Adding Some Color to Your Wastepaper Furnish, 1992 Pulping Conference Proceedings

Two issues of interest to recycled fiber producers are firstly, the elimination of hypochlorite, which traditionally has been used as an effective bleaching and color stripping agent, and secondly, the desire to make use of the lowest grade wastepaper as is practicable as raw material (such as post-consumer colored ledger) for producing the highest grade recycled product. With the introduction of FAS into commercial applications in North America, the above two issues can be satisfactorily resolved.

Data are presented which show FAS to be an effective replacement for bleaching a variety of types of colored stock. As well, various applications of FAS are described.

A series of raw material stocks were prepared by mixing unprinted virgin white ledger with 10%, 30%, 50% and 70% of a mixture of 5 unprinted colored papers, and each stock was treated with bleaching chemical. With the capability of bleaching with either FAS or hydrosulfite, substantial cost savings can be realized by introducing a less expensive colored wastepaper into the starting furnish. An 80% IS0 brightness can be economically achieved using up to about 30% color content. A treatment with peroxide, followed by reductive bleaching allows for up to about 70% colored paper content to produce an 80% IS0 brightness.

Data are also shown demonstrating the economic benefit of bleaching colored paper separately prior to blending it with white paper.