Papermaker s alum

Internal Sizing. The most widely used internal sizes are alkyl ketene dimers (AKD), alkenylsuccinic anhydrides (ASA), and rosin-based sizes that are used with papermaker s alum (aluminum sulfate with 14 waters of hydration), polyaluminum chloride (PAG), or polyaluminum siUcosulfate (PAS) (61). The rosin-based sizes are used under acidic conditions. Since the mid 1980 s there has been a steady conversion from acid to alkaline paper production, resulting in static to declining demand for the rosin-based sizing systems. Rosin is a complex mixture of compounds and consists primarily of monocarboxyhc acids with alkylated hydrophenan threne stmctures (62). A main constituent of wood rosin, gum rosin and taH-oil rosin is abietic acid. 

ALUMINUM SULFATE (FILTER ALUM, ALUM, OR PAPERMAKER S ALUM)... 

Coagulating and coating the fibers with aluminum sulfate, papermaker s alum. 

Aluminum sulfate [A12(S04)3, alum, filter alum, papermaker s alum] is manufactured from aluminum oxide (A1203, alumina, bauxite). A mixture of the crude ore and sulfuric acid is heated at 105 to 110°C for 15 to 20 hours. 

Synonyms Concentrated alum, Papermaker s alum, Sulfate of alumina. 

Acidity. For many years the pH of the paper has been considered an important characteristic affecting peramnence. Permanency specifications exist which call for paper with a pH of 6.5 or higher. Other specifications say that the pH should not be lower than 5.5. There is no disagreement, however, about the poor permanency of paper when it is under pH 5.5 (4). In this context, paper pH is determined by the extraction procedure already described. The acidity that is present in the paper will promote acid hydrolysis of the glucosidic bonds of cellulose. To prevent this type of degradation and to produce paper with a high extract pH, the paper machine process water system must be controlled at a neutral to alkaline pH with a minimum of total acidity, preferably with an excess of alkalinity. The term total acidity is used to describe the concentration of all dissolved ions and particles in the process water that contribute to acidity in the system and a low extract pH in the paper. For example, papermaker s alum dissociates to alumi-... 

Papermaker s alum is sometimes used for pitch control as alum functions by fixing the colloidal pitch particles onto the fibres, removing these from the system. The conditions (acid pH, etc.) by which this method can be utilised are the same as those required for rosin sizing. 

Barium sulphate is also becoming a rather common scale, particularly in closed pulp mills. When it occurs, the problem of its formation is exbemely troublesome as it is a salt with very low solubility. Because barium sulphate is a salt of such low solubility, barium sulphate scale may form even if barium concenbation, relative to other cations, is low, particularly when concentration in the system of sulphate ions is high. Barium is dissolved from the wood in the digester. The sulphate ion comes into the system through additives such as alum, and high sulphate ion concenbation may develop as a result of accumulation of the sulphate ion from papermaker s alum (used in the rosin sizing process) or from sulphuric acid used for pH conbol. A particular problem is Barium sulphate deposition in the headbox of Kraft liner machines. 

The most critical chemical in rosin sizing is the source of aluminium ions to react with the rosin size, as unless the alnmininm species is contained in the product, as in type 3 of the cationic rosin sizes, there will be no sizing. It is possible to obtain sizing with other metal ions, but these are much less efficient, or more costly, than alnmininm. As previonsly stated, the two most commonly nsed chemicals for this pnrpose are alnmininm sulphate (papermaker s alum) and PAC. 

ClearValue 1100 t[Clearvalue] Papermaker s Alum [Delta http //www.deitachemicai.com], Unichem ALSUL [Universal Preserv-A-Chem http //WWW. upichem. com]... 

Alcan Aluminum Sulphate Sol n. Alcan Aluminum Sulphate Solid Aluminum sulfate AS-3050 Betz Entec 650P Clar+lon A410P ClearValue 1100 Papermaker s Alum Unichem ALSUL... 

Certain specifications are however a must—e.g., iron content shall not exceed 15 ppm in battery grade sulphuric acid insoluble matter shall not exceed 0.2 % in papermaker s alum. 

Batch Process for Manufacture of Papermaker s Alum (Iron Free)... 

Since the 1800 s, sizing has been achieved by the wet end addition of rosin. Rosin size is emulsified in water prior to addition to the wet end of the paper machine. The introduction of preemulsified sizes in the 1970 s greatly simplified the sizing process. The rosin size must be anchored to the fibers in order to be effective as a sizing agent. This is accomplished by reaction with aluminum in the form of papermaker s alum, Al2(S04)3. The pH of the wet end is important to this process as the chemical nature of the aluminum ion is a function of pH. At a pH of 4.0 to 5.5, aluminum is Al which can react with the rosin in the size. This aluminum rosinate is precipitated onto the fibers creating the water resistant barrier. The precise mechanism of this process has been debated for many years. 

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