With the increasing demand for leisure food, how to produce flavor food with pure flavor, longer storage time and more convenient storage and carrying is a problem considered by the R & D Department of each food factory. With the development of high-temperature cooking soft packaging, food research and development has also been brought to a new field. The most obvious is that the high-temperature cooking packaging containing aluminum foil is used more and more widely. However, from the current high-temperature cooking packaging production situation, there are many quality problems in aluminum foil packaging. How to improve the production level of aluminum foil packaging bags through various links control is the problem that the author wants to discuss with you today.
Material selection
How to choose the composite material reasonably is the key step of packaging. At present, the cooking temperature in the market is above 121 ℃ (inclusive). The high temperature cooking packaging containing aluminum foil mainly has the following two material structures, namely BOPET / Al / rcpp and BOPET / Al / BOPA / rcpp. The following author focuses on the analysis of these two structures, and to discuss with you, hoping to do a good job in this kind of packaging.
BOPET is a kind of high-grade plastic film with excellent properties, which is produced by biaxial stretching with PET chips as raw materials. It has high transparency, non-toxic and tasteless, high tensile strength, good stiffness, tear resistance, non-destructive, excellent electrical and optical properties, good oxygen resistance, moisture resistance, cold resistance (- 70 ℃), heat resistance (200 ℃), and chemical corrosion resistance And good properties of stable shrinkage. When selecting BOPET, the heat shrinkage should be less than 2% in longitudinal direction and 1.5% in transverse direction at 150 ℃ for 30 min, and the surface tension should not be less than 45MN / m.
Aluminum foil is the only metal foil in flexible packaging materials, which has a long application time in packaging field. Aluminum foil is a kind of metal material. Its water resistance, gas resistance, light shielding and taste retention are difficult to be achieved by any other packaging materials, and they can not be completely replaced. Aluminum foil is made of electrolytic aluminum with 99.0% ~ 99.97% purity after multiple calendering. It is rich in resources and has considerable advantages in performance price ratio. The aluminum foil for cooking packaging should be grade a soft aluminum foil with thickness of 9 μ M.
BOPA film has high puncture resistance, impact strength, friction strength and bending strength, and has good barrier property. When we use BOPA film, we should pay attention to the characteristics that it is easily affected by moisture and water absorption deformation. As the material of the intermediate layer, double-sided corona treatment is required, and the surface tension is not less than 50Mn / m. some customers use BOPA with single side treatment for lamination. The strength of the composite will be much lower, and increasing the amount of glue on the non treated surface will make up for it.
The characteristics of rcpp film are transparency, good flatness, good temperature resistance, certain stiffness, flexibility, and good heat sealing property. When making rcpp with aluminum foil packaging, attention should be paid to the heat shrinkage rate not to be too large, and the selection should take into account the different contents and have certain pertinence, especially when making some materials containing grease and acid and alkali 。 It is suggested that the thickness of cooking CPP should not be less than 80 microns, and the supplier with good physical control should be selected. For the special requirements of the contents, the corresponding products should be selected.
Special attention should be paid to the selection of ink for cooking and packaging. The double liquid polyurethane ink with good temperature resistance must be added with curing agent. Otherwise, the free hydroxyl in the ink will consume part of the curing agent, resulting in insufficient curing agent and main agent reaction, so that the adhesive layer can not be completely cured. After cooking, the peeling strength is low and the adhesive layer is back sticky; when it is serious, the ink layer and aluminum foil layer will appear, which will affect the appearance and barrier performance of the packaging.

The use of adhesives will be described in the next section.

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In the production of cooking and packaging, the most critical process control is in the composite process. Every detail of the composite process will determine whether the packaging performance reaches the expected goal. Therefore, in the production, we should strengthen the control of the composite process and master several key control points. Then, it is much easier to do this kind of packaging.
The right adhesive should be selected in the production of cooking packaging. For an adhesive, we should not only consider its temperature resistance, but also consider whether it has a great impact on the next process, whether there is a certain bearing capacity for the substances that may permeate out of the package, whether the peel strength after cooking is decreased or increased, and so on. The results showed that yh502s of GAOMENG could be used for sterilization at 121 ℃ for 40 minutes, and yh502 and yh3166 could be used for sterilization at 135 ℃ for 30 minutes. Moreover, these adhesives have good wettability and coating property to the film. For BOPA, pet, CPP and aluminum foil materials, they have high initial adhesion force and excellent composite strength. The heat resistance and chemical resistance of the adhesive layer are very good. The strength will increase after cooking, which makes the shelf life of cooked products long and the goods can be stored for a long time.
After choosing the glue, we need to configure it. I want to emphasize a problem when mixing glue. The moisture in ethyl ester will consume the effective components of curing agent, resulting in insufficient curing agent in glue liquid, incomplete reaction of adhesive layer, and low final peeling strength. Therefore, we must control the moisture content of ethyl ester below 300ppm. Due to the coming of summer, the air humidity is increasing, so higher requirements are put forward for the transportation and storage of ethyl ester we use. The water content of the ethyl ester entering the factory should be tested. The ethyl ester exceeding the standard should not be used. If possible, silica gel can be used for dehydration. Otherwise, the ethyl ester that can meet the standard should be replaced and reused. If it is difficult to purchase, the curing dosage can be increased by 10% ~ 15% to ensure enough curing agent and main agent reaction. If the ethyl ester entering the factory is placed in a large tank, a drying device shall be added to the breathing valve of the tank body to filter the air supplied; if the barrel solvent is used, the barrel shall be covered in time after taking out to prevent the ethyl ester from being exposed to the air for a long time and absorbing the water vapor in the air, thus affecting the quality of the glue solution.
The problem of glue quantity is always emphasized by us. Only when there is enough glue, can we have enough bonding strength to cope with the change of process conditions and external conditions. In view of these two structures, the author suggests that the glue amount of PET / Al layer should not be less than 3.5g/m2, and the glue amount of products with larger printing ink area should be increased; the glue amount of other layers should be higher than 4G / m2. At present, the wire roller of most manufacturers is embossed wire roller, which is not ideal for the transfer and leveling of glue liquid. If possible, laser etching roller should be selected to ensure the glue loading amount of large-scale production of composite products. In the case of insufficient glue, the cooking temperature and time of the bag may be reduced, resulting in the decrease of shelf life. We must avoid this kind of situation. Smooth roller is required in the process of lamination, which can assist the rubber layer to complete leveling better. The rotation direction of the smoothing roller should be opposite to that of the film.

Solvent residue is a very important control point in food packaging. Due to people's more and more strict requirements for food safety, the state has also increased the control of solvent residues. In the composite process, we need to increase the drying capacity of the equipment to maximize the volatilization of ethyl ester in the rubber layer. How can the equipment be dried? The products of various equipment manufacturers are different, and there is no mandatory requirement for this in China. If customers need to know the drying performance of the equipment, they can contact the customer service department of GAOMENG. We will evaluate the equipment together with you and provide corresponding rectification suggestions.
The temperature and curing time of curing chamber will affect the final strength of the bag. Take yh3166 as an example (see the figure below), under the condition of curing at 50 ℃, 74% of the reaction is completed in 72 hours and 86% in 96 hours. Therefore, the temperature and time of curing chamber will determine the final rate of reaction and determine the final composite fastness. The author suggests that the independent curing chamber should be used to hang the coiled material for curing when the conditions permit, and there should be appropriate air circulation in the room to ensure that the inner and outer layers are heated evenly. The room temperature of curing room is required to be measured at 55 ℃± 5 ℃, and the curing time shall not be less than 72 hours. Some products shall be cured for more than 96 hours. After leaving the curing room, bags shall not be made immediately, but shall be fully cooled before bag making.
high-temperature sterilization
In high temperature disinfection, the choice of disinfection equipment is the key. The most basic requirements for the disinfection equipment are: automatic temperature control device, temperature detection probe at the upper, middle and lower parts of the pot; pressure maintaining setting for the inside of the pot; heating and cooling should be slow and uniform, and attention should be paid to the control of sterilization temperature and sterilization time. Disinfection should not exceed 40 minutes when cooking at 121 ℃ and 30 minutes at 135 ℃. Some food manufacturers use steam sterilization, steam directly blows on the bag bag, resulting in local high temperature. After disinfection, many products near the steam nozzle appear serious stratification phenomenon. In order to solve this problem, baffle should be installed at the steam nozzle to make the steam evenly sterilize the package in the sterilizer. In cooling, special attention should be paid to it. Generally, cold water is used for direct cooling. If the cold water is poured directly into the larger shear force, the adhesive force of the adhesive layer will be reduced. Therefore, water bath should be used to cool down the temperature to 40 ℃ slowly, and the pressure should be kept when cooling, otherwise the bag will be broken.
In short, the high temperature cooking packaging industry is still more concerned about the field, each has its own unique process control point, here the author is just a general introduction to the feelings, I hope you pay attention to the details of the production control, after the problem is found, to analyze the causes of the problem, formulate solutions, and have a clear record of the problem handling Record and establish files to avoid repeated quality problems next time.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service. 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 the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries. We uphold the integrity of cooperation, good quality, good service business philosophy, won the industry's approval, products sold to all over the world; welcome friends from all walks of life to inquire, visit our factory to investigate guidance and business negotiations.