It is difficult to analyze and deal with the odor from film in flexible packaging. Especially when packaging pure water, milk, coffee, chocolate and other products which are extremely sensitive to odor, the odor in the film is very important. At present, the identification of odor mainly depends on the subjective judgment of people, and the final conclusion is drawn by statistical methods. The instrument can only be used when the content of some substance is relatively high, but it is not able to detect the trace amount.
Compared with glass, metal and other hard packaging, soft packaging is the biggest defect in terms of residual odor. No matter how well the control is, it can not completely eliminate all the flavor, and can only be acceptable to consumers.
The odor in the film mainly comes from these parts: first, all kinds of additives and their own low molecular substances of the resin itself; second, the odor produced in the film processing; third, the odor in the flexible packaging processing; fourth, the odor produced in the storage.
1、 Influence of resin itself
1. The film is usually made of high molecular weight resin. The resin is composed of molecules of different sizes, and the molecular weight distribution of different resins is different, and the content of low molecular weight is also different. Low molecular weight substances are easy to be oxidized and volatilized in extrusion process and produce odor.
2. Resin synthesis process: the solution method is different from the meteorological method in terms of odor. The solution method is better than the meteorological method in theory because many low molecular substances are removed after the solution is removed after the synthesis.
3. Many additives should be added to the resin to improve its performance. These additives are the biggest source of taste: the smooth agent is generally acylamide compounds, some sweet taste. The taste of antistatic agent is very pungent and can not be used in low odor packaging. The opening agent is generally inorganic, usually calcium carbonate and silica. But in terms of opening effect, silica is much better than calcium carbonate. But in terms of taste, calcium carbonate is better than silica. Antioxidants are usually phenols and have a certain taste. In general, antioxidants must be added to linear molecules because of the residual catalyst. Color Masterbatch: commonly used White Masterbatch will add some wax and stearate as dispersant and lubricant. These low-molecular-weight substances will be precipitated during the processing, so they are placed in the middle layer as much as possible in the multi-layer coextrusion.
2、 Influence of film processing technology
Generally speaking, the higher the processing temperature, the higher the odor. Because in the high temperature processing environment, the low molecular substances in the resin will be more volatile. A small amount of carbonic acid, aldehydes and other substances produced by high temperature oxidation can cause strong odor. Therefore, tape casting has a higher taste than blowing film theoretically. The equipment with internal cooling must be better than that without internal cooling equipment. The taste of the water-cooled downdraft will be the lowest.
3、 Influence of flexible packaging process
In the flexible packaging processing, ink, adhesive, solvent and printing compound process control also have great influence on the film taste.

1. Printing ink can be divided into benzene type and non benzene type, and non benzene type can be divided into polyurethane type and alcohol soluble type ink. Different base materials use different ink, and each series of ink has different taste due to different resin and pigment. Therefore, the choice of low flavor, solvent release effect of good ink in soft packaging processing is particularly critical.

2. In the compound processing, we usually use two-component solvent-based polyurethane adhesive, two-component solvent-based aliphatic adhesive and two-component solvent-free polyurethane adhesive. In order to ensure the different performance requirements of packaging bags, we have a lot of knowledge in the selection of adhesives. Various brands of adhesives have strong functionality, and the performance difference is relatively large, so we are in the choice It is necessary to consider not only the effect of adhesive itself on the taste of film, but also whether the strength of composite interlayer meets the requirements of customers.
3. In the evaluation of film odor, we found that if the solvent used for diluting ink and adhesive is not fully volatilized in the process of printing and laminating, too much solvent will remain between the composite film layers. After slow migration, these solvents gradually contact with the contents and change the taste of food. Therefore, it seems that reasonable process parameters should be set up Effective on-line control is very important.
In addition, with the rapid development of the industry in recent years, solvent-free coating technology has been widely used, it can effectively avoid the risk of solvent residue, should be said to be a good choice for composite processing.
4、 Storage conditions
Resin and finished products should be placed away from odor sources. Long term exposure to odorous environment, irritant molecules will adsorb on the surface, causing some special taste. The same is true in transit. Storage temperature should be lower than 35 degrees, otherwise low molecular substances will quickly migrate out, resulting in increased taste. In the processing workshop, the ambient temperature should not be too high, otherwise low molecular substances will be precipitated in the production process.
In a word, if we want to achieve the goal of low odor, we should first consider the selected resin in the design formula of the film. The various additives in the formula should be as few as possible, and the processing temperature should be as low as possible. It is best to choose the equipment with internal cooling or the process of water cooling with Down blowing. Flexible packaging processing should consider the materials such as ink, adhesive and processing technology, so as to obtain the film with low taste and customer satisfaction.
In addition, there should be a final evaluation of taste, and the evaluation method should be consistent with the customer. The adoption of international statistical methods will reduce the subjective factors and improve the reliability of the assessment.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, a world famous manufacturing city, is a subsidiary company of Beite packaging (China) Co., Ltd
With an area of 6000 square meters, it is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of advanced production equipment in China
We provide customers with high-quality products and first-class service with the support of the humanized management system and a group of experienced technical personnel.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for food, daily chemicals, and other special-shaped bags
Electronic, toys, medicine, cosmetics, industrial products and other industries of internal and external packaging.
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