Void-Containing Polyester Film Melt Viscosity Control
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Solution Overview
Problem
The use of polypropylene resin as a void-generating agent in polyester films faces challenges such as deformation during heat-stretching, reduced void generation, and thermal degradation when compatibilizers like surfactants or polyethylene glycol are added, leading to compromised lightweight, concealing, and thermal dimensional stability properties.
Innovation Solution
Adjusting the melt viscosity and melt viscosity ratio of polyester and polypropylene resins within specific ranges to control the dispersed particle diameter of polypropylene in the polyester resin, eliminating the need for compatibilizers and ensuring voids of optimal size are maintained after heat stretching and setting, while incorporating reclaimed raw materials to maintain film quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If polypropylene resin is used as a void-generating agent with a compatibilizer added to achieve fine dispersion, then lightweight properties and concealing properties are improved, but thermal dimensional stability deteriorates due to deformation during heat-stretching and crushing of voids
Solution Approach 1:
The invention changes the key parameter from particle size (fine dispersion) to void size and void number. By controlling the void number to 10 or more per 10000 μm2 and void area to 10-50 μm2, the patent achieves lightweight properties without requiring fine dispersion that would cause thermal degradation. This parameter shift resolves the contradiction between lightweight properties and thermal dimensional stability
Solution Approach 2:
The invention uses polypropylene resin as a sacrificial void-generating agent that is intentionally designed to be deformed and crushed during heat-stretching to create voids. The resin serves its purpose (generating voids for lightweight properties) and is then discarded in the process, with no need for fine dispersion or compatibilizers that would compromise thermal stability
2Weight of moving object
If polypropylene resin is finely dispersed by adding a compatibilizer, then specific surface area is increased and weight is reduced, but void generation is reduced due to decreased interfacial tension
Solution Approach 1:
Instead of trying to prevent deformation of polypropylene resin during heat-stretching, the invention inverts the approach by intentionally allowing and controlling the deformation to occur. The resin is designed to be deformed into voids of specific size and number, achieving weight reduction through controlled void formation rather than through fine dispersion. This inversion resolves the contradiction between weight reduction and void generation
3Stability of the object's composition
If heat-stretching temperature is lowered to prevent polypropylene resin deformation, then void crushing is reduced, but thermal dimensional stability and film-forming properties deteriorate
Solution Approach 1:
The invention changes the evaluation parameters from void size preservation to void number and void area within acceptable ranges. By setting the void number to 10 or more per 10000 μm2 and void area to 10-50 μm2, the patent allows thermal processing at appropriate temperatures to ensure film-forming properties and thermal dimensional stability, while still achieving sufficient lightweight properties through the specified void characteristics
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 a polyester film with excellent lightweight, concealing, and thermal dimensional stability properties, even when using inexpensive polypropylene resin, and allows for the reuse of reclaimed materials without thermal degradation, enhancing film-forming and whiteness retention.
Implementation Method 1
an incompatible thermoplastic resin (hereinafter referred to as incompatible resin) is first mixed into a matrix made of a polyester resin to obtain a melt of sea-island structure in which the incompatible resin is dispersed in the polyester resin
Implementation Method 2
stretched in at least one axial direction to generate voids by interfacial peeling between the polyester resin and the incompatible resin
Implementation Method 3
light is reflected at the interface between the polyester portion inside the film and the void portion, so that concealing properties and whiteness like paper can be obtained
Data Source
AI summary
A void-containing polyester is disclosed which is excellent in concealing properties, whiteness, and thermal dimensional stability. A void-containing polyester film includes an internal void-containing layer (layer A). The void-containing layer contains a polyester matrix resin and a polypropylene dispersed resin, and satisfies the following requirements (1) to (3), and an apparent density of the film is in a range of 0.8 to 1.2 g/cm3.(1) A melt viscosity (η1) of the polyester resin at a melting temperature of 280° C. and a shear rate of 121.6 sec−1 is 90 to 400 Pa·s(2) A melt viscosity (η2) of the polypropylene resin at a melting temperature of 280° C. and a shear rate of 121.6 sec−1 is 300 to 850 Pa·s(3) A melt viscosity ratio (η2/η1) of the polyester resin and the polypropylene resin at a melting temperature of 280° C. and a shear rate of 121.6 sec−1 is 1.5 to 4.5.