Reactive Leather Dyeing with Covalent Fixation for High Fastness
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Solution Overview
Problem
Current leather dyeing processes with reactive dyes fail to achieve high wet- and perspirationfastness, especially at medium to high depths of shade, due to inadequate fixation yields and damage to leather, making them unsuitable for producing high-quality leather goods for segments like footwear and automotive.
Innovation Solution
A process using dyes with an alkaline-activable group in formula A, applied at a pH of 7.5 or higher, which allows for rapid dyeing and fixation, achieving 85% or more color intensity and high fixation rates, thereby enhancing wet-, perspiration-, and rubfastness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional dyes with ionic bonds are used, then dyeing process is simple, but wet- and perspirationfastness are poor because aqueous alkaline solutions destroy the ionic bond
Solution Approach 1:
The patent changes the bonding mechanism from ionic to covalent by using reactive dyes with specific functional groups (vinyl sulfone, dichlorotriazine, isocyanate) that form covalent bonds with leather amino groups, making the bond resistant to aqueous alkaline solutions while maintaining process feasibility
Solution Approach 2:
The patent creates a composite chemical structure where the dye molecule forms a covalent bond with the leather protein structure, combining the dye's coloring function with the leather's structural integrity to achieve both fastness and processability
2Reliability
If reactive dyes with vinyl sulfone group are used, then covalent bonding is achieved, but long dyeing times at pH 10 are required which damages leather
Solution Approach 1:
The patent modifies the reactive group from vinyl sulfone to dichlorotriazine or isocyanate groups that react faster and at lower pH values, reducing dyeing time from 7+ hours to 1-4 hours while maintaining high fixation yields above 85%
Solution Approach 2:
The patent adopts the successful covalent bonding concept from textile reactive dyes and adapts it to leather by selecting reactive groups and conditions appropriate for leather's amino group content and structure
3Reliability
If dichlorotriazine reactive dyes are used, then covalent bonding is achieved, but fixation yield is only 70-75% which is insufficient for high fastness
Solution Approach 1:
The patent designs dyes with multiple reactive groups per molecule (di- or polyfunctional) that can form multiple covalent bonds with the leather, increasing the probability of successful bonding and achieving fixation yields above 85%
Solution Approach 2:
The patent optimizes pH to 8.5-10.0 and temperature to 20-40°C to maximize the reactivity of the dichlorotriazine and isocyanate groups with leather amino groups, achieving high fixation yields without requiring extreme conditions
4Reliability
If multiple process steps with separate dye and fatliquor application are used, then desired fastness is achieved, but process complexity and wastewater increase
Solution Approach 1:
The patent combines dyeing and fixation into a single simultaneous process by using reactive dyes that bond covalently during the dyeing step itself, eliminating the need for separate fixation floats and reducing process complexity and wastewater
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 ensures excellent fastness properties, including rubfastness and migrationfastness, even at high depths of shade, with minimal leather damage, making it suitable for producing high-quality leather goods.
Implementation Method 1
Reactive dyeing refers to the use of dyes which have functional groups capable of forming a covalent chemical bond with the functional groups of leather
Implementation Method 2
the fraction of a chemically bound dye
Data Source
AI summary
The present invention relates to a process for dyeing leather with at least one dye F which has at least one alkaline-activable group of the formula A;where- - - - denotes the bond to the rest of the dye molecule;X is an electron-attracting radical,k is 1, 2 or 3,n is 0 or 1 andB is a CH═CH2 group or a CH2—CH2-Q group, where Q is an alkaline-detachable group,which comprises treating the leather with an aqueous float comprising at least one dye F at a pH of not less than 7.5. The present invention also relates to novel dyes which are particularly useful for reactive dyeing of leather.