The material and process requirements of several mouth of vertical bag are quite different
Release time: 14:46:08, July 3, 2020 reading volume: 1445 times
In production Suction bag In order to make better products, we must understand its production process and material properties.
one Requirements for bag making equipment
The production of vertical bag has special requirements for the structure of bag making machine. In addition to the six main mechanisms (unwinding part, two link swing rod, heat sealing part, constant tension device, sensor and cutting part) of ordinary three side sealing bag making machine, there is also an auxiliary discharging device at the side of the main unwinding unit, which is specially used to provide the bottom material for the vertical bag.
two Selection of composite materials
Due to the high requirements of mechanical properties of materials for vertical bags, multilayer composite films are generally used.
one , outer layer
The outer layer is the printing material. At present, the commonly used vertical bag printing material on the market is in addition to the ordinary OPP Circumscribed, and PET 、 PA Materials with high strength and high barrier can be selected according to the situation. If it is used to pack dry fruit solid products, it can be selected BOPP , extinction BOPP And other common materials. If packaging liquid products, generally choose PET or PA Material Science.
two , middle layer
The intermediate layer is generally made of high strength and high barrier materials, such as PET 、 PA 、 VMPET , aluminum foil, etc. and RFID It is required that the surface tension of the intermediate layer material should meet the requirements of composite, and it must have a good affinity with the adhesive.
three , inner layer
The inner layer is the heat seal layer, which is generally selected PE or CPE 、 CPP And other materials with strong low temperature heat sealing performance. It is required that the surface tension of the composite surface must meet the composite requirements, but the surface tension of the hot surface must be lower than 34mN/m And it should have good anti pollution ability, antistatic ability and heat sealing property.
three Requirements for bag making process
one Heat sealing temperature
When setting the heat sealing temperature, the following factors should be considered: first, the characteristics of the heat sealing material; second, the thickness of the film; third, the times of hot pressing and the size of the heat sealing area. In general, the same part of the hot pressing times more, the heat sealing temperature can be set lower appropriately.
two Heat sealing pressure
Heat must be applied to the cover to promote thermal bonding when possible. However, if the pressure is too high, the molten material will be extruded, which will not only affect the flatness of the bag, fault analysis and troubleshooting, but also affect the heat sealing effect of the bag and reduce the heat sealing strength.
three Heat sealing time
The heat sealing time is not only related to the heat sealing temperature and pressure, but also to the performance of the heat sealing material and the heating method. The specific operation should be adjusted according to different equipment and materials during the actual test run.
four Heating mode
There are two kinds of heating methods of heat sealing knife in bag making: one side heating and two sides heating. It is obvious that the two-sided and practical heating mode is more efficient than the unilateral heating mode.
There are many problems in the actual production of vertical bags, but there are mainly two prominent problems: one is the leakage of liquid or gas when filling goods; the other is the uneven shape and asymmetric bottom seal in the process of bag making. Therefore, how to choose the best materials and adopt the best operation mode plays a decisive role in improving the overall quality of the vertical bag.
Process requirements of welding nozzle
Suction bag There are two parts in the process, bag making and welding nozzle. Each link has higher process requirements. If the process is not well mastered, it is easy to produce quality problems such as bag breaking and leakage. Although there are many domestic flexible packaging enterprises can produce Suction bag However, few of them have really passed the quality standard.
In order to produce high-quality vertical bags, special attention should be paid to punching, bag bottom and heat sealing at the bottom. Especially, the joint of four layers and two layers of vertical bags is easy to break. It is not enough to only rely on horizontal sealing knife. Heat sealing knife should be installed and heat sealing should be strengthened locally. Besides, Suction bag Good opening performance is required, otherwise it is difficult for the suction cup to pull the mouth to install the mouth; the friction coefficient of the bag surface should be small, and the surface static electricity should be eliminated during bag making, so as to prevent the adsorption between bags, which is not conducive to the bag taking by the mouth sealing machine.
Suction bag It can be designed into a special-shaped bag, which is beneficial to enhance the attraction of packaging. However, it must be noted that the bag width of the top welding nozzle should be greater than 40mm In order to ensure the high success rate of the automatic welding nozzle machine.
At present, there are two kinds of welding nozzle technology in China: one is manual installation and one-time heat sealing process. In this process, the temperature is transferred to the mouth by means of heat conduction, so that the mouth is melted and connected with the bag PE The sealing layers are welded together. Due to the large heat capacity of the plastic nozzle, the melting of the primary heat sealing nozzle will make PE The sealing layer is overheated, PE It is difficult to ensure the sealing strength by one-time heat sealing; the mouth is not in line with the requirements of food hygiene, and the consistency is poor. Due to the above shortcomings of manual installation of nozzle primary heat sealing process, this process is generally prohibited in foreign countries.
The mouth is automatically loaded by a sealing machine, four Besides, the plastic nozzle should be preheated before welding nozzle. These technological steps ensure the internal and external quality of welding and meet the hygienic standards. When using the automatic sealing machine, the sealing pressure should be controlled within four ～ five Kg / Square centimeter, in the first three The heat sealing pressure is increased gradually during the secondary heat sealing.
The automatic nozzle sealing machine uses the vibrating plate to automatically send the plastic nozzle into the welding line, which requires a high consistency of the plastic nozzle shape, otherwise, it will cause jamming and stop the equipment. The difference in the shape of plastic nozzle will also cause insufficient sealing strength and leakage. Therefore, the plastic nozzle with good quality must be selected, and its shape and position error should be controlled within 0.1mm Within. The welding strength of the hard nozzle is determined by the matching degree of the heat sealing part between the heat sealing mold and the plastic nozzle. After selecting a kind of hard nozzle, the heat sealing mold should be removed, and the heat sealing part of the hard nozzle should be clamped with the mold for light transmission inspection, and the heat sealing mold should be carefully ground to make the heat sealing parts completely consistent.
Production inclined port installation type Suction bag In addition to the above process requirements, attention must be paid to the distance between the hard mouth and the top edge of the bag at least in the bag shape design 10mm It is convenient to heat seal the top edge after filling from the top, so as to avoid damage to the plastic nozzle when heat sealing the top edge. In addition, reducing the angle between the incision and the side of the bag can make the installation position of the hard mouth move down, which is conducive to increasing the distance between the hard mouth and the top edge of the bag.
To guarantee Suction bag The production quality of flexible packaging manufacturers should be equipped with pressure testing instruments according to the three If the bag making process is strictly followed, 200ml Of Suction bag It's affordable 70kg Above the pressure.
one Material type
PET Optional Bopp There has to be a big package PA （ NY Nylon), special contents need special PE 。
two Parameters that the product must meet
Heat sealing strength: ≥ 80 N/mm
Peel strength: ≥ 2.5 N/mm
Bearing strength: ≥ 70kg
Acid and alkali resistance: PH9.5 , acid PH3.5 。