Oxidative Liming Process for Metal-Free Leather Production
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Solution Overview
Problem
Traditional tanning processes rely on environmentally harmful materials like heavy metals and sulfides, and existing alternatives often do not integrate well into the entire tanning process, failing to produce a 'metal-free' product with biocompatible disposal properties.
Innovation Solution
A tanning process incorporating oxidative liming with hydrated lime and hydrogen peroxide, adjusted with caustic soda, which allows for the recovery and reuse of liming waste, reducing heavy metal usage and CO2 emissions, and featuring sequential eco-friendly steps to produce a biocompatible leather product.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional heavy metal tanning and sulfide liming are used, then tanning effectiveness is achieved, but environmental pollution and harmful by-products are generated
Solution Approach 1:
The patent changes the chemical parameters of the liming process by using hydrogen peroxide instead of sulfides and adjusting pH with caustic soda to achieve effective hair removal without generating harmful sulfide by-products. The oxidative liming process maintains effectiveness while improving environmental compatibility
Solution Approach 2:
The patent uses readily available chemicals like hydrogen peroxide, hydrated lime, and caustic soda that can be easily disposed of or neutralized, replacing persistent heavy metals and sulfides that require complex waste treatment and disposal systems
2Adaptability or versatility
If hydrogen peroxide liming is used to avoid sulfides, then by-product reusability improves, but integration into the complete tanning process is limited
Solution Approach 1:
The oxidative liming process serves multiple functions: it removes hair effectively, generates reusable by-products free from sulfide contamination, and integrates seamlessly with subsequent tanning steps. The process is designed to be universally applicable across different tanning workflows
Solution Approach 2:
The patent uses an intermediary washing step between liming and tanning that facilitates the transition and allows by-products to be recovered and reused in other processes, while ensuring no sulfide contamination carries forward to affect subsequent steps
3Object-affected harmful factors
If sequential green steps are chained together, then biocompatible metal-free product is obtained, but process complexity increases
Solution Approach 1:
The patent divides the tanning process into distinct sequential steps: oxidative liming, washing, and metal-free tanning. Each step is optimized independently to ensure metal-free operation and biocompatibility, making the overall complex process manageable and controllable
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 process effectively recovers liming waste, reduces CO2 emissions by 3.3%, and produces a metal-free leather product with improved mechanical properties and reduced pollution, meeting regulatory standards for disposal.
Implementation Method 1
an oxidative liming in base environment of a hide wherein said oxidative liming comprises a treatment of said hide with lime... adding an unhairing solution of peroxide
Implementation Method 2
immunizing the hair of said hide with 0.8 to 1.2%, preferably with about 1% of hydrated lime; thereafter, adding an unhairing solution of peroxide in a percentage of between 2 and 3% of hydrogen peroxide, at a pH of between 12.0 and 12.5, wherein the pH is preferably adjusted by alkalizing the mixture with caustic soda (NaOH)
Data Source
AI summary
The invention relates to a tanning process which comprises the following step: (a) an oxidative liming in base environment of a hide. The oxidative liming comprises a treatment of the hide with lime. The oxidative liming, i.e. step (a), comprises the following steps wherein the percentages are to be understood as percentages by weight with respect to the weight of the hide: (a1) immunizing the hair of said hide with 0.8 to 1.2%, preferably with about 1% of hydrated lime; (a2) thereafter, adding an unhairing solution of peroxide in a percentage of between 2 and 3% of hydrogen peroxide, at a pH of between 12.0 and 12.5, wherein the pH is preferably adjusted by alkalizing the mixture with caustic soda (NaOH); and (a3) thereafter, neutralizing the bath. The process allows recovering all the components of the liming, in particular also the protein part in the liming bath. The hide obtained with the liming is sulfide-free. The invention also relates to a complete tanning process, from brining up to dressing, which complies with the ISO 15987 standard.