Polymeric Powder Coating for Molded Pulp Containers
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Solution Overview
Problem
The challenge lies in applying a polymeric powder coating to molded pulp containers, particularly hollow ones, as the non-conductive nature of the substrate hinders electrostatic attraction, leading to poor adhesion and uneven deposition, and existing methods require separate steps for interior and exterior coating, increasing complexity and cost.
Innovation Solution
A method involving a spraying device that charges the polymeric powder and grounds the main portion of the container, allowing simultaneous deposition on both interior and exterior surfaces of the upper portion, followed by a single heat or irradiation treatment to cure the coating, thereby simplifying the process and ensuring even adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a polymeric powder coating is applied to molded pulp containers using conventional electrostatic deposition, then the coating can be applied to the container surface, but the non-conductive nature of the substrate results in poor adhesion and uneven deposition
Solution Approach 1:
The patent changes the physical state of the container surface from dry to moist by controlling the moisture content of the molded pulp substrate. This parameter change enables electrostatic attraction between the charged polymeric powder and the moist substrate surface, achieving both uniform deposition and reliable adhesion despite the non-conductive nature of the substrate.
2Manufacturing precision
If separate coating steps are used for interior and exterior surfaces of hollow containers, then each surface can be coated, but the process complexity and production time increase
Solution Approach 1:
The patent merges the interior and exterior coating operations into a single simultaneous deposition process. By positioning the container appropriately and using a spraying device that can reach both surfaces, the method applies coating to both interior and exterior surfaces in one operation, reducing process complexity and production time while maintaining comprehensive coverage.
3Reliability
If the entire hollow container is coated, then all surfaces are protected, but the upper portion exposed to moisture and liquid requires additional protection and separate coating steps
Solution Approach 1:
The patent applies different coating strategies to different portions of the container based on their functional requirements. The upper portion, which is exposed to moisture and liquid during use, receives coating treatment as part of the simultaneous deposition process, while the interior surface receives coating for containment protection. This localized approach ensures appropriate protection for each area without requiring separate sequential steps.
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
This method provides a durable and even barrier coating on molded pulp containers, reducing time and costs while ensuring protection against moisture and liquids, with the option to tailor moisture content and humidity for specific applications.
Implementation Method 1
The powder may be charged by corona discharge and then sprayed onto a grounded substrate
Implementation Method 2
The deposition of a powder coating is typically achieved by electrostatic forces
Implementation Method 3
the powder melts and forms a continuous film on the substrate
Implementation Method 4
treating the hollow container with heat or irradiation under conditions that melt and/or cure the polymeric powder
Data Source
Figure 1A
Figure 1B
Figure 2~3B
AI summary
The present disclosure generally relates to a method for providing a barrier coating on a hollow container (100) comprising molded pulp. The method comprises providing a polymeric powder coating onto the interior surface (105a) and at least a portion of the exterior surface of the container (100) prior to curing and/or melting the powder coatings. The present disclosure also relates to a hollow container (100) formed by the method.