Papermaking alkaline

In 1945, cationic urea resins were introduced and quickly supplanted the anionic resins, since they could be used with any type of pulp (62). Although they have now become commodities, their use in the industry has been steadily declining as the shift towards neutral and alkaline papermaking continues. They are commonly made by the reaction of urea and formaldehyde with one or more polyethylene—polyamines. The stmcture of these resins is very compHcated and has not been deterrnined. Ammonia is evolved during the reaction, probably according to the following ... 

In a previous publication in this series (8), Hagemeyer set alkaline papermaking in the context of future demand for paper, and dealt briefly with some of the technical consequences. Since then, more mills have converted to the new method, and the aim of this chapter is to inform the reader in some detail about the reasons for changing to neutral/alkaline papermaking, some of the consequences for the production and properties of paper, and how the change impinges on... 

The repercussions of running neutral/alkaline on the total process are widespread and merit a separate article. Whilst in the present context it is not necessary to deal with the topic in detail, to understand the relationship of permanent paper to neutral/alkaline papermaking as a whole, the reader needs to have some appreciation of what it means to change to the new process. In particular, this understanding is very useful for effective communication between manufacturer and user. 

Alberts, A.M. TAPPI Seminar Notes, Alkaline Papermaking (1983) 35. 

Davison, R.W. Hlrwe, A.S. TAPPI Alkaline Papermaking Seminar Notes (1985) 7. 

Permanency of paper was not questioned seriously until only recently when modern paper showed signs of excessive deterioration. In a relatively short time the technology was developed and standards were set for modern paper with specific, predictable permanency properties. Today, permanent paper is readily available and is competitively priced. Moreover, the alkaline papermaking process that is required for the manufacture of permanent paper is proving to some manufacturers to be more efficient in terms of costs, corrosion of equipment, and pollution control. 

An acid papermaking environment is corrosive. In the same manner that acidity can affect the reasonable life expectancy of paper by breaking down the amorphous structure of cellulose, acidity can affect the reasonable life expectancy of the working parts of a paper machine by corroding the exposed metal surfaces. An alkaline papermaking environment is noncorrosive, extends life, and reduces maintenance costs. Paper machine systems get dirty, and dirt affects the quality of the paper. 

Paper machines must be shut down, flushed out, and cleaned routinely to continue to operate efficiently. An alkaline papermaking system is cleaner than an acid system so downtime for wash-ups are less. 

These factors mean that an alkaline papermaking process contributes to smoother running conditions. The result can be a significant increase in paper machine productivity and paper mill profitability. 

In conclusion to this section specifically devoted to alkaline papermaking, the statement must be reiterated that it is very unlikely that any single paper mill will realize all six benefits. The value of an alkaline system vs. an acid system depends on the particular set of papermaking conditions, grade structure, and market requirements which exist for each mill. 

Stuhrke, R. A., Alkaline Papermaking Pros Cons, Hercules, Inc., pre-... 

Alkaline papermaking provides several opportunities for conserving papermaking raw materials and thus should become more prevalent in the years ahead. Making the conversion from an acid to an alkaline system includes many problems, but they are solvable and the ultimate savings warrants the effort. The strength and optical properties are similar for paper made by either system, but the permanence properties of the alkaline sheet are substantially better. 

Traditionally papermaking is made at acid pH of about 4.5. Because of this the sizing of paper is carried out with resin acid salts in the presence of alum. Under these conditions, the resin acid anions complex with the aluminium cations and the complex formed is attracted to and deposited on the fibre surface. The purpose of sizing is to render the paper more resistant to water-based printer s ink. Today there is much interest in so-called alkaline sizing at about pH 7, which is preferred for specialist long-life papers. Here sizes such as alkyl ketene dimer replace alum. Alkaline papermaking has the further advantage that fillers such as calcium carbonate can be employed. 

However, the general trend is towards neutral and alkaline papermaking, so currently the predominance is with cationic rosin sizes for neutral and ASA/AKD sizes for alkaline. The difference in the three types can be described by ... 

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