The odor produced by composite flexible packaging materials is a major quality accident. The author thinks that in the flexible packaging industry, the odor problem is worth studying. Relatively speaking, it is a relatively general concept, and there are many reasons, which requires: "only by analyzing and finding corresponding preventive measures can the odor problem be reduced to the lowest point." Peculiar smell, especially food packaging materials, has strict requirements on odor. Some foods with low taste, such as milk powder, cheese, biscuits, cornflakes, etc., are more sensitive to odor. All kinds of modifiers, additional materials and thermal degradation of polymer materials can produce peculiar smell. Therefore, the odor produced by packaging materials is various, complex and changeable. There are sweet, sour, medicinal, burnt, paraffin, oil, ink, tar, solvent and so on. Now we analyze this and propose countermeasures.
1、 Source of odor:
1. For PVC film which is easy to produce thermal decomposition, it is no longer used in food composite flexible packaging materials. At present, the peculiar smell produced by thermal decomposition of polyethylene is more prominent, because polyethylene is widely used in the inner thermal seal of composite flexible packaging, and directly contacts with the contents of the package. The components that produce peculiar smell by decomposition of polyethylene can be roughly divided into aliphatic hydrocarbons and aromatic hydrocarbons. According to the research, LDPE thermal decomposition into c3-c28 saturated or unsaturated hydrocarbons, of which C3-C6 produced by short branched chain has the greatest impact on the content. In addition, when plastic is processed at high temperature and high shear force, in addition to thermal decomposition, especially after extrusion, it will react with O2 in the air, and the substances produced will also cause odor. In the actual production process, the temperature control is divided into three parts: "barrel temperature, connector temperature, touch head temperature." The temperature control level is related to the actual material parameters. Of course, odor, and the processing of plastic particles, its own quality has a lot to do with. If the plastic particles have their own peculiar smell, they will produce the same smell during hot processing, and they will be more serious at high temperature. Therefore, this requires manufacturers to strengthen the awareness of quality management to prevent the processing of unqualified raw materials. At the same time, it also puts forward higher quality requirements for suppliers. It is suggested that the environment should be well ventilated during the production and processing, and the micro hair dryer should be placed nearby when the finished product is rewinding. For the improvement of air cooling, the product can not be packaged in time, so as to let the product have enough time to volatilize the odor.
2. Odor produced by plastic additives: in the process of plastic processing, in order to improve the processability or to improve and change the performance of products. Will be added into a variety of additives, varieties are very complex, different ingredients of additives is one of the main factors causing odor. Such as: "plasticizer, heat stabilizer, antioxidant, anti ultraviolet agent, blending agent, antistatic agent, antifogging agent and so on." In addition, functional inorganic additives, such as calcium carbonate, kaolin, talcum powder and silica, will be added, and a large number of dispersants and coupling agents will be brought in. Moreover, the addition of a variety of organic pigment masterbatch, Titanium White Masterbatch, etc., will produce a lot of volatile substances when heated. If the pigment can promote the decomposition of polymer, it will also produce serious odor during heat sealing. According to experience, when the thickness of PE film is more than 60um, the peculiar smell will be obvious. The main reason for the burnt flavor is that the additive of the opening agent exceeds the standard. At the same time, the peeling strength is greatly reduced due to the precipitation of additives;

3. Odor caused by plastic aging. All kinds of plastic materials, if stored for a long time, will cause decomposition and oxidation under the action of oxygen, ozone, moisture in the air, especially under the action of ultraviolet rays, which will make the polymer aging and produce peculiar smell. In addition, the additives in plastics, like the plastics themselves, cause oxidation and odor under the action of O2 and UV. Generally, the storage time of plastic film, peeling strength decrease, produce odor, and affect the quality are in direct proportion. Therefore, we require color printing enterprises, in a certain period of time must be used for material, serious testing.

4. Peculiar smell caused by ink, adhesive and residual solvent. In the composite flexible packaging materials, the main cause of odor is the residual solvent of ink and adhesive. Especially in the dry composite process, solvent residue is unavoidable. At present, the national standard requires that the residual solvent should be less than 5mg / m2, which is related to many factors, such as process: (1): diluents such as toluene, ethyl ester, butanone are often used in printing products The purpose is to improve the dispersion and transfer of ink, so as to improve the printing quality. If the diluent volatilizes incompletely in the production process, the surface layer is dried, and the inner layer is still wet, the solvent volatilization rate is relatively slow. With the continuous increase of winding, the residual solvent will increase and the odor problem will occur. (2) In printing, we suggest to reduce and use high fo point solvents such as butanone and dimethylbenzene as far as possible; in the actual use process, it is recommended not to exceed 30% of the mixed solvent, and chlorinated polypropylene ink is mostly used by general flexible packaging enterprises. Often mixed flux ratio is: toluene: butanone: ethyl ester = 70%: 20%: 10%. The advantages of using mixed solvent are: improve the ink dispersion, increase the liquidity, improve the transfer rate; but because of technical problems, or unreasonable ratio, often bring hidden trouble to the odor. Therefore, the solvent problem is the focus problem of odor; it must be volatilized clean, which is related to the reasonable combination of solvent and drying temperature, machine speed, indoor temperature and humidity. The solution is to improve the fast drying ability of solvent, slow down the machine speed, increase the drying temperature, and relatively reduce the residual solvent. In dry compounding process, the residual solvent is mainly related to drying temperature, machine speed and diluent quality. Under normal conditions, the drying temperature is divided into three sections: 60 ° C in zone 1, 60-70 ° C in zone 2 and 70-80 ° C in zone 3; compound room temperature is 21-23 ° C and relative humidity is 65%. According to the structure and temperature control of the compound machine, we must adopt the method of shaving growth to dry from low to high; now the compound machine is changed from the original "one" shape to the "arch" type, which aims to make the solvent volatile more thoroughly. This is a good form of expression;
5. Odor caused by other reasons. In addition to the main factors causing odor, other factors can not be ignored, such as the residue of unreacted and side reactants in the polymerization process of plastics, the odor produced by the reaction products of additives and plastic materials, and the odor caused by radiation irradiation.
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
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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
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