CA2192570A1 - A light drainability, bulky chemimechanical pulp that has a low shive content and a low fine-material content - Google Patents
A light drainability, bulky chemimechanical pulp that has a low shive content and a low fine-material contentInfo
- Publication number
- CA2192570A1 CA2192570A1 CA002192570A CA2192570A CA2192570A1 CA 2192570 A1 CA2192570 A1 CA 2192570A1 CA 002192570 A CA002192570 A CA 002192570A CA 2192570 A CA2192570 A CA 2192570A CA 2192570 A1 CA2192570 A1 CA 2192570A1
- Authority
- CA
- Canada
- Prior art keywords
- pulp
- content
- refining
- chips
- preheating
- 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.)
- Abandoned
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
- D21B1/00—Fibrous raw materials or their mechanical treatment
- D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
- D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
- D21B1/14—Disintegrating in mills
- D21B1/16—Disintegrating in mills in the presence of chemical agents
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
- D21B1/00—Fibrous raw materials or their mechanical treatment
- D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
- D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
- D21B1/00—Fibrous raw materials or their mechanical treatment
- D21B1/02—Pretreatment of the raw materials by chemical or physical means
- D21B1/021—Pretreatment of the raw materials by chemical or physical means by chemical means
Abstract
A chemimechanical pulp for use in the manufacture of paper or paperboard products where a high drainability, bulky pulp is desired. The pulp has a long fiber content of between 60 and 75 %, a fine-material content of at most 14 %, a shive content of beneath 0.5 %, is refined to a freeness of 600 ml CSF at the lowest, and has a tensile index of at least 10 kNm/kg. A method for producing such a pulp comprising: a) impregnating chips with a lignin softening chemical; b) preheating the chips; c) refining the chips to papermaking pulp; wherein the chips are impregnated and heated over a total time period of at most 4 minutes; a) using a hot impregnating liquid having a temperature of at least 130 ~C; b) preheating the chips at a temperature above the lignin softening temperature; c) refining the pulp in one or more stages, of which the first or sole stage is carried out solely at essentially the same pressure and the same temperature as the preheating process; and refining the pulp at a total energy input which is at least 50 % and at most 90 % of the energy input required to achieve the same shive content when preheating at 135 ~C and using the same machine equipment.
Description
~ WO g5/34711 2 I q 2 5 7 ~ u A light drA;nAh;lity~ bulky rhrm; ~hAn;r.Al pulp that has a low shive content 2nd a low finc teLlal contçnt 1. InLLud~Lion The present invention relates to a long-fiber, readily dewa-tered, bulky, high yield rh~m; '-n;cAl pulp produced from lignocellulosic fiber material at a high yield (>8a%) and having a low shive content, low finc -~L~llal content and an extract content of less than 0.15%. The invçntion also relates to a method of producing the pulp.
In certain paper products it is advantageous to be able tO
achieve the highest pocc; hl r bulk (low bulk density) at a given ~Ll~nyLh while satisfying high requirements placed on the surfa-ce ~LupelLles of the products. F ,l~e of such ~Lodu~Ls aretissue ~LuduuL~, with which high liquid absorption is a prefe-rential ,uLu,ueLLy, and paperboard material or so-called liners for ~uLLuyaL~d fibeLboaLd boxes, with which a high degree of flexural rigidity is desired.
High bulk is, of course a nrr~ccAry factor in achieving high liquid absorption. High bulk also contributes positively to the rigidity or stiffness of the board and the liner pLUdU~Y. Since high requirements are also placed on the surface properties of this type of product, i.e. ~Lu,ueLLles which will impart smooth-ness and softness to tissue ,ULUduuLY and enable print to be applied easily to the surfaces of p~ bo~d and liners the shive content of the pulps used must be e~LL~ ly low. The requirement of a low shive content and a given lowest ' ~CAl ~LL~--yLh has hitherto limited the pncsl h; 1; ty of using the most ~LLL~ ly long-fiber rhrm; ' ;rAl pUlps of low finc LeLlal ~ul-t~llLs, which provide the bulkiest uLudu~L~. The methods hitherto known for the pLudu~Llon of e~LL~ -1y long-fiber chemi--hAn;mAl pulps have resulted in pulps which are too weak or in which the coarse shive content is much too high.
High yield '-n~CAl and r.hrmi ' ;r.Al pUlpS (>88%) are characterized in that the long whole fibers in the pulp (measu-red for instance as the fraction captured on a 3û mesh (Tyler W095/347ll 2 i 9 2 5 7 ~ ~ ' ! I ~ I ,~ . ",70 standard) wire when fractionatlng in a Bauer McNett-apparatUS) have a high flexural rigidity, which is also a prerequisite for manufacturing products which have a very high bulk. In order to produce pulp whose ~LL~nULII properties are sufficiently good for the pulp to be used in the manufacture of tissue, papeLboaLd or liner pLuùu~L~ for instance, it has also been n~--y~ry hitherto for ~hAnlCAl and ~h~mll ~hAniC.Al pulp to contain a very high proportion of fiber fragments and fine-material, since these materials function as a binder between the long, stiff fibers.
When fractionating in a Bauer McNett-apparatus, it has hitherto been ~nnc~red npneccAry for the fine-material content, which is normally characterized as the fraction that can pass through a 200 mesh wire (Tyler standard), to be greater than 10~, pref-erably greater than 12~, in order to be able to obtain ~LLenyL
properties that are sufficiently good for use in tissue, fiber-board or liner products. Another reason why it has hitherto been considered nPI~c~,y for mechanical or rh~ml -hAnlcAl pulps to contain more than 12% fine-material is because at least this amount is formed nevertheless when working the pulp to reduce its shive content (measured according to Somerville with a 0.15 mm mesh width) to levels that are sufficiently low (less than 0.50%, preferably less than 0.25~) to obtain the desired surface properties.
SE-B-397 851 teaches a method of producing a nh~mi ~h~n pulp in which the chips are first impregnated with an Al~li sodium sulphite solution and then ~leheat~d with steam at 135-170~C for about 10 minutes. The following r~f1 t is effected in an open refiner at a ~ , ~LUL~ slightly above lOO~C. The pulp is refined to 400 ml CSF and a very low shive content is obtained. Thus, when practicing this known method it is elected to refine at a relatively low temperature, i.e. a i , ~LUL~
which is much lower than the so-called lignin softening temper-ature. A relatively high energy input is then required in the refining process in order to obtain a low shive content, which results in a high percentage of fine-material in the pulp. The low shive content is only obtained at a relatively low fL~e..ess level. The long preheating time easily leads to a pulp of low ~ WO95/34711 2 1 9 2 ~ 7 0 ~ 70 brightness, particularly at the longest of these preheating times.
W0-Al-91/12367 describes an abs~ent rhrmi ~=nlr~l pulp that is manufactured from lignrrrllulosic material at an extremely low energy input, at a wood yield above 88%, a long fiber con-tent above 70%, preferably above 75%, a fine-material content below 10% and a shive content below 3%. The pulp is produced by preheating and impregnating the chips at high t~..~e~Lul~, high pressure and over a short period of time in one and the same vessel, prior to defibering the wood. When producing rhrm; ~-nical pulp with the method according to W0-Al-91/12367 at a long fiber content >70% and in which the energy input is maintained at an ~ ~L -ly low level in the refining process, there is often obtained a pulp whose shive content is too high and its strength too low (<10 kNm/kg) for the pulp to be used brnpf;ri-ally in paper products that are required to have high ~h~n~r~l strength.
By "energy input" is meant in the following the input of elec-trical energy when refining the fiber material (unless stated differently, the term energy input refers to the total energy input in the single refining stage or in all refining stages).
The term "refinement or refining" refers both to the coarse separation of the fibers (defibration) and to working of the fibers (rrf~n~ ~ in its true meaning). ~y "yield" is meant the pulp yield calculated on the fibrous starting material, such as barked wood for instance.
2. Descriptlon of the invention It has now surprisingly been found pocsihl~ to produce a bulky (density suitably lower than 400 kg/m , preferably lower than 325 kg/m3, and more preferably lower than 275 kg/m3) chrmi nical pulp at a yield greater than 88% and an extract content of less than 0.15%, wherein the inventive pulp presents good strength p~.~eL~les (tensile index above 10 kNm/kg, preferably above 15 kNm/kg, and particularly above 20 kNm/kg) and a very low shive content (less than 0.5%, preferably less than 0.25%
and more preferably less than 0.10%) at a low fine-material con-W095/~711 2 I q2570 ~4 ~ C~70 tent (at most 14% according to RMN <200 mesh (Tyler Standard),preferably at most lO~), a high long-fiber content (between 60 and 75~ according to BMN >30 mesh, preferably between 62 and 72%
and more preferably between 63 and 70~) and a high freeness (at least 600 ml CSF, preferably at least 650 ml CSF, and more preferably at least 700 ml CSF and particularly at least 720 ml CSF). It has also been found that this pulp can be used to adVUnL~ ln tissue, payeLbuaLd or liners and produces products of desired high bulk or stiffness of sufficient ~LLe1IYLII~ while PnAhl;ng the demand for good surface properties to be satlsfied at the same time.
In the following, the rhPm; - '-n;cal pulps produced in accor-dance with the invention will be referred to as "HT-CTMP" (High T~ ~LatuLe ChemiThermo~PrhAn;rAl Pulp). Standard rhPm; chAn;-cal pulps are referred to as standard CTMP.
The fiber starting material from which the rhPm; -hAn;rAl pulp is produced in accordance with the invention may comprise any l;nngr~llulosic material, for instance grass (such as S-chAn;A) or wood. Suitably softwood, such as spruce, is used.
According to the present invention there is obtained a suitable combination of valuable pLu~eLLies by a) impregnating chips produced from the lignoceliulosic material with one or more lignin softening .-hPm;rAlc, such as sulphite, ior instance, sodium sulphite, dithionite, for instance sodium dithionite, or an AlkA11nP peroxide, b) preheating the chips, c) refining the chips to produce pApPrr-k~ng pulp, d) suitably e~LLauLlng excessive coarse fiber material in a screen room and returnlng sald material for further procpcclng~
wherein the chips are impregnating and preheated over a total time period of at most 4 minutes, particularly at most 3 minutes, and preferably at most 2 minutes, and wherein ~ WO95~4711 2 i 9 2 ~ 7 ~ ~ t ~ /u a) there is used a hot lmpregnating liquid having a temperature of at least 130~C, suitably at least 150~C and preferably of essentially the same temperature as the preheating L , ~L~re, b) the impregnated chips are preheated at a temperature above the lignin softening temperature (suitably at a t , aLul~ of 150-190~C, preferably 160-175~C, when the fiber starting materi-al is softwood) and wherein c) the refining process is carried out in one or more stages of which the first, or the sole, stage is carried out at essential-ly the same ~l~S~uL~ and the same temperature as the preheatingstage and with an energy input which is at least 50% and at most 90~, particularly 60-80%, of the energy input that is required when preheating the chips at a t ~Lul~ of 135~C to achieve the same shive content in the same type of mechanical equipment.
Impregnation and preheating of the chips may conveniently be effected over a total time period of 1 minute or shorter, parti-cularly 0.5 minute or shorter. The impregnation and preheating process are suitably carried out in one and the same vessel.
When the fiber starting material is auL~ .od, the total energy input of the refining process will suitably be at least 300 kWh/ton, preferably at least 500 kWh/ton and partlcularly at least 600 kWh/ton. The total energy input of the refining pro-cess will then suitably be at most 1200 kWh/ton, preferably atmost 1100 kWh/ton and partlcularly at most 1000 kWh/ton.
The energy input ls de~ormi n~8 on each occaslon to obtain desi-red pulp pa , -L~
Both preheating and refinlng of the chips in the first stage is effected at temperatures above the lignin softening L ,~ dLuL~.
The preheating t , ~LUL~ ls sultably at least 140~C. At rele-vant working Lleyu~L.~Les in a conventional refiner when the starting material is soLL~Jod, the lignin softening t , ~L
will lie in the range of 130-140~C (ref. 1-8). Further refine-ment of the pulp is suitably carried out at lower t , aLuL~s than those used in the first stage.
. . ~
W09~/34711 2192570 ~ ' r~ s~ ~u The lignin softening temperature can be determined by mechanical speu~lusco~y in accordance with various well known methods (ref.
1-5). The lignin softening temperature can be ad~usted downwards after impregnating with different softening rhPm~r~lc (re'f. 6-8), for instance with sulphite, such as sodium sulphite, dithio-nite, such as sodium dithionite, ~lk~l 1nP peroxlde or some other lignin softening rhPmir~l, as is also the case in the r~ ' ch~n~cal processes most relevant to the invention.
However, in order for the rhPm1 ~h~n~cal pulp to provide the desired combination of properties at such high yield levels (higher than 88%), it is nPrPccary to have worked its long fibers to a suitable high degree of flP~h~l1ty without forming high p~ Lag_s of fine-material at the same time. Fiber flexi-bility is preferably achieved by causing the initlally too rigidfibers to rnll~rse~ either completely or partially, in the manufacturing process. When producing pulp in ~U~Uld~l-C~ with the present invention, this ls achieved by refining adequately softened chips in a first stage with a suitable energy input and at temperatures which exceed the so-called softening temperature of the lignin (ref. 1-8).
The degree of collapse of long, whole fibers ~a~-ul~d on a 30 mesh wire when fractionating according to Bauer McNett and produced under the aforesaid conditions have been measured in an electron microscope. The degree of roll~rsp of dried fibers has been detected as the change in the lumen of the pulp fibers according to Figure 1. The results are presented in Table 1 and show that the dried fibers in HT-CTMP have roll~rcPd to a grea-ter extent than uull~ ng fibers in ~LGIldald CTMP. This istrue despite the fact that the freeness value, which is conside-red as a reverse mea~ul t of the wnrk~hi l 1 ty of the pulp, i5 lower for the ~"dald pulp than for the pulps ~lUdUU~d in accordance with the inventlon.
~ W095~4711 2 i 9 2 5 7 ~ u Table 1 =~
HT CTMP HT CTMP Standard Ex 1 - Ex. 2 Preheat temp., ~C 170 170 135 Total energy input, kWh/t 950 6801300 Freeness, ml 660 720 554 Bauer McNett > 30 mesh, % 65.3 67.659.9 < 200 mesh, ~ 7.7 7.513.5 Shive content Somerville, ~ 0.04 0.08 0.15 Mean lumen long fiber, ,um 6.1 6.8 7.8 3. Description of the drawings and preferred '-'i Ls Comparisons are made in Figures 5-15 and in Tables 3-5 between HT-CTMP-pulps and various commercial ~hPmir- ~~n;cal CTMP-type pulps that are used at present in the manufacture of tissue and paperboard materials. The different HT-CTMP-pulps have been obtained by varying the energy inputs and the refining disk patterns in the refining process. The pulps designated Sran~i n~-vian have all been produced in plants in which the first refi-ning stage was carried out in a single-disk reflner from the machine supplier Sunds Defibrator, after preheating spruce chips at ~ a~uL~s beneath 145~C (ref. 9-11). The pups designated Ostrand were produced in a ~ ulal CTMP-plant (Figure 4), in which the first refining stage was carried out in a twin-disk refiner of the type RSB 1300 from Sunds Defibrator, after prehe-ating the chips at ; ~L~L~S beneath 140~C. The preheating time was about 3 minutes (ref. 9). The pulps designated ran~ n were all manufactured from r~n~ n spruce chips in single-disk refiners. These pulps were also preheated at temperatures below 145~C (ref. 11).
Figure 1 is a cross-section sketch of a fiber and shows the lumen of the fiber.
Figure 2 is a process chart which illustrates one example of a pulp manufacturing process in aciuLd~nu~ with the invention. In this case, the pulp is refined in a total of three stages, two ..... .. ... _ ..... .. _ . _ _ _ _ W095134711 2 1 9 2 5 7 0 ~ 5~~70 stages at high conslstencies and one stage at low consistency (Conflo).
Figure 3 is a process chart which illustrates another example of an inventive pulp manufacturing process. In this case, the pulp is refined in a total of two stages, one stage at high consis-tency and one stage at low consistency (Conflo).
Figure 4 illustrates plant ~--hinPry for the manufacture of conventional CTMP-type rhPmir--h~n1r~1 pulps, these pulps being designated ~strand in Figures 1-15. In this case, the pulp is refined in a total of two stages, one stage at high consistency and effected in two parallel-connected refiners, and one stage at low consistency (Conflo).
Figure 5 is a diagram showing the shive content as a function of freeness for a number of r.hPmi ~h~n~r~l CTMP-type pulps. The Figure shows that it is posclhl~ to produce high dr~inAh111ty (high freeness (CSF)) pulps having an e~Ll~ ly low shive con-tent ln high yields when practicing the inventive method.
Figure 6 is a diagram which shows the shive content as a func-tion of the fine-material content for a number of CTMP-type rhPm1 -h~n1cal pulps. The Figure shows that the ~Ll~ ly low Z5 shive content of the pulps ~Ludu~d in accoLd~l~ce with the invention is achieved without forming large quantities of fine-material. The fine-material content, according to 8MN <200 mesh, can be kept beneath 14~, preferably beneath 10~.
Figure 7 is a diagram showing the shive content, according to Somerville, as a function of the long fiber content. The long fiber content of the pulps ~Luduu~d in A(~ A~I ~ with the invention can be kept high despite the e~LL ly low shive cunL~,.ts of the pulps, which is a prerequisite for manufacturing pulp having the desired high bulk levels.
Figure 8 shows the tensile index as a function of the fine-material content. A sufficiently high ~c~l ~LL~n~LII (ten-sile index >10 kNm/kg, preferably >15 kNm/kg) can be achieved ... ~ . . .. _ ,_.... ._. . ...... _.. _... _ . _. _... . .. . _ ~ W095/34711 21 92~70 g~ J~ 70 without large quantlties of fine-materlal in pulps produced in a~uld~nce with the invention. This shows that the long whole fibers in the inventive pulp have been given sufficiently high flPYih11ity. The per~enLage of finc L~llal according to Bauer McNett can be kept beneath 14%, preferably beneath 10%, while, at the same time, achieving the same ~Ll~ h level as that which can be achieved with present day techniques for the manu-facture of CTMP-type ch~mi -h~nlr~l pulp. The puIcenL~ye of fine-màterial is significantly higher, however, when applying the conventional techniques.
Figure 9 shows the density as a function of the fine-material content. The highest bulk levels (density lower than 275 kg/m3) can not be achieved until the pulps have a low fine-material content, which is shown to advantage with the novel technique according to the invention.
Figure lO shows the Scott Bond value as a function of fine-material content. The Scott Bond value is of great 11, L~1,ce to the production of pulps that are intended for pa~elboald manu-facture. It is n~r~qs~ry to obtain sufficiently high Scott Bond values in order to obtain high binding ~lenuLhY in layered ~a~elLuald constructions. The Figure shows that when practicing the inventive technique, it is possible to achieve sufficiently good values without high per~enLagus of ~ine-material. The fine-material content, according to BMN <200 mesh, can be kept be-neath 14%, preferably beneath 10%.
Figure ll shows the shive content as a function of the density.
Very high bulk levels (density lower than 275 kg/m3) can be achieved with ~Ll~ ly low shive ~unL~llL-~ in pulps ~ udu~d in auuold~l~e with the invention (less than 0.3%, preferably less - than O.lû%, according to analyses with Somerville screens), which is n~e4~ ~ y in order to be able to use the pulps in products in which high demands are placed on the purity or surface smoothness of the product. When 1llal~ur~Lullng CTMP-type n~c~l pulps using present day ~erhnlqll~q it is not poqqihle to obtain the highest bulk levels (the lowest denslties) and _ _ _ _ . _ . = . . _ . _ . . . _ _ =
WO9S~4711 2I 92570 ~ ' r~ 70 sufficiently low levels of shive ~u~ at one and the same time.
Figure 12 illustrates freeness as a function of energy rnn tlon. When practicing the present invention it is possible to maintain a high level of freeness with low contents of fine-material even when the energy input is relatively high.
Figure 13 shows the shive content as a function of energy con-sumption. A low shive content can be achieved with a low energy input, when practicing the inventive method.
Figure 14 shows density as a functlon of energy rnnl ,~ion. A
low density can be achieved with a low energy input when prac-ticing the inventive method.
Figure 15 illustrates tensile index as a function of the energyron~ ,Lion. A high -h~n1n~ ny~l- can be achieved with a low energy input when practicing the inventive method.
The inventive pulps illustrated in Figures 5-11 have been pro-duced at different energy Cnn ,~lon or inputs. The lower shive contents shown in Figures 5-7 and in Figure 11 correspond to high energy inputs (with the same type of refining segment) at the same values of freeness, fine-material content, long fiber content and density respectively. In Figures ~-10, the higher tensile index, density and Scott Bond value respectively corre-spond to a higher energy input (with the same type of reflning segment) at the same fine-material content.
Figures 12-15 show that the pulp pL~p~l ~les can be controlled by the energy input in the various refining stages with a refining segment of given design. When producing pulp in accordance with the present invention (HT CTMP) the energy nnn ' in obtaining the desired plu~el-les are much lower than when producing con-ventional CTMP nh~ml - 'nn~r~l pulps using present day teoh-niques, when the refining segment is appropriately d~ign~ or configured. The energy comparison has nevertheless been made with the most energy-lean techni~ue for manufacturing conventio-_ _ _ _ _ 2 q 2 7 0 ~ Y~ 70 _ W095~4711 1 5 nal CTMP, where rrf1n L has been effected in a 52" twln-dlsk re~1ner operated at a speed of 1500 rpm. The energy ~u..~ ,Llon is still higher when manufacturing conventlonal or standard CTMP
in plants which use single-disk refiners. The properties of CTMP
manufactured in such plants are evident from Figures 5-15.
The ~lupeLLles of those pulps produced in accordance with the invention and intended for the manufacture of tissue are also described by data listed in Table 2. The properties of pulps (with equal shive collLel.tx) according to the invention have been ~ d in the table with ~uLL~ in3 pLu~eLLles of pulps manufactured in accordance with conventional rhrm1 '~n1r~1 technigues. This type of pulp intended for use in tissue or paperboard products for instance is often reguired to have a given highest shive content. The pulp pLudu~d in accordance with the invention (HT tissue) will contain much 'lower propor-tions of fine-material at a given shive content, and is also more bulky (has a lower density), has a higher dr~n~hll~ty (has a higher freeness) and can be produced at much lower energy inputs than corresponding CTMP-type rh~mi '-n1r~1 pulps pro-duced ln a conventlonal manner.
Table 2 (~1 , ' of the properties of pulps intended for tissue r ~ from spruce chips according to the invention (HT tissue) and cr,.l.. I CrMP-type, ' ' ~ ' pulp. ' The ,r , was made at identical shive content levels.
HT TISSUE CONVENTIONAL TISSUE ~
0,25-0,15 0,15-0,10 0,10-0~04 0,25-0,15 0~15-0,10 <0,10 '~7 2~7275 217325 225401) 3004~5 3134~5 730~~ 47 ~ 11650;4001)~12~;4~31~ -I) According to the rnost electric energy effective technigue known at present time, with refinement in double disc refmers.
~ W095~47ll 2 i 92~70 13 ~ ~70 As will be evident from the Table, when practicing conventional techni~ues it is e~Ll~ ly difficult to obtain a shive content of 0.10% or lower in the freeness range above 400 ml, which is the most relevant range for the inventive pulps.
Example 1 The pulps were ~rud~ced in the plant described with reference to Figure 2. Spruce chips were steamed a ,'- ically, ~csed in a press screw and then impregnated with 3-5% sodium sulphite at a i , ~Ul~ of 170-175'C. The chips were held in the imp-regnating liquor for about 1 minute. After impregnation, the chips were preheated in the same vessel in a steam ~L srh~re at a temperature of 170-175~C for about 1 minute prior to being refined in the first stage, which was carried out in a single disk refiner of the type RGP 242 at high consistency (about 30%) and at the same pressure and the same temperature as those applied in the preheating process. For these tests the refiner was equipped with two different types of refining disks (type 11979 or 11980 from the sl-rrl i~r Sunds Defibr~tor). After this initial refining stage, the pulp was blown to an ai - ,~Aric~ in other words non-pressurized, twin-disk refiner of the type RSB
1300, in which the pulp was refined in a second stage, which was also carried out at a high consistency (about 30%). A third refining stage was carried out at a low consistency (4-5%) in a Conflo-type low consistency refiner obtained from Sunds Defib-rator (machine suppliers). A number of pulps were yludu~ed~
these pulps being given individually specifio ~lupelLles by varying the energy inputs in the-different refining stages. The different refining se~ Lx gave different relati~nAhir~ bet-ween energy cull~ ,Llon and pulp pl~elLles (see Figures 12-15).
It was found that the freeness-value and the shive content de-creased while the denslty and tensile index value increased with increasing energy input values. Table 3 presents data for the different pulps ~rodu~d in accordance with the invention, which are ,- ,- ed in the table with pulps produced in the plant shown in Figure 4 by means of a conventional CTMP-techni~ue (STD
CTMP).
W09~34711 2 ~ 9 2 5 7 0 14 ' '~ ~ F~ 70 The reference pulps were produced from the same type of spruce chips as those used in the tests carried out in accordance with the invention. The chips were impregnated with 2-5~ sodium sulphite in an a; ~h~riC impregnating stage and then preheated to a t~ eL~LuL~ of 135~C, i.e. to the lignin softening tempera-ture. The pulp was refined in a first pressurized stage at a high pulp consistency (30~) in an RSB 1300 type twin-disk refi-ner at the same temperature as the preheating t , ~UL~. The pulp was then refined in a second stage in a Conflo-type low consistency refiner under the same conditions as those applied when producing Hl CTMP.
Example 2 Pulps were also produced in ~r~r~ncP with the invention under the same conditions as those repor~ed in Example l, but with the exception that the second high-consistency refining stage was excluded. Instead, the pulp was blown from the first refining stage directly to a vessel in which the pulp was thinned for refinement in a Conflo-type low-consistency refiner. The pro-perties of the pulps yLuduc~d are set forth in Table 4. Theresults show that inventive pulps can also be produced in accor-dance with this method.
Example 3 Pulps were pLudu~d in accordance with the invention under the same conditions as those L~uL~ed in Example l with the excep-tion that the third low-consistency refining stage was omitted.
The properties of the pulps ~L~duc~d are set~forth in Table 5.
The results show that pulps according to the invention can also be produced by this method.
W095/34711 2 1 92 5 7 i~ u ~ u~ ~~ ~ Er~ 0 0~ ~ o 0 N 0, ~ 0 ~ ' 0 ,~
y ~ } 8 o o ~ ~' 0 0 0 ,~ N c~ O
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l. Atack, D., Svensk Papperstidning 75 (3):89 (1972) 2. Hoglund, H. and Sohlin, U.;
"The effect of physical properties of the wood in chip refining n ~
Pro~e~1ngs 1975, Intrnational ~rh~n;ral Pulping Conference, San Francisco, San Francisco, June 16-20, p 77-85.
3. Salmén, L.:
"Viqr~lActic yLoyeLLles of in situ lignin under water saturated conditions", Journal of Materials Science l9 (1984), p 3090-3096.
In certain paper products it is advantageous to be able tO
achieve the highest pocc; hl r bulk (low bulk density) at a given ~Ll~nyLh while satisfying high requirements placed on the surfa-ce ~LupelLles of the products. F ,l~e of such ~Lodu~Ls aretissue ~LuduuL~, with which high liquid absorption is a prefe-rential ,uLu,ueLLy, and paperboard material or so-called liners for ~uLLuyaL~d fibeLboaLd boxes, with which a high degree of flexural rigidity is desired.
High bulk is, of course a nrr~ccAry factor in achieving high liquid absorption. High bulk also contributes positively to the rigidity or stiffness of the board and the liner pLUdU~Y. Since high requirements are also placed on the surface properties of this type of product, i.e. ~Lu,ueLLles which will impart smooth-ness and softness to tissue ,ULUduuLY and enable print to be applied easily to the surfaces of p~ bo~d and liners the shive content of the pulps used must be e~LL~ ly low. The requirement of a low shive content and a given lowest ' ~CAl ~LL~--yLh has hitherto limited the pncsl h; 1; ty of using the most ~LLL~ ly long-fiber rhrm; ' ;rAl pUlps of low finc LeLlal ~ul-t~llLs, which provide the bulkiest uLudu~L~. The methods hitherto known for the pLudu~Llon of e~LL~ -1y long-fiber chemi--hAn;mAl pulps have resulted in pulps which are too weak or in which the coarse shive content is much too high.
High yield '-n~CAl and r.hrmi ' ;r.Al pUlpS (>88%) are characterized in that the long whole fibers in the pulp (measu-red for instance as the fraction captured on a 3û mesh (Tyler W095/347ll 2 i 9 2 5 7 ~ ~ ' ! I ~ I ,~ . ",70 standard) wire when fractionatlng in a Bauer McNett-apparatUS) have a high flexural rigidity, which is also a prerequisite for manufacturing products which have a very high bulk. In order to produce pulp whose ~LL~nULII properties are sufficiently good for the pulp to be used in the manufacture of tissue, papeLboaLd or liner pLuùu~L~ for instance, it has also been n~--y~ry hitherto for ~hAnlCAl and ~h~mll ~hAniC.Al pulp to contain a very high proportion of fiber fragments and fine-material, since these materials function as a binder between the long, stiff fibers.
When fractionating in a Bauer McNett-apparatus, it has hitherto been ~nnc~red npneccAry for the fine-material content, which is normally characterized as the fraction that can pass through a 200 mesh wire (Tyler standard), to be greater than 10~, pref-erably greater than 12~, in order to be able to obtain ~LLenyL
properties that are sufficiently good for use in tissue, fiber-board or liner products. Another reason why it has hitherto been considered nPI~c~,y for mechanical or rh~ml -hAnlcAl pulps to contain more than 12% fine-material is because at least this amount is formed nevertheless when working the pulp to reduce its shive content (measured according to Somerville with a 0.15 mm mesh width) to levels that are sufficiently low (less than 0.50%, preferably less than 0.25~) to obtain the desired surface properties.
SE-B-397 851 teaches a method of producing a nh~mi ~h~n pulp in which the chips are first impregnated with an Al~li sodium sulphite solution and then ~leheat~d with steam at 135-170~C for about 10 minutes. The following r~f1 t is effected in an open refiner at a ~ , ~LUL~ slightly above lOO~C. The pulp is refined to 400 ml CSF and a very low shive content is obtained. Thus, when practicing this known method it is elected to refine at a relatively low temperature, i.e. a i , ~LUL~
which is much lower than the so-called lignin softening temper-ature. A relatively high energy input is then required in the refining process in order to obtain a low shive content, which results in a high percentage of fine-material in the pulp. The low shive content is only obtained at a relatively low fL~e..ess level. The long preheating time easily leads to a pulp of low ~ WO95/34711 2 1 9 2 ~ 7 0 ~ 70 brightness, particularly at the longest of these preheating times.
W0-Al-91/12367 describes an abs~ent rhrmi ~=nlr~l pulp that is manufactured from lignrrrllulosic material at an extremely low energy input, at a wood yield above 88%, a long fiber con-tent above 70%, preferably above 75%, a fine-material content below 10% and a shive content below 3%. The pulp is produced by preheating and impregnating the chips at high t~..~e~Lul~, high pressure and over a short period of time in one and the same vessel, prior to defibering the wood. When producing rhrm; ~-nical pulp with the method according to W0-Al-91/12367 at a long fiber content >70% and in which the energy input is maintained at an ~ ~L -ly low level in the refining process, there is often obtained a pulp whose shive content is too high and its strength too low (<10 kNm/kg) for the pulp to be used brnpf;ri-ally in paper products that are required to have high ~h~n~r~l strength.
By "energy input" is meant in the following the input of elec-trical energy when refining the fiber material (unless stated differently, the term energy input refers to the total energy input in the single refining stage or in all refining stages).
The term "refinement or refining" refers both to the coarse separation of the fibers (defibration) and to working of the fibers (rrf~n~ ~ in its true meaning). ~y "yield" is meant the pulp yield calculated on the fibrous starting material, such as barked wood for instance.
2. Descriptlon of the invention It has now surprisingly been found pocsihl~ to produce a bulky (density suitably lower than 400 kg/m , preferably lower than 325 kg/m3, and more preferably lower than 275 kg/m3) chrmi nical pulp at a yield greater than 88% and an extract content of less than 0.15%, wherein the inventive pulp presents good strength p~.~eL~les (tensile index above 10 kNm/kg, preferably above 15 kNm/kg, and particularly above 20 kNm/kg) and a very low shive content (less than 0.5%, preferably less than 0.25%
and more preferably less than 0.10%) at a low fine-material con-W095/~711 2 I q2570 ~4 ~ C~70 tent (at most 14% according to RMN <200 mesh (Tyler Standard),preferably at most lO~), a high long-fiber content (between 60 and 75~ according to BMN >30 mesh, preferably between 62 and 72%
and more preferably between 63 and 70~) and a high freeness (at least 600 ml CSF, preferably at least 650 ml CSF, and more preferably at least 700 ml CSF and particularly at least 720 ml CSF). It has also been found that this pulp can be used to adVUnL~ ln tissue, payeLbuaLd or liners and produces products of desired high bulk or stiffness of sufficient ~LLe1IYLII~ while PnAhl;ng the demand for good surface properties to be satlsfied at the same time.
In the following, the rhPm; - '-n;cal pulps produced in accor-dance with the invention will be referred to as "HT-CTMP" (High T~ ~LatuLe ChemiThermo~PrhAn;rAl Pulp). Standard rhPm; chAn;-cal pulps are referred to as standard CTMP.
The fiber starting material from which the rhPm; -hAn;rAl pulp is produced in accordance with the invention may comprise any l;nngr~llulosic material, for instance grass (such as S-chAn;A) or wood. Suitably softwood, such as spruce, is used.
According to the present invention there is obtained a suitable combination of valuable pLu~eLLies by a) impregnating chips produced from the lignoceliulosic material with one or more lignin softening .-hPm;rAlc, such as sulphite, ior instance, sodium sulphite, dithionite, for instance sodium dithionite, or an AlkA11nP peroxide, b) preheating the chips, c) refining the chips to produce pApPrr-k~ng pulp, d) suitably e~LLauLlng excessive coarse fiber material in a screen room and returnlng sald material for further procpcclng~
wherein the chips are impregnating and preheated over a total time period of at most 4 minutes, particularly at most 3 minutes, and preferably at most 2 minutes, and wherein ~ WO95~4711 2 i 9 2 ~ 7 ~ ~ t ~ /u a) there is used a hot lmpregnating liquid having a temperature of at least 130~C, suitably at least 150~C and preferably of essentially the same temperature as the preheating L , ~L~re, b) the impregnated chips are preheated at a temperature above the lignin softening temperature (suitably at a t , aLul~ of 150-190~C, preferably 160-175~C, when the fiber starting materi-al is softwood) and wherein c) the refining process is carried out in one or more stages of which the first, or the sole, stage is carried out at essential-ly the same ~l~S~uL~ and the same temperature as the preheatingstage and with an energy input which is at least 50% and at most 90~, particularly 60-80%, of the energy input that is required when preheating the chips at a t ~Lul~ of 135~C to achieve the same shive content in the same type of mechanical equipment.
Impregnation and preheating of the chips may conveniently be effected over a total time period of 1 minute or shorter, parti-cularly 0.5 minute or shorter. The impregnation and preheating process are suitably carried out in one and the same vessel.
When the fiber starting material is auL~ .od, the total energy input of the refining process will suitably be at least 300 kWh/ton, preferably at least 500 kWh/ton and partlcularly at least 600 kWh/ton. The total energy input of the refining pro-cess will then suitably be at most 1200 kWh/ton, preferably atmost 1100 kWh/ton and partlcularly at most 1000 kWh/ton.
The energy input ls de~ormi n~8 on each occaslon to obtain desi-red pulp pa , -L~
Both preheating and refinlng of the chips in the first stage is effected at temperatures above the lignin softening L ,~ dLuL~.
The preheating t , ~LUL~ ls sultably at least 140~C. At rele-vant working Lleyu~L.~Les in a conventional refiner when the starting material is soLL~Jod, the lignin softening t , ~L
will lie in the range of 130-140~C (ref. 1-8). Further refine-ment of the pulp is suitably carried out at lower t , aLuL~s than those used in the first stage.
. . ~
W09~/34711 2192570 ~ ' r~ s~ ~u The lignin softening temperature can be determined by mechanical speu~lusco~y in accordance with various well known methods (ref.
1-5). The lignin softening temperature can be ad~usted downwards after impregnating with different softening rhPm~r~lc (re'f. 6-8), for instance with sulphite, such as sodium sulphite, dithio-nite, such as sodium dithionite, ~lk~l 1nP peroxlde or some other lignin softening rhPmir~l, as is also the case in the r~ ' ch~n~cal processes most relevant to the invention.
However, in order for the rhPm1 ~h~n~cal pulp to provide the desired combination of properties at such high yield levels (higher than 88%), it is nPrPccary to have worked its long fibers to a suitable high degree of flP~h~l1ty without forming high p~ Lag_s of fine-material at the same time. Fiber flexi-bility is preferably achieved by causing the initlally too rigidfibers to rnll~rse~ either completely or partially, in the manufacturing process. When producing pulp in ~U~Uld~l-C~ with the present invention, this ls achieved by refining adequately softened chips in a first stage with a suitable energy input and at temperatures which exceed the so-called softening temperature of the lignin (ref. 1-8).
The degree of collapse of long, whole fibers ~a~-ul~d on a 30 mesh wire when fractionating according to Bauer McNett and produced under the aforesaid conditions have been measured in an electron microscope. The degree of roll~rsp of dried fibers has been detected as the change in the lumen of the pulp fibers according to Figure 1. The results are presented in Table 1 and show that the dried fibers in HT-CTMP have roll~rcPd to a grea-ter extent than uull~ ng fibers in ~LGIldald CTMP. This istrue despite the fact that the freeness value, which is conside-red as a reverse mea~ul t of the wnrk~hi l 1 ty of the pulp, i5 lower for the ~"dald pulp than for the pulps ~lUdUU~d in accordance with the inventlon.
~ W095~4711 2 i 9 2 5 7 ~ u Table 1 =~
HT CTMP HT CTMP Standard Ex 1 - Ex. 2 Preheat temp., ~C 170 170 135 Total energy input, kWh/t 950 6801300 Freeness, ml 660 720 554 Bauer McNett > 30 mesh, % 65.3 67.659.9 < 200 mesh, ~ 7.7 7.513.5 Shive content Somerville, ~ 0.04 0.08 0.15 Mean lumen long fiber, ,um 6.1 6.8 7.8 3. Description of the drawings and preferred '-'i Ls Comparisons are made in Figures 5-15 and in Tables 3-5 between HT-CTMP-pulps and various commercial ~hPmir- ~~n;cal CTMP-type pulps that are used at present in the manufacture of tissue and paperboard materials. The different HT-CTMP-pulps have been obtained by varying the energy inputs and the refining disk patterns in the refining process. The pulps designated Sran~i n~-vian have all been produced in plants in which the first refi-ning stage was carried out in a single-disk reflner from the machine supplier Sunds Defibrator, after preheating spruce chips at ~ a~uL~s beneath 145~C (ref. 9-11). The pups designated Ostrand were produced in a ~ ulal CTMP-plant (Figure 4), in which the first refining stage was carried out in a twin-disk refiner of the type RSB 1300 from Sunds Defibrator, after prehe-ating the chips at ; ~L~L~S beneath 140~C. The preheating time was about 3 minutes (ref. 9). The pulps designated ran~ n were all manufactured from r~n~ n spruce chips in single-disk refiners. These pulps were also preheated at temperatures below 145~C (ref. 11).
Figure 1 is a cross-section sketch of a fiber and shows the lumen of the fiber.
Figure 2 is a process chart which illustrates one example of a pulp manufacturing process in aciuLd~nu~ with the invention. In this case, the pulp is refined in a total of three stages, two ..... .. ... _ ..... .. _ . _ _ _ _ W095134711 2 1 9 2 5 7 0 ~ 5~~70 stages at high conslstencies and one stage at low consistency (Conflo).
Figure 3 is a process chart which illustrates another example of an inventive pulp manufacturing process. In this case, the pulp is refined in a total of two stages, one stage at high consis-tency and one stage at low consistency (Conflo).
Figure 4 illustrates plant ~--hinPry for the manufacture of conventional CTMP-type rhPmir--h~n1r~1 pulps, these pulps being designated ~strand in Figures 1-15. In this case, the pulp is refined in a total of two stages, one stage at high consistency and effected in two parallel-connected refiners, and one stage at low consistency (Conflo).
Figure 5 is a diagram showing the shive content as a function of freeness for a number of r.hPmi ~h~n~r~l CTMP-type pulps. The Figure shows that it is posclhl~ to produce high dr~inAh111ty (high freeness (CSF)) pulps having an e~Ll~ ly low shive con-tent ln high yields when practicing the inventive method.
Figure 6 is a diagram which shows the shive content as a func-tion of the fine-material content for a number of CTMP-type rhPm1 -h~n1cal pulps. The Figure shows that the ~Ll~ ly low Z5 shive content of the pulps ~Ludu~d in accoLd~l~ce with the invention is achieved without forming large quantities of fine-material. The fine-material content, according to 8MN <200 mesh, can be kept beneath 14~, preferably beneath 10~.
Figure 7 is a diagram showing the shive content, according to Somerville, as a function of the long fiber content. The long fiber content of the pulps ~Luduu~d in A(~ A~I ~ with the invention can be kept high despite the e~LL ly low shive cunL~,.ts of the pulps, which is a prerequisite for manufacturing pulp having the desired high bulk levels.
Figure 8 shows the tensile index as a function of the fine-material content. A sufficiently high ~c~l ~LL~n~LII (ten-sile index >10 kNm/kg, preferably >15 kNm/kg) can be achieved ... ~ . . .. _ ,_.... ._. . ...... _.. _... _ . _. _... . .. . _ ~ W095/34711 21 92~70 g~ J~ 70 without large quantlties of fine-materlal in pulps produced in a~uld~nce with the invention. This shows that the long whole fibers in the inventive pulp have been given sufficiently high flPYih11ity. The per~enLage of finc L~llal according to Bauer McNett can be kept beneath 14%, preferably beneath 10%, while, at the same time, achieving the same ~Ll~ h level as that which can be achieved with present day techniques for the manu-facture of CTMP-type ch~mi -h~nlr~l pulp. The puIcenL~ye of fine-màterial is significantly higher, however, when applying the conventional techniques.
Figure 9 shows the density as a function of the fine-material content. The highest bulk levels (density lower than 275 kg/m3) can not be achieved until the pulps have a low fine-material content, which is shown to advantage with the novel technique according to the invention.
Figure lO shows the Scott Bond value as a function of fine-material content. The Scott Bond value is of great 11, L~1,ce to the production of pulps that are intended for pa~elboald manu-facture. It is n~r~qs~ry to obtain sufficiently high Scott Bond values in order to obtain high binding ~lenuLhY in layered ~a~elLuald constructions. The Figure shows that when practicing the inventive technique, it is possible to achieve sufficiently good values without high per~enLagus of ~ine-material. The fine-material content, according to BMN <200 mesh, can be kept be-neath 14%, preferably beneath 10%.
Figure ll shows the shive content as a function of the density.
Very high bulk levels (density lower than 275 kg/m3) can be achieved with ~Ll~ ly low shive ~unL~llL-~ in pulps ~ udu~d in auuold~l~e with the invention (less than 0.3%, preferably less - than O.lû%, according to analyses with Somerville screens), which is n~e4~ ~ y in order to be able to use the pulps in products in which high demands are placed on the purity or surface smoothness of the product. When 1llal~ur~Lullng CTMP-type n~c~l pulps using present day ~erhnlqll~q it is not poqqihle to obtain the highest bulk levels (the lowest denslties) and _ _ _ _ . _ . = . . _ . _ . . . _ _ =
WO9S~4711 2I 92570 ~ ' r~ 70 sufficiently low levels of shive ~u~ at one and the same time.
Figure 12 illustrates freeness as a function of energy rnn tlon. When practicing the present invention it is possible to maintain a high level of freeness with low contents of fine-material even when the energy input is relatively high.
Figure 13 shows the shive content as a function of energy con-sumption. A low shive content can be achieved with a low energy input, when practicing the inventive method.
Figure 14 shows density as a functlon of energy rnnl ,~ion. A
low density can be achieved with a low energy input when prac-ticing the inventive method.
Figure 15 illustrates tensile index as a function of the energyron~ ,Lion. A high -h~n1n~ ny~l- can be achieved with a low energy input when practicing the inventive method.
The inventive pulps illustrated in Figures 5-11 have been pro-duced at different energy Cnn ,~lon or inputs. The lower shive contents shown in Figures 5-7 and in Figure 11 correspond to high energy inputs (with the same type of refining segment) at the same values of freeness, fine-material content, long fiber content and density respectively. In Figures ~-10, the higher tensile index, density and Scott Bond value respectively corre-spond to a higher energy input (with the same type of reflning segment) at the same fine-material content.
Figures 12-15 show that the pulp pL~p~l ~les can be controlled by the energy input in the various refining stages with a refining segment of given design. When producing pulp in accordance with the present invention (HT CTMP) the energy nnn ' in obtaining the desired plu~el-les are much lower than when producing con-ventional CTMP nh~ml - 'nn~r~l pulps using present day teoh-niques, when the refining segment is appropriately d~ign~ or configured. The energy comparison has nevertheless been made with the most energy-lean techni~ue for manufacturing conventio-_ _ _ _ _ 2 q 2 7 0 ~ Y~ 70 _ W095~4711 1 5 nal CTMP, where rrf1n L has been effected in a 52" twln-dlsk re~1ner operated at a speed of 1500 rpm. The energy ~u..~ ,Llon is still higher when manufacturing conventlonal or standard CTMP
in plants which use single-disk refiners. The properties of CTMP
manufactured in such plants are evident from Figures 5-15.
The ~lupeLLles of those pulps produced in accordance with the invention and intended for the manufacture of tissue are also described by data listed in Table 2. The properties of pulps (with equal shive collLel.tx) according to the invention have been ~ d in the table with ~uLL~ in3 pLu~eLLles of pulps manufactured in accordance with conventional rhrm1 '~n1r~1 technigues. This type of pulp intended for use in tissue or paperboard products for instance is often reguired to have a given highest shive content. The pulp pLudu~d in accordance with the invention (HT tissue) will contain much 'lower propor-tions of fine-material at a given shive content, and is also more bulky (has a lower density), has a higher dr~n~hll~ty (has a higher freeness) and can be produced at much lower energy inputs than corresponding CTMP-type rh~mi '-n1r~1 pulps pro-duced ln a conventlonal manner.
Table 2 (~1 , ' of the properties of pulps intended for tissue r ~ from spruce chips according to the invention (HT tissue) and cr,.l.. I CrMP-type, ' ' ~ ' pulp. ' The ,r , was made at identical shive content levels.
HT TISSUE CONVENTIONAL TISSUE ~
0,25-0,15 0,15-0,10 0,10-0~04 0,25-0,15 0~15-0,10 <0,10 '~7 2~7275 217325 225401) 3004~5 3134~5 730~~ 47 ~ 11650;4001)~12~;4~31~ -I) According to the rnost electric energy effective technigue known at present time, with refinement in double disc refmers.
~ W095~47ll 2 i 92~70 13 ~ ~70 As will be evident from the Table, when practicing conventional techni~ues it is e~Ll~ ly difficult to obtain a shive content of 0.10% or lower in the freeness range above 400 ml, which is the most relevant range for the inventive pulps.
Example 1 The pulps were ~rud~ced in the plant described with reference to Figure 2. Spruce chips were steamed a ,'- ically, ~csed in a press screw and then impregnated with 3-5% sodium sulphite at a i , ~Ul~ of 170-175'C. The chips were held in the imp-regnating liquor for about 1 minute. After impregnation, the chips were preheated in the same vessel in a steam ~L srh~re at a temperature of 170-175~C for about 1 minute prior to being refined in the first stage, which was carried out in a single disk refiner of the type RGP 242 at high consistency (about 30%) and at the same pressure and the same temperature as those applied in the preheating process. For these tests the refiner was equipped with two different types of refining disks (type 11979 or 11980 from the sl-rrl i~r Sunds Defibr~tor). After this initial refining stage, the pulp was blown to an ai - ,~Aric~ in other words non-pressurized, twin-disk refiner of the type RSB
1300, in which the pulp was refined in a second stage, which was also carried out at a high consistency (about 30%). A third refining stage was carried out at a low consistency (4-5%) in a Conflo-type low consistency refiner obtained from Sunds Defib-rator (machine suppliers). A number of pulps were yludu~ed~
these pulps being given individually specifio ~lupelLles by varying the energy inputs in the-different refining stages. The different refining se~ Lx gave different relati~nAhir~ bet-ween energy cull~ ,Llon and pulp pl~elLles (see Figures 12-15).
It was found that the freeness-value and the shive content de-creased while the denslty and tensile index value increased with increasing energy input values. Table 3 presents data for the different pulps ~rodu~d in accordance with the invention, which are ,- ,- ed in the table with pulps produced in the plant shown in Figure 4 by means of a conventional CTMP-techni~ue (STD
CTMP).
W09~34711 2 ~ 9 2 5 7 0 14 ' '~ ~ F~ 70 The reference pulps were produced from the same type of spruce chips as those used in the tests carried out in accordance with the invention. The chips were impregnated with 2-5~ sodium sulphite in an a; ~h~riC impregnating stage and then preheated to a t~ eL~LuL~ of 135~C, i.e. to the lignin softening tempera-ture. The pulp was refined in a first pressurized stage at a high pulp consistency (30~) in an RSB 1300 type twin-disk refi-ner at the same temperature as the preheating t , ~UL~. The pulp was then refined in a second stage in a Conflo-type low consistency refiner under the same conditions as those applied when producing Hl CTMP.
Example 2 Pulps were also produced in ~r~r~ncP with the invention under the same conditions as those repor~ed in Example l, but with the exception that the second high-consistency refining stage was excluded. Instead, the pulp was blown from the first refining stage directly to a vessel in which the pulp was thinned for refinement in a Conflo-type low-consistency refiner. The pro-perties of the pulps yLuduc~d are set forth in Table 4. Theresults show that inventive pulps can also be produced in accor-dance with this method.
Example 3 Pulps were pLudu~d in accordance with the invention under the same conditions as those L~uL~ed in Example l with the excep-tion that the third low-consistency refining stage was omitted.
The properties of the pulps ~L~duc~d are set~forth in Table 5.
The results show that pulps according to the invention can also be produced by this method.
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O _~ r~ E 0 ~D ~ ~~ N ~r _ O. q0 0. CD 00 ID _ cc cc cc cc $ E a~ ae ae a~ E ~ ~ E a~ EE ae ae - i 3 3 3 3 ~
y y ~ ~c ~ ~ z t .
N -- N, V
, _, ~, ' ' ~ , L~ g a ~ E
8 ~ O ~ I ~ ~ I c _ _ ~ WO95~i4711 2 1 925 70 ., ~ ~
LiL~LaLuL~
The lignin softening ~ , aLuLe:
l. Atack, D., Svensk Papperstidning 75 (3):89 (1972) 2. Hoglund, H. and Sohlin, U.;
"The effect of physical properties of the wood in chip refining n ~
Pro~e~1ngs 1975, Intrnational ~rh~n;ral Pulping Conference, San Francisco, San Francisco, June 16-20, p 77-85.
3. Salmén, L.:
"Viqr~lActic yLoyeLLles of in situ lignin under water saturated conditions", Journal of Materials Science l9 (1984), p 3090-3096.
4. Salmén, N.L. and Fellers, C.:
"The fllr~; L~ls of energy ~O~ Lion during v;conelAqtic and plastic deformation of wood", Journal Pulp Paper Science TR93-99 (1982).
"The fllr~; L~ls of energy ~O~ Lion during v;conelAqtic and plastic deformation of wood", Journal Pulp Paper Science TR93-99 (1982).
5. Becker, H., Hoglund, H. and Tistad, G.:
"Fl~u~l~y and t , aLuLe in chip reflning"
Paperi ~a Puu 59 (1977), No. 3, p 123.
Lignln softening L , ~LUL~ after rhem;cAl softenlng:
"Fl~u~l~y and t , aLuLe in chip reflning"
Paperi ~a Puu 59 (1977), No. 3, p 123.
Lignln softening L , ~LUL~ after rhem;cAl softenlng:
6. Atack, D. and Heitner, C.:
"Dynamic - '-nirAl yL~yeLLles of sulfonated eastern black spruce"
Pror~e~;ngq 1979, International Mechanical Pulping Conference, Terhnf r.~l Sectlon CPPA, June 1979, ~ p. 1 - 12.
"Dynamic - '-nirAl yL~yeLLles of sulfonated eastern black spruce"
Pror~e~;ngq 1979, International Mechanical Pulping Conference, Terhnf r.~l Sectlon CPPA, June 1979, ~ p. 1 - 12.
7. Heitner, C. and Atach, D.:
"Dynamlc ' frAl pL~yeLLles of sulphite treated aspen"
Paperi ja Puu, No 2 (1984), p 84-89.
, _ . _ _, .. ., . , , . , , _ _ WO95~4711 2~ 92570 18 ~ lu 8. Corson, S.R. and Fontebasso, J.:
"Visco-elastic energy absorption of sulfonated radiata pine"
Appita Vol. 43, No. 4, p 300-304.
Reference mill and system descriptions 9. CTMP, Brochure from Sunds Defibrator (334-167 E
01.83) 10. First CTMP-mill in Norway, Norsk ~kns1n~llqtri~
No. 9, 1984, p 40-44.
"Dynamlc ' frAl pL~yeLLles of sulphite treated aspen"
Paperi ja Puu, No 2 (1984), p 84-89.
, _ . _ _, .. ., . , , . , , _ _ WO95~4711 2~ 92570 18 ~ lu 8. Corson, S.R. and Fontebasso, J.:
"Visco-elastic energy absorption of sulfonated radiata pine"
Appita Vol. 43, No. 4, p 300-304.
Reference mill and system descriptions 9. CTMP, Brochure from Sunds Defibrator (334-167 E
01.83) 10. First CTMP-mill in Norway, Norsk ~kns1n~llqtri~
No. 9, 1984, p 40-44.
11. Sharman, P.M.: Pulp & Paper, Vol 63, No. 5, May 1989, p S2-S32.
Test methods Shive content Somerville TAPPI UM 242 Freeness SCAN M4:65 Bauer McNett SCAN M6:69 Manufacture of laboratory sheets SCAN M5:76 Tensile index SCAN M8:76 Density (bulk) SCAN M8:76 Scott Bond TAPPI UM 403
Test methods Shive content Somerville TAPPI UM 242 Freeness SCAN M4:65 Bauer McNett SCAN M6:69 Manufacture of laboratory sheets SCAN M5:76 Tensile index SCAN M8:76 Density (bulk) SCAN M8:76 Scott Bond TAPPI UM 403
Claims (14)
1. A high drainability chemimechanical pulp for use in the manufacture of paper or paperboard products where a high bulk is desired, wherein the pulp is produced from lignocellulosic material at a yield above 88%, and has an extract content of beneath 0.15% calculated as dichloromethaneresin extractable, a high long fiber content, a low fine-material content and a low shive content, characterized in the pulp having been produced by refining impregnated and preheated chips in one stage or in several stages in series, wherein the first or sole stage, respectively, is effected at a temperature of 150-190°C and above the lignin softening temperature, that when fractionating according to Bauer McNett the long fiber content is between 60 and 75% (fibers retained on a 30 mesh wire cloth); in that when fractionating according to Bauer McNett the fine-material content is at most 14% (the percentage of fibers that pass through a 200 mesh wire cloth); in that the pulp is refined to a freeness of 600 ml CSF at the lowest; in that the shive content is lower than 0.5%, preferably lower than 0.25%; in that the pulp density is 200-400 kg/m3 and in that the tensile index of the pulp is at least 10 kNm/kg.
2. A pulp according to Claim 1, characterized in that the long fiber content is between 62 and 72%, preferably between 63 and 70%.
3. A pulp according to Claim 1 or 2, characterized in that the fine-material content is at most 11%, preferably at most 9%.
4. A pulp according to any one of the preceding claims, characterized in that the shive content is at most 0.15%, preferably at most 0.10%.
5. A pulp according to Claim 1, characterized in that the long fiber content is at least 65%; in that the fine-material content is at most 10%; in that the pulp is refined to a freeness of 650 ml CSF at the lowest; and in that the shive content is at most 0.10%.
6. A method for producing chemithermomechanical pulp (CTMP) according to Claim 1, by a) impregnating chips of lignocellulosic material with a lignin softening chemical, such as sulphite, for instance sodium sulphite, dithionite, for instance sodium dithionite, or alkaline peroxide;
b) preheating the chips;
c) refining the chips to paper pulp;
characterized by effecting the chips impregnating and preheating process over a total time period of at most 4 minutes, preferably at most 2 minutes, and more preferably at most 1 minute;
a) using a hot impregnating liquid having a temperature of at least 130°C, suitab1y at least 150°C and preferably having essentially the same temperature level as the preheating temperature level;
b) preheating the chips at a temperature of 150-190°C and above the lignin softening temperature;
c) refining the chips in one stage or in several stages in series, wherein the first or sole stage, respectively, is effected at essentially the same pressure and the same temperature as the preheating process; and effecting the refining process at a total energy input which is at least 50% and at most 90% of the energy input that is required to achieve the same shive content when preheating at 135°C and using the same machine equipment.
b) preheating the chips;
c) refining the chips to paper pulp;
characterized by effecting the chips impregnating and preheating process over a total time period of at most 4 minutes, preferably at most 2 minutes, and more preferably at most 1 minute;
a) using a hot impregnating liquid having a temperature of at least 130°C, suitab1y at least 150°C and preferably having essentially the same temperature level as the preheating temperature level;
b) preheating the chips at a temperature of 150-190°C and above the lignin softening temperature;
c) refining the chips in one stage or in several stages in series, wherein the first or sole stage, respectively, is effected at essentially the same pressure and the same temperature as the preheating process; and effecting the refining process at a total energy input which is at least 50% and at most 90% of the energy input that is required to achieve the same shive content when preheating at 135°C and using the same machine equipment.
7. A method according to Claim 6, characterized by effecting the refining process at a total energy input which is at least 60% and at most 80% of the energy input required to achieve the same shive content when preheating at 135°C and using the same machine equipment.
8. A method according to Claim 6 or Claim 7, characterized by effecting the first refining stage at a temperature of 160-175°C, wherein the fiber starting material is softwood.
9. A method according to any one of Claims 6-8, characterized by using softwood as the fiber starting material and by effecting the refining process with a total energy input of at least 300 kWh/ton, preferably at least 500 kWh/ton, and then particularly at least 600 kWh/ton.
10. A method according to Claim 9, characterized by using softwood as the fiber starting material and by effecting the refining process at a total energy input of at most 1200 kWh/ton, preferably at most 1100 kWh/ton, and then particularly at most 1000 kWh/ton.
11. A method according to any one of Claims 6-10, characterized by effecting the refining process in at least three stages in series.
12. A method according to any one of Claims 6-11, characterized by refining the pulp in the first stage at a pulp consistency which is higher than 25%, preferably about 30%.
13. A method according to any one of Claims 6-12, characterized by refining the pulp in the second refining stage at atmospheric pressure and at a pulp consistency which is higher than 25%, preferably about 30%.
14. A method according to any one of Claims 6-13, characterized by refining the pulp in the last refining stage at a pulp consistency which is lower than 8%, preferably between 4% and 6%.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE9402101A SE9402101L (en) | 1994-06-15 | 1994-06-15 | Light dewatering, bulky, chemical-mechanical pulp with low tip and fine material content |
| SE9402101-1 | 1994-06-15 | ||
| PCT/SE1995/000670 WO1995034711A1 (en) | 1994-06-15 | 1995-06-07 | A light drainability, bulky chemimechanical pulp that has a low shive content and a low fine-material content |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2192570A1 true CA2192570A1 (en) | 1995-12-21 |
Family
ID=20394398
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002192570A Abandoned CA2192570A1 (en) | 1994-06-15 | 1995-06-07 | A light drainability, bulky chemimechanical pulp that has a low shive content and a low fine-material content |
Country Status (14)
| Country | Link |
|---|---|
| US (1) | US5879510A (en) |
| EP (1) | EP0764225B1 (en) |
| JP (1) | JP3856466B2 (en) |
| AT (1) | ATE184929T1 (en) |
| AU (1) | AU705185B2 (en) |
| BR (1) | BR9508006A (en) |
| CA (1) | CA2192570A1 (en) |
| DE (1) | DE69512408T2 (en) |
| ES (1) | ES2139218T3 (en) |
| FI (1) | FI965014A (en) |
| NO (1) | NO309157B1 (en) |
| NZ (1) | NZ300088A (en) |
| SE (1) | SE9402101L (en) |
| WO (1) | WO1995034711A1 (en) |
Families Citing this family (27)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE504030C2 (en) * | 1995-02-17 | 1996-10-21 | Moelnlycke Ab | High bulk spun lace material and absorbency as well as process for its preparation |
| US6899791B2 (en) | 1997-08-08 | 2005-05-31 | Andritz Inc. | Method of pretreating lignocellulose fiber-containing material in a pulp refining process |
| EP0775232B2 (en) * | 1995-06-12 | 2003-05-02 | Andritz Sprout-Bauer, Inc. | Low-resident, high-temperature, high-speed chip refining |
| SE505388C2 (en) * | 1995-11-24 | 1997-08-18 | Sca Hygiene Paper Ab | Soft, bulky, absorbent paper containing chemitermomechanical pulp |
| FI113552B (en) * | 1999-12-09 | 2004-05-14 | Upm Kymmene Corp | Process for producing printing paper |
| FI113670B (en) * | 1999-12-09 | 2004-05-31 | Upm Kymmene Corp | Process for producing printing paper |
| US6585861B2 (en) | 2000-12-19 | 2003-07-01 | Metso Paper Karlstad Ab | Device for producing an extensible paper having a three-dimensional pattern |
| CN1250811C (en) | 2001-07-19 | 2006-04-12 | 安德里兹有限公司 | Four stage alkaline peroxide mechanical pulping |
| US20040200586A1 (en) | 2002-07-19 | 2004-10-14 | Martin Herkel | Four stage alkaline peroxide mechanical pulping |
| CN1839227B (en) * | 2003-10-02 | 2011-08-17 | 安德里兹有限公司 | Multi-stage AP mechanical pulping process with refiner flow line treatment |
| US8317975B2 (en) | 2004-04-20 | 2012-11-27 | The Research Foundation Of The State University Of New York | Product and processes from an integrated forest biorefinery |
| DE102005036075A1 (en) * | 2005-08-01 | 2007-02-15 | Voith Patent Gmbh | Process for the production of tissue paper |
| US7771565B2 (en) * | 2006-02-21 | 2010-08-10 | Packaging Corporation Of America | Method of pre-treating woodchips prior to mechanical pulping |
| US8734611B2 (en) * | 2008-03-12 | 2014-05-27 | Andritz Inc. | Medium consistency refining method of pulp and system |
| US20130000856A1 (en) * | 2010-03-15 | 2013-01-03 | Upm-Kymmene Oyj | Method for improving the properties of a paper product and forming an additive component and the corresponding paper product and additive component and use of the additive component |
| US8753476B2 (en) | 2010-10-06 | 2014-06-17 | Andritz Technology And Asset Management Gmbh | Methods for producing high-freeness pulp |
| EP3080354B1 (en) * | 2013-12-13 | 2019-08-07 | Stora Enso Oyj | Multiply paperboard |
| EP2924166A1 (en) * | 2014-03-25 | 2015-09-30 | Basf Se | Method for the manufacture of bleached wood fibre |
| DE102014112096B4 (en) | 2014-08-25 | 2020-02-20 | McAirlaid's Vliesstoffe GmbH | Absorbent fibrous web |
| SE539344E (en) | 2015-03-02 | 2020-02-11 | Billerudkorsnaes Ab | Pulp mixture for production of a paper product with high strength in z-direction |
| SE540961C2 (en) * | 2016-05-23 | 2019-01-29 | Holmen Ab | Method of providing a paper fibre composition by combining chemical and mechanical pulping |
| SE540115C2 (en) * | 2016-09-21 | 2018-04-03 | A paper or paperboard product comprising at least one ply containing high yield pulp and its production method | |
| UY37491A (en) * | 2016-11-23 | 2018-06-29 | Fibria Celulose S/A | INTEGRATED PRODUCTION PROCESS OF NANOFIBRILE CELL AND HIGH DRAINAGE ADAPTED MARKET PULP WITH REDUCED ENERGY CONSUMPTION |
| DE202018107142U1 (en) | 2018-12-13 | 2018-12-20 | McAirlaid´s Nordic OÜ | Absorbent mat for use as a base for food in a microwave oven |
| DE202018107140U1 (en) | 2018-12-13 | 2019-01-02 | McAirlaid´s Nordic OÜ | Insert for food packaging |
| DE202018107131U1 (en) | 2018-12-13 | 2019-01-02 | McAirlaid´s Nordic OÜ | Absorbent mat for use as a base for food in an oven |
| FI20215861A1 (en) * | 2021-08-17 | 2023-02-18 | Metsae Board Oyj | A method, use of the same, a pulp composition, and a system |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3661328A (en) * | 1970-03-30 | 1972-05-09 | Bauer Bros Co | Pulp refining system and process |
| SE413684C (en) * | 1974-09-23 | 1987-05-07 | Mo Och Domsjoe Ab | PROCEDURE FOR PREPARING CELLULOSAMASSA IN THE REPLACEMENT AREA 65-95% |
| SE397851B (en) * | 1976-04-02 | 1977-11-21 | Sca Development Ab | HOW TO PRODUCE FROM WOOD MATERIAL A CHEMISTRY MODIFIED THERMOMECHANICAL RAFFINE MASS |
| NO142091C (en) * | 1977-10-17 | 1980-06-25 | Myrens Verksted As | PROCEDURE FOR OZONE TREATMENT OF REFINO MECHANICAL AND THERMOMECHANICAL MASS. |
| SE422818B (en) * | 1978-03-31 | 1982-03-29 | Modo Chemetrics Ab | PROCEDURE FOR PROCESSING ALLULOSAMASSA BY BLACKING OR EXTRACTING |
| DE3321443A1 (en) * | 1983-06-11 | 1984-12-13 | Losenhausen Maschinenbau AG, 4000 Düsseldorf | VIBRATION ROLLER WITH POWER LIMITATION DEVICE |
| US4486267A (en) * | 1983-11-14 | 1984-12-04 | Mead Corporation | Chemithermomechanical pulping process employing separate alkali and sulfite treatments |
| SE441282B (en) * | 1984-02-22 | 1985-09-23 | Mo Och Domsjoe Ab | PROCEDURE FOR THE PREPARATION OF IMPROVED HOG REPLACEMENT MASS |
| US4562969A (en) * | 1984-03-05 | 1986-01-07 | Mooch Domsjo Aktiebolag | Process for preparing groundwood pulp as short fiber and long fiber fractions |
| SE466060C (en) * | 1990-02-13 | 1995-07-11 | Moelnlycke Ab | Absorbent chemitermomechanical mass and preparation thereof |
-
1994
- 1994-06-15 SE SE9402101A patent/SE9402101L/en not_active Application Discontinuation
-
1995
- 1995-06-07 DE DE69512408T patent/DE69512408T2/en not_active Expired - Fee Related
- 1995-06-07 EP EP95922830A patent/EP0764225B1/en not_active Expired - Lifetime
- 1995-06-07 ES ES95922830T patent/ES2139218T3/en not_active Expired - Lifetime
- 1995-06-07 AU AU27575/95A patent/AU705185B2/en not_active Ceased
- 1995-06-07 JP JP50202696A patent/JP3856466B2/en not_active Expired - Fee Related
- 1995-06-07 US US08/750,527 patent/US5879510A/en not_active Expired - Lifetime
- 1995-06-07 BR BR9508006A patent/BR9508006A/en not_active IP Right Cessation
- 1995-06-07 AT AT95922830T patent/ATE184929T1/en not_active IP Right Cessation
- 1995-06-07 NZ NZ300088A patent/NZ300088A/en unknown
- 1995-06-07 WO PCT/SE1995/000670 patent/WO1995034711A1/en active IP Right Grant
- 1995-06-07 CA CA002192570A patent/CA2192570A1/en not_active Abandoned
-
1996
- 1996-12-13 FI FI965014A patent/FI965014A/en not_active IP Right Cessation
- 1996-12-13 NO NO965375A patent/NO309157B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| WO1995034711A1 (en) | 1995-12-21 |
| FI965014A0 (en) | 1996-12-13 |
| SE9402101D0 (en) | 1994-06-15 |
| NO309157B1 (en) | 2000-12-18 |
| BR9508006A (en) | 1997-08-12 |
| NO965375D0 (en) | 1996-12-13 |
| NZ300088A (en) | 1999-01-28 |
| US5879510A (en) | 1999-03-09 |
| ES2139218T3 (en) | 2000-02-01 |
| ATE184929T1 (en) | 1999-10-15 |
| DE69512408D1 (en) | 1999-10-28 |
| AU705185B2 (en) | 1999-05-20 |
| EP0764225A1 (en) | 1997-03-26 |
| EP0764225B1 (en) | 1999-09-22 |
| JP3856466B2 (en) | 2006-12-13 |
| DE69512408T2 (en) | 2000-01-05 |
| NO965375L (en) | 1997-02-05 |
| FI965014A (en) | 1996-12-13 |
| JPH10506435A (en) | 1998-06-23 |
| SE9402101L (en) | 1995-12-16 |
| AU2757595A (en) | 1996-01-05 |
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