High Density Paper Oxygen Barrier via Blade Coating and Supercalendering
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Solution Overview
Problem
Existing paper laminates with aluminum and polyethylene for food packaging face challenges with recyclability and carbon footprint, while providing adequate oxygen barrier properties.
Innovation Solution
A method involving blade coating and supercalendering a paper substrate at a moisture content of 4-9% with an aqueous coating composition containing PVOH or starch, followed by drying and supercalendering, to produce a high-density paper with improved oxygen barrier properties and recyclability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If paper is laminated with aluminum or polyethylene film to provide barrier properties, then oxygen barrier properties are improved, but recyclability and carbon footprint deteriorate
Solution Approach 1:
The patent removes the problematic laminate layers (aluminum or polyethylene) from the packaging structure and replaces them with a coating applied directly to the paper substrate. This extraction of the problematic elements eliminates the recyclability issues while maintaining the barrier function through the coating's porous structure control.
Solution Approach 2:
The patent uses a composite coating system consisting of a polymer matrix (such as polyvinyl alcohol, starch, or cellulose derivatives) combined with inorganic fillers (such as clay, silica, or calcium carbonate). This composite structure provides both the barrier properties and the recyclability, as the coating can be removed and the paper substrate recycled without contamination from metal or plastic laminates.
2Reliability
If coating composition is applied to paper substrate to improve oxygen barrier, then barrier properties are improved, but blocking during processing increases
Solution Approach 1:
The patent optimizes multiple parameters of the coating composition including polymer type, molecular weight, concentration, and the addition of cross-linking agents. It also controls the coating weight, moisture content during supercalendering (4-9%), and nip impulse. These parameter changes allow the coating to form a porous structure that provides barrier properties while preventing excessive blocking during the supercalendering process.
Solution Approach 2:
The patent creates a coating layer with specific local properties - a porous structure with controlled pore size and distribution. The coating composition is designed to form a homogeneous layer with uniform pore structure throughout, providing consistent barrier properties while maintaining processability. The cross-linking agent creates localized cross-linked regions that prevent blocking during supercalendering.
3Volume of stationary object
If supercalendering is performed at high nip impulse to achieve high density, then density is improved, but energy consumption and blocking increase
Solution Approach 1:
The patent changes the moisture content parameter during supercalendering to an optimal range of 4-9%, which allows achieving high density (≥900 kg/m³) at reduced nip impulse (120-400 kPa·s). The coating composition parameters are also optimized to enable densification at lower energy input, reducing both energy consumption and blocking while maintaining the desired density.
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 method results in a high-density paper with reduced blocking and energy consumption, enhanced oxygen barrier properties, and improved recyclability compared to conventional laminates.
Implementation Method 1
the aqueous coating composition may penetrate the paper substrate from two sides and thereby more efficiently fill the pores in the paper substrate
Implementation Method 2
coating the paper substrate with an aqueous coating composition using a blade coater
Implementation Method 3
supercalendering the dried coated paper at a moisture content of 4-9 %
Data Source
AI summary
There is provided a method for producing a high-density paper comprising the steps of: a) providing or producing a paper substrate; b) coating the paper substrate with an aqueous coating composition using a blade coater to obtain a coated paper; c) drying the coated paper to obtain a dried coated paper; and d) supercalendering the dried coated paper at a moisture content of 4-9 %, such as 4-8%.