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The production process of pp woven bags

PP woven bag are products made of polypropylene and polyethylene resin as the main raw material, extruded and stretched into flat wire, then woven and bagged. Woven bags we must have seen, but do you know its production process? Here, let's find out.

History of the woven bag

In the 1930s, H. Jaeque invented a new technology for the production of cut filaments (flat filaments) and split film fibres through research into the stretching of polyvinyl chloride film;

In the 1950s, O. B. Rasmusse developed fibres for weaving using film extrusion methods and stretching equipment.

In 1965, Europe began industrial production of unidirectional stretch flat wire for the production of woven bags for industrial packaging.

PP Woven Bag Production Process  

PP woven bag production machine includes: drying mixer, drawing machine, winding machine, circular weaving machine, printing machine, bag cutting machine, sewing machine.

1. Raw material proportioning


According to the customer's requirements for quality, different ratios of raw materials can be used. If it is for food, the use of recycled materials is not allowed, and it is appropriate to add no more than 8% of filler masterbatch. In general, a maximum of 30-40% of recycled material should be added. Filler masterbatch should be added at 10-15%.

2. Drawing


This is a step where the heated polypropylene is drawn into a fine wire, the specific width of which is determined by the density of the woven bag required by the customer. Generally speaking, the width of the filament is between 10 and 15 filaments.

3. Woven Fabric


The yarn is drawn and woven into cloth by interlacing the warp and weft, a step that is usually done on a circular loom. Before the warp yarn enters the circular knitting machine, the warp yarn is crossed by means of a brown frame, and the weft bobbin moves in a circular motion through the warp yarn in the crossed opening to weave the fabric into a cylinder. The number of warp yarns entering the circular knitting machine is determined by the number of shuttles in the circular knitting machine.

In this production process, there are several indicators: weave density, width, tensile strength and weight per unit area of the woven fabric.

4. Film Coating


This step involves the lamination or coating of the woven fabric, the coating material and the paper or film to produce a cylinder or sheet fabric. The resulting cylinder cloth can be cut, printed and stitched to make ordinary sewn bottom bags, or perforated, folded, cut, printed and stitched to make cement bags.

5. Printing and cutting   


The qualified woven fabric will be printed on the woven fabric with product related information by printing machine, and then the bag cutting machine (cutting machine) will cut it to meet the size required by the customer.   

6. Sewing


The cut woven fabric is made into pp woven bag by a bag sewing machine.

In the national standard GB/T8946, the tensile load in the direction of the seam edge and the seam bottom is specified. The main factors affecting the strength of the stitching are the variety and type of stitching thread, the size of the stitching distance, the stitching, the size of the rolled or folded edge stitching to the bag edge, the way of cutting, etc.

Technical indicators of the knitting process  


  1. Weave density   

Woven density refers to the number of warp and weft yarns in a 100mm x 100mm woven fabric. National standards specify the density and density tolerance of woven fabric, commonly used woven fabric density is 36 × 36 / 10cm, 40 × 40 / 10cm, 48 × 48 / 10cm.


  1. Quality per unit area of woven fabric   

The weight per unit area of woven fabric is expressed in square metres of grammage, which is an important technical indicator of woven fabric. The grammage per square metre mainly depends on the warp and weft density and the thickness of the flat wire, which affects the tensile strength and load capacity of the woven fabric and is a major part of cost control for the manufacturer.  


  1. Woven fabric tensile load   

For woven fabric, can withstand the warp and weft of the two directions of the tensile load, said warp, weft tensile load.  


  1. Width   

A variety of woven fabric width directly affects the bag-making process. For the cylinder cloth, the width is indicated by the folded warp; the folded warp is equal to half of the circumference.  


  1. Handfeel  

PP flat silk woven fabric feels thicker, broader, coarser and stiffer;

HDPE flat silk knitted fabric is soft, lubricated and not dense;

The addition of calcium masterbatch to PP flat yarn gives it a firm feel; the addition of less HDPE to PP makes it softer.

If the flat filament is narrow, the weave will be flat and soft to the touch; if the flat filament is wide, the weave will have more folded filaments and a rough feel.  


In the production process of pp woven bag, the ratio of raw materials is to ensure that the product qualified basis, especially when it comes to food products, raw materials can not add recycled materials; drawing is the most critical link; weaving, printing and sewing is an important guarantee of product aesthetics, especially for food products, the printing requirements are higher.  


Throughout the production process, the technical parameters and indicators of each process have a direct link to the impact of product quality. The study of the impact of each technical parameter and indicator on product quality can better promote production, ensure product quality and improve the competitiveness of enterprises.