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49-509: Born in Edinburgh, Scotland in 1839, he emigrated to the United States at age 14. Gair invented the paperboard folding carton by accident when a metal ruler used to crease bags shifted position and cut the bag. Gair found that by cutting and creasing paperboard in one operation, he could make prefabricated cartons. He ultimately entered the corrugated fiberboard shipping container business in

98-495: A reducing agent like sulfur dioxide : Chlorine dioxide is sometimes used in combination with chlorine, but it is used alone in ECF (elemental-chlorine-free) bleaching sequences. It is used at moderately acidic pH (3.5 to 6). The use of chlorine dioxide minimizes the amount of organochlorine compounds produced. Chlorine dioxide (ECF technology) currently is the most important bleaching method worldwide. About 95% of all bleached kraft pulp

147-444: A complex mixture of small oxygenated molecules. Transition-metal compounds, particularly those of iron , manganese and copper , which have multiple oxidation states, facilitate many radical reactions and impact oxygen delignification. While the radical reactions are largely responsible for delignification, they are detrimental to cellulose. Oxygen-based radicals, especially hydroxyl radicals , HO•, can oxidize hydroxyl groups in

196-452: A final treatment with hypochlorite. An example of a modern totally chlorine-free (TCF) sequence is OZEPY , where the pulp would be treated with oxygen, then ozone, washed with sodium hydroxide, then treated in sequence with alkaline peroxide and sodium dithionite. Chlorine replaces hydrogen on the aromatic rings of lignin via aromatic substitution , oxidizes pendant groups to carboxylic acids and adds across carbon carbon double bonds in

245-453: A market share of 85%. Bleaching of wood pulp Bleaching of wood pulp is the chemical processing of wood pulp to lighten its color and whiten the pulp. The primary product of wood pulp is paper , for which whiteness (similar to, but distinct from brightness) is an important characteristic. These processes and chemistry are also applicable to the bleaching of non-wood pulps, such as those made from bamboo or kenaf . Brightness

294-462: A persistent environmental pollutant, regulated internationally by the Stockholm Convention on Persistent Organic Pollutants . Dioxins are highly toxic, and health effects on humans include reproductive, developmental, immune and hormonal problems. They are known to be carcinogenic . Over 90% of human exposure is through food, primarily meat, dairy, fish and shellfish, as dioxins accumulate in

343-604: A result of layering different types of pulp into a single product. In cases where the same kind of pulp is being used in several layers, each separate layer is treated and shaped individually in order to create the highest possible quality. In order to improve whiteness, smoothness and gloss of paperboard, one or more layers of coating is applied. Coated paper is usually made up of: Additional components could be OBA ( optical brightening agents ). The DIN Standard 19303 "Paperboard - Terms and grades" (Publication date : 2005-09) defines different grades of paperboard based on

392-430: A sheet of paperboard with a thickness of 0.024” would be 24 points. In Europe it is often sold in g/m , however the thickness of the board is measured in micron (μm). Paperboard also tends to be referred to with thickness rather than weight. Whiteness: It refers ideally to the equal presence of all colours, because a truly white sheet will reflect all wavelengths of visible light equally. The paperboard sector

441-428: Is a technical term that is defined as the amount of blue-white light that a paper reflects. This property is very subjective and individual to each buyer and end use, as skin colour and food are better reproduced on 'warm' (yellow) whites and not blue whites. Grammage: The grammage of the paperboard is assessed in accordance ISO 536. Grammage expresses mass per unit area and is measured in g/m . PH: Surface pH

490-464: Is a thick paper -based material. While there is no rigid differentiation between paper and paperboard, paperboard is generally thicker (usually over 0.30 mm, 0.012 in, or 12 points ) than paper and has certain superior attributes such as foldability and rigidity. According to ISO standards, paperboard is a paper with a grammage above 250 g/m , but there are exceptions. Paperboard can be single- or multi-ply. Paperboard can be easily cut and formed,

539-400: Is frequently composed of four or more discrete steps, with each step designated by a letter: A bleaching sequence from the 1950s could look like CEHEH  – the pulp would have been exposed to chlorine, extracted (washed) with a sodium hydroxide solution to remove lignin fragmented by the chlorination, treated with sodium hypochlorite, washed with sodium hydroxide again and given

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588-467: Is less than that used in bleaching chemical pulps and the temperatures are lower. These conditions allow alkaline peroxide to selectively oxidize non-aromatic conjugated groups responsible for absorbing visible light. The decomposition of hydrogen peroxide is catalyzed by transition metals , and iron , manganese and copper are of particular importance in pulp bleaching. The use of chelating agents like EDTA to remove some of these metal ions from

637-503: Is lightweight, and because it is strong, is used in packaging . Another end-use is high quality graphic printing, such as book and magazine covers or postcards. Paperboard is also used in fine arts for creating sculptures. Sometimes it is referred to as cardboard , which is a generic, lay term used to refer to any heavy paper pulp –based board, however this usage is deprecated in the paper, printing, and packaging industries as it does not adequately describe each product type. In 1817,

686-601: Is made using chlorine dioxide in ECF bleaching sequences. All bleaching agents used to delignify chemical pulp, with the exception of sodium dithionite, break lignin down into smaller, oxygen-containing molecules. These breakdown products are generally soluble in water, especially if the pH is greater than 7 (many of the products are carboxylic acids ). These materials must be removed between bleaching stages to avoid excessive use of bleaching chemicals, since many of these smaller molecules are still susceptible to oxidation. The need to minimize water use in modern pulp mills has driven

735-716: Is mainly looked at in conjunction with the paper industry. The Paper & Paperboard market size (2007) had a value of US$ 630.9 billion and a volume of 320.3 million metric tons. Of that market 40.1% is European. About 50% of all produced paper is used for packaging, followed by printing and writing. According to ProCarton, the consumption of paper and paperboard seem to correlate with economic trends (GDP). Sales of carton in Europe sum up to around 8 billion Euros worth. Over 1,100 printers produce 5.4 million tonnes of cartonboard yearly. Cartons make up one third of paper and board packaging and 15% of all packaging. A bit more than half (54%) of

784-556: Is measured on a water extract and is on a scale of 0–14. 0 is acidic , 7 is neutral and 14 is alkaline . Stiffness: Stiffness is one of the most important properties of paperboard as it affects the ability of cartons to run smoothly through the machine that erects, fills and closes them. Stiffness also gives strength and reduces the propensity of a carton to bulge under the weight of settling flowable contents such as cereals. Although most paper strength properties increase with increasing sheet density, stiffness does not. A rule of thumb

833-419: Is not necessary for all end-uses, it is vital for many graphical and packaging purposes. There are various methods of bleaching , which are used according to a number of factors for example, the degree of colour change required, chemicals chosen and method of treatment. There are three categories of bleaching methods : Multi-ply paperboard generally has higher creasing and folding performance than single-ply as

882-535: Is now mandatory in many countries for paper-based packaging to be manufactured wholly or partially from recycled material. Raw materials include: Two principal methods for extracting fibres from their sources are: Pulp used in the manufacture of paperboard can be bleached to decrease colour and increase purity. Virgin fibre pulp is naturally brown in colour, because of the presence of lignin . Recycled paperboard may contain traces of inks , bonding agents and other residue which colors it grey. Although bleaching

931-410: Is often referred to as delignification. Sodium hypochlorite (household bleach ) was initially used to bleach chemical pulps, but was largely replaced in the 1930s by chlorine . Concerns about the release of organochlorine compounds into the environment prompted the development of elemental chlorine free (ECF) and totally chlorine free (TCF) bleaching processes. Delignification of chemical pulps

980-530: Is produced on pulping machines that can handle higher grammage and several plies. The above-mentioned fibrous material can either come from fresh (virgin) sources (e.g. wood) or from recycled waste paper . Around 90% of virgin paper is made from wood pulp. Today paperboard packaging in general, and especially products from certified sustainable sources, are receiving new attention, as manufacturers dealing with environmental, health, and regulatory issues look to renewable resources to meet increasing demand. It

1029-416: Is seen as an adjunct to chlorine dioxide in bleaching sequences not using any elemental chlorine (elemental-chlorine-free, ECF). Over 25 pulp mills worldwide have installed equipment to generate and use ozone. The effect of transition metals such as Mn on some of the bleaching stages has already been mentioned. Sometimes it is beneficial to remove some of these redox-active metal ions from the pulp by washing

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1078-402: Is that stiffness is proportional to the 1.6 power of sheet caliper. The species of fiber used has an effect on stiffness, other things being equal. Northern softwood species impart superior stiffness compared to southern softwoods. Other factors which affect board stiffness include coatings and moisture content. Smoothness: Smoothness is particularly important when being used for printing,

1127-521: Is the amount of incident light reflected from paper under specified conditions, usually reported as the percentage of light reflected, so a higher number means a brighter or whiter paper. In the US, the TAPPI T ;452 or T 525 standards are used. The international community uses ISO standards. The table shows how the two systems rate high-brightness papers, but there is no simple way to convert between

1176-405: Is very similar to that involved in oxygen delignification, in terms of the radical species involved and the products produced. Hydrogen peroxide is sometimes used with oxygen in the same bleaching stage, and this give the letter designation Op in bleaching sequences. Redox-active metal ions, particularly manganese , Mn(II/IV), catalyze the decomposition of hydrogen peroxide, so some improvement in

1225-423: The food chain in the fatty tissue of animals. As a result, from the 1990s onwards, the use of elemental chlorine in the delignification process was substantially reduced and replaced with ECF (elemental chlorine free) and TCF (totally chlorine free) bleaching processes. In 2005, elemental chlorine was used in 19–20% of kraft pulp production globally, down from over 90% in 1990. 75% of kraft pulp used ECF, with

1274-399: The 1900s. His idea was developed and utilized by E. S. & A. Robinson with whom he had long-term business dealings. Gair founded a paper empire and occupied several buildings in the area of Brooklyn now known as DUMBO, many of which still bear his name. This article about an American inventor is a stub . You can help Misplaced Pages by expanding it . Paperboard Paperboard

1323-402: The 1970s and 1980s, as evidenced by the formation of organizations like Greenpeace , influenced the pulping industry and governments to address the release of these materials into the environment. Conventional bleaching using elemental chlorine produces and releases into the environment large amounts of chlorinated organic compounds , including chlorinated dioxins . Dioxins are recognized as

1372-454: The EU, the average chlorinated organic compound emissions for ECF plants is 0.15 kg per tonne. However, there has been disagreement about the comparative environmental effects of ECF and TCF bleaching. Some researchers found that there is no environmental difference between ECF and TCF, while others concluded that among ECF and TCF effluents before and after secondary treatment, TCF effluents are

1421-510: The European carton is produced using recovered fibre or waste paper. The paper and paperboard industry is quite energy and capital intensive. Just a coated board machine itself can cost around 90 - 120 million Euros (about 125 - US$ 166 million in 11/2011). Economies of scale apply, because of which a few large players often dominate the market place. E.g. in North America the top 5 producers have

1470-570: The beneficial metal ions, especially magnesium . A negative impact of chelating agents, as DTPA, is their toxicity for the activated sludges in the treatment of kraft pulping effluent. A variety of less common bleaching agents have been used on chemical pulps. They include peroxyacetic acid , peroxyformic acid , potassium peroxymonosulfate (oxone), dimethyldioxirane , which is generated in situ from acetone and potassium peroxymonosulfate, and peroxymonophosphoric acid . Enzymes like xylanase have been used in pulp bleaching to increase

1519-488: The big advantages of mechanical pulp is the high yield of pulp based on wood used. Therefore, the objective of bleaching mechanical pulp (also referred to as brightening) is to remove only the chromophores (color-causing groups). This is possible because the structures responsible for color are also more susceptible to oxidation or reduction . Alkaline hydrogen peroxide is the most commonly used bleaching agent for mechanical pulp. The amount of base such as sodium hydroxide

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1568-410: The brightness of deinked pulp . The bleaching methods are similar for mechanical pulp, in which the goal is to make the fibers brighter. Chemical pulps, such as those from the kraft process or sulfite pulping, contain much less lignin than mechanical pulps, (<5% compared to approximately 40%). The goal in bleaching chemical pulps is to remove essentially all of the residual lignin, hence the process

1617-554: The cellulose chains to ketones , and under the strongly basic conditions used in oxygen delignification, these compounds undergo reverse aldol reactions , leading to cleavage of cellulose chains. Magnesium salts are added to oxygen delignification to help preserve the cellulose chains, but mechanism of this protection has not been confirmed. Using hydrogen peroxide to delignify chemical pulp requires more vigorous conditions than for brightening mechanical pulp. Both pH and temperature are higher when treating chemical pulp. The chemistry

1666-443: The complexes formed between iron and lignin. The brightness gains achieved in bleaching mechanical pulps are temporary, since almost all of the lignin present in the wood is still present in the pulp. Exposure to air and light can produce new chromophores from this residual lignin. This is why newspaper yellows as it ages. Yellowing also occurs due to the acidic sizing . Hydrogen peroxide and sodium dithionite are used to increase

1715-540: The development of equipment and techniques for the efficient use of available water. Oxygen exists as a ground-state triplet , which is relatively unreactive and needs free radicals or very electron-rich substrates such as deprotonated lignin phenolic groups. The production of these phenoxide groups requires that delignification with oxygen be carried out under very basic conditions (pH > 12). The reactions involved are primarily single-electron ( radical ) reactions. Oxygen opens rings and cleaves sidechains, giving

1764-640: The efficiency of other bleaching chemicals. It is believed that xylanase does this by cleaving lignin–xylan bonds to make lignin more accessible to other reagents. It is possible that other enzymes such as those used by fungi to degrade lignin may be useful in pulp bleaching. The bleaching of chemical pulps has the potential to cause significant environmental damage, primarily through the release of organic materials into waterways. Pulp mills are almost always located near large bodies of water because they require substantial quantities of water for their processes. An increased public awareness of environmental issues from

1813-557: The efficiency of peroxide bleaching can be achieved if the metal levels are controlled. Ozone is a very powerful oxidizing agent, and the biggest challenge in using it to bleach wood pulp is to get sufficient selectivity so that the desirable cellulose is not degraded. Ozone reacts with the carbon–carbon double bonds in lignin, including those within aromatic rings. In the 1990s ozone was touted as good reagent to allow pulp to be bleached without any chlorine-containing chemicals (totally chlorine-free, TCF). The emphasis has changed, and ozone

1862-516: The first paperboard carton was produced in England . Folding cartons first emerged around the 1860s and were shipped flat to save space, ready to be set up by customers when they were required. The mechanical die cutting and creasing of blanks was developed in 1879. In 1911 the first kraft sulphate mill was built in Florida . In 1915 the gable top milk carton was patented and in 1935 the first dairy plant

1911-514: The lignin sidechains. Chlorine also attacks cellulose , but this reaction occurs predominantly at pH = 7, where un-ionized hypochlorous acid , HClO, is the main chlorine species in solution. To avoid excessive cellulose degradation, chlorination is carried out at pH < 1.5. At pH > 8 the dominant species is hypochlorite, ClO , which is also useful for lignin removal. Sodium hypochlorite can be purchased or generated in situ by reacting chlorine with sodium hydroxide : The main objection to

1960-704: The pulp prior to adding peroxide allows the peroxide to be used more efficiently. Magnesium salts and sodium silicate are also added to improve bleaching with alkaline peroxide. Sodium dithionite (Na 2 S 2 O 4 ), also known as sodium hydrosulfite, is the other main reagent used to brighten mechanical pulps. In contrast to hydrogen peroxide, which oxidizes the chromophores, dithionite reduces these color-causing groups. Dithionite reacts with oxygen , so efficient use of dithionite requires that oxygen exposure be minimized during its use. Chelating agents can contribute to brightness gain by sequestering iron ions, for example, as EDTA complexes, which are less colored than

2009-623: The pulp with a chelating agent such as EDTA or DTPA . This is more common in TCF bleaching sequences for two reasons: the acidic chlorine or chlorine dioxide stages tend to remove metal ions (metal ions usually being more soluble at lower pH), and TCF stages rely more heavily on oxygen-based bleaching agents, which are more susceptible to the detrimental effects of these metal ions. Chelant washes are usually carried out at or near pH = 7. Lower-pH solutions are more effective at removing redox-active transition metals ( Mn , Fe , Cu ), but also remove most of

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2058-424: The pulp. Lignin is the main source of color in pulp due to the presence of a variety of chromophores naturally present in the wood or created in the pulp mill . Mechanical pulp retains most of the lignin present in the wood used to make the pulp and thus contain almost as much lignin as they do cellulose and hemicellulose. It would be impractical to remove this much lignin by bleaching, and undesirable since one of

2107-771: The remaining 5–6% using TCF. Most TCF pulp is produced in Sweden and Finland for sale in Germany, all markets with a high level of environmental awareness. In 1999, TCF pulp represented 25% of the European market. TCF bleaching, by removing chlorine from the process, reduces chlorinated organic compounds to background levels in pulp-mill effluent. ECF bleaching can substantially reduce but not fully eliminate chlorinated organic compounds, including dioxins, from effluent. While modern ECF plants can achieve chlorinated organic compounds (AOX) emissions of less than 0.05 kg per tonne of pulp produced, most do not achieve this level of emissions. Within

2156-404: The results are the same, the processes and fundamental chemistry involved in bleaching chemical pulps (like kraft or sulfite ) are very different from those involved in bleaching mechanical pulps (like stoneground, thermomechanical or chemo-thermomechanical). Chemical pulps contain very little lignin , while mechanical pulps contain most of the lignin that was present in the wood used to make

2205-465: The smoother the paperboard, the better the image quality, because of better ink coverage. Smoothness is measured using air leak methods – the greater the rate of air leakage, at a specific air pressure, from under a cylindrical knife placed on the surface, the rougher the surface. Caliper/thickness: In the United States caliper is usually expressed in thousandths of an inch (0.001”) or points, where

2254-471: The surface treatment (first letter), the main furnish (second letter) and the colour (non-D grade) or bulk (D grade only) (numbering). All except D grades: D grades only: Example: GC1 would be a "pigment coated", "virgin mechanical pulp" board with a "white reverse side". Often the used paperboard type would be FBB, which was coated on both sides. Basis weight (US): Is the weight in 1,000 square feet (93 m ) of paperboard. Brightness: Brightness

2303-514: The two systems because the test methods are so different. The ISO rating is higher and can be over 100. This is because contemporary white paper incorporates fluorescent whitening agents (FWA). Because the ISO standard only measures a narrow range of blue light, it is not directly comparable to human vision of whiteness or brightness. Newsprint ranges from 55 to 75 ISO brightness. Writing and printer paper would typically be as bright as 104 ISO. While

2352-409: The use of chlorine for bleaching pulp is the large amounts of soluble organochlorine compounds produced and released into the environment. Chlorine dioxide , ClO 2 is an unstable gas with moderate solubility in water. It is usually generated in an aqueous solution and used immediately because it decomposes and is explosive in higher concentrations. It is produced by reacting sodium chlorate with

2401-448: Was observed using them. Ovenable paperboard was introduced in 1974. Terminology and classifications of paperboard are not always uniform. Differences occur depending on specific industry, locale, and personal choice. In general, the following are often used: Fibrous material is turned into pulp and bleached to create one or more layers of board, which can be optionally coated for a better surface and/or improved appearance. Pulp board

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