Recyclable single material structure has been in full swing in the domestic packaging market. However, most applications are still concentrated in some low and medium barrier fields. How to implement the recyclable single material structure in the high barrier field or even the high barrier field of high temperature cooking? At present, some enterprises normally produce a single material, whether fully meet the requirements of recycling? First, what is recyclable single material structure? Although recyclable single material structure has been very popular in the domestic market, but some enterprises produce single material structure in the recyclable certification, will not have a high percentage of recovery rate. Figure 1 shows the test data of the recovery rate of composite packaging provided by “Institute Cyclos-HTP Institute of Germany”, which is an independent professional assessment and certification company. At present, it has issued tens of thousands of recycling certificates worldwide. In China, dozens of enterprises such as Huizhou Baoba and Daoco have also obtained the certificates issued by this institute. These recoveries are the test results of composite packaging products whose overall structure conforms to the structure of a single material. Why is there such a big difference?
According to the European CEFLEX guidelines and the data of Institute Cyclos-HTP in Germany, the recovery rates of high purity materials are as follows: single polypropylene film (PP), single polyethylene film (PE) and single polyester film (PET) with the highest recovery rates: High recovery polyolefin composite structure film: recyclable and in the composite structure shall not contain PA, PVDC, aluminum foil, allowed to contain non-main material components (such as ink, glue, aluminum plating, EVOH, etc.) total not more than 5%. Allowed to contain ingredients, is its total content, not separate content, which is a lot of enterprise design product structure prone to errors, resulting in low recovery rate when certification.
Vacuum evaporation process can improve the double barrier function of water and oxygen resistance, which is also a way to improve the highest barrier function at present, and a process with the highest cost performance of water and oxygen resistance function. Vacuum evaporation is one of the processes with the smallest proportion of non-main materials in all the lifting barrier processes. The thickness of aluminum plating layer is only 0.02~0.03u, which has a very small proportion and does not affect the principle of recyclable and recyclable. On the premise of being recyclable, the most widely used coating process is PVA coating, which can improve the oxygen resistance function. The thickness of the coating process is about 1~3u, accounting for a relatively small amount. In terms of oxygen resistance function, it is a cost-effective process, which conforms to the principle of recyclable and recyclable. But PVA has two obvious weaknesses: first, it does nothing to stop water; Secondly, it is easy to lose oxygen resistance function after absorbing water. On the premise of being recyclable, the most widely used co-extrusion process is EVOH co-extrusion at present, while the widely used PA co-extrusion does not conform to the recyclable principle. Under the recyclable principle, PA is prohibited, and the maximum proportion of EVOH is not more than 5%. EVOH co-extrusion thickness is about 4~9u, according to the thickness of the main material is different, EVOH co-extrusion process is easy to exceed 5% of the proportion, especially in the overall thickness of the thin structure, and its barrier also has a direct relationship with the thickness. Under the principle of recyclability, EVOH is limited by the proportion of addition and has limited improvement on barrier. Like PVA coating, EVOH only improves oxygen resistance and does not help water resistance. Based on the current general mature technology, BOPP and PET films can achieve the best resistance to water and oxygen. Bolene film the highest barrier of aluminized BOPP, double barrier below 0.1; At present, there are mature technologies to apply three or two barrier processes to thin films at the same time, with complementary advantages, so as to achieve better barrier performance. Based on the current mature technology, the following table lists the high barrier characteristics of the main recyclable recyclable structures, and the corresponding possible recovery rate of each structure and the application scenario with the most advantages.
Post time: Mar-23-2023