Improvement of conventional leather making processes to reduce the environmental impact

1. Improvement of conventional leather making processes to reduce the environmental impact Eduard Hernàndez Balada Doctoral Thesis directed by Dr. José Costa López Dr. Jaume Cot Cosp Programa de Doctorat d’Enginyeria del Medi Ambient i del Producte Bienni 2006-2008 Barcelona, 5 de febrer 2009 FACULTAT DE QUÍMICA DEPARTAMENT D’ENGINYERIA QUÍMICA

5. Hide preservation . Treatment given to raw hides or skins just removed from the carcass of the animal to minimize putrefaction. Beamhouse (Pretanning). Processes in the tannery that take place between the removal of the skins or hides from storage and their preparation for tanning. Tanning . Process by which the pelt is converted into a stable material which is resistant to microbial attack and has enhanced resistance to heat. Post tanning operations . Includes wringing, splitting, retanning, coloring, fatliquoring, setting out, drying. Finishing operations . The act of making completely tanned leather more attractive, serviceable and durable. Raw hides and skins Preserved hides and skins Wet blue leather Crust leather Finished leather Pelt Conversion of hides and skins into leather Introduction – Hides and skins

6. Conversion of hides and skins into leather Preserved Hides and Skins Pelt Wet Blue Leather Crust Leather Finished Leather Finishing Operations Preservation Pretanning Tanning Post tanning Operations Trimming Soaking Unhairing Liming Deliming Bating Scudding Pickling Wringing Splitting Retanning Dying Fatliquoring Setting Drying Conditioning Staking Toggling Buffing Spraying Plating Stages Unit Operations Outcome Introduction – Hides and skins

12. Brine curing of raw hides and skins Composition of the hide before the cure Composition of the hide after the cure Introduction – Preservation of raw hides and skins H 2 O H 2 O H 2 O H 2 O Hair side Flesh side NaCl NaCl NaCl NaCl

15. Split the hide in three layers (grain, middle, flesh) Piece of ~ 100 g Cure with 95 °SAL brine (initial concentration) for various time intervals (0.5, 1, 2, 4, 8, 16, 24 h) and 500% float Squeeze out the excess moisture % moisture % ash % salt saturation Wash raw hide @ 6 rpm for 2 hours, 100% float (with 0.15% Boron TS and 0.10% Proxel GXL) Flesh Middle Grain Flesh and adipose tissue Junction of grain and corium and epidermis Majority of the corium Stratrigraphic study – Experimental ( ρ hide = 1 g/cm 3 )

17. CoroNa Green dye is a sodium ion indicator that exhibits an increase in green fluorescence emission intensity upon binding Na + with little shift in wavelength. Fluorescence imaging MW=586 Da Brine concentration: 30% (w/v) NaCl 500% (v/v) float 5 μM CoroNa Green Stereomicroscope equipped for epifluorescence Samples irradiated with blue light (470/40 nm) Magnification: 2.5x 15min 30min 1h 2h 3h 4h 5h 28h 48h Flesh Hair CoroNa Green Na + indicator Fluorescence emission spectra of the CoroNa Green indicator Stratrigraphic study – Results

25. Degreasing study – Introduction Grease distribution in raw hide and wet blue Removal of fat Increase of NaCl uptake Reduction of turn around times in the raceway Creation of additional curing capacity

29. Commercial Degreasers - Results Degreasing study – Results

30. Commercial degreasers and SL: 0.5% (w/w) Sophorolipids - Results 40.4 38.5 36.6 SL-unfiltered 27.2 32.3 36.9 SL-filtered 46.1 47.8 48.7 Degreaser 3 10.9 11.5 9.5 Degreaser 2 42.5 48.3 51.8 Degreaser 1 Moisture and ash free basis (MAFB) Moisture free basis (MFB) As it is Fat Removal (%)/Degreaser Degreasing study – Results

42. Biopolymer study – SDS-PAGE results Inter-protein crosslinking was evaluated by polyacrylamide gel electrophoresis in sodium dodecyl sulfate (SDS-PAGE) Lane 1 : molecular weight markers Lane 2 : gelatin 10% (w/w) Lane 3 : gelatin 10% (w/w) after treatment with mTGase (10 U/g) under reducing conditions Lane 4 : WPI 10% (w/w) Lane 5 : WPI 10% (w/w) after treatment with mTGase (5 U/g) Lane 6 : WPI 10% (w/w) after treatment with mTGase (5 U/g) under reducing conditions Lane 7 : WPI 10% (w/w) with gelatin 1.5% (w/w) Lane 8 : WPI 10% (w/w) with gelatin 1.5% after treatment with mTGase (2 U/g) Lane 9 : WPI 10% (w/w) with gelatin 1.5% after treatment with mTGase (2 U/g) under reducing conditions Biopolymer study – Results 1 2 3 4 5 6 7 8 9 0 Da 200 kDa

45. Shoe upper wet blue – Protein uptake results Proteinaceous blend: 5% (w/w) WPI + 0.5% (w/w) gelatin, with respect to weight of wet blue Filler study – Results

46. Upholstery wet blue – Protein uptake results mTGase offer: 2.5% (w/w) Proteinaceous blend: 2.5% (w/w) WPI + 0.25% (w/w) gelatin, with respect to weight of wet blue Filler study – Results

47. Protein uptake results – Uptake rate coefficients One may consider that the absorption of protein by the wet blue follows a first order reaction kinetics, where k is the reaction rate coefficient. Filler study – Results Uptake rate coefficient k for various treatments x 0.68 x 0.78 x 0.53 x 3.77 Upholstery wet blue Shoe upper wet blue

48. Shoe upper wet blue – Mechanical properties Three dimensional regression plots of the mechanical properties of the belly area with respect to % WPI and % mTGase. Filler study – Results

49. Upholstery wet blue – Mechanical properties Filler study – Results

50. Shoe upper wet blue – Subjective properties All test samples treated with 5% (w/w) WPI + 0.5% (w/w) gelatin, with respect to weight of wet blue Improvement No effect Worsening Filler study – Results

51. Shoe upper wet blue – Subjective properties (Grain break) Control sample – Belly area Pretreated with 2.5% mTGase followed by treatment with 5% WPI + 0.5% gelatin (all weights with respect to weight of wet blue). Test sample – Belly area Filler study – Results

52. Shoe upper wet blue – Subjective properties (Color) Test : Pretreated with 2.5% mTGase followed by treatment with 5% WPI + 0.5% gelatin (all weights with respect to weight of wet blue). Filler study – Results

53. Shoe upper wet blue – SEM images Magnification: x1000 Test : Pretreated with 2.5% mTGase followed by treatment with 5% WPI + 0.5% gelatin (all weights with respect to weight of wet blue). Filler study – Results Belly Butt Neck Control Test 50.0 μ m

54. Upholstery wet blue – Subjective properties All test samples treated with 2.5% (w/w) WPI + 0.25% (w/w) gelatin, with respect to weight of wet blue Filler study – Results 2.5% mTGase 2.5% mTGase 0% mTGase 0% mTGase 0% mTGase 2.5% mTGase 2.5% mTGase 2.5% mTGase

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