FI61926B - FOERFARANDE VID OXONBEHANDLING AV PAPPERSMASSA - Google Patents

Description

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Patent · and Register Office * / 44) Date of NihUvikalpano and kuall | -

Patent- och regicterttyrelsen 'An * 6k * n utlagd oeh utl.skrtfnn publkcrad 30.06.82 (32) (33) (31) Privilege claimed— Bejird priorltet OU .10.73 Norway-Norway (NO) 3859/73 (71) Papirindustriens Forskningsinstitutt , Forskningsveien 3, Oslo 3,

Norway-Norway (NO) (72) Franqois Andr £ Abadie-Maumert, Oslo, Sigurd Hauan, Oslo, Vidar Loräs, Hosle, Arne Nicolai Soteland, Oslo, Norway-Norway (NO) (7 * 0 Berggren Oy Ab (5M Method The present invention relates to a process for the production of ozonated pulps by subjecting the pulp to ozone treatment as part of a continuous refining process.

It has been known in the past that treating both mechanical and chemical pulps with ozone can significantly improve their properties. Accordingly, Applicant's Patent No. 115,279 and N. Soteland and K. Kringstad, Norsk Skogindustri Nos. 2, 46 (1968) and N. Soteland, Norsk Skogindustri Nos. 3, 61 and 5, 135 (1971) disclose a method for determining the whiteness of lignin-containing pulps. and to increase the strength by subjecting them to ozone treatment in an organic solvent to which water may have been added. Applicant's Norwegian Patent No. 128,074, which has been published, further discloses a method for reducing the resin content of a pulp and its risk of precipitation by treating the pulp under acidic conditions with a certain amount of ozone, 2,61926, which is insufficient to achieve a substantial bleaching power or strength increase.

Although said known ozone treatment can be carried out on pulps with a wide consistency range, the best results are obtained with a "ground" pulp having a consistency of between 15-60%, preferably between 25-40%. In order to obtain such a "ground" pulp, the pulp is usually first dewatered by means of a suitable pressing device and then subjected to a so-called pulp rubbing. However, the mentioned work steps require special and expensive equipment.

In recent years, the defibering or grinding of high-consistency pulps with the help of plate refiners has become increasingly widespread in the pulp industry. Examples include the production of mechanical, thermomechanical, semi-chemical and high yield pulps. In the grinding or defibering of said pulp types, it is possible to obtain a pulp suitable for the ozone treatment according to the invention by using most known plate refiners, namely a so-called pulp with a particularly suitable consistency and a favorable physical state. "rubbed" fluffy mass.

It has been an object of the present invention to eliminate the above-mentioned expensive specially constructed apparatus. The invention therefore relates to a process for treating paper pulp, such as mechanical, thermomechanical, semi-chemical or chemical pulp, with ozone, the pulp being treated with an ozone-containing gas at a density of 15-60%, preferably 25-40%, and the invention is characterized by that the pulp is refined in one or more stages in a plate mill to a consistency of 15-60%, after which the pulp is directly treated with ozone in a gas phase reactor. The pulp is then fed from the plate refiner, possibly e.g. in a heat exchanger after cooling to achieve the most favorable pulp temperature for ozone treatment, immediately and continuously to a gas phase reactor where the pulp is ozone treated.

3,61926

The gas phase reactor may have a structure known per se, e.g. as disclosed in the Norwegian patent application No. 2068/72 of the applicant of this patent.

After the ozone treatment, the pulp can, if desired, be subjected to some other mechanical or chemical treatment, such as grinding, homogenization, bleaching, pH adjustment, etc. In these refining steps following the ozone treatment, which can be carried out using a lower pulp consistency, homogenization of the ozone-treated pulp, among other things, is achieved, and good contact between the chemicals and the pulp is achieved by chemical treatment of the pulp, e.g. bleaching. In the event that the ozone treatment is not followed by refining steps, the dilution of the pulp is possibly carried out in connection with the pH adjustment.

The invention will now be explained in more detail by means of the following examples.

Example 1

The spruce chips are defibered in a plate refiner in two stages, so that the whiteness of the mechanical pulp obtained after the second stage is 63% SCAN and the consistency 25%. The pulp is immediately fed to an ozone reactor, where the pulp is continuously treated with 2% ozone. In this case, the strength properties are improved to such an extent that the pulp can replace the share of thermomechanical pulp or partly chemical pulps in wood-containing paper grades. In the post-ozone process, the pulp is refined to a consistency of 18%, while adding the necessary peroxide-based bleaching chemicals to increase the whiteness to 73% SCAN.

Example 2

After the thermomechanical process, the spruce chips are defibered in one operation with a pulp consistency of 35%. After cooling in a heat exchanger, the pulp is immediately fed to an ozone reactor where it is continuously

Claims (1)

4 61926 is ordered with 1% ozone. In this case, the strength properties of the pulp are improved to such an extent that the pulp can completely or partially replace sulphite or sulphate pulps in wood-containing paper grades. After ozone treatment, the pulp is refined in two stages, the first of which is performed to homogenize the pulp at a pulp consistency of 22%, the second step to achieve the desired CTF value (CTF = Canadian Standard Freeness) at a pulp consistency of 12%. Example 3 Unbleached softwood sulphate pulp with a kappa number of 50 and a consistency of 25% is refined in one operation in a plate refiner, after which the pulp is continuously fed to an ozone reactor where it is treated with 2% ozone. After extraction with base, a pulp with a kappa number of 10 is obtained, which can be further bleached in the customary manner, if desired. Example 4 Washed chips from a high yield pine sulphite cooking process are defibered in a plate refiner in one operation with a pulp consistency of 30%. The pulp is then continuously fed to an ozone reactor where it is treated with 0.3% ozone. In this case, the total amount of resin, and in particular the amount of harmful resin, is reduced to a level acceptable for driving the pulp in the paper machine. After the ozone treatment, the pulp is possibly diluted during pH adjustment before being fed to the pulp system of the paper machine. Process for the treatment of paper pulp with ozone, such as mechanical, thermomechanical, semi-chemical or chemical pulp, the pulp being treated with an ozone-containing gas at a consistency of 15-60%, preferably 25-40%, characterized in that the pulp is refined in one or more stages in a plate mill at a consistency of 15-60%, after which the pulp is directly treated with ozone in a gas phase reactor.