Heat-sealed PE Square Valve Bag

High-Strength Sealing and Structural Stability

Advantages of Heat-Sealing Process: High-frequency heat sealing or heat-sealing machines are used to melt and bond the edges of PE films. The weld strength reaches 30N/15mm (ordinary sewn bags only 15-20N/15mm), eliminating the risk of leakage through needle holes. This makes them suitable for packaging easily leaky materials such as powders and granules, like carbon black and chemical raw materials.

Square-Bottom Structure: Empty bags are cubic. The four sides of the bottom are heat-sealed to form a load-bearing plane. After filling, they stack neatly (stacking height can reach more than 5 layers), increasing warehouse space utilization by 30%. Moreover, the bottom is not easily deformed by extrusion, which prevents leakage.

Efficient Filling and Dust-Proof Performance

The valve adopts a heat-sealed design. When inserted into the equipment during filling, it automatically forms a closed channel. The amount of dust escaping is ≤0.1mg/m³, which meets environmental protection dust emission standards. At the same time, it prevents external impurities from entering the bag, making it suitable for scenarios with high cleanliness requirements such as pharmaceuticals and food.

Material Adaptability and Weather Resistance

After heat-sealing, the PE material has a tight bond between film layers. Its tensile strength is ≥25MPa, and its puncture resistance (puncture force ≥80N) is better than that of ordinary woven bags. It can withstand temperature environments from -30℃ to +70℃, making it suitable for cold chain transportation or high-temperature storage.

Anti-aging masterbatches, such as hindered amine light stabilizers, can be added. When stored outdoors for 6 months, the film layer remains tough, avoiding embrittlement and cracking at heat-sealed parts.

Lightweight and Cost Advantages

The thickness of a single layer of PE film is usually 50-120μm. Under the same load-bearing capacity, it is 40% lighter than paper bags, reducing transportation costs by 15%-20%. The heat-sealing process has a high degree of automation, and production efficiency is 50% higher than that of sewn bags, making it suitable for large-batch customization.

Environmental Protection and Multi-Functional Expansion

PE materials can be recycled and regenerated. Some products use degradable PE, such as adding PBAT masterbatches, which comply with EU packaging regulations. They can be compounded with anti-static films (surface resistance 10⁶-10⁹Ω), moisture-proof aluminum foil layers, etc., to meet the needs of special materials.

Sizes are customized according to packaging weight, material density, and equipment adaptability. Typical specifications are as follows.

Small valve bags have dimensions of 250×200×350mm, with a load-bearing capacity of 5-10kg, suitable for food additives and pharmaceutical intermediates.

Standard industrial bags measure 400×300×600mm, bearing 20-25kg, used for plastic particles, pigments, and chemical fertilizers.

Large valve bags are 550×400×800mm in size, with a load-bearing capacity of 30-50kg, applicable to bulk transportation of cement, mineral powder, and feed.

Extra-large customized bags are 700×500×1000mm, bearing 50-100kg, used for packaging bulk materials such as industrial salt and quartz sand.

Impact of Heat-Sealing Parameters on Performance

The heat-sealing temperature is controlled at 180-220℃ (adjusted according to the melting point of PE), with a pressure of 0.3-0.5MPa and a pressure-holding time of 3-5s. This ensures that the weld has no false welding or melting perforation. A typical heat-sealing strength test (peel test) needs to reach ≥25N/15mm.

Valve Structure Design

Common valve types:

Flanged Valve: After heat-sealing, an inwardly folded flange is formed. It automatically opens during filling and can be folded and sealed after unloading, suitable for materials that need to be taken multiple times.

Threaded Valve: A PE threaded sleeve is embedded during heat-sealing, combined with a dust cover, and the sealing performance reaches IP65 level, suitable for high-dust or humid environments.

Anti-Fatigue Design

The edges of the heat-sealed seams on the bag body adopt arc transitions (R≥2mm) to avoid cracking caused by stress concentration. The heat-sealed areas at the four corners of the bottom are thickened to 150-200μm to enhance tear resistance during repeated handling.

Typical Applications:

In the chemical field: PVC resin, titanium dioxide, washing powder.

In the food industry: white sugar, starch, coffee beans (requiring food-grade PE certification, such as FDA compliance).

In the building materials industry: putty powder, tile adhesive, grouting material.

Selection Notes:

Choose the PE material grade according to the material characteristics: food-grade needs to comply with GB 9688, and chemical-grade needs to resist solvent penetration (such as adding an EVOH barrier layer).

Heat-sealed bags are not recommended for packaging strong oxidants, such as potassium permanganate, to avoid accelerated aging of the PE film. Special structures with composite aluminum foil layers can be chosen instead.

If involving automatic filling lines, it is necessary to confirm in advance that the valve size matches the equipment interface (for example, the valve diameter is usually 50-100mm).

For customizing anti-static, high-temperature resistant (short-term resistance to 120℃) or light-proof heat-sealed bags, they can be realized by adding conductive carbon black, glass fiber, or matte masterbatches. At the same time, it is recommended that suppliers provide performance test reports such as heat-sealing strength and drop resistance (no damage after 3 drops from a height of 1.5m).

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