The Square Valve Bag's sealing structure is central to its zero-leakage performance under high pressure. This goal is achieved through optimized valve port structure, the use of multi-layer composite materials, elastic sealing element design, automated filling adaptation, bottom square structural support, and rigorous production process control.
The valve port, as the critical passage for material in and out, directly impacts sealing performance. The Square Valve Bag's valve port typically utilizes either an internal or external port. The internal port automatically closes under the weight of the material during filling, while the external port relies on manual folding or mechanical compression to seal. This design ensures a tight fit after filling, forming the first physical barrier. For example, the internal port utilizes specially designed bevels or elastic tabs to automatically compress the valve port edges under the weight of the material, eliminating gaps. The external port utilizes hot melt adhesive or ultrasonic welding to securely connect the valve port to the bag body, preventing leakage under high pressure.
The use of multi-layer composite materials provides the Square Valve Bag with a high-strength physical foundation. The bag body is typically made of a composite of materials such as kraft paper, plastic film, or aluminum foil. The outer layer of kraft paper provides tear and abrasion resistance, while the middle layer of plastic film enhances moisture resistance and barrier properties. The inner layer may also have a food-grade coating to meet hygiene requirements. This structure not only enhances the bag's overall strength but also effectively distributes stress under high pressure, preventing localized damage and leaks. For example, the paper-plastic composite square valve bag combines the stiffness of paper with the flexibility of plastic, maintaining its shape during high-pressure filling and reducing the risk of deformation.
The design of elastic sealing elements is one of the key technologies for achieving zero leakage in square valve bags. A rubber or silicone sealing ring is often embedded around the valve opening. These materials elastically deform under high pressure, filling the tiny gap between the valve opening and the bag body. For example, the inner valve opening may utilize a double-layer sealing structure: a hard plastic support ring on the outer layer and a soft rubber sealing layer on the inner layer. This ensures the rigidity of the valve opening while also utilizing the elasticity of the rubber to ensure a tight fit under high pressure. Furthermore, some square valve bags feature leak-proof grooves or raised protrusions on the valve opening edge to further enhance the sealing effect.
The compatibility of automated filling equipment is crucial to the sealing performance of square valve bags. The valve design of a square valve bag must precisely match the filling machine's discharge nozzle to ensure smooth material flow into the bag without spillage. For example, the filling machine's discharge nozzle may feature a tapered design, creating a close fit with the inner wall of the valve opening to minimize material residue. Furthermore, the filling machine uses sensors to control the filling volume to prevent overfilling, which could cause the bag to bulge and compromise the seal. This precise fit ensures that square valve bags maintain zero leakage even in high-speed automated production.
The square bottom design indirectly enhances the sealing stability of the square valve bag. This square bottom ensures that the bag remains upright during filling and stacking, reducing uneven force on the valve opening due to tilting or collapse. For example, during automated palletizing, the square bottom ensures that bags are tightly packed together, preventing deformation that could compromise the valve seal. Furthermore, the square bottom design enhances the overall rigidity of the bag, making it less susceptible to deformation under high pressure, thereby maintaining the integrity of the seal.
Strict production process control guarantees the sealing performance of the square valve bag. From raw material inspection to finished product testing, every step must meet high standards. For example, the welding or gluing process of the valve mouth must pass tensile testing and airtightness testing to ensure that it can withstand high pressure without falling apart. The composite material of the bag body must pass peel strength testing to prevent leakage caused by interlayer separation. In addition, the production environment must be kept clean to avoid impurities that may affect the sealing performance.
