How Packaging is Made
For a general overview of paper packaging production in Canada check out the flow chart above and in our Factsheet section which describes how packaging mills make board which is then converted into boxes, bags and cartons before being sold to industrial or residential consumers.
To begin the production cycle, you must first have pulp, either virgin, recycled, or a blend of the two. In Canada, we mostly used recycled pulp (old boxes and other used paper material collected from the back of factories, supermarkets and office buildings, and from curbside, apartments, and drop-off depots).
This used paper material or recovered fibre as the industry calls it, is baled and sent to a mill for pulping. It is here that it is transformed into the type of board or paper that the particular mill specialises in.
For example, a mill might specialise in linerboard or corrugating medium (or both) to produce what’s collectively called containerboard. Or it might specialise in producing boxboard or paperboard, or in kraft paper (to make paper bags and sacks).
Wherever the pulp has come from, the mill process is essentially the same. The pulp is dropped into what’s called a pulper, which acts like a big washing machine. Non-paper materials such as plastic, glass and metals are removed through a series of cleaning and screening processes. The paper fibres are then pumped onto a fast-moving screen to form paper or board. The rest of the process involves removing the moisture out of the paper or board so that it can be wound onto big rolls or cut into sheets.
These rolls and sheets are then shipped to what’s called a converter or a box plant. Containerboard is converted into corrugated boxes; boxboard or paperboard into boxboard or paperboard cartons; and kraft paper into paper bags or sacks.
There are many more converting facilities (box plants) than mills, dotted around the country so as to be closer to their customers. Converters print, slot, crease, fold and glue the board, and send it on to a packer or the customer to be filled with product. Any waste material from the converting process (such as corrugated cuttings or boxboard trim) is collected on-site and sent back to a mill for further recycling.
Making corrugated boxes
The board used to make a corrugated box is called containerboard. Two different layers of board are actually required to do this, linerboard and corrugating medium. Both are normally produced at the same mill location. Linerboard describes the top and bottom layers of the board and the medium is the wavy, ripple-like layer that gives the corrugated box its strength. Think of it as a sandwich: two layers (one top and one bottom) with the medium in the middle. Rip the edge of a used package. If it has a wavy layer of paper fibres in the middle, it is a corrugated box (with greater strength).
The linerboard and the medium are shipped from the mill to a corrugated converter who uses a piece of machinery called a corrugator to blend the medium and the linerboard together. Once blended, the combined sheet can be printed, slotted, creased and folded as noted above, then sent on to the customer or his packer to be filled with product.
The corrugated box is primarily used for the shipping of heavier products to factories and supermarkets but it is also widely used to deliver consumer goods such as appliances and electronics, and food and beverages. For further information on corrugated boxes see www.corrugatedboxescanada.org
Making boxboard cartons
The board used to make a boxboard or paperboard carton is called (surprisingly!) boxboard or paperboard. Most boxboard mills in Canada use 100% recycled pulp, as much as 60% of it being old corrugated boxes or containers (OCC). The other components are old newspapers, used printing and writing paper, and old boxboard (OBB) itself.
The same mill processes used in a containerboard mill (pulping and drying) are used at a boxboard mill, with the boxboard sent to a boxboard converter for printing and slotting and so on. The end result is the lighter weight carton used to deliver products such as breakfast cereals, shoes and toys. For further information on boxboard or paperboard cartons see www.paperboxescanada.org
Making kraft paper bags and sacks
There are two mills in Canada making kraft paper for later conversion into paper bags and sacks. They both primarily use sawmill residue as pulp. The rolls and sheets of kraft paper are sent to bag converters for printing and slotting etc. and then on to customers ready for filling. Kraft paper bags essentially come in two types: stronger industrial sacks containing things like flour and cement, and lighter grocery bags used at retail. For more information on kraft paper bags see www.paperbagscanada.org