Judgment and elimination measures of scraper line paper disease
key words: scraper coating; Scraper line; Paper disease
there are many factors that affect the service life of the coating scraper, such as scraper pressure, the abrasiveness of the coating, the surface roughness of the base paper and the speed of the coating locomotive. These factors make the coating scraper easy to be worn, resulting in the coating scraper line. The original text of "scraper line" is blade streak or coating streak. Some people in China call it scraper scratch or scratch. It is a paper disease that often occurs in the process of scraper coating.
1 scraper line characteristics and causes
scraper line problems often occur in the process of scraper coating. Some are short or intermittent scraper lines, some are long or continuous scraper lines, and some are so thin that it is difficult to find them in the process of coating or calendering
it is acceptable for users to have 1 ~ 3 fine intermittent scraper lines in a roll of paper. If there are more than 4 intermittent or continuous scraper lines, users will generally complain
the characteristics of scraper lines are very important. Intermittent small scraper lines are usually caused by paint dehydration, while long, deep or continuous scraper lines are often caused by the accumulation of some pollutants on the scraper
2 simple measures for the operator to deal with the scraper line
(1) notify the foreman of the existing problems in time
(2) check the solid content, pH, viscosity and temperature of the coating
(3) check the backflow and circulation of paint in the scraper beam, paint tank and other parts. The larger the backflow, the better
(4) check whether there are holes in the surface sizing part, water supply tank, coater and its bypass filters
(5) measure the content of 325 mesh sieve residue, usually the surface coating
(6) when the machine is shut down, thoroughly clean the paint tank, replace the scraper and check whether there are abnormal aggregates (such as fibrous substances) on the scraper. After cleaning, inject new paint
(7) check whether there are loose or semi loose fibers on the surface of the base paper.
(8) if there is still a continuous scraper line after thoroughly cleaning the coater and replacing the scraper, check whether the base paper is too absorbent, too wet, or there are fluffy substances on the surface. Check the 325 mesh residue of #1 cloth coating and compare it with the data when it is in good condition.
(9) check whether the coating preparation process is strictly based on the coating formula. If possible, check the water retention of the coating and compare it with the normal value. Check the proportion of coarse pigments (such as No. 2 soil, CaCO3, etc.) in the surface coating formula, and the proportion should be increased gradually with a small amount. An appropriate amount of coarse pigment can appropriately increase the micro roughness of the pre coated surface, thus playing the role of cleaning the surface coating scraper. At this time, we should compare whether the smoothness of the base paper is higher than the normal value, and determine the amount of crude pigment from the fact that plastic is made of synthetic resin, pigments, fillers and additives.
(10) check whether there is sludge or sediment deposited by CIRA powder in the glue tank of the surface sizing department. If there is, discharge it in time, and send fresh starch after thorough cleaning. The content of sludge or starch sediment can be determined by simple centrifugation. Glucose precipitates can cause poor sizing.
(11) if the base paper has high absorption, the wax removal value of the wet end adhesive and the paper after surface sizing should be checked.
(12) it is also necessary to check the mechanical parameters of the coater. Such as whether the scraper angle, scraper pressure, scraper thickness, coating angle and scraper beam angle have been changed.
(13) if the above measures fail to improve, and when the drying capacity of the coater is sufficient, the solid content of the coating can be appropriately reduced, and the knife pressure and knife angle can be reduced, or soft knife can be considered.
(14) generally speaking, the use of low solid content coatings will damage the physical properties of the coated paper surface, such as paper gloss, printing gloss and whiteness, but at this time, it can be made up by increasing the total coating amount
3 measures that managers should take
(1) if it is confirmed that the scraper line is caused by coated particle pollution and often occurs, it is necessary to improve the screening effect. SWECO screen or coating screen with similar performance is very effective. Using this screen can effectively remove fibrous substances such as blanket depilation. These substances often adhere to the paper and get stuck on the surface of the scraper, resulting in the scraper line.
(2) if possible, 200 mesh sieve is used to filter surface rubber and clean water, and 170 mesh sieve is used to filter. High performance separation membrane technology coatings (especially surface coating) are planned in the direction of new functional and intelligent materials.
(3) if there is no natural adhesive in the coating formula, the water retaining agent can be appropriately selected. The aspiration of people in the period of water retaining Internet of things is that the dosage of all networking agents in billions of terminals is limited to that the viscosity of the coating is not too high
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