Product Overview

Square bottom valve port PP woven bags, also known as three-dimensional bags, are shaped packaging specially designed for automatic powder filling and neat pallet stacking, differing greatly from ordinary flat valve bags that deform randomly after being filled. Its unique square bottom structure enables the bag to stand upright automatically once loaded with materials, forming neat cuboid shapes for stable stacking in warehouses and containers. This product relies on dedicated square bottom valve bag forming equipment for final molding, with a whole set of streamlined roll-to-roll production procedures.

The complete production route starts with conventional PP yarn drawing and circular weaving to produce finished woven fabric rolls. Subsequent continuous processing is carried out directly on the fabric rolls in sequence: customized printing, film lamination and surface micro-punching. Both flexographic plain printing and BOPP color printing are available for customization, yet lamination is a mandatory matching process for either printing type to prevent pattern abrasion and fading. Tiny micro holes punched on the surface serve as air vents to exhaust trapped air during filling, preventing bag bulging and improving stacking flatness. After finishing printing, lamination and perforation, the treated fabric rolls are fed into professional square bottom valve bag machines for subsequent procedures: cutting to fixed length, edge slitting, glue coating, valve port forming and bottom gluing sealing to make finished products. Each finished bag features uniform fabric density, stable tensile strength and consistent dimensional accuracy across batches, with customizable sizes and printed contents as required by brand packaging standards.

This square bottom valve bag stands out for its integrated roll processing and tidy upright stacking effect. Standard sizes are available with flexible order quantities, widely favored by dry mortar factories, chemical powder manufacturers, mineral powder plants and food additive enterprises equipped with automatic filling lines. After filling, orderly cuboid shapes optimize storage space utilization and effectively reduce the risk of stack collapse during long-distance transportation.

The continuous roll processing mode improves production efficiency greatly compared with piece-by-piece processing. The laminated outer layer provides dustproof, moisture-proof and wear-resistant protection for printed patterns. Empty bags can be folded flat to save storage space, while the combination of woven substrate, valve structure and sealed square bottom effectively avoids powder overflow and leakage during high-speed filling.

With continuous roll printing-lamination-perforation workflow, dedicated square bottom valve bag molding equipment, vented micro holes, mandatory lamination for all printed versions and excellent palletizing performance after filling, Square bottom valve port PP woven bags have become the preferred standardized packaging for various powdery and granular industrial bulk raw materials.

FAQ

Q: Are samples free of charge?

A: Existing standard samples are free (freight collect). If you require a custom prototype sample with your specific printing, a sampling fee (approx. RMB 200–500) applies. This fee will be refunded against your future bulk order.

Q: How many bags can fit into a 20'GP or 40'HQ container?

A: Capacity depends on the bag size and thickness. Taking a standard 48gsm, 50x80cm bag as an example:
20'GP: Approx. 260,000 pieces (Baled).
40'HQ: Approx. 610,000 pieces (Baled).
We will provide a professional Loading Plan for your reference.

Q: What is a "Laminated Bag"? When do I need lamination?

A: A laminated bag features a layer of LDPE (Low-Density Polyethylene) film extrusion-coated onto the woven fabric. If you are packing powders (e.g., flour, putty powder) or moisture-sensitive materials (e.g., fertilizers, chemicals), lamination is essential to prevent leakage and provide a basic moisture barrier.

Q: What is the correct HS Code for woven bags on the Commercial Invoice and Packing List?

A: Woven bags are typically classified under HS Code 6305.33 (of synthetic textile materials) or 3923.29 (of plastics). We can provide a suggested code based on your specific bag composition, but the final declaration should always be confirmed with your local customs broker to mitigate inspection risks.

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