CPP High Temperature Retort Film
With the development of China's economy, the prosperity of tourism and the rise of Golden Week economy, people's demand for convenient food is growing. All kinds of soft cans and high temperature retort food are not only diversified but also in large quantities. A lot of food packaging products with high barrier, high impact resistance, high temperature retort resistance, high pressure resistance and medium resistance emerge at the moment, thus ensuring the freshness and nutrition of convenient food, extending the shelf life of convenient food, and being the best packaging material for soft cans.
High temperature retort can kill all bacteria (135 ° C), the products have a long shelf life, for the high barrier transparent bag, the shelf life is about one year, and for the aluminum foil retort bag, the shelf life is about two years. Oxygen and moisture permeability are close to zero, and food is not easy to deteriorate; With high heat strength and can be stored at room temperature.
Its raw materials mainly include: PET (mainly B0PET), PA (mainly B0PA), PP (mainly RCPP and SCPP), AL (mainly aluminum foil), co-extrusion PA film, co-extrusion EV0H film, PVDC Coating film, etc.
Classification of High Temperature Retort Bags
1、Classification by structure
Class A: PA/CPP, PET/CPP. Water vapor transmission volume: ≤ 15g ／ (m • 24h); Oxygen transmission volume: ≤ 120cm ／ (m2 • 24h • 0.1HPa).
Class B: PA/AL/CPP, PET/AL/CPP. Water vapor transmission volume: ≤ 0.5g ／ (m • 24h); Oxygen transmission volume: ≤ 0.5cm ／ (m • 24h • 0.1MPa).
Class C: PET/PA/AL/CPP, PET/AL/PA/CPP. Water vapor transmission volume: ≤ 0.5g ／ (m • 24h); Oxygen transmission volume: ≤ 0.5cm ／ (m • 24h • 0.1MPa).
2、Classification by retort temperature (retort time is about 30-45 minutes)
When the relative pressure is PS110 lb/in, the corresponding temperature is l15cC; The shelf life is about 3 months.
When the relative pressure is Ps115 lb/in, the corresponding temperature is 121cC; The shelf life is about 6 months.
When the relative pressure is PS120 lb/in, the corresponding temperature is 126cC; The shelf life is about 12 months (transparent bag).
When the relative pressure is PS130 lb/in, the corresponding temperature is 135cC; The shelf life is about 24 months (aluminum foil bag).
The shelf life also has a great association with the barrier of the retort bag and the type of food.
Characteristics of Medium-temperature Retort CPP (RCPP) and High-temperature Retort CPP (SCPP)
The main features of Retort CPP Film are good flatness, high tensile strength, high heat-sealing strength, high heat-sealing temperature (it is required to ensure high heat-sealing strength under high temperature and pressure during retort), high impact resistance (it is required to have puncture resistance and package breaking resistance under high temperature and pressure during retort), elongation at break is moderate, good medium resistance, etc.
The main raw material of Retort CPP Film is block copolymerized impact resistant polypropylene. The performance requirements are: Vicat softening point temperature should be greater than retort temperature; The haze shall be as small as possible (because the haze of block copolymerization is relatively large); Good impact resistance; Good dielectric resistance; Fish eyes and crystal points should be as few as possible.
The production of block copolymer impact resistant polypropylene and the market development is difficult, so there are few domestic products, and they are basically imported raw materials. Due to the high technical requirements and costs of the film block copolymer impact resistant polypropylene raw materials, some domestic manufacturers are trying to use binary heat sealable polypropylene materials with high heat-sealing temperature and injection moulding block copolymer impact resistant polypropylene materials to replace the film block copolymer impact resistant polypropylene raw materials.
When using the two-component heat sealable polypropylene material with high heat-sealing temperature, the heat-sealing temperature and heat strength are no problem, the haze is also very good, the fish eyes and crystal points are few, but the tensile strength, impact resistance, medium resistance, elongation at break and other performance indicators may be poor.
When using injection moulding block copolymer impact resistant polypropylene, the impact resistance, medium resistance and other indicators are acceptable, but the tensile strength, elongation at break, haze and other performance indicators may be poor due to more fish eyes and crystal points.
High Temperature Retort Resistant Ink
First, the selection of ink binders (to ensure the stability of binders under the temperature of high temperature retort ); The second is the selection of ink colorants (to ensure the color stability of colorants under high temperature retort); The third is the selection of ink curing agent (pay attention to the selection of curing agent when using two-component ink).
Pay attention to the difference: normal retort resistant ink; High temperature retort resistant ink; Super high temperature retort resistant ink. Also pay attention to the problem of ink color conversion, the problem of adding new curing agent when the two-component residual ink is mixed with new ink, and the problem of inch scratch reduction when the curing agent is excessive.
High Temperature Retort Resistant Adhesive
High temperature retort resistant bags should be sterilized by high temperature retort. High temperature resistant 121cc and ultra-high temperature resistant 135cc retort adhesives should be selected. Normal adhesives must not be used,because normal adhesives are not temperature resistant. Lamination film bags usually delaminate when the temperature is less than 80L ℃, and the peel strength is extremely low. High temperature retort resistant adhesive shall have good adhesion to treated PET, polyolefin, aluminum foil, Metallised foil, PVDC coating, as well as excellent retort resistance and chemical medium resistance.
Generally, the main components of two-component polyurethane adhesive are: mixture of polyester polyols (polyester polyurethane), modifier isocyanate adduct (polyisocyanate). During using, pay attention to ensure the dry coating amount, minimize the solvent residue and fully maturing.
If the dosage of curing agent is too less, the degree of crosslinking between curing agent and resin is low, and the adhesion strength, heat resistance and hydrolysis resistance of the ink layer will be reduced; If it is too much, excessive crosslinking will occur, which will affect the separation of crystallization and microscopic phases between polymers, increase the cohesion of the adhesive layer, and cause excessive shrinkage of the ink layer, causing delamination. If the curing time is not enough, the crosslinking is not sufficient, the temperature resistance and hydrolysis resistance of the ink layer decreased; If the curing time is too long or the curing temperature is too high, excessive bonding will occur and the peel strength will decrease. For batch production of retort bags, the retort performance shall be confirmed before use.
New Type High Barrier Retort Film
With the 7-layer co-extrusion CPP film production line, 7-layer and 9-layer blown film production lines, and various high barrier film production lines start production, the raw materials for the production of new high barrier retort bags are more abundant. The 5-layer co-extrusion film mainly includes PP/AC/EV0H/AC/PP or PE/AC/EV0H/AC/PE. The 7-layer co-extrusion film mainly includes PP/AC/PA/EV0H/PA/AC/PP or PE/AC/PA/EV0H/AC/PA/PE.
High barrier lamination base film include: B0EV0H or C-EV0H, PVDC/B0EV0H/PVDC (K-EV0H), PVDC/B0PVA/PVDC (K-pVA), PVDC/BOPA/PVDC (K PA), PVDC/BOPET/PVDC (K-PET), PVDC (co-polymerization blown film), etc.
The use of these new packaging materials has not only greatly extended the shelf life of food, kept the food fresh and nutritious to the maximum extent, but also reduced the package broken phenomenon under vacuuming, high pressure and pressure fluctuation to a considerable extent, thus greatly reducing the cost and popularizing the packaging of high-grade convenient food.