Minimization of Process and Wastewater Load in a Low-Pressure Environment through Vacuum Application for Fiber-Based Materials: Leather and Cotton Products

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Leather and float analyses after conventional dyeing process

Process	Dyestuff float exhaustion (%)	Color strength on leather after dyeing (K/S)
Conventional dyeing process	71.18 ± 3.28	12.36 ± 0.57

Conventional dyeing recipe

Process	%	Substances	Temperature (°C)	Time (min.)	Remarks
Dyeing	100	Water	40
	2	Dye auxiliary		30
	5	Dyestuff		60
	1	Formic acid		40	pH: 4.0
Drain-Washing-Horsing-Mechanical operations

Results of leather dyeing with metal complex dyestuff and cotton dyeing carried out in a conventional and vacuum cabinet

Process	Float exhaustion (%)	Color strength (K/S)
Conventional system (metal complex dye, leather)	74.05 ± 4.47	14.81 ± 3.35
Vacuum system (metal complex dye, leather)	96.79 ± 2.24	15.23 ± 0.74
Conventional system (hypericum dye, cotton)	92.21 ± 1.93	6.91 ± 1.23
Vacuum system (hypericum dye, cotton)	98.76 ± 2.01	7.06 ± 1.19

Rubbing fastness values of dyed samples

Process	Rub fastness
Conventional system (acid dye, leather)	4/5
Conventional system (metal complex dye, leather)	4/5
Conventional system (hypericum dye, cotton)	4
Vacuum system (acid dye)	4/5
Vacuum system (metal complex dye)	4/5
Vacuum system (hypericum dye, cotton)	4

Composition and identification of cotton sample

Yarn number in warp	Yarn number in weft	Fabric composition		Interlacing
68/1	68/1	-	100%c	5/2

Leather and float analyses after dyeing processes carried out in a vacuum cabinet in dependence on water usage ratios

Process	Float exhaustion (%)	Color strength on leather (K/S)
80% water use	92.15 ± 1.47	20.36 ± 1.61
50% water use	91.45 ± 1.77	19.20 ± 1.13
25% water use	90.32 ± 2.63	18.78 ± 2.05
Free of water use (only dissolving water)	86.56 ± 2.82	16.45 ± 1.16

Leather dyeing recipe under vacuum

Process	%	Substances	Temp. (°C)	Time (min.)	Remarks
Dyeing	A	Water	40		A1-A4
	2	Dye auxiliary		30
	B	Dyestuff		C	B1-B4, C1-C3
	1	HCOOH		40	pH: 4.0
Drain-Wash-Horsing-Mechanics

Leather and bath analyses after dyeing processes carried out in a vacuum cabinet in dependence on dyestuff usage ratios

Process	Float exhaustion (%)	Color strength on leather (K/S)
4% dyestuff	94.02 ± 2.42	15.49 ± 1.90
3.5% dyestuff	95.25 ± 2.91	12.41 ± 1.29
3% dyestuff	93.35 ± 4.30	11.32 ± 1.37
2.5% dyestuff	92.86 ± 3.19	9.45 ± 0.76

Leather and float analyses after dyeing processes carried out in a vacuum drum in dependence on the process time

Process	Float exhaustion (%)	Color strength on leather (K/S)
45 mins	94.05 ± 2.87	15.18 ± 1.52
30 mins	92.02 ± 1.96	12.38 ± 2.39
15 mins	80.11 ± 3.69	10.77 ± 1.10