Foldable Paper Substrates Coated with Flexible Aqueous Dispersion
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Solution Overview
Problem
Current water-based coatings for foldable paper products are not suitable for maintaining barrier properties when folded, as they crack and lose resistance, whereas polyethylene coatings, although recyclable, are not repulpable and environmentally friendly alternatives are needed.
Innovation Solution
A foldable paper-based substrate coated with a wax-free primer coat and a top coat, both aqueous dispersions, providing flexibility and barrier properties such as water resistance, grease resistance, and heat resistance, with the primer coat having a dry film flexibility of at least 1100% and the top coat having a dry film flexibility of at least 570%, ensuring the coating remains effective even when folded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water-based coatings are used on foldable paper products, then environmental friendliness and recyclability are improved, but the coating cracks when folded and loses barrier properties
Solution Approach 1:
The patent changes the physical-chemical parameters of the coating by using aqueous dispersions with specific flexibility characteristics (elongation-to-break of at least 570% for top coat and at least 1100% for primer coat). This parameter change allows the coating to stretch and flex without cracking when the paper is folded, while maintaining water-based environmental friendliness and recyclability.
Solution Approach 2:
The patent uses a composite coating system consisting of multiple layers (top coat and primer coat) with different polymer compositions and flexibility characteristics. The top coat provides barrier properties with moderate flexibility, while the primer coat provides high flexibility to prevent cracking. This composite structure combines the benefits of both requirements.
2Strength
If polyethylene coatings are used to provide barrier properties, then grease resistance, water resistance, and heat resistance are improved, but the coating is not repulpable and reduces recyclability
Solution Approach 1:
The patent changes the chemical composition parameter by replacing polyethylene with water-based aqueous dispersions of polymers and copolymers. This chemical substitution maintains the barrier properties (grease, water, and heat resistance) while enabling repulpability and recyclability, as water-based coatings can be removed and the paper can be reprocessed.
3Reliability
If known water-based coatings are applied to foldable cardboard, then environmental friendliness is improved, but cracks form in the folds and barrier properties decrease
Solution Approach 1:
The patent changes the flexibility parameter of the water-based coating by selecting polymers and copolymers with specific elongation-to-break values (at least 570% for top coat, at least 1100% for primer coat). This ensures the coating can accommodate the deformation during folding without cracking, maintaining barrier property integrity while remaining environmentally friendly.
Solution Approach 2:
The patent applies the coating with predetermined flexibility characteristics before the folding operation. The high flexibility of the applied coating film prevents crack formation during subsequent folding, thereby preserving barrier properties without requiring post-application modifications.
Data Source
AI summary
A foldable paper-based substrate coated with primer coat and top coat. Primer coat includes a wax-free aqueous dispersion wherein a dry film thereof has a flexibility of at least 1100% for a film thickness from about 1.0 to about 2.5 mm. Top coat is blocking resistant and includes an aqueous dispersion of a polymer providing water resistance, grease or oil resistance, heat resistance, odor barrier, moisture barrier and/or heat sealability to the paper-based product. The top coat aqueous dispersion is characterized in that a dry film thereof has a flexibility of at least 570% for a film thickness from about 1.5 to about 2.5 mm. A process for preparing the coated foldable paper-based substrate includes applying the primer coat to the surface of the paper-based substrate, applying the top coat and drying the coats. The primer coat may be dried before application of the top coat.