Answers to problems in the use of the hottest wate

At present, there are more and more water-based composite adhesives (hereinafter referred to as water-based adhesives) on the market, and more and more manufacturers use water-based adhesives. However, when using water-based adhesives to composite products for the first time, there are some problems that need to be paid attention to, which must be understood, otherwise there may be a lot of trouble and unnecessary losses. The author has done some application experiments on the yh620s water-based adhesive produced by Beijing GAOMENG Chemical Co., Ltd. in the factory, and compared it with several existing products in the market. It was found that the weight decreased from 15kg to 6kg, and some experiments were made to find better solutions to these problems, which were summarized as the following aspects

I. how to select the top roller (line roller)? How much glue is suitable

the amount of water-based glue is small, so it is important to choose the right glue roller. For water-based adhesive, the pit on the rubber roll should be shallow and the opening should be large, so that the glue can contact the substrate with the largest surface area, so that the coating is uniform, the drying speed is fast, the composite appearance is good, and the peel strength is high. The proper line roller is the premise to ensure the glue amount and peel strength, and the user should adjust it according to the equipment conditions and compounding speed. It is recommended to use 180 line/inch ~ 200 line/inch electric engraving roller. The pit is connected, and the pit depth is 32 μ～ thirty-five μ。 In the process of use, the upper rubber roller should be cleaned frequently to prevent blockage, and after a period of use, it should be chrome plated again or engraved with a new wire roller

the appropriate glue amount is 1.6g/m2 ~ 2.4G/m2, which cannot be lower than 1.6g/m2, otherwise the peel strength cannot be guaranteed. Too much glue will affect the drying of glue and the leveling of glue on the surface of plastic film, thus affecting the composite appearance and peel strength

second, how to solve the problem of too many bubbles during high-speed recombination? Can defoamer be added

in order to catch up with the production progress and reduce the cost, some manufacturers have fast compound machines, some of which reach more than 160m/min. For this compounding speed, the water-based glue is easy to produce more foam in the glue tank. If the production continues for several days, the foam will accumulate more and more, and even overflow out of the glue tank. At this time, if certain measures are not taken, it may lead to problems such as small glue amount, low strength, white spots on the appearance, etc. The best solution is to put a uniform ink stick in the glue tank to defoaming. At the same time, adopt the method of cyclic gluing to ensure that there is not too little glue in the glue tank. A spare rubber barrel should be used for recycling, so if the foam in the rubber barrel cannot be eliminated during long-term operation, the spare rubber barrel can be used to apply glue, and it can be replaced after the foam in the original rubber barrel is eliminated

yh620s products already contain defoamer, so it is generally unnecessary to add additional defoamer. Too much defoamer will affect the surface properties of the glue liquid, thus affecting the composite appearance. The added defoamer cannot be mixed evenly with the glue liquid, which will also affect the composite appearance

III. can water-based adhesive be diluted with water

at present, most of the water-based adhesives on the market are lotion type. The principle is that high molecular polymers rely on emulsifiers to stabilize in water. In fact, it is a metastable state, and many external forces will lead to the demulsification and delamination of the glue, which will lose its function. The author does not recommend diluting the glue with water, because diluting with water will increase the surface tension of the glue, destroy the stability of the glue, and cause delamination. In addition, dilution will change the surface properties of the product, resulting in poor wettability and affecting the composite appearance

IV. when using water-based adhesive composite, some white spots appear on the appearance, and they disappear after ripening for a while. What is the reason? How to avoid this

generally, water-based adhesive contains more than 50% of water, and it needs sufficient temperature and wind speed to completely volatilize in a short time. There are two reasons for white spots on the appearance of composite products: insufficient glue application and incomplete drying. The white spots that can disappear after a short period of ripening indicate that the drying is not complete, because ripening can further help the evaporation of water; Otherwise, it means that the glue amount is insufficient

to avoid incomplete drying until the working surface of the board is cleaned by visual inspection, it is necessary to adjust the temperature and wind speed of the drying channel

the oven temperature can be set to 70 ℃ ~ 80 ℃ 90 ℃, but the author found that the actual temperature of many composite equipment is much lower than the set temperature, so if possible, it must be corrected to avoid too much error. The wind speed is particularly important for the drying of water-based adhesive. It must be ensured that the wind speed reaches more than 6m/s, and the air outlet and inlet of the equipment should be cleaned frequently to prevent blockage. In addition, the temperature of the composite roll will also affect the composite appearance and the initial adhesion. It is necessary to ensure that the actual temperature of the composite roll reaches more than 50 ℃

v. does the film compounded with water-based adhesive need to be matured? Will the peel strength be improved after aging for a period of time after getting off the machine? Will it be affected by high temperature aging for a long time

generally speaking, the membrane compounded with yh620s does not need to be matured and can be cut off the machine. Among them, impact resistance is the main factor to be considered in design. When maturing for a period of time, the peel strength can be improved, because the molecular weight of water-based adhesive is very high, and it needs a certain time to level to achieve better strength. Therefore, it is better to put the composite membrane in 50 ℃ curing room for 1H ~ 4H when conditions permit. Aging at higher temperature for a long time (above 80 ℃) has a certain impact on the strength of the composite membrane, because the water-based adhesive polymer can not withstand high temperature for a long time

VI. will water-based adhesive affect the adhesion of ink on the film? Why is there a great difference in the appearance of films printed with different inks

water-based adhesive has good adaptability to water-based ink and solvent based ink. Ink transfer is generally related to the quality of ink. If the affinity between the ink and the film is poor, the adhesive may pull the ink down from the film. This problem does not exist when using high-quality ink

the ink contains different waxes, smoothers, defoamers, plasticizers, etc., which will have an adverse impact on the glue, and then affect the composite appearance. Therefore, after replacing the ink, the glue should be tested to avoid losses

reprinted from: printing industry