Moisture-Curable Hot Melt Urethane Foaming for Uniform Thin Films
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Solution Overview
Problem
Existing methods for foaming and curing moisture-curable hot melt urethane compositions face challenges in achieving a uniform and reproducible foamed state, especially in thin films, and require the use of solvents like DMF, which are regulated and can damage substrates due to high heating temperatures and poor texture issues with solid thermally expandable particles.
Innovation Solution
A solvent-free moisture-curable hot melt urethane composition using a foaming agent composition containing N,N'-dinitrosopentamethylenetetramine, urea, and a polyol, with boric acid, which undergoes thermal decomposition to form bubbles that are immobilized by reacting with isocyanate groups, maintaining an excellent foamed state even in thin films without deteriorating mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If water foaming method is used to produce foamed and cured product, then carbon dioxide bubbles are generated through reaction with isocyanate groups, but the foaming degree varies depending on mixed state and it is difficult to achieve uniform foamed state with high reproducibility, especially in thin films
Solution Approach 1:
The patent changes the chemical parameters of the foaming system by replacing water with organic peroxide initiators and azo compounds. This parameter change transforms the foaming mechanism from water-isocyanate reaction to thermal decomposition of peroxides and azo compounds, enabling controlled and uniform bubble generation throughout the composition without dependence on mixing state, thereby achieving consistent foamed state in thin films with high reproducibility
Solution Approach 2:
The patent substitutes the chemical reaction mechanism (water-isocyanate reaction) with a thermal decomposition mechanism. By using organic peroxides and azo compounds that decompose upon heating to release nitrogen gas, the system replaces the unpredictable water-based foaming with a controllable thermal process, eliminating the need for vigorous stirring and achieving uniform foaming in thin films
2Quantity of substance
If water or steam is used for foaming, then carbon dioxide is produced as bubbles, but carbon dioxide escapes from thin films and only bubbles from vigorous stirring remain
Solution Approach 1:
The patent changes the physical and chemical parameters by using organic peroxides and azo compounds instead of water. These compounds decompose at controlled temperatures to release nitrogen gas uniformly throughout the composition. The gas bubbles form consistently during heating without escaping, maintaining the desired foamed state in thin films without relying on mechanical stirring
Solution Approach 2:
The patent introduces organic peroxides and azo compounds as intermediary substances that mediate the foaming process. These intermediaries decompose upon heating to generate nitrogen gas uniformly distributed throughout the composition, serving as a reliable bubble source that prevents carbon dioxide escape and maintains stable foamed structure in thin films
3Ease of manufacture
If DMF solution of polyurethane is used for intermediate layer, then foamed layer can be formed by wet processing, but DMF is regulated and needs to be reduced or eliminated
Solution Approach 1:
The patent extracts and eliminates the harmful solvent DMF from the system. By using a solvent-free moisture-curable hot melt urethane composition with organic peroxide and azo compound foaming agents, the invention removes DMF entirely while maintaining the ability to form foamed intermediate layers through thermal decomposition and nitrogen gas generation, complying with environmental regulations
Solution Approach 2:
The patent changes the formulation parameters by transitioning from DMF-based solutions to a solvent-free hot melt system. The moisture-curable urethane composition with peroxide and azo compound initiators enables foaming without any organic solvent, eliminating DMF's harmful effects while preserving manufacturing capabilities through controlled thermal decomposition
4Productivity
If thermally expandable fine particles are used for foaming, then heating and foaming can occur, but the particles remain solid and hard after heating, resulting in poor texture
Solution Approach 1:
The patent changes the physical state and chemical composition of the foaming agents by using organic peroxides and azo compounds instead of solid thermally expandable particles. These chemical initiators decompose upon heating to release nitrogen gas uniformly, creating soft and flexible foam structures rather than hard particles, thereby improving texture while maintaining foaming efficiency
Solution Approach 2:
The patent substitutes solid thermally expandable particles with chemical foaming agents (organic peroxides and azo compounds). Instead of relying on mechanical expansion of solid particles, the system uses chemical decomposition to generate nitrogen gas uniformly throughout the composition, resulting in a homogeneous foamed structure with excellent texture and flexibility
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 achieves a stable and reproducible foamed state with excellent texture in thin films, eliminates the need for solvents like DMF, and prevents substrate damage by using a heat-decomposable foaming agent that maintains mechanical properties and promotes foaming without water influence.
Implementation Method 1
A solvent-free moisture-curable hot melt urethane composition using a foaming agent composition containing N,N'-dinitrosopentamethylenetetramine, urea, and a polyol, with boric acid, which undergoes thermal decomposition to form bubbles
Implementation Method 2
bubbles that are immobilized by reacting with isocyanate groups
Implementation Method 3
water or steam reacts with the isocyanate groups in a moisture-curable hot melt urethane to produce carbon dioxide
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The present invention provides a moisture-curable hot melt urethane composition, including a hot melt urethane prepolymer (A) having an isocyanate group and a foaming agent composition (B) containing N,N'-dinitrosopentamethylenetetramine (b1), urea (b2) and a polyol (b3). The present invention also provides a method for producing a foamed and cured product of a moisture-curable hot melt composition, which includes heat-melting a hot melt urethane prepolymer (A), then mixing the foaming agent composition (B) therewith, applying the resultant mixture to a substrate, and performing a heating treatment at a temperature equal to or higher than heat-melting temperature of the (A) to thereby cause foaming and curing. An object of the present invention is to provide a solvent-free foaming system, according to which a foamed and cured product with excellent texture can be obtained, and an excellent foamed state can be maintained even in a thin film.