Expanded Polyolefin Resin Particles Process
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Solution Overview
Problem
Conventional processes for producing expanded polyolefin resin particles often result in nonuniform cell diameters and expansion ratios, leading to poor fusibility, surface properties, and dimensional accuracy in in-mold expanded molded products, with environmental and cost concerns associated with volatile organic foaming agents and limited expansion capabilities with inorganic gases.
Innovation Solution
A process involving the use of water and carbon dioxide as foaming agents, with polyolefin resin compositions containing polyvalent alcohols and foam nucleating agents, to produce expanded polyolefin resin particles with controlled cell diameter and expansion ratio, achieving uniform cells and improved product properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If volatile organic foaming agents (propane, butane) are used, then high expansion ratio is achieved, but control of expansion ratio and crystal condition becomes difficult and facility costs increase due to explosion-proof requirements
Solution Approach 1:
The invention changes the fundamental parameter of foaming agent type from volatile organic compounds to inorganic gases (CO2, N2, air). This parameter change fundamentally alters the expansion mechanism, enabling precise control through pressure and temperature parameters rather than relying on the plasticizing effect of organic agents, thus resolving the contradiction between achieving expansion and maintaining control precision
Solution Approach 2:
The invention replaces expensive explosion-proof facilities and safety infrastructure with inexpensive inorganic gas foaming agents that pose no explosion hazard. This substitution eliminates the need for costly explosion-proof equipment while maintaining effective expansion, addressing the facility cost issue
2Object-affected harmful factors
If inorganic gases (nitrogen, air) are used as foaming agents, then safety and environmental issues are resolved, but sufficient impregnation and high expansion are not achieved due to low capacity to spread through polyolefin resin
Solution Approach 1:
The invention introduces water as an intermediary substance that facilitates the impregnation of inorganic gases into the polyolefin resin. Water acts as a carrier medium that enhances the penetration capability of inorganic gases through the resin matrix, enabling sufficient impregnation and subsequent high expansion while maintaining the safety and environmental benefits of inorganic gases
Solution Approach 2:
The invention creates a composite foaming system combining inorganic gases (CO2, N2, or air) with water as a dual-phase foaming agent. This composite approach leverages the safety of inorganic gases while utilizing water's superior impregnation capability, achieving both high expansion and environmental safety simultaneously
3Object-affected harmful factors
If water is used as a foaming agent, then environmental friendliness and cost-effectiveness are achieved, but the resulting expanded particles have extremely small cell diameters and high open cell ratios, leading to poor fusibility, surface appearance, and mechanical properties
Solution Approach 1:
The invention optimizes the physical parameters of the water-based foaming process, specifically controlling temperature and pressure conditions during impregnation and expansion. By adjusting these parameters, the cell diameter and open cell ratio are precisely controlled to produce expanded particles with uniform, larger cells that maintain good fusibility, surface appearance, and mechanical properties while preserving environmental benefits
4Volume of moving object
If amount of water-soluble inorganic substance is increased to achieve higher expansion ratio, then expansion ratio increases, but cell diameter becomes extremely small and fusibility between expanded particles deteriorates
Solution Approach 1:
The invention changes the approach to controlling expansion by adjusting process parameters (temperature, pressure, impregnation time) rather than increasing the amount of water-soluble inorganic substance. This parameter-based control mechanism achieves high expansion ratios while maintaining appropriate cell diameters and fusibility, avoiding the detrimental effect of excessive inorganic additive
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 process enables the production of expanded polyolefin resin particles with high expansion ratios and uniform cell diameters, resulting in in-mold expanded molded products with enhanced fusibility, surface quality, and dimensional accuracy, while reducing environmental impact and production costs.
Implementation Method 1
impregnating the resin particles with the foaming agent at a constant pressure and constant temperature
Implementation Method 2
a process for producing expanded polyolefin resin particles with use as a foaming agent of water contained in an aqueous dispersion medium
Implementation Method 3
releasing them into a low-pressure atmosphere
Implementation Method 4
heating the polyolefin resin particles up to or above a softening temperature of the polyolefin resin particles
Data Source
Figure 1~2
AI summary
Provided is a process for producing expanded polyolefin resin particles whose cells are not made nonuniform or extremely smaller as seen in conventional expanded particles, whose cell diameter and expansion ratio can be easily controlled independently, and which, when subjected to in-mold expansion molding, give in-mold expanded molded products satisfactory in fusibility and excellent in surface properties. The process is a process for producing expanded polyolefin resin particles by: dispersing polyolefin resin particles together with an aqueous dispersion medium into a closed vessel; heating the polyolefin resin particles up to or above a softening temperature of the polyolefin resin particles; and releasing the polyolefin resin particles into a zone whose pressure is lower than an internal pressure of the closed vessel, with use as a foaming agent of water serving as the dispersion medium, the polyolefin resin particles being composed of a polyolefin resin composition including: polyolefin resin; a substance selected from among polyethylene glycol, polyvalent alcohol having a carbon number of not less than 3 to not more than 6, and a water-absorbing substance having no function of forming foaming nuclei; and a foam nucleating agent.