Pulp message. Cellulose formula

Cellulose is a derivative of two natural substances: wood and cotton. In plants it carries out important function, gives them flexibility and strength.

Where is the substance found?

Cellulose is a natural substance. Plants are able to produce it on their own. Contains: hydrogen, oxygen, carbon.

Plants produce sugar when exposed to sun rays, it is processed by cells and enables the fibers to withstand high wind loads. Cellulose is a substance involved in the process of photosynthesis. If you sprinkle sugar water on a cut of fresh wood, the liquid will quickly be absorbed.

Cellulose production begins. This natural method of obtaining it is taken as the basis for the production of cotton fabric on an industrial scale. There are several methods by which pulp of varying quality is obtained.

Manufacturing method No. 1

Cellulose is produced natural method- from cotton seeds. Hairs are collected by automated mechanisms, but it is required a long period growing a plant. Fabric produced in this way is considered the purest.

Cellulose can be obtained more quickly from wood fibers. However, with this method the quality is much worse. This material is only suitable for the production of non-fiber plastic, cellophane. Artificial fibers can also be produced from such material.

Natural Receipt

The production of cellulose from cotton seeds begins with the separation of long fibers. This material is used to make cotton fabric. Small parts, less than 1.5 cm, are called

They are suitable for producing cellulose. The assembled parts are heated under high pressure. The duration of the process can be up to 6 hours. Before heating the material, sodium hydroxide is added to it.

The resulting substance must be washed. For this purpose, chlorine is used, which also bleaches. The cellulose composition with this method is the purest (99%).

Manufacturing method No. 2 from wood

To obtain 80-97% of cellulose, coniferous tree chips are used, chemical substances. The whole mass is mixed and subjected to temperature treatment. As a result of cooking, the required substance is released.

Calcium bisulfite, sulfur dioxide and wood pulp are mixed. Cellulose in the resulting mixture is no more than 50%. As a result of the reaction, hydrocarbons and lignins dissolve in the liquid. Hard material goes through the purification stage.

The result is a mass reminiscent of low-quality paper. This material serves as the basis for the manufacture of substances:

• Ethers.
• Cellophane.
• Viscose fiber.

What is produced from valuable material?

It is fibrous, which allows it to be used to make clothing. Cotton material is a 99.8% natural product obtained using the natural method described above. It can also be used to make explosives as a result chemical reaction. Cellulose is active when acids are applied to it.

The properties of cellulose are applicable to the production of textiles. So, artificial fibers are made from it, reminiscent of natural fabrics in appearance and touch:

• viscose and;
• artificial fur;
• copper-ammonia silk.

Mainly made from wood cellulose:

• varnishes;
• photographic film;
• paper products;
• plastics;
• sponges for washing dishes;
• smokeless powder.

As a result of a chemical reaction from cellulose, the following is obtained:

• trinitrocellulose;
• dinitrofiber;
• glucose;
• liquid fuel.

Cellulose can also be used in food. Some plants (celery, lettuce, bran) contain its fibers. It also serves as a material for the production of starch. They have already learned how to make thin threads from it - artificial spider web is very strong and does not stretch.

The chemical formula of cellulose is C6H10O5. Is a polysaccharide. It is made from:

• medical cotton wool;
• bandages;
• tampons;
• cardboard, chipboard;
• food additive E460.

Advantages of the substance

Cellulose can withstand high temperatures up to 200 degrees. The molecules are not destroyed, which makes it possible to make reusable plastic dishes from it. At the same time, an important quality is preserved - elasticity.

Cellulose can withstand prolonged exposure to acids. Absolutely insoluble in water. Not digestible human body, is used as a sorbent.

Microcrystalline cellulose is used in alternative medicine as a drug to cleanse the digestive system. Powdery substance acts as a food additive to reduce the calorie content of consumed dishes. This helps remove toxins, reduce blood sugar and cholesterol.

Manufacturing method No. 3 - industrial

At production sites, cellulose is prepared by boiling in different environments. The material used—the type of wood—depends on the type of reagent:

• Resinous rocks.
• Deciduous trees.
• Plants.

There are several types of cooking reagents:

• Otherwise, the method is referred to as sulfite. The solution used is a salt of sulfurous acid or its liquid mixture. In this production option, cellulose is isolated from coniferous species. Fir and spruce are processed well.
• The alkaline medium or soda method is based on the use of sodium hydroxide. The solution effectively separates cellulose from plant fibers (corn stalks) and trees (mainly deciduous trees).
• The simultaneous use of sodium hydroxide and sodium sulfide is used in the sulfate method. It is widely used in white liquor sulfide production. Technology is quite negative for surrounding nature due to the resulting third-party chemical reactions.

The last method is the most common because of its versatility: cellulose can be obtained from almost any tree. However, the purity of the material is not entirely high after one cooking. Impurities are removed by additional reactions:

• hemicelluloses are removed with alkaline solutions;
• lignin macromolecules and the products of their destruction are removed with chlorine followed by treatment with alkali.

The nutritional value

Starch and cellulose have a similar structure. As a result of experiments, it was possible to obtain a product from inedible fibers. A person needs it constantly. The food consumed consists of more than 20% starch.

Scientists have managed to obtain the substance amylose from cellulose, which has a positive effect on the condition of the human body. At the same time, glucose is released during the reaction. The result is a waste-free production - the last substance is sent for the production of ethanol. Amylose also serves as a means of preventing obesity.

As a result of the reaction, the cellulose remains in a solid state, settling to the bottom of the vessel. The remaining components are removed using magnetic nanoparticles or dissolved and removed with the liquid.

Types of substance on sale

Suppliers offer pulp different quality at reasonable prices. We list the main types of material:

• Sulfate cellulose is white in color, produced from two types of wood: coniferous and deciduous. There is unbleached material used in packaging material, low quality paper for insulation and other purposes.
• Sulfite is also available in white, made from coniferous trees.
• The white powder material is suitable for the production of medical substances.
• Premium grade pulp is produced by bleaching without chlorine. Coniferous trees are used as raw materials. Wood pulp consists of a combination of spruce and pine chips in a ratio of 20/80%. The purity of the resulting material is the highest. It is suitable for the production of sterile materials used in medicine.

To select a suitable cellulose, standard criteria are used: material purity, tensile strength, fiber length, tear resistance index. Also quantified chemical state or the aggressiveness of the water extract environment and humidity. For cellulose supplied in the form of bleached pulp, other indicators are applicable: specific volume, brightness, grinding size, tensile strength, degree of purity.

An important indicator for the mass of cellulose is the tear resistance index. The purpose of the materials produced depends on it. Take into account the raw material used and humidity. The level of tars and fats is also important. Powder uniformity is important for certain processes. For similar purposes, the viscosity and compressive strength of the material in the form of sheets are assessed.

All our lives we are surrounded by a huge number of objects - cardboard boxes, offset paper, plastic bags, viscose clothing, bamboo towels and much more. But few people know that cellulose is actively used in their production. What is this truly magical substance, without which almost no modern industrial enterprise? In this article we will talk about the properties of cellulose, its use in various fields, as well as what it is extracted from, and what it is chemical formula. Let's start, perhaps, from the beginning.

Substance detection

The formula for cellulose was discovered by the French chemist Anselme Payen during experiments on separating wood into its components. After treating it with nitric acid, the scientist discovered that during the chemical reaction a fibrous substance similar to cotton was formed. After careful analysis of the resulting material, Payen obtained the chemical formula of cellulose - C 6 H 10 O 5. A description of the process was published in 1838, and the substance received its scientific name in 1839.

Gifts of nature

It is now known for certain that almost all soft parts of plants and animals contain some amount of cellulose. For example, plants need this substance for normal growth and development, or more precisely, for the creation of the membranes of newly formed cells. In composition it belongs to polysaccharides.

In industry, as a rule, natural cellulose is extracted from coniferous and deciduous trees - dry wood contains up to 60% of this substance, as well as by processing cotton waste, which contains about 90% cellulose.

It is known that if wood is heated in a vacuum, that is, without air access, thermal decomposition of cellulose occurs, resulting in the formation of acetone, methyl alcohol, water, acetic acid and charcoal.

Despite the rich flora of the planet, there are no longer enough forests to produce the amount of chemical fibers required for industry - the use of cellulose is too extensive. Therefore, it is increasingly extracted from straw, reeds, corn stalks, bamboo and reeds.

Synthetic cellulose is produced from coal, oil, natural gas and shale using various technological processes.

From the forest to the workshops

Let's look at the extraction of technical cellulose from wood - this is a complex, interesting and lengthy process. First of all, wood is brought to production, cut into large fragments and the bark is removed.

The cleaned bars are then processed into chips and sorted, after which they are boiled in lye. The resulting cellulose is separated from the alkali, then dried, cut and packaged for shipment.

Chemistry and physics

What chemical and physical secrets are hidden in the properties of cellulose besides the fact that it is a polysaccharide? First of all, it is a white substance. It ignites easily and burns well. It dissolves in complex compounds of water with hydroxides of some metals (copper, nickel), with amines, as well as in sulfuric and orthophosphoric acids, a concentrated solution of zinc chloride.

Cellulose does not dissolve in available household solvents and ordinary water. This happens because the long thread-like molecules of this substance are connected in peculiar bundles and are located parallel to each other. In addition, this entire “structure” is strengthened by hydrogen bonds, which is why molecules of a weak solvent or water simply cannot penetrate inside and destroy this strong plexus.

The thinnest threads, the length of which ranges from 3 to 35 millimeters, connected into bundles - this is how you can schematically represent the structure of cellulose. Long fibers are used in the textile industry, short fibers are used in the production of, for example, paper and cardboard.

Cellulose does not melt or turn into steam, but it begins to decompose when heated above 150 degrees Celsius, releasing low molecular weight compounds - hydrogen, methane and carbon monoxide (carbon monoxide). At temperatures of 350 o C and above, cellulose becomes charred.

Change for the better

This is how chemical symbols describe cellulose, the structural formula of which clearly shows a long-chain polymer molecule consisting of repeating glucosidic residues. Note the "n" indicating a large number of them.

By the way, the formula for cellulose, derived by Anselm Payen, has undergone some changes. In 1934, the English organic chemist, laureate Nobel Prize Walter Norman Haworth studied the properties of starch, lactose and other sugars, including cellulose. Having discovered the ability of this substance to hydrolyze, he made his own adjustments to Payen’s research, and the cellulose formula was supplemented with the value “n”, indicating the presence of glycosidic residues. On this moment it looks like this: (C 5 H 10 O 5) n.

Cellulose ethers

It is important that cellulose molecules contain hydroxyl groups, which can be alkylated and acylated, forming various esters. This is another one of the most important properties that cellulose has. The structural formula of various compounds may look like this:

Cellulose ethers are either simple or complex. Simple ones are methyl-, hydroxypropyl-, carboxymethyl-, ethyl-, methylhydroxypropyl- and cyanoethylcellulose. Complex ones are nitrates, sulfates and cellulose acetates, as well as acetopropionates, acetylphthalylcellulose and acetobutyrates. All these ethers are produced in almost all countries of the world in hundreds of thousands of tons per year.

From photographic film to toothpaste

What are they for? As a rule, cellulose ethers are widely used for the production of artificial fibers, various plastics, all kinds of films (including photographic), varnishes, paints, and are also used in the military industry for the production of solid rocket fuel, smokeless powder and explosives.

In addition, cellulose ethers are included in plaster and gypsum-cement mixtures, fabric dyes, toothpastes, various adhesives, synthetic detergents, perfumes and cosmetics. In a word, if the cellulose formula had not been discovered back in 1838, modern people would not have many of the benefits of civilization.

Almost twins

Few of them ordinary people knows that cellulose has a kind of twin. The formula of cellulose and starch is identical, but these two are completely different substances. What's the difference? Despite the fact that both of these substances are natural polymers, the degree of polymerization of starch is much less than that of cellulose. And if you delve further and compare the structures of these substances, you will find that cellulose macromolecules are arranged linearly and only in one direction, thus forming fibers, while starch microparticles look slightly different.

Areas of application

One of the best visual examples of practically pure cellulose is ordinary medical cotton wool. As you know, it is obtained from carefully purified cotton.

The second, no less used cellulose product is paper. In fact, it is a thin layer of cellulose fibers, carefully pressed and glued together.

In addition, viscose fabric is produced from cellulose, which, under the skillful hands of craftsmen, magically turns into beautiful clothes, upholstery for upholstered furniture and various decorative draperies. Viscose is also used for the manufacture of technical belts, filters and tire cords.

Let's not forget about cellophane, which is made from viscose. It’s hard to imagine supermarkets, shops, and packaging departments without it. post offices. Cellophane is everywhere: candy is wrapped in it, cereals are packed in it, bakery products, as well as tablets, tights and any equipment, from a mobile phone to a remote control remote control for TV.

In addition, pure microcrystalline cellulose is included in weight loss tablets. Once in the stomach, they swell and create a feeling of fullness. The amount of food consumed per day is significantly reduced, and accordingly, weight falls.

As you can see, the discovery of cellulose produced a real revolution not only in chemical industry, but also in medicine.

Cellulose is a polysaccharide built from elementary units of anhydro- D -glucose and representing poly-1, 4-β - D -glucopyranosyl- D -glucopyranose. The cellulose macromolecule, along with anhydroglucose units, may contain residues of other monosaccharides (hexoses and pentoses), as well as uronic acids (see figure). The nature and quantity of such residues are determined by the conditions of biochemical synthesis.

Cellulose is the main component cell walls of higher plants. Together with the substances accompanying it, it plays the role of a frame bearing the main mechanical load. Cellulose is found mainly in the hairs of the seeds of some plants, for example, cotton (97-98% cellulose), wood (40-50% on a dry matter basis), bast fibers, inner layers of plant bark (flax and ramie - 80-90% , jute - 75% and others), stems of annual plants (30-40%), for example, reeds, corn, cereals, sunflowers.

Isolation of cellulose from natural materials based on the action of reagents that destroy or dissolve non-cellulose components. The nature of processing depends on the composition and structure of the plant material. For cotton fiber (non-cellulose impurities - 2.0-2.5% nitrogen-containing substances; about 1% pentosans and pectin substances; 0.3-1.0% fats and waxes; 0.1-0.2% mineral salts) use relatively mild extraction methods.

Cotton fluff is subjected to a park (3-6 hours, 3-10 atmospheres) with a 1.5-3% solution sodium hydroxide followed by washing and bleaching with various oxidizing agents - chlorine dioxide, sodium hypochlorite, hydrogen peroxide. Some polysaccharides with low molar weight (pentosans, partially hexosans), uronic acids, and some fats and waxes pass into the solution. Contentα -cellulose (fraction insoluble in 17.5% solution N aOH at 20° for 1 hour) can be increased to 99.8-99.9%. As a result of partial destruction of the morphological structure of the fiber during cooking, the reactivity of cellulose increases (a characteristic that determines the solubility of esters obtained during the subsequent chemical processing of cellulose and the filterability of spinning solutions of these esters).

To isolate cellulose from wood containing 40-55% cellulose, 5-10% other hexosans, 10-20% pentosans, 20-30% lignin, 2-5% resins and a number of other impurities and having a complex morphological structure, more rigid processing conditions; Most often, sulfite or sulfate cooking of wood chips is used.

During sulfite cooking, wood is treated with a solution containing 3-6% free SO 2 and about 2% SO 2 , bound in the form of calcium, magnesium, sodium or ammonium bisulfite. Cooking is carried out under pressure at 135-150° for 4-12 hours; Cooking solutions during acid bisulfite cooking have a pH from 1.5 to 2.5. During sulfite cooking, lignin is sulfonated, followed by its transition into solution. At the same time, part of the hemicelluloses is hydrolyzed, the resulting oligo- and monosaccharides, as well as part of the resinous substances, dissolve in the cooking liquor. When using cellulose isolated by this method (sulfite cellulose) for chemical processing (mainly in the production of viscose fiber), the cellulose is subjected to refining, the main task of which is to increase the chemical purity and uniformity of cellulose (removal of lignin, hemicellulose, reduction of ash content and resin content, change in colloidal chemical and physical properties). The most common refining methods are treating bleached cellulose with a 4-10% solution N aOH at 20° (cold refining) or 1% solution NaOH at 95-100° (hot refining). Refined sulfite cellulose for chemical processing has the following indicators: 95-98%α -cellulose; 0.15--0.25% lignin; 1.8-4.0% pentosans; 0.07-0.14% resin; 0.06-0.13% ash. Sulfite cellulose is also used for the production of high-quality paper and cardboard.

Wood chips can also be cooked with 4- 6% N solution aOH (soda cooking) or its mixture with sodium sulfide (sulphate cooking) at 170-175° under pressure for 5-6 hours. In this case, lignin is dissolved, part of the hemicelluloses (mainly hexosans) are transferred into solution and hydrolyzed, and the resulting sugars are further converted into organic hydroxy acids (lactic, saccharic and others) and acids (formic). Resin and higher fatty acid gradually pass into the cooking liquor in the form of sodium salts (the so-called"sulfate soap"). Alkaline cooking is applicable for processing both spruce, pine and deciduous wood. When using cellulose (sulfate cellulose) isolated by this method for chemical processing, the wood is subjected to pre-hydrolysis (treatment with dilute sulfuric acid at elevated temperatures) before cooking. Pre-hydrolysis kraft pulp used for chemical processing, after refining and bleaching, has the following average composition (%):α -cellulose - 94.5-96.9; pentosans 2-2, 5; resins and fats - 0.01-0.06; ash - 0.02-0.06. Sulfate cellulose is also used for the production of sack and wrapping papers, paper ropes, technical papers (bobbin, emery, condenser), writing, printing and bleached durable papers (drawing, cartographic, for documents).

Sulphate cooking is used to produce high-yield cellulose, used for the production of corrugated cardboard and sack paper (the yield of cellulose from wood in this case is 50-60% versus~ 35% for pre-hydrolysis kraft pulp for chemical processing). High yield cellulose contains significant amounts of lignin (12-18%) and retains its chip shape. Therefore, after cooking, it is subjected to mechanical grinding. Soda and sulphate cooking can also be used to separate cellulose from straw containing large quantities SiO2 , removed by the action of alkali.

Cellulose is also isolated from deciduous wood and annual plants by hydrotropic cooking - processing the raw materials with concentrated (40-50%) salt solutions alkali metals and aromatic carbonic and sulfonic acids (for example, benzoic, cymene and xylene sulfonic acids) at 150-180° for 5-10 hours. Other methods of cellulose isolation (nitric acid, chlor-alkali and others) are not widely used.

To determine the molar weight of cellulose, a viscometric method is usually used [by the viscosity of cellulose solutions in a copper-ammonium solution, in solutions of quaternary ammonium bases, cadmium ethylenediamine hydroxide (the so-called cadoxene), in alkaline solution ferric acid sodium complex and others, or by the viscosity of cellulose ethers - mainly acetates and nitrates obtained under conditions excluding destruction] and osmotic (for cellulose ethers) methods. The degree of polymerization determined using these methods is different for different cellulose preparations: 10-12 thousand for cotton cellulose and bast fiber cellulose; 2.5-3 thousand for wood cellulose (according to determination in an ultracentrifuge) and 0.3-0.5 thousand for viscose silk cellulose.

Cellulose is characterized by significant polydispersity in molar weight. Cellulose is fractionated by fractional dissolution or precipitation from a copper-ammonia solution, from a solution in cupriethylenediamine, cadmiumethylenediamine or in an alkaline solution of sodium ferrous acid complex, as well as fractional precipitation from solutions of cellulose nitrates in acetone or ethyl acetate. Cotton cellulose, bast fibers and softwood wood pulp are characterized by molar weight distribution curves with two maxima; the curves for hardwood pulp have one maximum.

Cellulose has a complex supramolecular structure. Based on X-ray diffraction, electron diffraction and spectroscopic studies, it is usually accepted that cellulose is a crystalline polymer. Cellulose has a number of structural modifications, the main of which are natural cellulose and hydrated cellulose. Natural cellulose is converted into hydrated cellulose upon dissolution and subsequent precipitation from the solution, under the action of concentrated alkali solutions and subsequent decomposition alkaline cellulose and others. The reverse transition can be carried out by heating cellulose hydrate in a solvent that causes its intense swelling (glycerin, water). Both structural modifications have different X-ray diffraction patterns and differ greatly in reactivity, solubility (not only of cellulose itself, but also of its esters), adsorption capacity and others. Cellulose hydrate preparations have increased hygroscopicity and paintability, as well as a higher rate of hydrolysis.

The presence of acetal (glucosidic) bonds between the elementary units in the cellulose macromolecule determines its low resistance to the action of acids, in the presence of which cellulose hydrolysis occurs (see figure). The speed of the process depends on a number of factors, of which the decisive factor, especially when carrying out the reaction in a heterogeneous environment, is the structure of the drugs, which determines the intensity of intermolecular interaction. In the initial stage of hydrolysis, the rate may be higher, which is associated with the possibility of the existence in the macromolecule large number bonds that are less resistant to the action of hydrolyzing reagents than conventional glucosidic bonds. The products of partial hydrolysis of cellulose are called hydrocellulose.

As a result of hydrolysis, the properties of cellulose material change significantly - the mechanical strength of the fibers decreases (due to a decrease in the degree of polymerization), the content of aldehyde groups and solubility in alkalis increases. Partial hydrolysis does not change the resistance of the cellulose preparation to alkaline treatments. The product of complete hydrolysis of cellulose is glucose. Industrial methods for the hydrolysis of cellulose-containing plant raw materials involve processing with dilute solutions HCl and H2SO4 (0.2-0.3%) at 150-180°; the yield of sugars during stepwise hydrolysis is up to 50%.

By chemical nature Cellulose is a polyhydric alcohol. Due to the presence of hydroxyl groups in the elementary unit of the macromolecule, cellulose reacts with alkali metals and bases. When dried cellulose is treated with a solution of sodium metal in liquid ammonia at minus 25-50°C for 24 hours, trisodium cellulose alcoholate is formed:

n + 3nNa → n + 1.5nH 2.

When concentrated alkali solutions act on cellulose, along with a chemical reaction, physicochemical processes also occur - swelling of cellulose and partial dissolution of its low-molecular fractions, structural transformations. The interaction of alkali metal hydroxide with cellulose can proceed according to two schemes:

n + n NaOH ↔ n + nH 2 O

[C 6 H 7 O 2 (OH) 3 ]n + n NaOH ↔ n.

Reactivity The primary and secondary hydroxyl groups of cellulose in an alkaline environment are different. The most pronounced acidic properties are those of hydroxyl groups located at the second carbon atom of the elementary unit of cellulose, which are part of the glycol group and are inα -position to the acetal bond. The formation of cellulose alkoxide apparently occurs precisely due to these hydroxyl groups, while when interacting with the remaining OH groups, a molecular compound is formed.

The composition of alkali cellulose depends on the conditions of its production - alkali concentration; temperature, nature of the cellulose material and others. Due to the reversibility of the reaction of formation of alkali cellulose, an increase in the concentration of alkali in the solution leads to an increaseγ (the number of substituted hydroxyl groups per 100 elementary units of a cellulose macromolecule) of alkali cellulose, and a decrease in mercerization temperature leads to an increaseγ alkaline cellulose obtained by the action of equiconcentrated alkali solutions, which is explained by the difference in temperature coefficients direct and reverse reactions. The different intensity of interaction of different cellulose materials with alkalis is apparently associated with the characteristics of the physical structure of these materials.

Important integral part The process of interaction of cellulose with alkalis is the swelling of cellulose and the dissolution of its low molecular weight fractions. These processes facilitate the removal of low molecular weight fractions (hemicelluloses) from cellulose and the diffusion of esterifying reagents into the fiber during subsequent esterification processes (for example, xanthogenation). As the temperature decreases, the degree of swelling increases significantly. For example, at 18°, the increase in cotton fiber diameter at 12% NaOH is 10%, and at -10° it reaches 66%. With increasing alkali concentration, there is first an increase and then (over 12%) a decrease in the degree of swelling. The maximum degree of swelling is observed at those alkali concentrations at which an X-ray pattern of alkali cellulose appears. These concentrations are different for different cellulose materials: for cotton 18% (at 25°), for ramie 14-15%, for sulfite cellulose 9.5-10%. Interaction of cellulose with concentrated solutions N AOH is widely used in the textile industry, in the production of artificial fibers and cellulose ethers.

The interaction of cellulose with other alkali metal hydroxides proceeds similarly to the reaction with caustic soda. The X-ray pattern of alkali cellulose appears when natural cellulose preparations are exposed to approximately equimolar (3.5-4.0 mol/l) solutions of alkali metal hydroxides. Strong organic bases, some tetraalkyl (aryl) ammonium hydroxides, apparently form molecular compounds with cellulose.

A special place in the series of reactions of cellulose with bases is occupied by its interaction with cupriammine hydrate [ Cu (NH 3 ) 4 ] (OH ) 2 , as well as with a number of other complex compounds of copper, nickel, cadmium, zinc - cupriethylenediamine [ Cu (en) 2 ](OH) 2 (en - ethylenediamine molecule), nioxane [ Ni(NH 3 ) 6 ] (OH) 2 , nioxene [ Ni (en ) 3 ] (OH) 2 , cadoxene [ Cd (en ) 3 ] (OH ) 2 and others. Cellulose dissolves in these products. Precipitation of cellulose from a copper-ammonia solution is carried out under the action of water, alkali or acid solutions.

Under the action of oxidizing agents, partial oxidation of cellulose occurs - a process successfully used in technology (bleaching cellulose and cotton fabrics, pre-ripening of alkali cellulose). Cellulose oxidation is a side process during the refining of cellulose, the preparation of copper-ammonia spinning solution, and the operation of products made from cellulose materials. The products of partial oxidation of cellulose are called oxycelluloses. Depending on the nature of the oxidizing agent, cellulose oxidation can be selective or non-selective. The most selectively acting oxidizing agents include periodic acid and its salts, which oxidize the glycol group of the elementary unit of cellulose with rupture of the pyran ring (formation of cellulose dialdehyde) (see figure). Under the action of periodic acid and periodates, a small number of primary hydroxyl groups are also oxidized (to carboxyl or aldehyde groups). According to a similar scheme, cellulose is oxidized under the action of lead tetraacetate in an environment of organic solvents (acetic acid, chloroform).

In terms of resistance to acids, dialdehydecellulose differs little from the original cellulose, but is much less resistant to alkalis and even water, which is the result of hydrolysis of the hemiacetal bond in an alkaline environment. Oxidation of aldehyde groups into carboxyl groups by the action of sodium chlorite (formation of dicarboxylcellulose), as well as their reduction to hydroxyl groups (formation of the so-called"disalcohol" - cellulose) stabilize oxidized cellulose to the action of alkaline reagents. The solubility of cellulose dialdehyde nitrates and acetates even of low oxidation states (γ = 6-10) is significantly lower than the solubility of the corresponding cellulose ethers, apparently due to the formation of intermolecular hemiacetal bonds during esterification. When nitrogen dioxide acts on cellulose, predominantly primary hydroxyl groups are oxidized to carboxyl groups (formation of monocarboxylcellulose) (see figure). The reaction proceeds by a radical mechanism with the intermediate formation of cellulose nitrate esters and subsequent oxidative transformations of these esters. Up to 15% of the total content of carboxyl groups are nonuronic (COOH groups are formed at the second and third carbon atoms). At the same time, the oxidation of hydroxyl groups at these atoms to keto groups occurs (up to 15-20% of the total number of oxidized hydroxyl groups). The formation of keto groups is apparently the reason for the extremely low resistance of monocarboxylcellulose to the action of alkalis and even water at elevated temperatures.

With a content of 10-13% COOH groups, monocarboxylcellulose dissolves in a dilute solution NaOH, solutions of ammonia, pyridine with the formation of the corresponding salts. Its acetylation proceeds more slowly than cellulose; acetates are not completely soluble in methylene chloride. Monocarboxylcellulose nitrates are not soluble in acetone even with a nitrogen content of up to 13.5%. These property features esters monocarboxylcelluloses are associated with the formation of intermolecular ether bonds during the interaction of carboxyl and hydroxyl groups. Monocarboxylcellulose is used as a hemostatic agent and as a cation exchanger for the separation of biologically active substances (hormones). By combined oxidation of cellulose with periodate, and then with chlorite and nitrogen dioxide, preparations of the so-called tricarboxylcellulose containing up to 50.8% COOH groups were synthesized.

The direction of cellulose oxidation under the influence of non-selective oxidizing agents (chlorine dioxide, hypochlorous acid salts, hydrogen peroxide, oxygen in an alkaline medium) largely depends on the nature of the medium. In acidic and neutral environments, under the action of hypochlorite and hydrogen peroxide, the formation of products of a reducing type occurs, apparently as a result of the oxidation of primary hydroxyl groups to aldehydes and one of the secondary OH groups to a keto group (hydrogen peroxide also oxidizes glycol groups with rupture of the pyran ring ). During oxidation with hypochlorite in an alkaline environment, aldehyde groups gradually transform into carboxyl groups, as a result of which the oxidation product is acidic in nature. Hypochlorite treatment is one of the most commonly used pulp bleaching methods. To obtain high-quality cellulose with a high degree of whiteness, it is bleached with chlorine dioxide or chlorite in an acidic or alkaline environment. In this case, lignin is oxidized, dyes are destroyed, and aldehyde groups in the cellulose macromolecule are oxidized to carboxyl groups; hydroxyl groups are not oxidized. Oxidation by atmospheric oxygen in an alkaline environment, which occurs by a radical mechanism and is accompanied by significant destruction of cellulose, leads to the accumulation of carbonyl and carboxyl groups in the macromolecule (pre-ripening of alkaline cellulose).

The presence of hydroxyl groups in the elementary unit of the cellulose macromolecule allows the transition to such important classes of cellulose derivatives as ethers and esters. Due to their valuable properties, these compounds are used in various industries technology - in the production of fibers and films (cellulose acetates, nitrates), plastics (acetates, nitrates, ethyl, benzyl ethers), varnishes and electrical insulating coatings, as suspension stabilizers and thickeners in the oil and textile industries (low-substituted carboxymethylcellulose).

Cellulose-based fibers (natural and artificial) are a full-fledged textile material with a complex of valuable properties (high strength and hygroscopicity, good dyeability. The disadvantages of cellulose fibers are flammability, insufficiently high elasticity, easy destruction under the influence of microorganisms, etc. A tendency towards directional Changes (modifications) of cellulose materials have led to the emergence of a number of new cellulose derivatives, and in some cases, new classes of cellulose derivatives.

Modification of properties and synthesis of new cellulose derivatives are carried out using two groups of methods:

1) esterification, O-alkylation or conversion of hydroxyl groups of an elementary unit into other functional groups (oxidation, nucleophilic substitution using some cellulose ethers - nitrates, ethers with n -toluene- and methanesulfonic acid);

2) graft copolymerization or interaction of cellulose with polyfunctional compounds (transformation of cellulose into a branched or cross-linked polymer, respectively).

One of the most common methods for the synthesis of various cellulose derivatives is nucleophilic substitution. The starting materials in this case are cellulose ethers with some strong acids(toluene and methanesulfonic acid, nitric and phenylphosphoric acids), as well as halogenodeoxy derivatives of cellulose. Using a nucleophilic substitution reaction, cellulose derivatives have been synthesized in which hydroxyl groups are replaced by halogens (chlorine, fluorine, iodine), rhodane, nitrile and other groups; deoxycellulose preparations containing heterocycles (pyridine and piperidine) were synthesized, cellulose ethers with phenols and naphthols, a number of cellulose esters (with higher carboxylic acids,α - amino acids , unsaturated acids). The intramolecular reaction of nucleophilic substitution (saponification of cellulose tosyl ethers) leads to the formation of mixed polysaccharides containing 2, 3- and 3, 6-anhydrocycles.

Greatest practical significance to create cellulose materials with new technical valuable properties, has the synthesis of cellulose graft copolymers. The most common methods for the synthesis of cellulose graft copolymers include the use of a chain transfer reaction on cellulose, radiation-chemical copolymerization and the use of redox systems in which cellulose plays the role of a reducing agent. In the latter case, the formation of a macroradical can occur due to the oxidation of both hydroxyl groups of cellulose (oxidation with cerium salts) and those specially introduced into the macromolecule functional groups- aldehyde, amino groups (oxidation with vanadium, manganese salts), or decomposition of a diazo compound formed during diazotization of aromatic amino groups introduced into cellulose. The synthesis of cellulose graft copolymers in some cases can be carried out without the formation of a homopolymer, which reduces monomer consumption. Cellulose graft copolymers, obtained under conventional copolymerization conditions, consist of a mixture of the original cellulose (or its ether, which is grafted onto) and the graft copolymer (40-60%). The degree of polymerization of grafted chains varies depending on the initiation method and the nature of the grafted component from 300 to 28,000.

The change in properties as a result of graft copolymerization is determined by the nature of the grafted monomer. The grafting of styrene, acrylamide, and acrylonitrile increases the dry strength of cotton fiber. Grafting polystyrene, polymethyl methacrylate, and polybutyl acrylate produces hydrophobic materials. Graft copolymers of cellulose with flexible chain polymers (polymethyl acrylate) are thermoplastic if the content of the grafted component is sufficiently high. Graft copolymers of cellulose with polyelectrolytes ( polyacrylic acid, polymethylvinylpyridine) can be used as ion-exchange fabrics, fibers, films.

One of the disadvantages of cellulose fibers is low elasticity and, as a result, poor shape retention of products and increased creasing. Elimination of this disadvantage is achieved through education intermolecular bonds when treating fabrics with polyfunctional compounds (dimethylolurea, dimethylolcycloethyleneurea, trimethylolmelamine, dimethyloltriazone, various diepoxides, acetals) that react with the OH groups of cellulose. Along with education chemical bonds Between cellulose macromolecules, polymerization of the cross-linking reagent occurs with the formation of linear and spatial polymers. Fabrics made from cellulose fibers are impregnated with a solution containing a cross-linking reagent and a catalyst, wrung out, dried at a low temperature and heat treated at 120-160° for 3-5 minutes. When treating cellulose with multifunctional cross-linking reagents, the process occurs mainly in the amorphous regions of the fiber. To achieve the same crease-resistant effect, the consumption of cross-linking reagent when processing viscose fibers should be significantly higher than when processing cotton fiber, which is apparently due to more high degree crystallinity of the latter.

Pure cellulose or fiber(from Latin cellula - “cell”) - these are substances also directly related to sugars. Their molecules are connected to each other by hydrogen bonds ( weak interaction) and are formed from many (2000 to 3000) B-glucose residues. Cellulose is the main component of any plant cell. It is found in wood and in the shells of some fruits (for example, sunflower seeds). IN pure form cellulose- It is a white powder, insoluble in water and does not form a paste. To evaluate "by touch" pure cellulose you can take, for example, cotton wool or white poplar fluff.
It's practically the same. If we compare cellulose and starch, starch is better hydrolyzed. Hydrolysis of cellulose is carried out in an acidic environment, and first the disaccharide cellobiose is formed, and then glucose.
Cellulose is widely used in industry, after purification it is produced, which is familiar to all of us. cellophane(polyethylene and cellophane differ from each other to the touch (cellophane does not seem “greasy” and “rustles” when deformed), as well as artificial fiber - viscose (from Latin viscosus - “viscous”).
Once in the body, disaccharides (for example, sucrose, lactose) and polysaccharides (starch) are hydrolyzed under the action of special enzymes to form glucose and fructose. This transformation can easily be done in your mouth. If you chew the bread crumb for a long time, then under the action of the enzyme amylase, the starch contained in the bread is hydrolyzed to glucose. This creates a sweet taste in the mouth.

Below is a diagram cellulose hydrolysis

Receiving paper

Pure cellulose

What do you think is included in paper composition?! In fact, this is a material that consists of very finely intertwined fibers cellulose. Some of these fibers are combined hydrogen bond(the bond formed between the groups is OH – hydroxyl group). Method of obtaining paper in the 2nd century BC it was already known in ancient China. At that time, paper was made from bamboo or cotton. Later, in the 9th century AD, this secret came to Europe. For receiving paper Already in the Middle Ages, linen or cotton fabrics were used.

But only in the 18th century they found the most convenient way receiving paper- made of wood. And the kind of paper that we now use began to be produced only in the 19th century.

The main raw material for receiving paper is cellulose. Dry wood contains approximately 40% of this cellulose. The rest of the tree is various polymers made up of sugars various types, including fructose, complex substances– phenol alcohols, various tannins, magnesium, sodium and potassium salts, essential oils.

Preparation of cellulose

Preparation of cellulose associated with the mechanical processing of wood and then carrying out chemical reactions with sawdust. Coniferous trees are ground into fine sawdust. These sawdust are placed in a boiling solution containing NaHSO 4 (sodium hydrogen sulfide) and SO 2 (sulfur dioxide). Boiling is carried out at high blood pressure(0.5 MPa) and for a long time (about 12 hours). In this case, a chemical reaction occurs in the solution, resulting in the formation of a substance hemicellulose and substance lignin (lignin is a substance that is a mixture aromatic hydrocarbons or aromatic part of the tree), as well as the main reaction product - pure cellulose, which falls out as a precipitate in the container where the chemical reaction is carried out. In addition, lignin, in turn, reacts with sulfur dioxide in solution, resulting in the production of ethyl alcohol, vanillin, various tannins, and nutritional yeast.

Further process pulp production associated with the grinding of sediment using rolls, resulting in cellulose particles of about 1 mm. And when such particles get into water, they immediately swell and form paper. At this stage, the paper does not yet look like itself and looks like a suspension of cellulose fibers in water.

On next stage paper is given its basic properties: density, color, strength, porosity, smoothness, for which clay, titanium oxide, barium oxide, chalk, talc and additional substances, connecting cellulose fibers. Further cellulose fibers treated with a special glue based on resin and rosin. It consists of resinates. If you add potassium alum to this glue, a chemical reaction occurs and a precipitate of aluminum resinates is formed. This substance is able to envelop cellulose fibers, which gives them moisture resistance and strength. The resulting mass is evenly applied to a moving mesh, where it is wrung out and dried. There is already formation here paper web. To make the paper more smooth and shiny, it is passed first between metal and then between thick paper rolls (calendering is carried out), after which the paper is cut into sheets with special scissors.

How do you think, Why does paper turn yellow over time?!?

It turns out that cellulose molecules that were isolated from wood consist of a large number structural units type C 6 H 10 O 5, which, under the influence of hydrogen atom ions, lose bonds with each other over a certain time, which leads to disruption of the overall chain. With this process, the paper becomes brittle and loses its original color. It still happens, as they say, paper acidification . In order to restore deteriorating paper, calcium bicarbonate Ca(HCO 3) 2) is used, which allows you to temporarily reduce acidity.

There is another, more progressive method associated with the use of diethylzinc substance Zn(C 2 H 5) 2. But this substance can spontaneously ignite in air and even in proximity to water!

Applications of cellulose

In addition to the fact that cellulose is used to make paper, it is also used for its very useful properties. esterification with various inorganic and organic acids. In the process of such reactions, esters are formed, which have found application in industry. During the chemical reaction itself, the bonds that bind the fragments of the cellulose molecule are not broken, but a new chemical compound with the ester group -COOR- is obtained. One of the important reaction products is cellulose acetate, which is formed during the interaction acetic acid(or its derivatives, for example acetaldehyde) and cellulose. This chemical compound is widely used to make synthetic fibers such as acetate fiber.

Another useful product - cellulose trinitrate. It is formed when nitration of cellulose a mixture of acids: concentrated sulfuric and nitric. Cellulose trinitrate is widely used in the manufacture of smokeless gunpowder (pyroxylin). There is also cellulose dinitrate, which is used to make certain types of plastics and

Cellulose (French cellulose, from Latin cellula, literally - little room, cell, here - cell)

fiber, one of the most common natural polymers(polysaccharide (See Polysaccharides)); the main component of plant cell walls, which determines the mechanical strength and elasticity of plant tissues. Thus, the content of color in the hairs of cotton seeds is 97-98%, in the stems of bast plants (flax, ramie, jute) 75-90%, in wood 40-50%, reeds, cereals, sunflowers 30-40%. It is also found in the body of some lower invertebrates.

In the body, C. serves mainly building material and is almost not involved in metabolism. C. is not broken down by the usual enzymes of the gastrointestinal tract of mammals (amylase, maltase); Under the action of the enzyme cellulase, secreted by the intestinal microflora of herbivores, cellulose breaks down into D-glucose. C. biosynthesis occurs with the participation of the activated form of D-glucose.

Structure and properties of cellulose. C. - white fibrous material, density 1.52-1.54 g/cm 3 (20 °C). C. is soluble in the so-called. copper-ammonium solution [a solution of ammine cuprum (II) hydroxide in a 25% aqueous ammonia solution], aqueous solutions of quaternary ammonium bases, aqueous solutions of complex compounds of polyvalent metal hydroxides (Ni, Co) with ammonia or ethylenediamine, an alkaline solution of an iron complex ( III) with sodium tartrate, solutions of nitrogen dioxide in dimethylformamide, concentrated phosphoric and sulfuric acids (dissolution in acids is accompanied by destruction of C.).

Macromolecules of glucose are built from elementary units of D-glucose (See Glucose), connected by 1,4-β-glycosidic bonds into linear unbranched chains:

C. are usually classified as crystalline polymers. It is characterized by the phenomenon of polymorphism, i.e. the presence of a number of structural (crystalline) modifications that differ in parameters crystal lattice and some physical and chemical properties; the main modifications are C. I (natural C.) and C. II (hydrated cellulose).

C. has a complex supramolecular structure. Its primary element is a microfibril, consisting of several hundred macromolecules and having the shape of a spiral (thickness 35-100 Å, length 500-600 Å and above). Microfibrils are combined into larger formations (300-1500 Å), differently oriented in different layers of the cell wall. The fibrils are “cemented” by the so-called. a matrix consisting of other polymer materials carbohydrate nature (hemicellulose, pectin) and protein (extensin).

Glycosidic bonds between the elementary units of the macromolecule of C. are easily hydrolyzed under the action of acids, which is the cause of the destruction of C. in aquatic environment in the presence of acid catalysts. The product of complete hydrolysis of C. is glucose; this reaction underlies the industrial production method ethyl alcohol from cellulose-containing raw materials (see Hydrolysis of plant materials). Partial hydrolysis of citrus occurs, for example, when it is isolated from plant materials and during chemical processing. By incomplete hydrolysis of C., carried out in such a way that destruction occurs only in poorly ordered areas of the structure, the so-called. microcrystalline “powder” C. - snow-white, free-flowing powder.

In the absence of oxygen, C. is stable up to 120-150 °C; With a further increase in temperature, natural cellulose fibers undergo destruction, and cellulose hydrates undergo dehydration. Above 300 °C, graphitization (carbonization) of the fiber occurs - a process used in the production of carbon fibers (See Carbon fibers).

Due to the presence of hydroxyl groups in the elementary units of the macromolecule, C. is easily esterified and alkylated; these reactions are widely used in industry to produce cellulose ethers and esters (see Cellulose esters). C. reacts with bases; interaction with concentrated solutions of caustic soda, leading to the formation of alkaline C. (Mercerization of C.), is an intermediate stage in the production of C. esters. Most oxidizing agents cause indiscriminate oxidation of the hydroxyl groups of C. to aldehyde, keto- or carboxyl groups, and only some of the oxidizing agents (for example, periodic acid and its salts) - selective (i.e. they oxidize OH groups at certain carbon atoms). C. is subjected to oxidative destruction when producing viscose (See Viscose) (pre-ripening stage of alkaline C.); oxidation also occurs during bleaching.

Application of cellulose. Paper is produced from carbon (See paper) , cardboard, various artificial fibers - hydrated cellulose (Viscose fibers, copper-ammonia fiber (See Copper-ammonia fibers)) and cellulose ether (acetate and triacetate - see Acetate fibers) , films (cellophane), plastics and varnishes (see Etrols, Hydrated cellulose films, Cellulose ether varnishes). Natural fibers from cotton (cotton, bast), as well as artificial ones, are widely used in the textile industry. C. derivatives (mainly ethers) are used as thickeners for printing inks, sizing and sizing preparations, suspension stabilizers in the manufacture of smokeless powder, etc. Microcrystalline C. is used as a filler in the manufacture of medicines, as a sorbent in analytical and preparative chromatography.

Lit.: Nikitin N.I., Chemistry of wood and cellulose, M. - L., 1962; Brief chemical encyclopedia, t. 5, M., 1967, p. 788-95; Rogovin Z. A., Cellulose Chemistry, M., 1972; Cellulose and its derivatives, trans. from English, vol. 1-2, M., 1974; Kretovich V.L., Fundamentals of plant biochemistry, 5th ed., M., 1971.

L. S. Galbreikh, N. D. Gabrielyan.

Big Soviet encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

Synonyms:

See what "Cellulose" is in other dictionaries:

Cellulose ... Wikipedia

1) otherwise fiber; 2) a type of parchment paper made from a mixture of wood, clay and cotton. Complete dictionary foreign words, which have come into use in the Russian language. Popov M., 1907. CELLULOSE 1) fiber; 2) paper made from wood with an admixture of... Dictionary of foreign words of the Russian language

Gossypin, cellulose, fiber Dictionary of Russian synonyms. cellulose noun, number of synonyms: 12 alkalicellulose (1) ... Synonym dictionary

- (C6H10O5), a carbohydrate from the POLYSACCHARIDES group, which is a structural component of the cell walls of plants and algae. It consists of parallel, unbranched glucose chains connected crosswise to form a stable structure.… … Scientific and technical encyclopedic dictionary

Fiber, the main supporting polysaccharide of the cell walls of plants and some invertebrates (ascidians); one of the most common natural polymers. Of the 30 billion tons of carbon, which higher plants annually converted into organic. connections, ok... Biological encyclopedic dictionary

cellulose- y, w. cellulose f., German Zellulose lat. cellula cell.1. Same as fiber. BAS 1. 2. A substance obtained from chemically treated wood and stems of certain plants; used for the production of paper, artificial silk, and also... ... Historical Dictionary of Gallicisms of the Russian Language

- (French cellulose from Latin cellula, lit. room, here cell) (fiber), a polysaccharide formed by glucose residues; the main component of plant cell walls, which determines the mechanical strength and elasticity of plant... ... Big encyclopedic Dictionary

- (or cellulose), cellulose, pl. no, female (from Latin cellula cell). 1. Same as fiber in 1 value. (bot.). 2. A substance obtained from chemically treated wood and stems of some plants and used for the production of paper, artificial ... Dictionary Ushakova

CELLULOSE, s, female. Same as fiber (1 value). | adj. cellulose, oh, oh. Ozhegov's explanatory dictionary. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 … Ozhegov's Explanatory Dictionary

Cellulose. See fiber. (