1、Chapter 2Modern Beamhouse Procedures -soaking,unhairing and Liming2.1 2.1 SoakingSoaking1.The purposes of soaking2.Soaking process:salted hides,fresh hides and dried hides3.Checking the end of soaking2.2 2.2 UnhairingUnhairing1.Unhairing(1)HAIR-SAVING-unhairing system 1-1 Sodium sulfide painting sys
2、tem 1-2 Enzymatic unhairing system a.Enzymatic painting system b.Enzymatic drum system(2)HAIR-BURNINGHAIR-BURNING-unhairing system2.3 2.3 LimingLiming1.The purposes of liming 2.Liming operations3.Checking the end of Liming process The history of beamhouseThe history of beamhouse Beam:Beam:The term d
3、ates back to the time when the hair was removed from the skins by means of a hand beam using a two-handled knife.Some hand work on the beam is needed occasionally for quality improvement.Such as scud.Beam BeamhouseBeamhouse Refers to the process in the tannery between the removal of the skins or hid
4、es from storage and their preparation for tanning.In the opinion of most practical tanners:Leather is made in the beamhouseLeather is made in the beamhousebeamhouse2.1 SoakingThe first and the most important steps1.The purpose of soaking1.The purpose of soaking Rehydration of the hide Hides and skin
5、s,when received by the tannery,are in a condition of preservation based on dehydration.The skins must be wet back and brought to a flaccid condition for subsequent operations.RemovalRemoval of:of:a.preserving saltsb.dirt and bloodc.unstructured proteins and proteoglycans Loosen Loosen ofof :a.epider
6、mal structuresb.subcutis Opening up the fibres Preparation of the hide for the subsequent process2.Conditions of soaking(1)Disinfectants The bacteria on hides may be dangerous to man,and bacterial damage to the hides may occur.Chlorinated aromatic compounds may usually be used.Infectious animal dise
7、ases:Infectious animal diseases:Anthrax Anthrax Hoof and mouth disease Hoof and mouth disease(2)Temperature Common,usually 25-28.The temperature of soaking is different from the different seasons,the areas(Such as in winter,in summer,the southern,the northern and so on).(3)(3)AdditivesAdditives(4)To
8、 accelerate the soaking process Sodium sulfide or sodium tetrasulfide Add a small quantity of sodium sulfide or sodium tetrasulfide to the soak may result in chemical action on keratin in the follicle,removal of soft globular proteins.Salt or appropriate alkali Salt in the soak:aids in the removal o
9、f globular proteins and in disinfecting the soak solution.Bactericide Limiting the growth of organisms or killing the bacteria.Enzymatic soaking/degreasing agent Surfactant/emulsifier Enzymatic soaking agents:will further accelerate soaking by use of specific proteolytic preparations to safely diges
10、t the non-structured proteins and proteoglycans.For a very fatty raw skin,such as pig,and sheep,choice of degreasing agents(emulsifiers)to remove fat.Deposits of fat will lead to poor penetration of liming agents,and subsequent areas of scud and drawn grain.(4).Water Salted hides:The liquor ratio is
11、 such that the quantity of water is low,the salt washed out from the cured hide is generally sufficient to maintain salt concentrations at a proper level for effective removal of some of the soluble protein.Dry hides:Addition of salt will be used to decrease probability of bacterial damage.The goods
12、 are fully covered with water.3.Soaking process The detailed process options will be introduce in Technology of Leather Making.Surfactant/emulsifier and suitable enzymatic soaking agent.soaking agent and bactericide will be added to the soaking liquor.Wet salted or brined hides Common temperature 25
13、-28.To remove surface salt,dirt,blood,and manure etc.by washing of 30 minutes.The time of soaking will depend on the type of hide or skin being processing,usually 24-48hours.Fresh hides(unsalted)To weaken and remove the non-structured protein(detailed in protein chemistry and Histology)T:25-28.Time:
14、6hours.Dried hides The fibers of dried hides are too stiff,and mechanical flexing will result in breaking of the fibers.When soaking heavy dried,it may still be necessary to pre-soak the goods overnight in static condition,if they are flexed too early before soak back,extensive damage to the skins c
15、an result.Such as loose grain,empty handle,and breaking of the grains.Conditions of soaking dried hidesSoaking time 24-48hours.pH:9.5-10Temperature 25-28.(Depending on using or not enzymatic soaking agent)Water float the goods are fully covered.VesselsVessels pit,paddle,DrumAdditives Wetting agents,
16、bactericide,salt,sodium carbonate,and enzymatic soaking agents.Operations Static soaking for 12-24hours,changing the float,the vessel may be turned or revolution each hour.4.Precautions To ensure that sufficient bactericide is present at all times.5.Checking The fully re-hydrated hides have regained
17、 a flaccid and natural condition,become noticeably softer and cleaner by feel and observation of a cut edge.Liming and unhairing 2.2 Unhairing2.2 Unhairing1.Unhairing(1)HAIR-SAVING-unhairing system 1-1 Sodium sulfide painting system 1-2 Enzymatic unhairing system a.Enzymatic painting system b.Enzyma
18、tic drum system(2)HAIR-BURNINGHAIR-BURNING-unhairing system (1)HAIR-SAVINGHAIR-SAVING-unhairing system 1-1 Sodium sulfide painting system A solution of lime and sodium sulfide,or sodium sulfide alone,or sodium sulfide plus caustic soda,making into a lime slurry,which is painted on the flesh side of
19、the skin and skins are piled in such a manner that sulfide paint is sealed in,or folded along the backbone.Two or three hours,the skins are ready for pulling.In pulling the wool,the skin is laid over a beam with wool side up,and the wool puller removes the wool by hand using scrubber or scudding kni
20、fe.The unhairing skin,or slat,is then placed in an additional liming solution,usually overnight,as liming.1-2 Enzymatic unhairing systemOne of the oldest practical methods of unhairing.Enzymes applied under controlled conditions by the tanner may selectively bring about the hydrolysis of the protein
21、s in the hair follicle.This will result in a controlled hair slip and removal of the hair in good condition.Commercial enzymes are from plant,animal or microbiological sources.Adv.Clean unhairing,no objectionable effluent problem,the hair can be re-used.Shortage Expensive,difficulty to control,more
22、often than not excessive damage to the skin collagen.(pits and holes)a.Enzymatic painting systemb.Sweating system By dipping the skins in water and hanginghanging them in a moist room for a period of time until the hair slip took place by natural wild bacterial growth.Painting Enzymes are painted on
23、 the flesh side of skins,piled at room temperature,about 2448hours(depend on the room temperature),or put the enzymes into drum,at 37-40,pH7.5-8.5(depend upon the enzyme),about 40120minutes.b.Enzymatic drum system Putting hides in the drum and adding warm water in it,adjusting the liquor temperature
24、 and pH to the optimum temperature and pH of the enzyme selected.After adding enzyme 2-4hours(depend on the enzyme selected),the hair were removal of from the hides and formed hair bulbs.The leather from this enzymatic unhairing are loss in thickness and increase in area,particularly in length from
25、head to tail.(2)(2)HAIR-BURNINGHAIR-BURNING-unhairing system-unhairing system In this system the quantities of sodium sulfide(sodium sulfhydrate)used are sufficient to cause the destruction of the hair.Sodium sulfide,sulfhydrate,lime are added.Within fifteen minutes the hair loses most of its fiber
26、structure.The reaction of unhairing by sulfide as a nucleophilic displacement is as follows:R-S-S-R+S2+R-S-S-+RS-RS-S-+S2+R-S-+S-S-Adv.Cheap,simply,safety for hides.Shortage Effluent problems.2.3 Liming(1)(1)The purposes of limingThe purposes of limingpurposes:to uniformly open up fiber structure an
27、d to remove the hair and epidermis.History:Since ancient times,the lime has been used as an unhairing system.In practice,there is a step called unhairing before the liming.Correct liming procedure:flat,tight and mellow leathers with maximum area yield.Poor liming procedure Draw deep growth marks and
28、 uneven tanning and post tanning processes.Chemicals:lime Dissolves in water to the extent of parts per 100 parts of water,produces a buffered alkaline solution of pH near 12.5.as a liming agent or self-basifying agent.Auxiliaries Sulphide or sulphide free agents(not economic in use)(2)Liming Operat
29、ion Temperature 25-26.See p30 line 2-3,line 6-7 Higher temperature will reduce physical properties such as tear and grain strength.Below will increase to scud and draw grain.Loading Correct loading will allow the goods to move in the intended manner within the vessel.When the goods are swollen,there
30、 will be returning to a slow speed or stop sequence,or will be seen as“leopard”grain,often in neck area.It is an abrasion Water float The goods are covered with water during the stationary process periods,the final float level of around 120150%on wet salted hides and 200300%on wet salted skins.Lime
31、loadLime load 2-3%lime will be used basis on the unhairing pelt.Liming auxiliaries To control the alkaline swelling and improve the solubility of lime,produce more uniform swelling and open-up of the fiber structure,resulting in a smoother,flatter and cleaner limed pelt.Such as surfactant/emulsifier
32、s,enzyme preparations able to work for preventing fat deposits,improvements in flatness and cleanliness of limed pelt.Checking a.Vessel speeds,temperatures,b.Cutting down the hide,no case-hardening,shows uniform swelling.Liming defect Since the fibers swell more in diameter than they do in length,th
33、ere will be a greater expansion of the surface area of the skin on the grain side than on the flesh side,which will result in a curling or rotting of the side.This occurs generally along the backbone,the skins may roll up quite tightly into long,ropy,sausage like bundles.The reason is of lack of pen
34、etration of additional action used in the initial stages to enable chemicals dispersed rapidly.Thinking and reviewingThinking and reviewing 1.Why fresh hides still need to be soaked?2.Please state the precautions for soaking flint-dried hide.3.The mechanism of sodium sulfide unhairing.4.Why enzymati
35、c unhairing is friendly environment?5.Why dont run the drum when the hides in swollen condition?1.Soaking 浸水浸水2.Unhairing 脱毛脱毛3.Liming 浸灰浸灰4.hair-saving system保毛脱毛法保毛脱毛法5.hair-buring system毁毛法毁毛法6.Enzymatic unhairing system酶法脱酶法脱毛毛7.Enzymatic painting system包（涂）包（涂）酶脱毛酶脱毛8.Sodium sulfide painting sy
36、stem包包（涂）灰脱毛（涂）灰脱毛9.sodium sulfide硫化钠硫化钠10.beamhouse鞣前准备鞣前准备11.rehydrate回水回水12.open up松散（打开）松散（打开）13.Disinfectant消毒剂消毒剂14.Solid door 实心门实心门15.Hollow axle 空心轴空心轴16.Perforated door 格子门格子门17.Additives 助剂助剂18.Bactericide 杀菌剂杀菌剂19.Surfactant 表面活性剂表面活性剂20.Emulsifier 乳化剂乳化剂21.degreasing agent 脱脂剂脱脂剂22.prot
37、eolytic preparations 蛋白水蛋白水解酶制剂解酶制剂23.caustic soda 苛性钠苛性钠24.Sweating system 发汗法发汗法25.Sulfate 硫酸盐硫酸盐26.Sulfide 硫化物硫化物27.Sulfhydrate 氢硫化物氢硫化物28.Sulfite 亚硫酸盐亚硫酸盐29.subcutaneous tissue 皮下组织皮下组织30.proteoglycans 蛋白多糖蛋白多糖31.subcutis 皮下组织皮下组织 32.proliferation 细胞增生，繁殖细胞增生，繁殖33.flay cut 描刀伤描刀伤 34.nubuck 正绒面革正
38、绒面革35.scuddy皮垢皮垢 36.immunization of hair护毛作用护毛作用37.premature 未成熟未成熟38.degreasing 脱脂脱脂39.proteolytic 水解蛋白的水解蛋白的 40.lipolytic 分解脂肪的分解脂肪的 41.Enzyme preparations 酶制剂酶制剂 42.emulsifier 乳化剂乳化剂 乳化器乳化器43.biocide 生物杀虫剂生物杀虫剂 44.foul恶臭的恶臭的45.beetle 甲虫甲虫 46.mould 塑模塑模 模型模型 样板样板 霉（菌）霉（菌）47.loose grain 松面松面48.Empt
39、y handle 空松的手感空松的手感49.patches 斑点斑点50.abrasion 磨耗磨耗51.scuffing 摩擦（鞋的）磨损摩擦（鞋的）磨损 52.leopard 豹豹 金钱豹金钱豹53.abrad 磨（抛）光，摩擦，擦伤磨（抛）光，摩擦，擦伤54.slip agent 滑动滑动 打滑打滑 掉毛掉毛 55.pulp浆状的浆状的56.swelling 膨胀膨胀 （plump）57.recipe 配方配方 处方处方 方法方法 诀窍诀窍 58.cystine n.胱氨酸胱氨酸 59.lanthionine n.羊毛硫氨酸羊毛硫氨酸60.flex弯曲弯曲61.float 液比液比62.
40、flaccid 柔软的，柔弱的柔软的，柔弱的63.hand feel 手感手感64.slat 裸皮裸皮65.sweating system 发汗法发汗法66.slip 掉毛掉毛67.growth mark 生长纹生长纹68.buffer 缓冲液缓冲液69.self-basifying agent 自动提碱剂自动提碱剂70.tear strength 撕裂强度撕裂强度71.scud 皮垢皮垢72.draw grain 皱面皱面73.swell 膨胀膨胀74.stationary 静止的静止的75.unhairing pelt 脱毛皮脱毛皮76.alkaline swelling 碱膨胀碱膨胀77.limed pelt灰皮灰皮78.case-hardening 未鞣透，脱灰不尽，未鞣透，脱灰不尽，未干透未干透79.backbone 背脊线背脊线80.neck area 颈部颈部
