• Raw Material
  Paper is made of all sort of things you can think of:
   

  • Soft Wood - Like spruce & pine which have a long fibre
     
  • Hard Wood - Short Fibre. Not very suitable for paper making. Gives trouble in barking and chipping. Eucalyptus, Acacia, Albizzia & wattle trees are more suitable hard wood trees for paper making and do have a very high rate of growth
     
  • Grasses - Several types of long grasses like bamboo sabai grass, sarkanda etc. are used
     
  • Straws - In India rice, wheat straw, bagasse and corn straw are used for paper pulp making. Straw has been reported as suitable for paper making
     
  • Cotton Linters - Its a seed hair from cotton plant after extracting cotton. Only small proportion of raw cotton in form of short fibre linters comes directly to paper mills
     
  • Cotton Rags - This gives more strength in paper or paper board
     
  • Linen - Linen fibre is derived from the bast tissue of the stem of the flax plant, cultivated extensively in USA, Russia, Hungary, France, Belgium & Ireland
     
  • Hemp - It comes to paper maker in the form of spinning waste, twine, cordage, ropes etc. Hemp is the bast tissue of an annual shrub growth extensively found in India, Russia & America
     
  • Manila - Fibre occurs in the leaves of a plant of the plantain family that grows in the Phillipines Islands
     
  • Sisal Hamp - The fibre comes from the leaves of the plant Agave Sisalana and is used for making rope & twine
     
  • Waste Paper - The demand of waste paper for manufacturing of paper is increasing every day. Utilization of this would reduce load on demand of fresh fibres. About 80% of the waste paper is used in the manufacture of paper boards. Small scale units depend almost entirely on waste paper as raw material. In India the use of recycled fibre is only 20 percent compared to 40% in developed countries.



• Chipping
  Chips arrive by truck and are unloaded at the factory and sent for pulping..



• Pulping
  It is obtained by removing lignin and other impurities from the wood & other raw materials used by a cooking process (Lignin is the glue that holds the fibers of the wood in three form). The cooking process requires wood bamboo or other raw materials chips. The chips are loaded into a digester and a cooking liquor is added. Then by pressure cooking, the wood bamboo or other fibers are separated from other unwanted ingredients. Either batch digester or continuous digesters are used in cooking.
  
  The chips and liquor are mixed as the chips are pumped to the top of the digester. The top section of the digester is pressurized to 160 psi and more. As the chip mass passes downward the cooking liquor penetrates the chip. After about 45 minutes or more as per raw material the chips have to be passed through the impregnation zone where hot liquor (340 degree F) is circulated through the chips for heating. The actual pulping occurs at 355 degree F in about 90 minutes, a period known as the cooking period. After passing through the cooking zone, the chips (which have not become pulp) are washed with weak liquor from washing stages that follow.
  
  Within the chemical process there are two types:

  • Sulphate Process "(Alkaline process)"
  • Sulphite Process "(Acid process)"

  Some hard woods may be dissolved with difficulty by the sulphite process. On the other hand, the sulphate process most of the chemicals are recovered and reused.




• Bleaching
  Although cellulose fiber is white in colour, due to residual lignin traces remaining on the fibers, the pulp appears creamish. Therefore, to manufacture white paper we need to remove yellowness without physically or chemically damaging the fiber, with improvement in various properties. So the main objectives of bleaching the pulp, can be set out as follows.
  
  To increase brightness of the pulp by removal or modification of some of the unwanted elements in the unbleached pulp. These deleterious elements are lignin traces, resins, metal ions, non-cellulosic carbohydrates etc.
  
  Bleaching for brightness improvement should also help to keep the pulp stable without turning yellow or lose strength or reduce brilliance - due to aging.
  
  To lower viscosity of the pulp for optimum flow, during subsequent operations.
  
  Bleaching also should help to reduce the fiber bundles, shives and bark fragments.
  Bleaching should be done with minimum mechanical action of fibers, while dissolving lignin and other unwanted residuals.
  
  Bleaching Pulp is normally done in a step-wise sequence using different chemicals and process conditions at each stage, with washing in between stages.



• Additives
  Additives are added to paper pulp. Addition of fillers like clay & calcium carbonate is very common & besides acting as fillers they add brightness to the paper. These additives must be finely ground. Additives like dyes & pigments are also added. Other fillers are Titanium Dioxide, Barium Sulphate & Zinc Sulphide.



• Removing Water
  Removing water is the next important stage. For this the pulp is passed through a rapidly moving wire mesh called fourdriner. The objective is to recover 93 to 95% of the water in the finished paper.
  
  As the paper flows along the wire mesh and water is drained along the way, a dandy roller near the end helps to smooth out the paper. The dandy roller will improve the formation of the paper web by application of pressure. When the paper reaches the end of the wire mesh it is transferred to a felt blanket which conveys it through many steam heated driers to remove the excess moisture. In the process the paper gets some glaze like coating also. Then it is made to pass through a series of calendar stacks. The calendars are series of polished iron rollers stacked one on top of the other, through which the finished paper will pass to smoothen down.
  
  The next step is rewinding on a metal or fibre core. The last stages after this are sheeting, packing & testing.



• Final Product
  The above processes when complete, gives us the final product.

For more information Contact Us.