Aqueous Polyolefin Dispersion Emulsifier-Free Process
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Solution Overview
Problem
Existing processes for preparing aqueous polyolefin dispersions, such as those described in WO2001/64774 and WO2005/085331, face challenges with high pressure build-up in extruders and lack clarity on dispersion collection, as well as the inability to produce homogeneous dispersions from combinations of high molecular weight polar and non-polar polymers.
Innovation Solution
A process involving the intimate mixing of solid components at 50°C to 200°C, followed by mixing with water and a neutralizing agent at a temperature 2 to 20°C above the highest melting temperature, to create an aqueous polyolefin dispersion with particle sizes below 150 µm, without the need for additional emulsifiers, using a twin screw extruder and elevated pressure, and incorporating specific polymer blends like copolymers of polyethylene and (meth)acrylic acid, and other polymers for enhanced heat sealability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high shear mixing is used to prepare aqueous polyolefin dispersions, then the polymer can be dispersed in water above its melting temperature, but high pressure build-up occurs inside the extruder and the process lacks clarity on dispersion collection
Solution Approach 1:
The patent changes the temperature parameter to be specifically above the melting temperature of the polymer (by 2 to 20°C), which allows the polymer to become sufficiently mobile for dispersion without requiring excessive mechanical energy input that would cause high pressure build-up. This temperature optimization resolves the contradiction between ease of manufacture and pressure control.
2Manufacturing precision
If conventional extrusion processes are used, then polymer dispersion can be achieved, but it is not disclosed how homogeneous dispersions can be prepared from combinations of high molecular weight polar and non-polar polymers
Solution Approach 1:
The patent applies preliminary action by first intimately mixing all solid components (including multiple high molecular weight polar and non-polar polymers) at elevated temperature to form a homogeneous compound before adding water. This pre-mixing step ensures uniform distribution of incompatible polymers, achieving homogeneous dispersions without complex processing equipment.
Solution Approach 2:
The patent creates composite materials by combining high molecular weight polar polymers (such as polyacrylic acid) and non-polar polymers (such as polyethylene) in a intimate mix before dispersion. This composite approach allows the formation of homogeneous dispersions containing multiple polymer types that would otherwise be incompatible, resolving the contradiction between manufacturing precision and device complexity.
3Ease of manufacture
If emulsifiers are used in the dispersion process, then polymer dispersion can be achieved, but food safety concerns and heat sealability issues arise
Solution Approach 1:
The patent extracts and removes emulsifiers from the dispersion process entirely. Instead of using chemical emulsifiers, it relies on thermal energy (heating above polymer melting temperature) and mechanical mixing to achieve dispersion. This elimination of emulsifiers resolves the contradiction by maintaining ease of manufacture while removing harmful factors related to food safety and heat sealability.
Solution Approach 2:
The patent applies self-service by allowing the polymer itself to facilitate its own dispersion through its own melting and mobility at elevated temperature, without requiring external emulsifying agents. The polymer's inherent properties at elevated temperature enable spontaneous dispersion in water, achieving both ease of manufacture and food safety/heat sealability compatibility.
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 process allows for the production of stable, food-safe aqueous polyolefin dispersions with improved heat sealability and enhanced sealing strength, particularly for aluminum foils, while avoiding the use of emulsifiers and achieving homogeneous particle distributions.
Implementation Method 1
all solid components of dispersion A are intimately mixed at a temperature in the range of 50°C to 200°C after which a homogenous compound of all components is obtained
Implementation Method 2
the homogeneous compound is mixed with water, compound B, and a neutralizing agent at a temperature which is 2 to 20°C above the highest melting temperature of the components mixed in the first step until an aqueous dispersion is obtained wherein all dispersed particles have a particle size below 150 μm
Data Source
AI summary
The invention relates to an aqueous polyolefin dispersion comprising from 50 to 100 wt.% of a aqueous dispersion A comprising the following ingredients: from 30 to 90 wt.% of A1, a copolymer of polyethylene and (meth)acrylic acid [E(M)AA] or a mixture of different copolymers of polyethylene and (meth)acrylic acid, from 10 to 70 wt.% of A2, another polymer, not being a copolymer of polyethylene and (meth)acrylic acid, or a mixture of other polymers, and from 0 - 15 wt.% of additive from 0 to 50 wt.% of a compound B, where compound B is a material dispersable or soluble in water and different from any of the ingredients of dispersion A wherein the wt.% of A and B is based on the solid content of the whole aqueous polyolefin dispersion and the wt% of the ingredients of dispersion A is based on the solid content of dispersion A, the sum of the wt.% of ingredients i to iii of dispersion A is 100%.