ISO 3688 pdf download.Pulps — Preparation of laboratory sheets for the measurement of diffuse blue reflectance factor (ISO brightness)
1 Scope
This International Standard specifies two procedures for the preparation of laboratory sheets prior to measuring the diffuse blue reflectance factor (ISO brightness). One is the traditional procedure based on preparation of sheets in a Büchner funnel using a filter paper or a wire screen. ln the other procedure, the sheets are prepared in a standard sheet former (conventional or Rapid Köthen). Details of the subsequent measurement procedure are given in ISO 2470. It is applicable to all wood pulps and to most other types of pulp. Pulps with very long fibres, such as those made from unshortened cotton, flax and similar materials, shall be reduced to a suitable fibre length before testing by this method. This International Standard shall be used in conjunction with ISO 2469 and ISO 2470.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 2469:1 994, Paper, board and pulps — Measurement of diffuse reflectance factor. ISO 2470:— 1 ) , Paper and board — Measurement of diffuse blue reflectance factor (ISO brightness). ISO 5263:1 995, Pulps — Laboratory wet disintegration. ISO 5269-1 :1 998, Pulps — Preparation of laboratory sheets for physical testing — Part 1 : Conventional sheet- former method. ISO 5269-2:1 998, Preparation of laboratory sheets for physical testing — Part 2: Rapid-Köthen method.
3 Reagents
During the sheet preparation, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity, free from colouring matter and from iron and copper ions. NOTE Distilled water is used to ensure that the brightness of the sample is not affected by the water.3.1 Sodium hydroxide, (NaOH), approximately 0,1 mol/l solution, containing 4,0 g of sodium hydroxide per litre. 3.2 SuIfuric acid, (H 2 SO 4 ), approximately 0,05 mol/l solution, containing 2,8 ml of sulfuric acid ( ρ 1 ,84 g/ml) per litre, or acetic acid, w (CH 3 COOH) = 1 0 % containing 95 ml of acetic acid ( ρ 1 ,05 g/ml) per litre. 3.3 Retention aid to be used for recycled and non-wood pulps. Recycled and non-wood pulps may contain very small particles or fibres, with a colour deviating from the colour of the long fibres. They may affect the brightness value, but they will not be retained by a wire screen. If the brightness value of a pulp including these particles or fibres is to be measured, a retention aid shall be added prior to sheet forming. For example, an addition of 0,4 % of polyacrylamide to the recycled pulp sample has proved effective. The use, kind and amount of retention aid shall be stated in the test report.
4 Apparatus and auxiliary materials
All equipment with which the pulp comes into contact shall be of non-corrosive material, for example glass, porcelain, plastics and chromium-plated or stainless steel. Iron, copper, brass and bronze particularly shall not be used, since iron and copper ions have a strong tendency to cause colour reversion in pulp. Ordinary laboratory apparatus and the following. 4.1 Standard disintegrator, as specified in ISO 5263. 4.2 For sheet-making in a funnel 4.2.1 Büchner funnel or similar of non-corrodible material, the perforated bottom of which shall be flat, and having an internal diameter of 1 1 5 mm to 1 50 mm and a volume of 1 000 ml to 1 500 ml. The funnel is connected to a vacuum pump. 4.2.2 Filter paper, medium hard, fast filtering with a diameter of 1 1 0 mm to 1 50 mm to fit the funnel, and free from fluorescent materials and soluble impurities. Alternatively a wire screen, as specified in ISO 5269, can be used. The wire screen eliminates the difficulties in separating the sheet from a filter paper, a situation encountered when testing certain kinds of short-fibre pulp. However, there is a risk of losing some fine material, when using a wire screen. For most kinds of pulp, the brightness value is unchanged regardless of the filtering device, but for some kinds of mechanical or recycled pulp, the difference may be significant. Therefore, it is important that the apparatus and the filtering device used for the production of the sheets be reported. NOTE When sheets are formed on a filter paper, fine material may stick to the filter paper and may lead to uneven brightness of the sheet. In this case, the wire screen may be preferable. 4.2.3 Blotters, suitable for interleaving and for absorbing water pressed from the test sheets, grammage approximately 250 g/m 2 , and free from fluorescent materials and soluble impurities.