Polymer-Coated Packaging Material for Heat-Sealable HDPE Cups
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Solution Overview
Problem
Current biodegradable polyethylene coatings, such as bio-HDPE, face challenges in heat-sealability and adhesivity when used for extrusion coating on fibrous bases like paper or cardboard, limiting their application in packaging materials like disposable drinking cups due to high melting temperatures and narrow molecular weight distribution.
Innovation Solution
A coextrusion process is developed using a blend of 10-25 wt-% low-density polyethylene (LDPE) and 75-90 wt-% high-density polyethylene (HDPE) as an inner layer, with an outer layer of over 90 wt-% HDPE, to enhance adhesion and heat-sealability, while maintaining a superior water vapor barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pure HDPE is used for extrusion coating to achieve superior water vapour barrier, then water vapour barrier performance is improved, but heat-sealability and adhesivity deteriorate due to higher melting temperature
Solution Approach 1:
The patent combines HDPE and LLDPE in a multilayer coextrusion system where HDPE provides water vapour barrier and LLDPE provides heat-sealability. The layers are merged during coextrusion onto the fibrous base, allowing both polymers to work together to fulfill multiple functional requirements simultaneously.
Solution Approach 2:
The invention uses composite material structure with multiple polymer layers (HDPE and LLDPE) coated on fibrous base. Each layer contributes different properties: HDPE layer provides water vapour barrier while LLDPE layer provides heat-sealability and adhesivity, creating a composite packaging material with superior overall performance.
2Reliability
If pure HDPE is used for extrusion coating to achieve water vapour barrier, then water vapour barrier is improved, but adhesivity to fibrous base deteriorates
Solution Approach 1:
The patent merges HDPE and LLDPE layers in a coextrusion process where LLDPE provides adhesivity to the fibrous base while HDPE provides water vapour barrier. The combination allows the coating system to adhere properly to the substrate while maintaining barrier properties.
Solution Approach 2:
The composite structure uses LLDPE as an adhesive layer in contact with the fibrous base, ensuring proper adhesion, while HDPE layers provide the water vapour barrier function. This composite approach allows each material to perform its optimal function.
3Adaptability or versatility
If bio-HDPE is used to increase renewable content, then environmental sustainability is improved, but availability and cost-effectiveness deteriorate due to limited supply
Solution Approach 1:
The patent combines bio-HDPE with LLDPE in a multilayer system, allowing the use of renewable bio-HDPE for the water vapour barrier function while LLDPE provides the necessary processing properties. This combination makes the bio-based material more available and cost-effective by blending it with a more readily available polymer.
Solution Approach 2:
The composite packaging material uses bio-HDPE in specific layers where water vapour barrier is critical, while LLDPE is used in layers where processability and availability are more important. This strategic use of composite materials optimizes both sustainability and manufacturing feasibility.
4Quantity of substance
If thin coating layers are used to reduce material weight, then coating layer weight is reduced, but runnability and neck-in control deteriorate in extrusion coating
Solution Approach 1:
The patent combines LLDPE and HDPE in a multilayer system where LLDPE improves runnability and reduces neck-in during extrusion coating. This allows the production of thin coating layers with total weight of 15-25 g/m2 while maintaining good processability and control during manufacturing.
Solution Approach 2:
The composite coating structure uses LLDPE in the inner layer to provide good runnability and reduce neck-in effects during thin layer extrusion, while HDPE provides the water vapour barrier. This composite approach enables successful production of thin coatings that would be difficult to manufacture with pure HDPE.
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 improves adhesion to the fibrous base, reduces coating layer weights, and addresses the neck-in and runnability issues of HDPE, enabling the production of thin, efficient, and renewable-based packaging materials with enhanced performance.
Implementation Method 1
a coextrusion process is developed using a blend of 10-25 wt-% low-density polyethylene (LDPE) and 75-90 wt-% high-density polyethylene (HDPE) as an inner layer, with an outer layer of over 90 wt-% HDPE
Data Source
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, an innermost polymer layer (2) containing a blend of (i) 10 to 25 wt-% of a low-density polyethylene (LDPE) and (ii) 75 to 90 wt-% of a second polyethylene with a higher melt viscosity, said second polyethylene being selected from linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE), and an outer layer (3) of more than 90 wt-% of HDPE. An outermost layer (4) of a polymer blend similar to that used for the innermost layer (2) may be provided for heat-sealing. The layers (2, 3 and 4) may be 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.