Optical Brighteners in Fine Papers, 1999 Papermakers Conference Proceedings

Thomas Roick

There are a number of substances of different chemical composition and different biological origin which can be used for the fluorescent whitening of paper. Derivatives of diaminostilbene disulphonic acid have proved the most popular in industry because of their fastness properties. In most cases, liquid formulations containing carrier substances are used. The active ingredient content of these formulations is generally between 20 % and 27 %. Figure 1 shows the structure of the different types of fluorescent whitening agent (FWA) used in the paper industry. The central part consists of the disulphonated diaminostilbene. The various types differ in the number of sulphonic acid groups in the side groups. The high-substantivity types with only 2 sulpho groups make up about 11 % of the market. Tetrasulphonated derivatives with medium substantivity account for about 80 % of the market, making them the workhorse of this product group. The rest is made up of low-substantivity, hexasulphonated types. In terms of volume, FWAs represent only a very small percentage of the processing chemicals used in paper production (Figure 2). FWAs make up about two thirds of the group "Dyestuffs and FWAs".