an annular outer stream

Methodology Applied

Scientific EffectCo-extrusion: Extrusion

Data Source

PatentUS9511526B2Methods and systems for the preparation of molded plastic articles having a structural barrier layer

Publication Date: 2016.12.06 MILACRON INC

AI summary

Disclosed herein are methods and systems for the preparation of a co-injection molded multilayer plastic article. Some methods include co-extruding a combined polymeric stream having an interior core stream encased by an inner stream and an outer stream. A volumetric ratio of the inner stream to outer stream is adjusted during injection of the combined stream into the a mold cavity to alter a streamline along which the interior core stream flows thereby forming cohesion member that structurally interlocks the interior layer with the inner layer, with the outer layer or with both. Some embodiments reduce or eliminate a need for addition of an adhesive in the composite stream to prevent delamination of layers of the resulting multilayer plastic article. In some embodiments, cohesion members may be employed to produce a desired cosmetic effect in a resulting article.