Problems and Countermeasures in Dry Compounding

Solvents used in rubber dispensing Due to the chemical nature of polyurethane adhesives, solvents containing water, alcohols, amines, esters, etc., that contain active hydrogen or reactive groups are not allowed to be used in the preparation of adhesives, but only highly pure esters, Inert solvents such as ketones, hydrocarbons (alkanes or aromatic hydrocarbons) also need to consider the safety of the product and avoid odors and odors.
Toxic aromatic hydrocarbons such as toluene and xylene should be used as little as possible. Methyl ethyl ketone (ie, ketones) with heavy odors should also be used sparingly. It is best not to use these problematic solvents. In the case of having to use, it is necessary to work hard on drying, to ensure that they are as volatile as possible, and the amount of residue is as small as possible.
The economically developed countries are very sensitive to the hygienic properties, odors, and odors of packaging materials, and those who have slight problems cannot pass. So if you are using for packaging of export products, you must pay special attention!
In recent years, when exporting products, the content of aromatic hydrocarbons in the residual solvent of packaging materials is often too high. After being loaded into food, it migrates to the food through the inner layer material and is adsorbed by the food, resulting in odor or toxicity of the food. Abroad is not accepted and returned. Sometimes there is such a problem: the composite bag smells no smell at room temperature, but when the bag is still hot food (such as freshly baked cookies from a processing line), it is cooled. When the food was tasted, unpleasant odor appeared. This was because the migration of residual solvents was promoted when the temperature was high.
This odor problem is often caused not only by the adhesives and the solvents used, because many plants only use ethyl acetate ethyl esters, but toluene remains on the packaging bags. Odor odor of butanol or xylene, which is the reason for printing inks. Today's composite printing inks mostly use "composite inks," which are so-called "printing inks." Solvents are used in this type of ink. In addition to the ethyl ester ethyl ester, there are odor-toxic and high-boiling solvents such as butanone, xylene and butanol.
Because the pigment particles in the ink are small, the specific surface area is large, and the adsorption ability is very strong. Although it has been heated and dried during printing, due to short time and high speed, the drying is often incomplete, and the residual solvent is too much, especially in a large area. This is especially true for multiple sets of printing. These residual solvents are brought into the compounding process and are harder to run off after compounding. They have to slowly migrate and infiltrate, so the above problems will occur.
There are two ways to solve this problem:
(1) Strictly determine the drying process so that the amount of residual solvent is minimized. For example, western countries require residual solvents below 5 mg/m2. Because it is less noticeable, it is not yet a fundamental solution to the problem.
(2) To fundamentally solve the problem, it is necessary to use high-boiling inks, solvents, and adhesives that do not contain toxic, odoriferous, and odoriferous substances as described above, and use ethyl acetate, alcohol, and acetone whose boiling points are low. Isopropyl alcohol and other non-toxic, low toxicity, no smell odor solvents. Two-component high-performance, versatile polyurethane inks eliminate the need for aromatic hydrocarbon solvents, and alcohol-soluble oils have no disadvantages. If there is no problem with the ink and the amount of residual solvent is small, there is no need to worry about it.
Another problem with solvents is that they should not be abused or abused. In the past, in order to save costs, industrial-grade banana water was used to dilute the adhesive. As a result, the glue was stratified and turned turbid and bluish quickly, resulting in the inability to use it. This turned out to be counterproductive. It not only did not save money, but it was even more wasteful. Also, because the factory that makes composite packaging materials prints, composites, and bags itself, the warehouse contains both ethyl acetate, toluene, xylene, alcohol, isobornyl alcohol, butanone, etc. Mistakes, improper use, there will be problems, need special attention. It is best to store the ethyl acetate in a separate library, not to mix it with other solvents, and to strengthen management and improve identification.