Pressure Tanning Leather with Carbon Dioxide
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Solution Overview
Problem
Conventional leather tanning processes generate significant environmental pollution due to high water and chemical usage, leading to excessive waste water and salt consumption, and require lengthy processing times.
Innovation Solution
A method involving soaking, dehairing, and pressure treatment with compressed carbon dioxide to reduce liquid content and eliminate the need for deliming, pickling, and salt, allowing for pH control through carbon dioxide pressure to facilitate tanning, thereby reducing waste water and processing duration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional deliming and pickling processes are used with high salt concentration, then skin swelling is controlled and tanning can proceed, but excessive waste water and salt consumption occur causing environmental pollution
Solution Approach 1:
The patent changes the pH parameter dynamically during the tanning process by controlling carbon dioxide pressure. By adjusting pressure, the pH shifts from alkaline (suitable for dehairing) to acidic (suitable for tanning), eliminating the need for separate pickling and deliming steps with high salt consumption.
Solution Approach 2:
The patent extracts and eliminates the need for separate deliming and pickling processes that require high salt concentrations. By using pressure-controlled carbon dioxide treatment, these intermediate steps with excessive salt usage are removed entirely.
2Reliability
If conventional pickling is carried out with sulfuric acid and high salt to prevent acid swelling, then tanning can proceed without dead tanning, but the processing time increases to 3-14 hours
Solution Approach 1:
The patent maintains continuous useful action by performing dehairing, deliming, pickling, and tanning in a single continuous pressure treatment process. The pH is adjusted dynamically within the same treatment cycle, eliminating idle time between separate process steps.
Solution Approach 2:
The patent merges multiple separate processes (dehairing, deliming, pickling, tanning) into a single integrated pressure treatment process. By controlling carbon dioxide pressure, all these functions are achieved in one continuous operation rather than sequential steps.
3Manufacturing precision
If conventional tanning uses large amounts of aqueous solution (liquor ratio 2:1 to 0.5:1), then tanning agents can penetrate the skin uniformly, but significant waste water is generated
Solution Approach 1:
The patent uses pressurized carbon dioxide gas instead of large volumes of aqueous solution. The gas penetrates the skin under pressure, delivering tanning agents uniformly without the need for excessive liquor, thereby minimizing waste water generation.
Solution Approach 2:
The patent utilizes the phase transition properties of carbon dioxide. By controlling pressure, CO2 transitions between gaseous and dissolved states, enabling uniform penetration of tanning agents into the skin without requiring large volumes of liquid solution.
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 high-quality leather with reduced environmental impact by minimizing waste water and chemical usage, saving time and resources, and eliminating the need for salt and acid additives.
Implementation Method 1
the pH value can drop to 2.5... The concentration of electrolytes in the free liquor brought about by the addition of salt
Implementation Method 2
The concentration of electrolytes in the free liquor brought about by the addition of salt leads to a reduction in the osmotic swelling of the skin cells
Implementation Method 3
The pelt has a water content of 60 to 80%, i.e. 10 kg pelt contains 6 - 8 kg water
Data Source
AI summary
The invention relates to a method for tanning hides, comprising the following steps: softening the hides in liquid at a pH value in a range of approximately 7 to approximately 10, unhairing the hides in liquid at a pH value of up to 13, dewatering the dripping-wet hides by 5 to 40 wt%, treating the moist hides in a pressure vessel at a pressure of 5 to 60 bar for a pressure treatment time of 60 to 360 minutes, wherein the pressure is built up by feeding carbon dioxide, introducing a tanning solution into the pressure vessel, wherein the mass of the tanning solution preferably corresponds at least substantially to the mass by which the dripping-wet hides have been dewatered in the dewatering step, lowering the pressure in the pressure vessel at least substantially continuously to ambient pressure over a pressure-relief time period of 15 to 90 minutes. Consequently, the method according to the invention leads to significantly reduced wastewater, and thus significantly reduced environmental impact, in relation to known tanning methods while achieving at least the same quality of the tanned leather.