Block Bottom Paper Bags
A multi-layer kraft sack with a folded and pasted block base, so the empty bag stands upright on the filling line and the filled bag sits square on the pallet. The construction for flour, milk powder, sugar, chemicals and anything that has to look right on a shelf as well as survive a container.
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What the block bottom actually does
A block bottom bag is built from a flat paper tube with the base folded inward on both sides and pasted into a rectangular block. That fold is why the bag behaves differently from a simple flat or sewn sack: the base opens into a square footprint, the bag stands up on its own before it is filled, and the four side panels stay flat and parallel instead of rounding out as the bag fills.
The practical results are a stable pallet, a straight-sided pack that stacks without leaning, and two flat, uninterrupted print faces totalling far more printable area than a pillow bag of the same capacity. On a high speed line, the square base also locates the bag in the filling cradle far more reliably, which is why block bottom sacks are the default for automated powder filling.
- 2 to 5 ply virgin kraft paper, brown or bleached white
- Folded and pasted block base; pinch bottom on request
- Stands upright before filling, stacks square after filling
- Flat side and front panels for high coverage printing
- PE film, aluminium foil or PP laminated barrier plies
- Flexo printing up to 6 colours
- Suitable for automatic filling and closing lines
- Food grade and UN certified constructions available
Typical specification
| Plies | 2 to 5 ply, specified from fill weight, product density and stacking height |
|---|---|
| Bag capacity | 5kg to 50kg; 25kg and 50kg are the most common export sizes |
| Bottom | Folded and pasted block bottom (standard), pinch bottom on request |
| Top | Open mouth for sewing or tape closing, or valve top on request |
| Paper | Virgin kraft, natural brown or bleached white, 70 to 90 gsm per ply |
| Barrier | PE film, aluminium foil or PP laminated inner ply; grease resistant ply available |
| Standard sizes | 5kg 300 × 500 × 100mm · 10kg 350 × 600 × 110mm · 25kg 450 × 750 × 120mm · 50kg 550 × 900 × 140mm · custom to your line |
| Printing | Flexo up to 6 colours, two sided |
| Packing | Palletised and stretch wrapped, or bales |
FAQ
Will a block bottom bag run on my existing filling line?
Usually yes, and often better than a flat bag, because the square base locates in the filling cradle. Tell us the machine make and model, the nozzle or auger diameter and the fill weight, and we will confirm the base dimensions and the mouth opening that suit it before any plate is made.
Is a block bottom bag stronger than a sewn bottom sack?
The strength comes from the ply count and the paper grammage, not from the base style. A pasted block base spreads the load across the whole folded area rather than along a stitch line, which is why it holds up well under repeated pallet handling, but a 4-ply sewn sack is still stronger than a 2-ply block bottom. We specify from your load, not from the construction name.
Can it be supplied with a liner or a barrier ply?
Yes. PE film, aluminium foil and PP laminated plies are all available, and a separate loose or sewn-in PE liner can be added for products that need a fully sealed inner layer. Tell us the moisture or oxygen sensitivity of the product and we will propose the ply structure that covers it.
Get your block bottom paper bag price today
Send the fill weight, the product, your filling equipment and the quantity. We will come back with the ply structure, the base dimensions, the price and the lead time within 24 hours.
- Emailsales@unisunpack.com
- Tel / WhatsApp+86 15825665852
- FactoryWenzhou, Zhejiang Province, China 325000
- Response timeWithin 24 hours, Monday to Saturday
