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34746.		Gregorian reform and Gregorian calendar	14.62KB
	This difference, accumulating annually, led after 128 years to an error of one day, and after 1280 years already in 10 days. The reform was supposed to solve two main tasks: firstly, to eliminate the accumulated difference of 10 days between the calendar and tropical years, and secondly, to bring the calendar year as close as possible to the tropical one so that in the future the difference between them would not be noticeable. Gregorian calendar In the Gregorian calendar, the length of the year is 3652425 days.
34747.		Time units: month, week, day	12.86KB
	The transition to agriculture and cattle breeding determined the need to take into account the time of its fixation in certain units. All the main units of time calculation developed by mankind day, month and year are determined by astronomical factors: a day, the period of the Earth's revolution around its axis, a month, the period of the Moon's revolution around the Earth, a year, the period of the Earth's revolution around the Sun. To facilitate the calculation of time, a fictitious concept of the mean sun, i.e., is introduced.
34748.		Types of chronology (eras) and reference points	15.88KB
	The first example is the era of Kali in India. Political eras include those whose starting points are the dates of the founding of cities, the accession to the throne of various rulers, etc. Such is, for example, the era of the post-consulate, the starting point of which was the election of the last Roman consul Flavius ​​Basil the Lesser in 541. In real eras, a historical event in fictitious legendary.
34749.		Era from the Nativity of Christ Dionysius the Lesser	11.06KB
	era of Diocletian by the monk Dionysius the Small. from the beginning of the reign of Emperor Diocletian around 243,313. The Romans called it the era of Diocletian. Dionysius the Lesser considered it more appropriate to replace the era of the pagan and opponent of Christianity Diocletian with another era somehow connected with Christianity.
34750.		Ordinary ideas of a person of Ancient Russia about time and chronology	17.96KB
	Such are, for example, carnival carols from the Latin calenda; another name for this holiday is autumn from autumn, which marked the turn of the sun for summer, the red hill, the celebration of the meeting of spring, the rainbow and the mermaids, spring and summer memorial holidays, and others. Survival names of the days of the week associated with astral cults have survived in some European countries to this day, for example: German Montg day Moon Monday Sonntg Sun Day Sunday French Vendredi Venus Day Friday...
34751.		Reform of the chronology of Peter 1	11.17KB
	Peter, on the other hand, wanted the New Year to be counted from the Nativity of Christ on January 1, like other European states. To this end, on December 20, a decree was issued to count the New Year, following the example of all other Christian powers, from January 1, 8 days after Christmas, on December 25, according to the old style. In addition, wherever the place is convenient, from January 1 to January 7, fires and tar barrels should be lit.
34752.		The concept of the March, September and ultra-March years of the Byzantine era. Ways to transfer them to the modern system of chronology	55.18KB
	Translation of the date according to the Ultra-March style to the modern system of chronology: If the event falls on the period of time between March and December inclusive, to transfer to the modern time system, it is necessary to subtract 5509 years from the date by era from the creation of the world. Task 1: Convert the date given in the ultra-March style to the modern chronology system: July 18, 6793. Solution: Since the date is given in the ultra-March style, subtract 5509 for the month of July. Task 2: Convert the date to the modern chronology system ...
34753.		Dating events according to indications for church holidays. Dating by astronomical phenomena	15.25KB
	As for the movable holidays, they all depend on Easter, separating from it by certain constant periods before or after Easter. For example, the Ascension of the Lord Thursday 39 days after Easter Palm Sunday 7 days before Easter Fomino Sunday 7 days after Easter the Lord enters Jerusalem 7 days before Easter. The mobility of Easter itself is explained by the fact that it is calculated according to the lunar calendar. To determine the day of Easter, they use special tables of reversal of the great indiction.
34754.		Determining the days of the week using formulas and tables	15.12KB
	There are several mathematical formulas for determining the day of the week. Perevoshchikov: X is the remainder of the expression: 7 where X is the ordinal number of the day of the week, counting from Sunday, Sunday 1, Monday 2, etc. Cherukhina: X is the remainder of dividing the expression: 7 where X is the ordinal number of the day of the week, counting from Monday, Monday 1, Tuesday 2, etc.

Paper and white products are paper and cardboard products intended for writing, drawing, drawing, storing photographs, stamps, etc. This group of goods is very extensive - notebooks, albums, notepads, notebooks, etc. In addition, in quantitative terms, it is quite significant.

The world produces over 300 million tons of paper and cardboard per year, which is about 50 kg per inhabitant of the Earth. The most common division of paper by purpose looks like this:

• for writing and printing (graphic types);
• Newspaper (traditionally singled out as a separate sector due to significant production volume and importance for society);
• paper and cardboard for packaging;
• · sanitary and hygienic;
• technical.

The largest consumer of paper is the printing industry. Of the total volume of paper and cardboard produced in the world, about 30% are graphic types, i.e. paper for printing, writing, drawing, for copiers and digital printing equipment.

According to GOST 9327-60 “Paper and paper products. Consumer Formats. Paper is divided into 11 classes:

• 1. For printing (typographical, offset, illustrative for intaglio printing, cartographic, coated, etc.) - it is distinguished by high smoothness, whiteness; well absorbs printing ink. This class also includes newsprint made from cheaper fibrous materials without sizing and fillers or with a low content of fillers and wallpaper paper.
• 2. For writing (writing, postal, envelope, for cards, etc.) - it is distinguished by good sizing, low absorbency and high smoothness. Paper of the first two classes is produced from unbleached and bleached sulphate and sulfite pulp, as well as using rag semi-mass and wood pulp.
• 3. Drawing and drawing (drawing, drawing, drawing transparent, drawing tracing paper, etc.) - it is usually produced without filler or with a small content of it, it is well glued, and to make it transparent, some grades are strongly moistened and calendered at high roller pressure. It is made from sulphate bleached pulp with the addition of certain types of wood pulp, rag and cotton semi-mass.
• 4. Electrical insulation (capacitor, cable, telephone insulating-winding, etc.) - has a high mechanical strength and good dielectric properties. It is usually produced from sulphate unbleached pulp with low ash content and high purity, without fillers and sizing agents.
• 5. Cigarette (mouthpiece, cigarette, cigarette, smoking) - in terms of composition, properties and manufacturing technology, this class of paper is very diverse. Raw materials - bleached or unbleached sulfite pulp with the addition of bleached wood pulp or flax production waste (tows).
• 6. Absorbent (filtering, blotting, impregnating) - used for the production of fiber, parchment, sanitary ware, etc.; has a high porosity, absorbs liquids well.
• 7. Paper for devices (telegraphic tape, Creed tape, punched card, etc.) - is characterized by increased mechanical strength. It is made from unbleached sulphite or sulphate (punched card) pulp with the addition of white wood pulp in some cases.
• 8. Photosensitive (bases) - a photo substrate used for making photographic paper, photosensitive for blueprints, etc.; It is characterized by high mechanical strength, good sizing and a number of special properties. Produced from bleached and unbleached sulfite and sulfate pulp.
• 9. Transferable (bases - copying, transferring, etc.) - undergoes special processing.
• 10. Wrapping - used for packaging food products and industrial goods - bag, tea, match, bottle, fruit, vegetable parchment, opaque, waxing base, reinforced, etc. It is made from durable fibrous materials, as well as production waste. Some types of paper of this class are subjected to bituminization, waxing, lamination (obtaining paper of a layered structure), etc.
• 11. Industrial and technical for various purposes. The most extensive class of paper: cartridge, emery, diffuser, for sound recording, for yarn, etc. This class includes the so-called long-staple papers (silk, asbestos, glass, etc.), made from cotton fiber, asbestos and artificial fibers in the usual way of paper production, as well as "dry molding". Differs in high elasticity and mechanical durability.

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1. History of the origin of paper

Paper is a material made from plant fibers, processed and joined into a thin sheet, in which the fibers are interconnected by surface cohesive forces. The word paper comes from the Tatar word "bumug", which means cotton. Also presumably this word comes from the Italian bambagia - cotton.

The historical prerequisites for the emergence of paper production originate in ancient times, when society needed to fix their relationships.

Writing materials have undergone significant changes over the centuries. The initial and most frequent appeal of ancient people to the stone was due to its availability. However, certain difficulties in use (impossibility of quick recording, difficulty in processing) led to the forced rejection of it as a material for writing.

The next step in the transformation of written material was the use of clay - an easily accessible, ubiquitous natural material. The softness and pliability of clay made it possible to use a thin pointed stick as a tool. Dried and fire-fired, the tile became hard as a stone and was stored for a long time.

In search of more practical media, ancient people tried to write on wood, its bark, leaves, leather, metals, and bones. In countries with a hot climate, dried and varnished palm leaves were often used. In Russia, the most common material for writing was birch bark.

In a number of European countries, before the advent of paper, papyrus was used. Papyrus making originated in ancient Egypt around 3,500 BC. It was prepared from a reed plant growing in the lower reaches of the Nile. This plant has a straight trihedral stem up to 5 meters high. For the preparation of material for writing, only the lower part of the stem, about 60 centimeters long, was used. It was freed from the outer green layer, and the white core was cut with a knife into thin narrow strips and kept in fresh water for 2-3 days to swell and remove soluble substances. The softened strips were rolled with a wooden gurney on the board, then again soaked for a day, rolled and again immersed in water. After these operations, the strips became translucent and had a creamy tint. After that, the stem strips were stacked on top of each other, dehydrated under a press, after which they were dried under a press and smoothed with a smooth stone.

Around the 5th century AD, the production of papyrus declined sharply, as parchment appeared and, somewhat later, paper, and from the 10th century AD. papyrus lost its industrial value.

In the 2nd century BC in Asia Minor in the Kingdom of Pergamum in the city of Pergamum, the production of excellent writing material was organized, but not from papyrus, but from the skins of young animals treated in a special way - calves, lambs, goats, donkeys. By the name of the city, this material became known as parchment. Unlike papyrus, parchment was much stronger, more elastic, more durable, it was easier to write on it, and on both sides, and if necessary, the text could be easily washed off and a new one applied. But, despite these advantages of parchment, its manufacture is laborious and it was an expensive material.

Chinese chronicles report that paper was invented in 105 AD. Tsai Lun. Before Cai Lun, paper in China was made from hemp, and even earlier from silk, which was made from defective silkworm cocoons. Cai Lun crushed mulberry fibers, wood ash, rags and hemp. Cai Lun mixed all this with water and laid out the resulting mass on a mold (wooden frame and bamboo sieve). After drying in the sun, Cai Lun smoothed this mass with the help of stones. The result is strong sheets of paper. After Cai Lun's invention, the papermaking process improved rapidly. Over time, starch, glue, natural dyes, etc. were added to paper to increase strength.

At the beginning of the 7th century paper making method becomes known in Korea and Japan. And after another 150 years, through prisoners of war, the secret of making paper gets to the Arabs.

In the VI-VIII centuries. paper production was carried out in Central Asia, Korea, Japan and other Asian countries.

Of great importance for the development of paper production was an invention in the second half of the 17th century. grinding apparatus - roll. At the end of the XVIII century. rolls already made it possible to produce a large amount of paper pulp, but manual ebb (scooping) of paper delayed the growth of production. In 1799 N.L. Robert (France) invented the paper machine by mechanizing the ebb of paper by using an infinitely moving grid. In England, the brothers G. and S. Fourdrinier, having bought Robert's patent, continued to work on the mechanization of the ebb and in 1806 patented a paper machine. By the middle of the XIX century. the paper machine has become a complex machine that operates continuously and largely automatically. In the XX century. paper production is becoming a large highly mechanized industry with a continuous flow process flow diagram, powerful thermal power plants and complex chemical workshops for the production of fibrous semi-finished products.

2. Paper range

paper market assortment commodity

Paper is a material consisting of cellulose fibers (wood pulp, wood pulp, cotton, flax, recycled fibers) interconnected by surface adhesion forces, which may contain sizing agents, mineral fillers, chemical and natural fibers, pigments and dyes. The length of plant fibers from which paper is formed is 1-2 mm with a diameter of about 25 microns. The mass of one square meter of paper reaches 250 grams.

Paper of various types is used for the production of packs, bags, packages, for packaging products manually and on automatic machines, as well as in design. Corrugated flat cardboard is used for the production of rigid consumer packaging (boxes, packs, combined packaging), as well as for the production of transport (boxes) containers.

There are different types of paper:

1) wrapping paper is paper for manual packaging of food and non-food products, used for the production of packages and for the formation of group packaging;

Wrapping paper is made from unbleached pulp and other semi-finished products. Depending on the type, purpose and quality characteristics of wrapping paper, there are 9 grades:

A, B, C, D, 01, 02, E, F, F.

Paper of such brands as B, G, E, G is used for food packaging, if it does not contain waste paper and other low-grade raw materials. It is used mainly for packaging non-food products, it is "non-food" paper. It has a natural fiber color, with shades of gray or beige.

2) paper for food packaging on automatic machines;

The paper that is used for packaging food products on automatic machines is necessary for the production of boxes, packs, bags for groceries, confectionery, bakery, for granulated sugar, refined sugar, cups for packaged ice cream, etc., as well as for use in public catering (disposable). It is produced by such brands: 0; A-I, A-II, B-I, D, E-I, E-II, B, D, PV-260.

3) vegetable parchment;

Parchment is a vegetable fat-resistant and moisture-resistant material. Parchment is obtained by processing special types of paper with concentrated sulfuric acid for 2-3 seconds. This is sufficient for intense swelling of cellulose to occur in the surface layers of the paper. Then it is squeezed out, and the swollen cellulose fills the interfiber spaces. Then it is washed and dried, and a rather dense, non-porous structure is formed. It determines the properties of the future parchment.

Parchment can be edible, it also includes parchment for lining jars intended for canning crabs, as well as medical parchment and semi-finished product used as a basis for lamination or metallization (sprayed or with aluminum foil).

4) Subparchment;

This type of paper is a low-porous, conditionally grease-proof material. Subparchment is intended mainly for the inner package in a pack or box, as well as for lining the bottom of boxes when packaging confectionery, when packaging meat products and other types of products. The low porosity of the structure of the subparchment is achieved as a result of careful grinding of the paper pulp during the formation of the material. Several brands are produced depending on its purpose: ZhV, PZH, P.

Products that contain fats and moisture are packed in special types of grease-resistant papers: parchment, parchment and paraffin paper.

5) Waxed paper.

Waxed paper is made from a special base paper, impregnated with molten paraffin. During the waxing process, the moisture resistance of the paper is greatly improved. Paraffin paper is intended for packing caramel and sweets on automatic machines, as well as for curd products, for processed cheese and other similar products.

6) Label paper, microwax coated paper.

7) Embroidered paper or laminated paper.

8) Writing paper.

9) Paper for printing.

10) Glassine

Semi-transparent glued paper made from unfilled bleached pulp. It is used for the production of tracing paper and food packaging.

3. Classification and characteristics of white goods

Paper and white products are paper and cardboard products intended for writing, drawing, drawing, storing photographs, stamps, etc. This group of goods is very extensive - notebooks, albums, notepads, notebooks, etc. In addition, in quantitative terms, it is quite significant.

The world produces over 300 million tons of paper and cardboard per year, which is about 50 kg per inhabitant of the Earth. The most common division of paper by purpose looks like this:

for writing and printing (graphic types);

Newspaper (traditionally singled out as a separate sector due to significant production volume and importance for society);

paper and cardboard for packaging;

· sanitary and hygienic;

technical.

The largest consumer of paper is the printing industry. Of the total volume of paper and cardboard produced in the world, about 30% are graphic types, i.e. paper for printing, writing, drawing, for copiers and digital printing equipment.

According to GOST 9327-60 “Paper and paper products. Consumer Formats. Paper is divided into 11 classes:

1. For printing (typographical, offset, illustrative for intaglio printing, cartographic, coated, etc.) - it is distinguished by high smoothness, whiteness; well absorbs printing ink. This class also includes newsprint made from cheaper fibrous materials without sizing and fillers or with a low content of fillers and wallpaper paper.

2. For writing (writing, postal, envelope, for cards, etc.) - it is distinguished by good sizing, low absorbency and high smoothness. Paper of the first two classes is produced from unbleached and bleached sulphate and sulfite pulp, as well as using rag semi-mass and wood pulp.

3. Drawing and drawing (drawing, drawing, drawing transparent, drawing tracing paper, etc.) - it is usually produced without filler or with a small content of it, it is well glued, and to make it transparent, some grades are strongly moistened and calendered at high roller pressure. It is made from sulphate bleached pulp with the addition of certain types of wood pulp, rag and cotton semi-mass.

4. Electrical insulation (capacitor, cable, telephone insulating-winding, etc.) - has a high mechanical strength and good dielectric properties. It is usually produced from sulphate unbleached pulp with low ash content and high purity, without fillers and sizing agents.

5. Cigarette (mouthpiece, cigarette, cigarette, smoking) - in terms of composition, properties and manufacturing technology, this class of paper is very diverse. Raw materials - bleached or unbleached sulfite pulp with the addition of bleached wood pulp or flax production waste (tows).

6. Absorbent (filtering, blotting, impregnating) - used for the production of fiber, parchment, sanitary ware, etc.; has a high porosity, absorbs liquids well.

7. Paper for devices (telegraphic tape, Creed tape, punched card, etc.) - is characterized by increased mechanical strength. It is made from unbleached sulphite or sulphate (punched card) pulp with the addition of white wood pulp in some cases.

8. Photosensitive (bases) - a photo substrate used for making photographic paper, photosensitive for blueprints, etc.; It is characterized by high mechanical strength, good sizing and a number of special properties. Produced from bleached and unbleached sulfite and sulfate pulp.

9. Transferable (bases - copying, transferring, etc.) - undergoes special processing.

10. Wrapping - used for packaging food products and industrial goods - bag, tea, match, bottle, fruit, vegetable parchment, opaque, waxing base, reinforced, etc. It is made from durable fibrous materials, as well as production waste. Some types of paper of this class are subjected to bituminization, waxing, lamination (obtaining paper of a layered structure), etc.

11. Industrial and technical for various purposes. The most extensive class of paper: cartridge, emery, diffuser, for sound recording, for yarn, etc. This class includes the so-called long-staple papers (silk, asbestos, glass, etc.), made from cotton fiber, asbestos and artificial fibers in the usual way of paper production, as well as "dry molding". Differs in high elasticity and mechanical durability.

Certain requirements and norms are imposed on the quality of paper, and deviations from them more than an acceptable limit are called defects.

4. Paper defects

External defects include rough traces of material - cloth or mesh - paper machines, folds, wrinkles, bubbles, holes, matte stripes, specks, non-uniform thickness, sheet slant. As a rule, the above defects are the result of a violation of production technology.

- Fluctuations in the mass of 1 m² of paper.

The more uniform the mass of 1 m² of paper is maintained, the more uniform, as a rule, the paper turns out to be in terms of other quality indicators: moisture content, thickness, density, clearance, mechanical strength indicators, etc. Maintaining a constant mass of 1 m² of manufactured paper is an important task for technologists. wallets. Permissible weight fluctuations of 1 m² are regulated by the norms of the current standards, and paper with a weight fluctuation of 1 m that goes beyond the norms of the standard is not conditioned. An excessively low weight of 1 m² of paper is often associated with its weakening, increased light transmission (which is undesirable for writing paper or paper for printing) and deterioration of other consumer properties of paper. An excessively high weight of 1 m² also often worsens its consumer properties and, above all, leads to an overrun of the fibers used for making paper. Therefore, it is desirable to produce paper with a weight rate of 1 m² corresponding to the lower limit allowed by the standard.

- Curl and waviness.

The increased curling of paper greatly complicates its use by consumers and can serve, for example, as one of the reasons for the rejection of white goods: notebooks, notebooks, albums, notebooks, etc. Punched cards used in mechanized machine counting must be flat, since their noticeable curl causes the machines they pass through to malfunction.

Paper curl in most cases is one of the manifestations of its versatility. The greater the difference in the orientation of the fibers on the sides of the paper sheet for the same mass of 1 m² of paper and all other things being equal, and the greater the difference in the moisture content of both sides of the paper, the more curl manifests itself. The fact is that when fully swollen plant fibers increase in length by only 1–2%, and under the same conditions in width by 20–30%. Thus, as a result of the uneven orientation of the fibers on both sides of the sheet, even with the same degree of moisture, stresses of different magnitudes arise. Under the influence of a greater voltage, or rather, under the influence of the difference in these voltages, the paper curls.

Single-sided smooth paper tends to curl more. In such paper, the matte side of the sheet is more porous and moisture-permeable. It is this side of this kind of paper (paper for matchboxes, poster paper, etc.) that is moistened with glue.

The waviness and curl of paper phenomena are largely similar, the main reasons for their occurrence:

- Heterogeneity of paper moisture, weight 1 m², clearance, distribution of filling and sizing agents.

1. The difference in the properties of the top and mesh sides.

2. Uneven and excessively high paper web tension on the paper machine.

3. Strong rosin sizing.

4. Increased shrinkage and deformation.

5. Oily grinding of the mass with the presence of fibrillated fibers.

6. Different humidity of drying felts in the corresponding groups of the upper and lower rows of drying cylinders.

7. Mechanical curl during long-term storage of paper rolls.

8. Storing excessively damp paper in dry air or dry paper in humid air.

9. Hanging of the edge of the paper when it is stored on racks or in bales.

Dusting and plucking from the surface.

The most negative property of paper, especially for printed types, is its dustiness.

Dustiness is characterized, on the one hand, by the separation from its surface or from the edges under the influence of mechanical influences (friction, bending, impact) of small pieces of fibers, as well as filler particles, sizing agents or dyes. On the other hand, the printing ink may come off from the surface of the printed paper. As a rule, there is relatively little binder on the surface layer of the paper, which makes it easier to separate the ink pigment from the surface of the paper. Print quality deteriorates drastically when using dusty paper. The print becomes not clear enough or, as printers say, “pockmarked”. Paper dust sticks to the printing plate, clogs it, and it becomes necessary to stop the printing machine frequently to clean the printing plates and rollers. Mineral dust (filler particles), due to its abrasive action, has a destructive effect on the printing plate, especially with intaglio printing. Sometimes it is difficult to distinguish between the dusting of paper and the plucking of individual fibers from its surface during printing. The forces that cause plucking are short-lived and are usually directed vertically to the surface of the paper. In this case, on the surface of the paper, a detachment of a section of the surface layer can occur with splitting of the paper in a plane parallel to the surface.

Electrification of paper

In the pulp and paper industry, paper electrification is characterized by an electrostatic charge on paper that causes sheets to stick together.

In printing houses, the use of paper charged with static electricity causes serious difficulties due to sticking of individual sheets of paper. Electrification of the paper is often the reason for the impossibility of printing at high speeds. In addition, strong adherence to paper dust is observed. Overdried paper is especially strongly electrified. Coated papers are electrified to a much lesser extent than natural papers.

versatility

The versatility of paper is the difference in the properties of the sides of a paper sheet. To varying degrees, versatility is observed in every paper made on a conventional flatbed paper machine. The reason for it lies in the existing technology of paper production.

The orientation of the fibers across the thickness of the paper is not the same. Due to the fact that the mesh orients the fiber predominantly in the machine direction, the arrangement of fibers in this direction on the mesh side is greater than on the top side.

Typically, the mesh side is rougher and thus less smooth than the top side.

Air bubbles and spots

When casting a paper web, one of the undesirable components of the mass is air. Air bubbles in paper are easy to detect when viewed through the light. They look like translucent round spots.

In the production of multilayer cardboard, the presence of air in the stock leads to a noticeable decrease in interlaminar strength and delamination of the cardboard is often observed. It has also been established that the presence of a large amount of air in the paper pulp leads to a decrease in the mechanical strength of the paper; its smoothness decreases, the structure of the sheet deteriorates, and air permeability increases.

The appearance of spots on paper is associated with the ingress of various kinds of foreign matter into the paper mass or onto the surface of the paper: litter, fire, oil, paint, coal particles, mucus, resin.

5. Requirements for regulatory documentation for paper quality indicators

The quality of paper is characterized by consumer properties, the indicators of which are regulated by standards. The most important of these properties are the composition of fibrous semi-finished products, weight 1 m 2, thickness, density, smoothness, degree of sizing, ash content, whiteness and grade. It is also characterized by tensile strength, linear deformation when moistened and dried, transparency, air permeability and other properties.

Examination of paper is carried out for compliance with the requirements of GOSTs for quality indicators of paper of various types. So each type of paper has its own requirements for the values ​​of quality indicators. By examining paper samples and determining the values ​​of quality indicators, experts can draw conclusions about the compliance of this type of paper with the requirements and its quality or the presence of defects. As well as measuring and calculating the values ​​of the quality indicators of the examined paper sample, the type of which is required to be determined, the experts can determine the type by comparing the obtained values ​​​​of the indicators with the values ​​\u200b\u200bpresented in the GOSTs.

The main properties of paper and their indicators:

1. Functional - determine the compliance of the paper with its intended purpose.

a) Weight 1 m 2. Depends on the type and composition of the fibers, the degree of grinding, the type and amount of fillers and other components.

The mass of drawing paper should be equal to 52 ± 2 g, cover paper of the highest grade - 110 ± 7 g, first grade 80 ± 4 g, drawing grades B, F, A, O - 160 ± 7, 135 ± 6, 200 ± 8, 100 ± 5 etc.

b) Thickness is measured in micrometers or millimeters. Depending on the purpose, paper is produced in different thicknesses.

c) The linear density is determined by dividing the mass of 1m2 by the thickness of the paper and is expressed in g/cm3. For example, the density of drawing paper grades B, F, A, O should be - 0.65, 0.86, 0.60, 0.63

d) Water and moisture permeability, air permeability characterize special-purpose paper (for example, parchment, subparchment, etc.). The values ​​of the moisture permeability index are determined by the measuring method described in GOST 9841-94 “Paper and cardboard. Method for determining water resistance.

2. Reliability. Causes the preservation of the main parameters of the paper in the process of its use.

a) Tensile strength is characterized by breaking length in meters or breaking load. By tensile strength, paper is divided into very strong - over 5000 m (paper tracing paper), strong - 3500 - 5000 m (drawing paper), medium strength - 2000-3500 m (writing), weak - up to 2000 m (blotting paper).

b) Fracture resistance is determined using a special device by repeated double bending of paper strips by 180 degrees with some tension until a complete fracture (rupture). For drawing paper, this figure is 500, for mailing paper it must be at least 15, and so on.

c) Punching resistance - the ability of paper to resist forces acting perpendicular to its surface (kgf / cm2). This indicator is of great importance for carbon paper, since it experiences significant letter pressure when printing. This indicator is determined using a hydraulic device with an electric drive by the method described in GOST 13525.8-86 “Fibrous semi-finished products, paper and cardboard. Method for determining bursting resistance. For drawing paper grades B, F, A, O, this indicator should be equal to - 196, 180, 150, 157 kPa.

d) Resistance to deformation - the ability of paper to maintain its size and shape when moistened and then dried.

e) Paper moisture - the amount of moisture contained in the paper. Paper easily accepts and quickly releases moisture, while changing its linear dimensions. The standard moisture content of printed papers is 7±1%. High humidity not only leads to deformation and change in the size of the sheet, but also greatly reduces the strength of the paper. Low humidity increases the rigidity and brittleness of the paper, which leads to a deterioration in the perception of ink during printing and a strong increase in the degree of electrification of the paper when the paper passes through the path of the equipment, for example, in a printing press. The moisture content of drawing transparent paper should be 6.0 ± 1.0%, drawing paper - 4-7%, paper for postal documents 5-8%, writing paper 5 ± 1.0.

3. Ergonomic properties characterize the usability of paper.

a) The degree of sizing. It is expressed in millimeters and is estimated by the size of the stroke applied with ink, ink, which did not pass to the reverse side of the sheet (after the final drying of the ink). The degree of sizing of different types of paper is from 0.5 to 2 mm. For drawing transparent paper, the indicator should be 1.2 ± 0.2, for cover notebook - 1.0, for drawing paper of various brands 1.8 - 2.0, for writing paper of various brands - 1.2 - 1.6 mm .

b) Smoothness. It characterizes the degree of paper surface treatment. Smoothness is expressed as the number of seconds required to pass 10 cm3 of air between the surface of a paper sample and a polished glass plate at a constant pressure of 1 kgf/cm3 on the paper. This indicator is determined using a special pneumatic device by the method described in GOST 12795-89. “Paper and cardboard. Beck's method for determining smoothness. The smoothness of paper for postal documents should be equal to 70 s, for writing paper of various brands - 100 - 220, 90 - 200, 80 - 250, etc.

The glossiness or dullness of paper also depends on the microgeometry of its surface. Very smooth papers will be glossy, rough papers will be matte.

4. Aesthetic properties. Characterized by the appearance and finish of the paper.

a) Whiteness of paper - the property of paper to diffusely reflect the light flux in the blue region of the spectrum. The whiteness index is expressed as a percentage relative to the white standard (plate coated with barium sulphate).

The whiteness index is determined by a photometric device by the method described in GOST 30113-94 “Paper and cardboard. Method for determining whiteness "

The degree of whiteness of some types of paper: Coated with optical brightener - 84%, Coated without optical brightener - 78%, Printed paper with optical brightener - 83%, Same without - 78%, Printed paper with white wood pulp - 72%, Newsprint paper - 65%, writing paper without optical brightener - 64-80% (for different brands), the same with optical brightener - 80 - 85%.

b) Color. Determined for colored papers by comparison with color standards.

c) Hue. Should correspond to the shade of the standard sample or standard.

d) Transparency - the property of paper to transmit (absorb) or not transmit (reflect) light flux. If the paper transmits light rays, then it is transparent. For testing, a photometric device such as a Zeiss leukometer, zonal reflectance plates, and a black substrate are used. Tests are carried out according to the method described in GOST 8874-80. "Paper. Methods for determining transparency and opacity. For example, for drawing paper, transparency should be at least 44%.

e) Weediness. It is characterized by the number of foreign inclusions ranging in size from 0.5 to 2 mm on an area of ​​1 m 2, having a different color than the tone of the paper on both sides of the sheet. Permissible weediness of writing paper - 125-200, drawing - 200, drawing - 100-200.

f) Ash content of paper - the proportion of the mass of mineral substances in the form of an ash residue in paper, expressed as a percentage. Determined by the method described in GOST 7629-93. “Paper and cardboard. Ash determination method”. For example, for paper for postal documents, this figure should be at least 7%.

5. The main factors that form the consumer properties of paper are the raw materials and materials from which fibrous semi-finished products are formed.

The composition of fibrous semi-finished products is determined by examining samples, as described in GOST 7500-85. Paper and cardboard. Methods for determining the composition of the fiber. For example, the composition according to the fiber of drawing transparent paper: cotton waste 25%, sulphate bleached softwood pulp grades KhB-5, KhB-6 - 75%. By examining the composition of paper, one can determine its type if it is unknown or determine whether the number of components in the test sample meets the requirements of regulatory documents or whether there are deviations leading to a decrease in the consumer properties of paper and its quality.

6. Production and properties of paper

Paper production

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

The production of cellulose is associated with the mechanical processing of wood and then carrying out chemical reactions with sawdust.

Trees are crushed to small sawdust. These sawdust are placed in a boiling solution containing NaHSO4 (sodium hydrosulfide) and SO2 (sulfur dioxide). Boiling is carried out at high pressure (0.5 MPa) and for a long time (about 12 hours). In this case, a chemical reaction occurs in the solution, as a result of which the substance hemicellulose and the substance lignin are obtained (lignin is a substance that is a mixture of aromatic hydrocarbons or an aromatic part of a tree), as well as the main product of the reaction - pure cellulose, which precipitates in a container where a chemical reaction takes place. In addition, in turn, lignin interacts with sulfur dioxide in solution, resulting in ethyl alcohol, vanillin, various tannins, and food yeast.

Cellulose can be obtained from any type of wood, mainly from low-resinous wood species - spruce, fir, beech - which can be processed by any of the cooking methods used in the industry. Resinous rocks (larch, pine) are processed by alkaline methods.

For the production of one ton of pulp for various purposes, about 4-5 m 3 of wood is required.

The process of obtaining cellulose is associated with the grinding of the sediment with the help of rolls, as a result of which cellulose particles of about 1 mm are obtained. When such particles fall 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.

At the next stage, paper is given its main properties: density, color, strength, porosity, smoothness, for which clay, titanium oxide, barium oxide, chalk, talc and additional substances that bind cellulose fibers are added to the cellulose container.

Further, the cellulose fibers are treated with a special adhesive based on resin and rosin. It contains rubber. If potassium alum is added to this adhesive, 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 the moving mesh, where it is pressed and dried. Here the formation of the paper web is already taking place.

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.

The most common is the so-called canteen (flat mesh) paper machine. The paper machine consists of wire, press and dryer parts, calender and reel. The paper mass flows in a continuous stream onto the moving mesh of the machine, closed in a ring, where the ebb, dehydration and compaction of the paper web take place. Further dehydration and compaction of the web is carried out in the press section, formed by several roller presses, between the shafts of which the paper web is transported throughout the entire process by a woolen cloth serving as an elastic gasket. The final removal of water takes place in the drying section, where the paper web alternately comes into contact with its surfaces with iron grinding cylinders heated from the inside by steam, arranged in a checkerboard pattern in two tiers. The surface of the paper is smooth due to the fact that it is pressed against the cylinders by the upper and lower felts. Then the paper web is finished in a calender, which is a vertical battery of 5-8 metal shafts. When moving between the shafts from top to bottom, the web becomes smoother, compacted and leveled in thickness. The resulting web of paper is wound on rolls on the reel, which is a forcedly rotated cylinder, against which the roller with the paper wound on it is pressed.

Paper properties

The properties of paper determine its appearance, quality and purpose. These include - structural, geometric, mechanical, optical, chemical, electrical and properties determined using a microscope.

The structural and geometric properties of paper include parameters such as weight, thickness, smoothness, bulk, lumen and porosity.

The mechanical properties of paper can be divided into strength and deformation properties. Deformation properties are manifested when external forces act on the material and are characterized by a temporary or permanent change in the shape or volume of the body. During the main technological operations of printing, paper is subjected to significant deformation of the paper, for example: stretching, compression, bending.

The main indicators of optical properties are: whiteness, opacity, transparency (opacity), gloss and color.

The chemical properties of paper are determined mainly by the type of wood used, the method and degree of pulping and bleaching, as well as the type and amount of non-fibrous components added, and are important because they determine the physical, electrical and optical properties.

Structural andgeometric properties. According to GOST R53636 -2 009 "Pulp, paper,cardboard. Terms and Definitions»

Mass or weight.

The mass (or weight) of one square meter of paper is the most common indicator, since most papers are sold by weight of 1m 2. The mass of paper is more often referred to as a unit of area than to a unit of volume (as is done with respect to other materials), because paper is used in the form of a sheet and area in this case plays a more important role than volume. According to the accepted classification, the mass of 1 m 2 of printed paper can be from 40 to 250 g. Papers weighing more than 250g/m2 are classified as boards.

Thickness

The thickness of the paper, measured in microns (µm), determines both the permeability of the paper in the printing press and the consumer properties - primarily strength - of the finished product.

Smoothness

Smoothness characterizes the state of the surface of the paper, due to mechanical finishing, and determines the appearance of the paper - rough paper, as a rule, is unattractive in appearance. Smoothness is important for writing papers, for printing papers, and also when gluing paper.

The opposite of smoothness is roughness, which is measured in microns (µm). It directly characterizes the microrelief of the paper surface. One of these two values ​​is always present in paper specifications.

Bulk

Bulkness is measured in cubic centimeters per gram (cc/g). The bulk of printed papers ranges on average from 2 cm 3 /g (for loose, porous) to 0.73 cm 3 /g (for high-density calendered papers). In practice, this means that if you take a thicker paper of a smaller gram, then with equal opacity there will be more sheets in a ton of paper.

Clearance

The clearance of paper characterizes the degree of uniformity of its structure, that is, the degree of uniformity of the distribution of fibers in it. The lumen of the paper is judged by observation in transmitted light. Paper with a highly cloudy gap is extremely inhomogeneous. Its thin spots are also the least durable and easily pass water, ink, printing ink. Due to the uneven perception of the printing ink by the paper, printing on cloudy paper is of poor quality.

Paper with a cloudy gap is difficult to color, multi-tone clouds are formed. Thick sections of the paper web are colored more intensively and less intensively thin ones.

Porosity

Porosity directly affects the absorbency of the paper, that is, its ability to accept printing ink, and may well serve as a characteristic of the structure of the paper. Paper is a porous capillary material; at the same time, macro- and microporosity are distinguished. Macropores, or simply pores, are spaces between fibers filled with air and moisture. Micropores, or capillaries, are the smallest spaces of indefinite shape penetrating the coating layer of coated papers, as well as spaces formed between filler particles or between them and the walls of cellulose fibers in uncoated papers. There are also capillaries inside cellulose fibers. All uncoated, not overly compacted papers, such as newsprint, are macroporous. The total pore volume in such papers reaches 60% or more, and the average pore radius is about 0.160.18 µm. Such papers absorb paint well due to the loose structure, that is, the highly developed inner surface.

Mechanical properties

Mechanical strength.

The tensile strength of paper does not depend on the strength of individual components, but on the strength of the paper structure itself, which is formed during the paper production process. This property is usually characterized by breaking length in meters or breaking force in Newtons. So, for softer printing papers, the breaking length is at least 2500 m, and for hard offset papers this value increases to 3500 m and more.

Break resistance.

The fracture resistance index depends on the length of the fibers from which the paper is formed, on their strength, flexibility and on the bonding forces between the fibers. Therefore, the highest fracture resistance is characterized by paper, consisting of long, strong, flexible and tightly bonded fibers.

Burst resistance.

This indicator is of great importance for wrapping papers. It is related to the breaking load of paper and its elongation at break.

Extensibility.

Paper elongation to break, or its extensibility, characterizes the ability of paper to stretch. This property is especially important for packaging paper, sack paper and cardboard, for the production of stamped products, for the base of waxed paper used for automatic wrapping.

Softness.

The softness of paper is related to its structure, that is, its density and porosity. Thus, large-pore newsprint can deform under compression up to 28%, and for dense coated paper, the compression deformation does not exceed 68%.

Linear deformation when moistened.

The increase in the dimensions of a wetted sheet of paper in its width and length, expressed as a percentage of the original dimensions of a dry sheet, is called linear deformation when wetted. The values ​​of paper deformation when wet and permanent deformation are important indicators for many types of paper (for offset, chart, cartographic, for the base of the photo substrate, for paper with watermarks). High values ​​of these indicators lead to misalignment of ink contours during printing and, as a result, to low-quality printing. However, it should be noted that in GOST 12057-81 “Paper and cardboard. Methods for determining linear deformation.» very stringent test conditions are laid down (wetting a calibrated strip of paper for a certain time), the use of which is impractical for most printed types of paper. European standards suggest the use of the term "moisture expansion", which determines the change in the linear dimensions of a strip of paper when the air humidity changes from 30 to 80%. High humidity dramatically reduces the mechanical tensile strength of the paper.

Optical properties

optical brightness.

Optical brightness is the ability of paper to reflect light diffusely and evenly in all directions.

White.

The true whiteness of a paper is related to its luminosity or absolute reflectivity, i.e. visual efficiency. Whiteness is based on the measurement of light reflection by white or almost white papers with one wavelength (GOST 30113-94 "Paper and cardboard. Method for determining whiteness." Provides 457 millimicrons, that is, in the visible spectrum) and is defined as the ratio of the amounts of incident and distributed reflected light (%).

Yellowing.

Paper yellowing is a term that conventionally refers to the decrease in its whiteness due to exposure to light rays or elevated temperature. Paper can be protected from light damage by storing it in a room without windows or with windows covered with thick curtains.

Opacity, or opacity.

Opacity is the ability of paper to transmit light rays. The opacity property of paper is determined by the total amount of light transmitted (diffuse and non-diffuse). Opacity is usually determined by the degree of penetration of the image into the test material, placed directly opposite the object in question.

The term "paper opacity" is more commonly used - the ratio of the amount of light reflected from a sheet lying on a black substrate to the light reflected by an opaque stack of this paper.

Transparency

Transparency is related in some way to opacity, but differs from it in that it is determined by the amount of light that passes through without scattering. The transparency ratio is a better estimate of highly transparent materials (cripples), while the opacity measurement is more suitable for relatively opaque papers.

Gloss or gloss.

Gloss (gloss) is a property of paper that expresses the degree of glossiness, gloss, or the ability of a surface to reflect light falling on it. This indicator can be thought of as the property of the paper surface to reflect light at a given angle. Thus, gloss (gloss) can be characterized as the ratio of the amount of light reflected in the specular direction to the amount of incident light.

Chemical properties.

Wet strength.

The wet strength of paper is judged by the degree to which it retains its original strength in the wet state, that is, according to the strength that it had before wetting, being in the air-dry state.

Humidity.

The moisture content of paper affects its weight, strength, immutability, dimensional stability and electrical properties. Humidity is very important in calendering, printing, coating and impregnation. When testing paper, it is usually conditioned in order to create a constant, well-defined humidity.

Ash content.

The ash content of paper depends on the quantitative content of fillers in its composition. High-strength paper should have a low ash content, as minerals reduce paper strength.

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