Leather Industry


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Leather Industry

  1. 1. Leather Industry • sources:US, Argentina, Australia, Brail & Canada  Bark-tanned pigskin – for bags & cases, History 5. Calfskin – used for expensive shoes, handbags and Mechanical Manufacturing Process leggings. • Leather is known to be “the most historic of similar articles; finer grained & lighter in weight than cattle hides strength Fairly good Very good  Vachette leather – for furniture, Terms: useful materials” motorcars… • The original primitive method was simply • sources: US & Europe o Tanning – the skin is turned into leather drying, either in air & in sunlight. 6. Kidskin – imported from countries where goats  Japanese leather – similar to alum-tanned o Tannins – complex mixtures of glucosides are raised for milk & meat leather, for braces. • In 1200 B.C., (age of the Homeric heroes) Greeks • sources: India, SA, & Central Africa 3. Fine leather – for gloves, lining, and of various polyphenols, combining were using leather garments and later spread 7. Horse hides – used for shoes, jackets & sports bookbinding between the collagen fibers of the skin. Characteristics of Leather:  liberates sugar during the tanning throughout the Roman Empire (The protective equipment armor of the Roman soldier was a heavy leather • sources: France & Belgium  Fancy leather – for handbags & other process o Uneven chemical composition articles, made from crocodiles, snakes, SKIN + TANNIN = LEATHER + SUGAR shirt.). 8. Pigskin – sources: US, Central Europe & South o Tensile strength – determines to what degree lizards… • acidity of pH is controlled by the used America o By trial and error, man discovered methods of 9. Lizards & Snakes Skin – provide leather with the leather may subjected to stretching.  Glove leather – includes alum salt leather, of sulfuric acid. preserving and softening leather treating animal o Permeability – determines to what extent the skins with smoke, grease and bark extracts. unusual textures and colors for shoes, handbags, & leather of a shoe garment will allow the nappa leather, & chamois leather o Keratin – a protein containing crystine luggage 4. Technical leather – for hose, straps, drums & residue which is easily attacked by an o Hebrews originated the tanning effects of removal of water of perspiration from the 10. Deerskin & Buckskin – skins from the deer parchments. alkali. body/feet. leaves/ barks of certain trees in water. 11. Water Buffalo, ostriches, seals, & sharks – for  Belting leather unusual leather. o Changeability of area – determines the o Neutralization – adjustment of pH for • In the middle ages, “England” – center for degree of physical discomfort in a shoe  Hose leather - for pumps different types of skin leather making & for the export of leather. resulting from the variability of relative  Lace leather o Chinese knew the art of making leather. Layers of Animal Skin humidity.  Strap leather o Liming – loosening & removing the Temper – measured by folding lightly in  Machine leather epidermis & hair from the hide o “Buckskin tan” – type of leather made by the a) o Indians Epidermis – outer layer constituting 1% of upper leather  Gas mask leather 10% lime, 2% Na2S (based on hide the total skin & chiefly consists of protein  developed great skills in leather work keratin. o Leather resilience – for soles and heels  Parchment & drum leather – made from weight) o Susceptibility to acid pigskin, calfskin, goat skin & sheep skin.  3 – 7 days/vats before the coming of the white man.  knew nothing of the bark tanning methods b) Derma/corium – a thick layer of living o Resistance to wear o Retanning – gives the required handles to tissue below the epidermis o Resistance to heat & water Raw Materials: used in Europe. the leather & modify the dyeing is chemically resistant, allowing the o Ability to hold embossing • In 1632, Bark tanning methods were introduced - epidermis to be easily removed by o Ability to absorb heat  Animal Hides/Skins – Batangas & Cebu characteristics by French in Canada & English in New England chemical means. o Porous are the main sources of hides in the Phils. o Dehairing – usually placed in a vat of • In 18th century, Sir Humphry Davy – discovered c.) Flesh – is an extraneous layer of adipose Kinds of Leather  Sodium Sulphide – a sharpening agent warm water which permits easier removal used in accelerating the dehairing process. of hair. other barks that could be used for tanning aside tissue which must be removed to ensure from oak & sumac. tannin penetration on both side of the  Lime water – unhairing agent o Fat liquoring – it restores the fatty oils 1. Heavy Leather – for sole and belting  o • In 19 century, Vegetable tanning, i.e., tanning th corium. 3+ Chrome (Cr ) – exhibits a slight tanning Preservation – usually by salts to avoid using the extracts from the bark of certain kinds Infos:  Sole leather – a vegetable tanned (good effect; source: Masinloc, district of decomposition of hides of trees, was supplemented by chrome tanning. • Addition of hot water causes slow thickness & firmness). Zambales o Pickling – reduces the pH of the skin to o “Chrome-tan leather” was introduced by solubilization to collagen when producing  Light Sole leather – a vegetable tanned  Chromic sulphate – exhibits a stronger between 2.0 to 2.5. Augustus Schultz & Robert Foerderer, with the gelatin (pliability & suppleness). tanning effect. o Bating/deliming – uses ammonium sulfate improvement of machinery made it possible to • Hair has large keratin which grows thru  Insoling & Offal Leather – vegetable  Formic acid – swelling agent in the soak or chloride for the removal & alteration of produce leather cheaper. both the derma & epidermis. tanned, no fillers are necessary. water. certain proteins & for the improvement of Definition:  Belting Leather – made from high quality  Sulfuric acid – used in regulating the pH & the color of Comparison of Skins & Leather: hides SKINS, KIPS, HIDES the grain in the tanning process; a pickling acid Leather –a material created through the tanning of  Chrome belting leather – fat liquored, together with HCOOH.  Falling – Skins/Hides Leather (rxn. in bating), a reduction in the hides and skins of animals that has been made pliable greater resistance to moisture & acid  Atlasol – degreasing & wetting agent degree of swelling of the protein & resistant to decay thru the chemical treatment Soon lose vapors. called tanning. Pliability pliability & Retains Pliability  Syntans(Synthetic tanning agents) – constituents of the limed skin become hard &  Chrome sole leather – for sport boots. condensation products of sulfonated 2. Light & Dressing leather - for boot uppers, phenols & formaldehyde, capable of Tannery Operations: Types of Skins: brittle harness & upholstery. converting animal skin to leather. Extremely a. Pretanning process – non-leather making • Skin – used as a generic word to denote skin from Permanence Putresce very permanent, not  Bark-tanned uppers – a.) russet leather, if o Classification acc. to use: a.) Auxiliary constituents of the skin are removed all kinds & sizes of animals. quickly attacked by finish is on the grain side b.) wax leather, tannins, b.) Complementary tannins, c.) bacteria if finish is on the left side. Replacement tannins b. Actual tanning process – skin is turned into leather 1. Hides – skins from larger animals (weighs 34 lbs. Water Absorb water Possesses great  Chrome tanned uppers – one-bath or two-  Sodium Sulphate – prevents acid swelling. up) resistance & are resistance to bath process tanned. sources: Nueva Viscaya c. Post-tanning process – required color & 2. Kips - skins from half-grown animals of larger permeated water appearance is imparted into the leather. varieties (weighs 5 lbs. in wet state) easily by it  Combination tanned uppers –  Fat Liquors 3. Skin – skins from smaller animals Are converted combination of chrome & vegetable  Dye Stuffs – either powder or liquid tanned. 4. Cattle hides – most important source of leather Boiling water to gelatin by Attacked with  Sodium Dichromate – main raw materials raw materials hydration great difficulty  Harness leather - for clothing, leggings… for tanning process
  2. 2. “geto” – graded,  Stuffing – is done by adding several “Life is good when we’re having fun” - Bambini Trimming coats of compounds cont’g clay, mineral examined, trimmed, Rinsing Vat salts, corn ugar @ 60°C. Prepared by: Juphil Lamanilao & open Soaking Pit o Chrome Tanning – usually subdivided 3 – 24 hrs flesh – removed by a into 2 processes which penetrate the hide spiral bladed cylinder very rapidly FINISHING OPERATIONS  One bath process – using chromium Beaming 1% sodium terasulfide – hastens sulfate rehydration & produces more Dyeing Stuffing Splitting  Two-bath process – using sodium uniform hydration. Drum Drum Machine dichromate 10% Ca(OH)2, Liming  requires 8 hrs. of continuous process 2% Na2S – sharpening oil (3 -7 days) with the hides maintained between 2 to agent; sulphydrate, dimethylamine, Jacking Bench 4 pH. cyanide salts. o Oil tanning – an old method in which fish Dehairin oil or other oil and fatty substances are Drying Loft g or hand-scraped stocked, or pounded, into dried hide until Machine they have replaced the natural moisture of the original skin. Embossing rolls Scudding bench  used principally to make chamois leather. tryptic enzymes MEASURING MACHINE Bating, 90°F (20 – 30 mins) H20 Preservation & Disinfection of Skins: (Vegetable tanning) Rinsing Vat • Curing - a method of short term preservation Drenchin (Chrome Tanning) g o Brine curing – immersing it in a Vat saturated brine solution o Salt Curing - sprinkling it liberally on organic acids (A) Pickling both sides with common salt. pH 3.5 Drum  requires 3 to 4 weeks @ 13°C  Dehydrates NaCl  Salt Absorption H2SO4 (B) Methods of Tanning: (A) (B) 30% HCl o Vegetable Tanning –used for heavy leathers, for soles & belting Tanning Vats 1st bath 2nd bath  2 Broad Groups: (30 days)  Catechols  Pyrogallols  usually done in 8x7 ft vats, 5 or 6 deep, Na2Cr2O7.H2O containing tan liquors and hides. Lay- away  from weakest tanning liquors thru Vat (60 days) liquors of increasing strength. Reduction Na2S2O3 Drum  to prevent complete plugging of the surface pore  Ratio (liquor/hide) = 4 to 6 lb liquor/lb hide. Setting Drum Borax  Bleaching – is done by using dilute solutions of oxalic acid or acidified solutions of sodium metabisulphite.