With the development of my country’s economy, the prosperity of tourism and the rise of the Golden Week economy, people’s demand for convenience food is increasing. All kinds of soft canned and high-temperature cooking foods are not only diverse but also huge in quantity. A large number of food packaging products with high barrier properties, high impact resistance, high temperature cooking resistance, high pressure resistance and medium resistance emerge as the times require, thus ensuring the convenience of food. The freshness and nutrition extend the shelf life of convenience food, and it is the best packaging material for soft cans.
High-temperature cooking can kill all bacteria (135°C), and has a long shelf life. The high-barrier transparent bag has a shelf life of about one year, and the aluminum foil cooking bag has a shelf life of about two years; oxygen permeability and moisture permeability are close to zero. Food is not prone to spoilage; heat intensity is high; it can be stored at room temperature.
The main raw materials are: PET (mainly B0PET), PA (mainly BOPA), PP (mainly RCPP and SCPP), AL (mainly aluminum foil), co-extruded PA film, co-extruded EVOH film, PVDC Coating film, etc.
Classification of high temperature cooking bags
- Classification by structure
Class A: PA/CPP, PET/CPP. Water vapor permeability: ≤15g/(m·24h); Oxygen permeability: ≤120cm/(m2·24h·0.1HPa).
Class B: PA/AL/CPP, PET/AL/CPP. Water vapor permeability: ≤ 0.5g/(m 24h); oxygen permeability: ≤ 0.5cm/(m 24h 0.1MPa).
Category C: PET/PA/AL/CPP, PET/AL/PA/CPP. Water vapor permeability: ≤0.5g/(m 24h); oxygen permeability: ≤0.5cm/(m 24h 0.1MPa).
- Classification by cooking temperature (cooking time is about 30-45 minutes)
When the relative pressure is PS110 psi, the corresponding temperature is l15cC; the shelf life is about 3 months.
When the relative pressure is Ps 115 psi, the corresponding temperature is 121cC; the shelf life is about 6 months.
When the relative pressure is PS120 psi, the corresponding temperature is 126cC; the shelf life is about 12 months (transparent bag).
When the relative pressure is PS130 psi, the corresponding temperature is 135cC; the shelf life is about 24 months (aluminum foil bag).
Of course, the shelf life is also closely related to the barrier properties of the retort bag and the type of food.
Characteristics of medium temperature cooking CPP (RCPP) and high temperature cooking CPP (SCPP)
The main features of cooking grade CPP film are: good flatness; high tensile strength; high heat sealing strength; high heat sealing temperature (requires high heat sealing strength under high temperature and high pressure during cooking); high impact strength (requires Resistance to puncture and bag breaking under high temperature and high pressure during cooking); moderate elongation at break; good medium resistance, etc.
The main raw material of cooking grade CPP film is block copolymerized impact-resistant polypropylene. The performance requirements are: the Vicat softening point temperature should be higher than the cooking temperature; the haze should be as small as possible (because the haze of block copolymerization is relatively large); the impact resistance is better; And less.
The production of block copolymerized impact-resistant polypropylene is difficult, and it is difficult to develop the market, so there are very few domestically produced, basically imported raw materials. Due to the relatively high technical requirements and cost of film-grade block copolymerization impact-resistant polypropylene raw materials, some domestic manufacturers are trying to use high heat-sealing temperature two-component heat-sealing polypropylene materials and injection-grade block copolymerization impact-resistant polypropylene materials instead. Film grade block copolymer impact polypropylene raw material.
When using a two-component heat-sealing polypropylene material with a high heat-sealing temperature, there is no problem with the heat-sealing temperature and heat strength, the haze is also very good, and there are few fish eyes and crystal points, but the tensile strength, impact resistance, medium resistance The performance indicators such as properties and elongation at break may be a little worse.
When using injection-grade block copolymer impact-resistant polypropylene material, the impact resistance, medium resistance and other indicators are acceptable, but there are many fish eyes and crystal points, and the tensile strength, elongation at break, haze and other performance indicators may be required. Almost.
High temperature cooking ink
The first is the selection of the ink binder (to ensure the stability of the binder at high temperature cooking temperature); the second is the selection of ink colorants (to ensure the color stability of the colorant at high temperature cooking temperature); the third is the ink Selection of curing agent (pay attention to the selection of curing agent when using two-component ink).
Pay attention to the difference: ordinary retort-resistant ink; high-temperature retort-resistant ink; ultra-high-temperature retort-resistant ink. Also pay attention to the problem of ink color change, the problem of adding a curing agent when the two-component residual ink is mixed with the new ink, and the problem that the scratching property is reduced when the curing agent is too much.
High temperature cooking glue
High temperature resistant retort bags should be retorted and sterilized at high temperature, and should be retortable adhesives with high temperature of 121cc and ultra-high temperature of 135cc. Never use ordinary adhesives. Ordinary adhesives are not temperature-resistant, and the composite film bag will usually delaminate when it is less than 80L°C. Peel strength is extremely low. High temperature retort adhesive for treated PET, polyolefin, aluminum foil, aluminized foil, PVDC coating and treated extruded hot film, etc., should have good adhesion, as well as excellent retort and chemical resistance Aggressive.
The main components of general two-component polyurethane adhesives are: a mixture of polyester polyols (polyester polyurethane) and modified isocyanate adducts (polyisocyanate). In use, attention should be paid to ensure the dry coating amount, the solvent residue should be as little as possible, and the curing should be sufficient.
If the amount of curing agent is too small, the degree of crosslinking between the curing agent and the resin will be low, and the adhesion strength, heat resistance and hydrolysis resistance of the ink layer will be reduced; Intermolecular crystallization and microscopic phase separation, the cohesion of the adhesive layer increases, and the ink layer shrinks excessively, causing delamination. If the curing time is not enough, the cross-linking is not enough, the ink layer is warm and the hydrolysis is reduced; if the curing time is too long or the curing temperature is too high, it will be excessively glued and the peel strength will decrease. For mass-produced retort bags, the retort performance should be confirmed before use.
New high-barrier cooking film
With the successive production of seven-layer co-extrusion cast film production lines, seven-layer and nine-layer blown film production lines, and various high-barrier film production lines, the raw materials for the production of new high-barrier retort pouches are more abundant. The five-layer co-extruded film mainly includes: PP/AC/EVOH/AC/PP or PE/AC/EVOH/AC/PE. Seven-layer co-extruded film mainly includes: PP/AC/PA/EVOH/PA/AC/PP or PE/AC/PA/EVOH/AC/PA/PE.
High barrier composite substrates include: B0EVOH or C—EVOH, PVDC/B0EV0H/PVDC(K-EVOH), PVDC/BOPVA/PVDC(K-pVA), PVDC/BOPA/PVDC(K PA), PVDC/BOPET/PVDC (K-PET), PVDC (copolymer blown film), etc.
The use of these new packaging materials not only greatly prolongs the shelf life of food, maintains the freshness and nutrition of food to the greatest extent, but also reduces the phenomenon of bag breakage during vacuuming, high pressure and pressure fluctuation to a considerable extent. To a certain extent, the cost has been reduced, and the packaging of high-end convenience food has been popularized.