What are composite packaging bags? Why use composite packaging bags?

What is Composite packaging bags ？Why use composite packaging bags? Shunxingyuan Packaging, a professional flexible packaging manufacturer, believes that improving the performance of existing plastic materials, enhancing the strength and barrier properties of materials, developing new types of materials, reducing material usage (thick walls), reusing materials, and classifying and recycling materials to protect the environment are the reasons why composite packaging bags are used.

Let's take a closer look!

 

 

New high-barrier plastics have been widely used

New high-barrier plastics not only enhance the packaging's protective function for food but also reduce the amount of plastic used, and can even enable material reuse. For processed foods requiring high-barrier protective packaging, and in applications such as vacuum packaging and gas packaging, we generally use composite material packaging, and in multilayer composite materials, one or more high-barrier materials must be used.

Commonly used high-barrier packaging materials include aluminum foil, nylon, and polyester. With the increasing demand for food packaging protection, materials with better barrier properties, such as ethylene-vinyl alcohol copolymers and polyvinyl alcohol, have also begun to be widely used. At present, developed countries have developed and applied PEN (polyethylene naphthalate) in small quantities, adding many advantages to food packaging materials. The chemical structure of PEN is similar to that of PET (polyethylene terephthalate), but its rigidity is greatly improved, and its oxygen barrier and water barrier properties are several times higher than those of PET materials. It also has good ultraviolet absorption and lower gas adsorption. In this way, containers used to hold food using PEN materials leave no odor and can be reused.

 

 

Inorganic high-barrier microwave food packaging materials will become a new favorite

With the acceleration of consumers' pace of life, food packaging that can be directly used for microwave heating will become a new hot spot in the food packaging field. Due to the disadvantages of packaging made of composite materials using aluminum foil and certain plastics, such as opacity, difficulty in recycling, and inability to be directly used in microwave ovens, the newly launched SiOx-coated material in recent years can be used as a good substitute. SiOx material is a thin layer of silicon oxide coated on PET, PA, PP and other substrates. It not only has superior barrier properties but also excellent atmospheric adaptability. The barrier properties of SiOx materials are hardly affected by changes in environmental humidity and temperature. SiOx coating has high barrier properties, high microwave permeability, and transparency. It can be used for flexible packaging of microwave-processed foods and can also be made into packaging containers for beverages and edible oils. SiOx materials have also begun to be applied in China. Although the cost of SiOx coating is high and large-scale commercial production technology is not yet perfect, due to its special properties, SiOx coating will become an important packaging material in this century.

The application of active packaging technology will become a trend

Active packaging technology refers to the interaction between the packaging, the gas inside the packaging, and the food, which can effectively maintain the nutrition and flavor of the food. Active packaging can mainly be applied to food packaging. Compared with the past physical methods of blocking gas, water vapor, and light, active packaging plays a positive and important role in extending the shelf life of food and can provide better protection for food. Therefore, active packaging, as an intelligent technology, is being widely developed and applied.

Due to advances in materials science, bioscience, and gas packaging technology, active packaging technology has developed rapidly in recent years, such as oxygen-absorbing active packaging and sterilization active packaging.

Sterilization active packaging is a complete system that combines active sterilizing substances with packaging materials. It refers to adding substances such as sorbitol, sorbate, sodium benzoate, and silver zeolite to the materials used to manufacture packaging containers, and then processing and forming the containers, which can slowly release sterilizing active ingredients.

Active packaging is considered a revolutionary change in the packaging industry. To control specific gases within the packaging, active packaging materials use chemicals that can absorb or release specific gases. The functional system of active packaging includes the use of bactericides, enzyme inhibitors, oxygen absorbers, odor absorbers or releasers, light blockers, antifogging agents, anti-sticking agents, stabilizers, etc. Other active packaging systems that have been or are about to be implemented include: antioxidant films, odor absorption and release systems, anti-bonding films, antifogging films, light-blocking and light-regulating components, etc.

 

 

 

 

 

 

 

 

Extrusion coating composite film: On an extruder, thermoplastic plastic is cast onto the paper, foil, or plastic substrate to be laminated through a T-die, or the extruded resin is used as an intermediate adhesive to press another film substrate together while hot, forming a "sandwich" composite film. To improve the composite strength, corona treatment is required, and an anchor coating agent is applied. The extrusion composite film can be reverse-printed, the thickness of each layer can be precisely controlled, the solvent residue is small, and the price is cheap.

The extrusion coating production line is designed according to the modular principle and can be combined with a single-station laminator or a multi-station laminator.

 

 

Single-layer or multi-layer polymer melt is processed in the extruder and applied to the substrate through a special seam die head. By guiding the polymer film on the cooling roller, the film is firmly adhered to the substrate and will not be separated by water, solvents, or high temperatures.

Co-extrusion composite film: Using two or three extruders, sharing a composite die head, laminating between several compatible thermoplastics to produce multi-layer films or sheets. Co-extruded composite films can only be printed on the front side and not on the reverse side. Compared with dry composite films and extrusion cast films, the thickness control of each layer is more difficult. No adhesives and anchor coating agents are used, and the hygiene is good. Co-extruded composite films have the lowest cost.

Extrusion composite process, also called sandwich composite process, is similar to extrusion coating process. However, in the extrusion composite process, the extrusion coating acts as an adhesive layer between two or more substrates. When the extrusion coating has not yet cooled, the second layer of substrate is laminated, and then this sandwich structure is compacted by a pressure roller.

Currently, extrusion lamination technology is only used in the production of composite films. Extrusion lamination is a method of melting and plasticizing thermoplastic resin by a plastic extruder, extruding it through a T-die to coat it on a substrate, simultaneously laminating and pressing it with another substrate, and cooling it to form a composite film. Extrusion coating is a process in which thermoplastic resin is continuously and uniformly extruded, directly cooled and wound on a substrate to form a composite film without bonding with another substrate. In practice, extrusion coating/coating is often classified as extrusion lamination.

1. Uses a small amount of adhesive, with very low or even no residual solvent

The extrusion lamination process is a method for manufacturing composite films by extruding adhesive resin from an extruder to laminate the materials to be compounded. It uses a small amount of AC agent and has very low or even no residual solvent. In terms of solvent residue control, extrusion lamination has an absolute advantage over dry lamination. It can ensure that the solvent residue of the composite film used for pharmaceutical packaging meets the requirements of pharmaceutical packaging. Taking PET/PE plastic-plastic structure as an example, extrusion lamination and dry lamination are used to complete the test, and the solvent residue is measured. The data in Table 1 shows the comparison of solvent residue between the two lamination methods.

 

Table 1: Comparison of solvent residue between dry lamination and extrusion lamination

2. Good hygiene performance

The extrusion-laminated heat-sealing layer is coated onto the substrate by an extruder after high-temperature heating in a GMP production environment, which ensures better hygiene performance of the product; while the heat-sealing PE layer of dry lamination or solvent-free lamination is a blown or cast PE film, most of which are not produced in a GMP clean environment, and there is a greater risk in terms of hygiene performance.

At the same time, because the coating-grade LDPE does not contain oxidants, lubricants, etc., using the LDPE film as the heat-sealing layer, whether it is migration or adsorption, is more hygienic than other materials in terms of compatibility with drugs, so it is more suitable for drug packaging.

3. The thickness of each layer of the composite film of extrusion coating can be freely adjusted and controlled

The thickness of the dry composite film is determined by the selected substrate and cannot be adjusted, especially for heat-sealing layers controlled below 30μm, blown films cannot meet the requirements.

The thickness of the extrusion lamination extrusion layer can be arbitrarily set between 12μm and 50μm. Through online automatic thickness measurement, the thickness change of the product is monitored in real time. By setting the thickness deviation range on the human-machine interface, when the exceeding phenomenon is detected, the alarm device can alarm in time, and the die gap can be adjusted online automatically on the human-machine interface to correct the thickness deviation, accurately control the thickness deviation, and print the detection data record to ensure the stability of product quality.

4. Different thermoplastic resins can be selected to produce composite materials with different functions

When producing composite films for pharmaceutical packaging, different heat-sealing resins should be selected according to different packaged products, different packaging machinery, and different packaging conditions (temperature, speed, etc.). For pharmaceutical packaging with poor heat resistance, low-temperature heat-sealing materials should be selected. For heavy packaging, heat-sealing materials with high heat-sealing strength, high mechanical strength, and good impact performance should be selected. For high-speed packaging machines, low-temperature heat-sealing and high heat-adhesive strength heat-sealing materials should be selected. For powders, liquids and other highly polluting pharmaceutical packaging, heat-sealing materials with good anti-pollution properties should be selected.

Using pure LDPE as the extrusion heat-sealing layer, the heat-sealing strength of extrusion lamination is about 20N/15mm, which is particularly suitable for packaging materials with a general content of 500g or less.

MLLDPE, IR and other heat-sealing resins are used for coating to improve the low-temperature heat-sealing performance, anti-pollution sealing performance, and heat-adhesive strength of the composite film, increase the speed of rapid packaging, ensure anti-pollution and sealing performance, and ensure the shelf life of the product.

Special resins can be selected for coating to produce easily peelable materials.

Taking PET/AL/PE as an example, different inner layer materials have different heat-sealing effects, as shown in the table below:

 

 

Experiments have shown that the addition of heat-sealing resin greatly reduces the low-temperature heat-sealing performance of extrusion-laminated products, and also makes its heat-sealing strength exceed that of general dry-laminated products.

5. The composite film has good tearability at the notch, which is convenient for patients to use

The right-angle tear strength of the composite film with LDPE coating as the heat-sealing layer is smaller than that of dry lamination, and the notch is easy to tear, showing good performance in terms of tearability of the product. At the same time, the tensile strength of the coated heat-sealing layer LDPE film is not as good as that of the blown film of the dry lamination heat-sealing layer. It has excellent cutting performance in automatic equipment packaging and rarely occurs that the blown PE composite film cannot be cut. This property is widely used in easy-tear product packaging.

 

 

High barrier film: a multi-layer film. This film can effectively prevent the penetration of oxygen and other gases, thereby preventing the growth of microorganisms; preventing the oxidation of the packaged items; preventing the leakage of the fragrance, solvent, etc. of the goods. Commonly known high-barrier high-strength materials, such as EVAL, PVDC, PET, PAN, selar PA, etc., are made into packaging films, which can significantly extend the shelf life of food, or can replace traditional rigid packaging materials with good barrier properties.

Ceramic film is a new type of barrier packaging film material that has emerged in recent years. The production process of ceramic film is similar to that of aluminum-plated film, and it also uses vacuum coating. At present, the ceramic films used in the packaging field mainly include SiO 2 (silicon dioxide), Al 2 O 3 (aluminum oxide), TiO 2 (titanium dioxide), etc. The biggest advantage of transparent barrier film over traditional aluminum-plated barrier film is that consumers can clearly see the goods themselves through the packaging material, and in the high-speed packaging process, the transparent barrier material will not cause any metal pollution to the packaged goods. Due to SiO 2 (silicon dioxide), Al 2 O 3 (aluminum trioxide), TiO 2 The melting point of (titanium dioxide) exceeds 1500℃, far exceeding that of aluminum (approximately 660℃). Producing ceramic films is therefore more difficult and requires specialized vacuum deposition equipment, which is a major reason for the high production cost of ceramic films. Generally, transparent barrier films cost 2-3 times more than traditional aluminum-coated barrier films. Reducing the production cost of existing equipment and processes is a current research focus. Numerous methods exist for preparing transparent barrier films; currently used production methods can be divided into the following five categories:

(1) Using induction thermal evaporation to heat silicon oxide materials to prepare silicon oxide film materials. This process is similar to traditional resistance evaporation vacuum aluminum coating equipment, the main difference being the use of an induction evaporation system instead of a resistance evaporation system; therefore, the equipment investment is similar to that of aluminum film. A 40kHz high-frequency induction coil heats the crucible, typically made of molybdenum or tungsten. Induction heating allows the crucible to reach temperatures above 2000-2500℃ with a uniform temperature field. This temperature easily evaporates SiO (silicon monoxide) material. Adding a mass flow system to introduce an appropriate amount of oxygen into the chamber avoids color differences in the silicon oxide film layer. The final ceramic film composition is SiOx, where 2>x>1, indicating that the film layer has certain oxygen defects. Some methods use ordinary 25-micron-thick OPP material as the substrate for preparing silicon oxide films; the resulting silicon oxide ceramic film has a barrier rate of 0.1 g/m²·day. The biggest drawback of this method is that the evaporation material used is SiO (silicon monoxide), which is expensive, directly resulting in a high unit price for the produced silicon oxide ceramic film. High-barrier packaging films prepared using SiO (silicon monoxide) coatings can also achieve an oxygen barrier capacity of 0.1 g/m²·day and have good steam sterilization resistance.

(2) Adding a mass flow meter gas supply system and a plasma treatment system to existing thermal evaporation aluminum coating equipment can also be used to produce transparent aluminum oxide ceramic barrier films. This process uses oxygen plasma to strongly oxidize the aluminum metal coating to form an aluminum oxide film, converting the opaque aluminum metal coating into a transparent aluminum oxide coating. Barrier films produced in this way can reach 0.1 g/m²·day, and the equipment investment is slightly higher than that of existing vacuum aluminum coating machines; the obvious drawback is that Al 2 O 3 material is easily hydrolyzed, so the steam sterilization resistance of this transparent barrier film is poor.

(3) Using electron beam heating to heat the material to be evaporated. This equipment is similar in structure to thermal evaporation aluminum coating equipment; the main difference is that an electron beam evaporation unit replaces the resistance evaporation unit, and the vacuum system requires a higher base vacuum. Because the electron beam heating temperature can reach over 3000℃, common ceramic materials can be evaporated and coated, such as SiO (silicon oxide), Al 2 O 3 (aluminum oxide), TiO 2 (titanium dioxide), etc. The biggest drawback is that the electron beam evaporation unit is very expensive, resulting in high equipment and maintenance costs for this process. Therefore, the unit cost of ceramic films produced by this process is high. An electron beam evaporation device with the same coating width is more than three times the price of an ordinary resistance thermal evaporation aluminum coating machine.

(4) Using roll-to-roll chemical vapor deposition to prepare transparent barrier films. Relatively inexpensive organic gases containing Si elements, oxygen, and inert gases are introduced into a vacuum chamber through a mass flow system in a certain distribution pattern. Under normal conditions, the various components of the mixed gas can stably coexist. After entering the vacuum chamber, medium-frequency or radio-frequency plasma activates the mixed gas, generating SiOx and depositing it on the coating substrate. The remaining reactants are removed as gas by the vacuum system. Currently, organic gases containing Si elements are mainly HMDSO (hexamethyldisiloxane) and TMSO (tetramethyldisiloxane). Barrier films prepared using this method perform well, reaching 0.1-0.01 g/m²·day, and have good steam sterilization resistance. Compared to ordinary vacuum aluminum coating machines, the equipment cost is higher, but lower than that of electron beam evaporation equipment. Moreover, the silicon-containing raw materials used are much cheaper than SiO evaporation materials. The biggest drawback of this process is the slow coating line speed, resulting in a high unit product cost. Increasing the number of coating stations can effectively improve production efficiency, but this will also lead to increased equipment complexity and cost.

(5) Roll-to-roll magnetron sputtering coating. Usually, medium-frequency magnetron sputtering is used for reactive sputtering to prepare SiOx films, Al 2 O 3 films or Al:ZnO films. This method produces transparent barrier films with excellent performance, reaching 0.01 g/m²·day or even better. The drawbacks are high equipment investment and slow production speed, resulting in a high unit product price. Therefore, this method is mainly used to produce ultra-high barrier films, mainly for the barrier packaging of OLEDs and thin-film solar cells, and is rarely used in the ordinary packaging film market.

Preservation and sterilization films: The following types exist:

① Ethylene gas adsorption film: Adding zeolite, olivine, silicon dioxide, etc., to the film can absorb ethylene gas exhaled by fruits and vegetables, inhibiting their rapid ripening.

② Anti-condensation and anti-fog film: The inner surface of the packaging film for many hydro-fruits often condenses and fogs, easily causing food spoilage. Adding anti-fogging agents such as monoglyceride stearate, polyol ester fatty acid derivatives, and sorbitan stearate, and adding fluorinated compounds as water-fogging agents to the film material can effectively prevent food spoilage.

③ Antibacterial film: Adding synthetic zeolite (SiO2+Al2O3) with ion exchange function to the plastic material, and then adding inorganic fillers containing silver ions, silver sodium ions are exchanged to become silver zeolite, which has antibacterial properties on its surface. Using co-extrusion composite technology can give the film a 6μm silver zeolite inner layer; when the silver ion concentration reaches 10-50 ppm, it can completely kill bacteria on the surface of hydro-fruits.

④ Far-infrared preservation film: Mixing ceramic fillers into the plastic film gives it the function of generating far-infrared rays, which can not only sterilize but also activate cells in hydro-fruits, thus having a preservation function.

Sterile packaging film: Mainly used in the production of sterile packaging for food and medicine, it requires: sterilization resistance; high barrier properties and strength; good heat and cold resistance (-20℃ without becoming brittle); good puncture and bending resistance; and printing patterns that will not be damaged during high-temperature sterilization or other sterilization methods.

High-temperature retort pouches: High-temperature retort pouches can be divided into transparent types (shelf life over one year) and non-transparent types (shelf life over two years), high-barrier types and ordinary types. According to the sterilization temperature, they are divided into low-temperature retort pouches (100℃, 30min), medium-temperature retort pouches (121℃, 30min), and high-temperature retort pouches (135℃, 30min).

The inner layer material of retort pouches uses various cast and blown PE (LDPE, HDPE, MPE) films, high-temperature cast CPP or blown IPP, etc. EVAL, aluminum foil, and PVDC film are suitable for the intermediate layer. Biaxially oriented PET, nylon 6, etc. are suitable for surface layer materials. Polyester-type two-component polyurethane acid adhesive is suitable for dry composite film adhesive.

Main advantages of high-temperature retort pouches: ① High-temperature retort sterilization can kill all bacteria; 121℃/30min can kill all Clostridium botulinum; ② Can be stored at room temperature for a long time without refrigeration; can be eaten cold or warmed; ③ Packaging materials have good barrier properties, comparable to cans; ④ Can be reverse-printed with beautiful printing and decoration; ⑤ Waste is easy to incinerate.

High-temperature resistant packaging film: The material melting point is above 200℃, suitable for making high-strength hard/soft containers.

Long press the QR code to follow, Customize your exclusive packaging

www.dgsunpak.cn  Packaging bags