Process for the de-inking of printed waste paper

In a washing process for de-inking printed waste paper comprising pulping a printed waste paper as an aqueous alkaline suspension in the presence of a de-inking composition and washing the pulped paper with water, thereby obtaining a thickened suspension of paper in water separate from the washing waters which consist of another more dilute suspension containing ink, fillers, and a small amount of residual paper fibers, the improvement comprising

• (1) using as said de-inking composition, a de-inking composition consisting essentially of:
• (A) a salt of a fatty acid of the formula:
• R--COO--M wherein R represents one or more hydrocarbon chains selected from the class consisting of saturated and/or unsaturated hydrocarbons;
• and M represents a metal selected from the class consisting of Na and K;
• said fatty acid salt being present in an amount between 5% and 32% with respect to the weight of the entire composition;
• (B) a nonionic ethoxylated and/or propoxylated surfactant of the formula:
• ##STR14## wherein:
• Y is either H or CH.sub.3 ;
• R.sup.1 O represents the hydrophobic moiety of the molecule and is derived from a compound selected from the class consisting of alkylphenols of formula ##STR15## saturated primary fatty alcohols of formula R"--CH.sub.2 OH;
• saturated secondary fatty alcohols of formula ##STR16## fatty acids of the formula R.sup.v --COOH;
• and mixtures thereof, wherein R', R", R"', R.sup.iv and R.sup.v are alkyl chains;
• and
• n is a number between 2 and 40;
• said nonionic surfactant being present in an amount between 5% and 25% by weight of the entire composition;
• (c) an anionic surfactant selected from the class consisting of sulphonates of the formula R.sup.2 --SO.sub.3 --M';
• sulphates of formula R.sup.3 --O--SO.sub.3 --M';
• and mixtures thereof, wherein:
• R.sup.2 is selected from the class consisting of linear paraffin chains, olefin chains, and alkylaryl chains;
• R.sup.3 is a paraffin chain;
• and
• M' is selected from the class consisting of Na, K, NH.sub.4 and mono-, di- and tri-substituted alkylamines;
• said anionic surfactant being present in an amount between 2% and 8% with respect to the weight of the entire composition;
• (D) a sodium-carboxylmethyl-cellulose in an amount between 1% and 5% with respect to the weight of the entire composition;
• and
• (E) an alkaline inorganic salt selected from the class consisting of metasilicate, disilicate, carbonate, borate and polyphosphates, said alkaline inorganic salt being present in an amount between 30% and 80% of the entire composition;
• the percentages of the components (A), (B), (C), (D), and (E) totaling essentially 100%, said composition being present in an amount of about 1 to about 6% by weight with respect to said paper and the pH during the pulping being from about 9 to about 12;
• (2) injecting air or another inert gas in a flotation unit, into the other more dilute suspension coming from the washing operations, to cause a flotation in an alkaline medium at a pH of about 9, without the addition of floculants resulting in the formation of two phases, the upper-most phase containing ink;
• (3) skimming said upper-most phase;
• and
• (4) at least partially recycling the lower-most phase comprising de-inked clarified water, residual paper fibers, and fillers in diluted form to the pulping and washing operations.