Production processes of cellulose acetate rayon

  The production process for cellulose acetate rayon fiber :

The production process for cellulose acetate rayon fiber processing steps are elaborately discussed below : 

1. Cotton linters and wood pulp purification: First of all to purify cotton linters and wood pulp need to keep in a kier boiler at a controlled atmospheric pressure with alkaline liquor or caustic soda or both of these mixtures for 4 to 6 hours. After that need to wash. Again we need to do bleaching by hypochlorite bleaching and wash off then dry.

2. Pretreatment: Above mentioned purified cotton linters and wood pulp need to be sunk under glacial acetic acid at a controlled temperature. 

3. Acetylation: Above processed pretreated cotton linters and wood pulp need to keep in a closed vessel with the below chemicals. The vessel has a strong vibrator. 

Purified cotton linters: 100 lbs 

Acetic anhydride: 300 lbs 

Glacial acetic acid: 500 lbs 

These tree chemicals need to mix in good condition and there will not be any chemical reaction. After fine mixing needs to add 8-10 lb heavy concentrated sulphuric acid. In a circular tank with the top covered tank complete acetylation. After entering the mixture we need to seal the tank. The stirring has a blade and it starts to move and also starts an acetylation reaction. This time temperature of the tank needs to keep less to save the cellulose from decomposing. Around the tank need to flow cold water to keep the temperature below 20°C. Slowly the acetylation process is complete. The acetylation process continues for up to 8 hours and cellulose makes triacetate cellulose also known as primary acetone. This makes it bright and viscose. 

4. Hydrolysis: In hydrolysis reaction need to dissolve primary acetone to secondary acetate. After that, some additional acetic acid and water anhydride react for up to 24 hours at high temperatures. Here acid is hydrolysis and makes acetone solution. Then full mixture takes in water and collects precipitated.  This precipitate is cellulose acetate and its degree of polymerization is 350 to 400. Again it separates and washes then dries at low temperature. 

5. Dope preparation: Blended secondary acetate is mixed with a 3times acetone and kept in a closed vessel. Acetone dissolves secondary acetate and it takes 24 hours to dissolve fully. During this period need to add titanium dioxide to reduce brightness and if necessary can add color pigment also. Cellulose acetate in acetone is called dope. Then filter the dope and before spinning take it to a feed tank. 

6. Spinning: Dissolved state cellulose acetate may spin in dry spinning. In this spinning process filament come out throughout the spinnerette and here need hot airflow. Dope send to a spinning cabinet from the feed tank. The spinning cabinet has a spinnerette and through this dope, the solution comes out at high pressure. Generally, every spinnerette has a definite number of hole in it. After spinnerette, the filaments come up 2 to 5 meters then to the feed roller. The spinning cabinet air temperature is 100°C. By this temperature, the filament removes vapor and the filaments be strong and through the feed roller and guide roller yarn spin in the bobbin.