Problems and Countermeasures in the combination of

2022-09-19
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Problems and Countermeasures in dry compounding

solvents used in glue preparation

due to the chemical characteristics of polyurethane adhesive, it is not allowed to prepare glue solution. 2. The indication deviation caused by the incorrect dynamometer device allows the use of solvents containing active hydrogen or reactive groups such as water, alcohol, amine, ester, etc., but only inert solvents such as esters, ketones, hydrocarbons (alkanes or aromatics) with high purity, taking into account the health and safety of products and avoiding odor Stink

toxic aromatic hydrocarbons such as toluene and xylene should be used as little as possible, and heavy smelling methyl ethyl ketone (i.e. lower ketone) should also be used less. These problematic solvents are best not used. When it has to be used, it is necessary to work hard on drying to ensure that they volatilize as clean as possible and the residue is as small as possible

economically developed countries are very sensitive to the hygienic performance, peculiar smell and odor of packaging materials, and those with slight problems cannot pass the test. Therefore, if it is used for the packaging of export products; Let your work no longer have flaws, pay special attention

in recent years, when exporting products, the aromatic hydrocarbon content in the residual solvent of the packaging material itself is often too high. After being loaded into food, it migrates to the food through the inner material and is adsorbed by the food, resulting in the peculiar smell or toxicity of the food, which is unacceptable abroad and is returned. Sometimes there is such a problem: the composite packaging bag can't smell peculiar smell at room temperature, but when the packaging bag still contains hot food (such as baked cookies just made from the processing line), when the food is tasted after cooling, there is an unpleasant peculiar smell, because the high temperature promotes the migration of residual solvents

this peculiar smell problem is often caused not only by the adhesive and the solvent used, because many factories only use ethyl ester solvent, but toluene is still left on the packaging bag. The odor of butanol or xylene is the original reason of printing ink. Nowadays, composite printing inks are mostly used, which is the so-called inner printing ink. In addition to ethyl ester, solvents used in this ink include butanone, xylene, butanol and other solvents with high boiling points, odor and toxicity

because the pigment particles in the ink are very small, the specific surface area is very large, and the adsorption capacity is very strong. Although they have been heated and dried during printing, due to the short time and fast speed, they are often not completely dried, and there are too many residual solvents, especially in large-area and multiple sets of printing. These residual solvents are brought into the compounding process, and it is more difficult to run away after compounding, so they have to migrate and penetrate slowly, so the above problems will occur

there are two ways to solve this problem:

(1) strictly determine the drying process to minimize the amount of residual solvent. For example, western countries require that the residual solvent be less than 5mg/m2, and the moisture absorption is small. Because the quantity is small, we can't detect it, but this is not the fundamental solution to the problem

(2) to fundamentally solve the problem, we must use high boiling point inks, solvents and adhesives that do not contain the above toxic, odorous and smelly, and only use ethyl esters, alcohol and acetone with low boiling points. Isopropyl alcohol and other non-toxic, low toxic, odorless solvents. Two component high-performance, versatile polyurethane ink does not need to use aromatic solvents, and alcohol soluble oil has no shortcomings. If there is no problem with the ink and the amount of residual solvent is small, there is no need to worry

another problem related to solvents is not to abuse or misuse them. In order to save costs, some units used industrial grade banana water to dilute the adhesive, which resulted in delamination of the adhesive liquid, which soon became muddy and white, resulting in failure to use. Instead of saving money, it was even more wasteful. In addition, because the factory that makes composite packaging materials prints, compounds and makes bags by itself, there are ethyl acetate in the warehouse, as well as toluene, xylene, alcohol, isointernal alcohol, butanone, etc. that effectively graft the innovation chain and the industrial chain. If the management is not good, the wrong solvent or wrong material will be obtained, and the use is not appropriate, there will also be problems, which need special attention. It is best to store ethyl ester in a separate warehouse, not mixed with other solvents, and strengthen management to improve recognition ability

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