Process for the manufacture of paper and board, with recycling of waste water

摘要

In a process for making paper or cardboard, colophony is dissolved in a solution of calcined soda and the solution clarified by boiling with a solution of sodium hydroxide to form a hot mixture A; sodium hydroxide solution is added to a boiling mixture of paraffin wax, stearin and colophony and the milky solution cooled to form a cooled mixture B; cooled mixture B is added to hot mixture A, and the resultant mixture cooled to give a mixture AB; starch is dissolved in the cold in a solution of sodium hydroxide to yield a clear solution C; solution C is added to mixture AB, and this mixture is added to cellulose pulp e.g. in the beater, in a conventional papermaking process; starch is suspended in water and sodium hydroxide in the cold to form a second starch solution D; solution D is added to mixture B and this mixture is added to the backwater from the papermaking process; the water is separated from fibrous and filler substances, these substances are recycled to the cellulose pulp, and clear water from the material-recovery plant is mixed with lime water to a pH of at least 6. The regenerated water may be stored in tanks and recycled to the production process, it may be used without addition of fresh water for processing cellulose pulp, and make-up water may be a 50/50 mixture of fresh water and regenerated water. The lime-water may contain milk. Pulp prepared with the regenerated water may be acidified with a mixture of lime-water, sulphuric acid and alum.