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Extra resources for Developments in Tissue Chemicals and Chemical Treatments
These products can be further cross-linked with compounds such as epichlorohydrin to give higher molecular weight polycondensates. Polyamines produced from an amine such as dimethylamine and epichlorohydrin are covered on page 48. These polyamines are primarily used as fixatives, for charge neutralisation or deposit control, rather than as retention aids. They are, however, also used to promote the performance of retention aids. Polyamidoamines Products for use in the paper industry can be obtained by condensing adipic acid and diethylenetriamine at high temperature and reacting with an excess of epichlorohydrin.
Typically, FWAs are supplied as 20% solutions, but suspensions and powders are also found in the market. The FWAs used in the paper industry are mostly derivatives of 4,4’-diaminostilbene2,2’-disulphonic acid, and three main types are used. When they are used in tissue, disulphonated or tetrasulphonated products are added into the paper-making furnish. Increasingly FWAs are supplied without additives such as urea, and stable products can then be produced only if they are ultra-filtered. The main FBAs used in paper-making are summarised below.
For packaging papers and many board products, removal of the printing inks is not necessary. The printing inks remaining in the paper cause a greyish-brown colouration, which precludes its use for higher-grade products. This is not the case for tissue paper, where chemical de-inking and ash removal are essential. Chemical de-inking In the washing process, surfactants are used to aid the detachment of ink and contaminant particles from the fibres and keep them in suspension, preventing re-deposition.