Propylene Resin Bead Composition for Low-Pressure Molding
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Solution Overview
Problem
Expanded propylene resin beads face challenges in in-mold molding due to high molding pressures caused by crystallinity and heat resistance, leading to insufficient secondary expandability and mechanical properties, particularly in achieving surface smoothness and fusion bonding properties.
Innovation Solution
A propylene resin bead composition comprising a core layer of foamed propylene-based resin and a cover layer of olefin-based resin, with specific melting point and flexural modulus ratios, allowing for reduced molding pressures and enhanced secondary expandability and fusion bonding properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If propylene-based resin with high melting point is used to maintain heat resistance and mechanical properties, then heat resistance and strength are improved, but molding pressure increases and secondary expandability deteriorates
Solution Approach 1:
The propylene-based resin is segmented into two distinct components: a high melting point resin (145-165°C) providing heat resistance and mechanical strength, and a low melting point resin (100-145°C) enabling low-pressure molding and good secondary expandability. This segmentation allows each component to fulfill its specific function without compromise
Solution Approach 2:
The invention changes the melting point parameter by combining resins with different melting characteristics. The high melting point resin maintains thermal stability while the low melting point resin reduces molding pressure requirements, achieving a parameter optimization that balances heat resistance with manufacturability
2Strength
If propylene-based resin with high melting point is used to maintain mechanical properties, then strength and rigidity are improved, but fusion bonding properties deteriorate
Solution Approach 1:
The resin system is segmented into high melting point propylene-based resin for mechanical strength and low melting point propylene-based resin for fusion bonding. The low melting point component facilitates better bonding between beads during molding while the high melting point component ensures overall structural integrity
Solution Approach 2:
The invention creates a composite resin system combining two propylene-based resins with different melting points. This composite approach allows the low melting point resin to enhance fusion bonding properties while the high melting point resin maintains mechanical strength, achieving a synergistic effect
3Ease of manufacture
If low melting point propylene-based resin is used to reduce molding pressure, then ease of molding is improved, but heat resistance deteriorates
Solution Approach 1:
The resin system divides functions between two components: low melting point resin (100-145°C) responsible for reducing molding pressure and improving secondary expandability, and high melting point resin (145-165°C) responsible for maintaining heat resistance and mechanical properties
Solution Approach 2:
The invention optimizes the melting point parameter distribution by combining resins with different thermal characteristics. The low melting point component enables easy molding while the high melting point component ensures adequate heat resistance, achieving parameter balance through composition
4Ease of manufacture
If low melting point propylene-based resin is used to improve secondary expandability, then ease of molding is improved, but mechanical properties deteriorate
Solution Approach 1:
The resin system segments functionality between low melting point resin for secondary expandability and high melting point resin for mechanical properties. The low melting point resin allows beads to expand and conform during secondary molding while the high melting point resin provides the necessary structural strength in the final product
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 solution enables in-mold molding at low heating medium pressures with improved surface smoothness and mechanical properties, such as compression strength, in the resulting expanded propylene resin beads molded articles.
Implementation Method 1
the propylene-based resin (a1) having a melting point of 145° C. to 165° C. and a flexural modulus of 1,200 MPa or more and 35% by weight to 2% by weight of a propylene-based resin (a2) having a melting point of 100° C. to 145° C.
Implementation Method 2
a molding pressure of a heating medium, such as steam, etc., is high due to crystallinity or heat resistance of the propylene-based resin
Data Source
AI summary
Provided is an expanded propylene resin bead including a core layer in a foamed state, which includes a propylene-based resin composition (a) satisfying the following (i) and (ii); and a cover layer which includes an olefin-based resin (b) satisfying the following (iii) or (iv):(i) the propylene-based resin composition (a) is a mixture of 65% by weight to 98% by weight of a propylene-based resin (a1) having a melting point of 145° C. to 165° C. and a flexural modulus of 1,200 MPa or more and 35% by weight to 2% by weight of a propylene-based resin (a2) having a melting point of 100° C. to 145° C. and a flexural modulus of 800 MPa to 1,200 MPa;(ii) a difference in a melting point between the resin (a1) and the resin (a2) is 5° C. to 25° C.;(iii) the olefin-based resin (b) is a crystalline olefin-based resin having a melting point (TmB) that is lower than a melting point (TmA) of the composition (a) and being in a relation of (0° C.<[TmA-TmB]≤80° C.); and(iv) the olefin-based resin (b) is a non-crystalline olefin-based resin having a softening point (TsB) that is lower than the TmA and being in a relation of (0° C.<[TmA−TsB]≤100° C.).