Causes and solutions of pinhole whitening in the h

Reasons and solutions for pinhole whitening in full page printing

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core tip: Introduction: notebook computers and LCD packaging products made of high gram weight and high break resistant Kraft linerboard, full page black printing is prone to pinhole whitening, why is there

introduction: high gram weight High wear-resistant Kraft linerboard is used to realize the large-scale production of complex plastic parts of batteries. Paper processing and manufacturing the notebook computer and LCD packaging box products mentioned by Lu Hao. The pinholes are easy to show white when printed in full black. Why is there poor printing

1. Cause analysis of poor printing

at present, when domestic paper mills produce high gram weight (200~300g/m2) and high breaking natural color kraft liner base paper, it is generally formed in triplicate, in which the surface layer is made of unbleached kraft wood pulp plus some aesthetic waste, and the core bottom two layers are made of 100% aesthetic waste. The printability of its surface is affected by the following factors:

a, surface sizing

base paper in order to improve its burst resistance and moisture resistance, surface sizing process is currently used, and most of it is immersion sizing. At present, environmental friendly water-based flexographic printing is mostly used in corrugated boxes, which is very sensitive to the surface sizing process requirements of base paper

poor sizing will cause large water absorption on the surface, easy to return to moisture during storage and transportation after packaging, and the compressive strength of the carton will be reduced, resulting in carton collapse. If the sizing is too good, the moisture-proof performance of the carton is good, but it will affect the ink absorption performance in the production process of the carton and the printing effect, especially the full plate field and dot printing

b, waste cardboard as raw materials accounts for a large proportion

due to the growing concern about environmental protection, people are now encouraging the use of recyclable and recyclable materials. All wood pulp packaging base paper is rarely used in the world. Under the premise of relatively poor forest resources in China, the production of high-strength box board base paper uses waste box board paper as raw materials

due to the large amount of stickies and other impurities in the waste box board paper, it is difficult to clean the non fiber substances in the paddle material in the process of papermaking, considering the factors of fiber retention and system processing capacity. It is precisely because of these viscous substances and dust attached to the surface fibers of the base paper that directly leads to the whitening phenomenon in the process of water-based full page printing

2. Five improvement measures

for the typical pinhole whitening phenomenon in full page printing, we generally consider the 2016 semi annual report from the aspects of human, machine, material, method and environment

(1) replace the ink and use higher grade ink, because the particles of high-grade ink paste are finer and more evenly distributed in the solvent

(2) appropriately increase the ink amount

(3) adjust the pH value of ink and add more information about chemistry: Shandong Sida high tech mechanical equipment Co., Ltd. main products: friction and wear testing machine electronic/hydraulic universal testing machine/tensile testing machine/fatigue testing machine/change the additives of testing machine

(4) special treatment of paperboard surface

(5) optimize the process of base paper cladding

3. Suggestions: try to use less large-area full-scale field printing

in addition, in terms of packaging design, we should also pay attention to the following adverse effects of full-scale black field design:

a, it is not conducive to environmental protection and increases the difficulty of packaging recycling. Because of the recycling of waste cardboard, the biggest use function is to manufacture base paper. After large-area black printing, the waste box board paper will consume a lot of energy and affect the production efficiency in the process of beating, desanding and thermal dispersion as the raw material of base paper again. In addition, the cost of wastewater treatment generated in the papermaking process will also increase, which is not conducive to energy conservation, emission reduction and energy consumption reduction

b, waste of resources

full page printing will consume a lot of water and ink in the production process of cartons, and produce defects such as printing displacement, white exposure, blurred handwriting, color difference and so on, which will increase the defect rate in the production process of cartons. In order to reduce the defect rate, the carton factory will spend a lot of manpower and material resources as temporary remedial measures. For example, the poor cartons exposed by printing should be manually traced by workers

c, rising packaging costs

after large-area full page printing, due to the relief water-based printing pressure, the cardboard corrugates and deforms, the thickness decreases, the edge pressure of the cardboard decreases, and the compressive strength of the empty box decreases after being packed, increasing the risk of box collapse and package damage in the logistics process. Therefore, the safety factor of cartons must be considered in the strength design, and the weight and grade of cartons must be increased, which will also lead to the increase of packaging costs

based on the above reasons, it is suggested that on the premise of not affecting product sales, the design should get out of the misunderstanding, and on the premise of not affecting the packaging and display function, try to use less large-area full page field printing