Faults and Countermeasures in the composite proces

Faults and Countermeasures in the compounding process of aluminum foil and aluminum plated film

at present, aluminum foil and aluminum plated film are the most frequently used and fashionable substrate, but in the processing and compounding process of aluminum foil and aluminum plated film, if you don't pay attention, there may be quality problems, such as spots, white spots and other quality problems in the most common composite products. This paper will mainly introduce the faults and Countermeasures in the composite process of aluminum foil and aluminized film

spots

obvious white or gray spots after aluminum coating composite are all free maintenance points. These spots are the most common in the process of full-scale ink printing composite, and the main reasons are three aspects:

1 The quality of aluminized film itself is poor, the coating is easy to peel off, and the aluminized film and calendered film are uneven. In particular, the uneven flow of adhesive coating is more likely to produce dense or messy white dots of different sizes after lamination. The adhesive force produced by the ink and adhesive on its surface varies, and the adhesive force between the ink layer and the coating is low at the spot (spots caused by uneven dispersion of the ink or adhesive), resulting in poor tightness between the layers; The coating at the spot free place has been obviously transferred, and the interlayer tightness is good. At present, there are two pain points restricting the development of graphene through plating: one is the dispersion problem. The reflective intensity of the aluminum layer forms white spots or gray spots. The depth of the spots is closely related to the covering power of the ink and the amount of sizing, especially the leveling of the glue. Good covering power, light spots; The glue has good leveling property, uniform coating and less white spots. On the contrary, there are many spots and serious white spots. 2. Operating procedures of rubber tensile testing machine

2. The ink itself has poor tightness and covering power. After the printing film is glued, the ink layer is soaked by acetic alcohol in the adhesive, and some of it is dissolved. After compounding, the ink layer and adhesive layer are very easy to be soaked and destroyed by the solvent of the adhesive system, resulting in different shades, resulting in color differences, forming the so-called spots

3. The quality of adhesive is poor. This kind of adhesive has poor affinity for the aluminum coating, especially when the uneven adhesive is compounded with the aluminum coating on OPP printing film and BOPP printing film. The main reason is that this kind of adhesive has high surface tension, poor coating performance and uneven glue coating, resulting in spots. At the same time, this kind of adhesive generally has high initial adhesion and poor solvent release. Due to the influence of residual solvent after curing, the strength is not as good as the initial adhesion. After the printing film is compounded, the ink layer is soaked by residual solvent, which may also produce spots. The above phenomenon will be more obvious when this kind of adhesive is used on rolls with more than 150 lines at high speed. If the adhesive coating cannot slightly dissolve with the ink film of the printing ink, no white spots can be seen on the surface, but after the composite process, the adhesion between the adhesive layer and the ink layer, or even the printing film layer, cannot meet the actual requirements of the packaged goods and is very easy to peel off

generally speaking, there are many spots caused by the above three reasons, but we can use the following methods to eliminate this phenomenon:

1 Using ink with good hiding power is the most fundamental way to eliminate the spots caused by the previous reasons. You can also engrave the printing line roller to increase the thickness of the ink layer, but this will increase the cost

2. Using appropriate special adhesive for aluminizing film is an effective method to eliminate the spot phenomenon caused by the third reason. This special adhesive for aluminum coating has moderate and uniform molecular weight and low initial adhesion, but it has excellent coating performance, good solvent release, and good peel strength after aging. In addition, if there is no good special adhesive for aluminizing film, a deeper line roller can be used to reduce the working concentration, slow down the machine speed, and reduce or solve the spot phenomenon

3. If it is caused by pigments or fillers in the ink, spots often appear in three cases: (1) when titanium dioxide and other pigments are not equal to the particle size, and one of the pigments is in the flocculation state, but the density is the same, spots will appear; (2) Titanium dioxide and other particles with the same size, but different density, will also appear spots; (3) Titanium dioxide and other particles with different sizes but different densities will also appear spots. These three faults are most likely to be caused by flocculation after the addition of white carbon black or active particles produced by the long grinding time of ink. For this phenomenon, try to mix all the dry powder first and then put it into dispersion. You can also reduce the amount of white carbon black, or increase the dispersant or antistatic agent, or shorten the grinding time (because this fault mostly occurs on the large-area layout with little or no carving at all), so as to prevent the competitive adsorption between abnormal colors and fillers? One cluster adheres to the plate roller and is distributed on the printing surface after being scraped by the scraper. It is better to add CHY-1 printing auxiliary to eliminate spots

white spots

besides the white spots of the aluminized composite film, there are also obvious white spots on other composite films, which can be randomly distributed and uneven in size. One is from time to time when getting off the machine, but it basically disappears after ripening; The other is when getting off the machine, which does not disappear after ripening. The latter is the biggest problem affecting performance. Such spots are most likely to appear in the effect of printing on a white or light yellow background. Generally, as long as such white spots appear, they are generally full version (except for equipment reasons), but white and light yellow have poor hiding power and are easy to see. There are many reasons for the phenomenon of white spots, mainly in three aspects:

1 Ink particle size or particle size distribution is not wide, generally the particle size of white ink has a greater impact. Ethyl ester in the adhesive is a good solvent for ink. The results of soaking ink particles with different particle sizes are different. The chromaticity changes will be different after heating and compounding or drying in the oven, which looks like white spots. Generally, in this case, it is obvious when getting off the machine, and the white dot phenomenon will be reduced and may disappear after ripening. When printing, it is best to add 1.% M-27 coupling agent improves the tightness of pigments and fillers in the ink system to resist large areas of white spots or spots caused by solvent infiltration and destruction in the adhesive system

2. The adhesive has high surface tension and poor wetting and spreading effect on the aluminized film. This is the white spot phenomenon of aluminum coating at present, and it is also the main reason for spots on other composite films. The coating effect of adhesive is not good. After the printing layer is covered, the color of different parts will change, producing the same effect as before, and sometimes producing large spots

3. Equipment process reasons. On the one hand, the workers are not aware of the particularity of aluminized film compounding, which has its unique features. On the other hand, the pressure on both sides of the equipment in the sizing process is inconsistent, and even the problems of the drying, coating and other systems themselves cannot ensure the full and uniform coating of the adhesive or the full volatilization of ethyl ester. There are other reasons, such as the roller grain of the full bottom printing line is too shallow, which reduces the ink coverage, etc

white spots can be eliminated by taking the following measures:

1 The fineness detection index of different batches of inks shall be increased and strictly controlled, especially when the particle size and fineness of full bottom inks are outside the standard range

2. Special adhesive for aluminizing film is used. The surface tension of the special adhesive for aluminized film composite is low, and the coating and spreading effect on the surface of aluminized layer is significantly better than that of general-purpose adhesive. It is very easy to control the leveling of the glue liquid by using aluminized film bonding, which has an ideal coating state. In terms of the adhesive coating state alone, the use of aluminized adhesive can eliminate the phenomenon of white spots

3. The adhesion of rubber liquid is one of the indispensable equipment in the work of testing rubber quality There is a certain matching relationship between MP ⑶ type grinding degree and the number of line rollers. If it exceeds the matching range too much, the coating state of the glue will be damaged, resulting in the generation of white spots and more serious other faults. However, it seems that the generation of white spots is the main concern on the aluminum coating film

4. Aluminum coating and gluing are adopted. The commonly used coating process is the coating of printing film (protective layer). Here, a special coating method is used to avoid the uneven penetration of ethyl ester into the ink layer, but this process has great limitations. First, it is limited to the compounding of VM pet. Secondly, a certain peel strength will be sacrificed

5. The manufacturer must adhere to the regular cleaning system of the coating roll and master the correct cleaning method of the coating roll. When producing full white background or line yellow printing film, we should pay attention to two points: first, thoroughly clean the scraper, coating roller, flattening roller, etc. before production; Secondly, for the old domestic dryer, the machine speed is slower than the normal speed to ensure the drying effect

pitting

pinholes (blank spots/pitting) caused by foam in the ink are often printed on the aluminized film. General troubleshooting methods: first, tighten the composite roller; Second, increase the amount of coating glue; Third, add defoamer dimethyl silicone oil; Fourth, try to use a straight scraper, and increase the blade of the scraper by mm, or use a soft blade (such as a steel tape instead), and adjust the angle of the scraper to not less than 45 degrees; Fifth, put a rubber on the back of the scraper to effectively scrape off the spots caused by poor dispersion in the printing graphic ink glue system or oxide crusts in the ink bucket; Sixth, white carbon black is added to the printing ink to thicken the ink film of the printing ink and improve the hiding power of the white ink film; Seventh, reprint it to improve the thickness of the ink film; Eighth, select the gravure with deep engraving to improve the transfer rate of ink; Ninth, put a stirrer in the ink bucket to ensure the uniformity of printing ink during transfer; Ten is to replace the printing ink with high viscosity and anti-static or slow down the printing speed, and strive to achieve the purpose of eliminating pockmarks, pinholes, spots and white spots

in actual production, only efficient additives and new materials can make up for the shortcomings of its aluminized composite printing products and improve the quality of packaging and printing process