A vacuum pouch looks like the simplest thing in a food business. Two layers of clear film, sealed on three sides. Getting it from a sack of plastic pellets to a box of 1,000 identical bags is four stages, and each one is where a cheap pouch goes wrong. This is how it's done at our Haslingden site.
Stage 1: co-extrusion
The raw material arrives as pellets: polyamide in one silo, polyethylene in another, plus a tie resin that bonds them. Each polymer is melted in its own extruder, a heated screw that turns pellets into a thick liquid at around 200 to 260°C depending on the polymer. The melts are fed into a single die where they meet as separate layers and come out together as one film. That's co-extrusion, and it's why a PA/PE pouch has no glue in it. The film guide explains what each layer does.
On a blown film line the die is a ring, and the melt comes out as a tube that's inflated with air into a bubble several metres tall. The bubble cools as it rises, is flattened at the top, and is wound onto a reel as a layflat tube. Thickness is controlled by how fast the film is pulled away from the die and how much air is in the bubble, and it's measured continuously; a 65 micron film has to be 65 micron all the way round or the pouches from one side of the reel will seal differently from the other.
This is the stage most pouch sellers don't do. They buy reels. Flexipol runs extrusion at Haslingden, which is what lets us say what's in the film and change it when a customer needs something different.
Stage 2: slitting and printing
The master reel is wider than any pouch. It's slit into narrower reels matching the pouch widths, so a 200mm pouch comes off a 200mm reel and there's no trimming later. For printed pouches, this is also where the print goes on, before the film is made into bags. Plain pouches, which is the whole online range, skip that step.
Stage 3: bag-making
The reel feeds a bag-making machine that does two things over and over: seal across the film to make the bottom of one pouch and the top edge of the next, and cut between them. For a layflat tube that's one seal per bag; for flat film folded over, it's a side seal as well. The seal is made by a heated bar at a set temperature, pressure and dwell time, and those three numbers are what a good bag-maker watches all shift. Too cool and the seal peels; too hot and the film thins at the seal line and splits under vacuum.
The finished pouches are counted into boxes, 1,000 for most sizes and 500 or 400 for the large formats, and the box carries the batch number that ties it back to the reel and the extrusion run.
Stage 4: the checks
Between the stages, and on the finished pouch, the quality checks are what a BRC audit looks at:
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Gauge: film thickness measured across the web and logged.
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Seal strength: sample pouches pulled apart on a tensile tester to confirm the seal is stronger than the film.
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Dimensions: width and length against the spec, because a 200mm pouch that's 205mm won't fit a 220mm seal bar with margin.
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Vacuum test: filled pouches run on a chamber machine and held to confirm they stay tight.
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Foreign body and hygiene controls across the site, which is the part of the audit that has nothing to do with the film and everything to do with whether it's fit to touch food.
The site holds BRC Global Standard for Packaging Materials at AA, the top grade. The BRC guide covers what that involves.
Why any of this matters to a buyer
Three things follow from making the film rather than buying it. The spec is known, so the pouch you get in March seals like the pouch you got in January. A problem can be traced to a reel and a run in an afternoon rather than a phone call to another country. And a customer who needs something different, a thicker gauge, a colour, a print, is talking to the people who can change the recipe. The buying direct guide covers the commercial side.
Want to see the film before you buy? A free sample pack comes from the same line as the boxes.
