Aqueous Barrier Coating for Cellulosic Substrates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current aqueous coatings for cellulosic substrates fail to achieve the balanced properties of LDPE extruded paperboards, including effective barrier resistance to water, oil, and grease, heat sealability, roll blocking resistance, and over-printability, while also being recyclable and repulpable.
Innovation Solution
An aqueous barrier coating comprising a blend of crystalline polymer binder dispersion and active filler, with a crystallinity percentage greater than 50%, providing a shear storage modulus range suitable for heat sealability and barrier properties, applied on cellulosic substrates with an optional aqueous sealing primer for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If aqueous coatings are used to replace LDPE extrusion coating for recyclability and repulpability, then environmental friendliness is improved, but barrier properties against water, oil, and grease deteriorate
Solution Approach 1:
The patent uses a composite coating system consisting of an aqueous polymer binder dispersion combined with specific fillers (clay, talc, calcium carbonate) and surfactants. This composite structure achieves both environmental friendliness through aqueous formulation and effective barrier properties through the synergistic combination of materials that provide water, oil, and grease resistance.
Solution Approach 2:
The patent modifies the chemical and physical parameters of the aqueous coating by controlling polymer concentration (10-50% solids), adjusting pH levels (7-10), and optimizing filler content (20-80 wt%) to achieve barrier performance comparable to LDPE while maintaining recyclability and repulpability.
2Object-affected harmful factors
If aqueous coatings are used to replace LDPE extrusion coating, then repulpability and recyclability are improved, but heat sealability deteriorates
Solution Approach 1:
The patent selects polymer binders with specific glass transition temperatures (Tg between -50°C and 0°C) and controlled molecular weights to achieve heat sealability at conventional sealing temperatures (80-150°C). The polymer composition and crosslinking density are adjusted to provide adequate melt flow and adhesion during heat sealing while maintaining aqueous-based repulpability.
Solution Approach 2:
The coating formulation incorporates specific functional components at localized concentrations: polymer binders (10-50% solids) for adhesion and sealability, fillers (20-80 wt%) for barrier properties, and surfactants (0.1-5 wt%) for surface tension control. This localized optimization of material properties throughout the coating matrix enables simultaneous achievement of heat sealability and repulpability.
3Object-affected harmful factors
If aqueous coatings are used to replace LDPE extrusion coating, then environmental friendliness is improved, but roll blocking resistance deteriorates
Solution Approach 1:
The patent controls the glass transition temperature (Tg) of the polymer binder within a specific range (-50°C to 0°C) and adjusts the coating's surface properties through surfactant selection and concentration (0.1-5 wt%). These parameter adjustments ensure the coating remains flexible and non-tacky at storage temperatures, preventing roll blocking while maintaining aqueous-based environmental friendliness.
Solution Approach 2:
The patent uses surfactants as intermediary substances that modify the surface tension and interfacial properties of the aqueous coating. These surfactants create a non-stick surface layer that prevents bonding between coated surfaces during storage and handling, thereby providing roll blocking resistance while the aqueous formulation maintains environmental friendliness.
4Object-affected harmful factors
If aqueous coatings are used to replace LDPE extrusion coating, then repulpability is improved, but barrier properties against hot liquids deteriorate
Solution Approach 1:
The patent employs a composite coating system with heat-resistant components including specific fillers (clay, talc, calcium carbonate) and heat-stable polymer binders. This composite structure provides effective barrier properties against hot liquids and steam while maintaining the aqueous-based formulation that enables repulpability and recyclability.
Solution Approach 2:
The patent optimizes the coating's crosslinking density, filler content (20-80 wt%), and polymer molecular weight to enhance thermal stability and barrier performance against hot liquids. These parameter adjustments ensure the coating maintains its integrity and barrier function at elevated temperatures while preserving repulpability through controlled polymer composition.
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 achieves easy repulpability, recyclability, heat sealability, resistance to roll blocking, and good barrier properties against water, oil, and grease, including hot liquids, while maintaining over-printability, effectively replacing LDPE extruded coatings.
Implementation Method 1
crystallinity is present in at least in one of the at least one polymer binder dispersion (composition A) or the least one active filler (composition B)
Implementation Method 2
the resulting dried film has a shear storage modulus between 50° C. and 60° C. in the range of 1.5×106 to 1×109 Pascals, a shear storage modulus between 80° C. and 90° C. in the range of 2×105 to 5×107 Pascals, and a shear storage modulus between 100° C. and 110° C. in the range of 5×103 to 1×106 Pascals
Implementation Method 3
having resistance to the permeation of water, oil, grease, and other cold and hot liquids
Implementation Method 4
Crystallinity in LDPE film helps the polymer to melt readily when the melting point is reached to provide the seal and its fast recrystallization during the cooling step allows fast securance of the seal
Implementation Method 5
most polymers or binders in aqueous coatings are amorphous and become soft and sticky at elevated temperature (even at 50-55° C.) and/or pressure in production, converting, shipping, and storage of the coated board causing blocking
Data Source
AI summary
An aqueous barrier coat for formable cellulosic substrates comprises a blend of A) at least one aqueous polymer binder dispersion at 40 wt % to 95 wt %, B) at least one active filler at 3 wt % to 30 wt % and, C) one or more optional additives, such as wetting additives, dispersants, thickeners, defoamers, and crosslinkers. Crystallinity is present in at least one of the polymer binder dispersion and active filler particle. The resulting dried film has a shear storage modulus between 50° C. and 60° C. in the range of 1.5×106 to 1×109 Pascals, a shear storage modulus between 80° C. and 90° C. in the range of 2×105 to 5×107 Pascals, and a shear storage modulus between 100° C. and 110° C. is in the range of 5×103 to 1×106 Pascals. The total weight % of crystalline polymer binder and the crystalline active filler combined is greater than 50%.