SE439332B - PROCEDURE FOR DELIGNIFICATION OF TREMATERIAL FOR THE PREPARATION OF CELLULOSAMASSA WITH IMPROVED PROPERTIES - Google Patents

Description

svao49es + 2 ear results similar to those obtained in the NSSC process, in terms of high yield, * The importance of the dye can not be overemphasized as this factor for of chemical recycling systems, which can enable Etnzvšnninq of the chemicals for mass cooking and destruction of dissolved vedauostanas, which could otherwise be an undesirable burden on the environment. Extraction processes suitable for NSSC pulp cooking are complex and expensive. than solution sometimes used is to burn the spent N55 'liquid can in a recycling system according to the power process. However, Detia_requires that the NSSC plant be located close to a "power plant", which may often not be the case. In addition, the chemicals obtained from the power recovery system are not suitable for use in a NJJC plant and must first be reworked at a significant cost. If the environmental requirements are so strict that a sulfur-free process must be used, then the WSJC process is in any case unusable.

An object of the present invention is to provide a masking process which enables a simplified chemical recovery, while providing good color and sufficient strength properties.

Semi-chemical pulps can be produced by the soda process, which uses sodium hydroxide as the active pulp cooking chemical, but it is used sparingly if ever because the strength and color of the pulp are not as good as in the NSSC process and the chemical cost is higher than for the semi-chemical sodium carbonate or sodium carbonate - -sodium hydroxide processes. currently prevents the use of semi-chemical soda masses in products I such as linerboard and bag and wrapping paper. . , than aspect of the present invention lies in a discovery that good color of chemical or semi-chemical pulps is due to a high residual content of alkali in the spent liquid, which results in a high residual pH at the end of the boiling period. This can be obtained by using an excess of strong alkali in the pulping process. It is already known that there is a connection between a good iron and a good yield, but lürvllgqandu uppiinníng lies in the discovery that at the same uthytv qnr an excess of alkali a better color; may have the same sweetness, when the yields are different, a lower yield pulp may have color properties similar to a higher yield pulp, if excess alkali has been used in producing low yield pulp. Although an excess of alkali will result in * Iíñbíï in uuALlTLï _7804963-2. high residual pH in buffered pulp cooking systems, a large difference in the amount of alkali cannot be reflected in the residual pH values especially when the pH value is high. Previous processes using sodium sulfite, sodium carbonate or sodium carbonate-sodium hydroxide would not have achieved this high residual pH, nor did the high yield soda mass processes give any high residual pH, as the first two do not use a sufficiently strong alkali, while the latter two normally use insufficient alkali. This is especially the case with the high-yield process (the semi-chemical process), in which the aim has been to consume as much of the added alkali as possible and leave a low residual pH. In the present invention, the use of excess strong alkalis gives a high residual pH of 9-14, preferably 12-13. with a cooking liquid containing substantially no sulfur-containing compounds and essentially a hydroxide or a carbonate of sodium, potassium, magnesium or calcium, the constituent amount of hydroxide or carbonate being present in such a large excess calculated on the wood material that the pH of the liquor after the cooking is 12 to 13.

The method according to the invention can be applied in both batch and continuous boilers, regardless of whether the latter is run in downstream or countercurrent. However, the method is not limited to conventional cooking equipment, but can also be applied to so-called blast gas production, in which chemically treated chips are defibrated by rapid or explosive pressure relief. The process is applicable to all types of wood, including deciduous and coniferous trees and non-woody materials such as straw, bagasse, etc. When wood is used, it can be barked or unbarked and it can contain branches, roots, rice and leaves as in the so-called Conventional semi-chemical cellulose pulp processes typically use temperatures of 165-1 ° C and the pH of the bonding liquid is normally 9-10 ° C. Even U.S. Pat. in 19006 was used.

In connection with uPPfiDDíngGn here it has been discovered that alkaline mnssnkoknxnz at lower temperature than normal can rosulturu in füiuïilrdd mnssnxill- iiiaaßv QUALITY 780496342 4 lïasthet. Therefore, the present invention provides a process for the delineation of lignocellulosic material characterized in that the cellulose material is boiled with a boiling liquid containing hydrocarbon or carbonate of sodium, potassium, magnesium or potassium. In the case of preheating according to this invention, boiling temperatures in the range up to IGOL can be used, although temperatures above 20 ° C are preferred. Temperatures up to 120 DEG-15 DEG C. are preferred. Working at temperatures up to 1603 has several advantages. An unexpected advantage is that the strength of the formed mass becomes higher when lower boiling temperature is used. There are also indications that in some cases the color improves and of course the lower boiling temperatures lead to an overall energy saving. A preferred form of the invention combines the use of excess alkali and low process temperatures, to give pulp with higher residual pH, which has good color and strength properties.

This process according to the invention has been found to give pulp with properties, including color, equal to those for_N¿SC pulp. Using this method, in a further embodiment of the invention, we have found that further acceleration of the boiling rate can be obtained and thereby either a lowering of the reaction temperature or the reaction time, by adding small amounts of quinonoid or hydroquinonoid compounds to the chips or to the cooking liquid. or the additive liquid. such additives may be made when the chips and / or liquid are introduced into the digester or as a separate pretreatment. Addition of quinonoid or hydroquinonoid compounds are particularly useful near low boiling temperatures are used because increased strength due to the lower temperatures can be obtained at shorter cooking times due to additions of the compounds.

A further advantage of using the described additives is a further improvement of the strength values of the pulp produced. as will be apparent from the examples, the strength values of the pulp, prepared according to the process of the invention, are superior to those of conventional NSSC pulp with the same yield.

The quinonoid or hydroquinonoid compounds that we have found to be good include anthraquinones (ÅQ) and anthrahydroquinones and their tautomers and derivatives, naphthoquinones and naphthohydroquinones and their tautomers and iderivatives and benzoquinones and benzohydroquinones and their tautnmurvr ...hrs.._ _ -. s _ _ 7804963-2 fifi h derivative. Examples of a tautomer of anthrahydroquinone are 10-hydroxyanthrone and 1,1-dihydradanthraquinone and an example of a tautomer of a naphthohydroquinone derivative is 1,4,4a, 9a-tetrahydroanthraquinone. Such compounds are described in more detail in our corresponding Lustralian Patent Applications Nos. 25519/77 and PC 9939/77 to which reference is made in this regard.

Preferably, compounds are used in an amount of 0.001-1%, preferably 0.01%, based on the weight of dry wood used. several of the preferred compounds are substantially insoluble in water, i.e. the use of them in the finely ground state, i.e. in the state of iitvn resin size. In some cases, it is advantageous to use diffuser or surfactant, such as Teepol or Cnmprow ëvnrumïrku). The use of the lignocellulosic feedstock with the quinoneoid / hydroquinonolide compound or tautomer in accordance with the invention may be varied to satisfy the requirements of the process in question. For example, the clononide / hydroquinonoid compound or tautomer may be present in a pretreatment liquid with which the lignocellulosic feedstock is soaked or impregnated: before adding the cooking liquid to the digester to complete the delignilivation process or or the compound may allow fi directly to the cooking liquid and lignocellulosic raw material in the digester, either in a single batch or in several batches, at different stages of the cooking or continuously throughout the cooking.

In the practical application of the process according to the invention, it may prove advantageous to use the soluble or more soluble hydroquinone compound (s), which can be formed in situ, by the reactant between the corresponding rabbit compound (s) and a reducing agent in a solution which is added to the cooking liquid or which is used at a later stage as cooking liquid. Inorganic or organic reducing agents may be used for the purpose, with preference given to organic compounds or compositions.

Inorganic reducing agents which can be used in this way include sodium or zinc dithionite (hydrosulfite), sodium borohydride or zinc powder and sodium hydroxide. Preferred organic reducing agents include carbohydrates such as glucose, xylose, manose or other monosaccharides, nacarose, cellubiosis, maltose or other disaccharides, organic acarids such as raffinose or polysaccharides such as starch, dextrin, oxidized starch or starch starches. xyian; amines XIïEÉHX1 QUALITY fi 7604963-2 s Ä 6 or alkane amines, such as ethylenediamine or diethylenetriamine or I ethanolamines, or aldehydes, such as vanillin.

Reducing substances present in the cooking liquid can in some cases be wasted or destroyed as the boiling process progresses, which results in the reducing effect being significantly reduced or completely lost. We have found that in such cases it is advantageous to add additional reducing agents periodically by injection into the digester for lignocellulose boiling in order to maintain a sufficient amount of the hydroquinone compound in the cooking liquid throughout the cooking period.

Pretreatment of the cellulosic feedstock in an impregnating liquid, containing the quinonoid or hydroquinonoid compound for a preparatory impregnation of the cellulosic feedstock with said compounds, can be carried out before the cellulosic feedstock is introduced into a digester to complete the noble ignition process. This pretreatment or preparatory step in boiling lignocellulosic feedstock aims to obtain better penetration and diffusion of the quinonoid compound into the lignocellulosic feedstock before the pulp is subjected to boiling; with a view to increasing the -good effects of quinonoid or hydroquinonoid excretion in the delignification boiling of the lignocellulosic feedstock.

The pre-negotiation or preparatory steps for cooking the lignocellulosic raw material can take place according to any of or any combination of steps A, B, C and D below. A. Impregnation of the lignocellulosic feedstock at normal or positive pressure (hydraulically or pneumatically applied) or negative pressure (vacuum) with an alkaline solution of the quinonoid or hydroquinonoid compound at temperatures from ambient temperature Lill 120%, which solution can be the normal boiling liquid or a liquid with another suitable composition, which is removed after the impregnation and then replaced with normal cooking liquid; or> n. extending the time required to raise the temperature of the lignocellulosic feedstock and the boiling liquid containing the quinone or hydroquinone compound from ambient temperature to a minimum boiling temperature of about 15 ° C; or 7 '' Maintaining the temperature of the lignocellulosic material: wch the boiling liquid containing quinonold or hydrnkinnnnfd æn ænhwen at a temperature in the range of 100 ~ 1R0ï for a period of 15-bU minutes, after which the normal temperature increase per unit time may continue to the maximum 150 ° ; or,,., ... _ __, ..-.__ -.-_ V. __ ..

Poon in fl llAuïv gvg 7804963-2 D. recycling of spent or partially consumed liquid from a previous boiling or from one or more stages of a multi-stage process or from any point in a continuous boiler, usually near the top of such a boiler, to a pre-impregnation stage which can be run either batchwise or continuously.

In working step A. above, the impregnation period can be up to 1 hour before proceeding with the cooking process, which can be carried out at a temperature of up to 150% for a period of 0.5-5 hours. In the working step B. above, the extension period can be up to 2-3 hours before fi exposing with the cooking process as in step A. In the working step C. above, the period to reach the temperature 100-120% can be 0.5-2 hours , while the boiling period after 15-60 minutes delay at 100-120% may be 0.5-5 hours at temperatures as in step A. above. In some cases, the time it takes to reach the desired boiling temperature is sufficient to achieve a satisfactory pulp yield, so that no cooking time is required.

Pretreatments of the type described above improve the pulp quality and additive recirculation, as in treatment D, and make it economically possible to use additives.

In cases where reduction of insoluble or sparingly soluble quinone compounds to the hydroquinone form is carried out as generally indicated above and at lower liquid circulation rates, the presence of a surfactant may keep the quinone compound in suspension during reduction to hydroquinone form, the proportion of spit or insufficiently cooked fragments in the resulting the mass is reduced.

In some cases, especially when batch boilers are used, it is advantageous to operate at higher liquid circulation rates than normal in boilers, for example liquid circulation rates up to 10: 1 relative to the normal speed. Thus, under normal operating conditions, the liquid circulation speed is about 6-10 circulations of total liquid per hour, but we have found, however, that the method according to the invention makes it possible in a good way to use pumps operating at \ fi & spoon ~ - circulation speeds of up to 60-100 circulations of total fluid per hour. However, this is not essential in all cases and excellent results can be obtained with normal circulation rates.

The absence of sulfur compounds in the process of the invention not only eliminates the remarkable odors often associated with the presence of such compounds in a recycling system, but also makes relatively simple recovery systems applicable to Poóšxlï QUALITY i '7804963-2 g 8. In addition to the normal recovery furnace, suitable systems include fluidized bed incineration, wet incineration and processes described in Australian Patent Application No. 73885/74 and GB Patent No. 1,407,272.

The practical examples set forth in the table below illustrate the preferred method of the invention. The table, diagrams and further examples below show the preferred methods of the invention; In all cases, a batch of 400 grams of pre-dried chips (either eucalyptus or pine) was boiled in a rotating electrically heated digester using a liquid wood ratio of 3.5: 1 and a period of 1.5 hours from ambient temperature to boiling temperature. Other conditions are as shown in the table and the individual examples. The pulp properties were determined using the Appita Standard Method after pickling in the Lamp Mill. For pulp prepared from mixed species and from ash-type eucalyptus, the calculations gave freenesstal of 400 resp. 200 C.S.F. (Canadian Standard Freeness).

In Example 1, an NSSC boiling liquid was used instead of NaOH liquid and the liquid used in Example 1 is 9.8% sodium sulfite and .3% sodium bicarbonate based on oven dried wood.

In the table and elsewhere in this description, the color "tristimulus green reflectance factor" means. _ ___ '____._...-....._.-- __- GL _ 6 9 an. w: cwzuu muøUcOU: 7 .. omm omá www www »än o? : f mvíåpmmøux 05 Ná fi vs. fw »é 1 2 :: Uøcm fi u fifi m mm> .m mw ww mm fi. m ov @ .w mw M oz oz ß. fi aw ^ m \ mE mmxv MU xw fl cwmcmunm cv av mm ww om am mm mm av mv ww> w_ m.mm om mm m wm mumm ø.m fl w.m fl m.m fi m.o fi m. fifi m.w fl N. fifl w.o fi w.m fl æ.m fl m.m fi o.m fi m m.o fl fi.fl a w.ww m. fifi o.> H Im mcmxmuw> M, wñmx fl unnmm _ W _ fififi 1 wo fi m fi www www www www mm fl amd www wow mo fl w mm fi wm fi www »vw www” Hmu mmamx M _,. mv ww ww mm mm ßw mo om mr mn mm ww.N mß fi ß oß oß on .xuo »mcm: \ umxnou 6 W lwcmø Rv wu> nu3 .N20 m5 må fl .f .v m5 fi må m mä NM N m .f fl W 2: .aswuwmc fi cuj MW lxox U fl> v fi ßfx Om fl Qm fi Om fi ow fi Ow fl ow fl Om fi om fi Om fi o flfl Om fi Ow fi w Ow fi ouw fi Ow fi om fi Oß fi ww mWw mEw. ma ma Uwwz Zuma »Dmxhoß m lwcms mo fi v: Omz wo« .o fi. o «.o fi. ø fl. c fi. o fi. o 0 ^ Uw> Umxuoumï n _ Lwcm: mn m3 ax. . zw <uwuum mnmvcm fi m fl xm <uwuum mvmncm fi m Uw> @ .Sw må 3 Ü Ü 3 3 3 m w ß w m .q m fi Hwasmxwwí.

MÛUQ> HÜUÖÜ arm UCmnCv-ÛMÜÜOM MW fi EWVTwHQI I H JÅHQJMH.

Fooï: QBÄLITY vsouess-z i g The following 12 comparisons of figures in the table illustrate the application of the invention. A comparison between examples 3 and 4 shows the clear effect of excess alkali on the pulp paint. Example 3 with higher residual pH, which comes from excess alkali, has better color than Example 4. 2. Example 3 compared to Example 5 confirms the effect of high residual pH.

Example 3 (high pH) has a much better color than Example 5 (low pH), despite the slightly lower pulp yield in the previous case. Example 6 compared to Example 8 again confirms that the use of a higher alkali batch and the consequent higher residual pH gives a better color despite a lower yield. The differences in measured pH values at these alkaline levels are not large, due to the buffering of the spent liquid at the end of the boiling, but the alkalinity in Example 6 must be clearly higher than in Example 8. Example 6 compared with Example 7 shows the combined effect of increased alkali charge and reduced temperature (Example 6) at the same pulp yield. Large differences in color should not be expected as the residual pH is higher in both cases, but a noticeable effect is observed.

. Example 7 compared to Example 8 shows the beneficial effect of lower boiling temperature on the pulp strength values. In these cases, pulp was boiled with the same amount of alkali at different temperatures and despite the fact that Example 7 (150%) has the lower yield, Example 8 (140¶) has higher strength values. If pulp is boiled at the same temperature under otherwise similar conditions, the pulp with a lower yield normally has a higher strength. Example 8 compared to Example 9 further confirms this. at the same pulp exchange, the pulp cooked at a lower temperature has a higher strength. Example 5 compared to Example 14 shows the accelerating effect of anthraquinone addition. By using the same alkali batch and temperature, a yield of 73% was obtained without anthraquinone and a yield of 69% with anthraquinone. Note that with the addition of anthraquinone, only half the cooking time is necessary. 8. Example 10 compared to Example 11, shows improvement of pulp color obtained in the presence of anthraquinone by increasing alkali addition and residual -PH at the same pulp yield and Kappatal. _9. Example 10 compared to Example 14 shows that under otherwise similar cooking conditions, a lower temperature results in improved pulp color at the same yield. Residual pH is slightly higher in Example 14 than in Example 10, but at values below 11 this should have little effect on the color.

Example 2 compared to Examples 10-2 shows the clear improvement in pulp strength obtained with the addition of anthraquinone. 780ß963 ~ 2 11 11. Example 15 shows a preferred combination of pulp cooking conditions using a high alkali addition and high residual pH, a low boiling temperature and anthraquinone. The resulting pulp exhibits excellent color and higher strength. Example 7 compared to Examples 16 and 17 shows the significant increase in pulp strength obtained by using anthraquinone, in addition to a noticeable increase in the pulp boiling rate.

The table above shows the advantages that can be achieved according to the method according to the invention. As stated above, an advantage is the production of lightly colored pulp by regulating the residual pH. The effect of pH on the paint is further shown in Figure 1, which shows a graph of color as a function of residual pH for pulp prepared at the same boiling temperatures and similar yields.

There will be a clear improvement in color as the residual pH increases. The neglected effect of residual pH on the color of semi-chemical soda mass does not appear to have been known in the technical literature to date.

A further advantage of the process according to the invention, which is illustrated by the examples, is the use of low pulp boiling temperatures. The invention enables the use of temperatures well below those hitherto used or considered practical for the preparation of semi-chemical pulp of the type described. The use of such low temperatures results not only in energy savings, but also in an unexpected improvement in the strength of the paper made from the pulp. (Commonly referred to as pulp strength).

This is further illustrated in Fig. 2 where the burst index in diagrams is plotted as a function of pulp yield for two different pulp boiling temperatures.

Compared to using 140%, 130% gives an increase in burst index of 0.1-0.4 units depending on the pulp yield.

Figure 2 - Examples 18 and 19 show the effect of mass cooking with anthrahydroquinone.

The results were generally similar to those obtained using anthraquinone (Example 17).

Example 180 Semi-chemical soda mass cooking with anthrahydroquinone Ash-type eucalyptus chips were boiled using a total of 15% sodium hydroxide and 0.1% anthrahydroquinone on oven-dried wood for 0.35 hours and 150%. Anthrahydroquinone was prepared by dissolving 0.4 grams of anthraquinone in 200 ml of water containing 8.0 grams of glucose and 30 grams of mumium hydroxide and boiling it in a nitrogen atmosphere. but QUALmj vaoaess-2 12 Total yield 1 72% Capacity '120 Consumed liquid on 12.9 Color 40 Burst index 5.0 (kPa m2 / g) Wear length (km) 8.7 Bxemgøl 19 Semi-chemical soda mass baking with anthrahydroquinone The wood and cooking conditions were the same as for example 18 Dantrahydroquinone was prepared by dissolving 0.4 grams of anthraquinone in 200 ml of water containing 0.5 grams of sodium dithionite and 30 grams of sodium hydroxide and boiling it in a nitrogen atmosphere.

Total yield 71% Capacity 110 Consumed liquid pH 12.9 Color 41 Explosion index 5.2 (kpa m2 / g) s1it1length (km) 8.7 Examples 20 and 21 show the effect of mass boiling with 10-hydroxyanthrone resp. 1,4-dihydroanthraquinone are both tautomers of anthrahydroquinone. These compounds are soluble in alkali and are believed to be converted to anthrahydroquinone in alkaline solution. They are at least as effective as anthraquinone (compare Example 12) and can be used with good results, where it is desirable to use a soluble additive which can quickly impregnate the wood before the pulp cooking begins.

Example gel Semi-chemical soda ash cooking with 10-hydroxyanthron Chips of mixed species of eucalyptus were boiled using 15% sodium hydroxide based on oven-dried wood and 0.1% 10-hydroxyanthron on oven-dried wood. The time at 140% was 1 hour. 2 Total yield _ 67% Capacity 122 Consumed liquid pH 12.0 Color 29 780fl | 963 r2 13 “Example gel 21 Semi-chemical soda ash cooking with 1,4-dihydroanthraquinone The wood and pulp cooking conditions were the same as for example 20.

Total yield 65.5% Kappatal 121 Consumed liquid pH 12.1 Color 28 Example 22 shows the effect of pulp boiling with 1,4,4a, 9a-tetrahydroanthraquinone. This compound can tautomerize in alkaline solution to 1,4-tetrahydroanthrahydroquinone, which can also be considered as a substituted naphthohydroquinone.

Example 22 Semi-chemical soda mass cooking with 1,4,4a, 9a-tetrahydroanthraquinone The wood and mass cooking conditions were the same as in Example 21.

Total yield 6S.1% Kappatal 122 Consumed liquid pH 12.0 Color 29 Examples 23 and 24 show the present invention applied to pine chips. Pulp prepared with higher alkali addition and residual pH (Example 23) has the better color at the same yield.

Exemgel 23 Bxemgel 24% caustic soda 13% 11% Cooking time 1.5 h 2.5 h Yield 74.5% 75.1 Kappatal 168 164 Residual pH 12.9 7 12.4 Color 35 - 30 V .....-._......__. __....._._ -.._...,. . . V

Claims (6)

78049634 14 Patent claims A process for the delignification of wood material for the production of cellulose pulp with improved color properties, characterized in that the wood material is boiled with a cooking liquid containing substantially no sulfur-containing compounds and mainly a hydroxide or a carbonate of sodium, potassium, magnesium or calcium, wherein the constituent amount of hydroxide or carbonate is present in such a large excess calculated on the wood material that the pH value in the liquor after boiling is 12 to 13. Process according to Claim 1, characterized in that the cooking liquid mainly contains sodium hydroxide and / or sodium carbonate. Process according to Claim 1, characterized in that the boiling takes place at a temperature between 120 and 150 ° C. A method according to claim 1, characterized in that a quinone or a hydroquinone compound is added to the cooking liquid in an amount of 0.01 - 0.3% by weight based on dry wood material. 5. A process according to claim 4, characterized in that the added compound is an anthraquinone, an anthrahydroquinone, a naphthoquinone, a naphthohydroquinone, a benzoquinone or a benzohydroquinone or tautomers of such compounds. 6. A process according to claim 5, characterized in that the added compound is 9,10-anthraquinone, 9,10-anthrahydroquinone or 1,4,4a, 9a-tetrahydroanthraquinone.