Valve paper bags (PVSE)
Pasted valve with sewn easy-open end. The standard for high speed automatic filling of powders.
View detailsProduct range
Multi-layer Kraft Paper Bags Manufacturer
Two to five ply kraft paper sacks manufactured in our own factory, with pasted valve, sewn open mouth or block bottom closures and optional PE, aluminium or PP laminated barriers. Built for flour, sugar, dairy powders, cement, chemicals and anything that has to run through an automatic filling line without dust escaping.
Click a thumbnail to change the view, or the photo itself to enlarge it.
Paper sacks, engineered ply by ply
A multi-layer paper bag is not one sheet of paper folded into a sack. It is a ply structure: two to five layers of kraft paper, each with a job, glued into a tube and closed with a pasted, sewn or block bottom. The plies share the load, the inner ply can be coated or laminated, and the outer ply carries your print.
That structure is why paper sacks remain the standard for flour, milk powder, cement and chemicals. They present a flat, printable face; they hold a precise fill weight; they run at high speed on automatic filling lines; and they are made from a renewable material that many of your customers now expect to see on the shelf.
UnisunPack produces multi-layer paper bags in natural kraft brown or bleached white, in any size, with the ply count and barrier layer specified against your product. If you are switching from woven bags to paper, or from paper to woven, we will tell you plainly which one suits your product better.
Features and options
- 2 to 5 plies of virgin kraft paper, natural brown or bleached white
- Pasted valve (PVSE), pasted open mouth (PBOM), sewn open mouth (SOM) and block bottom
- Pinch bottom and pasted flat bottom constructions
- PE film, aluminium foil or PP laminated inner plies for barrier and strength
- Grease resistant inner ply where required
- Flexo printing up to 6 colours, with excellent detail on paper
- Anti-skid treatment for pallet stability
- Micro perforations for products that must release moisture
- Ideal for fully automatic filling and closing lines
- Custom sizes, gusseted or pillow style
- Food grade and UN certified constructions available
- Renewable, recyclable paper based packaging
Closure types
Sewn open mouth paper sacks
Filled from the top and closed with thread. Flexible fill weights, low tooling cost.
View details
Block bottom paper bags
A folded block base so the bag stands upright. Best print face and shelf presentation.
View detailsTypical specification
| Plies | 2, 3, 4 or 5 ply, specified from fill weight, product density and stacking. |
|---|---|
| Paper grammage | Commonly 70 to 90 gsm per ply, natural kraft brown or bleached white. |
| Bag capacity | 5kg to 50kg. 25kg and 50kg are the most common export sizes. |
| Closure | PVSE pasted valve, PBOM pasted open mouth, SOM sewn open mouth, block bottom (SOS), pinch bottom. |
| Bottom | Pasted, sewn or block bottom. |
| Barrier options | PE film lamination, aluminium foil laminate, PP lamination, grease resistant ply, moisture barrier coating. |
| Printing | Flexo printing up to 6 colours. |
| Standard sizes | 25kg 500 × 800mm · 50kg 550 × 900mm · custom dimensions to your filling line. |
| Certification | Food grade and UN certified constructions on request. |
| Packing | Palletised and stretch wrapped, or bales on request. |
| MOQ | Low minimum for a first order — ask us for your size. |
| Lead time | Around 2 weeks for stock constructions, up to 25 working days for fully customised bags. |
What multi-layer paper bags are used for
- Flour, semolina and bakery mixes
- Sugar, icing sugar and confectionery ingredients
- Milk powder and dairy ingredients
- Cement, gypsum, mortar and dry mix construction products
- Tile adhesive, wall putty and plaster
- Chemical powders, resins, pigments and additives
- Pet food, bird food and aquatic feed
- Seed, grain and pulses
- Starch, cocoa and dehydrated ingredients
- Animal feed concentrates and premixes
If your product is a fine powder and your market expects a paper pack, this is usually the right family. If it needs to survive rough manual handling and the cheapest possible cost per tonne, compare with PP woven bags.
How a paper sack is made
1
Paper roll selection
Kraft paper rolls are selected by grammage, colour and barrier requirement.
2
Printing
Flexo printing of the outer ply with your artwork, up to 6 colours.
3
Lamination and ply assembly
Plies are glued together, with a PE, foil or PP barrier layer where specified.
4
Tube forming and cutting
The ply structure is formed into a tube and cut to the bag length.
5
Bottom forming
Valve, pasted, sewn or block bottom is formed, with the valve patch for PVSE bags.
6
Inspection and packing
Bags are counted, inspected against specification, palletised and stretch wrapped.
Multi-layer paper bag FAQ
What does multi-layer mean, and how many plies do I need?
Each ply is a separate paper layer glued together, and the plies share the load. A light retail sack might be two plies; a 25kg cement or fertiliser bag is typically three or four plies, and a heavy-duty chemical bag can be five. The right number depends on the weight per bag, the drop height in your warehouse and how the bag will be stacked. We usually start from the product and the filling line, then specify plies, paper grammage and any intermediate liner.
What is the difference between PVSE, PBOM, SOM and block bottom?
PVSE is a pasted valve bag with a sewn easy-open end — filled through the valve and opened along the sewn edge. PBOM is a pasted bottom open mouth bag, filled from the top. SOM is sewn open mouth, closed with thread after filling. Block bottom (also called SOS, self opening sack) is a folded block base that lets the bag stand up on a shelf. Valve closures suit fast automatic filling of powders; open mouth constructions suit granules, seed and products filled by weight.
Can kraft paper bags be used for liquids or greasy products?
Not as plain paper. For greasy, moist or aromatic products you need a barrier layer inside the paper structure — PE film, aluminium foil or a laminated ply — plus a grease-resistant inner ply where required. Tell us the product and we will build the ply structure around it.
How are kraft paper bags printed?
Usually by flexo printing, which on paper gives noticeably better detail and colour depth than printing on woven fabric. Up to 6 colours is normal. Because the face is flat and untextured, paper is the better choice if your artwork contains fine text, regulatory information or ingredient panels.
Do kraft paper bags need special handling in the warehouse?
Paper loses strength when it takes up moisture, so the bags should be stored on pallets, off the floor and away from damp walls. For humid destinations we recommend a moisture barrier liner or PE coating. In transit, bags are palletised and stretch wrapped as standard.
Customer print work
Kraft paper bags from our production
Click any bag to enlarge it. Flour, sugar, cement, resin, feed additive and charcoal bags, all printed and converted in our factory.
Construction detail
How the closures differ
Sewn open mouth, block bottom, pasted open mouth, and the multi-ply interior of a 25kg food bag.
Related products
You may also need
Valve paper bags (PVSE)
The standard paper sack for automatic high speed filling of powders.
View details
Barrier and liner options
PE, aluminium and PP laminated barriers built into the ply structure.
View details
Let's talk packaging
Get your multi-layer paper bag price today
Send the product, fill weight, closure type, number of print colours and quantity. We will come back with the ply structure, the price and the lead time.
- Emailsales@unisunpack.com
- Tel / WhatsApp+86 15825665852
- FactoryWenzhou, Zhejiang Province, China 325000
- Response timeWithin 24 hours, Monday to Saturday
