Polyester Prepolymer Hot-Water Treatment Fusion Suppression
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Solution Overview
Problem
Current methods for producing polyester resin particles face challenges in suppressing fusion during heat treatments like crystallization or solid-phase polycondensation, leading to reduced productivity and increased energy consumption, while also compromising the solid-phase polycondensation rate and transparency of molded products.
Innovation Solution
A method involving a hot-water treatment followed by specific heat treatment conditions, including stepwise heating and crystallization, to form a surface-crystallized layer with fine spherocrystals, which suppresses fusion and maintains a high polycondensation rate, resulting in transparent and high-molecular-weight PET products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyester prepolymer particles are subjected to conventional crystallization and drying steps before solid-phase polycondensation, then fusion of particles can be suppressed, but the production time increases and productivity decreases
Solution Approach 1:
The invention applies a preliminary hot-water treatment at 100°C or higher before crystallization and drying. This pre-treatment modifies the particle surface properties and internal structure, enabling the particles to resist fusion during subsequent heat treatments. The treatment includes immersing particles in hot water, followed by rapid drying, which creates a protective surface layer that prevents particle bonding during storage and processing.
Solution Approach 2:
The invention changes the temperature parameter significantly by using hot water at 100°C or higher (above the glass transition temperature of PET) for a short duration. This parameter change fundamentally alters the particle surface characteristics and moisture content, creating conditions that prevent fusion during subsequent operations without requiring extended treatment times.
2Reliability
If the crystallization and drying steps are extended to ensure complete suppression of fusion, then particle stability improves, but energy consumption increases
Solution Approach 1:
The hot-water treatment at 100°C or higher serves as a preliminary action that fundamentally changes particle properties before subsequent processing. This pre-treatment reduces the need for extended crystallization and drying times, as the particles are pre-conditioned to resist fusion. The rapid drying phase following hot-water treatment efficiently removes surface water, creating a stable particle surface with reduced energy input compared to conventional extended drying.
Solution Approach 2:
The invention rushes through the water removal process by using rapid drying at elevated temperatures immediately after hot-water treatment. This quick drying step efficiently evaporates surface water before particles can fuse, eliminating the need for prolonged low-energy drying phases while maintaining particle stability.
3Productivity
If high-temperature solid-phase polycondensation is used to increase molecular weight efficiently, then productivity improves, but particle fusion occurs
Solution Approach 1:
The hot-water treatment at 100°C or higher followed by rapid drying serves as a preliminary action that creates fusion-resistant particle surfaces. This pre-treatment modifies the particle surface morphology and reduces surface moisture, enabling subsequent high-temperature solid-phase polycondensation to proceed without particle fusion. The treatment creates a protective surface layer that maintains particle integrity even at elevated polycondensation temperatures.
4Reliability
If conventional drying methods are used to remove surface water, then particle stability improves, but production time increases
Solution Approach 1:
The invention rushes through the drying process by using rapid drying at elevated temperatures (100°C or higher) immediately after hot-water treatment. This rapid drying efficiently evaporates surface water in a short time, preventing hydrolysis and fusion without requiring extended drying periods. The high temperature gradient enables fast moisture removal while maintaining particle stability.
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 method effectively prevents fusion during heat treatments, enhances the transparency of molded products, and improves the productivity and energy efficiency of the polyethylene terephthalate (PET) production process by maintaining a high polycondensation rate and achieving desired molecular weights for various applications.
Implementation Method 1
bringing the polyester prepolymer particles into contact with hot water at a temperature higher than the glass transition temperature of the polyester prepolymer particles
Implementation Method 2
a surface-crystallized layer with fine spherocrystals, which suppresses fusion
Data Source
AI summary
The present invention provides a method for producing a polyester resin, comprising carrying out a hot-water treatment and a heat treatment, in this order, of polyester prepolymer particles obtained by melt polycondensation of a dicarboxylic acid component and a diol component. The hot-water treatment comprises bringing the polyester prepolymer particles with an intrinsic viscosity of from at least 0.10 dL/g to at most 1.0 dL/g and with a density of at most 1.36 g/cm3 into contact with hot water at a temperature higher than the glass transition temperature of the polyester prepolymer particles and less than 100° C., under the condition satisfying the following formula (1):40≦(T−Tg)t≦6000 (1)wherein t is a hot-water treatment time (second), T is the temperature of the hot water (° C.) and Tg is the glass transition temperature (° C.) of the polyester prepolymer particles.