CA1170487A - Process for improving and retaining pulp properties - Google Patents
Process for improving and retaining pulp propertiesInfo
- Publication number
- CA1170487A CA1170487A CA000402701A CA402701A CA1170487A CA 1170487 A CA1170487 A CA 1170487A CA 000402701 A CA000402701 A CA 000402701A CA 402701 A CA402701 A CA 402701A CA 1170487 A CA1170487 A CA 1170487A
- Authority
- CA
- Canada
- Prior art keywords
- pulp
- fibres
- pulps
- heat treatment
- pulp fibres
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/001—Modification of pulp properties
- D21C9/007—Modification of pulp properties by mechanical or physical means
Abstract
ABSTRACT OF THE DISCLOSURE
A process is provided for treating pulp fibres, that have already been curled in order to improve at least some of the following physical properties: drainage, wet-web stretch, wet-web work-to-rupture, and dry-sheet tear strength and stretch, which process comprises: subjectinng said curled pulp fibres to a heat treatment while said pulp is at a high consistency in the form of nodules or entangled mass, without appreciable drying of the pulp, the heat treatment being at an elevated temperature and for a time sufficient to render the curl permanent to subsequent mechanical action. The process comprises: subjecting the curled pulp to a heat treatment e.g. at a temperature of at least 100°C, preferably 100°C-170°C, for a sufficient length of time, e.g. between 60 minutes and 2 minute, inversely dependent on the temperature, while the curled pulp is at a high consistency, e.g. at least 15% pre-ferable 15% to 35%, in the form of nodules or entangled mass. The heat treatment is sufficient to render the curl permanent to sub-sequent mechanical action. This permanent curl has advantages for papermachine runnability and for increasing the toughness of the finished product.
A process is provided for treating pulp fibres, that have already been curled in order to improve at least some of the following physical properties: drainage, wet-web stretch, wet-web work-to-rupture, and dry-sheet tear strength and stretch, which process comprises: subjectinng said curled pulp fibres to a heat treatment while said pulp is at a high consistency in the form of nodules or entangled mass, without appreciable drying of the pulp, the heat treatment being at an elevated temperature and for a time sufficient to render the curl permanent to subsequent mechanical action. The process comprises: subjecting the curled pulp to a heat treatment e.g. at a temperature of at least 100°C, preferably 100°C-170°C, for a sufficient length of time, e.g. between 60 minutes and 2 minute, inversely dependent on the temperature, while the curled pulp is at a high consistency, e.g. at least 15% pre-ferable 15% to 35%, in the form of nodules or entangled mass. The heat treatment is sufficient to render the curl permanent to sub-sequent mechanical action. This permanent curl has advantages for papermachine runnability and for increasing the toughness of the finished product.
Description
~7~4~17 This invention relates to a process or treating lignocellulosic pulp fibres of ei~her softwoods or hardwoods to provide pulps of improved properties. In particular this invention is directed to the treatment of mechanical pulps and high-yield chemical pulps to improve and retain the properties oE such pulp5.
Newsprint traditionally has been manufactured from a furnish consisting of a mixture of a mechanical pulp and a chemical pulp. Mechanical pulp is used because it imparts certain desired properties to the furnish:
namely, its high light scattering coefficient contri-butes to paper opacity and allows the use of a thinner sheet; its high oil absorbency improves inX acceptance during printing.
Chemical pulps are used because they impart propertie~ to the furnish which improve its run-nability. Runnability refers to properties which allow the wet-web to--be transported at high speed through the forming, pressing and drying sections of a paper-machine and allows the dried paper sheet to be reeled and printed in an acceptable manner. Runnability con-tributes to papermachine and pressroom efficiency.
It is believed that improved runnability in chemi-cal pulp is due to high wet-web strength and drainage rate. Wet and dry stretch are important because they are believed to contribute to preventing concentrations of stress around paper defects, thereby minimizing .
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breaks. High drainage rates lower the water content and are believPd to yield a less fragile web.
Mechanical pulps including stone grounc1wood (SG) and pressurized stone groundwood (PSG) can be made to provide wet stretch but only at the expense of poor drainage. Higher quality mec'nanical pulps are obtained by manufacture in open discharge refiners, to produce refiner mechanical pulp (RMP) and in pressurized thermomechanical pulp (TMP). Still further upgraded mechanical pulps were provided by chemical pretreatment of the wood chips prior to refining to provide chemi-mechanical pulp (CMP or CTMP).
U.S. Patent 3,446,699 issued May 27, 1965 to Asplund et al. provided a method for producing mechani-cal and chemimechanical or semichemical pulps from lignocellulose-containing material, in order to provide what was alleged to be improved quality of the ibres with improved defibration.
U.S. Patent 3,55~,428 issued Jan. 26, 1971 to Asplund et al. provided a method for manufacturing chemimechanical pulps involving heating and defibrating the same in an atmosphere of vapour at elevated temper-atures and under corresponding pressure of the impreg-nated chips to provide a more rapid and effective impregnation.
U.S. Patent 4,116,758 issued Sept. 26, 1978 to M.J. Ford provided a process for producing high-yield chemimechanical pulps from woody lignocellulose materi-al by treatment with an aqueous solution of a mixture of sulfite and bisulfite, to provide a pulp which can 'qk~V7 be readily defibered by customary mechanical means to provide a pulp having excellent strength characteris~
tics.
Today's papermaker is ~aced with the problems of decreasing forest resources, an increasing demand for paper products and stringent environmental laws. Low-yield chemical pulps, e.g. sulphite and kraft pulps, contribute highly to such problems~
The fibres of low-yield chemical pulps are known for their desirable dry- and wet-web strength proper-ties. Observations of low-yield chemical fibres in a formed paper sheet indicate that these tend to have a kink and curl which is said to contribute, in an advan-tageous way, to the papermachine runnability and to certain physical properties. Mechanical pulps lack the desirable strength properties to replace, in whole or in part, low-yield chemical pulps, e.g. kraft or sul-phite pulps, in linerboard, newsprint, tissue, printing grades and coated-base grade of paper. Consequently, it has been an aim of the art to improve the physical properties of mechanical and high-yield chemical pulps, so that such improved pulps would be used to replace low-yield chemical pulps.
A number of mechanical devices have been built to produce curled chemical and mechanical fibres in order to improve certain physical properties. Two such mechanical fibre-curling devices are disclosed in H.S.
Hill, U.S. Pat. 2,516,384 and E.F. Erikson U.S. Pat.
3,054,532.
H.S. Hill et al. in Tappi, Vol. 33, No. 1, pp.
76~4~7 36-44, 1950, described a "Curlator" designed to produce curled fibres. The process consisted of rolling fibres into bundles at a consistency of around 15%-35%, followed by dispersion. Advantages claimed were higher wet-web stretch, improved drainage, and higher tear strength and stretch of the finished product. These advantages were at -the expense of certain other proper-ties, notably tensile strength.
W.B. West in Tappi, Vol. 47, No. 6, pp. 313-317, 1964, describes high consistency disc refining to pro-duce the same action.
D.H. Page in Pulp Paper Mag. Canada, Vol. 67, No.
1, pp. T2-12, 1966, showed that the curl introduced was both at a gross level and at a fine level which he called "microcompressions". Both types of curl w~re advantageous.
J.H. De Grâce and D.H. Page in Tappi, Vol. 59, No.
7, pp. 98-101, 1976, showed that curl could be produced adventitiously during bleaching of pulps, by the mechanical action of pumps and stirrers at high con-sistency.
R.P. ICibblewhite and D. Brookes in Appita, Vol.
28, No. 4, pp. 227-231, 1975, claimed that this adven-titious curl could have advantages for practical run-nability of papermachines.
High-consistency mechanical defibration of wood chips is known to produce curled, kinked and twisted fibres. Kinked fibres are known to be particularly effective in developing extensibility in wet webs if the kinks are set in position so that they survive the 7e~7 action of pumps and agitators at low consistency and retain their kinked and curled state in the formed sheet. This ensures enhancement of the wet-web stretch and certain other physical properties.
A number of chemical treatment methods have been reported to enhance and retain fibre curl in a refined pulp. In one, Canadian Patent No. 1,102,969 issued June 16, 1981 to A.J. Kerr et al., improvement in tear-ing strength of the pulp is alleged by the treatment of delignified lignocellulosic or cellulose pulp derived from a chemical, semichemical or chemimechanical pulp-ing process at a pressure of at least one atmosphere, with sufficient gaseous ammonia to be taken up by moist pulp in an amount greater than 3% by weight to weight of oven dried pulp.
In another, Canadian Patent ~o. 1,071,805 issued Feb. 19, 1980 to A.J. Barnet et al., a method of treat-ment of mechanical wood pulp is provided by cooking the pulp with aqueous sodium sulphite solution containing sufficient alkali to maintain a pH greater than about 3 during the cooking. The cooklng was effected at an elevated temperature for a time sufficient to cause reaction with the pulp and to increase the drainage and wet stretch thereof, but for a time insufficient to cause substantlal dissolution of liquor from the pulp, and insufficient to result in a pulp yield below about 90~. A minimum concentration of sodium sulphite was 1%
since, below 1% sodium sulphite improvements were said to be too small to justify the expense of treatment.
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-: During the process of papermaXing, most of the curl in both high-consistency refined mechanical and hi~h-yield sulphi~e pulp is lost in the subsequent steps of hanaling at low consistency and high tempera-tures. This is also taught in the article by H.W.H.
Jones in Pulp Paper Mag. Canada, Vol. 67, No 6, pp.
T2~3-291, 1966. Jones showed that when mechanical pulp fibres which are curled during high consistency refin-ing are subjected to mild mechanical action in dilute suspension at a temperature of arouna 70C the curl tends to be removed. The increased tensile and burst strengths produced by removal of curl was seen as advantageous. Thus, curl in such pulps is normally removed in ~apermachine operation, since auring practi-cal papermaking, pulps are always subjected to mild mechanical action ln dilute suspension at temperatures of the order of 70C.
High-yleld and ultra high-yield sulphite pulps are used as reinforcing pulps for manufacture of newsprint and othe~ groundwood-containing papers. Although they ~ay be subjected to high-consistency refining, their fibres are in practice substantially straight because the curl introduced in high-consistency refining is lost in subsequent handling.
Accordingly an object of one aspect of this inven-tion is to provide a process for imparting and render-ing permanent, the physical properties of such mechani-cal and high-yield chemical pulps in order to improve their papermachine runnability and pressroom effici-' ~ ~ ency. 117~7 An object of another aspect of this invention is to providea non-chemical process of treating higher-yield pulps ta improve and retain certain physical properties so that the pulp can be used to replace in whole or in part, the low-yield chemical pulps.
It is an object of yet another aspect of the present inven-tion to render permanent, by non-chemical means, the curl imparted ,,, ~, ., . ,, .. .. .. ._ . , . --to the fibres of high-consistency mechanically treated, mechanical and high-yield chemical pulps.
The mechanicaI pulps or high-yield chemical pulps included within the ambit of various aspect~s of this inventlon can be produced by either mechanical deflbration of wood, e.g. in stone groundwood (SG), pressurized stone groundwood (PSG), refiner mechanical pulp (RMP) and thermomechanical pulp (TMPj production or by mechanical defibration, at high~consistency, followed or preceded by a chemical :. , : . .
treatment of wood chips~and pulps e.g.~in the production of ultra-high-yield sulphite pulps (UHYS, yie;lds~ in the range 100-85%), high-: : : : :
yield sulphlte~pulp~s (HYS, yields ln the range 85-65%),~chemi-thermo-mechanical (C1`MP), high-yield chemimechanical (CMP), lnterstage~ ~
thermomechanical and chemically~post-treated mechanical pulp (MPC) - or~thermomechanical~pulps (TMPC) By~ a broad aspect of this invention`, a process is provided for treating pulps, that havè already;been curled, in order to im-~prove at least some~of the following physical properties: drainage, :
wet-ueb stretch, wet-web work-to-rupture, and dry-sheet tear strength and stretch,~which process comprises: sobjecting the curled pulp .
fibres to a heat treatment while said pulp is at a high consistency ~ ;
in the form of nodules or entangled mass, without appreciable drying of the pulp, the heat treatment being at an elevated temperature and for a time sufficient to render the curl permanent to subsequent ~mechanical action, which process comprises: subjecting the curled pulp to a heat treatment, e.g., at a treatmcnt of at least 100 C, ~:~7~
preferably 100C-170C, for a sufficient length of time, e.g., between 60 minutes and 2 minutes, inversely dependent on the temperature while curled pulp is at a high consistency, e.g., at least 15%, preferably 15% to 35%, in the form of nodules or entangled masses, thereby to render the curl per-manent to subsequent mechanical action.
The present invention in its broad aspects is a process which fol-lows the mechanical action that the already made the fibres curly in either mechanical, ultra high-yield or high-yield pulps. Such a mechanical action generally takes place at high consistency (15%-35%), and may typically be a high-consistency disc refining action, e.g. as is generally used io pulp manufacture. ~ ;
The process of aspects of this invention thus consists of a simple heat treatment of the pulp in the presence of water while it is retained in the form of nodules or entangled mass at a high consistency. The process preferably involves temperatures ahove;100 C, ln which case a pressure vessel is required.
Wh~le the inven~tion is not to be limited to any theory, it is believed that the process sets~the curl in place e~ther by relief of stresses in the Eibre or by a cross-linking~mechanism, so that~upon subsequent pro-cessing during papermaking, the~fibres retain their curled form. ,~
This curled form has particular advantàges for the propertibs~of~
, the wet web, so that the runnability of the papermachine is improved. In addition, the toughness of the finished produce is increased.
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ln gcncral tcr~s~ thc pr3C~ss b~ins ~it}, a p~llp tl~a~ has becn converted to the curly state by mechanical action at hi~h consistency, and in whichthe fibres are held in a curly s~ate in the or~, of nodules or en-tangled mass. The pulp may be either purely mechanical, e.g, stone ground-wood, pressurized stone groundwood, refiner mechanical, thcrnlomechanlcal, or a chemimechanical pulp, e.g., ultra high-yield sulphite pulp or high-yield sulphite pulp. Conversion to a curly state is generally achie~ed naturally in the high-consistency refining actionthat is normally used for refiner mechanical, theremomechanical and ultra high-yield sulphite pulp. For stone groundwood, pressurized stone groundwood and high-yield sulphite pulp, it would be necessary to add, to the normal processing, a step that curls the .- fibres. This may be for example by use of a machine~known by the Trade Mark of CURLATOR or high-consistency disc refining, or by use of a machlne known by the Trade Mark FROTAPULPER (See E.F. Erikson, U.S. Pat. 3,054,532).
`~ The pulp fibres may be lignocellulos~c fibres produced by mechanlcal , defibratlon, or by refining, or by refin~ng in a disc ref~ner at high consis-tency, or by mechanical deflbratlon at high consistency of wood chips, or by mechanical defibration at hlgh consistency of wood chips followed or preceded by a chem~cal t~reatment, or by a slngle stage~refining~, or after two successive~refinings, or between two~successive refinings. They may~ ;
alternatively be pulp fibres commercially~produced under the designation o~f refIner mechanical pulp, pressurized~reflner meGhanicalpulp ànd thermo--.
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, mechanical pulp either from a single stage or two-stage refining, or commercially produced under the designa-tion of -ul~ra high-yield pulps, high-yield pulps, high-yield chemimechanical pulps, interstage thermomechani-cal pulps an~ chemically post-treated mechanical or .
thermomechanical pulps, or may be part of the furnish, e.g. the' refined re~ects in mechanical pulp production or may be whole pulps.
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The process consists of taking the curled pulp at 1,0 high consistency (say 15-35~) in the form of noaules or entangled mass and- subjecting it to heat treatment : , without appreciable drying of the pulp. The tempera-ture and duration of the heat treatment controls the extent to which the curl in the fibres is rendered permanent,~ and this may be ,adjusted to match the a~van-~tages sought. ~
This process may be carried out as a batch p.rocess in a ~digester or as a~continuous p~roce~ss~ t~rough a '' ,' s~'eaming tube maintained at high pressure. ; ' The process may also include the step of incorpora-:
ting a brlg~tening agent during heat trea;tment, to upgrade the brightness while retaining the improved - : ~
pulp properties; or the subsequent steps of brightening or bleaching sequences to upgrade the brightness of the pulps while m~intaining the improved pulp properties;
or indeed may be carried out in brightened pulps there-by also to maintain adequate~ brighkness after heat treatment.
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, Nowhere in the prior art is there disclosed a process in which a separate and sole heat treatment at high consistency and high temperature is given to curled pulp fibres in order to achieve the desired changes in the properties of the wood pulp being treated.
Among the advantages of the process of aspects o this invention in settling in fibre curl in high-yield pulps and mechanical pulps is to provide a means of controlling pulp properties in order to impart high wet-web stretch, work-to-rupture and increased drainage rates. In the case of high-y1eld pulps, in addition to the above wet-web properties, higher dry-sheet tear strength and stretch are also obtained.
Thus, by aspects of this invention, it has been discovered thatwhen lignocellulosic pulp fibres, that have already been made curly, are heat treated at (a) consistencies ~from 10% to 35%, (b) temperatures from 100 C~to 170 C using steam at correspond1ng pressures of 5 psig to 105 psig, (c) for a period of time from 2 minutes to 60 minutes, fibre curl permanently sets 1n place, and the çurl is made resistant to removal in subsequent mechanical action experienced by fibres in the papermaking process. The process of aspects of this~1nvention improves drainage, wet-web stretch, wet-web work-to-rupture and dry-sheet tear strength~and stretch.
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In one variant, the pr~cess is to take a pulp that has been made curly by high-consistency (20-35%) refin-ing, and to set in the curl (and perhaps microcompres-sions) by subjecting it at a high consistency to an elevated temperature te.g. llO~C - 160C) for a brief time (eOg. 1 minute to 1 hour). This set-in curl is resistant to removal by the hot disintegration experi-enced during papermaking. The advantages of such a pulp are: 1. higher wet-web stretch; 2. higher tearing strength; and- 3. better drainage.
The process j may be a batch process, i.e. if the pulp is-placed in a pressure vessel~e.g. a closed re-action vessel -or digester, or it may be a continuous process~e.g through a steaming tube maintaining high pressures. ~ ~-~
The~ temper~ture and duration of the heat treatment - . :
controls the extent to which the curl in the fibres is rendered permanent, and this may be adjusted to match r the advantages sought. Preferred conditions are as follows: temperatures of from above 100 to 170 with .
corresponding stsam pressures of 5 psig to 105 psig and ~for periods from 2 minutes to 60 minutes.
The trsatment according to aspects of this invsn-,. : ., , . , ~
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~ ~ , ^` 1.~704~7 tion has been observed to render fibre curl permanent including fibre twists, kinks and microcompressions~
Either during or after completion of the heat treatment the pulp may then be brightened in accordance with any of the well-known conventional brightening sequences.
In general, pulp fibres obtalned after refininy at high consistency are very curly. For mechanical pulps, if a mlld disintegration treatment at room temperature is made on these pulps, the fibres retain substantially their curliness so as to produce wet webs with high wet-web stretch, work-to-rupture ~and fast drainage.
However, in the~ papermaking~process, pulps receive mechanical action at high temperatures and low consis-tencies so ~that ~their curliness~ls lost. ~ ~It ~is believed that pulps which are~ given standard hot dis-integration~treatment in the 1 aboratory ~at low cansi~s-tency experience similar conditions dur~ing which the carll~ness~is ~lost and the wet-web~ properties~deteri~
orate.
The~ followlng; examples are~ given to ~ lustrate more clearly var~ious embodiments~of the invention. ~In the following examples, the tests were conducted in the following standard~ way:
Wet-web results were obtained following the pro-cedure~ des~crlbed;by ~R.5. Seth,~ M.C. Bsrbe,~ J.C.R.
Williàms and D.H. Page in ~Tappi, Vol. 65, ~o. 3, pp.
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135-138, 1982. ~ ~
Wet-web~percent solids, tenslle strength, stretch and work-to-rupture were obtained on webs prepared by :
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, , , ~1709~7 applying 0.7 kPa and 103 kPa wet-pressing pressures.
The percent stretch to-break was obtained for wet-webs pressed so as to give a breaking length of 100 meters. It is considered that this value is a measure of the "toughness" of the wet-web and is an iDdication of the runnability of the pulp on a papermachine.
Changes in drainage rates are given by the measure of Canadian Standard Freeness.
Hot disintegration was done accordlng to the pro-cedure of C.W. Skeet and R.S. Allan in Pulp Paper Mag.
Canada, Vol. 69, ~o. 8, pp. T222-22~;, April l9,1968.
The extent of fibre~curliness has been quantified by an Image Analysls method as described by B.D. Jordan and D.H.~ Page ln the~Proceedlngs of the TAPPI Inter-national Paper Physics Conference, Harrison Hot Sprlngs, B.C.~ (1979~ Hlgh values~ of curl indices reflect curlier~fibres.
In the examples following, two parameters have ;
been used~to follow~the progress of the heat treatment ~ ~
effect. ~ -First the curliness of the fibres has been measured, after a standard hot disintegration treatment at low consistency, that simulates the subsequent treatment that the pulp will~receive in ths papermaking process. ~ ~
Secondly, the ~advantags of this new pulp (after hot disintsgration) has been determined in terms oE the extensibility (percent stretch-to-break) of wet webs prepared from the pulp pressed so as to give a breaking length of 100 metres. It is considered that t~is value . :
is a measure of the "toughness" of the wet sheet, and is an indication of the runnability of ~he pulp on a papermachine.
This example is intended to illustrate that when pulp fibres are given a heat treatment, as described for aspects of this invention, they remain curly even after standard hot disintegration.
In this example pulp fibres were treated in a digester at 150C and at about 22~ consistency for approximately 60 minutes.
The results obtalned after the above treatment on a variety of mechanical, chemlmechanical~and chemical :
wood pulp fibres are reproduced below in Table I.
From the results, it is seen that the heat treat-.
ment produces the desired effects, on wet-web stretch and drainage, for all the lignocelluloslc pulp fibres, e.g., mechanical pulp and high-yield sulphite pulp :
fibres. The treatment has no~effect on cellulosic pulp fibres which~contain llttle or no lignin.
This example illustrates the effec~ o~ the temper-ature of the treatment.
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Lignocellulosic pulp fibres were treated in a digester at temperatures of 110, 130, 150 and 170C for 60 minutes and at approximately 22~ consistency. The results reproduced in Table II were obtained after a standard hot disintegration.
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r This example illustrates the efect of the time for the treatment.
Lignocellulosic pulp fibres at approximately 22%
consistency were treated in a digester at 150C for 2, lO and 60 minutes respectively. The results reproduced in Table III were obtained after a standard hot dis-integration.
It can be seen that the time,~ as well as the temperature (Example 2), control the extent to which the curl in ~the fibres is rendered ~permanent. Both variables can be adjusted to yield pulp with the re~
quired properties sought.
In addition to the ~time~to~ maintain the desired properties of curIy ~fibres and temperature ~of the treatment described above,~ the~extent to which;fibre curl i~s present, after heat treatment~and hot dislnte-gration also~depends on the state of the fibres immedi-ately after~refinlng. In Table~ it can be seen that for two 70%-yield sulphite pulps, ~the one re~ined at 30% consistency, i.e., containing more curly;fibres, .
will~requir~e~a~shorter heat treatment and/or a treat- -ment at a lower temperature~to achieve the same wet-web strength properties~as that `for the pulp~refined at 9%
-.
consistency.
:
This example illustrates the effect of the con- ~
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w ' ~ a~ w ~I ~n . ., -- 22 -- l Lignocellulosic pulp fibres were treated in a digester at 150C for 60 minutes at consistencies of 5, 10, 20, and 25%. For the purposes of this specifica-tion, the term "% consistency" means the percenta~e of oven-dried weight of pulp fibres to the total weight of pulp fibres plus water. The results reproduced in Table IV were obtained after a standard hot disin-tegra-tion.
The effect of the treatment is greater, the higher the consistency of the pulp flbres. The treatment has no effect on pulp fibres at low consistency, typically lower than 5%.
: `
This ~example illustrates the effect of the heat treatment on the wet-web ~and~dry-handsheet properties of high-yield pu~lps.
The lignocellulosic pulp fibres were heat ~treated in a digester at 150C and at about 20% consistency for approximately 60 minutes. For~the pulp fibres, in the high-yield~range, the heat treatment improves, in addi-tion to the wet-web stretch and work to rupture, ~the~
dry~handsheet tear strength and stretch (Table V).
This example illustrates the effect of the pH of the pulp fibres during the~heat treatment. A 70% yield sulphite pulp~ at a pH of 3.2 was heat treated in a digester at 150C and at about 20% consistsncy for approximately 60 minutes. Another sample of the same .... ..
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pulp was sprayed with a solution of sodium carbonate to increase its pH to lO.0 and was also given a heat treatment at the same conditions.
Both heat treated pulps show remarkable improve-ment in wet-web properties and dry;tear strength and stretch over the untreated sample (Table VI). The~puIp heat treated at high pH has higher tear strength due to the proteotive~action of the alkali which reduces the loss in fibre strength through acid hydrolys1s.
,~
This example illustrates the effect of pulp bleaching or brightening agents on the wet-web and dry-~handsheet strength of heat tre~ted~pulp~s.
~ A 70~ yield sulphite pulp was ~bleached~by a con-ventional hydrogen peroxide ~treatment following the heat treatment~at 150C for 60~minutes and 20~ consis-tency. Results are~given ~in Table~ VII for the~pulps after treatment ~wlth dlfferent~;peroxide charges and after a~standard hot disintegration~. The pulp after bleaching ~6till possesses ~all the~ clalmed ~superior properties ~(with the ~exception of~drainage) resulting from the heat treatment done under the conditions dis-: .
closed~in this invention.
EXAMPLE 8 ~ ~
As a further example pulps have been heat treatedin the~ way descrlbe~d earller, with the additicn cf a brightening~agent during the heat treatment~stage.
~A thermomechanical pulp and a 70%-yield sulphite 1, '~ ' , ' ' , TABLE VI
, THE EFFECT OF THE PULP ~IBRE H DURING HEAT TREATMENT
P
_ _ 70% yie ~d sulphite pulp Heat treated pulp at 150C
Untreatedfor 60 minutes and 20%
pulp hotconsistency followed by disintegrated hot disintegration -- : _: : ::
pH of heat treatment ~ ~ 3.2 10.0 - ~ - _ - ~
Pulp and fibre proper~ies ;~
Curl index 0.135 0.237 0.253 ~ CSF (ml) ~ 643~ ~ ~ 610 ~ 672 0.7 kPa~ solids (%) 25.4 ~ ~ 22.1 ~ 26.7 l tensile (m) 103 ~89.5 ~ 67.8 ¦~stretch~(%) ~ 2.67 -15.8 7.38 ~ -~ l work to rupture ~ R~ . 29.1 ~; ; ;~157 ~ 52.6 103 kPa ~ solids ~(%) 29.0 ~ ~ 28.2 ~ ~ 29.4 tPnsilè ~(m)~ ~ 169 ~ ~ 141 ~ 103 ~ ~ ~stretch (%? :~ : ~: 2.54 ~ ~ 9.61 6.19 ~work to rupture~ ~ 34~.4 ~ ~ ~ 142~ ~ ~ ~ ~67.0 : ~ ~ : ~ : :' Wet'Web~stretch st~ ~ 2.89 ~ ~ ~ 13.5 ~ ~ ~ 6.24 100 m breaking~length Dry~handsheet~propertles~ ~ ~ ~ ~ ~
Bulk (cm3~/g)~ 1.72 ~ ~ 1.54~ ~ ~ 1.78 Burst index (kPa.m2/g) 6.70 ~ 4.71 3.43 ~ -Téar index (mN.m2/g~ 8.15 ~ ~9.78 16.41 Breaking length~(m) ~ 9924 ~ ~ 7383 ~ ~ ~5547 % stretch` ~ ¦ ~ ~2~.89 ~ ~ 3.03 ~ ~ 2~99 Toùghnèss index (mJ)~ 167 ~ 137 107 Zero-span b.~l. tkm)~ 16.38 14.95 ~ 14.35 Scattering coeff.~;(cm2/g) 205~ ` 209 263 Tappi opacity~(%)~ ; 74.6 74.9 ;~93.7 Iso-brightness (%)~ ~ ~ 44.4 43.0 21.5 ~Absorption~coeff.~(cm2/g)~ ~ 14.86 ~ ~ ~ 15.22 i ~30-50 --: --: :
1 Refined at O.99~mJ/kg and 18% consistency ~
~:
:: : : ~ ::
7(~ 7 TABLE VII
THE EFFECT OF BLEACHING HEAT-TREATED PULPS
70% Yield Sulphite Pulp1 -After heat treatment at 150~C for Before Heat60 minutes and 20% conslstency Treatmentfollowed by peroxide bleaching Weight of Peroxide on Pulp (%) - O 0-5 1.0 2.0 Pulp and Fibre Properties .
Curl Index 0.138 0.227 0.216 0.209 0.204 CSF (ml)~ 662 607 583 533 524 Wet-Web Properties 0.7 kPa . Solids~(%) 27.4 23.3 22.9 25.0 22.7 TensiIe (m) 91.8 87.7 92.2 93.7 95.9 Stretch (%) 2.19 15.1 12.8 1k.0 16.5 ~ Work to rupture ~19.0 ~ 150 131 165 210 103 kPa . ,Solids (~) ~ 31.8 29.0 28.I 32.8 25.3 Tensile (m) 158 133 139 180 151 Stretch (%) 2.34 9.31 9.26 8.95 8.48 ~Work to rupture ~36.4 ~ 148~ 150 171 162 Wèt'Web stretch at 2.34 ~ 13.02 12.82 13.82 15.0 100 m breaking~ length (~
Dry Handsheet Properties~
Bulk (cm3/gj ` ~ 1.74 ~ 54 1.53 ~ ~ 1.47 ~ 1.49 Burst Index (kPa.m2lg) 6.73 ~ 4.~50 ~ 4.70 5.23 5.18 Tear Index (mN-m2/g) ~ ~ ~ 8.26 10.40 10.75 10.64 10.04 Breaking Length~(m3 ~ 9422 6754 6814 ~ 7389 ~ 7302 i;~ ;
Stretch (X)~ ~ ~ 2.79 ~ 3.26 ; 3.43 3.50 3.48 Toughness Inde~ (mJ) ~ 159 ~ 143 148 170 163 Zero-span b.l.~(km) ~ ~ I6.12 ~ 14.38 ~ 14.42 ~ 14.48 14~.98 Scattering Coeff.~(cm2/g) ~ 208 211 ; 206 ; ~ 196~ 198 Tappi Opacity (~%) ~ 76.3 76.8 61.5~ 68.7 ~ 66.4 Iso-Brightness (%)~ 44.8 42.1 49.3 52.9 56.6 Absorption Coeff. (~cm2/g) 14.88 ~ 16.36 7.02 5.23 4.03 Visual Efficièncy (%) 56.0 53.6 63.5 67.0 70.5 -~
Printing Opacity (~j ~ 86.0 86.6 69.6 77.0 73.7 1 Refined at 0.78 MJ/kg and 24% consistency :: : :~
:
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. .
, pulp at about 30~ consistency were sprayed with a solu-tion of 2% H202, 0.4~ EDTA, 3% Na2SiO3, 0.005% g 4 to bring it to 19% consistency. The pulps were treated at 150C for 10 minutes.
Results are given in Table VIII. Both pulps are higher in visual efficiency than the control and possess all the other desired superior properties.
This example illugtr~ates the effect of the heat treatment on bleached or brightened pulps.
A 70% yield sulphi~e ~palp ~and a thermomechanical pulp at about 30% ~consistency were sprayed with a solu-tion of 2% ~22~ 0-4% EDTA, 3% Na25103 and 0.005% MgS04 to bring it~to~l9% consistency.~The pu1ps reacted with the`chemicals for one hour at ~60C. Afterwards, the pulps were~heat treated at 150C for 10 mlnutes.
Results~ are glven in Table ~IX~for the orl~ginal pulps before~ heat~treatment,~the brightened~ pulps and for both pulps~ after ~heat treatmen~t. The heat treat~
ment~ done~under the condltions~disclosed~herein;on the~
brightened pulp~compared to; the~ orig1nal pulp gaye~
similar~properties while it had higher visual effici-ency.
,.
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TABLE VIII
.
THE EFFECT OF THE ADDITION OF A BRIGHTENING AGENT
TO PULP DURING THE HEAT TREATMENT
. .
:
70% YIELD SULPHITE PULP1 TMp2 Heat Treatment at Heat Treatment at~
150C, 10 minj 19% 150C, 10 min, 19%
consistency with consistency with Before No 0.4% EDTA BeforeNo 0.4% EDTA
Heat Bleaching 3% Na2SiO3 HeatBleaching 3% Na2SiO3 Treatment Chemicals 0.005% MgS04 Treatment Chemicals 0.005% MgS04 Pulp and Fibre Pr perties Curl Index 0.148~ 0.187 0.209 0.106 0.177 0.163 CSF ~(mI) 673 651 685 175 312 293 t Wet'Web Properties 0.7 kPa ~ Solids (%) 26.1 26.5 25.1 20.6 25.9 23.4 ¦ TensiIe~(m) 82.8 92.4 ~ 80.1 110 86.1 96.1 Stretch ~(%) ~ 2.38 3.32 ~5.045.02 10.1 iO.l Work to rupture 20.3 ~ 32.0 ~ 43.7~ 68.4 117 122 I03 kPa ~ Solids (%) ~29~1 32.5 ~ 32.1 ~25.0 ~ 32.3 29.3 Tensile (m) i ~ 143 147 ~ ~ 127~ 167 ~144 150 Stretch (%3 ~ ~ 1.95 ~ 2.~53 ~ 3.49 4.42 8.22 ~ 7.24 : Work to rupture~;27.3 38~ 44.7 ~ 86.8 ~ 159 144 Wet-Reb stretch at ~100 m breaking;length ~(%) ~ ~2.23 ;2.90~ ~ 4.05 ~5.22~ ~ 9.61 ~8.93 ~;
Dry Handsheet Properties :~:: : ~:
Bulk ~cm3/gj ~ ~ ~ 1.81 1.65 1.79~ ~ 2.79 3.10~ 2.;96 Burst Index (kPa.m21g) ~ ~ 6.24 5.78 4.38 2.02 1.~36 ~ ~1.50 Tear Index (mN.m2/g)~ 8.22 7.84 7.84 ~ ~ 8.72 8.27 ~8.94 Breaking Length (m) ~ 9704 9251 ~ 7361 ~ 3625 2469 ~2792 Stretch (X) ~ 2.63; ;2.71~ 2~.32 ~ ~ 2.15~ ~ 2~05~ 2.07 Toughness Index (mJ)~ 150 156 ~ 113 ~ 45 ~ 32~ 37~
2ero-span b.l. (km)~ 16.45 16.23 13.96 11.20 ~ 9.78~ 10.47 Scattering Coeff. (~cm2-/g)~ 219 ;~ 203 238 ~ ~568 568 581 ~ ;
Tappi Opacity (~%)~ 77.2~ 76.1 79.7 93.8 95.1 ~93.3 Iso-Brightness (%) ~ ~ 45.3 ~ 41.7 42.8 ~ 56.0 ~ 50.9 55.8 Absorption Coeff. `(cm2/g)~ 14.68 ~ 15.10 9.22 ~20.23 20.49 9.83 Vlsual~Efficiency~(%)~ 56.6~ 54.3 60.4~ 67.3 ~ 64~4~ 71.2 ;~
Refined at 0.57 MJ/kg~and~ 9% consistency
Newsprint traditionally has been manufactured from a furnish consisting of a mixture of a mechanical pulp and a chemical pulp. Mechanical pulp is used because it imparts certain desired properties to the furnish:
namely, its high light scattering coefficient contri-butes to paper opacity and allows the use of a thinner sheet; its high oil absorbency improves inX acceptance during printing.
Chemical pulps are used because they impart propertie~ to the furnish which improve its run-nability. Runnability refers to properties which allow the wet-web to--be transported at high speed through the forming, pressing and drying sections of a paper-machine and allows the dried paper sheet to be reeled and printed in an acceptable manner. Runnability con-tributes to papermachine and pressroom efficiency.
It is believed that improved runnability in chemi-cal pulp is due to high wet-web strength and drainage rate. Wet and dry stretch are important because they are believed to contribute to preventing concentrations of stress around paper defects, thereby minimizing .
;
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. .
breaks. High drainage rates lower the water content and are believPd to yield a less fragile web.
Mechanical pulps including stone grounc1wood (SG) and pressurized stone groundwood (PSG) can be made to provide wet stretch but only at the expense of poor drainage. Higher quality mec'nanical pulps are obtained by manufacture in open discharge refiners, to produce refiner mechanical pulp (RMP) and in pressurized thermomechanical pulp (TMP). Still further upgraded mechanical pulps were provided by chemical pretreatment of the wood chips prior to refining to provide chemi-mechanical pulp (CMP or CTMP).
U.S. Patent 3,446,699 issued May 27, 1965 to Asplund et al. provided a method for producing mechani-cal and chemimechanical or semichemical pulps from lignocellulose-containing material, in order to provide what was alleged to be improved quality of the ibres with improved defibration.
U.S. Patent 3,55~,428 issued Jan. 26, 1971 to Asplund et al. provided a method for manufacturing chemimechanical pulps involving heating and defibrating the same in an atmosphere of vapour at elevated temper-atures and under corresponding pressure of the impreg-nated chips to provide a more rapid and effective impregnation.
U.S. Patent 4,116,758 issued Sept. 26, 1978 to M.J. Ford provided a process for producing high-yield chemimechanical pulps from woody lignocellulose materi-al by treatment with an aqueous solution of a mixture of sulfite and bisulfite, to provide a pulp which can 'qk~V7 be readily defibered by customary mechanical means to provide a pulp having excellent strength characteris~
tics.
Today's papermaker is ~aced with the problems of decreasing forest resources, an increasing demand for paper products and stringent environmental laws. Low-yield chemical pulps, e.g. sulphite and kraft pulps, contribute highly to such problems~
The fibres of low-yield chemical pulps are known for their desirable dry- and wet-web strength proper-ties. Observations of low-yield chemical fibres in a formed paper sheet indicate that these tend to have a kink and curl which is said to contribute, in an advan-tageous way, to the papermachine runnability and to certain physical properties. Mechanical pulps lack the desirable strength properties to replace, in whole or in part, low-yield chemical pulps, e.g. kraft or sul-phite pulps, in linerboard, newsprint, tissue, printing grades and coated-base grade of paper. Consequently, it has been an aim of the art to improve the physical properties of mechanical and high-yield chemical pulps, so that such improved pulps would be used to replace low-yield chemical pulps.
A number of mechanical devices have been built to produce curled chemical and mechanical fibres in order to improve certain physical properties. Two such mechanical fibre-curling devices are disclosed in H.S.
Hill, U.S. Pat. 2,516,384 and E.F. Erikson U.S. Pat.
3,054,532.
H.S. Hill et al. in Tappi, Vol. 33, No. 1, pp.
76~4~7 36-44, 1950, described a "Curlator" designed to produce curled fibres. The process consisted of rolling fibres into bundles at a consistency of around 15%-35%, followed by dispersion. Advantages claimed were higher wet-web stretch, improved drainage, and higher tear strength and stretch of the finished product. These advantages were at -the expense of certain other proper-ties, notably tensile strength.
W.B. West in Tappi, Vol. 47, No. 6, pp. 313-317, 1964, describes high consistency disc refining to pro-duce the same action.
D.H. Page in Pulp Paper Mag. Canada, Vol. 67, No.
1, pp. T2-12, 1966, showed that the curl introduced was both at a gross level and at a fine level which he called "microcompressions". Both types of curl w~re advantageous.
J.H. De Grâce and D.H. Page in Tappi, Vol. 59, No.
7, pp. 98-101, 1976, showed that curl could be produced adventitiously during bleaching of pulps, by the mechanical action of pumps and stirrers at high con-sistency.
R.P. ICibblewhite and D. Brookes in Appita, Vol.
28, No. 4, pp. 227-231, 1975, claimed that this adven-titious curl could have advantages for practical run-nability of papermachines.
High-consistency mechanical defibration of wood chips is known to produce curled, kinked and twisted fibres. Kinked fibres are known to be particularly effective in developing extensibility in wet webs if the kinks are set in position so that they survive the 7e~7 action of pumps and agitators at low consistency and retain their kinked and curled state in the formed sheet. This ensures enhancement of the wet-web stretch and certain other physical properties.
A number of chemical treatment methods have been reported to enhance and retain fibre curl in a refined pulp. In one, Canadian Patent No. 1,102,969 issued June 16, 1981 to A.J. Kerr et al., improvement in tear-ing strength of the pulp is alleged by the treatment of delignified lignocellulosic or cellulose pulp derived from a chemical, semichemical or chemimechanical pulp-ing process at a pressure of at least one atmosphere, with sufficient gaseous ammonia to be taken up by moist pulp in an amount greater than 3% by weight to weight of oven dried pulp.
In another, Canadian Patent ~o. 1,071,805 issued Feb. 19, 1980 to A.J. Barnet et al., a method of treat-ment of mechanical wood pulp is provided by cooking the pulp with aqueous sodium sulphite solution containing sufficient alkali to maintain a pH greater than about 3 during the cooking. The cooklng was effected at an elevated temperature for a time sufficient to cause reaction with the pulp and to increase the drainage and wet stretch thereof, but for a time insufficient to cause substantlal dissolution of liquor from the pulp, and insufficient to result in a pulp yield below about 90~. A minimum concentration of sodium sulphite was 1%
since, below 1% sodium sulphite improvements were said to be too small to justify the expense of treatment.
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-: During the process of papermaXing, most of the curl in both high-consistency refined mechanical and hi~h-yield sulphi~e pulp is lost in the subsequent steps of hanaling at low consistency and high tempera-tures. This is also taught in the article by H.W.H.
Jones in Pulp Paper Mag. Canada, Vol. 67, No 6, pp.
T2~3-291, 1966. Jones showed that when mechanical pulp fibres which are curled during high consistency refin-ing are subjected to mild mechanical action in dilute suspension at a temperature of arouna 70C the curl tends to be removed. The increased tensile and burst strengths produced by removal of curl was seen as advantageous. Thus, curl in such pulps is normally removed in ~apermachine operation, since auring practi-cal papermaking, pulps are always subjected to mild mechanical action ln dilute suspension at temperatures of the order of 70C.
High-yleld and ultra high-yield sulphite pulps are used as reinforcing pulps for manufacture of newsprint and othe~ groundwood-containing papers. Although they ~ay be subjected to high-consistency refining, their fibres are in practice substantially straight because the curl introduced in high-consistency refining is lost in subsequent handling.
Accordingly an object of one aspect of this inven-tion is to provide a process for imparting and render-ing permanent, the physical properties of such mechani-cal and high-yield chemical pulps in order to improve their papermachine runnability and pressroom effici-' ~ ~ ency. 117~7 An object of another aspect of this invention is to providea non-chemical process of treating higher-yield pulps ta improve and retain certain physical properties so that the pulp can be used to replace in whole or in part, the low-yield chemical pulps.
It is an object of yet another aspect of the present inven-tion to render permanent, by non-chemical means, the curl imparted ,,, ~, ., . ,, .. .. .. ._ . , . --to the fibres of high-consistency mechanically treated, mechanical and high-yield chemical pulps.
The mechanicaI pulps or high-yield chemical pulps included within the ambit of various aspect~s of this inventlon can be produced by either mechanical deflbration of wood, e.g. in stone groundwood (SG), pressurized stone groundwood (PSG), refiner mechanical pulp (RMP) and thermomechanical pulp (TMPj production or by mechanical defibration, at high~consistency, followed or preceded by a chemical :. , : . .
treatment of wood chips~and pulps e.g.~in the production of ultra-high-yield sulphite pulps (UHYS, yie;lds~ in the range 100-85%), high-: : : : :
yield sulphlte~pulp~s (HYS, yields ln the range 85-65%),~chemi-thermo-mechanical (C1`MP), high-yield chemimechanical (CMP), lnterstage~ ~
thermomechanical and chemically~post-treated mechanical pulp (MPC) - or~thermomechanical~pulps (TMPC) By~ a broad aspect of this invention`, a process is provided for treating pulps, that havè already;been curled, in order to im-~prove at least some~of the following physical properties: drainage, :
wet-ueb stretch, wet-web work-to-rupture, and dry-sheet tear strength and stretch,~which process comprises: sobjecting the curled pulp .
fibres to a heat treatment while said pulp is at a high consistency ~ ;
in the form of nodules or entangled mass, without appreciable drying of the pulp, the heat treatment being at an elevated temperature and for a time sufficient to render the curl permanent to subsequent ~mechanical action, which process comprises: subjecting the curled pulp to a heat treatment, e.g., at a treatmcnt of at least 100 C, ~:~7~
preferably 100C-170C, for a sufficient length of time, e.g., between 60 minutes and 2 minutes, inversely dependent on the temperature while curled pulp is at a high consistency, e.g., at least 15%, preferably 15% to 35%, in the form of nodules or entangled masses, thereby to render the curl per-manent to subsequent mechanical action.
The present invention in its broad aspects is a process which fol-lows the mechanical action that the already made the fibres curly in either mechanical, ultra high-yield or high-yield pulps. Such a mechanical action generally takes place at high consistency (15%-35%), and may typically be a high-consistency disc refining action, e.g. as is generally used io pulp manufacture. ~ ;
The process of aspects of this invention thus consists of a simple heat treatment of the pulp in the presence of water while it is retained in the form of nodules or entangled mass at a high consistency. The process preferably involves temperatures ahove;100 C, ln which case a pressure vessel is required.
Wh~le the inven~tion is not to be limited to any theory, it is believed that the process sets~the curl in place e~ther by relief of stresses in the Eibre or by a cross-linking~mechanism, so that~upon subsequent pro-cessing during papermaking, the~fibres retain their curled form. ,~
This curled form has particular advantàges for the propertibs~of~
, the wet web, so that the runnability of the papermachine is improved. In addition, the toughness of the finished produce is increased.
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ln gcncral tcr~s~ thc pr3C~ss b~ins ~it}, a p~llp tl~a~ has becn converted to the curly state by mechanical action at hi~h consistency, and in whichthe fibres are held in a curly s~ate in the or~, of nodules or en-tangled mass. The pulp may be either purely mechanical, e.g, stone ground-wood, pressurized stone groundwood, refiner mechanical, thcrnlomechanlcal, or a chemimechanical pulp, e.g., ultra high-yield sulphite pulp or high-yield sulphite pulp. Conversion to a curly state is generally achie~ed naturally in the high-consistency refining actionthat is normally used for refiner mechanical, theremomechanical and ultra high-yield sulphite pulp. For stone groundwood, pressurized stone groundwood and high-yield sulphite pulp, it would be necessary to add, to the normal processing, a step that curls the .- fibres. This may be for example by use of a machine~known by the Trade Mark of CURLATOR or high-consistency disc refining, or by use of a machlne known by the Trade Mark FROTAPULPER (See E.F. Erikson, U.S. Pat. 3,054,532).
`~ The pulp fibres may be lignocellulos~c fibres produced by mechanlcal , defibratlon, or by refining, or by refin~ng in a disc ref~ner at high consis-tency, or by mechanical deflbratlon at high consistency of wood chips, or by mechanical defibration at hlgh consistency of wood chips followed or preceded by a chem~cal t~reatment, or by a slngle stage~refining~, or after two successive~refinings, or between two~successive refinings. They may~ ;
alternatively be pulp fibres commercially~produced under the designation o~f refIner mechanical pulp, pressurized~reflner meGhanicalpulp ànd thermo--.
. . . . .
-:
~:
:
- - ' , ': ` '~ - ' ' ` ' ' ' . ' ' :: :
, mechanical pulp either from a single stage or two-stage refining, or commercially produced under the designa-tion of -ul~ra high-yield pulps, high-yield pulps, high-yield chemimechanical pulps, interstage thermomechani-cal pulps an~ chemically post-treated mechanical or .
thermomechanical pulps, or may be part of the furnish, e.g. the' refined re~ects in mechanical pulp production or may be whole pulps.
. .
The process consists of taking the curled pulp at 1,0 high consistency (say 15-35~) in the form of noaules or entangled mass and- subjecting it to heat treatment : , without appreciable drying of the pulp. The tempera-ture and duration of the heat treatment controls the extent to which the curl in the fibres is rendered permanent,~ and this may be ,adjusted to match the a~van-~tages sought. ~
This process may be carried out as a batch p.rocess in a ~digester or as a~continuous p~roce~ss~ t~rough a '' ,' s~'eaming tube maintained at high pressure. ; ' The process may also include the step of incorpora-:
ting a brlg~tening agent during heat trea;tment, to upgrade the brightness while retaining the improved - : ~
pulp properties; or the subsequent steps of brightening or bleaching sequences to upgrade the brightness of the pulps while m~intaining the improved pulp properties;
or indeed may be carried out in brightened pulps there-by also to maintain adequate~ brighkness after heat treatment.
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7~3~
, Nowhere in the prior art is there disclosed a process in which a separate and sole heat treatment at high consistency and high temperature is given to curled pulp fibres in order to achieve the desired changes in the properties of the wood pulp being treated.
Among the advantages of the process of aspects o this invention in settling in fibre curl in high-yield pulps and mechanical pulps is to provide a means of controlling pulp properties in order to impart high wet-web stretch, work-to-rupture and increased drainage rates. In the case of high-y1eld pulps, in addition to the above wet-web properties, higher dry-sheet tear strength and stretch are also obtained.
Thus, by aspects of this invention, it has been discovered thatwhen lignocellulosic pulp fibres, that have already been made curly, are heat treated at (a) consistencies ~from 10% to 35%, (b) temperatures from 100 C~to 170 C using steam at correspond1ng pressures of 5 psig to 105 psig, (c) for a period of time from 2 minutes to 60 minutes, fibre curl permanently sets 1n place, and the çurl is made resistant to removal in subsequent mechanical action experienced by fibres in the papermaking process. The process of aspects of this~1nvention improves drainage, wet-web stretch, wet-web work-to-rupture and dry-sheet tear strength~and stretch.
:
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In one variant, the pr~cess is to take a pulp that has been made curly by high-consistency (20-35%) refin-ing, and to set in the curl (and perhaps microcompres-sions) by subjecting it at a high consistency to an elevated temperature te.g. llO~C - 160C) for a brief time (eOg. 1 minute to 1 hour). This set-in curl is resistant to removal by the hot disintegration experi-enced during papermaking. The advantages of such a pulp are: 1. higher wet-web stretch; 2. higher tearing strength; and- 3. better drainage.
The process j may be a batch process, i.e. if the pulp is-placed in a pressure vessel~e.g. a closed re-action vessel -or digester, or it may be a continuous process~e.g through a steaming tube maintaining high pressures. ~ ~-~
The~ temper~ture and duration of the heat treatment - . :
controls the extent to which the curl in the fibres is rendered permanent, and this may be adjusted to match r the advantages sought. Preferred conditions are as follows: temperatures of from above 100 to 170 with .
corresponding stsam pressures of 5 psig to 105 psig and ~for periods from 2 minutes to 60 minutes.
The trsatment according to aspects of this invsn-,. : ., , . , ~
, . . . . .
: , . .
..
.
~ :
~ ~ , ^` 1.~704~7 tion has been observed to render fibre curl permanent including fibre twists, kinks and microcompressions~
Either during or after completion of the heat treatment the pulp may then be brightened in accordance with any of the well-known conventional brightening sequences.
In general, pulp fibres obtalned after refininy at high consistency are very curly. For mechanical pulps, if a mlld disintegration treatment at room temperature is made on these pulps, the fibres retain substantially their curliness so as to produce wet webs with high wet-web stretch, work-to-rupture ~and fast drainage.
However, in the~ papermaking~process, pulps receive mechanical action at high temperatures and low consis-tencies so ~that ~their curliness~ls lost. ~ ~It ~is believed that pulps which are~ given standard hot dis-integration~treatment in the 1 aboratory ~at low cansi~s-tency experience similar conditions dur~ing which the carll~ness~is ~lost and the wet-web~ properties~deteri~
orate.
The~ followlng; examples are~ given to ~ lustrate more clearly var~ious embodiments~of the invention. ~In the following examples, the tests were conducted in the following standard~ way:
Wet-web results were obtained following the pro-cedure~ des~crlbed;by ~R.5. Seth,~ M.C. Bsrbe,~ J.C.R.
Williàms and D.H. Page in ~Tappi, Vol. 65, ~o. 3, pp.
:
135-138, 1982. ~ ~
Wet-web~percent solids, tenslle strength, stretch and work-to-rupture were obtained on webs prepared by :
: - :
, , , ~1709~7 applying 0.7 kPa and 103 kPa wet-pressing pressures.
The percent stretch to-break was obtained for wet-webs pressed so as to give a breaking length of 100 meters. It is considered that this value is a measure of the "toughness" of the wet-web and is an iDdication of the runnability of the pulp on a papermachine.
Changes in drainage rates are given by the measure of Canadian Standard Freeness.
Hot disintegration was done accordlng to the pro-cedure of C.W. Skeet and R.S. Allan in Pulp Paper Mag.
Canada, Vol. 69, ~o. 8, pp. T222-22~;, April l9,1968.
The extent of fibre~curliness has been quantified by an Image Analysls method as described by B.D. Jordan and D.H.~ Page ln the~Proceedlngs of the TAPPI Inter-national Paper Physics Conference, Harrison Hot Sprlngs, B.C.~ (1979~ Hlgh values~ of curl indices reflect curlier~fibres.
In the examples following, two parameters have ;
been used~to follow~the progress of the heat treatment ~ ~
effect. ~ -First the curliness of the fibres has been measured, after a standard hot disintegration treatment at low consistency, that simulates the subsequent treatment that the pulp will~receive in ths papermaking process. ~ ~
Secondly, the ~advantags of this new pulp (after hot disintsgration) has been determined in terms oE the extensibility (percent stretch-to-break) of wet webs prepared from the pulp pressed so as to give a breaking length of 100 metres. It is considered that t~is value . :
is a measure of the "toughness" of the wet sheet, and is an indication of the runnability of ~he pulp on a papermachine.
This example is intended to illustrate that when pulp fibres are given a heat treatment, as described for aspects of this invention, they remain curly even after standard hot disintegration.
In this example pulp fibres were treated in a digester at 150C and at about 22~ consistency for approximately 60 minutes.
The results obtalned after the above treatment on a variety of mechanical, chemlmechanical~and chemical :
wood pulp fibres are reproduced below in Table I.
From the results, it is seen that the heat treat-.
ment produces the desired effects, on wet-web stretch and drainage, for all the lignocelluloslc pulp fibres, e.g., mechanical pulp and high-yield sulphite pulp :
fibres. The treatment has no~effect on cellulosic pulp fibres which~contain llttle or no lignin.
This example illustrates the effec~ o~ the temper-ature of the treatment.
:: :
Lignocellulosic pulp fibres were treated in a digester at temperatures of 110, 130, 150 and 170C for 60 minutes and at approximately 22~ consistency. The results reproduced in Table II were obtained after a standard hot disintegration.
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r This example illustrates the efect of the time for the treatment.
Lignocellulosic pulp fibres at approximately 22%
consistency were treated in a digester at 150C for 2, lO and 60 minutes respectively. The results reproduced in Table III were obtained after a standard hot dis-integration.
It can be seen that the time,~ as well as the temperature (Example 2), control the extent to which the curl in ~the fibres is rendered ~permanent. Both variables can be adjusted to yield pulp with the re~
quired properties sought.
In addition to the ~time~to~ maintain the desired properties of curIy ~fibres and temperature ~of the treatment described above,~ the~extent to which;fibre curl i~s present, after heat treatment~and hot dislnte-gration also~depends on the state of the fibres immedi-ately after~refinlng. In Table~ it can be seen that for two 70%-yield sulphite pulps, ~the one re~ined at 30% consistency, i.e., containing more curly;fibres, .
will~requir~e~a~shorter heat treatment and/or a treat- -ment at a lower temperature~to achieve the same wet-web strength properties~as that `for the pulp~refined at 9%
-.
consistency.
:
This example illustrates the effect of the con- ~
:' sistency of the pulp fibres~when submitted to heat treatment.
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w ' ~ a~ w ~I ~n . ., -- 22 -- l Lignocellulosic pulp fibres were treated in a digester at 150C for 60 minutes at consistencies of 5, 10, 20, and 25%. For the purposes of this specifica-tion, the term "% consistency" means the percenta~e of oven-dried weight of pulp fibres to the total weight of pulp fibres plus water. The results reproduced in Table IV were obtained after a standard hot disin-tegra-tion.
The effect of the treatment is greater, the higher the consistency of the pulp flbres. The treatment has no effect on pulp fibres at low consistency, typically lower than 5%.
: `
This ~example illustrates the effect of the heat treatment on the wet-web ~and~dry-handsheet properties of high-yield pu~lps.
The lignocellulosic pulp fibres were heat ~treated in a digester at 150C and at about 20% consistency for approximately 60 minutes. For~the pulp fibres, in the high-yield~range, the heat treatment improves, in addi-tion to the wet-web stretch and work to rupture, ~the~
dry~handsheet tear strength and stretch (Table V).
This example illustrates the effect of the pH of the pulp fibres during the~heat treatment. A 70% yield sulphite pulp~ at a pH of 3.2 was heat treated in a digester at 150C and at about 20% consistsncy for approximately 60 minutes. Another sample of the same .... ..
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pulp was sprayed with a solution of sodium carbonate to increase its pH to lO.0 and was also given a heat treatment at the same conditions.
Both heat treated pulps show remarkable improve-ment in wet-web properties and dry;tear strength and stretch over the untreated sample (Table VI). The~puIp heat treated at high pH has higher tear strength due to the proteotive~action of the alkali which reduces the loss in fibre strength through acid hydrolys1s.
,~
This example illustrates the effect of pulp bleaching or brightening agents on the wet-web and dry-~handsheet strength of heat tre~ted~pulp~s.
~ A 70~ yield sulphite pulp was ~bleached~by a con-ventional hydrogen peroxide ~treatment following the heat treatment~at 150C for 60~minutes and 20~ consis-tency. Results are~given ~in Table~ VII for the~pulps after treatment ~wlth dlfferent~;peroxide charges and after a~standard hot disintegration~. The pulp after bleaching ~6till possesses ~all the~ clalmed ~superior properties ~(with the ~exception of~drainage) resulting from the heat treatment done under the conditions dis-: .
closed~in this invention.
EXAMPLE 8 ~ ~
As a further example pulps have been heat treatedin the~ way descrlbe~d earller, with the additicn cf a brightening~agent during the heat treatment~stage.
~A thermomechanical pulp and a 70%-yield sulphite 1, '~ ' , ' ' , TABLE VI
, THE EFFECT OF THE PULP ~IBRE H DURING HEAT TREATMENT
P
_ _ 70% yie ~d sulphite pulp Heat treated pulp at 150C
Untreatedfor 60 minutes and 20%
pulp hotconsistency followed by disintegrated hot disintegration -- : _: : ::
pH of heat treatment ~ ~ 3.2 10.0 - ~ - _ - ~
Pulp and fibre proper~ies ;~
Curl index 0.135 0.237 0.253 ~ CSF (ml) ~ 643~ ~ ~ 610 ~ 672 0.7 kPa~ solids (%) 25.4 ~ ~ 22.1 ~ 26.7 l tensile (m) 103 ~89.5 ~ 67.8 ¦~stretch~(%) ~ 2.67 -15.8 7.38 ~ -~ l work to rupture ~ R~ . 29.1 ~; ; ;~157 ~ 52.6 103 kPa ~ solids ~(%) 29.0 ~ ~ 28.2 ~ ~ 29.4 tPnsilè ~(m)~ ~ 169 ~ ~ 141 ~ 103 ~ ~ ~stretch (%? :~ : ~: 2.54 ~ ~ 9.61 6.19 ~work to rupture~ ~ 34~.4 ~ ~ ~ 142~ ~ ~ ~ ~67.0 : ~ ~ : ~ : :' Wet'Web~stretch st~ ~ 2.89 ~ ~ ~ 13.5 ~ ~ ~ 6.24 100 m breaking~length Dry~handsheet~propertles~ ~ ~ ~ ~ ~
Bulk (cm3~/g)~ 1.72 ~ ~ 1.54~ ~ ~ 1.78 Burst index (kPa.m2/g) 6.70 ~ 4.71 3.43 ~ -Téar index (mN.m2/g~ 8.15 ~ ~9.78 16.41 Breaking length~(m) ~ 9924 ~ ~ 7383 ~ ~ ~5547 % stretch` ~ ¦ ~ ~2~.89 ~ ~ 3.03 ~ ~ 2~99 Toùghnèss index (mJ)~ 167 ~ 137 107 Zero-span b.~l. tkm)~ 16.38 14.95 ~ 14.35 Scattering coeff.~;(cm2/g) 205~ ` 209 263 Tappi opacity~(%)~ ; 74.6 74.9 ;~93.7 Iso-brightness (%)~ ~ ~ 44.4 43.0 21.5 ~Absorption~coeff.~(cm2/g)~ ~ 14.86 ~ ~ ~ 15.22 i ~30-50 --: --: :
1 Refined at O.99~mJ/kg and 18% consistency ~
~:
:: : : ~ ::
7(~ 7 TABLE VII
THE EFFECT OF BLEACHING HEAT-TREATED PULPS
70% Yield Sulphite Pulp1 -After heat treatment at 150~C for Before Heat60 minutes and 20% conslstency Treatmentfollowed by peroxide bleaching Weight of Peroxide on Pulp (%) - O 0-5 1.0 2.0 Pulp and Fibre Properties .
Curl Index 0.138 0.227 0.216 0.209 0.204 CSF (ml)~ 662 607 583 533 524 Wet-Web Properties 0.7 kPa . Solids~(%) 27.4 23.3 22.9 25.0 22.7 TensiIe (m) 91.8 87.7 92.2 93.7 95.9 Stretch (%) 2.19 15.1 12.8 1k.0 16.5 ~ Work to rupture ~19.0 ~ 150 131 165 210 103 kPa . ,Solids (~) ~ 31.8 29.0 28.I 32.8 25.3 Tensile (m) 158 133 139 180 151 Stretch (%) 2.34 9.31 9.26 8.95 8.48 ~Work to rupture ~36.4 ~ 148~ 150 171 162 Wèt'Web stretch at 2.34 ~ 13.02 12.82 13.82 15.0 100 m breaking~ length (~
Dry Handsheet Properties~
Bulk (cm3/gj ` ~ 1.74 ~ 54 1.53 ~ ~ 1.47 ~ 1.49 Burst Index (kPa.m2lg) 6.73 ~ 4.~50 ~ 4.70 5.23 5.18 Tear Index (mN-m2/g) ~ ~ ~ 8.26 10.40 10.75 10.64 10.04 Breaking Length~(m3 ~ 9422 6754 6814 ~ 7389 ~ 7302 i;~ ;
Stretch (X)~ ~ ~ 2.79 ~ 3.26 ; 3.43 3.50 3.48 Toughness Inde~ (mJ) ~ 159 ~ 143 148 170 163 Zero-span b.l.~(km) ~ ~ I6.12 ~ 14.38 ~ 14.42 ~ 14.48 14~.98 Scattering Coeff.~(cm2/g) ~ 208 211 ; 206 ; ~ 196~ 198 Tappi Opacity (~%) ~ 76.3 76.8 61.5~ 68.7 ~ 66.4 Iso-Brightness (%)~ 44.8 42.1 49.3 52.9 56.6 Absorption Coeff. (~cm2/g) 14.88 ~ 16.36 7.02 5.23 4.03 Visual Efficièncy (%) 56.0 53.6 63.5 67.0 70.5 -~
Printing Opacity (~j ~ 86.0 86.6 69.6 77.0 73.7 1 Refined at 0.78 MJ/kg and 24% consistency :: : :~
:
:
:; :
I
. .
, pulp at about 30~ consistency were sprayed with a solu-tion of 2% H202, 0.4~ EDTA, 3% Na2SiO3, 0.005% g 4 to bring it to 19% consistency. The pulps were treated at 150C for 10 minutes.
Results are given in Table VIII. Both pulps are higher in visual efficiency than the control and possess all the other desired superior properties.
This example illugtr~ates the effect of the heat treatment on bleached or brightened pulps.
A 70% yield sulphi~e ~palp ~and a thermomechanical pulp at about 30% ~consistency were sprayed with a solu-tion of 2% ~22~ 0-4% EDTA, 3% Na25103 and 0.005% MgS04 to bring it~to~l9% consistency.~The pu1ps reacted with the`chemicals for one hour at ~60C. Afterwards, the pulps were~heat treated at 150C for 10 mlnutes.
Results~ are glven in Table ~IX~for the orl~ginal pulps before~ heat~treatment,~the brightened~ pulps and for both pulps~ after ~heat treatmen~t. The heat treat~
ment~ done~under the condltions~disclosed~herein;on the~
brightened pulp~compared to; the~ orig1nal pulp gaye~
similar~properties while it had higher visual effici-ency.
,.
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TABLE VIII
.
THE EFFECT OF THE ADDITION OF A BRIGHTENING AGENT
TO PULP DURING THE HEAT TREATMENT
. .
:
70% YIELD SULPHITE PULP1 TMp2 Heat Treatment at Heat Treatment at~
150C, 10 minj 19% 150C, 10 min, 19%
consistency with consistency with Before No 0.4% EDTA BeforeNo 0.4% EDTA
Heat Bleaching 3% Na2SiO3 HeatBleaching 3% Na2SiO3 Treatment Chemicals 0.005% MgS04 Treatment Chemicals 0.005% MgS04 Pulp and Fibre Pr perties Curl Index 0.148~ 0.187 0.209 0.106 0.177 0.163 CSF ~(mI) 673 651 685 175 312 293 t Wet'Web Properties 0.7 kPa ~ Solids (%) 26.1 26.5 25.1 20.6 25.9 23.4 ¦ TensiIe~(m) 82.8 92.4 ~ 80.1 110 86.1 96.1 Stretch ~(%) ~ 2.38 3.32 ~5.045.02 10.1 iO.l Work to rupture 20.3 ~ 32.0 ~ 43.7~ 68.4 117 122 I03 kPa ~ Solids (%) ~29~1 32.5 ~ 32.1 ~25.0 ~ 32.3 29.3 Tensile (m) i ~ 143 147 ~ ~ 127~ 167 ~144 150 Stretch (%3 ~ ~ 1.95 ~ 2.~53 ~ 3.49 4.42 8.22 ~ 7.24 : Work to rupture~;27.3 38~ 44.7 ~ 86.8 ~ 159 144 Wet-Reb stretch at ~100 m breaking;length ~(%) ~ ~2.23 ;2.90~ ~ 4.05 ~5.22~ ~ 9.61 ~8.93 ~;
Dry Handsheet Properties :~:: : ~:
Bulk ~cm3/gj ~ ~ ~ 1.81 1.65 1.79~ ~ 2.79 3.10~ 2.;96 Burst Index (kPa.m21g) ~ ~ 6.24 5.78 4.38 2.02 1.~36 ~ ~1.50 Tear Index (mN.m2/g)~ 8.22 7.84 7.84 ~ ~ 8.72 8.27 ~8.94 Breaking Length (m) ~ 9704 9251 ~ 7361 ~ 3625 2469 ~2792 Stretch (X) ~ 2.63; ;2.71~ 2~.32 ~ ~ 2.15~ ~ 2~05~ 2.07 Toughness Index (mJ)~ 150 156 ~ 113 ~ 45 ~ 32~ 37~
2ero-span b.l. (km)~ 16.45 16.23 13.96 11.20 ~ 9.78~ 10.47 Scattering Coeff. (~cm2-/g)~ 219 ;~ 203 238 ~ ~568 568 581 ~ ;
Tappi Opacity (~%)~ 77.2~ 76.1 79.7 93.8 95.1 ~93.3 Iso-Brightness (%) ~ ~ 45.3 ~ 41.7 42.8 ~ 56.0 ~ 50.9 55.8 Absorption Coeff. `(cm2/g)~ 14.68 ~ 15.10 9.22 ~20.23 20.49 9.83 Vlsual~Efficiency~(%)~ 56.6~ 54.3 60.4~ 67.3 ~ 64~4~ 71.2 ;~
Refined at 0.57 MJ/kg~and~ 9% consistency
2 Refined at 8.52 MJ/kg and~35%~consistency afeer second stage : ~:
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Claims (23)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for treating pulp fibres, that have already been curled in order to improve at least some of the following phy-sical properties: drainage, wet-web stretch, wet-web work-to-rupture, and dry-sheet tear strength and stretch, which process comprises:
subjecting said curled pulp fibres to a heat treatment while said pulp is at a high consistency in the form of nodules or entangle mass, without appreciable drying of the pulp, said heat treatment being at an elevated temperature and for a time sufficient to render said curl permanent to subsequent mechanical action.
subjecting said curled pulp fibres to a heat treatment while said pulp is at a high consistency in the form of nodules or entangle mass, without appreciable drying of the pulp, said heat treatment being at an elevated temperature and for a time sufficient to render said curl permanent to subsequent mechanical action.
2. A process for treating high yield or mechanical pulp fibres that have already been curled by a high consistency action, in order to improve at least some of the following physical proper-ties: drainage, wet-web stretch, wet-web work-to-rupture, and dry-sheet tear strength and stretch, which process comprises: subjecting said curled pulp fibers to a heat treatment at a temperature of at least 100°C, while said curled pulp is in the form of nodules or en-tangld mass at a high consistency of at least 15%, without appreciable drying of the pulp, said heat treatment being for a sufficient time at said temperature to render said curl permanent to subsequent mechanical action.
3. A process for treating high yield or mechanical pulps that have already been curled by a high consistency action in order to improve at least some of the following physical properties: drain-age, wet-web stretch, wet-web work-to-rupture, and dry-sheet tear strength and stretch, which process comprises: subjecting said curled pulp fibres to a heat treatment at a temperature of 100°C-170°C for a time varying between 60 minutes and 2 minutes, while said curled pulp is at a high consistency of 15% to 35% in the form of nodules or entangled mass, said heat treatment thus being suf-ficient to render said curl permanent to subsequent mechanical action.
4. The process of claims 1, 2 or 3 wherein said heat treatment is carried out as a batch process in a digester.
5. The process of claims 1, 2 or 3 wherein said heat treatment is carried out as a continuous process through a steaming tube maintained at high pressure.
6. The process of claims 1, 2 or 3 wherein said pulp fibres are lignocellulosic pulp fibres produced by mechanical defibration.
7. The process of claims 1, 2 or 3 wherein said pulp fibres are lignocellulosic pulp fibres produced by refining.
8. The process of claims 1, 2 or 3 wherein said pulp fibres are lignocellulosic pulp fibres produced by refining in a disc refiner at high consistency.
9. The process of claims 1, 2 or 3 wherein said pulp fibres are lignocellulosic fibres produced by treatment in a mechan-ical fiber-curling device.
10. The process of claims 1, 2 or 3 wherein said pulp fibres are lignocellulosic fibres produced by mechanical defi-bration of wood chips at high consistency.
11. The process of claims 1, 2 or 3 wherein said pulp fibres are lignocellulosic fibres produced by mechanical defi-bration of wood chips at high consistency followed or preceded by a chemical treatment.
12. The process of claims 1, 2 or 3 wherein said pulp fibres are lignocellulosic pulp fibres obtained after a single stage refining.
13. The process of claims 1, 2 or 3 wherein said pulp fibres are lignocellulosic pulp fibres obtained after two successive refinings.
14. The process of claims 1, 2 or 3 wherein said pulp fibres are lignocellulosic pulp fibres obtained between two succes-sive refinings.
15. The process of claims 1, 2 or 3 wherein said pulp fibres are lignocellulosic pulp fibres at neutral or alkaline pH.
16. The process of claims 1, 2 or 3 wherein said pulp fibres are refiner mechanical pulp, pressurized refiner mechanical pulp or thermomechanical pulp, either from a single stage or two-stage refining.
17. The process of claims 1, 2 or 3 wherein said pulp fibres are ultra-high yield pulps, high-yield pulps, high-yield chemi-thermomechanical pulps, chemimechanical pulps, interstage thermomechanical pulps for chemically post-treated mechanical pulps or chemically post-treated thermomechanical pulps.
18. The process of claims 1, 2 or 3 wherein said pulp fibres are part of a furnish.
19. The process of claims 1, 2 or 3 wherein said pulp fibres are the refined rejects in mechanical pulp production or high yield pulp production.
20. The process of claims 1, 2 or 3 wherein said pulp fibres are whole pulps of a furnish.
21. The process of claims 1, 2 or 3 including the step of incorporating a brightening agent during heat treatment, to up-grade the brightness while retaining the improved pulp properties.
22. The process of claims 1, 2 or 3 including the sub-sequent steps of brightening or bleaching sequences to upgrade the brightness of the pulps while maintaining the improved pulp pro-perties.
23. The process of claims 1, 2 or 3 wherein said pulps, are brightened pulps, thereby to maintain adequate brightness after heat treatment as well as the improved pulp properties.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NZ20401983A NZ204019A (en) | 1982-05-11 | 1983-04-27 | Heat treatment of pulp fibres |
| EP19830302424 EP0096460B1 (en) | 1982-05-11 | 1983-04-29 | Process for improving and retaining pulp properties |
| FI831626A FI74052C (en) | 1982-05-11 | 1983-05-10 | Process for improving and preserving the properties of a cellulose pulp |
| AU14392/83A AU559355B2 (en) | 1982-05-11 | 1983-05-10 | Retaining fibre curl in pulp |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000377111A CA1142012A (en) | 1980-07-14 | 1981-05-07 | Drive mechanism |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1170487A true CA1170487A (en) | 1984-07-10 |
Family
ID=4119908
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000402701A Expired CA1170487A (en) | 1981-05-07 | 1982-05-11 | Process for improving and retaining pulp properties |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1170487A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2000039388A1 (en) * | 1998-12-30 | 2000-07-06 | Kimberly-Clark Worldwide, Inc. | High bulk, high strength fiber material with permanent fiber morphology |
| WO2000039387A2 (en) * | 1998-12-30 | 2000-07-06 | Kimberly-Clark Worldwide, Inc. | Steam explosion treatment with addition of chemicals |
| US6413362B1 (en) | 1999-11-24 | 2002-07-02 | Kimberly-Clark Worldwide, Inc. | Method of steam treating low yield papermaking fibers to produce a permanent curl |
| US6506282B2 (en) | 1998-12-30 | 2003-01-14 | Kimberly-Clark Worldwide, Inc. | Steam explosion treatment with addition of chemicals |
-
1982
- 1982-05-11 CA CA000402701A patent/CA1170487A/en not_active Expired
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2000039388A1 (en) * | 1998-12-30 | 2000-07-06 | Kimberly-Clark Worldwide, Inc. | High bulk, high strength fiber material with permanent fiber morphology |
| WO2000039387A2 (en) * | 1998-12-30 | 2000-07-06 | Kimberly-Clark Worldwide, Inc. | Steam explosion treatment with addition of chemicals |
| WO2000039387A3 (en) * | 1998-12-30 | 2000-11-23 | Kimberly Clark Co | Steam explosion treatment with addition of chemicals |
| GB2361481A (en) * | 1998-12-30 | 2001-10-24 | Kimberly Clark Co | Steam explosion treatement with addition of chemicals |
| GB2361482A (en) * | 1998-12-30 | 2001-10-24 | Kimberly Clark Co | High bulk high strength fiber material with permanent fiber morphology |
| US6506282B2 (en) | 1998-12-30 | 2003-01-14 | Kimberly-Clark Worldwide, Inc. | Steam explosion treatment with addition of chemicals |
| GB2361481B (en) * | 1998-12-30 | 2003-03-12 | Kimberly Clark Co | Steam explosion treatement with addition of chemicals |
| GB2361482B (en) * | 1998-12-30 | 2003-06-04 | Kimberly Clark Co | High bulk high strength fiber material with permanent fiber morphology |
| US6413362B1 (en) | 1999-11-24 | 2002-07-02 | Kimberly-Clark Worldwide, Inc. | Method of steam treating low yield papermaking fibers to produce a permanent curl |
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