Paper Coating Composition Using Polycarbodiimide Curing Agent
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Solution Overview
Problem
Paper food containers, such as paper cups, lack sufficient water resistance and durability due to inadequate adhesion properties of existing coatings, particularly those using ethylene-(meth)acrylic acid copolymers with low (meth)acrylic acid content, which leads to reduced polarity and poor cross-linking.
Innovation Solution
A paper coating composition comprising an ethylene-(meth)acrylic acid copolymer, a basic compound, and a polycarbodiimide-based curing agent with a specific carbodiimide group equivalent range, which forms a coating layer with improved adhesion and water resistance by cross-linking the copolymer, preventing polarity reduction and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ethylene-(meth)acrylic acid copolymer with low (meth)acrylic acid content is used for coating, then water resistance is improved, but adhesion properties to polar substrate deteriorate due to reduced polarity
Solution Approach 1:
The patent changes the chemical parameters of the copolymer by controlling the (meth)acrylic acid content within 10-30 wt% and adjusting the weight average molecular weight to 10,000-60,000. These parameter optimizations balance the polarity needed for adhesion with the water resistance properties, resolving the contradiction between improved water resistance and maintained adhesion.
Solution Approach 2:
The patent creates a composite coating system by combining ethylene-(meth)acrylic acid copolymer with specific additives and curing agents. This composite approach allows the copolymer to provide water resistance while the composite formulation maintains adhesion properties through synergistic interactions between components.
2Reliability
If cross-linking between carboxylic acids is increased to improve water resistance, then polarity is reduced, but adhesion properties to polar substrate deteriorate
Solution Approach 1:
The patent optimizes the carboxylic acid content parameter by limiting (meth)acrylic acid to 10-30 wt%, preventing excessive cross-linking that would reduce polarity. This parameter control ensures sufficient cross-linking for water resistance while maintaining enough polarity for adhesion to polar substrates.
3Productivity
If coating composition is simplified to reduce manufacturing complexity, then production efficiency improves, but water resistance and durability are insufficient
Solution Approach 1:
The patent achieves multi-functionality within the coating composition, where the ethylene-(meth)acrylic acid copolymer simultaneously provides adhesion to polar substrates, water resistance, and durability. This universal approach allows a single coating formulation to deliver multiple performance benefits without requiring complex multi-layer systems, thus maintaining manufacturing efficiency while improving reliability.
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 composition significantly improves the water resistance and durability of paper containers by forming a smooth coating layer with reduced water permeability and enhanced adhesion to polar substrates, maintaining container integrity over time.
Implementation Method 1
due to cross-linking between carboxylic acids, a polarity of the copolymer is considerably reduced
Implementation Method 2
a polycarbodiimide-based curing agent... equivalent of carbodiimide group of the curing agent ranges from 150 to 350
Implementation Method 3
a basic compound... content of the basic compound may range from 0.1% to 5% by weight
Data Source
Figure 1~2
Figure 3~4
AI summary
A composition for coating a paper according to embodiments of the present invention includes an ethylene-(meth)acrylic acid copolymer and a polycarbodiimide-based curing agent. By applying the paper coating composition to a paper and then drying the same, a coated paper with improved water resistance can be provided.