Polymer Microparticle Coating for Food Container Seals
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Solution Overview
Problem
Current polymer dispersions used in coating metal food and drink containers face limitations due to high viscosity and particle size, leading to sedimentation issues, uneven coating distribution, and variable seal strengths, which affect the shelf life and safety of the contents.
Innovation Solution
A dispersion of polymer microparticles is developed, comprising a reaction product of polypropylene with carboxylic acid and/or carboxylic acid anhydride groups and a second polymer, dissolved in an organic liquid, which forms a core-shell structure to enhance stability and adhesion, allowing for higher solid content and improved distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polypropylene dispersions with large mean particle size (approximately 10 μm) are used, then the coating can be made with sufficient flexibility and adhesion, but the dispersion viscosity becomes too high and sedimentation occurs
Solution Approach 1:
The patent divides the polypropylene into smaller microparticles (0.1-10 μm) rather than using large particles (approximately 10 μm), which segments the particle size distribution and reduces viscosity while maintaining coating performance. This segmentation allows the dispersion to remain stable without sedimentation while still providing adequate flexibility and adhesion.
Solution Approach 2:
The patent changes the particle size parameter from large (approximately 10 μm) to small (0.1-10 μm) microparticles, and adjusts the solids content parameter to 15-60% non-volatile content. These parameter changes reduce dispersion viscosity and prevent sedimentation while maintaining the required coating properties.
2Quantity of substance
If polypropylene dispersions with high solids content are used, then more polypropylene can be incorporated into the coating, but the dispersion viscosity increases and sedimentation occurs
Solution Approach 1:
The patent optimizes the solids content parameter to 15-60% non-volatile content, which is higher than conventional dispersions but maintained stable by using small microparticles. This parameter change allows more polypropylene to be incorporated while preventing viscosity issues and sedimentation through the small particle size.
3Ease of manufacture
If large polypropylene particles (average diameter of 10 μm) are used in the coating, then the coating can be applied, but the particles protrude beyond the surface creating uneven distribution and variable seal strengths
Solution Approach 1:
The patent segments the polypropylene into small microparticles (0.1-10 μm) instead of large particles (10 μm), which allows the particles to be fully embedded in the coating matrix without protruding. This segmentation achieves uniform coating distribution and consistent seal strengths while maintaining ease of application.
Solution Approach 2:
The patent changes the particle size parameter from 10 μm to 0.1-10 μm, which ensures particles do not protrude beyond the coating surface. This parameter change achieves even coating distribution and uniform seal strengths while maintaining coating applicability.
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 solution provides a stable, evenly distributed coating with enhanced adhesion and seal strength, reducing sedimentation and energy consumption, while meeting stringent safety and shelf life requirements for food and beverage containers.
Implementation Method 1
the polymer comprising the reaction product of i) from 2 to 40 parts by weight of a first polypropylene polymer having sufficient carboxylic acid and/or carboxylic acid anhydride groups
Implementation Method 2
A dispersion of polymer microparticles is developed, comprising a reaction product of polypropylene with carboxylic acid and/or carboxylic acid anhydride groups and a second polymer, dissolved in an organic liquid
Implementation Method 3
The lid is attached to the tray by means of a coating, usually crosslinked, which on application of heat and pressure forms an adhesive bond or seal between the lid and the tray
Implementation Method 4
The lid is attached to the tray by means of a coating, usually crosslinked, which on application of heat and pressure forms an adhesive bond or seal between the lid and the tray
Data Source
AI summary
A dispersion of polymer microparticles in organic liquid, the polymer comprising the reaction product of i) from 2 to 40 parts by weight of a first polymer being polypropylene polymer having sufficient carboxylic acid and/or carboxylic acid anhydride groups equivalent to an acid value of from 2 to 50 mg KOH/g nv polymer and ii) from 60 to 98 parts by weight of a second polymer having a molar excess of functional groups capable of reacting with the carboxylic acid and/or carboxylic acid anhydride groups of the polypropylene polymer and wherein the organic liquid is chosen to be a good solvent for the second polymer and a poor solvent for the polypropylene polymer.