Press drying

This method is a combination of pressing and drying. First the web is dewatered mechanically in a press nip and brought into tight contact with the hot surface on one side. At the opposite side the web is covered by a permeable belt such as a felt or a wire which continues to press the web to the hot surface over a longer distance. The vapour escapes through the permeable cover or is stored therein. There are only a few installations of this dryer type worldwide. 

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Processes. The most common method for the appHcation of chemicals to the surface of a paper web is by a size press. In the size press, dry paper, which usually is sized to prevent excess water and chemical penetration, is passed through a flooded nip or pond, and a solution or dispersion of the functional chemical contacts both sides of the paper. Excess Hquid is squeezed out in a press and the paper is redried. 

TSR 5. Within the Malaysian scheme SMR 5 is restricted to mbber derived from sheet material prepared by conventional processes, ie, ribbed smoked sheet (RSS), air-dried sheet (ADS), and unsmoked sheet (USS) and presented in small bale form. Other countries may source different raw materials, eg, Indonesia produces SIR 5 from thin latex coagulum (14). SMR 5 prepared by pressing dry-sheet material into standard bales must be identified by the type of sheet material, eg, SMR 5RSS, on the test certificate as well as on the wrapping. 

The 3-bromo-4-acetaminotoluene separates in crystalline flocks. It is filtered by suction and washed well with water and pressed dry. The wet crude material is dried until its weight does not exceed 500 g. before proceeding with the hydrolysis (Note 3). 

B. Extraction with Ether (Note 10).—The solid mixture is transferred to a 2-1. flask and shaken ten minutes with 750 cc. of ether. The ether solution is decanted through a suction filter and the solid thrown onto the filter and pressed dry. The solid is then returned to the flask and shaken with 400 cc. of ether, d his mixture is filtered by suction and the solid washed twice on the filter with 250 cc. portions of ether. Each portion is allowed to drain through the filter several times while the solid is kept... 

The residue of crystalline putrescine dihydrochloride is rinsed onto a Buchner funnel with the aid of 100-200 ml. of absolute ethanol used in several portions. The last portions of ethanol are used as wash liquid for the crystals. The crystals are finally pressed dry and washed with 25 ml. of ether. The air-dried product weighs 53-55 g. (72-74%) and melts above 275. Analysis for chlorine indicates that the salt is anhydrous. Concentration of the filtrate to a volume of about 25 ml. yields an additional 1-2 g. total yield 73-77%. The entire synthesis may be completed in one day. 

The reaction mixture was then allowed to cool to room temperature, washed with water, and extracted with four 165 ml portions of 2 N hydrochloric acid. The aqueous extracts were combined and stirred at room temperature to permit crystallization of the hydrochloride salt of the desired product. Crystallization was completed by cooling the slurry in an ice bath, and the product was collected by filtration, pressed dry, and recrystallized from 750 ml of water. Yield of pure crystalline material, 323 grams. 

C. MEDINA. The crude methylenedi(nitro-formamide) is pressed dry on the filter, stirred into lOSml of formic acid, and the paste allowed to stand overnight. The next day the soln is filtered thru an acid-proof flit, the formic acid and w removed by codistn with xylene, and the crude MEDINA, which seps as a sand, filtered and dried over paraffin and NaOH in a vacuum yield 80—100% based on methylene diform-amide, mp 98—103°. The crude MEDINA is recrystd from 2-nitropropane or et chloride iso-Pr ale 9 1, mp 104-059 (Ref 11, p 54). This prepn is also covered in Ref 20... 

The flask is then cooled in ice water, and the contents are filtered with as little suction as possible (Note 3). The filter cake is pressed dry and washed with three 15-ml. portions of tetrachloroethane first used to rinse out the flask. The combined filtrates are dried with a little calcium chloride. Sometimes the solution contains a little bromine it is removed by adding allyl alcohol dropwise until the bromine color is discharged (usually 0.5-1.0 ml. suffices). 

The precipitate is collected on filter paper (Note 7) in a Buchner funnel by vacuum filtration and is washed with 100 ml. of absolute ethanol. The solid is slurried in three 75-ml. portions of distilled water (Note 8), 100 ml. of absolute ethanol, two 100-ml. portions of reagent-grade acetone, and two 100-ml. portions of anhydrous ethyl ether. The filter cake is pressed dry in the funnel with suction by means of a piece of rubber dam, transferred to a tared, 500-ml., round-bottomed flask, and dried under reduced pressure (0.01 mm.) at room temperature for 24 hours (Note 9). The weight of the dry silver salt of succinimide is 51-54 g. (88-94%). 

In the production of wet process hardboards and serai-hardboards the press-dried boards are usually tempered or "cured" in hot air to increase their water resistance, dimensional stability, strenght and stiffness. A curing for 5 hours or more in hot air of 165°C is common. Higher curing temperatures reduce the period needed for each batch and thus increase the capacity of the heat treatment chamber, but they increase the auto-ignition risks. 

In a 600-ml. beaker equipped with a stirrer, thermometer, and dropping funnel are placed 24.6 g. (0.1 mole) of finely powdered l,2-di-l-(l-cyano)-cyclohexylhydrazine (p. 50) and 130 ml. of 90% ethanol. To this mixture is added slowly, with cooling, 45 ml. of concentrated hydrochloric acid. The beaker is placed in an ice bath, and, after the suspension has been cooled to 10°, bromine is added at such a rate that the temperature does not rise above 15°. About 16-17 g. (about 0.1 mole) of bromine is required to reach the end point characterized by a permanent orange-yellow color. The reaction mixture is poured into 80 ml. of ice water. After 15 minutes the suspension is filtered with the aid of a Buchner funnel, washed with 250 ml. of water, and pressed dry. The solid is transferred to a 500-ml. Erlcnmeyer flask, 120 ml. of boiling 95% ethanol is added, and the crude... 

In a 600-ml. screw-capped bottle are placed 15.4 g. (0.314 mole) of sodium cyanide, 20.5 g. (0.158 mole) of hydrazine sulfate (Note 1), and 400 ml. of ice water. The bottle is capped to prevent loss of hydrogen cyanide (Note 2) and held in an ice bath for 15 minutes. To the cooled mixture is added 29.4 g. (0.3 mole) of cyclohexanone. The bottle is recapped and cooled for an additional 15 minutes. The bottle is then shaken intermittently over a period of 6 hours and allowed to stand an additional 14 hours. The bottle is cooled again before opening. The suspension is filtered by means of suction, and the cake is washed thoroughly with 250 ml. of ice water. After the crude product has been pressed dry on the filter (Note 3), it is transferred to a... 

The solid product is next treated for 15 min with 300 ml of a 10% aqueous sodium carbonate solution at 40°C, filtered, washed with water, refiltered, and pressed dry. The solid is then dissolved in warm ethanol. The solution is treated with decolorizing carbon and filtered. On cooling, the product crystallizes out yield 3.9 gm (53%), m.p. 192°-193°C. 

In an apparatus set up for steam distillation and containing a rapidly stirred solution of 5.0 gm (0.023 mole) of jV-benzoylphenylhydroxylamine (N-phenylbenzohydroxamic acid) in 100 ml of a 1 1 solution of ethanol-acetic acid, cooled to —20°C, is added 11.5 gm (0.024 mole based on 94% purity) of lead tetraacetate in one portion. After approximately 10 sec (when the initial green color just begins to darken), 100 ml of water is added and the brown or black mixture is rapidly subjected to steam distillation. The distillate is collected in a receiver filled with chopped ice. The product is isolated by filtration of the distillate. Finally, it is dried by pressing dry between filter papers to yield 1.4-2.0 gm (56-80%), m.p. 66°-68°C. 

A solution of sodium iodate, prepared from lOg of iodine according to (I), is diluted to 120ml with water and 4g of sodium hydroxide are added. Twenty-two grams of potassium persulfate are used as m (II) and then a second portion of 17g sodium hydroxide is added. The mixture is boiled for 15 minutes longer, then cooled to 40° C, and the liquid is decanted. The solid is broix it on to the filter with about 25ml of ice water, pressed dry, and then heated at 110°C for one or two hours. 

The French and J apanese used compressed PA. The Russians, as late as WWI, used pressed dry Guncotton as boosters in warheads of some torpedoes with wet guncotton as bursting chge and pressed TNT for... 

The pulp recovered during screening may be transferred to a pulp-wash operation to yield further soluble solids by counter-current extraction with water. The washed pulp may be held for further processing or included with the bulk of ejected peel material from the extractors. This is milled, treated with lime (calcium hydroxide or calcium oxide) to break down pectin and reduce water retention, pressed, dried to c.10-12% moisture content and finally converted to pellets. Being high in carbohydrates these are used as filler in livestock feed blends. 

The white, finely divided precipitate of nitrourea is filtered upon a 12-cm. Buchner funnel. A hardened filter paper (Note 2) is used in this operation and the nitrourea is pressed as dry as possible. The product is washed in the funnel with four portions of cold water just sufficient to covfer it and pressed dry each time (Note 3). Then it is dried in the air (Note 4). By strongly cooling the filtrates, a further small amount of nitrourea may be obtained and added to the main portion. The yield of air-dried material is 120-150 g. (70-87 per cent of the theoretical amount). It melts with decomposition at 150-164° and is sufficiently pure for use in the preparation of semicarbazide (Note 5). 

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