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Методические указания по выполнению семестровой контрольной работы с комплектом заданий по английскому языку студентов дистанционной формы обучения Уфа 2007

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Контрольное задание № 4

для студентов специальности "Технология кожи и меха"

Вариант I

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Hides and skins

I. The hides and skins used in the manufacture of leather are generally obtained from animals killed for food.

The coverings of large animals are classified as hides, whereas those of small animals are known as skins.

Hides and skins soon putrefy if allowed to remain in a moist condition, 30 it becomes necessary to treat them in such a manner that they may be kept undamaged until ready for the tanning processes. This operation, known as curing, may be done in several ways. The cure has a decided influence upon the hide, and largely determines the character of the leather. The pelts of animals come to the tanner in four conditions: I) green (fresh from the animal); 2) green-salted (where the salt has been rubbed on the flesh-side); 3) dry-salted (rubbed with salt and dried); 4) dried (usually stretched on boards in the sun).


The pelts so received are divided according to the size into three general classes, namely: hides, kips and skins.

2. Hides comprise pelts from large and fully grown animals suchas the cow, horse, camel and walrus. These give thick, heavy leather for shoe soles, machinery belting and other purposes. Cowhides can be divided into two layers. These layers of hides aremade into leather shoes. The hide of the horse also serves as theleather for shoes.

Kips are the skins of undersized animals of the above species.

3. Skins are obtained from small animals such as calves, sheepsend goats. Kips and skins yield a lighter leather than hides,which is suitable for a great variety of purposes such as uppersfor shoes, pocket-books, gloves, etc.

Calf skins are made into upper leather for shoes. So are the skins of the goat. Sheep skins are very soft and made into leather for lining shoes. Sheep leather is also used for bags, book bindings, etc., for it is a leather that may be decorated with facility.
  1. As soon as the hide is removed from the animal carcass it isinspected for "take off" damage, such as cuts, scores and irregular pattern. Any defect thus noted is called to the attention ofthe butcher responsible for corrective measures on future hides.The hide is then promptly sent to the curing department by dropping it into a connection chute.
  2. On arrival there the hides are spread out on a platform, fleshaide up, for the trimming and grading operation. Excess fat andflesh are removed, and the ears, snout, lower lip and the longhair portion of the tail are cut off»
  3. The trimmed hides are then classified into various grades orselections such as steers or cows, heavy or light weight, brandedor native (free of brands), bulls, kips, etc. '.Then a sufficientnumber of a given selection has been accumulated they are countedand weighed. This weight is known as the "green" (uncured) weightand is the basis for calculation of the weight loss or "shrink"during cure. By this time the hide has lost much of its body heatand is ready for the curing operation.


Answer the following questions:

I.What is the classification of the coverings of animals?

2. What purposes are hides and skins used for?

3. Why are they treated before tanning?

4. In what conditions do the pelts of animals come to the tanner?
  1. What are pelts divided into?
  2. What sort of leather is obtained from hides and where is itused?
  3. What do kips and. skins yield?

8. Why is the hide inspected after removing from the animal carcass?

9. What are the trimmed hides classified into?


10. When is the hide ready for the curing operation?


Вариант II

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Preparation for tanning
  1. Damage by putrefaction, as well as damage from moths and othervermin, is a frequent happening in many countries leading to thereduction in quality of skins while leathers manufactured fromthese skins are of inferior quality. Putrefaction damage by microorganisms is the consequence of unsuitable or too-late-appliedconservation. The damage by macro-organisms (moths or vermin) isdue to insufficient protection of the skins during storage.
  2. Before discussing results obtained, it is necessary to mentionin this connection surface active substances which play a greatpart in to-day's tanning industry. These chemicals are used tohelp in soaking of hides, during liming, degreasing, dyeing, fatliquoring and as an additive in many types of leather finishes,etc.
  3. They do not assist the preservation process itself, but helpother chemicals which have bacteriostatic properties to penetratemore quickly into the skin. Thus a quicker and better conservationto obtained.
  4. Many changes occur in skins after the death of the animal. The process of changing the skin of animal into leather consists of three main stages: Preparation for tanning; Tanning; Finishing.
  5. Since skins are often transported some distance to the tanneries, they are given a preserving treatment by being either sun dried or treated with salt as soon as they are taken from the animal. This keeps them fresh until they arrive at the tannery.
  1. Hides and skins are brought to the tannery as usual in a curedcondition. Curing may be done by salting. Salt checks the bacterial action which would otherwise cause irrepairable damage. Whenskins are thoroughly cured, they are usually free from bacterialaction. But it mustn't be supposed that the concentrated salt solution stops the activity of all kinds of bacteria. Salt has atendency to drew water from the skin. It was found necessary toadd sodium chlorine to the salt to prevent stains.
  2. At the tannery skins are properly washed and cleaned. Thiscleaning is done in large washing machines. Water used for washingshould range between 50 and 68 . It should be free of organicmatter and iron salts that might stain the hides. The volume ofwater used for washing varies from tannery to tannery. The amountof water used for washing purposes varies from 0,5 to 2 gallonsper minute per pound of stock washed.
  3. However maximum flow of water is desired to hasten the removalof surface debries: thus reducing the possibility of cracking thegrain of dried-out portions of the hide and of flexing the fibersbefore they are properly wetted.
  4. To remove flesh and fat from the skins tanners use a fleshingmachine. Next operation is soaking which must be carried out withgreat care.

10. The skins are soaked in a lime solution to loosen the hair sothat it can be easily removed by the machine. This process iscalled unhairing or depilation. When the preliminary treatment isprovided the skins are ready for a conventional tanning process.

Answer the following questions:
  1. Why is it necessary to preserve skins against micro- end macro-organisms?
  2. What plays an important role in today's tanning industry?
  3. What do chemicals help in?
  4. What happens with the skins after the death of the animal?
  5. Can you name the stages of changing the skin into leather?
  6. When are the skins given preserving treatment?
  7. In what way is curing done?
  8. What is the process of washing and cleaning?
  9. What does a fleshing machine do?
  10. What is depilation?



Вариант III

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Tanning

1. Hides and skins having passed the preparation stage of tanningare not yet leather.

The series of processes by which the natural skins are converted into leather is broadly covered by the term "tanning". The purpose of tanning proper is to bring about changes of the skin properties preserving the hides from putrefaction.
  1. From the moment the hide (or skin) is removed from the animaluntil it is completely tanned, it is constantly in danger of attack by bacteria that are a form of plant life. Bacteria reactwith the protein matter in the hide, breaking it down. The hidebecomes foul-smelling and begins to rot. This is known as putrefaction. The chief purpose of tanning is to render the hide imputrescible, that is, resistant to putrefaction. It is the tannerwho converts the hide into enduring leather. Through every stagein the tanning process, the tanner must constantly take precautions to keep his stock free of harmful bacterial action, forthese injurious micro-organisms exist abundantly in every tanneryand present the greatest danger to the making of leather.
  2. When skins and hides arrive at the tannery they are generallydry and stiff, so first they are put into water to soften themand get rid of any salt that has been put on to preserve them.
  3. Next they are soaked in lime and water to loosen the hairs, sothat they are easily removed, the flesh aide of the skin is scrapedto remove anything that is not really part of the skin and willnot make leather. After being carefully washed in running waterthe skins are now ready for tanning.

5. Hides and skins tanned absorb certain properties of the agents with which they are tanned.

The tanning liquid is made with tannin : extract from vegetable material or tannin may be extracted from minerals.

6. The principles of converting animal skin into durable leather are practically unchanged from the early days of leather making history, though the actual tanning methods have changed much.

In the older days tanning was a very long process, but modern science has shortened it.

7. There are several methods of tanning, each producing a special type of leather with special characteristics: vegetable tanning, which produces a firm leather with excellent abrasive resistance - sole leather, belting leather, strap leather, harness leather, luggage leather, and light leathers for fancy. Leather goods are generally vegetable tanned. Chrome tanning is used mainly for upper leather for shoes, for gloving, and for fancy leather goods where water-resistance or softness is a desirable quality; some sole leather is also chrome-tanned. Oil tanning is used principally in the manufacture of "chamois". Alum tanning is used mainly for white leather. Combination tanning, which consists generally of vegetable tanning in combination with one of the mineral tannages, usually chrome, to combine in the finished leather some of the characteristics of both tannages, as in upper aide leather for shoes. Of these the two most important are vegetable tanning and chrome tanning.

Answer the following questions:
  1. What does the term "tanning" mean?
  2. What is the chief purpose of tanning?
  3. Why are hides and skins put into water when they arrive atthe tannery?
  4. When are skins and hides ready for tanning?
  5. What do hides and skins absorb?
  6. What is the tanning liquid made with?
  7. What changed tanning methods?
  8. Can you name methods of tanning?
  9. What are the two most important methods?10. What method is used for white leather?


Вариант IV

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Finishing Operations
  1. Upon removal from the layer vats, the actual conversion of raw,hide substance into leather is complete. But at this stage theleather would be so crude and unattractive as to limit its usegreatly. Nor would it have sufficient tensile or flexural strengthto serve well in the manifold purposes for which it is used. Thefinishing steps that follow are numerous, and of great importancein transmuting a harsh stiff material into the beautiful finishedleather we recognize in our products. These steps vary greatly insequence depending upon the type of leather to be made. We shalllimit ourselves to a brief exposition of the more important finishing processes common to most cattlehide leathers.
  2. Bleachings. To secure a uniform color penetration in a subsequent operation - that of dyeing or coloring - the leather isbleached. This done by dipping the stock for a short period firstin a weak alkali solution, then in a weak acid solution, afterwhich the stock is washed and put through a wringer.
  3. Stuffings. The stock is still harsh and stiff; under flexing,the leather would crack. To impart flexibility and wear resistance the leather, while still wet to some extent, is placed into alarge heated drum. As this drum revolves, hot oils and greasersare introduced. This lubricates the fibers and imparts flexibility. Now the leather is dried slowly, and then it may be stuffed a second time.
  1. Coloring. To impart a suitable color, the leather must bestained or dyed. Dyeing is done in a rotating drum. The coloringmatter is put in solution in a drum which, as it revolves, forcesthe dye into the leather.
  2. Staking. To separate the fibres sticking together, and to makethe leather flexible and supple, it is "staked". It is entirelyan operation done on a staking machine. The leather, while damp,Is kept moving through the jaws of the machine, the lower jaw orroller gripping the leather, while the upper jaw exerts a violentmechanical action, stretching and flexing the leather, and hencesoftening it.

6. Fat-liquoring. After staining or coloring, the leather is placed in a heated drum with an emulsion of soaps and oils to lubricate the fibres and prevent cracking of the grain surface. It is then set out by machine to squeeze out excess water and to remove wrinkles.

7. Sammying. Leather stored in the "crust" must be treated before it can be processed to restore to the hide substance an adequate water or moisture content. The leather is "sammied" by dipping into warm water and then piling it in damp sawdust until it absorbs a considerable amount of moisture. Following "summing" the leather is staked, set out "toggled". Toggling consists in attaching the leather to a perforated metal frame by means of spring clamps or toggles. It is then introduced into a drying room or drying tunnel with controlled temperature and humidity. Here it remains until it is thoroughly dry and firm. Upon removal from the drying room the leather is ready for the final finishing operations.

These final operations are numerous and depend in large part upon the type of finished leather required.

Answer the following questions:
  1. When is the conversion of hide leather complete?
  2. What would the leather look like at this stage?
  3. What does it need to become the beautiful finished leather?
  4. Why is the leather bleached?
  5. Рог what purpose is the leather placed into a large drum?
  6. How is colouring done?
  7. What is "staking"?
  8. What happens with the leather in a heated drum?
  9. In what way is the leather "sammied"?
  10. What do these final operations depend upon?


Вариант V


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What is Fur ?

1. When assorting and valueing fur three factors must be takeninto consideration: quality, size, and colour.

2. Quality. The colder temperatures require a heavy, thick growthof hair and fur to protect the animal against the harsh weatherthat it encounters. The animal cannot obtain its food readily in the cold weather; therefore, in winter the fat that has been accumulated during the warmer weather is used up with the result that skin or pelt becomes very thin. In the warmer climates animals find their food easily. The result is a thicker pelt, shorter hair and fur that is scant and thin.
  1. Hind that carnivorous animals do not take the same sort of dressing processes as do those that are herbivorous. Consequently, twoprocesses of dressing must be worked out because of the differencein the skin content between peltries of wild and domestic animals.
  2. In all peltries except those of the Water Rodents, the qualitiesare summarized in four grades, which are termed Ones, Twos, Threes,and Fours. Sometimes the words Firsts, Seconds, Thirds, andFourths are used meaning respectively the same thing. These termsrepresent the fact that the first grade is the best; the secondgrade next best and so on. At times a grade called Fifths is addedand expresses that the peltries are trash or of no value. First-grade peltries or Ones must primarily be prime in pelt, and thenfull furred.
  3. "Prime in pelt" refers to a condition that is found at theheight of the cold weather, if it is also dry: in other words,the coldest and driest time of the year. The skin is then freefrom any discoliratione, either blueish or reddish, both of whichare indication of unprimed quality. "Full furred", as the term indicates, means that the peltry has a full and thick covering offur fiber. This thick fur fiber causes the guard hair to standerect and to give the general appearance of the peltry.
  4. Size. The colder climates produce larger animals of a particular species than do the warmer climates. Only animals of greatstrength and size can survive the extreme cruelty of the climate;the weaker ones rapidly succumb. Note carefully that, although wehave large animals in the north and large animals in the south,the small animals in both the north and south, animals of the samespecies are larger in the north than in the south, for example,the Muskrat. There are four basic sizes: Extra Large, Large, Medium, and Small. These are abbreviate*!, Ex. L. or XL., L. or Lge.,M. or bled., and S. or Sm. These sizes are applicable to all typesof peltries.

Colour. The snow and ice of the north cause a change in thecolour pigment content of the hair covering on most animals. Thelark marshlands, the rivers, and the thick-growing, shady plantlife of the south, however, have the opposite effect. Here the hair covering Is of a darker shade, usually some shade of brown. Brown, in its various shades, is the principal colour factor that comes up for consideration when the value of certain peltries is determined; but, where colour is used to determine quality only, the. explanation of its use will be found under the individual species of peltry which is being considered. Brown is usually divided into three shades: Brown, Pale and Reddish or Off Colour. Gray, the next leading colour, as well as the other colours cannot be generalized as can the Browns. They are matters for determination in certain peltries only, and can be best explained under the respective species involved.

8. Before proceeding further, it should be noted that, in the matter of colour, the females are usually of a darker shade than the males, and also that the females are smaller; hence, we deduce the fact that the smaller peltries usually contain the dark colours.

Answer the following questions:

I. What factors must be taken into consideration speaking

about furs?

2. What do the colder temperatures require?
  1. What happens with the fur of the animals in summer?
  2. Are dressing processes the same for carnivorous and herbivorous animals?
  3. What do grades represent?
  4. What does "Prime in pelt" refer to?
  5. Why are animals larger in size in the colder climates?
  6. What causes a change in the colour of the hair covering onmost animals?
  7. What produces the opposite effect?

10. What colour is the principal factor when the value of certainpeltries is determined?


Контрольное задание № 4


для студентов специальности "Химтехнология и оборудование отделочного производства"

Вариант I

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Methods of Dry-Gleaning

■

I. The basis of dry-cleaning is the treatment of soiled textiles with an organic solvent, thereby avoiding difficulties caused by the use of water in washing, particularly those associated with the swelling action of water in textiles, e.g. shrinkage, colour ' Loss, distortion and loss of shape.

2. The solvent acts primarily by dissolving fatty matter thus permit ing the release and removal of soil bound by a film of oil and of soil that Is only loosely attached to the surface of the fabric. Only two solvents, perchloroethylene and white spirit, meet these requirements to permit their general industrial use.

3. Perchlorethylene which until a few years ago found little use 1b now the predominant dry-cleaning solvent. The various inflatable solvents used previously, e.g. benzol, solvent naphtha, benzine have been replaced by white spirit and now white spirit is being replaced by perchloroethylene.

4. The relative ease of recovery of solvent and the fact that it in not inflammable and can be used automatically in operated machines favour this tendency. In the dry-cleaning industry old machines which used white spirit are being replaced by modern machines in which perchloroethylene is used. Although the replacement white spirit by perchloroethylene will continue, it is unlikely that white spirit will be replaced completely in the future.

5. At present approximately 75 per cent of all dry-cleaning is carried out with perchloroethylene and approximately 20 per cent with white spirit, while no more than 5 per cent is cleaned with trichloroethylene.