Paper is a thin material produced by pressing together the cellulose pulp moist fibers from wood, rags or grass, and drying them into flexible sheets. It is a versatile material with many uses, including writing, printing, packaging, cleaning, and a number of industrial and construction processes.
The pulsed paper-making process is said to have been developed in China at the beginning of the 2nd century, probably at the beginning of AD 105, by the court palace of Han Cai Lun, although the earliest archaeological pieces of paper date from the 2nd century BC in China. The modern pulp and paper industry is global, with China leading the production and the United States right behind it.
Video Paper
Histori
The oldest known archaeological fragment from a direct precursor to the date of modern paper into the 2nd century BC in China. The process of making pulp paper is thought to have originated from Cai Lun, a 2nd century Han court court judge.
In the 13th century, knowledge and paper use spread from China through the Middle East to medieval Europe, where the first water-powered paper mill was built. Since paper was introduced to the West through the city of Baghdad, it was first called bagdatikos . In the 19th century, industrialization greatly reduced the cost of paper making. In 1844, Canadian inventor Charles Fenerty and German F. G. Keller independently developed the process for making wood fibers.
Maps Paper
Initial fiber source
Prior to the industrialization of paper production, the most common source of fiber was the recycled fibers of used textiles, called fabrics. The fabrics are from hemp, linen and cotton. A process for removing printing ink from recycled paper was discovered by German lawyer Justus Claproth in 1774. Today this method is called deinking. New to the introduction of wood pulp in 1843 paper production does not depend on the recycled material of the ragpicker.
Etymology
The word "paper" is etymologically derived from the Latin papyrus , which is derived from the Greek ??????? ( papuros ), the word for Cyperus papyrus . Papyrus is a thick material, like paper produced from the pith of Cyperus papyrus, used in ancient Egypt and other Mediterranean cultures to be written before the introduction of papers to the Middle East and Europe. Although the word paper is etymologically derived from papyrus, both are produced very differently and the first development differs from that of the second. Papyrus is a natural plant fiber lamination, while paper is made from fibers that have been altered by maceration.
Papermaking
Pulping chemistry
To make pulp from wood, the process of making chemical pulp separates lignin from cellulose fibers. This is done by dissolving lignin in liquor, so it can be washed out of cellulose; This maintains the cellulose fiber length. Paper made from chemical pulp also known as wood-free paper - not to be confused with tree-free paper; this is because they do not contain lignin, which worsens over time. Pulp can also be bleached to produce white paper, but this consumes 5% of the fiber; the process of making chemical pulp is not used to make paper made of cotton, which is already 90% cellulose.
There are three major chemical refining processes: the sulphite process began in the 1840s and it was the dominant method as far before the second world war. The kraft process, discovered in the 1870s and first used in the 1890s, is now the most common strategy, one of the advantages being a chemical reaction with lignin, which produces heat, which can be used to run a generator. Most stripping operations using the kraft process are clean contributors to the power grid or use electricity to run adjacent paper mills. Another advantage is that this process recovers and reuses all inorganic chemical reagents. Pulp soda is another special process used for pulp, bagasse and hardwood with high silicate content.
Mechanical stripping
There are two main mechanical pulps: thermomechanical pulp (TMP) and pulpwood pulp (GW). In the TMP process, the wood is exfoliated and then fed to a heated steam distiller, where the chips are squeezed and converted into fibers between two steel discs. In the groundwood process, debarked logs are inserted into the grinder where they are pressed against the spinning stone to be made into fibers. Pulping mechanically does not remove lignin, so the yield is very high, & gt; 95%, but causes the resulting paper to become yellow and becomes brittle over time. Mechanical pulps have rather short fibers, resulting in weak paper. Although large amounts of electrical energy are required to produce mechanical slurry, the cost is cheaper than the chemical type.
Unlinked pulp
The paper recycling process can use chemical or mechanically produced pulses; by mixing it with water and applying the mechanical action the hydrogen bonds on the paper can be broken and the fibers separated again. Most recycled paper contains virgin fiber proportions for quality; in general, non-ink pulps have the same or lower quality than the paper collected.
There are three main classifications of recycled fibers.
- Mill ruptures or internal factory waste - It combines any unprocessed or modified paper grade created inside the paper mill itself, which then returns to the manufacturing system to be re-pulped back into paper. Paper out of specification is not sold and is therefore often not classified as recycled recycled native fibers, but most paper mills have been reusing their own waste fibers for years, long before recycling became popular.
- Waste waste - This is cut and processed waste, such as the rest of the guillotine and empty envelope waste; these are produced outside the paper mill and potentially enter the landfill, and are the original source of recycled fiber; this includes non-ink precursors (recycled material that has been printed but does not achieve the desired end-use, such as waste from printers and unsold publications).
- Waste waste - This is fiber from paper that has been used for final use purposes and includes office waste, magazine paper and newsprint. Since most of this material has been printed - either digitally or in more conventional ways such as lithography or rotogravure - it will be recycled like print paper or through a de-inking process first.
Recycled paper can be made from 100% recycled material or mixed with virgin pulp, although they are (generally) not as strong or as bright as paper made from the last.
Additive
In addition to fibers, the pulp may contain fillers such as chalk or clay china, which enhance its characteristics for printing or writing. Additives for the intended size can be mixed or applied to the paper web then in the manufacturing process; the purpose of that measure is to establish the correct absorption level of the surface according to the ink or paint.
Producing paper
The pulp is fed to a paper machine where it is formed as a paper net and the water is removed from it by pressing and drying.
Pressing the paper will forcibly remove the water; after the water is forced from the sheet, a special kind of flavor, not to be confused with the traditional ones, is used to collect water; while when making paper by hand, the ink sheet is used instead.
Drying involves the use of air or heat to remove water from the sheet of paper. In the early days of paper making, this was done by hanging sheets like laundry; In a more modern era, various forms of heated drying mechanisms are used. On the paper machine, the most common is the steam heated canister. It can reach temperatures above 200Ã ° Â ° F (93Ã, Â ° C) and is used in long order of more than forty cans where the heat produced by this can easily dry the paper up to less than six percent humidity.
Completed
The paper may undergo a size change to change its physical properties for use in various applications.
The paper at this time is not coated . Layered papers have thin layers of materials such as calcium carbonate or clay china applied to one or both sides to create surfaces that are more suitable for high resolution halftone screens. (Uncoated paper is seldom suitable for screens above 150 lpi.) Coated or uncoated paper may be polished on the surface with calendering. The coated paper is divided into matte, semi-matte or silk, and gloss. Gloss paper provides the highest optical density in the printed image.
The paper is then inserted into a roll if it will be used on a web printing machine, or cut into sheets for other printing processes or other purposes. The fibers in the paper basically run toward the machine. The sheets are usually cut "long-grain", ie with the grain parallel to the longer dimensions of the sheet. Continuous form paper (or continuous stationery) is cut wide with holes punched at the edges, and folded into piles.
Paper grain
All paper produced by a paper machine as a Fourdrinier Machine is a sticky paper, ie a web-loaded wire leaving a pattern that has the same density along the grain of paper and across the grain. Textured prints, watermarks and wire patterns that mimic handmade paper can be made by using the right rollers at a later stage of the machine.
The sliding paper does not indicate "indentations", which are small stripes that are commonly left on paper when they are handmade in prints made of rows of metal or bamboo wires. Laidlines are very close together. They walk perpendicular to the "chain chain", which is further apart. Handmade paper also shows "dekle edges", or rough and hairy borders.
Apps
Paper can be produced with a variety of properties, depending on the intended use.
- To represent the value: banknotes, bank notes, checks, security (see security paper ), vouchers and tickets
- To store information : books, notebooks, graph paper, magazines, newspapers, art, zines, letters
- For private use : diary, note to remind yourself, etc.; for temporary personal use: scratch paper
- For communication: between an individual and/or a group of people.
- For packaging: corrugated box, paper bag, envelope, Packing & amp; Paper Packaging, Paper string, Charta emporetica and wallpaper
- To clean: toilet paper, handkerchief, tissue, facial tissue and cat litter
- For construction: papier-mÃÆ' Â ¢ chÃÆ' Â ©, origami, paper plane, quilling, honeycomb paper, used as core material in composite materials, paper engineering, construction paper,/li>
- For other uses: sandpaper, sandpaper, blotting paper, litmus paper, universal indicator paper, paper chromatography, electrical insulation paper (see also dielectric and < permittivity ) and filter paper
It is estimated that paper-based storage solutions captured 0.33% of the total in 1986 and only 0.007% in 2007, although in absolute terms, the world's capacity to store information on paper increased from 8.7 to 19.4 petabytes. It is estimated that in 1986 paper-based mailings represented less than 0.05% of the world's telecom capacity, with a sharp downward trend after the introduction of digital technology on a large scale.
Type, thickness and weight
The thickness of the paper is often measured with caliper, which is usually given in thousandths of an inch in the United States and in micrometers (Ã,Âμm) worldwide. Paper may be between 0.07 and 0.18 millimeters (0.0028 and 0.0071 in) thick.
The paper is often marked by weight. In the United States, the weight set for paper is the weight of the rim, 500 sheets, of various "base sizes", before the paper is cut to size that is sold to the end consumer. For example, a ream of weighing 20 pounds, 8.5 inches (216 mm) deep, weighs 5 pounds, having been cut from larger sheets into four sections. In the United States, printed paper is generally 20 pounds, 24 pounds, or 32 pounds at most. Stock cover is generally 68 pounds, and 110 pounds or more is considered card stock.
In Europe, and other regions using an ISO 216 paper sizing system, the weight is expressed in grams per square meter (g/m 2 or usually only g) of paper. Printed paper is generally between 60 g and 120 g. Anything heavier than 160 g is considered a card. Therefore the weight of the rim depends on the paper dimension and its thickness.
Most commercial paper sold in North America is cut to standard paper sizes based on custom units and is determined by the length and width of a sheet of paper.
The ISO 216 system used in most other countries is based on the surface area of ​​a sheet of paper, not on the width and length of the sheet. It was first adopted in Germany in 1922 and generally spread when countries adopted the metric system. The largest standard size paper is A0 (A zero), measuring one square meter (about 1189 × 841 mm). A1 is half the size of A0 sheet (ie, 594 mm-841 mm), such that two A1 sheets are placed side by side together with one sheet A0. A2 is half the size of a sheet A1, and so on. Common sizes used in offices and homes are A4 and A3 (A3 is the size of two A4 sheets).
Paper density ranges from 250 kg/m 3 (16 pounds/cuÃ, ft) for tissue paper up to 1,500 kg/m 3 special paper. Print paper is about 800 kg/m 3 (Â £ 50/cuÃ, ft).
Paper can be classified into seven categories:
- Print a variety of .
- Paper wrapping for the protection of goods and merchandise. These include candles and kraft paper.
- Written paper suitable for stationery needs. These include ledgers, banks, and bond paper.
- Blotting paper contains little or no size.
- Drawing paper is usually with rough surfaces used by artists and designers, including cartridge paper.
- Handmade paper includes most of the decorative paper, Ingres paper, Japanese paper and tissue, all marked by a lack of grain directions.
- Special paper including cigarette paper, toilet paper, and other industrial papers.
Some types of paper include:
Paper stability
Most of the early paper made of wood pulp contains a large amount of alum, a variety of highly acidic aluminum sulfate salts. The aluminum is added to the paper to help in size, making it somewhat waterproof so the ink does not "run" or spread uncontrollably. Early paper makers did not realize that the alum they added freely to cure almost every problem encountered in making their products would ultimately harm. The cellulose fibers that make up the paper are hydrolyzed by acid, and the presence of alum will eventually degrade the fibers until the paper is destroyed in a process known as "slow fire". Documents written on rag paper are significantly more stable. The use of non-acid additives to make paper more common, and the stability of these papers is less of a problem.
Paper made of mechanical pulp contains a large number of lignin, a major component in wood. In the presence of light and oxygen, lignin reacts to give a yellow material, which is why newsprint and other mechanical paper are yellow with age. Paper made from bleached kraft or sulphite pulp does not contain significant amounts of lignin and is therefore more suitable for books, documents and other applications where paper whiteness is essential.
Paper made from wood pulp does not have to be more durable than lap paper. The behavior of paper aging is determined by its manufacture, not the original source of the fiber. Furthermore, a test sponsored by the Library of Congress proves that all paper is at risk of acid decay, since cellulose itself produces formic, acetic, lactic and oxalic acids.
Mechanical pulping produces nearly a ton of pulp per ton of dry wood used, which is why mechanical pulp is sometimes referred to as "high yield" pulp. With almost twice as much yield as chemical breaking, mechanical pulps are often cheaper. Paperback books and mass market newspapers tend to use mechanical papers. Book publishers tend to use acid-free paper, made from wholly bleached chemical pulp for hardback books and paperback trade books.
Environmental impact
Paper production and use have a number of adverse effects on the environment.
Paper consumption worldwide has increased 400% in the last 40 years which led to increased deforestation, with 35% of the trees being harvested used for paper making. Most paper companies also plant trees to help regenerate the forest. Deforestation of old growth forests accounts for less than 10% of wood pulp, but is one of the most controversial issues.
Waste paper accounts for up to 40% of total waste produced in the United States each year, which adds up to 71.6 million tonnes of paper waste per year in the United States alone. The average office worker in the US prints 31 pages every day. Americans also use in the order of 16 billion paper cups per year.
The bleaching of conventional wood pulps using chlorine elements produces and releases into the environment a large number of chlorinated organic compounds, including chlorinated dioxins. Dioxin is recognized as a persistent environmental polluter, regulated internationally by the Stockholm Convention on Persistent Organic Pollutants. Dioxin is highly toxic, and health effects in humans include reproductive, developmental, immune and hormonal problems. They are known to be carcinogenic. More than 90% of human exposure is through food, especially meat, milk, fish and shellfish, as dioxin accumulates in the food chain in animal fat tissue.
Future
Some manufacturers have started using new alternatives that are significantly more environmentally friendly than expanded plastic packaging. Made of paper, and known commercially as PaperFoam, the new packaging has mechanical properties that are very similar to some expanded plastic packaging, but biodegradable and can also be recycled with plain paper.
With increasing environmental concerns about synthetic coatings (such as PFOAs) and higher prices of hydrocarbon-based petrochemicals, there is a focus on zein (maize protein) as paper coatings in high-grease applications such as popcorn pouches.
Also, synthetics such as Tyvek and Teslin have been introduced as print media as a more durable material than paper.
See also
Note
References
- Burns, Robert I. (1996). "Paper came to the West, 800-1400". At Lindgren, Uta. EuropÃÆ'¤ische Technik im Mittelalter. 800 bis 1400. Tradition und Innovation (4th ed.). Berlin: Gebr. Mann Verlag. pp.Ã, 413-422. ISBN: 3-7861-1748-9. Tsien, Tsuen-Hsuin (1985). Needham, Joseph, ed. Paper and Printing . Science and Civilization in China, Chemical and Chemical Technology. V (part 1). Cambridge University Press.
- "Dual Document" in Detecting Truth: Fache, Forgeries and Trickery, virtual museum exhibit in the Library and Archives of Canada
Further reading
- Alexander Monro, The Paper Trail: Unexpected History of the World's Largest Invention , Allen Lane, 2014
External links
- Technical Association of the Pulp and Paper Industry website (TAPPI)
- Papers at EncyclopÃÆ'Â|dia Britannica
- How are papers made? at The Straight Dope, November 22, 2005
- 'Paper thickness reference guidelines
- A thirteen minute video on modern paper production systems, from Sappi
Source of the article : Wikipedia
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