Abstract:This paper analyzes the application and development trend of solvent-free composite high temperature retort pouch,and introduces the main points of process control,including the setting and confirmation of coating amount, the humidity range of the environment,the parameter setting of equipment operation,and the requirements of raw materials,etc.
The steaming and sterilization method has existed for many years. In China, due to the late development of solvent-free adhesives, almost all of them were used to composite high-temperature cooking packaging. Now, solvent-free adhesives have undergone ten years of development in China, with significant improvements in equipment, raw materials, personnel, and technology. In the context of national environmental protection policies, color printing enterprises have created greater development space for solvent-free adhesives in order to seek profit and development, driven by the factor of increasing production capacity.Therefore, the coverage of solvent free adhesives is becoming increasingly broad, and steaming, sterilization, and packaging are one of them.
1.The concept of cooking sterilization and the application of solvent-free adhesives
Cooking sterilization is the process of sealing and killing bacteria in airtight containers by applying pressure and heating. In terms of application structure, steaming and sterilization packaging is currently mainly divided into two types: plastic and aluminum-plastic structures. The cooking conditions are divided into two levels: semi high temperature cooking (above 100 ° C to 121 ° C) and high temperature cooking (above 121 ° C to 145 ° C). Solvent free adhesives can now cover cooking sterilization at 121 ° C and below.
In terms of applicable products, let me briefly introduce the application situation of several products of Kangda:
Plastic structure: WD8116 has been widely and maturely applied in NY/RCPP at 121 ° C;
Aluminum plastic structure:The application of WD8262 in AL/RCPP at 121 ° C is also quite mature.
At the same time, in the cooking and sterilization application of aluminum-plastic structure, the medium (ethyl maltol) tolerance performance of WD8262 is also quite good.
2.The Future Development Direction of High Temperature Cooking
In addition to the familiar three – and four layer structures, the main materials used are PET, AL, NY, and RCPP. However, other materials have also begun to be applied to cooking products on the market, such as transparent aluminum coating, high-temperature cooking polyethylene film, etc. However, they have not been used on a large scale or in large quantities, and the basis for their widespread application still needs to be tested for a longer period of time and more processes.In principle, solvent-free adhesives can also be applied, and the actual effect is also welcome to be verified and tested by color printing enterprises.
In addition, solvent-free adhesives are also improving their performance in terms of sterilization temperature. At present, significant progress has been made in the performance verification of Konda New Materials’ solvent-free products under conditions of 125 ° C and 128 ° C, and efforts are being made to reach higher temperature cooking peaks, such as 135 ° C cooking and even 145 ° C cooking.
3.Key points of application and process control
3.1 Setting and confirmation of adhesive amount
Nowadays, the popularity of solvent-free equipment is increasing, and many manufacturers have gained more experience and insights in using solvent-free equipment. However, the high-temperature cooking sterilization process still requires a certain amount of interlayer adhesive (i.e. thickness), and the adhesive amount in general processes is not enough to meet the needs of cooking sterilization. Therefore, when using solvent-free adhesive for composite cooking packaging, the amount of adhesive applied should be increased, with a recommended range of 1.8-2.5g/m ²。
3.2 The humidity range of the environment
Nowadays, many manufacturers are beginning to realize and attach importance to the impact of environmental factors on product quality. After certification and a summary of numerous practical cases, it is recommended to control the environmental humidity between 40% and 70%. If the humidity is too low, it needs to be humidified, and if the humidity is too high, it needs to be dehumidified. Because a portion of the water in the environment participates in the reaction of solvent-free glue, However, excessive water participation can reduce the molecular weight of the glue and cause certain side reactions, thereby affecting the high-temperature resistance performance during cooking. Therefore, it is necessary to adjust the configuration of A/B components slightly in high temperature and humidity environments.
3.3 Parameter settings for device operation
Parameter settings are set according to different device models and configurations; The tension setting and the accuracy of the dispensing ratio are all details of control and confirmation. The high degree of automation, precision, and convenient operability of solvent-free equipment are its own advantages, but it also covers the significance of meticulousness and caution behind it. We have always emphasized that solvent free production operations are a meticulous process.
3.4 Requirements for raw materials
Good flatness, surface wettability, shrinkage rate, and even moisture content of thin film raw materials are necessary conditions for completing the cooking of composite materials.
- The advantages of solvent-free composites
Currently, high-temperature cooking and sterilization products in the industry mainly use solvent based adhesives for dry compounding. Compared to dry composite, using solvent-free composite cooking products has the following advantages:
4.1 efficiency advantages
The advantage of using solvent-free adhesives is primarily an increase in production capacity. As is well known, using dry composite technology to process high-temperature cooking and sterilization materials has a relatively low production speed, generally around 100m/min. Some equipment conditions and production control are good, and can achieve 120-130m/min. However, the conditions are not ideal, only 80-90m/min or even lower. The basic output capacity of solvent-free adhesives and composite equipment is better than that of dry composite, and the composite speed can reach 200m/min.
4.2 cost advantage
The amount of glue applied to solvent based high-temperature cooking glue is large, basically controlled at 4.0g/m ² Left and right, the limit is not less than 3.5g/m ²； Even if the amount of glue applied to solvent-free cooking glue is 2.5g/m ² Compared to solvent based methods, it also has a significant cost advantage due to its high adhesive content.
4.3 Advantages in safety and environmental protection
During the use of solvent based high-temperature cooking glue, a large amount of ethyl acetate needs to be added for dilution, which is detrimental to environmental protection and production workshop safety. It is also prone to the problem of high solvent residue. And solvent-free adhesives have no such concerns at all.
4.4 Energy saving advantages
The curing ratio of solvent based adhesive composite products is relatively high, basically at 50 ° C or above; The maturation time should be 72 hours or more. The reaction speed of solvent-free cooking glue is relatively fast, and the demand for curing temperature and curing time will be lower. Usually, the curing temperature is 35 ° C~48 ° C, and the curing time is 24-48 hours, which can effectively help customers shorten the cycle.
5.Conclusion
In summary, solvent-free adhesives, due to their unique properties, color printing enterprises, adhesive enterprises, and solvent-free composite equipment production enterprises have cooperated and supported each other for many years, providing valuable experience and knowledge in their respective fields. We believe that solvent-free adhesives have a wider range of applications in the future.The development philosophy of Kangda New Materials is “we have been working hard to create value for customers and move them”. We hope that our high-temperature cooking products can help more color printing enterprises explore new solvent-free composite application fields.
Post time: Dec-22-2023