Multilayer Polymer Coating for Bio-Based Packaging Adhesion
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Solution Overview
Problem
Current methods for extrusion coating of polymer layers onto fibrous bases like paper or cardboard face challenges in achieving good adhesivity, heat sealing, and vapor barrier properties, especially with bio-based polymers like bio-LLDPE, which are not well-suited for this application due to poor runnability and high costs.
Innovation Solution
A multilayer coating comprising an innermost layer of a blend of 10-25 wt-% branched LDPE and 75-90 wt-% linear LLDPE, a middle vapor barrier layer, and an outermost heat-seal layer, all coextruded onto the fibrous base, excluding high-density polyethylene (HDPE) in excess of 90 wt-%, to enhance adhesion, runnability, and heat sealing while increasing the use of bio-based materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If bio-LLDPE is used for extrusion coating onto fibrous base, then bio-based material share is increased, but adhesivity and runnability deteriorate
Solution Approach 1:
The patent applies composite materials by creating a multilayer coating structure where an innermost layer combines bio-LLDPE with conventional LDPE and/or LLDPE. This composite approach allows the bio-based material to be used while conventional polymers provide the necessary adhesivity and runnability properties that pure bio-LLDPE lacks for extrusion coating applications.
2Quantity of substance
If LLDPE blend is used for coating, then cost is reduced compared to bio-LDPE, but adhesivity to fibrous base deteriorates
Solution Approach 1:
The patent applies local quality by assigning different functional roles to different layers of the coating. The innermost layer contains the LLDPE blend optimized for cost-effectiveness and runnability, while the outer layers provide the necessary adhesivity and protective functions. This spatial differentiation of material properties allows cost reduction without sacrificing overall coating performance.
3Quantity of substance
If coating layer weight is reduced, then material usage is optimized, but vapor barrier and heat sealing properties deteriorate
Solution Approach 1:
The patent applies segmentation by dividing the coating into multiple functional layers, each optimized for specific properties. The innermost layer provides adhesion and runnability, while outer layers provide vapor barrier and heat sealing functions. This segmented structure allows each layer to be optimized independently, achieving lightweight overall coating while maintaining necessary functional properties through the collective performance of specialized layers.
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 results in improved strength of sealing, runnability, and adhesion to the fibrous base, allowing for a higher share of bio-based materials at a lower cost, with enhanced vapor barrier properties and reduced coating weights, suitable for producing disposable products like drinking cups and other packaging materials.
Implementation Method 1
a multilayer coating comprising an innermost polymer layer containing a blend of (i) 10 to 25 wt-% of a branched low-density polyethylene (LDPE) having a melt index of at least 25 g/10 min (190 °C, 2.16 kg)
Implementation Method 2
the innermost layer adhering the coating to said fibrous base
Implementation Method 3
a middle polymer layer, and an outermost heat-seal layer of the same blend as said innermost layer
Implementation Method 4
an outermost heat-seal layer of the same blend as said innermost layer, the innermost layer adhering the coating to said fibrous base and the outermost layer forming a heat-seal layer
Data Source
Figure 1~3
AI summary
The invention relates to a polymer-coated packaging material, a method of manufacturing the same, and products, such as a disposable drinking cup, made from the material. The packaging material comprises a fibrous base (1) of paper or board and an extruded polymer layer (2) containing a blend of (i) 0 to 25 wt-% of a branched low-density polyethylene (LDPE)with a lower melt viscosity and (ii) 75 to 90 wt-% of a linear low-density polyethylene (LLDPE) with a higher melt viscosity. The packaging material of the invention comprises multilayer coatings, e.g.an adhesive innermost and a heat-sealable outermost layer (2, 4) of said blend and a vapour barrier middle layer (3) of at most 90 wt- % of high density polyethylene (HDPE). The layers (2, 3, 4) are brought and adhered to the fibrous base (1) by coextrusion. To maximize renewability of the materials HDPE and LLDPE as used for the structure are of biologic origin.