Insulating Coating Composition for Bondable Electrical Steel Sheets
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Solution Overview
Problem
Electrical steel sheets with insulating coatings lack sufficient adhesion strength to anaerobic acrylic adhesives, corrosion resistance, and tension pad resistance, making them unsuitable for forming strong bonds in thinner laminated steel sheets used in automobile motors and electrical equipment.
Innovation Solution
A surface-treatment agent comprising trialkoxysilane and/or dialkoxysilane, silane coupling agent without a polymerizable unsaturated group, plate-like silica, and a polymerizable unsaturated-group-containing compound, applied in specific ratios, forms an insulating coating that enhances adhesion, corrosion resistance, and tension pad resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the thickness of electrical steel sheets is reduced to decrease eddy current loss, then energy efficiency is improved, but adhesion strength to adhesive and bonding reliability deteriorate
Solution Approach 1:
The invention changes the chemical composition parameters of the insulating coating by incorporating specific silane compounds (trialkoxysilane and/or dialkoxysilane with non-reactive substituents), silane coupling agents without polymerizable unsaturated groups, and polymerizable unsaturated-group-containing compounds in controlled ratios. This chemical parameter optimization enables the coating to maintain adequate adhesion strength even on thinner steel sheets, resolving the contradiction between reducing eddy current loss through thinning and maintaining bonding reliability.
Solution Approach 2:
The invention uses a composite insulating coating formulation combining multiple functional components: trialkoxysilane/dialkoxysilane for base coating, silane coupling agents for adhesion promotion, and polymerizable unsaturated-group-containing compounds for crosslinking and mechanical strength. This composite material approach allows the coating to simultaneously provide insulation, adhesion, and mechanical properties necessary for bonding thin electrical steel sheets with anaerobic acrylic adhesives.
2Object-affected harmful factors
If conventional insulating coatings are used without chromium compounds, then corrosion resistance is improved, but adhesion strength to anaerobic acrylic adhesive deteriorates
Solution Approach 1:
The invention optimizes the chemical composition parameters of the insulating coating by specifying precise ratios of silane compounds and silane coupling agents. The coating contains trialkoxysilane and/or dialkoxysilane (A) at 5-50 mass%, silane coupling agent (B) at 1-20 mass%, and polymerizable unsaturated-group-containing compound (D) at 10-40 mass% based on total solid content. This parameter optimization achieves both corrosion resistance without chromium compounds and adequate adhesion strength to anaerobic acrylic adhesives.
Solution Approach 2:
The silane coupling agent (B) without polymerizable unsaturated groups acts as an intermediary between the inorganic silane base coating and the organic polymerizable components, as well as between the insulating coating and the anaerobic acrylic adhesive. This intermediary component facilitates chemical bonding across the interface, enabling both corrosion resistance and adhesion strength to be achieved simultaneously without chromium compounds.
3Reliability
If insulating coating is applied to electrical steel sheets, then electrical insulation is improved, but tension pad resistance deteriorates
Solution Approach 1:
The invention carefully controls the composition parameters of the insulating coating to balance electrical insulation and tension pad resistance. The coating contains trialkoxysilane and/or dialkoxysilane (A) at 5-50 mass%, silane coupling agent (B) at 1-20 mass%, plate-like silica (C) at 1-30 mass%, and polymerizable unsaturated-group-containing compound (D) at 10-40 mass% based on total solid content. This parameter control ensures adequate electrical insulation while maintaining sufficient tension pad resistance for handling during slitting operations.
Solution Approach 2:
The plate-like silica (C) with specific aspect ratio (10-100) and average particle size (0.08-0.9 μm) provides localized mechanical reinforcement and surface properties that improve tension pad resistance in specific areas of the coating, while the overall coating composition maintains electrical insulation properties. This local quality enhancement resolves the contradiction between insulation and handling resistance.
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 electrical steel sheet with the insulating coating exhibits excellent adhesion to anaerobic acrylic adhesives, effective corrosion resistance, and improved tension pad resistance, ensuring strong bonding and durability in automotive and electrical equipment applications.
Implementation Method 1
a silane coupling agent (B) that does not contain a polymerizable unsaturated group in its structure
Implementation Method 2
a polymerizable unsaturated-group-containing compound (D)
Implementation Method 3
formed by applying a surface-treatment agent to at least one surface of the electrical steel sheet and drying the surface-treatment agent
Data Source
AI summary
Disclosed is an electrical steel sheet with an insulating coating formed by applying a surface-treatment agent to at least one surface of the electrical steel sheet and drying the surface-treatment agent, wherein the surface-treatment agent contains: certain trialkoxysilane and/or dialkoxysilane (A); a silane coupling agent (B) that does not contain a polymerizable unsaturated group in its structure; plate-like silica (C); a polymerizable unsaturated-group-containing compound (D); and water, within a range satisfying the following conditions (1) to (3): (1) a mass ratio (A/B) of (A) to (B) is from 0.05 to 1.00; (2) a content of (C) is 2 mass % to 30 mass % with respect to a total mass of (A) to (D) in the surface-treatment agent; and (3) a content of (D) is 2 mass % to 18 mass % with respect to the total mass of (A) to (D) in the surface-treatment agent.