Tanning Process Without Pickling Step
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Solution Overview
Problem
The tanning industry's reliance on the pickling step, which involves high amounts of sodium chloride, leads to significant environmental pollution and challenges in waste water purification, necessitating a process that avoids this step.
Innovation Solution
A tanning process that includes soaking, liming, deliming, maceration, and tanning without pickling, using a liquid mixture of water, sulphonates, C4-C6 dicarboxylic acids, and sodium acetate or formate to prepare hides for tanning, eliminating the need for sodium chloride and reducing environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pickling step is used in tanning process, then hides are prepared for tanning with appropriate pH and carboxyl group neutralization, but significant environmental pollution occurs due to high sodium chloride and acid discharge
Solution Approach 1:
The patent removes the pickling step from the traditional tanning process sequence. By extracting this harmful step, the process eliminates sodium chloride and acid discharge while maintaining hide preparation quality through alternative treatments in subsequent steps.
Solution Approach 2:
The patent changes the chemical parameters of the tanning process by avoiding pickling (pH 3-4) and instead using higher pH values (8-9) achieved through deliming and neutralization with carbonates or bicarbonates, thereby eliminating harmful acid and salt discharge.
2Ease of manufacture
If pickling with sodium chloride is used, then carboxylate groups are neutralized and tanning metal penetration is facilitated, but waste water purification becomes difficult due to high chloride content
Solution Approach 1:
By removing the pickling step that introduces sodium chloride, the patent eliminates the need for complex waste water purification systems designed to remove chlorides, thereby simplifying the overall process while maintaining tanning effectiveness.
Solution Approach 2:
The patent replaces expensive and complex waste water treatment infrastructure with a simpler process that uses readily available neutralizing agents (carbonates, bicarbonates) that can be easily disposed of or neutralized without requiring sophisticated purification systems.
3Stability of the object's composition
If conventional pickling process is used, then hides achieve appropriate pH and chemical stability, but volatile organic compound emissions increase
Solution Approach 1:
The patent changes the chemical approach by avoiding acid-based pickling and instead using alkaline neutralization with carbonates or bicarbonates, which eliminates volatile organic compound emissions while achieving the required chemical stability through alternative biochemical pathways.
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 process achieves tanned hides with chemical stability and physical-mechanical characteristics comparable to conventional methods, while significantly reducing sodium chloride and pollutant discharge, and lowering volatile organic compound emissions.
Implementation Method 1
the hides are treated with a liquid mixture consisting of: water in an amount between 40 and 60% by weight with respect to the weight of the hide; between 0.5 and 2.5% by weight with respect to the weight of the hide of an emulsion containing between 45 and 60% by weight of water and between 40 and 55% by weight of an oil consisting of one or more sulphonates
Implementation Method 2
The aim is both to prevent the formation of chromium hydroxides (which occurs at pH values above 4-4.5), which would make the addition of the element useless, and to neutralize the free carboxylate groups produced in the liming step by forming R—COOH carboxyl groups.
Implementation Method 3
Tanning: finally, the hide deriving from the pickling process is subjected to the actual tanning process, the chemical operation that transforms the still putrescible hide into an imputrescible material, i.e. leather.
Data Source
AI summary
The present invention relates to a process for the tanning of animal hides characterised, compared to currently adopted processes, by the non-adoption of the step known in the industry as “pickling”. The invention also concerned hides tanned by said process.