Selection of the hottest adhesives and analysis of

2022-07-25
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Selection of adhesives and analysis of common quality problems

caused by "difficult bonding"

with the progress of social civilization and the demand of the market, more and more new materials and new processes are used in the packaging industry, and bonding has become an important material for the complete packaging of a product, which is more and more used in the packaging industry. Our company produces and sells various printing and packaging adhesives in China, We have had a lot of contact with many domestic printing and packaging factories. During this contact process, we surprisingly found that many manufacturers (including some large printing and packaging factories) are experts in printing, but they do not know enough about viscose. Many are even blind in selecting and using adhesives, which has brought great losses and waste to various manufacturers. "Difficult adhesion" has become a ghost that puzzles all packaging factories, causing headaches to almost every packaging and printing factory

our company is a professional manufacturer of printing and packaging adhesives. We believe that the problem of "difficult bonding" can be completely solved as long as we select and use good adhesives. Based on the experience and lessons of many manufacturers, the problem lies in the two links of "selection and use". In order to let many colleagues engaged in technical work, quality management and supply work know more about adhesives, make "difficult bonding" become "easy bonding", and change "worrying about adhesives" to "reassuring adhesives", we have prepared this pamphlet to discuss the production and use of adhesives with our domestic counterparts, Make our contribution to the prosperity of China's packaging industry

how to choose adhesives

understand the use characteristics. Any adhesive is not omnipotent. An adhesive can only be suitable for a certain or a specific type of bonded material. Some manufacturers blindly use glue with a "try" mentality, which not only wastes time and energy, but also causes great losses. At present, bopp/paper, polished/paper, pet/paper and high gloss printing paper/paper are commonly bonded by various packaging factories. In fact, this kind of product only needs one product of our company, namely 810 sealing adhesive, which can meet all the requirements of the above products, and more than 98% of the products of various packaging factories are the above materials. In addition, there are some manufacturers such as pvc/paper, pvc/wood, uv/paper, etc. these products can be solved with other types of glue of our company. (such as PVC adhesive, 818uv special sealing adhesive)

2) quality standard

as an adhesive, the most important quality standard: A. bonding strength (adhesion); B. High temperature resistance; C. Low temperature resistance; D. Aging resistance; E. Retention of bond strength. In many domestic packaging plants, the bonding is not firm, or the product is brittle for a period of time, and the degumming is basically the above situations. Therefore, it is often heard that some printing and packaging factories say that "some glues are degummed in hot weather, some glues are degummed in cold weather, and some glues are not stored for a long time regardless of cold weather or hot weather". In fact, this is because they do not have a deep understanding of the quality standards of glues, and even some factories producing viscose do not know why they want to degumm, so it is not surprising that there are quality problems in the production process

3) performance

our 810 sealing adhesive and 818 sealing adhesive are miscible multi-functional paper plastic adhesives. They have strong initial adhesion, high bonding strength, good high and low temperature resistance, good bonding retention, good moisture resistance and wide bonding range. Software is open. Only one or two adhesives are needed to basically meet all the bonding requirements of the current packaging factory (bopp/paper, polishing/paper, pet/paper, UV light/paper, ink/ink), and are welcomed by many manufacturers. The disadvantage of miscibility is that the cleaning ability of containers and utensils is slightly poor, and the wild glue has to be wiped with solvent (due to its good moisture resistance). Therefore, when selecting viscose varieties, manufacturers should understand the characteristics, performance and scope of application of each variety according to their own actual situation. At the same time, you should also have a certain understanding of the manufacturer providing viscose, such as whether the product is mature, the stability of the product, the degree of understanding of the product, technical strength, etc. Otherwise, the blind use of glue will do great harm, because the viscose products are lagging behind, and many degumming only appears after a few days or even months, so the use of glue must be cautious

4) price

selecting adhesive can leave the eyepiece on the lens barrel. The quality must be the first and the price the second. Some manufacturers blindly believe that the higher the price, the better the quality, or the lower the price, the worse the quality. These views are very one-sided. Therefore, some manufacturers not only spend money, but also cause great losses. In fact, viscose only accounts for a small proportion of the cost of a packaged product. Therefore, we believe that it is reasonable to seek an appropriate price on the premise of understanding product characteristics, quality standards and performance

adhesive properties and test methods of sealing adhesive

a batch of finished packaging boxes will not be used immediately, and sometimes they may be stored for months or even a year. Therefore, the cold and heat resistance and aging resistance of an adhesive are very important. For example, some packaging boxes have good bonding effect in a short time after they are finished, but after they are put for a period of time, there are phenomena such as degumming and brittle adhesive film. Therefore, the following aspects should be tested to determine the bonding performance of an adhesive

first, tear a bonded packaging box along the edge to observe whether the bonded substrate is torn. At the same time, scrape the paper base attached to the film with your fingernail. If you can only tear off a small piece of paper base each time or can not scrape off the paper base at all, it indicates that the adhesive has good adhesion to the film. The two bonded surfaces of plastic/plastic sealing adhesive are BOPP film, which cannot be damaged due to its strong flexibility. Therefore, it is sufficient to feel that the two bonded surfaces have strong adhesion during inspection

second, place the bonded packaging box (which has been placed for at least one day) in a constant temperature oven at 60 ℃ for 72 hours. After taking it out for cooling, the edge seam or bottom opening will not pop up. At the same time, pat the packaging box with both hands without degumming and the adhesive film will not be brittle, indicating that the heat resistance of the adhesive is no problem

third, put the bonded packaging box (which has been stored for at least one day) in the freezer and freeze it for 72 hours. After the box is dry, pat the packaging box with your hand without degumming and the adhesive film is not brittle, indicating that the low temperature resistance of the adhesive is no problem

fourth, save some samples of the products bonded by the three adhesives that have passed the previous three. Inspect a packaging box every half a month. The two hands can not degumm, and the adhesive film is not brittle. Continuous inspection for half a year shows that the sealing adhesive can be used safely

common problems and cause analysis of sealing adhesive in use and storage of finished products

1. Problems prone to occur in the bonding process: ⑴ glue overflow after pressing due to too thick amount of glue brushing, which not only affects the beauty of the product, but also prone to mutual adhesion between packaging boxes. In this case, the adhesive shall be placed in the air for 2-5 minutes after brushing, and then pressed after the adhesive is slightly dry. ⑵ the glue is brushed too thin and the drying time is too long, which leads to poor adhesion fastness, and sometimes it can not be adhered at all. In case of such situation, you should understand the instructions or consult the manufacturer. (3) the bonded product will automatically spring open without pressing or because the pressure is too small. This situation is mainly aimed at the products with large stiffness, which must be pressed for at least half an hour. Because many adhesives are contact adhesive, the two bonded surfaces must be effectively pressed. In unit time, if the initial adhesive force is less than the product elasticity, the product will spring open, so the pressing time of 0.5 hours is required for general products. (4) in order to save money, some manufacturers use compound film adhesive and milky glue to stick boxes or use a large amount of water to dilute the adhesive, resulting in insufficient bonding fastness and poor adhesion on the film. This situation is very dangerous, and it is also a serious violation of the bonding principle and process. I hope that all adhesive users must not blindly use the adhesive to cause greater losses to themselves

2. Problems occurred during storage of bonded products

the packaging box was degummed in cold winter. The main reason is that some adhesives have poor low temperature resistance. The loss of magnesium alloy on the surface of adhesives below 5 ℃ is the most potential metal material in the automotive industry. The activity leads to the decline or disappearance of adhesive force. (2) in hot summer, the glued packaging box pops off in the warehouse or transport truck. The main reason is that the adhesive has poor high temperature resistance. At the temperature of 50-60 ℃, the adhesive layer becomes soft and the strength becomes smaller, resulting in the degumming of the packaging box. (3) the bonding effect of the packaging box is very good at the initial stage (within half a month), but the packaging box degumming occurs with the extension of time. The main reason is that the adhesive itself has poor adhesive durability. Most of them are plasticizers added to the adhesive. With the extension of time, the plasticizer migrates to the paper base, resulting in the hardening and brittleness of the adhesive layer and the degumming of the product. On the other hand, because the adhesive contains a large number of unsaturated bonds, the aging resistance of the product is poor, the storage period is prolonged, the adhesive film becomes brittle, and the product is degummed. (4) the warehouse is very humid and stored in it for a long time. Not only the humidity of the products exceeds the standard, but also the products are degummed. The main reason is that the product absorbs water, and the water resistance of the adhesive itself is not good, resulting in the softening of the adhesive layer and delamination. A series of sealing adhesives produced by us have certain water resistance, so the overflow glue should be wiped with solvent, and the container cleaning should use water and solvent

characteristics and application methods of water-soluble laminating adhesive

the laminating mechanism of the adhesive is to adjust the liquid adhesive to the correct position according to the requirements, apply the liquid evenly on the film, and then directly wet bond with the printing paper, so as to achieve the purpose of bonding through the penetration of adhesive molecules. Now, several problems worth paying attention to in the composite process are put forward for your reference

1) the adhesive is a water-based adhesive. The printed matter to be compounded must have strong water absorption. The printed matter with poor water absorption capacity cannot be compounded with this kind of adhesive

2) for printing products with gold ink, samples must be taken first. Only when there is no discoloration reaction to gold ink can they be used in batches

3) the recovered product can be cut off on the winding rod only after the adhesive film is transparent, which takes about 20 minutes

4) if it is necessary to press the concave convex of the laminating product, it must be put aside for 24 hours

5) if the four corners of the paper jam after lamination are warped, it may be caused by too much glue, resulting in too much shrinkage stress of the adhesive layer, or the water content of the paper jam is too high, which should be controlled

6) glues from different manufacturers shall not be mixed to avoid glue polymerization and affect the lamination effect

7) if the temperature is below 10 ℃, the low-temperature activity of the adhesive must be tested before use. If the low-temperature performance is not good, the method of water bath heating must be used to make the adhesive temperature reach above 10 ℃. So as to achieve the purpose of full bonding

inspection method for quality of laminating products

1) kneading inspection method

take a laminating sample of appropriate area, knead it back and forth with both hands like washing clothes, and see that there is no separation or blistering between the plastic film and the printed matter, and the bonding is firm, which indicates that the product quality is reliable

2) tear off test method

uncover and tear off the plastic film layer on the laminated sample sheet by hand to see if the printing ink layer can completely adhere to the film or tear off the paper base. If so, explain

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