Polypropylene Expanded Beads With Through-Holes for Uniform Black Molding
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Solution Overview
Problem
Existing methods for producing black polypropylene-based resin expanded beads result in reduced blackness and noticeable color unevenness, and increasing carbon black content to improve these issues leads to longer cooling times and decreased productivity.
Innovation Solution
A two-step expanding process is employed to produce polypropylene-based resin expanded beads with a tubular shape and through-holes, using specific bulk ratios and carbon black content to achieve high blackness and reduced color unevenness while maintaining high productivity at lower molding temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the addition amount of carbon black is increased to improve blackness and color unevenness, then blackness and color uniformity are improved, but molding heating temperature must be increased and cooling time becomes longer, which deteriorates productivity
Solution Approach 1:
The invention changes the particle size parameter of the expanded beads to 0.5 mm or smaller, which allows for improved blackness and color uniformity without requiring increased carbon black content or higher molding temperatures. This parameter change enables shorter cooling times and maintains high productivity while achieving the desired visual quality.
Solution Approach 2:
The invention performs preliminary expansion of the polypropylene-based resin particles before molding to create expanded beads with controlled particle size. This preliminary action ensures that the beads achieve optimal blackness and color uniformity in advance, eliminating the need for excessive carbon black addition or prolonged cooling during the molding process.
2Manufacturing precision
If the addition amount of carbon black is increased to improve blackness and color unevenness, then blackness and color uniformity are improved, but molding heating temperature must be increased, which affects fusion-bondability requirements
Solution Approach 1:
The invention changes the particle size parameter of the expanded beads to 0.5 mm or smaller, which improves blackness and color uniformity without requiring increased molding heating temperature. This parameter change maintains optimal fusion-bondability conditions while achieving the desired visual quality.
3Manufacturing precision
If the cooling time is extended to improve blackness and color uniformness, then quality is improved, but productivity deteriorates
Solution Approach 1:
The invention changes the particle size parameter of the expanded beads to 0.5 mm or smaller, which enables achievement of high blackness and color uniformity with significantly reduced cooling time. This parameter change directly addresses the time-quality trade-off by decoupling quality improvement from time extension.
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 beads with high blackness and minimal color unevenness, enabling efficient molding with shorter cooling times and improved moldability, even at lower heating temperatures.
Implementation Method 1
supplying a heating medium to fusion-bond the expanded beads to each other
Implementation Method 2
heated with steam to secondarily expand the expanded beads
Data Source
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AI summary
There is provided a method for producing polypropylene-based resin expanded beads (1) each having a through-hole (11) by performing a first expanding step and a second expanding step. In the first expanding step, tubular resin particles containing carbon black and having through-holes are dispersed in a dispersion medium and released to an environment under a low pressure, thereby obtaining first-step expanded beads having a bulk ratio of M1 times. In the second expanding step, the first-step expanded beads are further expanded to obtain polypropylene-based resin expanded beads having a bulk ratio of M2 times. The bulk ratio M1 is 5 times or more and 25 times or less. A ratio M2/M1 of the bulk ratio M2 to the bulk ratio M1 is 1.2 or more and 3.0 or less.