Liquor, whether it's history or culture, goes back to ancient times. Since ancient times, the packaging of liquor cannot be separated from containers such as ceramics, glass, and clay jars. They have little permeability. Good sealing. Strong corrosion resistance, long-term storage of white wine can not be deteriorating, but there are some insurmountable disadvantages. The first is the impatience of impact, and it is fragile. The second is the inconvenience of carrying. The main reason is that the shape is very bulky and only a few bottles occupy a lot of space. This also results in the increase of the storage and transportation costs; the bottle price Higher, it becomes a burden after use. In recent years, plastic bottled liquor has also appeared on the market. It overcomes the problem of glass bottles being easily broken and having a small capacity-to-weight ratio, but it cannot overcome the problem of small capacity and volume ratio. And its sealability is inferior to glass bottles. The use of a composite flexible packaging bag as a white wine packaging solves the problem of small volume and volume ratio of bottled spirits on the premise of ensuring the sealing performance. Therefore, although bottled spirits are still the mainstream in the market, the use of plastic flexible packaging to print bags of liquor has gradually shown its vibrant vitality .
Plastic flexible packaging printing bagged liquor has the following characteristics.
(1) Strong barrier property and good fragrance protection effect. As long as you choose the right substrate, you can be airtight, impervious to moisture, opaque, and solvent-impermeable.
(2) It is easy to carry, it is not easy to break, and it is even tougher than plastic bottles. It does not break when it is squeezed, hit or dropped.
(3) Low cost.
(4) beautiful appearance. Easy to use, its shape, specifications and structural design can be diversified. According to people's needs, we can design a series of packaging, such as one, two, twenty-two, half a catty, etc., which is more convenient to use.
Based on the above advantages of white wine plastic flexible packaging printing bags, soft packaged white wine will be gradually promoted in the market, and the development of soft liquor packaging bags has a broad market prospect.
The main component of liquor is ethanol, which is extremely corrosive and permeable. It can cause damage to the composite package and result in delamination of the composite film, which in turn leads to the loss of the scent and the decrease in wine concentration. Liquor deterioration and so on. Therefore, the composite material with strong barrier property is selected when printing flexible soft packs for liquor. Adhesives, inks, etc. are very important.
First, the choice of composite substrate
1. Outer material selection (print layer)
In order to improve the barrier property of soft liquor packaging bags, BOPET, BOPA or KPET, KPA, and other materials are recommended as surface printing layers to improve barrier properties and prevent fragrance emission. After PVDC coating material is stored for a long time, the color will turn yellow. Therefore, PVDC coating materials are generally less used for packages with higher appearance quality requirements.
2. Inner material selection (heat seal layer)
The heat-seal layer of plastic flexible packaging is usually PE film and CPP film. Flexible packaged liquor is usually packaged with automatic packaging machine, which puts higher requirements on the material of the heat seal layer. First, the heat seal layer material must have good heat sealability (heat seal strength, low temperature heat sealability, anti-pollution heat sealability, heat seal temperature range, and hot tack strength, etc.); secondly, good suitability; and finally, Must have a good automatic packaging film removal, which means that the material's thermal cover finish must meet the requirements of the automatic packaging machine, with an appropriate friction coefficient (surface friction coefficient can be from the resin opening agent, the type and content of the lubricant On the choice).
(1) Good heat seal strength and heat seal range
Compared with CPP film, PE film has the advantages of wide heat sealing range, low heat sealing temperature, and soft texture. CPP film is generally more brittle and has a higher heat sealing temperature, especially for thicker CPP film.
That's it. Therefore, for the use of automatic packaging of liquor bags. It is more appropriate to choose PE film than CPP film.
(2) Anti-pollution and low temperature heat sealability
When the ordinary PE film is used for packaging white wine, the heat sealing conditions are more severe and the bag leakage rate is higher. Therefore, in order to ensure good heat sealing during the packaging process, modified polyethylene such as mPE must be selected. mPE has higher anti-pollution and heat sealability than ordinary PE, is less affected by white wine pollution, has higher tensile strength, and has high toughness and high transparency. It is a better choice to use mPE as the heat seal layer.
(3) Complex suitability and automatic packaging suitability
In order to meet the requirements of automatic packaging, a co-extrusion method is generally used to produce a polyethylene film so that the composite layer has a low slipperiness to ensure a higher composite strength; at the same time, the heat seal layer has a high smoothness so that Get a low coefficient of friction (usually required around 0.2) to ensure a good automatic packaging film removal.
The heat seal layer of the composite film uses a multi-layer co-extruded composite film, which can take into account its complex suitability, heat sealability, and automatic package adaptability while reducing production costs.
For example, a single proportion of metallocene linear low density polyethylene (mLLDPE) is currently used in the market to modify a single-layer heat-sealable substrate to improve the heat-sealability and physical properties of the composite, but per ton. The cost of heat-sealable substrates will increase more. To achieve the same performance as a single-layer modified heat-sealable substrate, if a multi-layer co-extruded composite substrate is used, the cost per ton of material will increase much less. The reason is that the multi-layer co-extruded composite substrate is modified by only blending on one of the heat seal layers, and a lower cost resin can also be used in the intermediate layer.
For another example, the packaging resins all contain a certain amount of an opening agent, a slip agent, etc. to improve the processability and increase the slipperiness of the film surface, but after these additives migrate to the film surface, they react with the binder chemically or physically. , causing a decrease in composite strength. This is also the confusion that many manufacturers often encounter. To solve this problem, in addition to allowing binder manufacturers to continuously improve the adhesive's ability to resist additives, the choice of multilayer co-extrusion heat-sealing substrates is a more economical and convenient method. That is, in the composite surface of a multilayer co-extruded heat-sealable substrate, a resin containing no or less opening agent and a slip agent is used to minimize the precipitation of surface additives of the composite layer, and a high-slip resin is selected at the heat-seal level. To ensure that the film has enough slippery.
Second, printing ink
Ordinary gravure printing inks are not problematic for printing dry food packaging and printing on ordinary BOPP film, but soft packaging printing for white wine will be due to the permeability of white wine and the affinity between common ink and PET film or BOPA film. Poor compatibility results in corrosion of the ink layer. Therefore, soft liquor packaging must be printed with special inks that are compatible with the substrate to improve the adhesion of the ink.
三ã€Adhesive
The choice of composite adhesives is also critical when making composite bags for liquor. Under normal circumstances, the adhesives we use are polyurethane adhesives, and the performance of polyurethane adhesives produced by different manufacturers or different types of polyurethane adhesives is quite different. The adhesive used in the flexible packaging of liquor must have strong resistance to media, which can block the penetration of alcohol and avoid lamination of the composite film.
Four, composite structure and process conditions
The surface of the composite packaging material used for packaging white spirits must be clean, and the surface wetting tension should be high; the dry base coating amount of the binder should not be less than 4.0g/m2, the composite strength should reach 35N/15mm or more; the residual solvent amount should be less than 10mg/m2; After compounding, it should also be fully matured at 50-55°C for more than 48 hours.
Liquor packaging can use BOPET/mPE. Structures such as BOPA/mPE or BOPET/BOPA/mPE. Liquor with different alcohol content requires different packaging bags. In general, the lower the alcohol content, the lower the permeability and corrosiveness of the composite film, and the lower the requirement for the composite film; conversely, the higher the alcohol content, the higher the requirement for the composite film. Therefore, a reasonable composite film structure and production process route must be selected according to the composition and content of the liquor produced by the customer.
Fifth, physical experiment
What needs to be pointed out here is that physical experiments must be carried out before mass production of soft composite liquor. Of course, fully simulating natural conditions cannot be concluded until two or three years later. It is not entirely realistic and will lose business opportunities. In order to reach a conclusion as quickly as possible, a rapid method can be used to perform a physical experiment, ie, a storage experiment under high temperature and high humidity conditions. For example, if the plastic flexible packaging bagged liquor is stored at 60°C for 2 months, the bag will not be damaged. Not layered. There is no apparent change in the appearance quality (such as pitting, wrinkles, delamination, tunneling, bubbles, etc.), and it can be considered that it has a shelf life of almost two years under normal atmospheric temperature conditions.
(Author: JIANG Zhi painted Maping Dong)