Shrink Calf Leather Processing for Uniform Grain Formation
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Solution Overview
Problem
Existing methods for producing leather shrinkage result in irregular grain patterns both within a single skin and across a batch, due to variations in skin structure and difficulty in adjusting thickness, leading to high scrap rates and a need for high-quality shrink calf leather in the 2.1-2.6 mm thickness range.
Innovation Solution
A method involving chrome-tanned skins treated with specific solutions including non-ionic surfactants, sodium formate, fatty acid esters, polymeric tanning agents, anionic dyes, formic acid, and polyurethane dispersions, followed by precise control of moisture and drying processes to achieve uniform shrinkage and reduced scrap rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional shrinking methods are used, then shrinkage effect is achieved, but grain pattern uniformity deteriorates
Solution Approach 1:
The patent applies preliminary actions by treating the leather with specific solutions (non-ionic surfactant washing, neutralization with sodium formate and bicarbonate, prefatting with fatty acid esters) before the actual shrinking process. These preparatory treatments standardize the leather substrate, ensuring uniform grain pattern formation during subsequent shrinkage while maintaining consistent shrinkage effects across batches.
Solution Approach 2:
The patent employs parameter changes by precisely controlling chemical concentrations (0.2% non-ionic surfactant, 1.5% sodium formate, 3% sodium bicarbonate, 0.5% fatty acid ester) and processing conditions (temperature, time, pH levels) throughout the treatment sequence. These controlled parameter changes enable simultaneous achievement of uniform grain patterns and consistent shrinkage effects.
2Manufacturing precision
If skin structure variations are not addressed, then processing is simpler, but grain pattern irregularity increases
Solution Approach 1:
The patent applies local quality principles by using non-ionic surfactants that selectively interact with different regions of the leather based on their local structure variations. The surfactant penetrates and conditions areas with different porosity and fiber density differently, standardizing the substrate locally across the entire skin to ensure uniform grain formation despite inherent structural variations.
Solution Approach 2:
The patent introduces intermediary substances (non-ionic surfactants, polymeric tanning agents, retanning agents) that mediate between the variable skin structure and the shrinking process. These intermediaries uniformly modify the leather properties across different regions, creating a standardized base that produces consistent grain patterns regardless of initial skin variations.
3Loss of substance
If thickness adjustment is difficult, then processing time is reduced, but scrap rate increases
Solution Approach 1:
The patent performs preliminary thickness standardization through controlled prefatting and retanning processes that uniformly modify the leather substrate before shrinking. This preliminary action ensures all skins reach the target thickness range (2.1-2.6 mm) with uniform grain patterns, allowing rejection of only truly defective pieces and reducing overall scrap rates despite extended processing time.
Solution Approach 2:
The patent uses parameter changes in the form of controlled chemical treatments (polymeric tanning agents, retanning agents with specific concentrations) that precisely adjust leather thickness and density. These controlled parameter modifications enable accurate thickness control within the 2.1-2.6 mm range, minimizing waste by preserving usable leather that would otherwise be scrapped.
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 method produces leather with a consistently uniform grain pattern and reduced scrap rates, achieving high-quality shrink calf leather with controlled thickness, enhancing surface utilization and processing efficiency.
Implementation Method 1
washing at least one chrome-tanned skin (chrome wet blue) in a washing solution containing about 200% (w/w) water and about 0.2% (w/w) of a non-ionic surfactant
Implementation Method 2
neutralizing the treated skin in a neutralizing solution containing about 100% (w/w) water, about 1.5% (w/w) sodium formate and about 3% (w/w) sodium bicarbonate
Implementation Method 3
prefatting the skin comprising incubating the skin with about 0.5% (w/w) solution of a fatty acid ester
Implementation Method 4
dyeing of the fur in a dyeing solution comprising about 50% (w/w) water, about 1.5% (w/w) ammonia and anionic dye
Implementation Method 5
fatliquoring by adding about 100% (w/w) water and about 4.5% fatliquor mixture, this fatliquoring mixture comprising about 45% (w/w) long-chain paraffins and about 55% (w/w) sulphited oils
Implementation Method 6
fixing by adding formic acid
Implementation Method 7
applying a binder mixture solution comprising binder mixture and an inorganic pigment dispersion in a ratio of 4:1, the binder mixture solution having about 40% (w/w) finely divided polyurethane dispersion
Implementation Method 8
drying the fur; dehumidification of the fur; conditioning of the fur and further reduction of the moisture content
Data Source
Figure 1
Figure 2A~2B
AI summary
The invention relates to measures for the treatment and finishing of leather. In particular, it relates to a method for producing leather shrinkage comprising the following steps a) washing at least one chrome-tanned hide (chrome wet blue) in a washing solution, b) neutralizing the treated hide in a neutralizing solution, c) prefatting the hide, d) coloring of the fur in a dyeing solution, e) fatliquoring by adding a fatliquor mixture, f) fixing by adding formic acid, g) final tone adjustment, h) fixing, i) washing the fur, j) drying the fur, k) applying a binder mixture solution, 1) application of an aqueous emulsion varnish based on polyurethane, m) ironing and staking of the fur, n) fulling of the fur with continuous supply of moisture, o) dehumidification of the fur, p) conditioning of the fur and further reduction of the moisture content and q) application of a fixative -Solution.