Metal Bottle Can Mouth Coating to Prevent Threading Cracks
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Solution Overview
Problem
The existing methods for producing metallic bottle cans face challenges in preventing the cracking or peeling of the finishing varnish layer on the outer surface of the mouth portion during the threading work, which can lead to increased production costs due to the need for additional coating and baking steps.
Innovation Solution
A metallic bottle can with a finishing varnish layer directly applied to the outer surface of the mouth portion, using a mixed resin matrix of polyester, epoxy, and amino resins, with an MEK extractability of 2 to 8% by mass, is produced through primary and secondary baking steps, eliminating the need for a size coating and reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a size coating is applied to improve adhesion of the finishing varnish layer, then the finishing varnish layer adhesion is improved, but the production cost increases due to additional coating and baking steps
Solution Approach 1:
The invention extracts and eliminates the size coating layer from the traditional multi-layer coating system. By formulating a finishing varnish layer with specific resin compositions (polyester resin, epoxy resin, and amino resin in specific ratios) and controlling its drying oil content and baking conditions, the patent achieves adequate adhesion without requiring the separate size coating layer, thereby reducing production steps and costs
Solution Approach 2:
The invention changes the chemical composition parameters of the finishing varnish layer by specifying particular resin ratios (polyester resin 20-60 parts, epoxy resin 10-40 parts, amino resin 5-30 parts) and controlling the drying oil content (5-20 parts based on total resin). These parameter changes enable the finishing varnish layer to achieve both adhesion and crack resistance without additional size coating
2Reliability
If the finishing varnish layer is baked to high cure level to prevent blocking with cap film, then blocking prevention is improved, but the finishing varnish layer becomes brittle and cracks during threading work
Solution Approach 1:
The invention changes the baking parameters to achieve optimal cure level. By controlling the baking temperature (100-150°C) and time, and by formulating the resin composition with specific ratios of flexible polyester resin and rigid epoxy resin along with controlled drying oil content (5-20 parts), the patent achieves sufficient curing to prevent blocking while maintaining flexibility to prevent cracking during threading
Solution Approach 2:
The invention uses a composite resin system combining polyester resin, epoxy resin, and amino resin in specific ratios. This composite material formulation provides a balance between flexibility (from polyester resin) and rigidity (from epoxy and amino resins), enabling the finishing varnish layer to resist both blocking and cracking under different service conditions
3Strength
If the finishing varnish layer is kept flexible to prevent cracking during threading, then crack resistance is improved, but blocking occurs between the cap film and finishing varnish layer
Solution Approach 1:
The patent employs a composite resin system where polyester resin (20-60 parts) provides flexibility and crack resistance, while epoxy resin (10-40 parts) and amino resin (5-30 parts) provide rigidity and cross-linking density. This composite formulation achieves the optimal balance between flexibility and curing level to simultaneously prevent both cracking and blocking
Solution Approach 2:
The invention controls the drying oil content parameter (5-20 parts based on total resin) and the resin ratio parameters to achieve the desired balance. The controlled drying oil content provides sufficient flexibility while the specific resin ratios ensure adequate cross-linking density to prevent blocking, resolving the contradiction between flexibility and cure level
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 effectively suppresses cracking and peeling of the finishing varnish layer while ensuring excellent adhesion and cap openability, reducing cap-opening torque and avoiding the need for additional coating and baking steps, thus lowering production costs and maintaining the strength of the base material.
Implementation Method 1
applying a coating material to which an anti-blocking agent has been added, subjecting the formed body to the necking and threading in a state where the coating on the outer surface thereof has been cured to a gel fraction of 80 to 96%
Implementation Method 2
the coating material for forming a finishing varnish layer has a gel fraction of 80 to 96%
Data Source
AI summary
A metallic bottle can including a metallic base material of the bottle shape that has a mouth portion having a threaded portion, a shoulder portion, a body portion and a bottom portion, wherein, on the outer surface of said mouth portion, a finishing varnish layer is provided directly on said metallic base material, and said finishing varnish layer has an MEK extractability of 2 to 8% by mass.