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Practitioners in the flexible packaging industry are well aware that the origin of flexible packaging is a substitute derived from canned products, commonly known as “soft cans”. In laminated flexible packaging products, the product that best reflects soft canned goods is the spout pouch product.
This representativeness is mainly determined by the characteristics of the spout pouch itself: strictly speaking, the spout pouch is a product that combines hard and flexible packaging, and cannot be simply regarded as a flexible packaging product.
The combination of hard and soft parts is the most distinctive part of the spout pouch in the flexible packaging category.
Therefore, whether in traditional lamination structures or in new recyclable mono-material, the requirements for such products are quite special. This article mainly explores their process control points to reduce waste and losses in the production process or reduce product development investment.
The application field of laminated flexible packaging spout bags is very wide, whether in the food industry, daily chemical products, pharmaceuticals or health products, they occupy a very large share. In these application fields, spout pouch products are divided into three categories based on their contents: powder, fluid, and liquid, with different structural designs.
For powdered products, a 2-3 layer structure is generally used to make 100% recyclable mono-material PE spout pouch, such as:
PE/PE
PE/PE/PE
It is used to package lightweight products such as essence materials, granulated white granulated sugar, toner, etc. The three layers of materials are designed to achieve certain decoration effects.
Fluid products generally use a 3-4 layer recyclable mono-material PE structure, such as:
PE/PE/PE
PE/PE/PE/PE
Used for packaging fluid products such as salad dressings, vegetable and fruit sauces, jelly, etc., using a 3-4 layer material structure to ensure that the physical properties meet the requirements.
Liquid products generally use 3-4 layers of material structure, such as:
PE/PE/PE
PE/PE/PE/PE
The main purpose of process design is to protect the transportation and use of products, used for packaging daily chemical products such as laundry detergent, fruit juice, beverages, and even some alcoholic beverages and water products. Of course, some lightweight liquid suction nozzle bags also have a two-layer material structure design, such as products below 100ml.
Basically both conventional material spout pouch and mono-material spout pouch are difficult to make. But the 100% recyclable mono-material PE spout pouch is even more difficult to make cause the low heat resistant of PE and low stiffness and unstable of PE film.
Today we will talk about 6 important points of how to make a better recyclable PE spout pouch.
In terms of raw material process design, the fabric must be designed according to conventional processes, and the fabric must be high temperature resistant and pressure resistant. This pressure resistance mainly refers to the pressure and high temperature that can be withstood during nozzle pressing. For single material nozzle bags, special attention should be paid to the temperature resistance of the fabric, otherwise it is easy to be crushed. As for the bottom material, according to convention, the lower the heat sealing temperature of the bottom material, the more favorable it is for the heat sealing performance between the bag body and the nozzle.
So the inner PE needs to be low temperature PE, and the nozzle needs to be low temperature PE too.
Ink needs to use high temperature resistant materials, especially at the nozzle position. If necessary, curing agents need to be added to improve the temperature resistance of the nozzle position.
If the product design has matte oil, the position of the pressure nozzle is usually designed in a non matte oil position.
Some people may wonder why there is usually no matte oil printed on the nozzle position? This is because there are differences in the temperature resistance of some matte oils in China, and many matte oils are prone to sticking back under high temperature and pressure in the heat sealing position. At the same time, the heat sealing knife for manual nozzle sealing generally does not have high-temperature cloth attached, and the anti sticking of matte oil is prone to accumulate on the nozzle sealing knife.
Therefore, in general, designing the nozzle position as a non mute oil level is more conducive to production control.
Lamination requires the use of high-temperature resistant adhesive, of course, the high-temperature resistant adhesive here does not refer to high-temperature cooking adhesive, but rather adhesive suitable for high temperature nozzle pressing.
For suction nozzle bags that require high-temperature cooking, the glue must be selected from high-temperature cooking grade glue. As producers, we must have a clear understanding of our customers’ usage requirements for high-temperature steaming bags with added suction nozzles. Because once a suction nozzle is added to the bag, under the same cooking conditions, it is likely that the bag will burst at the junction between the bag body and the suction nozzle due to unreasonable pressure relief or insufficient pressure maintenance during the cooking process. This is because the bursting location is mainly concentrated at the weakest point of the soft hard junction. Therefore, for high-temperature steaming bags with suction nozzles, special caution should be taken when accepting orders. It is important to clarify the customer’s usage requirements, otherwise it can easily lead to waste of bulk products.
For products with manual nozzle pressing, special attention should be paid to the size control of the suction nozzle position. Generally, there is a certain size space range for the suction nozzle position size. If this space range is too narrow, it is difficult to fit the suction nozzle in, which may cause the bag body to be crushed. If the space range is too large, the suction nozzle is prone to fall off and misalignment when placed. Therefore, when designing the space range for placing the suction nozzle, the mold must reserve the size range for smoother manual nozzle pressing in the subsequent process.
There are currently two main production modes for nozzle presses, one is manual mode and the other is fully automatic nozzle press machine automation mode.
For manual pressure nozzles, we generally need to pay attention to the same three elements as bag making: time, temperature, and pressure. Pressure nozzles pay more attention to temperature and pressure. For 100% recyclable PE spout pouch, the staff of the nozzle press machine must pay special attention to the temperature and pressure control of the nozzle press machine. The temperature resistance of Matte PE film is always poor, and it is very easy to crush and produce false sealing when the temperature is not enough. Therefore, the temperature difference range of this type of product will be relatively small, and it is necessary to be very cautious during production. For this type of product, we also need to pay special attention to the design of raw materials and processes. The fabric should strive to improve its temperature resistance, and the base material should try to lower its sealing temperature as much as possible. Similarly, the suction nozzle should also lower its sealing temperature as much as possible to better heat seal with the bag body and increase the temperature difference range.
Automatic nozzle sealing machines are easier to control than manual nozzle pressing machines. Automatic nozzle sealing machines generally have preheating and cooling knives, which can heat seal the suction nozzle and bag body through multiple sealing presses like bag making machines. However, for automatic nozzle pressing, it is important to coordinate the pressure matching of the hot knife, preheating knife, and cold sealing knife effectively. Therefore, the main focus of the automatic nozzle pressing method is on the matching of pressure and temperature. Given that each equipment manufacturer has different process designs or equipment model numbers, operators need to treat them differently.
Mainly testing the finished products of bag making process and nozzle pressing process.
In the bag making process, it is necessary to test whether the physical properties of the product are qualified without a pressure nozzle. For example, testing the drop performance of the bag, whether it meets the national standard height and number of drops within the national standard range, without breaking or leaking, and further testing whether it meets the customer’s drop requirements. Only after passing the test can further production or production adjustments be made. If its drop performance does not meet the standard without a nozzle, it will be even more difficult to meet the relevant requirements after the nozzle is pressed. The pressure resistance performance is the same, it is necessary to test whether it meets the national standard pressure resistance index or the customer’s required pressure resistance index before pressing the nozzle.
The finished product after pressing the nozzle also needs to undergo drop resistance and pressure resistance tests, especially at the junction of the nozzle and the bag body, which is the connection position where the entire bag is heat sealed and compressed, with the largest thickness difference. When testing for drop or pressure resistance, it is also the most likely location to break the recyclable spout pouch.
The recyclable PE spout bag has its own uniqueness, so in order to produce recyclable PE spout pouch efficiently and with high quality, the characteristics of the nozzle bag need to be considered from raw materials, structure to production process and testing. Adjustments should be made based on the process design of general bag products.
Longdapac is the leading recyclable mono-material PE flexible packaging manufacturer. It is the first supplier of recyclable mono-material PE spout pouch. After 2 years R&D, the quality of recyclable spout pouch is as good quality as the conventional material.