PET Heat-Resistant Containers Using Fine Crystal Nucleators
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current materials for food containers fail to simultaneously achieve high heat resistance and transparency, as high transparency materials lack heat resistance and vice versa, and existing methods for enhancing crystallinity in PET containers are limited by the size of crystal nucleators and the complexity of uniaxial stretching processes.
Innovation Solution
The method involves producing organic acid metal salt particulates through a chemical reaction between an inorganic basic material or carbonate and an organic acid, which are then used as crystal nucleators in the PET resin to create a heat-resistant and transparent container by controlling crystallinity through a specific molding process, including a masterbatch-making and molding sheet-making process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If A-PET sheet or OPS is used for high transparency, then transparency is improved, but heat resistance deteriorates as these sheets are softened at about 80°C
Solution Approach 1:
The invention changes the crystallinity parameter of PET resin from low (amorphous) to high (30-60%) through controlled crystallization using organic acid metal salt nucleators. This parameter change enables the material to maintain both high transparency and heat resistance, as the crystalline structure provides thermal stability while controlled crystal size maintains optical clarity.
Solution Approach 2:
The invention creates a composite system by incorporating organic acid metal salt particles (sodium benzoate, calcium benzoate, etc.) as nucleating agents within the PET resin matrix. This composite approach enables simultaneous achievement of transparency and heat resistance by controlling crystal nucleation and growth, allowing the material to resist softening at high temperatures while maintaining optical properties.
2Temperature
If PP sheet is used for high heat resistance, then heat resistance is improved, but transparency deteriorates
Solution Approach 1:
The invention changes the crystallinity parameter of PET resin to 30-60% through controlled crystallization, achieving heat resistance comparable to PP while maintaining transparency. The controlled crystal size and distribution allow light transmission while the crystalline structure provides thermal stability up to 150°C.
3Temperature
If uniaxially stretched PET film is heat-set at 220°C to achieve high heat resistance and transparency, then heat resistance and transparency are improved, but the film cannot be elongated by heating and cannot be formed into container shapes
Solution Approach 1:
The invention performs preliminary uniaxial stretching at 90-120°C to create oriented molecular structure and initiate crystal nucleation, then applies a mild heat-setting at 100-200°C to develop crystallinity to 30-60%. This preliminary crystallization creates a structure that maintains heat resistance while retaining sufficient chain mobility for subsequent forming operations, unlike conventional full heat-setting at 220°C which locks the structure completely.
Solution Approach 2:
The invention optimizes the crystallinity parameter to 30-60% (rather than maximum crystallinity) and controls crystal size to maintain a balance between heat resistance and formability. The moderate crystallinity level provides thermal stability while leaving enough amorphous regions for the material to be formed into container shapes through heat forming.
4Manufacturing precision
If conventional solid nucleators are pulverized to reduce size, then nucleation effectiveness is improved, but the minimum average size remains about 10 μm which is too large for fine crystal formation
Solution Approach 1:
The invention replaces the mechanical pulverization system with a chemical reaction system. Instead of mechanically grinding nucleators to reduce size, the invention uses inorganic basic materials or carbonates to react with organic acids, producing organic acid metal salt particulates with molecular-level dimensions (0.1-10 μm). This chemical approach naturally produces ultra-fine particles without the limitations of mechanical size reduction.
Solution Approach 2:
The invention creates a composite approach by combining inorganic basic materials (calcium carbonate, magnesium oxide, etc.) with organic acids (benzoic acid, phthalic acid, etc.) to produce organic acid metal salt nucleators. This composite chemical reaction produces ultra-fine particulates with controlled size and distribution, achieving superior nucleation effectiveness compared to conventional pulverized nucleators.
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 allows for the production of containers with crystallinity of 18% or more, achieving both high heat resistance and transparency by growing fine crystals that are effective as crystal nucleators, thereby overcoming the limitations of existing materials and processes.
Implementation Method 1
utilizing an organic acid metal salt produced by allowing to react an inorganic basic material or carbonate with an organic acid, as a crystal nucleator of PET resin
Implementation Method 2
produced by allowing to react an inorganic basic material or carbonate with an organic acid
Data Source
Figure 1~2
Figure 3
AI summary
[Problem] Upon manufacturing a heat-resistant container using PET sheet, high heat-resistance is made sure without stretching operation. [Solving Means] The method comprises a molding sheet-making process, wherein a sheet is made including organic acid metal salt particulates produced by allowing to react an inorganic basic material or carbonate being solid at ordinary temperature with an organic acid being solid at ordinary temperature in the equivalent relationship, and a container-molding process, wherein, the molding sheet made in the molding sheet-making process is heated to 80- 130°C, formed into a container shape by a vacuum or vacuum-pressure forming machine using a mold, and heat-set by keeping at 130-220°C in the same mold, and the container formed in the container-molding process has a crystallinity of 18 % or more represented by the following formula.