Biaxially Oriented Polyester Film Surface Control for Winding and Adhesion
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Solution Overview
Problem
Existing biaxially oriented polyester films face issues with wrinkling and blocking when wound into film rolls, poor adhesion during secondary processing, and variations in physical properties in the machine direction, particularly when using carbon-neutral polyester resins derived from biomass ethylene glycol, which are not adequately addressed by existing methods.
Innovation Solution
A biaxially oriented polyester film is produced by blending polyester resin chips containing particles with carbon-neutral polyester resin obtained from biomass-derived ethylene glycol, using a specific method of mixing and extruding the chips to minimize static charge and ensure uniform film formation, with controlled surface protrusions and friction coefficients, thereby enhancing transparency and ease of secondary processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a biaxially oriented polyester film is wound into a long film roll, then productivity is improved, but wrinkling and blocking occur
Solution Approach 1:
The invention changes the surface roughness parameter by controlling the number of fine protrusions (0.5-5.0 per 4×10^-12 m²) and arithmetic mean height (Sa: 0.005-0.020 μm) to reduce friction and prevent blocking during winding, while maintaining film strength and integrity
Solution Approach 2:
The invention applies local quality modification by creating specific surface protrusions only where needed for reduced friction, while maintaining the bulk film properties for strength and barrier performance
2Ease of operation
If the surface roughness is controlled to reduce wrinkling, then ease of operation is improved, but adhesion for secondary processing deteriorates
Solution Approach 1:
The invention optimizes the arithmetic mean height Sa to 0.005-0.020 μm, which is sufficiently small to prevent wrinkling during winding but large enough to provide adequate surface area and roughness for adhesion of coating and vapor deposition processes
Solution Approach 2:
The invention uses a moderate level of surface roughness (not overly smooth nor excessively rough) that provides just enough adhesion for secondary processing while being smooth enough to prevent winding defects
3Object-affected harmful factors
If carbon-neutral polyester resin from biomass ethylene glycol is used, then environmental friendliness is improved, but physical property uniformity in machine direction deteriorates
Solution Approach 1:
The invention controls the biomass content parameter to 10-80% by mass and adjusts the number of fine protrusions and surface roughness parameters to compensate for variations in physical properties, achieving uniform film characteristics despite using renewable materials
Solution Approach 2:
The invention uses composite materials by combining carbon-neutral polyester resin with controlled amounts of conventional polyester resin or additives to achieve both environmental benefits and physical property uniformity
Data Source
AI summary
The invention provides a biaxially oriented polyester film, which exhibits excellent transparency, is easily subjected to secondary processing, is an environmentally friendly polyester film, and has little variations in physical properties in the machine direction, and a production method therefor. The biaxially oriented polyester film is formed of a polyester resin composition containing particles and 50% by weight or more of a polyester resin composed of biomass-derived ethylene glycol and fossil fuel-derived dicarboxylic acid units, wherein at least one surface of the biaxially oriented polyester film meets requirements (1) to (3): (1) a number of fine protrusions each having a height of less than 3 nm per area of 4×10−12 m2 is 250-600; (2) a number of fine protrusions each having a height of 3 nm or more per area of 4×10−12 m2 is 300-600; and (3) an arithmetic mean height Sa is 0.010-0.025 μm.