The hottest paper is kept to control temperature a

2022-08-16
  • Detail

Editor's note: the paper or paperboard used for packaging and printing will often affect its performance due to improper storage. The following article introduces how to control temperature and humidity in different storage places to avoid paper deformation

paper is a material with strong hydrophilicity. The change of paper moisture content will cause paper deformation and embrittlement, resulting in inaccurate overprint of printed products, and fracture during paper forming and processing. The changes of ambient temperature and humidity are the main factors affecting the water content of paper. Paper not only absorbs moisture in the process of contact with paper, but also has the ability to absorb moisture from wet air,

and drain water into dry air. The paper expands after absorbing water, the linear size and area in all directions will increase, and the mechanical strength will decrease; The paper shrinks after dehydration, and the linear size and area in all directions will shrink, becoming stiff and brittle. Therefore, to control the change of paper performance, we must control the water content of the paper and the temperature and humidity of the environment in which the paper is located

in the whole printing production process, the paper is taken out from the warehouse, cut, printed, processed and shaped after printing, and transferred from one workshop to another. At this time, it is necessary to consider the possible changes in temperature and humidity due to the change of space, resulting in the change of paper performance

(1) warehouse

pay attention to the storage conditions of paper in storage, and control the temperature and humidity of the warehouse environment. If the paper is in high humidity, it will absorb the surrounding water and curl and deform, resulting in Ruffle edges; If the paper is stored in a very dry environment, it will lead to the loss of water in the paper, making the paper brittle, fragile, and tight edges. Therefore, the paper should be stored close to the use environment

(2) printing workshop

due to the difference of temperature and humidity in the surrounding environment, the paper should be subject to the humidification treatment of the leader of the production enterprise of the testing machine before being put into printing, especially the sheet fed paper. When unpacking a single sheet of paper, its moisture content cannot be the same as the temperature and humidity of the printing workshop. It is necessary to adjust the humidity to make the moisture content of the paper uniform and consistent with the temperature and humidity of the printing workshop

there are usually three methods to adjust the humidity of offset sheet fed paper:

① hang it in the printing workshop or the air drying room with similar temperature and humidity

② conduct humidity adjustment treatment in the paper drying room which is 6% - 8% higher than the relative humidity of the printing workshop

③ put the paper in a wet place to humidify, and then go to the printing workshop or the air drying room with good stability with the temperature and humidity of the printing workshop to balance the water content, so that the water content of the paper is uniform

comparing these three methods, the latter two methods have better results, but need some equipment and site. Due to the limitations of conditions, the first method, usually called natural wet adjustment, is mostly adopted by printing plants in China at present. If the paper is kept in an environment without temperature and humidity control, the paper should be sent to the printing workshop for humidity control at least 24 hours before printing, so that the moisture contained in the paper can adapt to the temperature and humidity of the printing workshop, so as to ensure the overprint accuracy and improve the print quality

in addition, the humidity control measures of web paper and sheet fed paper are different. The web paper is packaged in paper roll (such as kraft paper packaging), and its outer packaging can protect the moisture content of the inner web paper from the influence of external environmental humidity. The outer packaging can only be opened before being put on the machine

(3) the temperature and humidity control of the post press processing workshop is the control of the whole process of printing and packaging. Some printing houses only pay attention to the temperature and humidity control of the printing workshop, while ignoring the temperature and humidity control of the post press processing workshop. The printing workshop is equipped with corresponding air conditioners, humidifiers and other devices, which can ensure the stability of the printing workshop environment. The post press processing workshop should also adopt the same method to ensure the stability of the processing environment in order to make the paper products processing "all the way smoothly". Otherwise, when the printed matter enters the dry and cold post press processing workshop from the printing workshop with temperature and humidity control, the paper, cardboard and paperboard printed in front will have problems such as carton edge fracture and whitening during the forming process, resulting in great waste in production

when formulating a series of plans for enterprise procurement, warehouse management and production environment control, the printing factory should fully consider the impact of small links on the overall production and product quality. It should be overall and scientific. The management should realize that timely capture of more accurate information is the most important, create a good but bad production environment, and improve production quality

Copyright © 2011 JIN SHI