NO136583B

NO136583B -

Info

Publication number: NO136583B
Application number: NO743286A
Authority: NO
Inventors: N Soteland
Original assignee: Papirind Forskningsinst
Priority date: 1974-09-12
Filing date: 1974-09-12
Publication date: 1977-06-20
Also published as: NO136583C; BE833343A; FI59444C; FR2284706A1; DE2539570B2; IT1049168B; DE2539570C3; AT347781B; CA1073162A; GB1515865A; FI59444B; JPS5184904A; DK406775A; FR2284706B1; AU8455175A; NO743286L; NL7510763A; ATA688175A; FI752552A; DE2539570A1

Description

Foreliggende oppfinnelse vedrorer mekanisk tremasse med hoy vannabsorpsjonshastighet, samt fremgangsmåte for fremstilling av en slik masse. The present invention relates to mechanical wood pulp with a high water absorption rate, as well as a method for producing such a pulp.

Mekaniske masser er en fellesbetegnelse for massetyper erholdt ved mekanisk defibrering av forskjellige treslag, eksempelvis ved hjelp av slipestener eller skiveraffinorer, eventuelt etter en mild kjemikaliebehandling. Mechanical pulp is a general term for types of pulp obtained by mechanical defibration of different types of wood, for example with the help of grinding stones or disc refiners, possibly after a mild chemical treatment.

Da mekanisk masse er et relativt rimelig produkt, sammenlignet med cellulosemasser erholdt ved en kjemisk oppslutning av ved, har slike masser fått en bred anvendelse som råstoff ved fremstilling av avispapir, magasinpapir o.l.. Imidlertid da slipe-massen utviser den uheldige egenskap at den undergår "selvliming" ved lagring, har det tidligere vært nodvendig å lagre As mechanical pulp is a relatively inexpensive product, compared to cellulose pulps obtained by chemical digestion of wood, such pulps have been widely used as a raw material in the production of newsprint, magazine paper etc. However, as the grinding pulp exhibits the unfortunate property that it undergoes " self-gluing" when storing, it has previously been necessary to store

og transportere mekanisk masse i fuktig tilstand, eller torke denne på en spesiell måte, eksempelvis ved den såkalte "flash-torke-metoden". Som folge av "selvlimingen" vil mekanisk masse etter lagring utvise mer eller mindre hydrofobe egenskaper, avhengig av lagringstid, harpiksinnhold, lagringsforhold etc, hvilket gjor en videre håndtering av en slik masse vanskelig når denne skal videreforedles. and transport mechanical pulp in a moist state, or dry it in a special way, for example by the so-called "flash-drying method". As a result of the "self-gluing", mechanical pulp will exhibit more or less hydrophobic properties after storage, depending on storage time, resin content, storage conditions etc., which makes further handling of such pulp difficult when it is to be further refined.

På grunn av "selvliming" har mekanisk masse kun i beskjeden grad blitt anvendt for absorpsjonsformål, eksempelvis i bleier, damebind, tamponger, håndklær og lignende produkter, med hvilke formål hoyforedlede, blekede celluloser stort sett har vært enerådende. Because of "self-gluing", mechanical pulp has only been used to a modest extent for absorption purposes, for example in nappies, sanitary napkins, tampons, towels and similar products, for which purposes highly refined, bleached celluloses have largely prevailed.

•Hvis harpiksen kan fjernes fra den mekaniske masse, har det vist seg at mekanisk masse med fordel også kan anvendes for de ovenfor nevnte formål, slik som angitt i norsk patent :nr. 124.193. Ifolge dette patent kan iharpiksen fjernes fra massen eksempelvis ved ekstraksjon med aceton, hvorved det erholdes ét •If the resin can be removed from the mechanical pulp, it has been shown that mechanical pulp can also be used with advantage for the above-mentioned purposes, as stated in Norwegian patent : no. 124.193. According to this patent, the resin can be removed from the mass, for example by extraction with acetone, whereby one is obtained

produkt med gode absorpsjonsegenskaper. Imidlertid er en indu-striell ekstraksjonsprosess en relativt komplisert og fordy-rende prosess, som krever stor kapitalinvestering i ekstrak-sjonsutstyr, gjenvinningsutstyr etc Aceton-ekstraher ing av mekanisk masse har også tidligere vært foreslått for å forbedre den mekaniske masses styrkeegenskaper og for å gjore massen lettere oppslagbar i den etterfolgende foredlingsprosess (Brandal & Lindheim, Pulp & Paper Mag. Can. 67 T 431, 1966). product with good absorption properties. However, an industrial extraction process is a relatively complicated and expensive process, which requires a large capital investment in extraction equipment, recycling equipment, etc. Acetone extraction of mechanical pulp has also previously been proposed to improve the mechanical pulp's strength properties and to make the pulp is more easily digestible in the subsequent refining process (Brandal & Lindheim, Pulp & Paper Mag. Can. 67 T 431, 1966).

Det har nå overraskende vist seg at det er mulig å behandle It has now surprisingly been shown that it is possible to treat

en mekanisk masse slik at den ved aldring bibeholder sine opp-rinnelige hydrofile egenskaper,slik at en mekanisk masse behandlet i henhold til foreliggende oppfinnelse, ved lagring vil forbli hydrofil og således lett å slå opp ved den etterfolgende foredling. Det har ytterligere vist seg at en slik masse er utmerket egnet for absorpsjonsformål, dette til tross for at den nye behandlingsmåte i liten grad påvirker den mekaniske masses harpiksinnhold. a mechanical mass so that it retains its original hydrophilic properties during aging, so that a mechanical mass treated according to the present invention will remain hydrophilic when stored and thus easy to break up during the subsequent processing. It has further been shown that such a pulp is excellently suitable for absorption purposes, this despite the fact that the new treatment method has little effect on the resin content of the mechanical pulp.

Den nye fremgangsmåte omfatter en behandling eller impregne-ring, av den mekaniske masse med en puffer, som pufrer i pH-området 6-10, fortrinnsvis 7-9. Egnede puffere er alkalimetall-salter og ammoniumsalter av eksempelvis fosforsyre, karbonsyre, sitronsyre, vinsyre etc. Pufferen tilsettes den mekaniske masse, fortrinnsvis i form av en vandig opplosning og i en slik mengde at den mekaniske masse tilfores minst 0,2 vekts%, regnet på The new method comprises a treatment or impregnation of the mechanical pulp with a buffer, which buffers in the pH range 6-10, preferably 7-9. Suitable buffers are alkali metal salts and ammonium salts of, for example, phosphoric acid, carbonic acid, citric acid, tartaric acid, etc. The buffer is added to the mechanical mass, preferably in the form of an aqueous solution and in such a quantity that the mechanical mass is supplied with at least 0.2% by weight, calculated on

massens torrvekt, fortrinns/is 0,5 % eller mere. dry weight of the mass, preferably 0.5% or more.

En slik behandling av den mekaniske masse med en vandig opplosning av pufferen er meget billig og enkel å utfore. Tilsetningen kan skje på flere steder under fremstilling av den mekaniske masse, avhengig av produktets bruksområde og tilgjengelig utstyr. Tilsetningen kan eksempelvis skje under massefremstil-ling i raffinor eller slipestol, i papirmaskinens bakvanns-system, i limpressen, ved påsproytning under eller etter ark-dannelsen, innsproytning i massen, for denne eventuelt omdannes til masseballer. Den nye behandlingsmåte kan således utfores med tilgjengelig utstyr og kan således tillempes i allerede eksisterende produksjonsanlegg. Ved den nye fremgangsmåte vil man eksempelvis kanne fremstille absorberende materialer fra mekaniske masser, hvilket betyr vesentlige besparelser vis a vis hoyforedlede celluloseprodukter. Sett fra et ressurs- og miljomessig hensyn representerer fremgangsmåten store selvinn-lysende fordeler. Such treatment of the mechanical pulp with an aqueous solution of the puffer is very cheap and easy to carry out. The addition can take place in several places during the production of the mechanical pulp, depending on the product's area of use and available equipment. The addition can, for example, take place during pulp production in a refiner or grinding wheel, in the paper machine's waste water system, in the glue press, by spraying during or after sheet formation, injection into the pulp, for this to eventually be converted into pulp bales. The new treatment method can thus be carried out with available equipment and can thus be applied in already existing production facilities. With the new method, for example, it will be possible to produce absorbent materials from mechanical masses, which means significant savings vis-à-vis highly refined cellulose products. Seen from a resource and environmental perspective, the method represents major self-evident advantages.

Oppfinnelsen skal i det etterfolgende belyses med de folgende eksempler, som viser effekten av den nye behandlingsmåte. In what follows, the invention will be illustrated with the following examples, which show the effect of the new method of treatment.

Forskjellige masse-typer ble behandlet med pufferen både ved påsproytning og neddypping i pufferopplosningen. Massenes torrstoffinnhold for behandling eller påsproytning med pufferopplosningen varierte mellom 25% og 90% torrstoff. Etter behandling ble massen torket i en cyklon og fluffet (i en Wenneberg-kvern). En del av den således pufferbehandlede og fluffede masse ble kunstig eldet ved 105°C i 1 time, hvor-etter massen fikk henstå i 30 - 60 minutter ved romtemperatur for den eldede massens vannabsorpsjon ble bestemt. Vannabsorp-sjonen for ikke-eldet masse og ikke-behandlet masse ble også bestemt. Different pulp types were treated with the puffer both by spraying on and by dipping in the puffer solution. The dry matter content of the pulps for treatment or spraying with the buffer solution varied between 25% and 90% dry matter. After treatment, the pulp was dried in a cyclone and fluffed (in a Wenneberg mill). Part of the thus puffed and fluffed mass was artificially aged at 105°C for 1 hour, after which the mass was allowed to stand for 30 - 60 minutes at room temperature for the water absorption of the aged mass to be determined. The water absorption of unaged pulp and untreated pulp was also determined.

Bestemmelse av vannabsorpsjons-hastigheten ble ved disse forsbk utfort ved at 10 g lufttorr, fluffet masse fordeles jevnt i et metallnett (metallkurv med dimensjonene 7 cm x 20 cm x 1 cm) som ble plassert i en beholder inneholdende 200 ml vann. Den tid det tar fra det oyeblikk metallnettet plasseres i beholde-ren og til all masse er gj ennomfuktet med vann er et mål for massens vannabsorpsjonshastighet. Determination of the water absorption rate was carried out in these experiments by distributing 10 g of air-dry, fluffed mass evenly in a metal net (metal basket with dimensions 7 cm x 20 cm x 1 cm) which was placed in a container containing 200 ml of water. The time it takes from the moment the metal mesh is placed in the container and until all the pulp is thoroughly moistened with water is a measure of the pulp's water absorption rate.

De erholdte resultater er gjengitt i den etterfolgende tabell. Som det fremgår av de ovenfor angitte resultater så oppnås ved behandlingen ifolge foreliggende oppfinnelse en betydelig for-bedret vannabsorpsjonshastighet i forhold til ikke-behandlet masse. Et unntak er imidlertid boratpufferen, som tilsynela-tende for ikke-eldet masse har en nedsettende virkning på absorpsjonshastigheten, men etter elding utviser eldet, borat-puf f er-behandlet masse en storre absorpsjonshastighet enn ikke-behandlet masse. The results obtained are reproduced in the following table. As can be seen from the above results, the treatment according to the present invention achieves a significantly improved water absorption rate compared to untreated pulp. An exception, however, is the borate buffer, which apparently for unaged pulp has a lowering effect on the absorption rate, but after aging, the aged, borate-buffer-treated pulp exhibits a greater absorption rate than untreated pulp.

Det vil ytterligere fremgå at masser behandlet med de andre puffere med hensyn til vann-absorpsjonshastigheten nesten ikke påvirkes ved kunstig elding, idet en forskjell på 1 sek. trolig ligger vel innenfor feilgrensen for denne spesielle prove-metodikk. It will further appear that pulps treated with the other buffers with regard to the water absorption rate are almost not affected by artificial ageing, as a difference of 1 sec. is probably well within the margin of error for this particular test methodology.

For sammenlignings skyld kan nevnes at en hoyforedlet cellu-lose under de tilsvarende betingelser utviser en vann-absorpsjonshastighet i størrelsesorden 5 sek.. For the sake of comparison, it can be mentioned that a highly refined cellulose under the corresponding conditions exhibits a water absorption rate of the order of 5 seconds.

De mekaniske masser i henhold til foreliggende oppfinnelse The mechanical masses according to the present invention

er således med hensyn til vann-absorpsjonshastighet sammen-lignbaremed hoyforedlede cellulosemasser, ytterligere da de bevarer sine hydrofile egenskaper ved elding,» lar de seg lett slå opp ved en eventuell videreforedling, eksempelvis i en papirfabrikk som anvender mekanisk masse som råprodukt. are therefore comparable in terms of water absorption rate to highly refined cellulose pulps, further as they preserve their hydrophilic properties during ageing," they allow themselves to be easily broken up during any further processing, for example in a paper mill that uses mechanical pulp as a raw product.

Claims

1. Mechanical wood pulp that can easily be broken down in water with a high absorption rate, characterized in that it contains at least 0.2% by weight, preferably at least 0.5% by weight, calculated on the dry mass, of a buffer component that buffers in the range of pH 6 - 10, preferably in the range pH 7 - 9.

2. Mechanical mass according to claim 1, characterized in that it contains an alkali metal or ammonium salt of phosphoric acid, carbonic acid, citric acid or tartaric acid, or mixtures thereof.

3. Method for producing the mechanical mass according to claims 1 or 2, characterized in that a non-borate-containing buffer substance is added to the mass that buffers in the pH range 6:- 10, preferably in the pH range 7-9.

4. Method according to claim 3, characterized in that a buffer substance is added to the mass which is an alkali metal or ammonium salt of phosphoric acid, carbonic acid, citric acid or tartaric acid, or mixtures thereof.