Paper is a thin material mainly used for writing upon, printing upon or for packaging. It is produced by pressing together moist fibers Fiber, also spelled fibre, is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread. They are very important in the biology of both plants and animals, for holding tissues together. Human uses for fibers are diverse. They can be spun into filaments, string or rope, used as a component, typically cellulose Cellulose is an organic compound with the formula n, a polysaccharide consisting of a linear chain of several hundred to over ten thousand β(1→4) linked D-glucose units pulp derived from wood Wood is a hard, fibrous tissue found in many plants. It has been used for centuries for both fuel and as a construction material for several types of living areas such as houses. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression. In the strict sense wood is produced as, rags or grasses Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges (Cyperaceae) and the rushes (Juncaceae). The true grasses include cereals, bamboo and the grasses of lawns (turf) and grassland, and drying them into flexible sheets.
Paper is a versatile material with many uses. Whilst the most common is for writing Writing is the representation of language in a textual medium through the use of a set of signs or symbols . It is distinguished from illustration, such as cave drawing and painting, and non-symbolic preservation of language via non-textual media, such as magnetic tape audio and printing Printing is a process for reproducing text and image, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing upon, it is also widely used as a packaging Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of design, evaluation, and production of packages. Packaging can be described as a coordinated system of preparing goods for transport, warehousing, logistics, sale, and end use. Packaging material, in many cleaning Cleanliness is the absence of dirt, including dust, stains, bad smells and garbage. Purposes of cleanliness include health, beauty, absence of offensive odor, avoidance of shame, and to avoid the spreading of dirt and contaminants to oneself and others. In the case of glass objects such as windows or windshields, the purpose can also be products, in a number of industrial and construction processes, and occasionally as a food ingredient Edible paper, as the name implies, is a paper that may be consumed without harsh effects on a normal human digestive system. Usually, the paper has no flavor and very little texture, particularly in Asian cultures.
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History
Main article: History of paper The history of paper began, so far as we know, in Ancient Egypt aprox. 3,700BC - 3,200BC with the use of Papyrus as a medium for written records, a considerable advance over the technique employed by the Sumerians of writing on clay tablets. The transition from clay tablets to Papyrus was as revolutionary as the step from manuscripts to printing Further information: Science and technology of the Han Dynasty The Han Dynasty of ancient China, divided between the eras of Western Han (206 BCE – 9 CE, when the capital was at Chang'an), Xin Dynasty of Wang Mang (r. 9–23 CE), and Eastern Han (25–220 CE, when the capital was at Luoyang, and after 196 CE at Xuchang), witnessed some of the most significant advancements in premodern Chinese science and and List of Chinese inventions China has been the source of many significant inventions, including the Four Great Inventions of ancient China: papermaking, the compass, gunpowder, and printing . The list below contains these and other inventionsThe word paper derives from the Greek term for the ancient Egyptian Ancient Egypt was an ancient civilization of eastern North Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. The civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh, and it developed over the next three millennia. Its history writing material called papyrus Papyrus is a thick paper-like material produced from the pith of the papyrus plant, Cyperus papyrus, a wetland sedge that was once abundant in the Nile Delta of Egypt, which was formed from beaten strips of papyrus plants Cyperus papyrus is a monocot belonging to the sedge family Cyperaceae. It is a herbaceous perennial native to Africa, and forms tall stands of reed-like swamp vegetation in shallow water. The immediate predecessor to modern paper is believed to have originated in China in approximately the 2nd century AD, although there is some evidence for it being used before this date.[citation needed] Papermaking In papermaking a dilute suspension of fibers in water is drained through a screen, so that a mat of randomly interwoven fibers is laid down. Water is removed from this mat of fibers by pressing and drying to make paper. Most paper is made from wood pulp, but other fiber sources such as cotton and textiles may be used is considered to be one of the Four Great Inventions of Ancient China The Four Great Inventions of ancient China are four inventions that are celebrated in Chinese culture for their historical significance and as signs of ancient China's advanced science and technology, since the first pulp papermaking process was developed in China China is seen variously as an ancient civilization extending over a large area in East Asia, a nation and/or a multinational entity during the early 2nd century AD by the Han The Han Dynasty was the second imperial dynasty of China, preceded by the Qin Dynasty (221–206 BCE) and succeeded by the Three Kingdoms (220–265 CE). It was founded by the peasant rebel leader Liu Bang, known posthumously as Emperor Gaozu of Han. It was briefly interrupted by the Xin Dynasty (9–23 CE) of the former regent Wang Mang. This court eunuch Cai Lun. China used paper as an effective and cheap alternative to silk, letting them sell more silk, leading to a Golden Age The term Golden Age comes from Greek mythology and legend and refers to the first in a sequence of four or five (or more) Ages of Man, in which the Golden Age is first, followed in sequence, by the Silver, Bronze, and Iron Ages, and then the present, a period of decline. By extension "Golden Age" denotes a period of primordial peace,.
The use of paper spread from China through the Islamic world The term Muslim world has several meanings. In a cultural sense, it refers to the worldwide community of Muslims, adherents of Islam. This community numbers about 1.3-1.5 billion people, roughly one-fifth of the world population. This community is spread across many different nations and ethnic groups connected by religion and a shared sense of and entered production in medieval Europe The Middle Ages is a period of European history from the 5th century through the 15th century. The period followed the fall of the Western Roman Empire in 476, and preceded the Early Modern Era. It is the middle period in a three-period division of history: Classical, Medieval, and Modern. The term "Middle Ages" (medium aevum) was coined in the 13th century, where the first water-powered paper mills A paper mill is a factory devoted to making paper from vegetable fibres such as wood pulp, old rags and other ingredients using a Fourdrinier machine or other type of paper machine were built and mechanization of papermaking began.[1] The industrial production of paper in the early 19th century caused significant cultural changes worldwide, allowing for relatively cheap exchange of information in the form of letters, newspapers and books for the first time. In 1844, both Canadian inventor Charles Fenerty Charles Fenerty , is a Canadian inventor who invented the wood pulp process for papermaking, which was first adapted into the production of newsprint. Fenerty was also a poet (writing over 32 known poems). He also did extensive traveling throughout Australia between the years 1858 to 1865 (living in the heart of the Australian gold rushes) and German inventor F.G. Keller had invented the machine and process for pulping wood for the use in paper making.[2] This would end the nearly 2000-year use of pulped rags and start a new era for the production of newsprint and eventually all paper out of pulped wood.
Papermaking
The microscopic structure of paper: Micrograph A micrograph or photomicrograph is a photograph or similar image taken through a microscope or similar device to show a magnified image of an item. Canadian inventor Reginald Aubrey Fessenden is credited with inventing photomicrography. A microphotograph is a very small picture, e.g. a microdot of paper autofluorescing Autofluorescence is the fluorescence of other substances than the fluorophore of interest. It increases the background signal under ultraviolet Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nm to 400 nm, and energies from 3eV to 124 eV. It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the colour violet illumination. The individual fibres in this sample are around 10 µm A micrometre is one millionth of a metre, or equivalently one thousandth of a millimetre or one thousand nanometres. It can also be written in scientific notation as 1×10−6 m, meaning 1⁄1000000 m in diameter. Main article: Papermaking In papermaking a dilute suspension of fibers in water is drained through a screen, so that a mat of randomly interwoven fibers is laid down. Water is removed from this mat of fibers by pressing and drying to make paper. Most paper is made from wood pulp, but other fiber sources such as cotton and textiles may be usedChemical pulping
Main articles: kraft process The kraft process describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers. The process entails treatment of wood chips with a mixture of sodium hydroxide and sodium sulfide that break the bonds that link lignin to the cellulose. The process name is derived from German kraft, meaning strength/power;, sulfite process The sulfite process produces wood pulp which is almost pure cellulose fibers by using various salts of sulfurous acid to extract the lignin from wood chips in large pressure vessels called digesters. The salts used in the pulping process are either sulfites , or bisulfites (HSO3−), depending on the pH. The counter ion can be sodium (Na+),, and soda pulping Soda pulping is a chemical process for making wood pulp with sodium hydroxide as cooking chemical. In the Soda-AQ process anthraquinone may be used as a pulping additive to decrease the carbohydrate degradation. The soda process has still limited use for easy pulped materials like straws and some hardwoods. It gives pulp with lower tear strengthThe purpose of a chemical pulping process is to break down the chemical structure of lignin Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood. It is one of the most abundant organic polymers on Earth, exceeded only by cellulose, and render it soluble in the cooking liquor, so that it may be washed from the cellulose Cellulose is an organic compound with the formula n, a polysaccharide consisting of a linear chain of several hundred to over ten thousand β(1→4) linked D-glucose units fibers. Because lignin holds the plant cells together, chemical pulping frees the fibres and makes pulp. The pulp can also be bleached Bleaching of wood pulp is the chemical processing carried out on various types of wood pulp to decrease the color of the pulp, so that it becomes whiter. The main use of wood pulp is to make paper where whiteness is an important characteristic. The processes and chemistry described in this article are also applicable to the bleaching of non-wood to produce white paper for printing Printing is a process for reproducing text and image, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing, painting Painting is the practice of applying paint, pigment, color or other medium to a surface . The application of the medium is commonly applied to the base with a brush but other objects may be used. In art the term describes both the act and the result which is called a painting. Paintings may have for their support such surfaces as walls, paper, and writing Writing is the representation of language in a textual medium through the use of a set of signs or symbols . It is distinguished from illustration, such as cave drawing and painting, and non-symbolic preservation of language via non-textual media, such as magnetic tape audio. Chemical pulps tend to cost more than mechanical pulps Pulp is a dry fibrous material prepared by chemically or mechanically separating fibres from wood, fibre crops or waste paper, largely due to the low yield, 40–50% of the original wood. Since the process preserves fibre length, however, chemical pulps Pulp is a dry fibrous material prepared by chemically or mechanically separating fibers from wood, fiber crops or waste paper tend to make stronger paper. Another advantage of chemical pulping is that the majority of the heat and electricity Electricity is a general term that encompasses a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning and static electricity, but in addition, less familiar concepts, such as the electromagnetic field and electromagnetic induction needed to run the process is produced by burning the lignin Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood. It is one of the most abundant organic polymers on Earth, exceeded only by cellulose, removed during pulping.
Paper made from chemical pulps are also known as wood-free papers. Not to be confused with tree-free paper.
The Kraft process The kraft process describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers. The process entails treatment of wood chips with a mixture of sodium hydroxide and sodium sulfide that break the bonds that link lignin to the cellulose. The process name is derived from German kraft, meaning strength/power; is the most commonly practiced strategy for pulp manufacturing and produces especially strong, unbleached papers that can be used directly for bags and boxes but are often processed further, e.g. to make corrugated cardboard Corrugated fiberboard is a paper-based material consisting of a fluted corrugated sheet and one or two flat linerboards. It is widely used in the manufacture of corrugated boxes and shipping containers.
Mechanical pulping
There are two major mechanical pulps, thermo mechanical pulp (TMP) and groundwood pulp (GW). In the TMP process, wood is chipped and then fed into large steam-heated refiners where the chips are squeezed and fibreized between two steel discs. In the groundwood process, debarked logs are fed into grinders where they are pressed against rotating stones and fibreized. Mechanical pulping does not remove the lignin Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood. It is one of the most abundant organic polymers on Earth, exceeded only by cellulose,, so the yield is very high, >95%, but also causes paper made from this pulp to yellow and become brittle over time. Mechanical pulps have rather short fibre lengths and produce weak paper. Although large amounts of electrical energy Electric potential energy aka "electrostatic potential energy" is a potential energy associated with the conservative Coulomb forces within a defined system of point charges. The term "electrostatic potential energy" is preferred here because it seems less likely to be misunderstood. The reference zero is usually taken to be a are required to produce mechanical pulp, it costs less than chemical pulp.
Deinked pulp
Main article: deinking Deinking is the industrial process of removing printing ink from paperfibers of recycled paper to make deinked pulpPaper recycling Paper recycling is the process of recovering waste paper and remaking it into new paper products. There are three categories of paper that can be used as feedstocks for making recycled paper: mill broke, pre-consumer waste, and post-consumer waste. Mill broke is paper trimmings and other paper scrap from the manufacture of paper, and is recycled processes can use either chemical or mechanical pulp. By mixing with water and applying mechanical action the hydrogen Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of 1.00794 u (1.007825 u for Hydrogen-1), hydrogen is the lightest and most abundant chemical element, constituting roughly 75 % of the Universe's elemental mass. Stars in the main sequence are mainly composed of hydrogen in its bonds in the paper can be broken and fibres separated again. Most recycled paper contains a proportion of virgin fibre in the interests of quality. Generally deinked pulp is of the same quality or lower than the collected paper it was made from.
There are three main classifications of recycled fibre:.
- Mill Broke or Internal Mill Waste — this incorporates any substandard or grade-change paper made within the paper mill which then goes back into the manufacturing system to be repulped back into paper. Such out-of-specification paper is not sold and is therefore often not classified as genuine reclaimed recycled fibre. However, most paper mills have been recycling their own waste fibre for many years, long before recycling become popular.
- Preconsumer Waste — this is offcuts and processing waste, such as guillotine trims and envelope blank waste. This waste is generated outside the paper mill and could potentially go to landfill, and is a genuine recycled fibre source. Also includes de-inked preconsumer (recycled material that has been printed but did not reach its intended end use, such as waste from printers and unsold publications).[3]
- Postconsumer waste — this is fibre from paper which has been used for its intended end use and would include office waste, magazine papers and newsprint. As the vast majority of this paper has been printed (either digitally or by more conventional means such as litho or gravure), it will either be recycled as printed paper or go through a deinking process first.
Recycled papers can be made from 100% recycled materials or blended with virgin pulp. They are (generally) not as strong nor as bright as papers made from virgin pulp.
Additives
Besides the fibres, pulps may contain fillers such as chalk Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under relatively deep marine conditions from the gradual accumulation of minute calcite plates (coccoliths) shed from micro-organisms called coccolithophores. It is common to find chert or flint or china clay, which improve the characteristics of the paper for printing or writing. Additives for sizing purposes may be mixed into the pulp and/or applied to the paper web later in the manufacturing process. The purpose of sizing is to establish the correct level of surface absorbency to suit the ink or paint.
Producing paper
Main articles: Papermachine and handmade paper See also: Air-laid paperThe pulp is feed to a paper machine where it is formed as a paper web and the water is removed from it by pressing and drying.
Pressing the sheet removes the water by force. Once the water is forced from the sheet, felt (not to be confused with the traditional felt) is used to collect the water. When making paper by hand, a blotter sheet is used.
Drying involves using air and or heat to remove water from the paper sheet. In the earliest days of papermaking this was done by hanging the paper sheets like laundry. In more modern times, various forms of heated drying mechanisms are used. On the paper machine, the most common is the steam-heated can dryer. These dryers can heat to temperatures above 200°F (93°C) and are used in long sequences of more than 40 cans. The heat produced by these can easily dry the paper to less than 6% moisture.
Finishing
The paper may then undergo sizing to alter its physical properties for use in various applications.
Paper at this point is uncoated. Coated paper has a thin layer of material such as calcium carbonate or china clay applied to one or both sides in order to create a surface more suitable for high-resolution halftone screens. (Uncoated papers are rarely suitable for screens above 150 lpi.) Coated or uncoated papers may have their surfaces polished by calendering. Coated papers are divided into matte, semi-matte or silk, and gloss. Gloss papers give the highest optical density in the printed image.
The paper is then fed onto reels if it is to be used on web printing presses, or cut into sheets for other printing processes or other purposes. The fibres in the paper basically run in the machine direction. Sheets are usually cut "long-grain", i.e. with the grain parallel to the longer dimension of the sheet.
All paper produced by paper machines as the Fourdrinier machine are wove paper, i.e. the wire mesh that transports the web leaves a pattern that has the same density along the paper grain and across the grain. Textured finishes, watermarks and wire patterns imitating hand-made laid paper can be created by the use of appropriate rollers in the later stages of the machine.
Wove paper does not exhibit "laidlines", which are small regular lines left behind on paper when it was handmade in a mould made from rows of metal wires or bamboo. Laidlines are very close together. They run perpendicular to the "chainlines", which are further apart. Handmade paper similarly exhibits "deckle edges", or rough and feathery borders.[4]
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Mon, 30 Aug 2010 09:08:32 GMT+00:00
On Tuesday IMarketnews.com beijing (MNI) - The People's Bank of China announced that it will sell CNY12 billion in one-year paper on Tuesday as part of its open market operations. ... China PBOC 1-Yr Yield Unchanged At 2.0929%; No Repos: Traders IMarketnews.com
Wed, 18 Jul 2007 17:16:11 PDT
A video of Blind Melon playing an acoustic version of the song "Paper Scratcher". myspace.com. youtube.com.
