DE102006027006A1 - Producing fibrous material comprises producing a chemical solution, mixing the chemical solution with wood and/or annual plant; heating the chemical solution and pulping and then separating the woods and the chemical solution - Google Patents

Abstract

Producing fibrous material from wood or annual plants with a lignin content of at least 15% for soft wood and 10% for annual plants comprises: producing a chemical solution; mixing the chemical solution with wood and/or annual plant; heating the chemical solution and the woods and/or the annual plants and subsequently either removing free-flowing chemical solution and pulping the woods and/or the annual plants in the vapor phase or pulping the woods and/or the annual plants in liquid phase and separating the free-flowing chemical solution and the woods and/or the annual plants. Producing fibrous material from wood or annual plants with a lignin content of at least 15% for soft wood, of at least 12% for hard wood and of at least 10% for annual plants, related to the oven dried fiber mass, comprises producing a chemical solution with more than 5% of chemicals (calculated as sodium hydroxide) for soft wood or with more than 3.5% of chemicals (calculated as sodium hydroxide) for hard wood or with more than 2.5% of chemicals (calculated as sodium hydroxide) for annual plants; mixing the chemical solution with wood and/or annual plant in a given liquor ratio; heating the chemical solution and the woods and/or the annual plants at a temperature that is above the room temperature and subsequently either removing free-flowing chemical solution and pulping the woods and/or the annual plants in the vapor phase or pulping the woods and/or the annual plants in liquid phase and separating the free-flowing chemical solution and the woods and/or the annual plants.

Description

The The invention relates to a process for producing pulp Wood with a lignin content for conifers of more than 15% and for hardwoods more than 12%, based in each case on the produced otro pulp, wherein the pulp has predetermined strength properties.

It For example, processes are known which produce relatively high levels of fiber Lignin content of about 15% for Softwood and from above 12% for Produce hardwood. They provide a yield of 70% or more on the starting material used. These methods are based on chemical and / or mechanical decomposition of wood.

at Mechanical defibration of the wood is this - usually after a pre-damping - in grinding units in fiber bundles disassembled. These fiber bundles are then defibrillated by further grinding into individual fibers. The yield is very high, but also the required grinding energy. The strength of the wood fibers is - even after grinding - very low, because the fibers contain much native lignin and therefore little binding potential exhibit. They are also strong due to the mechanical defibration degraded what their recyclability impaired.

at Chemical decomposition of the wood usually affects chemicals increased Pressure and elevated temperature on the wood. As a typical process for high yield pulps is the NSSC procedure. But other methods like the force or the soda process can be modified so that High-yield fibrous materials be prepared (see "Choosing the best brightening process ", N. Liebergott and T. Joachimides, Pulp & Paper Canada, Vo. 80, No. 12, December 1979). If the dismantling of the original used wood should be limited to a maximum of 30% far fewer chemicals needed and used as in the manufacture of pulps completely from Lignin should be free. For the production of high yield pulps becomes the amount of chemicals dependent on from the desired Yield dosed. To a yield of about 70% based on otro To achieve wood usage is recommended in the prior art until to use 10% chemicals based on the starting material. at Whole pulps The use of chemicals often 30% of chemicals related to the otro Wood or above.

chemicals determine the process costs, so they are possible used sparingly. CTMP pulps are usually made with chemical quantities made from 3% to 5%. In known, industrially established Process for the preparation of high yield pulps, e.g. B. the NSSC process, up to 10% chemicals are based on the starting material used. With such a limited use of chemicals is still no recovery for the recovery the chemicals installed. Despite the relatively small amounts of chemicals leads this Type of pulp production to a considerable environmental, especially water pollution, not only because of the entry of chemicals but mainly because of the organic Freight being dumped in the receiving waters.

to Cost situation is to be noted, that with mechanically manufactured Fibers the sharply rising energy prices the manufacturing costs strain. For chemically produced high yield pulps the production with the costs for burdened the lost chemicals.

High-yield fibrous materials be for the current uses ground to high grinding levels. Just then they reach an acceptable level of strength. As high grinding degrees here are values of approx. 300 ml CSF (Canadian Standard Freeness), equate to 41 ° SR (Schopper-Riegler, s.u.) and 500 ml CSF, equal to 26 ° SR, as they are z. In "Choosing the best brightening process ", N. Liebergott and T. Joachimides, Pulp & Paper Canada, Vo. 80, No. 12, December 1979, for High yield fibers are described from softwood. A high one Freeness is achieved by using mechanical energy. The Fibers are rubbed against each other or on a grinder or on a grinding media and so in their surface properties changed to a better binding behavior. The high degree of grinding is so not an end in itself. It results rather from the requirements to the Festig keitseigenschaften the fiber.

The In particular, high yield fibers produced by mechanical and / or chemical means become used where not necessarily a high Endweißgrad and high whiteness stability required are. You could there are many other fields of application, if the strength level could be increased.

It It is therefore an object of the invention to provide a process for the preparation of Fiber with a lignin content of more than 15% for softwood and more than 12% for To propose hardwood, with the economic way fiber materials high strength can be produced.

• – Herstellen einer Chemikalienlösung mit mehr als 10 % Chemikalien (berechnet als NaOH) für Nadelholz oder mit mehr als 7 % Chemikalien (berechnet als NaOH) für Laubholz, jeweils bezogen auf die otro Menge des eingesetzten Holzes,
• – Mischen der Chemikalienlösung mit dem Holz in einem vorgegebenen Flottenverhältnis,
• – Erwärmen der Chemikalienlösung und des Holzes auf eine Temperatur über Raumtemperatur und anschließend entweder (1. Alternative)
• – Entfernen frei fließender Chemikalienlösung und
• – Aufschließen des Holzes in der Dampfphase oder (2. Alternative)
• – Aufschließen des Holzes in Gegenwart der Chemikalienlösung in flüssiger Phase und
• – Separieren der frei fließenden Chemikalienlösung und des Holzes.

This object is achieved with a method for the production of pulp from wood with a lignin content of at least 15% for softwood and 12% for hardwood, each based on the otro fiber mass, with the steps:

• - manufacture of a chemical solution with more than 10% chemicals (calculated as NaOH) for softwood or with more than 7% chemicals (calculated as NaOH) for hardwood, in each case based on the otro amount of wood used,
• Mixing the chemical solution with the wood in a predetermined liquor ratio,
• - Heating the chemical solution and the wood to a temperature above room temperature and then either (1st alternative)
• - Remove free-flowing chemical solution and
• - digesting the wood in the vapor phase or (2nd alternative)
• - digesting the wood in the presence of the liquid phase chemical solution and
• - Separate the free-flowing chemical solution and the wood.

The inventive method based on that for the production of high yield pulps higher Chemical quantities are used as usual.

More than 10% chemicals for Softwoods are well above the usual Chemical quantities for technical pulp production, also more than 7% chemicals for hardwood. This high use of chemicals yields fibers with good yield and excellent strength properties. So be for softwood at grindings of only 12 ° SR up to 15 ° SR Tear lengths of more than 8 km, but also tear lengths of measured more than 9 km and more than 10 km. For hardwoods at only 20 ° SR values of more than 5 km, but also more than 6 km and measured more than 7 km. This will be the desired high level of strength reached.

It is more extraordinary Advantage of the method according to the invention to see that these strength values already at extremely low Grind grades are achieved, as previously for high-yield fibers not available were. Fibers according to the prior art show at Mahlgrade from 12 ° SR to 15 ° SR for softwood pulp or from 20 ° SR for hardwood an unacceptable level of strength. Known pulps have at these low degrees of grinding so far result in fibers that no sufficient binding capacity have the corresponding and no sufficient strength properties for an economic Have offered to use such fibers.

By contrast, the fibrous materials produced by the process of the invention have tear lengths of more than 8 km up to 11 km and tear strengths of more than 70 cN up to more than 110 cN, even at grinding degrees in the range of 12 ° SR to 15 ° SR, based on a Leaf weight of 100 g / m ² . These low freeness levels are also achieved with a low specific demand for grinding energy, which is less than 500 kWh / t pulp for softwood pulps, and for hardwood pulp the demand for grinding energy may even be less than 300 kWh / t pulp. The realization that the high level of strength is achieved even at low grinding degrees of 12 ° SR to 15 ° SR for softwood and 20 ° SR for hardwood and below, is an integral part of the invention.

These high strength values are for Fibers with a lignin content of more than 15% for softwood pulps and more than 12% for Hardwood pulps previously unknown. The high strength level but also for Fibers with an even higher Lignin content can be maintained. The inventive method is also suitable for the production of softwood pulps with a lignin content of more than 17%, preferably more than 19%, advantageous of more than 21% relative to the otro pulp mass. Hardwood fibers with a lignin content of more than 14%, preferably more than 16 %, more preferably more than 18% can also with the inventive method produced and show a high level of strength.

The composition of the chemical solution used for the digestion can be determined in agreement with the wood to be digested and the desired pulp properties. As a rule, only one sulfite component is used. Alternatively or in addition, a sulfide component may be added get. Digestion with a sulfite component is not disturbed by the presence of sulfide components. Technically, sodium sulfite is usually used, but also the use of ammonium or potassium sulfite or magnesium bisulfite is possible. In particular, when high amounts of sulfite are used, can be dispensed with the use of an alkaline component, because even without the addition of alkaline components, a high pH value sets, which favors the digestion.

to PH adjustment and delignification support For example, an acidic and / or an alkaline component can be added. The alkaline component is usually sodium hydroxide (NaOH) used. Possible but is also the use of carbonates, especially sodium carbonate. All Information on chemical quantities of the digestion process in this Document, e.g. B. for the total use of chemicals or for the distribution of the sulfite component and the alkaline component, are calculated and indicated, unless otherwise stated as sodium hydroxide (NaOH).

As an acidic component, acids can be added in order to set the desired pH. However, preference is given to the addition of SO ₂ , if appropriate in aqueous solution. It is inexpensive and readily available, especially if the spent chemical solution z. B. based on sodium sulfite, after digestion is prepared for further use.

It is considered independent inventive performance, the advantages of using a Quinone component for the high yield digestion according to the invention to have recognized. Quinone components, especially anthraquinone, So far, in the production of pulps with minimal Lignin content used to end of the digestion an undesirable To prevent attack on the carbohydrates. By adding quinone components will it be possible the digestion of wood until almost complete degradation of lignin. It has turned out to be an unprecedented, unexpected property of Chinon components proved that these are the speed lignin degradation in the production of high yield pulps increase significantly. The duration of the digestion can z. B. in the production of softwood pulps by more than half, be shortened by more than three quarters depending on digestion conditions. This remarkable effect comes with minimal use of quinone reached. Optimal is a use of z. As anthraquinone, the between 0.005% and 0.5%. Use of anthraquinone of up to 1% also provides the desired effect. A use of more than 3% anthraquinone is usually uneconomical.

Out one or more of the aforementioned chemicals, a chemical solution is prepared. Most of time becomes an aqueous solution stated. As an option, the use or the addition of organic solvents be provided. Alcohol, especially methanol and ethanol in combination with water, particularly effective chemical solutions for the production high quality high yield fiber. The mixing ratio of Water and alcohol can for the respective raw material can be optimized in few attempts.

The for producing a pulp with a yield of at least 70% to be used according to the invention Amount of chemicals at least 10% for Softwood and at least 7% for Hardwood, in each case related to the otro wood mass to be split. The quality of the produced Pulp shows the best results in a chemical application up to 30% for Softwood and hardwood. Preference is given between 10% and 27.5 %, more preferably between 12% and 20% chemicals on the used otro wood, especially softwood added. The chemicals use for the production of softwood pulps leads to particularly good results, if he z. Between 15% and 20% is. For hardwoods lies the use of chemicals tends to be lower, preferably between 7% and 20%, more preferably between 10% and 15%.

As already explained above, setting a specific pH is by no means required. Only if, for example, special properties of the pulps (particularly high whiteness, a certain ratio of breaking lengths and tear strength) are to be achieved with the digestion, it may be useful to add acid or an alkaline component before or during the digestion. According to an advantageous embodiment of the method according to the invention, regardless of the chosen use of chemicals as a whole, a ratio between an alkaline component and sulfur dioxide (SO ₂ ) can be adjusted within a wide range. SO ₂ is mentioned here as representative of the above-mentioned acidic component. So it can be used instead of SO ₂ and an acid. Since the possibly added quinone component is used only in minimal amounts, usually well below 1%, it is negligible for setting this ratio. A ratio of alkaline component: SO ₂ in a range of 4: 1 to 1.6: 1 is well suited to carry out the process according to the invention and fibers with high strength to achieve properties. A customary, particularly suitable range is between 2: 1 and 1.6: 1. The adjustment of the proportionate components takes place depending on the raw material to be digested and the respectively selected process control (digestion temperature, digestion time, impregnation).

The inventive method can be carried out in a wide pH range. The ratio of alkaline component to acidic component or the use of a acid or an alkaline component can be adjusted that at the beginning of the process, a pH between 6 and 11, preferably set between 7 and 11, more preferably between 7.5 and 10 becomes. The more alkaline pH values between 8 and 11, for the inventive method are beneficial, favor also the effect of the quinone component. The inventive method is tolerant of pH; there are few chemicals for pH adjustment required. This has a favorable effect the price for Chemicals off.

Without further addition of acid or alkaline component arises, for. B. for softwood, at the end of the digestion a pH between 8 and 10, usually between 8.5 and 9.5 in the free flowing chemical solution as well as the dissolved ones organic components liquefied by the digestion. To the solved ones include organic ingredients especially lignosulfonates.

The Liquor ratio, so the relationship the amount of otro wood to the chemical solution is between 1: 1.5 and 1: 6 set. Preference is given to a liquor ratio of 1: 3 to 1: 5. In this area is a good and easy mix and impregnation of the to be closed Materials guaranteed. For softwood becomes a liquor ratio of 1: 4 preferred. For Wood chips with big surface can the liquor ratio also much higher lie to allow rapid wetting and impregnation. simultaneously the concentration of the chemical solution can be kept so high that the revolving amounts of liquid do not get too big.

The Mixture or impregnation the wood chips are preferably carried out at elevated temperatures. Heating up the wood chips and the chemical solution up to 110 ° C, preferably up to 120 ° C, particularly preferably up to 130 ° C leads to a fast and uniform digestion of the wood. For mixing or impregnating the wood chips is a period of up to 30 minutes, preferably up to 60 minutes, more preferably up to 90 minutes advantageous. The optimal time depends on the quantity the chemicals and the liquor ratio and the type of digestion (liquid or vapor phase).

Of the Digestion of the mixed or impregnated with the chemical solution Lignocellulosic material is preferably carried out at temperatures between 120 ° C and 190 ° C, preferably between 150 ° C and 180 ° C. For the most woods Digestion temperatures between 155 ° C and 170 ° C are set. Higher or higher lower temperatures can be set, but in this temperature range are the energy expenditure for the Heating and accelerating the digestion in an economic relationship to each other. higher Temperatures can also negative for the strength and whiteness of the Impact fibers. The generated by the high temperatures Pressure can easily by appropriate design of the digester be caught. Usually is the duration of heating only a few minutes, usually up to 30 minutes, advantageously up to 10 minutes, especially when using steam is heated. The duration of the heating up can be up to 90 minutes, preferably take up to 60 minutes, z. B. when in the liquid phase is disrupted and the chemical solution along with the wood chips too is heating.

The Duration of digestion will depend mainly on the desired Fiber properties selected. The duration of the digestion can be shortened to up to 2 minutes, z. For example the case of a vapor phase digestion of a hardwood with low Lignin content. It can also be up to 180 minutes, though z. B. the digestion temperature low and the natural lignin content of the to be closed Wood is high. Even if the initial pH of the digestion In the neutral range, a long digestion time may be required be. Preferred is the digestion time up to 90 minutes, especially in coniferous wood. Particularly preferred is the digestion time up to 60 minutes, advantageously up to 30 minutes. A digestion time of up to 60 minutes occurs mainly in deciduous trees in Consideration. The use of a quinone component, in particular anthraquinone, allows a reduction of digestion time up to 25% of the time required without the addition of anthraquinone. Is based on the use of quinone components waived, extended for comparable digestion results increase the digestion time by more than one Hour, for example from 45 minutes to 180 minutes.

To an advantageous embodiment the method according to the invention the duration of the digestion is set as a function of the selected liquor ratio. The lower the liquor ratio, the shorter the process duration can be set.

The Production of high yield pulp with high chemical use of more than 10% for softwood and more than 7% for Hardwood appears first uneconomical. But tests have shown that only a part the chemicals during the partial digestion of the lignocellulosic material consumed becomes. The predominant Part of the chemicals is discharged unused, either before the digestion (vapor phase digestion) or after digestion (Digestion in the liquid Phase). The actual consumption of chemicals is below the in the digestion solution used quantities.

Of the Chemical consumption is recorded as the amount of chemicals - related on the original amount of chemicals used - after removal or separation the chemical solution and, if necessary, the detection of chemical solution after defibering or measured in conjunction with a detection of the chemical solution becomes. The consumption of chemicals depends on the absolute amount the for the chemicals used, based on the otro to be broken down Carpentry and joinery. The higher the Use of digestion chemicals is the lower the direct Sales of chemicals. When using 27.5% chemicals Based on otro wood pulp, for example, only about 30% of used chemicals consumed. When using 15% chemicals However, 60% of the chemicals used are related to otro wood consumed as could be demonstrated in laboratory experiments. Of the Chemical consumption for the inventive method is according to a preferred embodiment of the procedure during digestion up to 80%, preferably up to 40%, more preferably up to 40%, advantageously up to 20%, particularly advantageous up to 10% of the chemical used at the beginning of the digestion becomes.

Of the Chemical consumption for producing a ton of pulp lies at about 6% to 14% sulphite and / or sulphide component and, if applicable, alkaline and / or acidic component and optionally quinone component based on otro pulp (deciduous and softwood). According to the invention this is sufficient Quantity of chemicals to a pulp with the given characteristics manufacture. However, to a uniform process result guarantee and possibly special, desired To get pulp properties, it may be useful prove, higher Chemical quantities for to use the digestion, z. As the above-mentioned up to 30% chemicals related to otro wood pulp.

Of the Use of these chemicals at the beginning of the digestion shows advantageous effect, since the fibers obtained in this way previously unavailable Properties, in particular high strength properties and high whiteness exhibit. In particular, no digestion method is currently available that has a wide pH spectrum from neutral to alkaline fiber with high strength generated. It has turned out to be particularly attractive economically that the invention produced Fibers with much lower energy consumption to specified Grinding degrees to grind are known as fibrous materials. In addition, develop the high strengths already at unusually low degrees of grinding from 12 ° SR up to 15 ° SR for softwood and from 20 ° SR for hardwood.

A surplus chemicals are present after mixing and impregnation of the wood with the chemical solution or after digestion in the free-flowing liquid. This surplus is before digestion (1st alternative) or after digestion (2nd alternative) deducted. After an advantageous development of the method, the composition of the removed chemical solution is detected and subsequently for the renewed use for the production of fibers on a given Composition set. The chemical solution before or after Digestion of the wood is removed, no longer indicates the exit set composition. At least part of the digestion used chemicals is - how described above - in the unlocked Material has penetrated and / or has been consumed during the digestion. The unused chemicals can without further ado for the next Digestion can be used. However, it is proposed according to the invention first to determine the composition of the removed chemical solution and then the consumed shares in z. B. sulfite, alkaline component, Quinone component or even water or alcohol supplement to restore the given composition for the next digestion. This supplementary step is also called strengthening designated.

It is to be regarded as a considerable advantage of this measure that the chemical solution even when removed before digestion, but also when removed after digestion, contains no or only very few substances, which are the result of renewed use of the fortified chemicals solution for the next digestion. The method according to the invention, which aims to provide an oversupply of digestion chemicals in the impregnation, can thus be extremely economical despite the initially uneconomic approach of high chemical use, because the removal or separation and the strengthening of the chemical solution can be carried out easily and inexpensively.

The inventive method is specifically controlled so that only as little as possible of the used Starting material is degraded or dissolved. The aim is to produce a pulp which contains a lignin content for softwood of at least 15% based on the otro fiber mass, preferably a lignin content of at least 18%, more preferably from 21%, preferably at least 24%. For hardwood is sought a lignin content of at least 12% based on the otro fiber mass to reach, preferably of at least 14%, more preferably at least 16%, preferably at least 18%.

The Yield of the process according to the invention is at least 70%, preferably more than 75%, advantageous more than 80%, in each case based on the wood used. These Yield correlates with the above lignin content of Pulp. The original one Lignin content of wood is specific to the species. The yield loss turns out in the present process predominantly as a loss of lignin In unspecific digestion methods is the proportion of carbohydrates clearly increased, z. B. because digestion chemicals are intrinsically undesirable You can also dissolve cellulose or hemicelluloses.

A Another advantageous measure is, after defibering and possibly grinding the lignocellulosic Material to remove the remaining chemical solution and one Re-use. In a preferred embodiment, this reuse can have two aspects include. For one thing, that will be during decomposed or dissolved organic matter, mainly lignin, continue to be used. For example, it is burned by process energy to win. Or it is prepared to be used elsewhere become. Second, the used and unused chemicals again prepared so that they are for a renewed, partial Digestion of lignocellulosic material can be used. To belongs the treatment of used chemicals.

To a particularly preferred variant of the method according to the invention the chemical solution used is used extremely efficiently. After pulping and possibly grinding, the pulp is washed, to the chemical solution as far as possible to displace by water. The in this washing or displacement process Contains resulting filtrate considerable Amounts of chemical solution and organic material. According to the invention, this filtrate is removed or separated chemical solution supplied before the chemical solution be strengthened and the next Excited becomes. The chemicals and organic components contained in the filtrate to disturb not digestion. As far as they still contribute to delignification while the next Provide information, their content is recorded in the chemical solution and in determining the for this amount of chemicals required. The chemicals further contained in the filtrate behave while inert for the upcoming digestion. They do not bother. The ones contained in the filtrate Organic components are also inert. you will be after the next Digestion in the treatment of the chemical solution continues to be used, either to generate process energy or otherwise.

It is considered to be particularly advantageous that by this leadership of the Filtrate less fresh water and less chemicals for digestion be used. At the same time a maximum of dissolved organic Material recorded. Even this improved use of the gone into solution organic material improves the economy of the method according to the invention.

details the method according to the invention and the device will be explained in more detail below with reference to exemplary embodiments.

• – Die Ausbeute wurde durch Wägung des eingesetzten Rohstoffs und des nach dem Aufschluss erhaltenen Zellstoffs, jeweils bei 105 °C auf Gewichtskonstanz (atro) getrocknet, berechnet.
• – Der Ligningehalt wurde als Klason-Lignin bestimmt gemäß TAPPT T 222 om-98. Das säurelösliche Lignin wurde bestimmt gemäß TAPPI UM 250
• – Die papiertechnologischen Eigenschaften wurden an Prüfblättern bestimmt, die nach Zellcheming-Merkblatt V/8/76 hergestellt wurden.
• – Der Mahlgrad wurde nach Zellcheming-Merkblatt V/3/62 erfaßt.
• – Das Raumgewicht wurde nach Zellcheming-Vorschrift V/11/57 ermittelt.
• – Die Reißlänge wurde nach Zellcheming-Vorschrift V/12/57 bestimmt.
• – Die Durchreißfestigkeit wurde nach DIN 53 128 Elmendorf ermittelt.
• – Die Ermittlung von Tensile-, Tear- und Burst-Index erfolgte gemäß TAPPI 220 sp96.
• – Der Weißgrad wurde ermittelt durch Herstellung der Prüfblätter nach Zellcheming-Merkblatt V/19/63, gemessen wurde nach SCAN C 11:75 mit einem Datacolor elrepho 450 × Photometer; die Weiße ist in Prozent nach der ISO-Norm 2470 angegeben.
• – Die Viskosität wurde bestimmt nach dem Merkblatt IV/36/61 des Vereins der Zellstoff- und Papier-Chemiker und -Ingenieure (Zellcheming).
• – Sämtliche %-Angaben in diesem Dokument sind als Gewichtsprozent zu lesen, soweit nicht im einzelnen anders angegeben.
• – Die Angabe "otro" in diesem Dokument bezieht sich auf "ofentrockenes" Material, das bei 105 °C bis zur Gewichtskonstanz getrocknet wurde.
• – Die Chemikalien für den Aufschluss sind in Gewichtsprozent als Natriumhydroxid angegeben, soweit nicht anders erläutert.

The following tests were evaluated according to the following rules:

• The yield was calculated by weighing the raw material used and the pulp obtained after the pulping, in each case dried at 105 ° C. to constant weight (atro).
• The lignin content was determined as Klason lignin according to TAPPT T 222 om-98. The acid-soluble lignin was determined according to TAPPI UM 250
• - The paper technology properties were determined on test sheets, which were prepared according to Zellcheming leaflet V / 8/76.
• - The degree of grinding was recorded according to Zellcheming leaflet V / 3/62.
• - The density was determined according to Zellcheming regulation V / 11/57.
• The breaking length was determined according to Zellcheming regulation V / 12/57.
• - The tear resistance was determined according to DIN 53 128 Elmendorf.
• Tensile, Tear and Burst Index were determined according to TAPPI 220 sp96.
• - The whiteness was determined by preparing the test sheets according to Zellcheming leaflet V / 19/63, was measured according to SCAN C 11:75 with a Datacolor elrepho 450 × photometer; the whiteness is given in percent according to ISO standard 2470.
• - The viscosity was determined according to the leaflet IV / 36/61 of the Association of Pulp and Paper Chemists and Engineers (Zellcheming).
• - All% figures in this document are expressed as weight percent unless otherwise specified.
• - The term "otro" in this document refers to "oven-dry" material that has been dried to constant weight at 105 ° C.
• - The chemicals for the digestion are given in percent by weight as sodium hydroxide, unless otherwise stated.

Example 1 - Digestion in the liquid phase

Spruce wood chips are, after damping (30 minutes in saturated steam at 105 ° C), treated with a sodium sulfite digestion solution at a liquor ratio of wood: digestion solution 1: 4. The total use of chemicals was 27.5% based on otro spruce wood chips. The pH at the beginning of the digestion was adjusted to pH 6 by addition of SO ₂ .

The with chemical solution impregnated Spruce wood chips were over a period of 90 minutes at 170 ° C heated and over Digested for 180 minutes at this maximum temperature.

Subsequently was the free-flowing liquid removed by centrifugation, collected and in an array to return unused liquid analyzed and strengthened and so for the next digestion provided.

The digested spruce wood chips were fiberized. subsets of the thus-produced pulp were ground for various lengths to To determine the strength at different degrees of grinding. The energy expenditure for defibering the partially digested spruce wood chips was less than 500 kWh / t of pulp.

Example 2

As in Example 1, but the pH at the beginning of the digestion was adjusted to pH 7 by addition of SO ₂ .

Example 3

As in Example 1, but the pH at the beginning of the digestion was adjusted to pH 8 by addition of SO ₂ .

Example 4

As Example 1; the pH at the beginning of the digestion was pH 9.4, without action to adjust the pH.

Table 1 Results of Examples 1-4, presented at freeness 15 ° SR

For Examples 1-4 described above, the following results can be stated:
The yield of more than 75% in each case based on the originally used wood pulp corresponds to a pulp with a lignin content of well over 20%. The average lignin content for spruce wood is given as 28% in relation to the otro wood mass (Wagenführ, Anatomie des Holzes, VEB Fachbuchverlag Leipzig, 1980). The actual lignin content of the pulp is higher than 20%, since during the digestion mainly, but not exclusively, lignin is broken down. Carbohydrates (cellulose and hemicelluloses) are also dissolved in small amounts. The values given show that the digestion has a good selectivity with regard to lignin and carbohydrate degradation.

Of the whiteness lies with values of over 55% ISO is unexpectedly high and thus provides a good starting point for a possibly subsequent Bleaching.

Around the spruce wood pulps of Examples 1 to 4 to a freeness from 15 ° SR To grind, a grinding time of 20 to 30 minutes is required. Developed up to a milling time of 20 minutes (freeness 12 ° SR-15 ° SR) the freeness is independent from the pH at the beginning of the digestion (pH 6 to pH 9.4) in one narrow corridor.

Also independently from the initial pH of the digestion and that required to reach the freeness Grinding time becomes a high level of strength at a grind level of 15 ° SR reached. Example 1 leads to an overall high level of strength with a breaking length of 8.9 km and a tear resistance of 53.8 cN. However, if the initial pH is 7 or above, it increases the tear length on 9 km and above. The tear resistance reaches values of 65 cN and above.

Example 5

As Example 4, but with beech wood chips. The pH also adjusts to pH 9.4 at the beginning of the digestion.

Example 6

As Example 5, but with poplar wood chips.

The Results of these outcrops shows Table 2. The beech and poplar pulps were with a Minimum energy dissipated (less than 300 kWh / t). They reached after only a few minutes extraordinary high grinding degrees. Already unground, more than 15 ° SR was measured. The hardwood pulps were therefore analyzed at freeness 20 ° SR.

The Yield is 75% and above, related to the otro wood chips. Again, the good shows selectivity the digestion according to the invention.

The so produced fibers already have despite the high yield one extraordinarily high whiteness on at over 65% ISO is. This is for a possibly subsequent Bleach laid a good foundation.

With a tearing length of more than 5 km at 20 ° SR, the beech has a tear that is remarkable for this type of wood length. The tear resistance of more than 50 cN is also remarkable. The strength level for the poplar pulp is even higher. A tearing length of more than 7.5 km and a breaking strength of 65 cN at 20 ° SR are not known for hardwood pulps with a high lignin content.

Table 2 Results of Examples 5, 6, presented at freeness 20 ° SR

Example 7

Of the Pulp according to Example 7 was from spruce wood chips under prepared according to the conditions of Example 4, with the following changes: additionally to the 27.5% total chemicals (sulfite and NaOH in given Relationship) became the chemical solution 0.1% anthraquinone added based on the amount of wood used. The duration of the digestion was shortened to 45 minutes.

Example 8

As Example 7, but with a total use of chemicals of 25% on the used otro amount of wood and a digestion time of 50 minutes.

Example 9

As Example 7, with a total use of chemicals of 22.5% and one Digestion time of 50 minutes.

Example 10

As Example 7, but with a total chemical input of 20% and a digestion time of 55 minutes.

Example 11

As Example 7, but with a total use of chemicals of 17.5% and a digestion time of 55 minutes.

Example 12

As Example 7, but with a total chemical input of 15% and a digestion time of 60 minutes.

Table 3 Results of Examples 7-11, presented at freeness 15 ° SR

First, you notice that by addition of 0.1% anthraquinone the duration of the digestion opposite 180 Minutes in Example 4 under otherwise unchanged digestion conditions decreased by 135 minutes (75% of digestion time) to 45 minutes can be. The results of the outcrops are comparable to how is shown in Table 4. This time gain is valuable, before All because the plants for pulp production smaller can be dimensioned. Another savings potential is that the for digestion required temperature only over a much shorter one Period must be maintained.

Further can be seen from the data in Table 3 that with decreasing use of total chemicals from 27.5% to 15% pulp with largely equal good properties is generated. These results are not dependent on the use of anthraquinone. The anthraquinone causes an acceleration of the digestion, but the desired pulp can be opened up without the addition of anthraquinone. The whiteness is for each the digestion examples at about 50% ISO and the lignin content in Examples 7 bis 11 between 21.5% and 22% based on otro pulp. The tear length is at over 10 km and tear resistance was measured to be greater than 70 cN, typically greater than 75 cN at 15 ° SR.

Table 4 Results of Examples 4 and 7, presented at freeness 15 ° SR

The explained below outcrops according to the examples 13 to 16 concerning vapor phase digestions.

Example 13

Spruce wood chips are used with 27.5% chemical use at a liquor ratio of wood : Chemical solution = 1: 5 at 120 ° C in the vapor phase for Impregnated for 120 minutes. The chemicals used are sulfite and 0.1% anthraquinone. At the beginning of the impregnation a pH of 9.4 is reached. After impregnation becomes the chemical solution away.

The with the chemical solution impregnated Wood chips are heated with steam in approx. 5 minutes to 170 ° C. This vapor phase at 170 ° C will over Held for 60 minutes. Then the steam is drained and inside of 30 seconds, the cooker is cooled to 100 ° C, and it raises ambient pressure one. The wood chips are removed from the stove and shredded. Aliquots of the spruce pulp thus prepared are ground and ground Partial quantities are determined by grinding degree and pulp properties.

Table 5 Results of Examples 13-16, presented at freeness 15 ° SR

Example 14

As Example 13, but with a digestion time in the vapor phase of 45 minutes. The use of chemicals is based on the 63.0% otro amount of wood increased.

Example 15

As Example 14, but with a digestion time of 30 minutes.

Example 16

As Example 14, but with a digestion temperature of 170 ° C.

The outcrops in the vapor phase show a small overall time requirement. Compared to the Digestion in the liquid Phase is the heating to the maximum digestion temperature much faster. The actual digestion then needs the same duration as boiling in the liquid phase. During the Vapor phase pulping is not free flowing chemical solution This will be after impregnation and before digestion deducted. It is therefore less offset with organic material as the chemical solution, which is removed after the digestion in the liquid phase. On the quality However, this does not have any significant influence on the fiber produced.

The Yield of the liquid phase extracts shown in Table 3 with the addition of Anthraquinone is above 75% related to the otro amount of wood. For the vapor phase digestions is this is also achieved with the exception of Example 14. The whiteness of the However, fibrous materials produced in Examples 13 to 16 is significantly lower Examples 7 to 12. Of only 32.2% ISO in the vapor phase digestion With a maximum digestion time of 60 minutes, the whiteness increases shortening digestion to 45 minutes at 39.1% ISO. Another reduction the digestion time to 30 minutes leads to an increase 43.1% ISO. A significant effect causes the reduction the maximum digestion temperature from 170 ° C to 155 ° C: the whiteness increases to 49.1% ISO.

The in the vapor phase produced fibers have excellent Strengths on. The tear length was measured at 10 km (Example 15) and at 11 km (Example 14) at 15 ° SR. The tear resistance was measured at 82.8 cN (Example 15) and at 91.0 cN (Example 14). These values correspond to the best values for high lignin fibers, the for outcrops in the liquid Phase have been reached or are still over. For fibers with a high lignin content from the prior art comparable strength values are not known.

With the tables 6 and 7 shown below it should be shown that the fibers produced according to the invention already offer good strength properties at grinding degrees of 12 ° SR. From these tables it can be seen particularly clearly that the fibrous materials according to the invention require only a small amount of energy during the grinding in order to build up high breaking lengths, without the tear propagation resistance being reduced. Grinding degree 12 ° SR was achieved in each case in 0-10 minutes; Grinding degree 13 ° SR 5-30 minutes, usually 10-20 minutes. To reach a grind level of 14 ° SR, the Jokro mill had to work for 30-40 minutes and for grind level 15 ° SR it was required between 35 and 40 minutes. It is obvious that one Grinding up to grinding degrees around 40 ° SR would require an enormous amount of grinding energy. A particular advantage of the method according to the invention is therefore to be seen in the fact that with low energy consumption to be milled fibers are produced with high strengths.

Tear length (km) for Examples 7-12, shown at different degrees of grinding

Tear strength (cN, 100 g / m ² ) for Examples 7-12, shown at different degrees of grinding

at Grinding degree 12 ° SR is the tear length with more than 6.5 km for Spruce pulp already well developed. The increase in tear length decreases with each additional grinding degree, at 14 ° SR to 15 ° SR is the strength potential the fiber is essentially exhausted. The tear resistance is 12 ° SR at a very high level. For further grinding down to grinding degree 15 ° SR is although a loss of tear length of about 19% (example 11) up to about 32% (example 7). Due to the high initial strength at 12 ° SR is the strength level at 15 ° SR but still very good.

Claims (18)

Method for producing wood pulp with a Lignin content of at least 15% for softwood and at least 12% for Hardwood, in each case related to the otro fiber mass, with the steps - Produce a chemical solution with more than 10% chemicals (calculated as NaOH) for softwood or with more than 7% of chemicals (calculated as NaOH) for hardwood, each related to the otro amount of wood - Mix the chemical solution with wood in a given liquor ratio - Heating the chemical solution and of the wood to a temperature above Room temperature and then - either (1st alternative) Remove free-flowing chemical solution and Unlock the Wood in the vapor phase - or (2nd alternative) catch up of the wood in liquid Phase and Separate the free-flowing chemical solution and of the wood. Method according to claim 1, characterized in that that a pulp containing at least 15% lignin, preferably at least 18% lignin, advantageously at least 21% lignin 24% based on otro pulp for softwood or with one Content of at least 14% lignin, preferably at least 16% lignin, particularly preferably at least 18% lignin based on otro pulp for hardwood will be produced. Method according to claim 1, characterized in that that for the preparation of the chemical solution, a quinone component is used. Method according to claim 1, characterized in that that for the decomposition of softwood 12% chemicals or more, preferably 15% chemicals or more, preferably 20% chemicals or more be used. Method according to claim 1, characterized in that that for the digestion of hardwood 10% chemicals or more, preferably 12% chemicals or more, more preferably 15% chemicals or more can be used. Method according to claim 1, characterized in that that for the preparation of the chemical solution sulfites and sulfides, individually or in mixture. Method according to Claim 6, characterized that for the preparation of the chemical solution, an acidic and / or a alkaline component, in particular an acid, sulfur dioxide, sodium hydroxide and / or a carbonate is used. A method according to claim 1 or 7, characterized in that for digestion an alkaline component and an acidic component, in particular SO ₂ are used, wherein the ratio of alkaline component: SO ₂ in a range of 4: 1 to 1.6: 1, preferably set to 2: 1. Method according to claim 1, characterized in that that the process at a pH between 6 and 11, preferred between 7 and 11, more preferably between 7.5 and 10 is performed. Method according to claim 1, characterized in that that a fleet ratio Wood: Chemical solution between 1: 1.5 and 1: 6, preferably between 1: 3 and 1: 5 becomes. Method according to claim 1, characterized in that that warming the chemical solution and wood up to 130 ° C, preferably up to 120 ° C, advantageous up to 110 ° C he follows. Method according to claim 1, characterized in that that warming of the wood and optionally the chemical solution up to 90 minutes, preferably up to 60 minutes, advantageously up to 30 minutes, particularly advantageous takes up to 10 minutes. Method according to claim 1, characterized in that that unlocking of the wood at temperatures between 120 ° C and 190 ° C, preferably at temperatures between 150 ° C and 180 ° C, is particularly preferably carried out at temperatures between 160 ° C and 170 ° C. Method according to claim 1, characterized in that that unlocking of the wood up to 180 minutes, preferably up to 90 minutes, especially preferably up to 60 minutes, advantageously up to 30 minutes, especially advantageously takes up to 2 minutes. Method according to claim 14, characterized in that that the duration of the digestion dependent on from the liquor ratio chosen becomes. Method according to claim 1, characterized in that that the consumption of chemicals during the digestion up to 80%, preferably up to 40%, more preferably up to 40%, advantageously up to 20%, particularly advantageously up to 10% of the chemical use at the beginning of digestion. Method according to claim 1, characterized in that that captures the composition of the removed or separated chemical solution and subsequently for the renewed use for the production of fibers on a given Composition is set. Method according to claim 1, characterized in that that after defibering and optionally grinding the digested lignocellulosic Material released chemical solution is removed and one Further use supplied becomes.