FI59444B - FOERFARANDE FOER BEHANDLING AV MECHANICAL MASSOR OCH / ELLER AV DESSA FRAMSTAELLDA PRODUKTER - Google Patents

Description

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Norway-Norway (NO) 7 ^ 3286 (71) Papirindustriens Forskningsinstitutt, Forskningsveien 3, Oslo 3,

Norway-Norway (NO) (72) Nicolai Soteland, Oslo, Norway-Norway (NO) (7 * 0 Berggren Oy Ab (54) Method for treating mechanical pulp and / or products made from it - Förfarande för behandling av Mekaniska massor och / eller This invention relates to a process for the treatment of mechanical pulps and / or products made therefrom.

"Mechanical pulps" is a general term for types of pulp obtained by mechanically defibering different types of wood, for example with grinding stones or disc cleaners, possibly after a slight chemical treatment.

Because mechanical pulp is a relatively useful product compared to cellulosic pulps obtained by chemically dissolving wood, these pulps have achieved widespread use as raw materials in the manufacture of newsprint, magazine paper and the like. However, because the grinding mass shows that it has its harmful property. that it tends to "self-adhesive" during storage, it has previously been necessary to store and transport the mechanical mass in a humid state, or to dry it to a certain amount, for example, using the so-called "sudden drying method". As a result of "self-adhesion" / m 2 5 94 4 4 the mechanical pulp after storage shows more or less hydrophobic properties, depending on the storage time, resin content, storage conditions, etc., which tends to make further processing of the pulp difficult, e.g.

Due to the self-adhesive nature, mechanical pulp has been used only to a small extent for absorption purposes, for example in baby nappies, women's bandages, tampons, towels and the like, for which almost exclusively highly bleached cellulose species have been used.

If the resin can be removed from the mechanical pulp, it has been found that the mechanical pulp can also be advantageously used for the above-mentioned purposes, as described in Norwegian Patent No. 124,193 · According to this patent, the resin can be removed from the pulp, for example by extraction with acetone. . However, the industrial extraction process is a relatively complex and expensive process that requires large investments in extraction equipment, recovery equipment, etc. Acetone extraction of mechanical pulp has also been previously proposed to improve the strength properties of mechanical pulp and make the pulp easier to handle in a later processing process. 6? T 431, 1966).

It has now surprisingly been found that it is possible to treat mechanical pulp in such a way that it retains its wetting properties during aging, so that the mechanical pulp treated according to the present invention remains moist in storage and thus easy to handle in subsequent processing. In addition, this pulp has been shown to be very suitable for absorption purposes, despite the fact that the new treatment has only a small effect on the resin content of the mechanical pulp.

The new treatment method involves impregnation of the mechanical pulp with a buffer which buffers in the pH range 6-10, more suitably in the pH range 7-9 · Suitable buffers are, for example, alkali metal and ammonium salts of phosphoric acid, carbonic acid, citric acid, tartaric acid and the like. The buffer is more suitably added to the mechanical pulp as an aqueous solution in an amount of at least 0.2%> more suitably 0.5? or more of the dry weight of the pulp.

3 59444 Such treatment of mechanical pulp with an aqueous buffer solution is quite inexpensive and simple to perform. The addition of the buffer can take place in several different stages of mechanical pulp production, depending on the area of use of the product and the equipment available. The addition can take place, for example, during pulping in a refiner or grinder, in post-water systems of a paper machine, in gluing, in spraying during or after sheet formation, with spraying into the pulp possibly forming pulp spheres. The new treatment can therefore be carried out with available equipment and can be applied to existing production facilities. For example, the new method can be used to produce absorbent materials from mechanical pulps, which means substantial savings compared to highly processed cellulosic products. In terms of its potential and environmental impact, this method has very significant advantages.

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The invention will now be explained by the following examples, which show the effectiveness of the new treatment. j

Different types of pulp were treated with buffer either by spraying with buffer solution or by dipping in solution. The dry matter content of the pulps before treatment ranged from 25% to 90%. After treatment, the pulp was dried in a cyclone and triturated (Wenneberg mill). .

Part of the buffer-treated and ground pulp in this way

was heated at 105 ° C for 1 hour, after which the pulp was allowed to stand for 30-60 minutes at room temperature before the water absorption of the heated pulp was determined. The water absorption of the unaged mass r and the untreated mass was also determined. P

The determination of the water absorption rate was performed in these experiments as follows, f. .f that 10 g of air-dry ground pulp was spread evenly on a metal mesh (a metal basket measuring 7 cm x 20 cm x 1 cm) placed in a container containing 200 ml of water. The time it takes f. i from the placing of the metal mesh in the tank until the pulp is completely wetted, Γ is a measure of the water absorption rate of the pulp. f i

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Claims (2)

5,54444 As can be seen from the above results, the treatment according to the present invention achieves a significantly better water absorption rate compared to the untreated pulp. The exception, however, is borate buffer, which has a clearly reducing effect on the rate of absorption in relation to the unaged mass, but after aging the mass treated with borate buffer shows a higher absorption rate than the untreated mass. It further appears that the rate of water absorption of pulps treated with other buffers is hardly affected by thermal aging at all, as the 1 second difference is likely to be within the error limits of the test method in question. V By way of comparison, highly processed cellulose under similar conditions shows a rate of water absorption of the order of 5 seconds. Thus, the mechanical pulps of this invention are comparable in their water absorption rate to highly processed cellulosic pulps, and furthermore, because they retain their wetting properties in aging, they can easily be subjected to possible further processing, for example in a paper mill using mechanical pulp as a raw product. The invention also comprises an absorbent medium for use in baby diapers, sanitary napkins, tampons, towels and the like, which medium is characterized in that it is formed by a mechanical mass containing one of the aforementioned buffers. An easy-to-handle mechanical pulp with a high absorption rate, characterized in that it contains at least 0.2% by weight of a borate-free buffer component which buffers in the pH range of 6 to 10, preferably in the pH range of 7 to 9. Mechanical pulp according to Claim 1, characterized in that it contains, as buffer, an alkali metal or ammonium salt of phosphoric acid, carboxylic acid, citric acid or tartaric acid or mixtures thereof.