Infrared Heating for Uniform Hollow Microsphere Formation in Leather Coating
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Solution Overview
Problem
Existing methods for forming a base coating on leather, particularly cowhide, using hollow microspheres are inadequate as they often result in shrinking, hardening, and uneven surfaces, which damage the grain structure and require sanding, and fail to effectively fill imperfections without compromising the leather's quality.
Innovation Solution
The use of infrared radiation with a wavelength between 0.7 μm and 10 μm to heat a solidified plastic dispersion containing compact particles, ensuring uniform heating and formation of hollow microspheres throughout the leather, including deeper areas, without causing significant shrinkage or hardening, using a device with an infrared radiator positioned to emit radiation directly onto the solidified dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If hot air is used to supply heat to form hollow microspheres, then hollow microspheres form quickly on the surface, but they form a heat-insulating layer that prevents heat from penetrating to deeper zones
Solution Approach 1:
The patent replaces the conventional hot air heating method with infrared radiation heating. Instead of using convective heat transfer through hot air that creates surface insulation, infrared radiation directly penetrates the plastic dispersion to heat compact particles throughout the coating layer, enabling uniform hollow microsphere formation from surface to depth without the heat-insulating barrier problem.
Solution Approach 2:
The patent changes the heating parameter from convective hot air temperature to infrared radiation wavelength and intensity. By using infrared radiation with specific wavelengths that can penetrate the plastic dispersion, the heating process achieves deeper penetration while maintaining controlled formation speed of hollow microspheres, resolving the contradiction between surface formation speed and deep heat penetration.
2Temperature
If the temperature of hot air is increased to improve heat penetration, then deeper zones can be heated, but hollow microspheres already formed on the surface are destroyed and the leather hardens and shrinks
Solution Approach 1:
The patent replaces hot air convection heating with infrared radiation heating. This substitution allows deep heat penetration without the need to increase air temperature to damaging levels. The infrared radiation directly heats the plastic dispersion and compact particles throughout the coating, achieving uniform hollow microsphere formation without destroying surface microspheres or causing leather hardening and shrinking.
Solution Approach 2:
The patent uses infrared radiation as an intermediary heating medium that can penetrate the plastic dispersion without requiring high ambient temperatures. This intermediary approach allows heat to reach deeper zones while maintaining a controlled thermal environment that prevents damage to the leather substrate and already-formed hollow microspheres.
3Manufacturing precision
If pressure and heat are applied to form hollow microspheres from compact particles, then hollow microspheres are formed, but the leather is adversely affected and hardens
Solution Approach 1:
The patent replaces the conventional method of using high pressure and heat to form hollow microspheres with infrared radiation heating. This substitution eliminates the need for high pressure application, allowing hollow microspheres to form through uniform heating of compact particles throughout the plastic dispersion without compressing or hardening the leather substrate.
Solution Approach 2:
The patent changes the heating parameters by using infrared radiation with controlled wavelength and intensity distribution. This allows the compact particles to be heated uniformly throughout the coating layer, enabling hollow microsphere formation at lower overall temperatures and without the high pressure conditions that cause leather hardening and loss of flexibility.
4Shape
If the grain layer is sanded down to achieve a flat surface, then the surface becomes flat, but the quality of the leather is affected and its value is greatly reduced
Solution Approach 1:
The patent applies preliminary action by using infrared radiation to uniformly heat the plastic dispersion containing compact particles before the coating fully solidifies. This causes hollow microspheres to form throughout the coating layer, including in depression areas, creating a uniformly expanded foam structure that fills surface imperfections. The result is a flat, even surface without the need for subsequent sanding that would damage the leather grain and reduce its value.
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 produces a leather with a nubuck-like, indentation-free surface and closed pores, maintaining the leather's natural strength and quality, allowing for a firm bond with subsequent finishes and reducing loose grain, enabling a smooth finishing process without reworking the grain structure.
Implementation Method 1
an infrared radiator with a radiation surface directed against the solidified plastic dispersion and emitting infrared rays with a wavelength of between 0.7 μm and 10 μm
Implementation Method 2
exposing the solidified plastic dispersion containing the compact particles to infrared radiation with a wavelength between 0.7 μm and 100 μm
Implementation Method 3
from the compact particles by supplying heat Hollow microspheres are formed
Implementation Method 4
the hollow microspheres are formed by applying pressure and heat at a temperature of at least 100°C
Data Source
Figure 1~2
AI summary
The invention relates to a method for application of a coating, preferably a base coating on the grain side of a leather, in particular, a cowhide, wherein an aqueous plastic dispersion (4), comprising compact particles containing a propellant, is applied to said grain side and allowed to adhere and microscopic hollow protuberances (7) are formed from the compact particles by introduction of heat. According to the invention, the adhered plastic dispersion (4) comprising the compact particles is subjected to an infrared radiation with a wavelength of between 0.7 µm and 100 µm.