Ink summer effect of waste newspaper deinking process

1. Ink summer effect

The fundamental reason for the summer effect of ink is that some changes in ink are caused after the temperature rises. Printing inks are mainly composed of pigments and binders, in addition, there are some fillers and additional materials. The black ink used for newsprint printing usually uses mineral oil as a binder, and the colored ink usually uses vegetable oil as a binder.

After the black ink is printed on the paper, the binder (mineral oil) in the ink is initially on the surface of the paper, but after a period of aging (4-6 months), the mineral oil is almost completely absorbed by the paper due to its The ability to absorb oxygen is poor. The binding material left on the paper is rarely cross-linked, and there is no stiff structure, only some fragile and fragile structures, so many small ink particles are formed.

After the vegetable oil ink is printed on the paper, the binder (vegetable oil) in the ink is also on the surface of the paper at the beginning, but due to its strong ability to absorb oxygen, after a period of aging, part of the vegetable oil is absorbed by the paper, but there are still Many remain on the paper surface and stick together with the pigment. Because vegetable oils have an unsaturated double-chain structure, they can form some cross-linked stiff structures and attach to fibers.

When old newspapers printed with mineral oil ink and vegetable oil ink are crushed in a disintegrating machine, mineral oil ink is easier to crush than vegetable oil ink, so the ERIC value after crushing is high (effective residual ink particle concentration) and after sufficient washing, The concentration of irreversible redeposited ink particles in the pulp is also greater, which has a greater impact on the whiteness of waste paper pulp.

2. Ink summer effect on whiteness

The whiteness of Canadian deinked pulp is the lowest from June to August every year. The whiteness of the deinked pulp in the northern United States is the lowest from July to August every year, which is about 1.4% lower than normal. The whiteness of waste paper desizing in our factory is also the lowest from July to August every year. For example, the minimum whiteness pass rate in 1998 was 46.2%, the minimum whiteness pass rate in 1999 was 71.2%, the minimum whiteness pass rate in 2000 was 2.6%, and the minimum whiteness pass rate in 2001 was 11.3%. This shows that no matter which country or region, the summer effect of ink deinking of waste paper is widespread.

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