Recycled Polypropylene Foam Beads for Consistent Expansion
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Solution Overview
Problem
Existing methods for producing expanded beads using recovered polypropylene-based resins result in variation in expansion ratio and reduced closed cell ratio, leading to appearance defects in the molded articles.
Innovation Solution
A production method involving a mixture of polypropylene-based resin A (non-recovered) and resin B (recovered post-consumer material) with specific melting point and blending ratios, along with controlled ash content and melting temperature differences, is used to impregnate and foam the beads under controlled pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If expanded beads are produced using a recovered product of post-consumer material and a polyolefin-based resin material that is a non-recovered material, then the utilization of recovered materials is improved, but variation in the expansion ratio increases and the closed cell ratio is reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the melting point difference between resin A and resin B (10-30°C range) and the blending ratio (resin B content at 5-50 wt%). These parameter optimizations resolve the contradiction by ensuring consistent expansion behavior while maintaining high recovered material utilization.
Solution Approach 2:
The patent uses composite materials by combining two different polypropylene-based resins (resin A and resin B) with distinct melting points into a blended mixture. This composite approach allows the system to leverage the advantages of both resins, achieving both high recovered material content and consistent expansion properties.
2Reliability
If expanded beads are produced using a recovered product of post-consumer material and a polyolefin-based resin material that is a non-recovered material, then the utilization of recovered materials is improved, but the appearance of the expanded beads molded article deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the melting point difference (10-30°C) and ash content (0.1-5 wt%) to ensure uniform expansion and high closed cell ratio. This resolves the appearance quality issue while maintaining high recovered material utilization.
Solution Approach 2:
The patent uses pneumatic principles by introducing a blowing agent that generates gas bubbles during the expansion process. The controlled gas generation, combined with the optimized resin blend, ensures uniform cell structure and high closed cell ratio, thereby improving appearance quality.
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 method produces expanded beads with consistent expansion ratio and high closed cell ratio, resulting in improved appearance of the molded articles while effectively utilizing recycled materials.
Implementation Method 1
impregnating the pellets with a blowing agent
Implementation Method 2
heating and melting again at a heating rate of 10°C/min to the heating end temperature
Data Source
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AI summary
The present invention relates to a method for producing expanded beads using, as a base material resin, a mixture of a polypropylene-based resin A that is a non-recovered material and a polypropylene-based resin B that is a recovered product of a post-consumer material. The present invention provides a method for producing expanded beads, which enables the production of expanded beads in which variation in the expansion ratio and reduction in the closed cell ratio are inhibited, and which is capable of improving the appearance of an expanded beads molded article that is produced by molding the expanded beads. In the method for producing expanded beads, a base material resin, which is a mixture of the polypropylene-based resin A having a melting point of 130°C or higher and 155°C or lower and the polypropylene-based resin B as a recovered product of a post-consumer material is used, in the mixture, the blending rate of the polypropylene-based resin A is 40 wt% or more and 97 wt% or less, and the blending rate of the polypropylene-based resin B is 3 wt% or more and 60 wt% or less (the total of the polypropylene-based resin A and the polypropylene-based resin B is 100 wt%), the melting point difference between the polypropylene-based resin A and the polypropylene-based resin B (the melting point of the polypropylene-based resin B - the melting point of the polypropylene-based resin A) is 10°C or more and 30°C or less, the polypropylene-based resin B has an ash content of 5 wt% or less with respect to 100 wt% of the polypropylene-based resin B, and in a melting peak observed in a DSC curve in heat-flux differential scanning calorimetry of the polypropylene-based resin B, the difference between an extrapolated melting start temperature (Tms) and an extrapolated melting end temperature (Tme) of the melting peak, that is, Tme - Tms is 30°C or more.