Propylene Resin Skin for Foamed Bead Bonding
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Solution Overview
Problem
Conventional skin-covered molded articles of expanded propylene resin beads face issues with lightness in weight and prolonged molding cycle time due to the need for thick skin for strong bonding, which compromises mechanical properties and production efficiency.
Innovation Solution
A skin-covered propylene resin foamed molded article with a skin formed from a propylene resin having specific thermal properties, including a melt tension of 1 to 30 cN at 230°C, allowing for thin skin thickness and improved bonding between the skin and expanded beads, while maintaining mechanical properties and reducing molding cycle time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the skin thickness is increased to improve bonding strength between the skin and expanded beads, then the mechanical properties and bonding strength are improved, but the weight of the molded article increases and the molding cycle time becomes longer
Solution Approach 1:
The invention changes the chemical composition parameters of the propylene resin to achieve optimal bonding strength with thinner skin. Specifically, it controls the propylene content to 90-99 mass% and incorporates specific comonomers (ethylene, propylene, butene, pentene, hexene, or heptene) in controlled amounts (1-10 mass% combined), which modifies the resin's melting point, crystallinity, and adhesion properties to enable strong bonding at reduced skin thickness
Solution Approach 2:
The invention uses composite propylene resin materials combining multiple components: base propylene resin (90-99 mass%), comonomer-containing propylene resin (1-10 mass%), and optionally impact modifiers or coupling agents. This composite approach creates a multi-functional skin material that provides both adequate bonding strength and reduced thickness simultaneously
2Strength
If the skin thickness is increased to improve bonding strength between the skin and expanded beads, then the bonding strength is improved, but the molding cycle time becomes longer
Solution Approach 1:
The invention optimizes resin parameters including melting point (controlled through comonomer content), crystallinity, and molecular weight distribution to achieve rapid bonding at lower skin thickness, thereby reducing the cooling and solidification time required in the molding cycle while maintaining adequate bonding strength
3Strength
If the skin thickness is increased to ensure adequate bonding, then the bonding strength is improved, but the lightness feature of foamed molded articles is adversely affected
Solution Approach 1:
The invention modifies the propylene resin parameters (propylene content 90-99 mass%, specific comonomer composition) to enhance adhesion and bonding strength per unit thickness, allowing the skin to be thinner while maintaining adequate bonding, thus preserving the lightness advantage of foamed molded articles
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 achieves excellent bonding between the skin and expanded beads, enhances the lightness and mechanical properties of the molded article, and ensures high production efficiency with uniform skin thickness, addressing the limitations of conventional methods.
Implementation Method 1
blowing a heating medium such as steam into the hollow molded body to heat and fuse-bond the expanded beads to each other
Implementation Method 2
cooling the resulting molded assembly to obtain the skin-covered molded article of the expanded beads
Data Source
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AI summary
The present invention pertains to a skin-covered foamed molded article (22) of expanded propylene resin beads having excellent lightness in weight, mechanical properties and appearance. The present invention provides a skin-covered foamed molded article (22) of propylene resin expanded beads, with the skin covering substantially the entire surface of the molded article (20) of the expanded beads. The skin, within which the molded article (20) of expanded propylene resin beads is placed, is a propylene resin hollow molded body obtained by blow molding. A base resin of which the skin is formed comprises a propylene resin having a partial heat of fusion in a temperature range between 80 and 140°C of at least 15 J/g and a ratio of the partial heat of fusion to a total heat of fusion (partial heat of fusion/total heat of fusion) of at least 0.2 as measured by heat flux differential scanning calorimetry. The skin has a thickness in the range of 0.3 to 3.5 mm, and the molded article (20) of expanded propylene resin beads has an apparent density in the range of 0.015 to 0.15 g/cm3. The skin is fuse-bonded to the molded article (20) of expanded beads, and the expanded beads from which the molded article (20) is formed are fuse-bonded to each other.