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BS ISO 21993:2020 pdf free

BS ISO 21993:2020 pdf free.Paper and pulp – Deinkability test for printed paper products
After storage the stock samples shall be diluted to a stock concentration of about 1 % to terminate any relevant chemical reaction before the treatment continues. For dilution of the un-deinked pulp sample use tap water. For dilution of the pulp sample to be deinked, use dilution water (7.3.2) with a temperature of (45±2) °C.
Measure the pH. At flotation concentration it should be equal to or higher than 7,5, provided that the defined range of the pH after pulping is met. If the pH before the flotation is below 7,5, discard the sample and repeat the test with a higher dosage of sodium hydroxide.
Start the flotation before preparing the un-deinked pulp specimens.
Heat up the cell with hot water. Pre-heat the cell with hot water close to the process temperature and then discard the water used for heating and add some of the prepared dilution water (7.3.2) of (45±2) °C to prevent the “concentrated” pulp from subsequently staying in dead corners. Determine the quantity of diluted sample required for the flotation cell used (see Annex B) and add it into the flotation cell. Add the required amount of dilution water to achieve a stock concentration of 0,8 % and proceed according to the manufacturer s instructions. The starting point for the flotation time is at which the air is introduced.
Parameters for some flotation deinking cells are available in Annex B. Set the flotation time accordingly.
If the cell is not listed in Annex B, set the stock concentration to 0,8 % at the beginning of the flotation,  set the temperature to (45±2) °C and the flotation time to a value when the status of hyper-flotation is reached. The state of hyper-flotation is defined by a maximum increase of luminance of 0,3 points per minute. This shall be determined for each cell type by using a mix of printed paper products (50 % newspapers, printed with coldset offset, 25 % magazines on SC paper and 25 % magazines on LWC paper, both printed with the heatset offset process) and following the procedures described in this document.
Determine the amount of the oven-dry overflow according to ISO 4119, and use this amount to calculate the overall yield and the fibre yield of the flotation. If the fibre yield is below 65 %, repeat the test with a shorter flotation time.BS ISO 21993 pdf download.

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