360° In-Mold Coating for Plastic Insert Encapsulation
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Solution Overview
Problem
Existing in-mold coating processes fail to effectively surround or encapsulate molded plastic parts, requiring excessive coating materials and being limited to liquid coatings that solidify upon removal, and often necessitate additional adhesives or structures for part assembly.
Innovation Solution
A process involving a 360° coating application around an assembly of two plastic molded parts, using a curable composition comprising isocyanate-reactive and polyisocyanate components, which flows and cures to encapsulate the parts without additional adhesives or structures, utilizing notches for fit and internal mold release agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a multi-cavity metal mold is used to form a plastic part in one cavity and introduce it into a second cavity for coating, then the coating can be applied to the part surface, but the process does not surround or encapsulate the molded plastic part
Solution Approach 1:
The mold is divided into multiple cavities: a first cavity for forming the plastic part and a second cavity for applying the coating. This segmentation allows the plastic part to be formed and then positioned in the coating cavity where the coating is injected to surround and encapsulate the part completely.
Solution Approach 2:
The plastic part formed in the first cavity is nested into the second cavity, which is designed to receive and surround the part. The coating is then injected into the space between the part and the mold cavity wall, creating a nested structure where the coating encapsulates the part.
2Ease of manufacture
If the part is submerged in liquid coating material, then the part can be coated, but considerably more coating materials are required than actually applied on the part
Solution Approach 1:
The coating application process extracts only the necessary amount of coating material by injecting it directly into the mold cavity where it will be applied precisely to the part surface. This eliminates the need for excessive coating material that would be required for submersion methods.
Solution Approach 2:
The plastic part is positioned in the mold cavity before the coating is injected. This preliminary positioning ensures that the coating material flows precisely around the part in the correct locations, preventing material waste and ensuring complete encapsulation.
3Adaptability or versatility
If liquid coating is used that solidifies when removed from submersion pool, then coating can be applied, but the process is limited to certain coatings and requires removal from pool
Solution Approach 1:
The mold cavity acts as an intermediary that allows the coating material to remain in a liquid state during application and then solidify in place. The cavity provides the necessary confinement and environment for the coating to cure without requiring removal from a pool, enabling greater versatility in coating types.
4Reliability
If additional adhesives or structures are used to hold parts together, then part assembly can be secured, but the encapsulation structure becomes more complex
Solution Approach 1:
The coating serves dual functions: it encapsulates the plastic part and simultaneously acts as an adhesive to hold the part assembly together. By merging these two functions into a single material and process step, the structure remains simple while maintaining reliability without requiring separate adhesives or structures.
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
Achieves efficient use of coating materials, minimizes waste, and ensures secure part assembly through a continuous, 360° coating that binds parts together, while allowing for varied surface coverage and reduced material usage.
Implementation Method 1
The addition reaction of the polyisocyanate with the isocyanate-reactive component, which can occur at ambient conditions, produces crosslinked polyurethane networks that form coating films
Implementation Method 2
the coating flows in a gap located between the outside surface of the assembly and the cavity, and wherein the coating flows 360° around the outside surface of the assembly
Data Source
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AI summary
An in-mold encapsulation and processes for its manufacture are disclosed, comprising two or more plastic molded parts and a coating, such that when the encapsulation is rotated 360° about an axis, the coating may be seen as applied to a portion of the outside surface of the molded parts at any degree about that axis. In embodiments, the molded parts comprise polycarbonate, and the coating composition comprises isocyanate reactive groups and a polyisocyanate. The encapsulation may comprise areas where the coating is not applied, even though only the coating and not any other adhesive or structure holds the plastic molded parts together.