Ceramic Green Sheet Urethane Binder Shrinkage Control
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Solution Overview
Problem
Ceramic green sheets exhibit high heat shrinkage, making it difficult to achieve high positioning accuracy in processes like printing and stacking, and they lack satisfactory plasticity, punching property, and sinterability, which are essential for subsequent mechanical working and firing.
Innovation Solution
A ceramic green sheet is produced using a specific urethane resin formed by mixing isocyanate and polyol, with a controlled functional-group ratio and molecular weight, and a controlled ratio of urethane resin to ceramic powder, which suppresses heat shrinkage and enhances punching property while maintaining plasticity and sinterability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional organic binders are used in ceramic green sheets, then the sheets can be formed and processed, but they exhibit large percent heat shrinkage making positioning accuracy difficult to obtain
Solution Approach 1:
The patent changes the chemical composition parameters of the organic binder by using a specific urethane resin with controlled molecular weight (290-988) and functional group ratio (polyol to isocyanate mole ratio of 1.5/11.5 to 11.5/11.5). These parameter changes result in reduced heat shrinkage while maintaining positioning accuracy during processing.
Solution Approach 2:
The patent employs a composite organic binder system consisting of urethane resin formed from specific combinations of polyol and isocyanate. This composite material approach creates a binder that simultaneously provides structural integrity and minimizes heat shrinkage, resolving the contradiction between positioning accuracy and shape stability.
2Productivity
If ceramic green sheets are heated to evaporate solvent, then the sheets can be dried and processed, but the intermolecular distances between binder molecules decrease causing easy heat shrinkage
Solution Approach 1:
The patent modifies the molecular parameters of the binder by selecting specific molecular weight ranges (290-988) and functional group ratios. These changes create a binder structure that maintains adequate intermolecular distances even during solvent evaporation, allowing efficient drying without excessive heat shrinkage.
Solution Approach 2:
The urethane resin acts as an intermediary material between the ceramic powder particles and the solvent evaporation process. It provides a stable molecular structure that mediates the transition from wet to dry state, preventing direct contraction of the ceramic matrix during drying.
3Shape
If crosslinking occurs between urethane resin molecules to suppress shrinkage, then heat shrinkage is reduced, but plasticity and punching property are compromised
Solution Approach 1:
The patent precisely controls the functional group ratio (polyol to isocyanate mole ratio of 1.5/11.5 to 11.5/11.5) and molecular weight parameters to achieve optimal crosslinking density. This controlled parameter adjustment allows sufficient crosslinking to suppress shrinkage while maintaining enough chain mobility for plasticity and punching performance.
Solution Approach 2:
The patent creates local variations in crosslinking density through controlled functional group ratios. The binder structure provides strong crosslinked regions for shrinkage suppression while maintaining more flexible regions for plasticity, achieving spatially differentiated properties within the binder network.
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 use of urethane resin as a binder in ceramic green sheets reduces heat shrinkage, improves punching property, and maintains satisfactory plasticity and sinterability, facilitating subsequent processing steps like mechanical working and firing.
Implementation Method 1
a urethane resin (polyurethane) produced by mixing an isocyanate and a polyol... formed through reaction between the isocyanate and the polyol
Implementation Method 2
The thin molded product is dried to evaporate the solvent, thereby producing a thin ceramic green sheet
Implementation Method 3
With the progress of gelling, crosslinking can occur between adjacent molecules of the urethane resin, so that the urethane groups contained in adjacent molecules of the urethane resin are linked
Data Source
AI summary
The invention provides a ceramic green sheet having plasticity, punching property, and sinterability of satisfactory levels as well as a low percent (heat) shrinkage. In the production of a ceramic slurry serving as a raw material of the sheet, ingredients thereof are mixed under such conditions that the functional group ratio (polyol to isocyanate) is 1.5/11.5 to 11.5/11.5; the urethane resin formed from isocyanate and polyol has a repeating-unit-based molecular weight of 290 to 988; and the ratio by weight of the urethane resin to a ceramic powder falls within a range of 4.5 to 10 parts by weight of the urethane resin with respect to 100 parts by weight of the ceramic powder. A ceramic green sheet having, in well balance, all of the properties (i.e., plasticity, punching property, sinterability, and (heat) shrinkage) required for facilitating subsequent processes such as mechanical working and firing can be provided.