Polythene

The Manufacturing Process

These are the three steps involved in making any plastic bag:

  1. Extruding Plastic Film
  2. Printing Bags
  3. Bag Making or “converting”

Blending and Mixing Resins

Clear LDPE (low density polyethylene) plastic resin in pellet form is vacuum fed from storage silos and blended with various additives as required for specific product applications. These mixes transform the plastic polymer to improve their basic mechanical, physical and chemical properties into a commercial product.Additives combine to create the desired proprietary blends of clarity, strength, stretchability, sealability, scuff and tear resistance, UV protection, bacterial protection, surface appearance, slip resistance and other properties required for the finished product.

If coloured film is to be made, coloured pellets (called “Master Batch”) are added in blends from 1% to 25% to achieve different opacities and virtually any colour imaginable.

Numerous resins, both LDPE and Linear LDPE, are kept in stock to allow for the many diverse applications that are manufactured daily.

Extruding Plastic Film

The blended resins are then fed into extruders and melted at 380ºF. Screw drives force the molten mixture through a precision die where air is introduced and a ‘bubble’ is formed. This process is known as “blown film extrusion”.Adjustments to wall thickness and diameter are made in this continuous bubble or tube. As it rises some 20 feet, it cools and is flattened and wound under tension into 50 – 200 lb. rolls.

Our line-up of extruders gives us the flexibility to regularly produce custom film orders. This allows also for quick order fulfilment where tubing may be available in as little as 2 or 3 days.

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Printing Bags

A smaller press does the less complex jobs such as produce roll bag printing and other 1 or 2 colour jobs.This versatility allows us to print small quantities of bags and also to handle huge press runs of a week or more. We can consistently meet deadlines while achieving consistent, quality results.From the extruders, the rolls of film are delivered to our print department. Flexographic stacked presses produce printed film in up to 10 colours with matte to gloss to metallic finishes.

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Bag Making or “converting”

Either plain rolls from the extruder line or printed rolls form our presses are delivered to the bag making area of our plant. A myriad of sizes and options are available in essentially 3 types of bag conversion: single bags, bags on rolls (perforated tear-off) or bags on wire wickets.

Roll stock is loaded onto bag making machines where repetitive bottom seal or side seal converting takes place to produce individual bags from the large rolls.Holes, vents, slits, perforations, handle punching, wicketting, header sealing and ziplocking are some of the many options available in each production run.

Special folding jigs allow for gusseting as required with high speed, automatic wire wicketting machines aligned for efficient production.

After the rolls of tubing are converted into one of many styles and types of bags, the bags are packed into boxes, stacked and wrapped on pallets in preparation for shipment.

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