Polymer Coating Void Formation for Smoothness Without Density
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for producing coated paper or paperboard with high stiffness and smoothness often result in increased density, which is undesirable, as they require calendering processes that reduce caliper and increase density, compromising the balance between stiffness and smoothness.
Innovation Solution
A method involving the application of a polymer film-forming coating to a substrate, which is then brought into contact with a heated surface while still wet, causing boiling and forming voids under the surface, thereby achieving smoothness and stiffness without significant densification, using a water-soluble polymer and a release agent, and optionally a crosslinking solution to create a partially crosslinked polymer film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If calendering processes are used to improve surface smoothness and stiffness, then surface quality improves, but density increases and caliper reduces
Solution Approach 1:
The patent applies phase transition by bringing the wet polymer coating into contact with a heated surface, causing the water to boil and transition from liquid to vapor phase. This creates voids beneath the polymer surface while the polymer itself transitions from a wet state to a dried, crosslinked film, achieving smoothness without the densification caused by mechanical calendering
Solution Approach 2:
The patent changes the physical and chemical parameters of the coating system by using a water-soluble polymer with specific glass transition temperature, adjusting the polymer concentration, and controlling the heating temperature and crosslinking conditions. These parameter changes enable the coating to form a smooth surface through boiling rather than mechanical compression
2Manufacturing precision
If calendering processes are used to improve surface smoothness, then surface quality improves, but caliper reduces
Solution Approach 1:
By utilizing the phase transition of water to vapor through boiling on the heated surface, the process creates a void structure that maintains caliper thickness while achieving surface smoothness, avoiding the caliper reduction inherent in mechanical calendering processes
3Strength
If conventional coating methods are used, then coating is applied to substrate, but surface smoothness and stiffness are insufficient
Solution Approach 1:
The patent creates a composite structure consisting of a polymer film-forming composition with voids distributed throughout. This composite material combines the stiffness-providing polymer matrix with voids that prevent excessive densification, achieving both surface smoothness and structural stiffness simultaneously
Solution Approach 2:
The phase transition of water to vapor during the heating process creates a unique microstructure with voids that enhance both surface smoothness and bulk stiffness, as the voids prevent polymer chain collapse and maintain structural integrity
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 approach enhances surface smoothness and flatness without increasing density, allowing for improved printability and stiffness while maintaining the initial caliper of the paper, thus offering a more economical and efficient production process compared to traditional calendering methods.
Implementation Method 1
bringing the polymer coating into contact with a heated surface while the polymer coating is still in a wet state... causing boiling and forming voids under the surface
Implementation Method 2
bringing the polymer coating into contact with a heated surface while the polymer coating is still in a wet state
Data Source
AI summary
A method for treating a substrate is described. In accordance with one aspect, the method includes applying a polymer coating to a substrate, and bringing the polymer coating into contact with a heated surface in a pressure nip while the coating is still in a wet state. Optionally the polymer coating may include a crosslinkable material, and a crosslinking agent may be used to promote crosslinking. The polymer coating replicates the heated surface. A product produced in accordance with the described method is also disclosed. The product is characterized by having subsurface voids within the coating.