Homopolyethylene Terephthalate Extrusion Coating on Paper
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Solution Overview
Problem
Existing laminates with resin coatings on paper bases, such as polyolefins, lack satisfactory heat resistance and aroma barrier properties, limiting their use in food containers, while direct coating of homopolyethylene terephthalate on paper bases is challenging due to instability and high costs of special polyester resins.
Innovation Solution
A heat-sealable laminate is produced by directly coating homopolyethylene terephthalate on a paper base material using an extrusion coating process with specific viscosity and temperature conditions, ensuring uniform film thickness and adhesion without an adhesive layer, and optionally laminating aluminum foil for enhanced properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyolefin is used as coating resin on paper base material, then workability and adhesion are improved, but heat resistance and aroma barrier properties deteriorate
Solution Approach 1:
The invention changes the chemical composition parameter of the coating resin from polyolefin to homopolyethylene terephthalate, which fundamentally alters the material properties to achieve both good workability and superior heat resistance. This parameter change enables the coating to withstand higher temperatures while maintaining manufacturability.
Solution Approach 2:
The invention creates a composite structure by coating homopolyethylene terephthalate on paper base material, combining the properties of both materials. The PET coating layer provides heat resistance and aroma barrier properties while the paper base material maintains structural integrity and workability.
2Temperature
If homopolyethylene terephthalate is directly coated on paper base material, then heat resistance and aroma barrier properties are improved, but film-forming stability deteriorates
Solution Approach 1:
The invention optimizes the melt viscosity parameter of homopolyethylene terephthalate to a specific range (50-200 Pa·s at 280°C) to achieve stable film-forming properties. This parameter control ensures the coating flows properly during extrusion and forms a uniform, stable film on the paper base material without requiring special polyester resins.
Solution Approach 2:
The invention uses general-purpose homopolyethylene terephthalate resin that can be easily acquired, replacing the need for special polyester resins. By optimizing processing parameters, the invention achieves stable film-forming properties with readily available materials, making the process reproducible and commercially viable.
3Stability of the object's composition
If special polyester resin is used to achieve stable film-forming properties, then film-forming stability is improved, but cost and availability deteriorate
Solution Approach 1:
The invention replaces expensive special polyester resins with inexpensive general-purpose homopolyethylene terephthalate resin. By optimizing the melt viscosity parameter, the invention achieves stable film-forming properties with a readily available, cost-effective material, eliminating the need for specialized and expensive resin formulations.
Solution Approach 2:
The invention controls the melt viscosity parameter of homopolyethylene terephthalate within a specific range to achieve stable film-forming properties. This parameter optimization allows the use of general-purpose resins rather than requiring expensive special polyester resins, significantly reducing material costs while maintaining production stability.
4Ease of manufacture
If homopolyethylene terephthalate is coated directly on paper base material, then economy and simplicity are improved, but heat sealability deteriorates
Solution Approach 1:
The invention optimizes the melt viscosity parameter of homopolyethylene terephthalate to a specific range (50-200 Pa·s at 280°C), which enables the coating to achieve proper adhesion and heat sealability. This parameter control ensures the coating forms a uniform film that can be reliably heat-sealed, overcoming the typical poor sealability of directly coated PET on paper.
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 laminate achieves reliable heat sealing at lower temperatures, excellent heat resistance, and effective aroma barrier properties, making it suitable for microwave use and maintaining flavor integrity in food containers, while being economically viable with easily available materials.
Implementation Method 1
a method for producing a laminate, which comprises melt-extruding homopolyethylene terephthalate directly on a paper base material by an extrusion coating process
Implementation Method 2
The laminate achieves reliable heat sealing at lower temperatures
Data Source
AI summary
[Problems to be Solved] To coat homopolyethylene terephthalate, which is inexpensive and easily available, on a paper base material directly, not via an adhesive layer, by extrusion coating, thereby providing a paper laminate having heat sealability and having a homopolyethylene terephthalate coating of a uniform film thickness formed thereon.[Means to Solve the Problems] A method for producing a paper laminate having a coating comprising homopolyethylene terephthalate formed on at least one surface of a paper base material by extrusion coating is characterized in that an air gap L, expressed as a distance from a lip opening of a T-die to a paper base material B, is 25 cm or less.