Manufacture and application of the hottest and hig

With the rapid development of China's economy, the improvement of the pace of people's life and the rise of tourism, the requirements for the grade of convenience food are becoming higher and higher. From 1959, when soft cans were successfully studied in the United States to now, their output has increased year by year, and their varieties are also moving towards the track of multi magnetization. In order to ensure their shelf life, the requirements for the outer packaging of products are particularly strict, High temperature resistant cooking bag is the best packaging composite material for soft cans because of its long-lasting packaging, stable storage, anti bacteria, high-temperature sterilization and repair properties

the water absorption (water repellency) and moisture flow density (air permeability) of high temperature resistant cooking bags should meet the structure and material selection at the same time

in order to meet the performance requirements of cooking bags, the outer layer of its structure is made of high-strength polyester film, the middle layer is made of aluminum foil with shading and air tightness, and the inner layer is made of polypropylene film. There are two kinds of three-layer structure: pet/al/cpp/, ppet/pa/cpp, and pft/al/pa/cpp with four layer structure

1. Polyester film

polyester film has the properties of high institutional strength, heat resistance, cold resistance, drug resistance, gas resistance and so on. Its thickness is 12gm, which can be used. However, many domestic polyester films have slightly poor temperature resistance, and the flatness of products is not very stable, which brings great difficulties to operation and waste

2. Aluminum foil

aluminum foil has excellent gas resistance and moisture resistance, so it is very important to preserve the original flavor of food. Strong protection, so that the packaging is not vulnerable to bacteria and mold; The shape is stable at high temperature and low temperature; Good shading, strong reflection energy to heat and light, 20 light aggregate concrete force. It can be used when its thickness is 7. The pinhole is as few as possible, and the aperture is as small as possible. In addition, its flatness must be very good, and the surface must be free of oil spots. Domestic aluminum foil generally cannot meet the requirements. Many manufacturers choose Korean and Japanese products

3. Nylon

nylon is not only good at separation, but also odorless, tasteless, non-toxic, and especially resistant to puncture. Its weakness is that it is not resistant to humidity. Therefore, it should be stored in a dry environment. Once it absorbs water, its performance indicators will decline. It can be used when the thickness of nyou is 15gm. In the process of compounding, it is best to use a double-sided film. If it is not a double-sided film, its untreated surface should be compounded with aluminum foil, To ensure the composite fastness

4. Polypropylene

polypropylene film, the inner layer of high-temperature cooking bag, not only requires good flatness, but also has strict requirements on its tensile strength, heat sealing strength, impact strength and elongation at break. Only a few domestic products can be used, but the effect is not as good as imported raw materials. Its thickness is GM, and the surface treatment duty is more than 40dyn

5. Adhesive

the whole adhesive of cooking bags requires strong adhesion fastness, and must be able to withstand high temperature of ℃. Its glue amount is the dry weight of g/m2. Many domestic composite plants use ad502 and 503H

II. Production process

1. Machine maintenance before production

before starting production, the machine must be thoroughly maintained. All rollers must have a smooth surface, free of adhesives and other sundries, and the second light is flexible in local motion; It is better to replace the composite rubber roller and the upper adhesive pressing roller with new spare parts, and adjust each roller in parallel

2. Process parameters

during production, if the quality of aluminum foil is good, it should be less than the guide roll as far as possible, and other base materials should be kept flat before entering the composite roll through tension and hand support fine-tuning devices. The humidity of the environment is kept above 85%, the compound drying humidity is 50 ℃, 70 ℃, 85 ℃, the compound temperature is, and the compound pressure is 0 5MPa, the machine speed is generally m/min under the condition of ensuring drying

3. Ripening

after each time of compounding, it is necessary to keep it in the ripening room above 40 degrees for 48 hours, and then carry out the next compounding. The final finished product needs to be ripened for 4 hours before it can be made into bags, but it is also not allowed to ripen for too long, otherwise the bonding fastness will decline

III. bag making

the bag making process is related to the heat sealing temperature, heat sealing pressure and machine speed. The heat sealing temperature is determined by the thickness of the composite film and the performance of the inner material. It is generally controlled between degrees. The pressure should be adjusted appropriately. If the pressure is too low, the sealing degree is not high. If the pressure is too high, the inner resin will be squeezed out, reducing the thickness of the seal and affecting the strength of the bag. In high temperature sterilization, it is easy to produce stress concentration at the heat seal and rupture the bag, The machine speed should not be too fast, otherwise the strength of the bag will also be reduced

IV. performance index of high temperature resistant cooking bags

when the bags are produced, the first batch should be sampled and checked, and the performance should meet the index before use

v. high temperature sterilization process

although each batch of processed products is qualified in the factory inspection, if the application process is unreasonable, it will also produce bag breakage, which will affect the reputation of the manufacturer. Therefore, the manufacturer should also master the sterilization process in order to find out the cause of bag breakage. At present, the domestic high-temperature sterilization process mostly adopts 121 degrees, min. if the air pressure rises or falls, it should be adjusted by injecting or releasing steam, but the pressure must be stable and must not fluctuate. (1) Select the research object: confirm the object under force analysis, then inject cold air, release water vapor while the pressure is still stable, stop after 5min, and finally put cold water for cooling to complete the sterilization process. During this period, if the pressure fluctuation is large, the bag will be seriously broken

information source: Fujian packaging printing brush, the first issue of 2005