AU683074B2 - Papermaking process - Google Patents

Abstract

A papermaking process in which an aqueous suspension of comminuted cellulose material is treated mechanically and the subjected to a sheet-forming operation in characterized in that the suspension contains a tertiary amine oxide. The comminuted cellulose material can come in part from wastepaper.

Description

.WO 95/07386 PCT/AT94/00098

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PROCESS FOR THE PREPARATION OF PAPER

The current invention concerns a process for the preparation of paper in which an aqueous suspension of comminuted cellulose material is mechanically treated and is subjected to a sheet-making process.

It is known that cellulose which is to be processed into paper must be milled before sheet-making. According to DIN 54 360 (November 1977), milling means mechanical treatment of the cellulose In a suspended state during which Its physical properties are so changed that it becomes suitable for the preparation of paper. During the milling of the slurry formed by the cellulose fibres and water, the fibres become cut, fibrillated and swollen. Fibrillation means the splitting of the fibres parallel to the fibre axis. After milling, the greater part of the fibrils remains hanging like frills on the fibres. Swelling and fibrillation are of great Importance in the preparation of strong paper.

The milling process is an energy-intensive process. Among products needing highly-milled fibrous materials, the milling of cellulose Is indeed one of the most energy-intensive processes in paper-making. Polymeric saccharides, monomeric and polymeric amines, amides and dyestuffs are recommended as milling aids (M Millchovsky, Chemische Aspekte der Mahlung von Zellstoff: Zellstoff und Papier, 38, page 17, (1989)). The degree of milling is given In degrees Schopper-Rlegler The strength of the resulting paper generally Increases as the degree of milling Increases.

Machines such as for instance, Hollander beaters, Jordan mills, refiners, disc mills and pulpers can be used for milling. The stock slurry is processed between a moving part and a fixed part of the machine during the milling process (Handbuch der Papler- und Pappenfabrlkation, (Paplerlexikon), 2nd Edition, Vol II, L-Z, 1971).

It is moreover known that the strength of a paper can be further Increased with additives. Such materials are for example natural rubbers and carboxymethyl cellulose. It Is also known from US-A 3 447 956 that paper T which has had chemical treatment, wherein it Is swollen at a temperature

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above 100 OC in a molten tertiary amine-oxide, has a higher strength.

In US-A 3 503 700 it Is said that paper which is soaked in a 25% aqueous solution of a tertiary amine-oxide, dried and heated to above 200tand then cooled and rinsed with water to wash out the tertiary amine-oxide again, has a higher strength after such treatment.

On the other hand problems which occur in the processing of w stepaper are increasingly described in the literature. A phenomenon well known to the paper-maker Is that cellulose fibres which have already been used one or more times for paper-making are no longer very suitable for renewed sheet- making. In the specialist world, the opinion is held that fibres which have already been milled once should not be milled any more (J Lumiainen, Refining of Recycled Fibre Advantages and Disadvantages, Papermakers Conference, 187, (1992)). Attempts to solve this problem have been made using special milling techniques and by the addition of auxiliary materials which are uncommon in paper. These auxiliary materials are supposed to increase the strength of the paper, among other features.

The invention has as its object the further development of the conventional process for paper-making, in order to allow the preparation of paper with a higher strength without the use of conventional auxiliary materials, whereby the milling time should be as short as possible.

The process according to the Invention for the preparation of paper commences with a process In which an aqueous suspension of comminuted cellulose material, for example half-stuff, is mechanically treated and Is then subjected to a sheet-making process, characterised in that, the mechanical treatment is carried out In the presence of a tertiary amine-oxide. The mechanical treatment is preferably carried out in a refiner.

Tertiary amine-oxides are known to be alternative solvents for cellulose. From US-PS 2 179 181 for example it Is known that tertiary amine-oxides have the property of dissolving cellulose without converting it into derivatives, and that cellulose mouldings such as fibres can be obtained from these solutions by precipitation. In US-PS 3 447 939, US-PS 3 447 956 and US-PS 3 508 941 further processes for the preparation of cellulose solutions

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are described whereby the solvents used are preferably cyclic amine-oxides. In all these processes however ceilulose is physically dissolved at elevated temperatures.

It has been shown that with the process according to the Invention, even waste paper can be added to the cellulose material, for example cellulose, and that even then the strength of the resulting paper is high. In this way therefore wmste paper can be reused in the process according to the invention. It is known that wste paper or cellulose fibres which have been recycled many times are not very suitable for renewed sheet-making. The given embodiment of the process according to the Invention is based on the finding that comminuted aste paper, which is subjected to a renewed milling process in the presence of a tertiary amine-oxide together with another cellulose material, is very suitable for use in the preparation of a high-grade paper.

A preferred embodiment of the process according to the invention consists of N-methylmorpholine-N-oxide being used as the tertiary amine-oxide.

The best concentration of tertiary amine-oxide in the aqueous phase of the suspension is between 55 and 72 wt%.

The invention further concerns the use of a tertiary amine-oxide as an auxiliary material in the mechanical treatment of comminuted material containing cellulose for the preparation of paper. The use of N-methyl- morphollne-N-oxide has proved to be especially advantageous.

The Invention is further described by the following Examples.

Examples

In order to reveal the effect of tertiary amine-oxides, cellulose from both sulphate and sulphite wood pulping processes were subjeeted to a standardised milling treatment at room temperature, in accordance with DIN 54 360 (November 1977) of the Standards Committee for Paper and Cardboard of the German Institute for Standards (registered Society). The reason for a«-h milling treatment is to set standards for assessing the strength properties of the cellulose.

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This is only possible when test sheets are prepared under given and reproducible conditions, and their strength properties are measured.

In accordance with the process described in DIN 54 360, suspensions of prehydrolysed sulphate cellulose ("Buckeye V5 high-grade pulp"), a sulphite- cellulose (beechwood digested-cellulose) and another beechwood digested- cellulose which had been mechanically premilled (sieve size 350 pm) were milled in a Jokro mill to varying SR degrees, whereby the consistency of the suspensions was standardised at 12%. These celluloses are not classical celluloses for paper-making; they were chosen so that the beneficial effects of amine-oxide could be better demonstrated. Using classical paper celluloses, still better effects would have been achieved without exception. Not only water but also an aqueous solution of NMMO (60 wt% NMMO, 40 wt% water) was used as the suspension medium in every test.

Sheet-making, using the respective cellulose suspensions which were obtained, was carried out according to DIN 54 358 T1 (February 1981). Strength testing (tear length) of the sheets obtained was carried out according to the standardised process described in DIN 53 112 (October 1981). The results are given in the toilowing Tables.

Table 1: Pre-hydrolysed sulphate-cellulose (Southern pine, Buckeye V5, Proctor Gamble)

Milling time (min) 10 20

Suspension medium water Milling degree (O SR): 8 9 Tear length 700 800 1000

Suspension medium 60% NMMO, 40% water Milling degree (O SR): 10 11 12 Tear length 900 1300 1500

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NOo 95/07386 PCT/AT94/00098

Table 2: Sulphite cellulose (Beechwood, Lenzing)

Milling time (min) 10 20

Suspension medium water Milling degree (o SR): 32 42 47 Tear length 1800 2100 2500

Suspension medium 60% NMMO, 40% water Milling degree (O SR): 37 47 54 Tear length 2100 2500 3100

Table 3: Sulphite cellulose (premilled) (BKZ premiled, Lenzing)

Milling time (min) 10 20

Suspension medium water Milling degree (O SR): 51 63 72 Tear length 1100 1700 1600

Suspension medium 60% NMMO, 40% water Milling degree (0 SR): 57 67 67 Tear length 1400 1600 1900

It can be seen from all the Tables that the tear length of a given paper increases with Increasing milling time, and that in every case the presence of NMMO gives the paper a greater tear length. This effect is especially marked with prehydrolysed sulphate-cellulose (see Table 1) where the presence of NMMO during milling of the cellulose fibres increases the tear length of the paper obtained by up to

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It can also be seen from all the Tables that the presence of NMMO leads to more efficient milling because higher degrees of milling are attained In a shorter period of time. This is naturally reflected in a saving of energy. It is astonishing that the increase in the degree of milling is not proportional to the tear length. Thus for example, the presence of NMMO during the minute milling of prehydrolysed sulphate-cellulose effects a 20% increase in the degree of milling but a 50% increase in the tear length.

It can also be seen that the premilled sulphite-cellulose (Table which on account of its poor fibre-forming properties after 30 minutes milling gives a paper with a tear length of only 1600 m, gives with the addition of NMMO a higher quality paper with a tear length of 1900 m; this latter paper is comparable with a paper prepared from a higher grade sulphite-cellulose (Table 2) using a suspension mi'led for 10 minutes without the addition of NMMO. This means that a material which can be processed by conventional means to give only a low grade paper, can be processed to give a high quality paper by milling In the presence of NMMO.

The process according to the Invention is suitable for all types of cellulose and is Independent of the chosen digestion process.

With the process according to the invention moreover, even waste paper consisting of fibres which have already been subjected several times to a conventional milling process and to sheet-making, can be processed together with cellulose to give high quality paper without additional auxiliary materials having to be added.

Claims (7)

*p I 7 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. Process for the preparation of paper in which an aqueous suspension of comminuted cellulose material is mechanically treated and is then subjected to a sheet-making process, characterised in that, the mechanical treatment is carried out in the presence of a tertiary amine- oxide.

2. Process in accordance with Claim 1, characterised in that, as the comminuted cellulose material a material is used which has already been subjected once to a sheet-making process.

3. Process in accordance with Claim 2, characterised in that, the cellulose material used comes partly from waste paper.

4. Process in accordance with one or more of the Claims 1 to 3, characterised in that, N-methylmorpholine-N-oxide is used as the tertiary amine-oxide.

Process in accordance with one or more of the Claims 1 to 4, characterised in that, the aqueous phase of the suspension contains .0 from 55 to 72 wt% of the tertiary amine-oxide.

6. Process in accordance with one or mnore of the Claims 1 to 20 5, characterised in that, the mechanical treatment is carried out in a i refiner. 7. Process as hereinbefore described with reference to the examples. 00o

25 DATED this Twenty-eighty day of July 1997.

LENZING AKTIENGESELLSCHAFT 0 By its Patent Attorneys FISHER ADAMS KELLY

INTERNATIONAL SEARCH REPORT ner-lApiaonN

PC1/AT 94/00098 A. CLASSIFICATION OF SUB3JECT MATTER IPC 6 021C9/00

According to trational Patent Claslilc.jon or to both national classification and (PC B3.FIELDS SEARCHED Minimum documentation searched (classification system followed by canmication symnbols) IPC 6 D21C

Documentation searched other than minimum documentation to the extent that such documents are included in thc fields searched

Electronic data base consulted during the intemationill search (name of data base and, where practical, search terms used)

C. DOCUMENTS CONSIDERED TO BE Category Citation ofdocument, with indication, where appropriate, of the relevant passages Relevant to claim No.

A DE,A,32 37 574 (HOECHST AG) 12 April 1984I 1,7 see the whole document A CHEMICAL ABSTRACTS, Vol. 101, no. 16, 4,8 October 1984, Columbus, Ohio, US; abstract no. 132754, KOGAN, E. G. ET AL 'Phase state and rheological properties of cellulose solutions in methylmorpholine oxide' see abstract KHIM. VOLOKNA (1984), 30-2 CODEN: KVLKA4; ISSN:- 0023-1118

Further documents are listed in the continuation of box C, I Patent family members ane listed in annex

Special categories ofkited doetmints Tr later document published aft the international fIling date oftheartwhih ~or defiingthegenralstat priority date and not in conflict with the Application but documeant iiigtegnrlsaeotharwicisotcited to understand the principle or theory underlying the cmnsiere to be of particular relevance Iieto W8earlier docurmt but published on or after the international W document of particular relevance; the claimed invention filing date cannot be conidered novel or cannot be considered to WLdocument whieh may throw doubts on priority clAln~s) or involve An inventive step when the documient is taken $lone which is cited to establish the publication date of another documnent of particular relevance; the claimed invention citation or other special reason (as specified) cannot be considered to Involve An inventive step when the O0 document refering to an oral disclosure, use, exhibition or document iscombincd with one or mom other such docu. other means ments, such combianation beilig obvious to a person skilled document puiblished prior to the international filing date but inthe art. later than the priority date claimecC W document member of the same patent family Date of the actual completion of the international search Date of mailing of the Interlational search report

7 October 1994 21. V0. 94 Name and mailing address of the ISA Authorized omeer Europa Paten P.D. 5111 Patentliun 2 *fie NL -21 =l &Rijswijk Te. (31!70) 3%=.04Tx. 316S1eponW, Sny Fast (4 31.70) 340-3016 Sny (July 1992) sheet) Paom CT1ISAMI (5.oio

INTERNATIONAL SEARCH REPORT InetWplcdnl iormation, on patent fam'ily menbr PCfAT 94/00098 Patent document Publication Patent family Publication cited in search report date Imember(s) date

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YomnloCT/ISA/210 (patent (uniy aax) (July IM

I NTERNATIO ALER REC ERF1.JfllIrr Intern alcs Ak~cnzcichcn

PCTIAT 94/00098 A. KLASSIFIZIERUNC3 DES ANMELDUNGSGEGENSTANDES IPK 6 D21C9/00

Nach der Internationalen Patentkiassiflkation (IPK) oder nach der natianaleri Kitisiikation und der IPK 8. RECHERCH1I!RTE GEBIETE Recherchierter Minitcstpr(Iistoff (Kluiflkabormytem Und Klmflikatonssymbole IPK 6 D21C

Rtcherchierte aber nlcht zumn Mindcstprilfstoff gchbrcnde Ver~ffntlichungen, soweit diese unter die recherchicrtcn Gebicte fallen

Wihrend der internAtionalcn Recherche konsultierte clcktronischc Datenbank (Name der Datenbank und cvii, verwendete Suchbegriffi)

C. ALS WI3SENTLICII ANGESEHENI3 ONTERLAGEN Katcgoric' D~emcduung der Verfcntltclnmg, sowcst crforderllch tinter Angabe dier in lictracht koromenden Tefle I A, ,uch Nr,

A DEA,32 37 574 (HOECHST AG) 12. April 19B1 siehe das ganze Dokument A CHEMICAL ABSTRACTS, Vol. 101, no. 16, 4,8 Oktober 1984, Columbus, Ohio, US; abstract no, 132754, KOGAN, E. G. ET AL 'Phase state and rheological properties of cellulose solutions in methylmorpholine oxide$ siehe Zusammenfassung KHIM. VOLOKNA (1984), 30-2 CODEN: KVLKA4; ISSN: 0023-1118

fJ Welterc Ver&Fcntlichungen d der Portsetzung von Feld Czu Mv Sicha Anhans PAtentfamflic Desondere K~tetorien von angegebenen Vcrdftentichungen r SpAtere VerdfFentlichung, die nach dein internationalen AnlckdAturn Vcrdfevtllchung, die den aligemcinen Stand der Techik defsl~, 6der dem Priorliftdatum varoftntlicht wordcn tit tind init dier Wsbsien Wiusr nuet i AnntchGi. nlcht kollidlcrt. sondern nur zuiVeritindnis dei der lirfindung zugrndeliegenden Prinalpi cider der it zugrunddllcgenilen W3 Altercs Dokuinent das Jedoch cnt am oder nach dem inernutitelma Thm.oe angegeben lit Anineldcdatun verdffentlicht,wonden ist W Verdffntflchung von besoderer lledtutunr. die beanspneehte Wrtduns OL. Vcr~ffent~limi die geeignet it. elnen Priorlthtsanspreh zwcifelhgft er. kann allein aulaend dieser Vrer~nlihung nicht als neu oder Wu heincen eta Is,%en, odtr durch die das Ver~ffntlichwngidatum Ciner erfinderischer Tltigktit beruhend bxtrachtet werden atiderersi rA Me-. hcnbcricht gchmnten Verdi~entlichung bce. werden Vcrdffcntlichung von besonderer Bedeutung die bearapeuchts llnindung W14eder die tu einein anderen besonderen Grind angegcbcn ist (wie kamenicht als AUterfindarlcher TtAgkeit berubend beiraebtct Verdffentlichung, die etch auf elne mOndliche Offenbarung, Verden rolcun dieve Verbfctlhn aoeI i in oden rahecren and elnc Benutzug, eine Atnstelluag oder Wnere Ma~nahmen bedit tVeri~ndcungnfd ie Kachman rVebiend u~txah idtn TO Verdffentlichung, die vor n internationalen Anmeldedatum aber nach e~~nlcug ~Mtleddrebe aetall aise deei beanspuchnn irtedatum vcndffcntlicht worden litA'Vrfetihgot igedeveb Ptd Datumn des Abmechums 8er inwrnationalen Recherche Ataaceditwm des internationalen Retcerehenbeuichts

7. Oktober 1954 244.4L Name und Postanschrift der Internationale Recherchentxhirde IlevdlInichdgter 0ediensteter Euopizches Patenta,4 P.D3. 5815 Patentlain 2 NL 2250 flY lRjwilk Tel. 31.70) 340-2040, Thx 31 651 eipo nW, Sny S ny Fix (+311470) 340-3016

rawiblatt PCO/ISM11 (Blatt 2) (lull 1992)

INTERNATIONALER RECHERCFTENBERICHT Intn'rraWes Aktomccbc Angaben zu Ver8ffenUichu. ,die zur selben Pateatbmi: go6ren IPCT/AT 94/00098 Im Rechercheneih Datum der M~itg[ied(er) der I Datum der angef'(hrtes Patetdkm t Verdffentlichung Pateiitfaniilie Verdffenitichung

DE-A-3237574 12-04-84 KEINE

Feablat PC?/IIIO (Mbutng h~ftWU6hlXUU I12)