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A bit of experience using a solvent-free process
Time: 2014-03-27 Source: Packaging Frontier Reading: 9386 times
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Wenzhou Junchuan Machinery Equipment Co., Ltd.

Abstract: Kaida currently has a total of 3 solvent-free equipment in normal production, with a general startup speed of 300m / min and a minimum speed of 250m. Compound OPP // CPP, PET // CPP, PA // CPP, BOPP // VMCPP, PA // PE and other structural products, the monthly startup rate is about 26 days. This article analyzes the factors of successful use of solventless compounding, and points out that when formulating the parameters of solventless compounding process for flexible packaging companies, they must comprehensively consider the matching of printing process, the rationality of compounding process, transportation and application.

Solvent-free compounding originated in Germany in the last century. Due to its characteristics of economy, environmental protection, high efficiency, and low energy consumption, it has also developed rapidly in China in recent years, becoming a common and important composite process for flexible packaging.

Solvent-free compounding is a compounding method in which the solvent is not used to dilute the adhesive during the production process. The production process is mainly to preheat the solvent-free adhesive to reduce its viscosity to a suitable viscosity, and then according to a certain ratio It is uniformly mixed by a glue mixer, and then transferred to each other through five rolls, coated on the substrate, and then cured at a certain temperature, so that the adhesive NCO and OH are completely reacted to complete the composite process.

With the continuous development of solvent-free compounding technology, the range of use of solvent-free compounding has also changed from the original lightweight packaging to the current heavy packaging, cooking packaging, etc. The types of solventless adhesives are also becoming more and more diverse. Therefore, when formulating the parameters of the solventless process for flexible packaging companies, they must comprehensively consider from printing, compounding, transportation and application.

I. Matching of printing process

Each process in the production process can be seen as the "customer" of the previous process. For flexible packaging production, in order to satisfy "composite customers" and reduce the risk of compound customers, we are required to consider the compatibility with solvent-free composites in addition to the elements of the printing process when formulating the printing process. .

Solvent-free glues have good leveling properties, low sizing amount, and no initial tackiness. Therefore, companies should pay special attention to the selection of ink systems and the control of solvent residues (especially the control of alcohol residues) when formulating printing processes. For example, when printing transparent ink products, pay attention to the ink fineness and selection of the ink system. If it is not selected properly, abnormalities such as bubbles or ink dissolution after solvent-free compound curing will occur. Because the reaction principle of solvent-free glue is that NCO reacts with OH, if the OH content in the printed film is too high, it will cause the OH group to fail to fully react after the solvent-free composite curing, which will cause the glue to dry.

Second, the rationality of the composite process

Compounding mainly uses adhesives to bond various materials together, giving full play to the characteristics of each layer of film material, so that the compounded product can meet customer requirements. In order to meet the customer's quality requirements, we are required to consider the influence of glue temperature, material corona treatment, adhesive, curing process and other factors on product quality when formulating the process.

Such as:

Temperature change: Seasonal changes will cause the temperature of the adhesive to change to a certain extent. In order to ensure the appearance of the product, the preheating temperature of the glue can be appropriately increased in winter.

Humidity change: The change of temperature and humidity in the environment will change the OH content in the environment, which will affect the incomplete reaction of solvent-free adhesive NCO with OH. In severe cases, the mature product will not dry.

Corona treatment process: Due to the surface tension decay phenomenon (such as VMCPP, VMPET, etc.) of some special materials after being placed for a certain period of time, many manufacturers choose to corona treat the composite material before recombination. Although this method solves the surface tension of the material, the corona treatment will affect the barrier properties of the material. Therefore, the corona treatment of the material should be reasonable and should not be too large.

Product transportation

With the global integration of the economy, many domestic packaging manufacturers have received orders from foreign customers. In this case, we must consider the impact of transportation on product quality, especially shipping, when developing the process. The transportation environment of high temperature in the daytime and low temperature in the sea will have a direct impact on the friction coefficient of PE film and the shrinkage of PE film. Therefore, when producing such products, special adhesives that have little effect on PE slip agents are used for production. You cannot choose ordinary adhesives and change the curing temperature to solve this problem.

Fourth, customer use plan

After the development of the enterprise, many companies have opened factories and branches in various places. Some customers will require the same structure for each branch in order to facilitate internal transfers. However, different factories are located in different areas. When producing products of the same structure, the effects of area and temperature difference must be considered in the process, that is, the altitude difference between the plateau and the plain, the temperature difference between the north and the south, and the humidity in the northwest and southeast during summer. Differences, etc. At the same time, the weatherability of the adhesive must be considered, and the proportion of the adhesive must be adjusted depending on the region. Otherwise, the adhesive may occasionally have incomplete reactions after maturation, resulting in dry glue and affecting subsequent use. .

V. Conclusion

The process parameters of any product are unique and special. When producing any product, you must know more about the product's research and development, design, manufacturing, transportation, use and consumption, and choose the most suitable for all factors. In order to formulate the most applicable and accurate process parameters and use solvent-free compounding, the process parameters and types of adhesives can be formulated.

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