Offset-printed, plastered, gypsum‑woven packaging bag with a square bottom and valve opening

I. Product Introduction (Woven Bags)

This product is Square-bottom valve bag (glue-sealed bag) , specially for Lightweight plaster gypsum Design, net content 25 kg. The bag clearly labels the product’s key features: Resists hollowing and prevents cracking. 、 Easy construction 、 Green and environmentally friendly It employs monochrome printing and features a cost-effective, precision‑aligned packaging design, while also offering automated filling compatibility, leak‑proof and dust‑proof performance, and stable palletizing.

II. Applicable Scenarios

Packaging for lightweight plastering gypsum, painting gypsum, and other dry-mix mortar products.

Fully automatic valve‑mouth filling on the building‑materials production line

Warehouse stacking, long-distance transportation, and retail sales at building materials markets

Dry powder material companies with requirements for packaging efficiency and moisture‑proof performance.

III. Applicable Materials

Lightweight plaster gypsum

Plaster for painting

Tile adhesive

Crack-resistant mortar

Putty powder

Other dry powdered building materials

IV. Core Advantages

Product Level:

Resists delamination and prevents cracking: Bonds firmly to the substrate, ensuring long-lasting durability.

Green and environmentally friendly: low-carbon and safe, aligning with the trend of new eco-friendly building materials.

Easy construction: saves time and effort, boosting construction efficiency.

At the packaging bag level:

Automatic filling with a square-bottom valve: compatible with automated production lines, delivering high packaging efficiency.

Leak-proof and dustproof: self-sealing valve opening + needle-free sealed bottom, eliminating powder leakage.

Monochrome printing, economy version: low plate fees and affordable unit price.

Square-bottom palletizing stability: After filling, the product forms a brick‑shaped cuboid, ensuring neat and orderly stacking.

High Strength and Tear Resistance: PP woven fabric boasts high tensile strength.

Moisture-proof and freshness-preserving: The PE film layer blocks moisture, preventing clumping.

V. Automatic Filling with Square Bottom and Valve Opening

Valve port structure: One side of the bag body is equipped with a filling valve port (typically an upper valve port).

Filling equipment: compatible with screw‑type valve‑mouth packaging machines or pneumatic filling machines.

Filling efficiency: up to 300 per machine ~ 600 bags per hour; the fully automated line can reach 800. ~ 1,200 bags/hour

Automatic sealing: Filling pressure causes the valve opening to seal itself, eliminating the need for bag stitching.

VI. Leak-Proof and Dust-Proof Design Details

Self-sealing valve port : After filling, the material pressure presses the inner side of the valve seat tightly, creating a natural seal.

PE inner membrane composite : The intermediate PE film covers the woven gaps, preventing fine powder from leaking out.

Hot-melt adhesive bottom coating : Bottom seam with no pinholes, offering far superior sealing compared to sewn-bottom bags.

Laminated sealing : The outer coating further seals the pores of the woven fabric.

VII. Monochrome Printing – Economy Model

Number of printing colors: 1–2 colors (typically the product name, brand logo, and net content)

Plate‑making costs: A single‑color plate costs approximately RMB 200–500 (depending on the supplier); bulk orders may qualify for discounts.

Price advantage: Compared with full-color customizations, monochrome models can reduce the unit price by 30% to 50%.

Customizable content: Can include the company name, product name, usage instructions, recycling symbols, and more.

8. Stability of Stacking with Square Bottoms

Post-filling appearance: The powder naturally forms a rectangular prism (brick-shaped) within the bag, with a flat bottom.

Independence: Can stand independently without leaning against a wall.

Stacking performance: The corners are neatly aligned, and the stack can reach 8 to 10 layers without toppling.

Warehousing and Transportation: Space-saving, suitable for container and palletized shipping.

9. Comparison between Square-Bottom Valve Bags and Flat Bags (Open-Top Bags/Sewn-Bottom Bags)

Appearance and Bottom : Square-bottom valve bags are square-shaped, sealed with hot-melt adhesive for a smooth, aesthetically pleasing finish; flat bags are round, sealed with stitched seams, resulting in visible thread ends.

Dustproof sealing performance : Square-bottom valve bags are excellent, with a self-sealing valve and no pinholes; flat bags are inferior, with numerous needle holes in the seams and a tendency to leak powder.

Filling efficiency : Square-bottom valve bags are very tall and can be fully automatically filled with a filling nozzle, achieving an efficiency of 800–1,200 bags per hour; flat-bottom bags are lower and require manual assistance or semi-automatic operation.

Warehousing and logistics : Square-bottom valve bags are excellent—brick-shaped and stackable in 8 to 10 layers; flat bags, on the other hand, are cylindrical and prone to rolling over or tipping sideways.

Applicable to automation : Square-bottom valve bags are perfectly compatible with fully automated packaging lines; flat bags require manual intervention or equipment modifications.

Procurement cost : Square-bottom valve bags are slightly more expensive, at approximately RMB 1.1–1.3 per bag; flat-bottom bags are lower in price, at about RMB 0.8–1.0 per bag.

X. Material and Craftsmanship

10.1 Structural Composition

Outer layer: Color-printed PP woven fabric (single-color printing)

Middle layer: PE film (moisture barrier, thickness approximately 5–12 μm)

Inner layer: PP woven base fabric (basis weight ≥ 65 g/m²)

Bag Type: Square-bottom valve bag (glue-sealed bottom bag)

10.2 Production Process Flow

Drawing → Weaving → Composite Molding → Gravure Printing → Valve Mouth Forming → Glue‑Back Bag Making → Hot‑Melt Adhesive Bottom Sealing → Finished‑Product Inspection

XI. Tensile Strength

Longitudinal tensile strength : ≥450 N/50mm (in accordance with GB/T 8946)

Zonal tensile strength : ≥450 N/50mm

Elongation at break : 15%~30%

Peel strength (composite layer) : ≥3.0 N/15mm

Safe Load Capacity : 25 kg

The hot-melt‑glued bottom achieves a tensile strength up to twice that of traditionally sewn‑bottom bags, with excellent tear resistance, effectively preventing bag rupture.

XII. Moisture-Proof Rating

Water vapor transmission rate (WVTR) : ≤15 g/(m²·24h) (GB/T 1037)

Moisture-proof effect : Under conditions of relative humidity ≤80%, the material can be guaranteed not to absorb moisture or cake within 3 months.

Upgrade Options : The PE film can be thickened to 80 μm, reducing the water vapor transmission rate to ≤5 g/(m²·24h).

13. Packaging Drop Test

Test Standard : GB/T 4857.5

Drop height : 1.2 meters

Fall order : Facade → Plan → Elevation (three sample bags tested separately)

Criteria for Determination : The bag body is undamaged, the contents are securely contained with no leakage, and it can effectively withstand accidental impacts during handling.

XIV. Applicable Filling Method

Filling equipment : Valve‑port‑specific packaging machines (screw‑type, pneumatic‑conveying, impeller‑type)

Filling process : Automatic bagging → Valve‑mouth docking → Automatic metered filling → Valve‑mouth self‑sealing → Conveying to the downstream line

Auxiliary equipment : Can be equipped with an automatic palletizer and a stretch wrapper.

15. Packaging Specifications

Applicable Net Content : 25 kg (the label in the image indicates 25 ± 0.5 kg)

Common sizes (tiled) : Length 63 cm × Width 51 cm × Bottom fold 11 cm

Bag type : Square-bottom valve bag (top valve opening)

Valve port type : Flanged type / Cylindrical type / Membrane type

Pallet packaging : Typically 200–300 bags per pallet.

16. Scope of Customization

Printed content : Brand logo, product name, instructions for use, recycling symbol, QR code, etc. (supports single-color或多-color)

Net Content Specification : Customizable from 15 to 50 kg

Bag body dimensions : Customized according to material density and customer requirements

Bag type : Upper valve port/Lower valve port, with or without a vent valve

Material : PP basis weight (45 ~ 80 g/m²), PE film thickness (5 ~ 80 μm)

Moisture-proof rating : Thickened PE film or an additional coating layer

Other features : Anti-slip embossing, one-way vent valve, easy-tear notch

Minimum order quantity Custom-printed bags typically require a minimum order of 5,000 to 10,000 units (some manufacturers may accept orders as low as 1,000 units).

XVII. Environmental Compliance

Product Standard : Complies with the national standard GB/T 28627-2023 “Plaster Gypsum”

Packaging Standards : Complies with GB/T 8946-2013 “General Technical Requirements for Plastic Woven Bags”

Ink Safety : Benzene- and ketone-free, compliant with GB 9685

Recyclability : Both PP and PE are recyclable materials, and some companies use recycled materials or biodegradable formulations.

Export Compliance : Complies with the EU Regulation No 10/2011 and the RoHS Directive, and can provide a certificate of inspection.

18. Price and Minimum Order Quantity

Price Reference (Monochrome Printing, 25 kg Square-Bottom Valve Bags)

Purchase quantity: 1,000–4,999 units; reference unit price: RMB 0.8–1.3 per piece (plate-making fee charged separately).

Purchase quantity: 5,000–19,999 units; reference unit price: RMB 0.7–1.0 per piece (plate‑making fee may be waived).

Purchase quantity: 20,000–49,999 units; reference unit price: RMB 0.6–0.9 per unit.

For purchase quantities of 50,000 units or more: reference unit price is RMB 0.5–0.8 per unit.

The unit price for the laminated moisture-proof version has increased by approximately RMB 0.1–0.3 per piece; additional costs apply for thicker PE film or the inclusion of an exhaust valve.

Minimum order quantity

Negotiable

XIX. Applicable Parties (Purchaser)

Lightweight plaster gypsum manufacturer

Dry-mix mortar and putty powder manufacturing enterprises

Building materials packaging traders and export enterprises

Brand owners requiring OEM contract manufacturing and packaging services

Medium- and large-scale powder-processing enterprises with requirements for automated packaging and moisture-proof performance.