How to filter film gravure ink (one)
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
The VOCs emission problem of the gravure printing process has been a long-standing problem, and a series of major environmental pollution incidents such as smog and PM2.5 exceeding the standard have become catalysts for solving the problems of gravure VOCs. The printing industry, once considered a city industry, is now listed in the polluting industry, which is indeed a very sad thing. The relevant local standards promulgated in Guangdong, Shanghai and Beijing have meant that a new round of sanctions will be imposed on the discharge of VOCs in the printing industry. At the same time, the exit of the printing company from Beijing has also brought shock to the printing industry. In 2014, the Beijing Municipal Government announced that the Catalogue of Prohibitions and Restrictions for New Industries in Beijing (2014 Edition) requires packaging and decoration printing enterprises to withdraw from Beijing. However, the "Beijing New Industry Inhibition and Restriction Catalogue (2015 Edition)" published on August 24 this year has been revised. The packaging and decoration printing enterprises using solvent-based inks have withdrawn from Beijing, which is offset printing (in the packaging and printing industry). More than 50%) left a door. Therefore, the problem of gravure VOCs must be solved, how to solve it? The answer is ink.
First, it is necessary to clarify the points. First, the inks described in this paper include water-soluble and water-dispersible inks; second, the content of organic solvents in inks does not exceed 5%; and third, the substrates are non-absorbent plastic films. With metal foil, it does not contain paper gravure ink, because gravure ink can be absorbed by the osmotic absorption on the paper to help volatilize and dry, and this technology is basically mature.
Ink is the fundamental way to solve the problem of film gravure VOCs
Controlling the emission of VOCs based on the outlet end is an effective solution to recover the organic solvent in the gaseous state, but this method will bring cost pressure to the gravure printing enterprise. Beijing Amco invested more than 10 million yuan and equipped 4 sets of two-stage desorption normal temperature solvent recovery equipment for 4 gravure printing lines. At present, 2 sets have been installed and put into trial operation. It is said that 812 tons of organic solvents can be reduced every year. . It should be noted that this more than 10 million yuan is only equipment investment, and does not include the daily operating expenses of the equipment, that is, the expenditure of energy consumption, because no matter which technology is used for organic solvent recovery, energy consumption will be involved.
At present, the organic solvent recovery device is most successfully applied in the dry composite process because the dry composite process uses a single solvent ethyl acetate, and the single solvent ethyl acetate recovered by the organic solvent recovery device can be used directly. However, in the gravure printing process, a mixed solvent is used, and the organic solvent recovery device recovers a mixture of all the characteristic parameters of the solvent, instead of the directly available mixed solvent that reaches the original design index, and therefore must be rectified. . However, rectification requires technology, capital and energy. Gravure companies can't do anything. They can only be entrusted to professional organizations to deal with them, and then buy back at a lower price. The difficulty in the process and cost of mixed solvent recovery makes some unscrupulous operators even if they are equipped with an organic solvent recovery device on the gravure printing machine, but it is not commonly used. The government environmental protection department checks it before use it.
However, the situation is different now. From October 1st, the government has to charge for the pollution of VOCs in the printing industry. Therefore, the problem of film gravure VOCs must be solved, and the fundamental way to solve this problem is ink.
Quality points of film gravure ink
In order to ensure the quality of the print on the film, it is necessary to pay attention to several quality points of the gravure ink.
(1) Adhesion on the film. When printing on a non-absorbent substrate such as a film, the ink cannot penetrate through the substrate to adhere, and how to ensure the adhesion of the ink film on the film is the primary quality problem of the film gravure ink.
(2) Drying performance. The drying of the gravure ink on the film is mainly based on volatilization, but since the volatilization rate of water is very slow, the drying performance of the gravure ink must be considered.
(3) Is it easy to start the knife? The process of printing the solvent ink can not avoid the knife wire. In addition to the foreign matter embedded in the blade due to environmental factors, the main reason lies in the fluctuation of the solubility of the mixed solvent used. The gravure ink does not use a mixed solvent. In theory, there is no risk of solubility fluctuation caused by the inconsistency of the mixing ratio and the volatilization ratio, but the objective reality is that the wire in the printing is still inevitable.
(4) Viscosity change and control. Gravure enterprises are faced with the problem of controlling chromatic aberration, and the change of ink viscosity will affect the color difference of printed products. Because the viscosity of ink is different, the proportion and solid content of color paste in ink are different. Therefore, gravure companies generally measure the ink viscosity every 15 minutes, or use the ink viscosity automatic control device to automatically monitor the ink viscosity and automatically add organic solvents to help maintain the stability of the ink viscosity. There are few organic solvents in the gravure ink, but there are also problems with viscosity changes.
(5) Stability of the pH of the ink. The pH of the ink is generally between 8.5 and 9.5, and some inks may even reach or exceed 10.0. However, the pH value of the ink changes with the change of the ambient temperature. After the pH value fluctuates, the viscosity and transfer rate of the ink will change, which will cause chromatic aberration. Therefore, in the printing process, it is necessary to regularly monitor and adjust the pH of the ink, but this makes the frontline operators feel inconvenient.
(6) Scratch resistance of the ink film. The surface printing ink has specific requirements for the scratch resistance of the ink film, which is related to the hardness of the resin in the ink or the composition and proportion of the additive. The necessary scratch-resistant auxiliaries, which are found in the gravure solvent ink, should also be present in the gravure ink.
(7) Removal performance of ink on the plate roll. This is related to the problem of gravure printing. The industry always believes that this is caused by the fact that the printing plate is not scraped clean. It used to be the responsibility of the plate making factory and the gravure printing enterprise. In fact, this is a problem with the ink. If the removal performance of the gravure ink on the plate roll is good, the problem of gravure printing can be avoided.
Film gravure ink laboratory test content
How should gravure companies screen film gravure ink? This is an urgent problem in ink application. When using solvent ink, the gravure printing company will do some very effective pre-test work, including: 1 Transfer the ink to the film with a gravure bar, and measure the ink on the film with 3M 600/610 tape. Adhesion; 2 color density measured by X-Rite spectrodensitometer;
3 use the fineness test to evaluate the risk of gravure wire; 4 to evaluate the drying performance with the initial dry length; 5 to test the wear resistance and scratch resistance by nail or flat grinding method; 6 to detect the solvent residue by gas chromatography; 7 use Blocking The test method detects the heat-resistant adhesion of the ink. These provide a very practical and practical idea and method for film gravure ink inspection.
The film gravure ink and the solvent ink belong to the liquid ink, and the drying method on the film is mainly volatilization. The printing materials are polar and non-polar films which cannot be dried by the osmotic absorption method, and can be adapted to the printing and the printing. Different processes are printed. However, the viscosity of the solvent ink changes greatly, the viscosity of the ink changes little, and the ink needs to control the pH.
Film gravure ink laboratory testing should include the following: 1 adhesion test of ink on different polar films; 2 drying performance characterized by initial dry length; 3 fineness; 4 viscosity; 5 color density; 6 pH stability ; 7 ink film wear and scratch resistance; 8 organic solvent content; 9 surface tension. These are the things we have to do in the lab.
Tape method for measuring the adhesion of gravure ink on film
1. The basic principle of tape measurement
The adhesion of the ink to the film was measured using a 3M 600/610 tape, revealing the basic principle of adhesion of the ink to the film. First, the ink is slightly soluble on the surface of the film, sticky, and anchor points are established on the film. Secondly, the ink should be wetted on the film to make the anchor point as much as possible; then the solvent or water in the ink film is precipitated therefrom. The resin in the ink film is gradually crosslinked and strengthened. Nowadays, many gravure companies also use this method to detect the adhesion of gravure ink.
Why use 3M's 600/610 tape instead of ordinary sealing tape? Because the ordinary sealing tape is different from the glue formula of 3M Company 600/610 tape, the adhesiveness of the two is different, and it is attached to the ink film. The adhesion generated after the above is also different. The amount of adhesive force that the tape produces on the ink film is related to the glue formulation, which stipulates that the glue type specifies the adhesion. That is to say, when using 3M tape to test the adhesion of the tape to the ink film, we have specified that the force is determined by the viscosity of 3M Company 600/610 glue. Therefore, the tape is peeled off from the ink film, that is, the adhesive force and the anchoring force PK, the adhesive force is less than the anchoring force, which represents the adhesion of the ink film to the film; the adhesive force is greater than the anchoring force, which represents the adhesion of the ink film to the film. small.
It should be noted here that when the adhesion of the gravure ink on the film is not up to standard, we actually need to judge two reasons. First, the ink film is incompatible with the film, and the ink film cannot be anchored due to insolubilization on the film. Or because the anchor point is too small and lacks a strong foundation; the other is that the ink film does not dry out, the additive or moisture contained therein makes the ink film low in strength, and the bonding force is too small to resist the adhesion of the tape to the ink film. Both of these causes the ink film to be peeled off by the tape, but the solution is completely different. Therefore, when we judge the adhesion of gravure ink on the film, we must be able to clearly distinguish it without mixing.
It is also worth noting that many of the inks used in other printing processes are biased towards this principle. For example, UV ink, as long as the surfactant or amide additive is added to the UV ink, the surface of the ink film will be very slippery. Even if the ink film does not dry out, the tape will not stick and cannot be pulled down, which will cause UV. The ink film has been dried for misjudgment.