Printing Paper and Printing Quality - Common Paper Diseases (1)

Paper defects that are not included in the paper quality technical requirements can be referred to as paper diseases. Paper sickness includes not only invisible, but only certain performance defects known through experiment or printing, such as brittle, print-through, lint-free, powder-fat, etc., as well as those that are directly visible or felt. Various defects and defects on the surface of the paper, such as dust, dirt, etc. Here the latter is called paper appearance disease.

The appearance of paper is a lot of diseases, including dust, spots, net marks, wool marks, "cloud flowers", seersuckers, wrinkles, creases, dirty spots, turf, clear spots, temperature spots, holes, embossing, scars, pulp, Hard blocks, uneven quantification, poor uniformity, etc. Some of these appearances of paper diseases are caused by paper materials before papermaking, some are caused by poor technical operation or poor technology in the papermaking process, and others are due to poor environmental hygiene in the factory. Once it appears, it is relatively continuous, such as felt marks and “cloud flowers”. Once it appears, it always exists if no measures are taken; some appearance paper diseases have some kind of chance or occur only once after a long time, such as dirty spots. , holes and so on. The presence of some paper diseases will deteriorate the quality of the paper, such as dust, felt, etc. Some paper diseases will make the paper waste, such as offset printing paper with hard blocks or copper plates with large dirty spots. Paper can only be disposed of as waste.

According to different types of common paper diseases can be divided into:

※ fluctuations in paper ration and uneven web quantification

The first kind of fluctuation is generally caused by periodic vibration of the feed system of the paper feed headbox, vibration of the rotor screen in front of the headbox or vibration of the pulp pump, and sometimes due to the uniformity of the headbox. The squeegee is bent or the hole is unreasonable.

The second kind of fluctuation is generally caused by reasons such as unreasonable production process or improper operation management.

※ Poor formation. The phenomenon is:

1) Tufty structure: refers to the state where the fibers are mixed together into a mass.

2) "Cloud Flower": Also called cloud organization, it means that the fibers in the paper are distributed like clouds on the paper sheet.

3) Fibrous tissue disjoint: refers to poor fiber interweaving in the running direction of the paper machine.

4) Wave-like fibrous tissue: It refers to a wavy thickening layer that curves along the width of the paper.

5) Puddle: Refers to some of the visible longitudinal strip marks on the web.

※ Dust, spots, sand and hard blocks

1) Dust: It can be classified into three types: "fibrous dust," "non-metallic dust," and "metal dust."

2) Spots: Can be divided into "moist spots and vapor spots", "cylinder spots", "calender spots", "spots", "bubble spots", "filler spots and paint spots", "bright spots and white spots ".

3) Sand: Refers to the sand, lime residue, carbon residue and other hard mineral sand present on the surface of the paper.

4) Hard block: Refers to the occasional hard texture on the surface of the paper, block material or coarse material that is higher than the paper surface, such as knots, grass knots, pulp blocks, etc., which are the most dangerous to the printing.