Sodium Silicate Coating for Corrugated Cardboard Water Resistance
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Solution Overview
Problem
Corrugated cardboard loses rigidity and effectiveness in humid conditions due to water absorption, and existing waterproof coatings like paraffin pose recycling challenges and increase costs by requiring heavier materials for strength.
Innovation Solution
A coating composition comprising sodium silicate, latex resin emulsion, and paraffin-water emulsion, applied to the fluting of corrugated cardboard, forming a water-resistant and flexible film that enhances strength without increasing weight, allowing for thinner paper usage and easy recycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If paraffin coating is applied to provide water resistance, then water resistance is improved, but recyclability deteriorates due to mass formation in repulping vat
Solution Approach 1:
The patent removes paraffin from the coating composition entirely, extracting the problematic substance that causes mass formation during recycling while maintaining water resistance through alternative materials like starch and cellulose derivatives
Solution Approach 2:
The patent changes the chemical composition parameters by substituting paraffin with starch-based and cellulose-based materials, fundamentally altering the coating's chemical properties to achieve both water resistance and recyclability
2Strength
If higher weight basis cardboard is used to provide stacking strength, then stacking strength is improved, but cost increases
Solution Approach 1:
The patent uses composite coating materials combining starch, cellulose derivatives, and plasticizers to create a strength-enhancing layer that provides stacking strength without requiring increased cardboard weight basis
Solution Approach 2:
The patent applies a thin film coating composition that, despite its minimal thickness, provides sufficient strength enhancement through the synergistic combination of starch matrix, cellulose reinforcement, and plasticizer flexibility
3Object-affected harmful factors
If paraffin coating is applied to prevent water contact, then water resistance is improved, but manufacturing complexity increases due to separation requirements
Solution Approach 1:
The patent extracts paraffin from the system entirely, eliminating the source of separation problems in repulping vats and simplifying the recycling process without compromising water resistance
Solution Approach 2:
The patent employs starch-based materials that are inherently biodegradable and easily separable in water, replacing durable but problematic paraffin with materials designed for easy disposal and recycling
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 coating composition provides enhanced strength, water resistance, and recyclability, enabling corrugated boxes to withstand humid environments while reducing material costs and ecological impact, with improved stack strength and crush resistance without the need for expensive adhesives.
Implementation Method 1
the coating composition provides enhanced strength, water resistance
Implementation Method 2
forming a water-resistant and flexible film that enhances strength
Data Source
AI summary
A low-cost and effective coating composition for cardboard allows use of thinner paper board with the same or higher strength relative to conventional water-resistant cardboard. The resulting cardboard can also be repulped and more easily recycled. The inventive coating composition, preferably applied to the fluted inner ply of the cardboard (as a waterproof barrier), is compatible with the utilization of low-cost starch-based adhesives for gluing the fluting to the liners. At least one side of the fluting cardboard is coated with a composition comprising: from about 10% to 70% by weight, and more preferably from about 40% to 60% by weight, of sodium silicate; from about 10% to 60% by weight, and more preferably from about 30% to about 50% by weight, of a synthetic resin emulsion; from about 10% to 50% of a paraffin-water emulsion; and from about 5% to about 25% by weight of added water.