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Wood and a paper

the Science and technics
 
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More often the person uses wood as fuel. However value of wood as natural riches and widely applied raw materials is defined by wood and paper manufacture.

Demand for wood is always high - with the help are sharp to it easily to give the necessary form, details from a tree without effort join to each other, and products from it well look.


Firm and soft wood

Wood happens two principal views - firm and soft. Soft wood is given by coniferous trees: a pine, a fur-tree, a fir, tsuga, a sequoia. On manufacture of firm wood go such shirokolistvennye tree species, as a beech, a birch, a maple, an oak and a poplar. In tropics firm wood receive from black ebenovogo a tree, different kinds of mahogany, a tic and other valuable breeds. Beautifully looking firm wood always was in the big honour at manufacturers and buyers of furniture. Unfortunately, trees of firm breeds grow slowly, and in their rainforests becomes ever less.


wood Preparation

wood Preparation Usually trees bring down by means of powerful circular saws, then trunks release from branches and bring on places of processing for the further transportation. The diversified technics - cranes, catarpillars, bulldozers will thus be involved. If wood is subject to transportation overland, its cranes load on wheel transport, though in India and Burma for taski the cut trees just as in olden days, use elephants.

wood Preparation In some regions wood is easier for alloying on the rivers: the cut trees stack in rafts and push together on water by means of cranes. Then hundreds such rafts connect together and tow to sorting and marks points. In the remote areas where on the rivers there is no navigation, logs simply alloy downstream - up to destination.

In many countries - and in particular where prepare firm breeds of wood, - are not present own capacities for raspilki wood. Hence, the most part of the prepared wood is taken out to industrially developed countries in the form of logs on derevoobrabatyvajushchie industrial complexes.

On timber mill the log, first of all, is cleared of a bark, and then by mechanical saws is cut on preparations of the necessary sizes. At this stage of processing wood still contains zhivitsu and demands preliminary drying. Natural drying is possible, but takes away about a year of time and consequently wood usually arrives on fast drying in special lesosushilki. As a result of such artificial drying, or keeping, occurs usazhivanie and sometimes even koroblenie wood. Thus, wood should go for processing only after full drying when it if only again will not get wet, gets relative firmness.

Pilenye forest products without the further processing are subject to use in building, and wooden surfaces which will be in the public eye, operational development will demand. Quite often bars start up on longitudinal razrezku, with painting or a prograss of boards. The most attractive wood is cut on very thin sheets - a facing interline interval which then is pasted on a basis from wood easier.

Plywood consists of the several sheets of the wood which have been stuck together so that a fibre of the next sheets formed a right angle. The plywood sheet is much stronger than the sheet of the same sizes manufactured from usual wood. Plywood is much more difficult for bending and splitting; the probability koroblenija is insignificant.

In derevoobrabatyvajushchej the industry there are not enough waste - the person has found application of all. Rejki from poor quality wood place between sheets of good wood and make a joiner's plate, and remaining skrap turns to sawdust, it is processed by glue and it is pressed in DSP - drevesnostruzhechnuju a plate.


Raw materials for a paper

Wood cellulose is the basic raw materials for paper manufacture though instead of it other kinds of a vegetative fibre also can be used. Cellulose receive from the most different firm and soft wood breeds: fur-trees, pines, evkalipta, a poplar, a birch, a chestnut and other trees.

The Most economic way of reception of wood cellulose - mechanical: on derevoobrabatyvajushchem the enterprise forest products are crushed to a crumb which mixes up with water. The paper made of such cellulose, is fragile and more often goes on manufacture, for example, newspapers.

More quality Paper do of the cellulose received in the chemical way: the wooden bar is cut on small shchepy which plunge into a chemical solution and heat up under pressure. Of such wood pulp make a paper for books, brochures and fashionable magazines, and also strong wrapping materials.


Manufacturing

On derevopererabatyvajushchem the enterprise for removal of impurity cellulose is washed out and filtered. The cellulose intended for manufacturing of a white paper, in addition is subject vybelke. After that it turns to sheet and dries that subsequently will facilitate process of manufacture of a paper. The sheet in bales arrives on pulp-and-paper industrial complex where the special car named razryvatelem of cellulose, rips up sheets and mixes them with water. Frequently cooking of cellulose and manufacture from it pass papers in a continuous mode, without intermediate drying.

To the processed paper weight the paper for recycling, but only after removal of ink can be added. At this production phase the processed weight consisting of wood fibres and water, is called as paper raw materials.

Then by the special processing car the form and structure of paper fibres - according to requirements to which the made paper should answer vary. At a following stage the paper weight mixes up with other substances, setting to an end-product desirable properties.

Glues are the substances which presence at a writing paper pushes away a moisture. For prokleivanija papers are used pitches more often. Thanking it, written on a paper the ink prepared on a water basis, does not spread and it is easily distinguished by a human eye. The paper used for printing, does not demand such prokleivanija as writing as printing paints prepare not on a water basis and do not spread. After that a paper paint in the amalgamator where add dyes or pigments, - for example, small crushed substances for melovanija. So, additives kaolina do a paper white and opaque. The most widespread way of manufacturing of a paper is the method of Furdrine. From a mixer the paper weight through the cylinder moves on the conveyor which tape represents a grid with cells; the width of this tape can reach 9 metres. The conveyor moves with a speed to 1000 m a minute. The thickness and weight of a paper descending from the conveyor depends on speed of receipt of raw materials.


Watermarks

In process of advancement of paper weight on the tape conveyor the part of water containing in it follows through cellular apertures, and paper fibres start to be weaved with each other, forming a so-called rolled tape. Before it will descend from the conveyor, fibres leaves even more waters - for the account vsasyvanija a moisture from below. Right now on paper fibres it is possible to put a watermark. The special platen with beforehand set drawing for this purpose is required. Further the tape will arrive on the moving belt conveyor from natural felt, and will pass through a little consistently located heavy valkov which will squeeze out from a paper of even more moisture and will even more strongly press its fibres. Then the paper tape which has reached to sufficient durability to move in itself, will round some the metal drums warmed up by steam which will evaporate from a tape almost all remaining to a moisture After drying a paper will pass through slightly rowed and faultlessly ground iron cylinders named kalandrami which will smooth its surface. After that a paper wind on reels which can be cut on smaller coils. Then the paper is cut on sheets.


surface Furnish

For giving to a paper or a cardboard of the kind necessary for this or that concrete application, there is a set of methods of furnish. For example, the high-quality paper becomes covered by the most thin layer of the crushed white dye which can be or kaolin, or "ьр=ютр  схышчэр" - a mix okisi aluminium and calcium sulphate. Dye keeps on a paper thanks to special gluing substance is an or dairy fiber casein, or polivinilatsetat, more known as PVA. Dye fills minute pores in a surface of a paper and gives it smoothness and characteristic luster.

Sometimes a paper and a cardboard process paraffin: the wax paper pushes away water. One their technological this sort of processes provides paper passage through capacity with the fused wax. Special are shaky clean off superfluous wax stratifications, and remaining wax hardens under a stream of cold water. If on such paper it is necessary to print, make something it follows to voshchenija as proparafinennaja the surface will not absorb a paint.

Other technology voshchenija papers assumes an initial covering wax only one party of sheet then another, the yet not processed surface moves on razogretyj a drum. Its heat plavit wax; the fused wax is absorbed by paper fibres. On the paper processed in such a way the subsequent press is possible. Basically the paper is made from the wood prepared in woods of the North America, Scandinavia, Russia, Japan and Germany. The small part of bumazhno-raw weight is made from straw and separate grassy plants, as, for example, esparto or albardin. Paper money usually makes of cotton weight or from a mix hlopchatyh and linen fibres. In many developing countries aspire to use local resources and alternative raw materials. For example, after extraction of sugar from reed cultures there is a fibrous oil cake, and its industrial use in the countries where cultivate a sugar cane, will allow to refuse import of a paper or raw materials for paper weight.


Whether

you Know?

  • the First paper was made by ancient Chineses. The secret of manufacturing of a paper to them was prompted by wasps and shershni which chew wood crumbs and build of this sticky weight the nests.
  • In printing the paper is measured in grammes on m 2
  • the Paper on which our magazine is printed, has density 90 g/m 2 .
  • From the economic point of view manufacture of a paper from a waste is more expensive, than its manufacturing from wood.