Coextrusion Blow Molding for Visual Effects

Solution Overview

Problem

Conventional coextrusion blow molding processes face limitations in producing multilayer hollow articles with specific visual effects due to interfacial instability and poor layer distribution caused by viscosity differences between polymer layers, which restrict the creation of desired surface patterns and visual appearances in blow-molded containers like bottles.

Innovation Solution

A coextrusion blow molding process involving two steps, where at least one layer is formed with a uniform thickness and another with varying thickness, utilizing polymers with controlled dynamic viscosities and extrusion rates to create a multilayer structure with a continuous and discontinuous layer configuration, resulting in a specific surface pattern and visual effect such as color swirls, waves, or translucency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional coextrusion blow molding processes are used with equal extrusion rates and similar viscosities for all layers, then stable and uniform layer distribution is achieved, but specific visual effects and surface patterns cannot be created

Engineering Contradiction:

Improvelayer distribution uniformityVSAvoidvisual effect creation

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent applies local quality by assigning different extrusion rates and viscosity characteristics to different polymer layers based on their desired function. The first polymer is extruded at a higher rate with lower viscosity to form a uniform continuous layer, while the second polymer is extruded at a lower rate with higher viscosity to create the visual effect layer with varying thickness. This localized differentiation of extrusion parameters enables both stable layer distribution and specific visual effects simultaneously.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the extrusion parameters (extrusion rate and viscosity) from the conventional uniform approach to a differentiated approach. By adjusting the extrusion rate ratio to be greater than 1:1 (first polymer extruded faster than the second) and controlling viscosity ratios, the process creates distinct layer characteristics. This parameter change enables the formation of continuous uniform layers combined with discontinuous visual effect layers, resolving the contradiction between uniformity and visual effect creation.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If the first polymer is extruded at a higher extrusion rate than the second polymer, then a continuous uniform layer is formed, but the second polymer forms a discontinuous layer with varying thickness

Engineering Contradiction:

Improvecontinuous layer uniformityVSAvoidlayer continuity

Core Design Contradiction:

Manufacturing precisionVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by assigning different extrusion rates and viscosity characteristics to different polymer layers based on their desired function. The first polymer is extruded at a higher rate with lower viscosity to form a uniform continuous layer, while the second polymer is extruded at a lower rate with higher viscosity to create the visual effect layer with varying thickness. This localized differentiation of extrusion parameters enables both stable layer distribution and specific visual effects simultaneously.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the extrusion parameters (extrusion rate and viscosity) from the conventional uniform approach to a differentiated approach. By adjusting the extrusion rate ratio to be greater than 1:1 (first polymer extruded faster than the second) and controlling viscosity ratios, the process creates distinct layer characteristics. This parameter change enables the formation of continuous uniform layers combined with discontinuous visual effect layers, resolving the contradiction between uniformity and visual effect creation.

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

The process effectively produces blow-molded hollow articles with pronounced visual effects and patterns by deviating from traditional equal extrusion rates and viscosities, allowing for the creation of containers with appealing designs that were previously challenging to achieve.

Implementation Method 1

These extruders force the plasticized polymers into a die head with one concentric channel for each layer

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Implementation Method 2

pressurized gas provides the blow molding of the hollow article to the shape of the mold cavity

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Data Source

PatentUS10906226B2Process for the production of multilayer blow-molded hollow articles

Publication Date: 2021.02.02 AVIENT COLORANTS ITALY SRL

AI summary

The present invention relates to blow molded multilayer hollow articles and a coextrusion blow molding process for the production of said multilayer hollow articles, made of thermoplastic polymers and characterized by a specific visual effect. More in particular, the present invention relates to multilayer hollow articles and a coextrusion blow molding process for the production of said multilayer hollow articles, wherein at least one layer is a continuous layer with a uniform degree of thickness and at least one layer is a discontinuous or a non-uniform continuous layer with varying degree of thickness, which results in a specific surface pattern and/or visual color effect.