WO2009015699A1

WO2009015699A1 - Lignocellulosic fibrous material from annual plants

Info

Publication number: WO2009015699A1
Application number: PCT/EP2008/002086
Authority: WO
Inventors: Esa-Matti Aalto; Hans-Ludwig Schubert
Original assignee: Voith Patent Gmbh
Priority date: 2007-07-31
Filing date: 2008-03-15
Publication date: 2009-02-05
Also published as: DE102007036382A1

Abstract

The invention relates to unbleached lignocellulosic fibrous material from annual plants, having a tear length of more than 4.5 km at 20 °SR and a lignin content of at least 8% in relation to the unbleached oven-dry fibrous material and an bleached fibrous material from annual plants. The invention also relates to two methods for the production thereof.

Description

Lignocellulosic pulp from annual plants

The invention relates to a lignocellulosic pulp of annual plants and a method for producing such a pulp from annual plants.

For the purposes of the present invention, the annual plants include not only grasses or parts thereof (bamboo, straw) but also fibrous plant components such as bagasse or banana peels. Lignocellulosic fibers from annual plants are used, inter alia, for the production of paper and cardboard. A large number of industrially produced lignocellulosic fibers are known, which differ greatly in their properties:

As wood pulp fibers are (also from annual plants) referred to, which are produced by mechanical defibration of the fiber composite by means of grinding or grinding units. In the production of wood pulp hardly any wood substance or lignin is broken down. The biomass originally used is found almost entirely in wood pulp. In the case of mechanical defibration of the annual plants, they are broken down into fiber bundles in milling aggregates, usually after pre-damping. 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 fibers is very low, even after grinding, because the fibers contain much native lignin and therefore have little bonding potential. They are also greatly reduced by the mechanical defibration, which impairs their recyclability. The wood pulp production requires high energy input.

Recent processes for making pulp try to improve fiber properties and / or reduce energy requirements by pretreating the annual plants with steam and / or chemicals. These include in particular CTMP (Chemo-Thermomechanical Pulp) and TMP (Thermomechanical PuIp). At CTMP, used in the technical application usually between 1 - 5% by weight of chemicals based on otro wood to allow partial release of the fiber composite. Wood pulp is generally characterized by low strength properties, in particular low tearing length and particularly low tearing strengths, and high opacity and light scattering with low whiteness and high susceptibility to yellowing.

Pulp refers to fibers that are produced by chemical dissolution of the fiber composite from lignocellulosic raw material. In the manufacture of zeolite, chemicals are used which usually act on the biomass under high pressure and high temperature. With more or less extensive removal of the lignin and part of the carbohydrates, ie with significant loss of yield, from annual plants produce fibers with good strength properties, in particular high tenacity and good bleachability to high whiteness and low tendency to yellowing. The energy required to produce the pulp is recovered from the digestion liquor.

For the use of the fibers, the lignin content is often not critical. Critical is usually the strength level, as it often limits the application areas. Numerous methods have therefore been developed which attempt to achieve a higher level of strength on the basis of pulp production processes, even for higher lignin fibers.

One such technique, which has become established in practice, is the NSSC process. Using as small amounts of sulphite as possible, the aim in industrial applications with neutral to slightly alkaline pH values is to achieve the highest possible strength of the fiber with minimal degradation of lignin. The chemical quantities are kept as low as possible in practice. Fibers produced by the NSSC process are usually used unbleached.

Another method is the bisulfite process, which operates at pH 4. Other processes, such as the Kraft process (also called sulfate process) or the soda process, which in themselves for the production of pulp with minimal Lignin content has been developed and tested for its suitability for the production of high yield pulps.

In the suitability test for such fibrous materials, it is always assumed that it is based on the practical experience that, due to the high lignin content, the fiber has only unsatisfactorily low strengths in the unground or in the slightly ground state and economic usability is not given. A good overview of high yield pulps from the raw material wood is provided by "Choosing the best brightening process", N. Liebergott and T. Joachimides, PuIp & Paper Canada, Vol. 8o, No.12, Decem- ber 1979, T391 - T395 , There, the achievable strength level is given as a function of the yield and the lignin content for unbleached pulps, which were prepared by various methods. As a lower limit for fibers usable for papermaking, the strength level is measured at 500 ml CSF (26 ^° SR) and a comparative measurement is made for 300 ml CSF (41 ^° SR). At yields of approx. 80%, cracking lengths (breaking length) of approx. 9-10 km for 500 ml CSF (26 ⁰ SR) are achieved for spruce. With further grinding, the strength values increase. These already relatively high values are achieved by digestion in the acidic pH range (bisulfite digestion, acid sulfite digestion). For fibers from neutral and alkaline outcrops (neutral sulphite digestion, power and soda digestion) significantly lower strength values are specified, which also have to be produced with a multiple higher use of fiberization and grinding energy. This can be seen from the higher RPM revolutions of the PFI grinder required to achieve a freeness of 500 ml CSF (26 SR) and 300 ml CSF (41 ^° SR), respectively.

For bagasse fibers are known, the z. B. at 523 ml of CSF have a surfactant factor of about 5000 and a Tear Factor of about 46. The whiteness of such fibers is about 35% ISO. Chemicals determine the process costs, so they are used as sparingly as possible. CTMP pulps are usually manufactured with chemical quantities of 1% to 5%. In known, industrially established processes for the production of high yield fibers, eg. As the NSSC process, up to 10% chemicals are used based on the starting material. With such a limited use of chemicals, there is preferably no recovery for the recovery the chemicals installed.

Despite the relatively small amounts of chemicals, this type of pulp production leads to a considerable environmental, especially water pollution, not only because of the chemical entry but mainly because of the organic cargo that is discharged into the receiving waters.

With regard to the cost situation, it should be noted that in the case of mechanically produced fibrous materials, the sharp rise in energy prices weighs on production costs. For chemically produced high yield pulps, production is burdened with the cost of the lost chemicals.

The high yield fibers produced by mechanical and / or chemical means are used in particular where it is not absolutely necessary to have a high final whiteness and high whiteness stability. They could open up many more fields of application if the strength level could be increased.

Starting from the described prior art, it is an object of the invention to provide an unbleached and a bleached pulp from annual plants, which offers a high level of strength at high lignin content of the fiber.

This object is achieved with a lignocellulosic pulp of annual plants with a tearing length of more than 4.5 km at 20 ⁰ SR and a lignin content of at least 8% based on the unbleached otro pulp.

The above-described pulp has a lignin content of at least 8% based on the otro pulp. This lignin content is determined by determination of the Klason lignin and the acid-soluble lignin (for definition see below). Klason lignin and acid-soluble lignin together give the lignin content of the respective pulp. The lignin content of the annual plant

However, pulp may also be quite higher, in particular more than 10%, more than 12% or more than 14%. The higher the lignin content of the annual plant fiber with a breaking length of more than 4.5 km at 20 ^° SR, the lower the yield losses in producing the pulp. This increased yield increases the competitiveness of the pulp.

The fibrous material of annual plants according to the invention differs from the prior art in that the fibers show high strength values even with a much lower degree of beating than known fibers of annual plants. The freeness is a measure of the dewatering behavior of a fiber suspension. At a freeness of 20 ⁰ SR, the fiber is morphologically changed only slightly. Known fibers z. Example of straw or bamboo with relatively high lignin content have at 20 ⁰ SR on a structure that is not able to build a good bond to adjacent fibers - and thus an acceptable static strength level. However, the fiber material of the invention is already at a low degree of beating of 20 ⁰ SR -and thus by little effort to Mahlenergie- able to build a good bond to adjacent fibers.

The achievable strength values are for annual plants with a lignin content of at least 8% over 4.5 km. Values of more than 5 km, of more than 6 km and, preferably, more than 7 km of breaking length of 20 ⁰ SR each are readily attainable for these fibrous materials.

However, the pulp of annual plants according to the invention is not only distinguished by high tear lengths. Rather, the strength level is high overall. Thus, the annual plant fiber material of the invention having a lignin content of more than 8% at 20 ⁰ and SR based on a sheet weight of 100 g / m ² Durchreißfes- a humidity of at least 45 cN. This tear resistance combined with high breaking lengths even at such unusually low degrees of beating of 20 SR ⁰ for annual plants is not known from the prior art.

At the same time, with a high lignin content of more than 8%, the pulp has an unusually high whiteness. After digestion, ie without any bleaching treatment, values of 40% ISO and more are measured. It is also easily possible to achieve values of over 50% ISO. As the lignin is generally considered to be a colorant for the pulp, it is remarkable if, despite the high Lignin content such a degree of whiteness is achieved.

If the pulp according to the invention is subjected to a bleaching treatment, the fiber properties improve considerably. Bleaching treatment is required for some applications with higher whiteness requirements; but it also aims to adjust and improve fiber properties. The bleached pulp not only has a significantly higher whiteness of more than 6o% ISO, preferably more than 65% ISO and advantageously more than 70% ISO. The bleaching treatment increases the breaking lengths to more than 5.5 km, preferably to more than 5.5 km, more preferably to more than 7.5 km at 20 ^° SR. During the bleaching treatment, the puncture resistance can be stabilized.

Process for the production of pulp from annual plants

As described above, processes are known which produce fibers from annual plants with a relatively high lignin content of more than 7%. They provide a yield of 70% or more based on the starting material used. These methods are based on chemical and / or mechanical decomposition of annual plants.

It is therefore an object of the invention to propose processes for the production of pulp from annual plants with a lignin content of more than 8%, with which fibers of high strength can be produced in an economical manner.

This object is achieved with a first process for the production of pulp from annual plants with a lignin content of at least 8%, in each case based on the otro fiber mass. This first method comprises the steps:

Producing a chemical solution with more than 5% of chemicals (calculated as NaOH), in each case based on the otro amount of annual plants used, - mixing the chemical solution with the annual plants in a predetermined liquor ratio,

Heating the chemical solution and the annual plants to a temperature above room temperature and then either (1st alternative)

Removal of free-flowing chemical solution and digestion of the annual plants in the vapor phase or (2nd alternative) - digesting the annual plants in the presence of the liquid phase chemical solution and separating the free-flowing chemical solution and the annual plants.

The first method according to the invention is based on the fact that higher quantities of chemicals are used for the production of high-yield fibers than has hitherto been customary. More than 5% of chemicals are used significantly above the usual chemical quantities for technical pulp production from annual plants. This high use of chemicals yields fibers with good yield and excellent strength properties. Thus, for annual plants with a lignin content of 8% or more at grindings of only 20 ⁰ SR values of more than 4.5 km, but also tear lengths of more than 5 km and more than 6 km are measured. This achieves the desired high level of strength.

It is to be regarded as an extraordinary advantage of the method according to the invention that these strength values are achieved even at extremely low degrees of grinding, which were previously unavailable for high-yield fibers. Einjahrespflanzen- fibrous materials according to the prior art exhibit an unacceptable level of strength at freenesses of 20 ⁰ SR. Known pulps have so far yielded fibers at these low degrees of grinding which have not exhibited sufficient binding power and which accordingly have not provided sufficient strength properties for economical use of such fibers.

By contrast, the fibrous materials produced by the process according to the invention have tear lengths of more than 4.5 km to more than 7 km and tear strengths of more than 45 cN to more than 60 cN, even at degrees in the range of 20 ^° SR, based on a sheet weight of 100 g / m ² . These low levels of grinding are moreover achieved with a low specific requirement of milling energy, which may even be less than 300 kWh / t of pulp. The realization that the high level of strength is already achieved at low degrees of grinding of 20 ⁰ SR and below, is an essential part of the invention.

These high strength values are not yet known for pulp from annual plants with a liginine content of more than 8%. However, the high strength level can also be maintained for fibers with an even higher lignin content. The method according to the invention is also suitable for the production of annual fiber crops having a lignin content of more than 10%, preferably more than 12%, advantageously more than 14%, based on the fiber mass.

For the production of a pulp of annual plants with a yield of at least 70% or with a lignin content of at least 8% used according to the invention amount of chemicals for the first inventive method at least 7%, in each case based on the aufzuschließende otro mass of annual plants. The quality of the pulp produced shows the best results with a chemical use of up to 30% based on otro annual plants. It is preferred to add between 10% and 27.5%, more preferably between 10% and 20%, of chemicals, based on the otro annual plants used. An optimum use of chemicals has proved to be optimal, which is preferably between 10% and 15%.

Setting a specific pH is by no means required for the first method of the invention. Only if, for example, special properties of the pulps (particularly high whiteness, a certain ratio of breaking lengths and tear resistance) 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 first method according to the invention, irrespective 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. SO2 is mentioned here as representative of the above-mentioned acidic component. So it can be used instead of SO2 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 relationship alkaline component: SO 2 in a range of 4: 1 to 1.6: 1 is well suited to carry out the first method according to the invention and to achieve fibers with high strength properties. A customary, particularly suitable range is between 2: 1 and 1.6: 1. The adaptation of the proportional components takes place depending on the raw material to be digested and the respectively selected process control (digestion temperature, digestion time, impregnation).

The object underlying the invention is also achieved with a second process for the production of pulp from lignocellulosic raw material with the steps:

Preparation of a chemical solution containing less than 20% sulphite (calculated as Na SO3), in each case based on the otro amount of annual plants used, mixing the chemical solution with the wood in a predefined liquor ratio,

Heating the chemical solution and the wood to a temperature above room temperature and then either (1st alternative) removing free-flowing chemical solution and - digesting the annual plants in the vapor phase or (2nd alternative)

Digest the annual plants in the presence of the liquid phase chemical solution and separate the free flowing chemical solution and the annual plants.

The method according to the invention is based on the fact that a minimum of chemicals is used for the production of high-yield fibers. Despite the low use of chemicals, the process according to the invention yields fibers with good yield and excellent strength properties. Thus, for annual plant fiber with a lignin content of more than 8%, which are produced by the second process according to the invention, at grinding degrees of only 20 ⁰ SR values of more than 4.5 km, but also tear lengths of more than 5 km and more measured as 6 km. This achieves the desired high level of strength. In the first method according to the invention, it is believed that the quality of the high yield pulp of annual plants produced there is due to the high chemical input of more than 5% (calculated as NaOH). However, tests have shown that a pulp with the same qualities can certainly also be produced if smaller amounts of sulfite are used and if the use of alkali, eg. B. of NaOH or Na2CO3 is omitted. The demand for sulfite in the second method according to the invention can be reduced by 10% to 50%, in most cases by 20% to 40%, usually by 25% to 35%, compared to the first method.

This is a significant advance on the one hand achieved in the process costs. On the other hand, the second method of the invention works much more environmentally friendly, because a total of a minimum of chemicals is used to produce a particularly high quality and versatile fiber. In addition, only a small and therefore particularly economical and environmentally friendly chemical reprocessing is required to complete the cycle of this process. Which of the two methods of the invention is used depends on the raw material to be digested and on the requirements of the pulp to be produced.

The second method according to the invention is used according to an advantageous embodiment for the production of high-yield fibers from annual plants. These high strength values are not yet known for pulp from annual plants with a lignin content of more than 8%. However, the high strength level can also be maintained for fibers with an even higher lignin content. The method according to the invention is also suitable for the production of fibrous substances from annual plants with a lignin content of more than 10%, preferably more than 12%, advantageously more than 14%, based on the fiber mass.

The advantages described above are fully applicable to high yield pulps of annual plants prepared by one of the methods of the present invention. It is to be regarded as an extraordinary advantage of the method according to the invention that the described strength values are already at extremely low levels Grinding levels are achieved, as they were previously unavailable for high-yield fibers in conjunction with high strength values. Plant fibers made from year old show prior art at freenesses of 20 ⁰ SR an unacceptable level of strength. Known pulps have hitherto yielded fibers at these low levels of milling which have not exhibited sufficient binding power and which accordingly have not provided sufficient strength properties for an economical use of such fibers.

By contrast, the fibrous materials produced by the processes according to the invention already have at break levels in the range of 20 ^° SR tear lengths of more than 4.5 km and tear strengths of more than 45 cN, based on a sheet weight of 100 g / m ² . These low levels of grinding are also achieved with a low specific requirement of milling energy lower than 250 kWh / t of pulp. The realization that the high strength level is achieved even at low grindings 20 ⁰ SR and below, is an essential part of the invention.

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 can be added. 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. If high amounts of sulfite are used in the first process according to the invention, it is possible to dispense with the use of an alkaline component, because even without the addition of alkaline components, a high pH is established which promotes the digestion.

To adjust the pH and to support the delignification, an acidic and / or an alkaline component can be added for the first process according to the invention. The alkaline component is usually sodium hydroxide (NaOH) is used. However, it is also possible to use carbonates, in particular sodium carbonate. The information on chemical quantities of the first invention Digestion process in this document, e.g. As for the total use of chemicals or for the distribution of the sulfite component and the alkaline component, unless otherwise stated, each calculated and reported as sodium hydroxide (NaOH). The information on chemical quantities of the second method according to the invention in this document are calculated and reported as sodium sulfite.

As the acidic component, acids can be added for the first process according to the invention 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 regarded as an independent inventive achievement for both processes according to the invention to have recognized the advantages of using a quinone component for the high-yield digestion according to the invention. Quinone components, particularly anthraquinone, have heretofore been used in the manufacture of pulps with minimal lignin content to prevent unwanted attack on the carbohydrates towards the end of the digestion. By adding quinone components it is possible to continue the digestion of annual plants until almost complete degradation of the lignin. It has been found to be an unprecedented, unexpected property of quinone components that significantly increase the speed of lignin degradation in the production of high yield pulps. The duration of the digestion can z. B. in the production of annual plant fiber by more than half, depending on digestion conditions shortened by more than three quarters. This remarkable effect is achieved with minimal use of quinone. It is expedient to use z. B. anthraquinone between 0.005% and 0.5%, advantageously 0.025-0.2% anthraquinone, particularly advantageously 0.025-0.1% anthraquinone used. Use of anthraquinone of up to 1% also provides the desired effect. A use of more than 3% anthraquinone is usually uneconomical.

From single or several of the aforementioned chemicals, a chemical solution is prepared for the process according to the invention. Mostly an aqueous solution stated. Optionally, the use or addition of organic solvents may be provided. Alcohol, especially methanol and ethanol, in combination with water, result in particularly effective chemical solutions for the production of high-quality high-yield fibers. The mixing ratio of water and alcohol can be optimized for the respective raw material in a few experiments.

The processes according to the invention can be carried out in a wide pH range. The ratio of alkaline component to acidic component or the use of an acidic or an alkaline component can be adjusted in the first method according to the invention so that at the beginning of the process, a pH between 5.5 and 11, preferably between 5.5 and 10 , is more preferably adjusted between 7.5 and 8.5. The more alkaline pH's between 8 and 11, which are advantageous for the processes of the invention, also favor the effect of the quinone moiety. The methods of the invention are tolerant in pH; In particular, in the second method according to the invention, no or few chemicals are required for the pH adjustment. This has a favorable effect on the costs of chemicals.

Without further addition of acid or alkaline component, at the end of the digestion, a pH of between 5.5 and 10, usually between 7.5 and 8.5 in the free-flowing chemical solution and the dissolved organic constituents, by the digestion liquefied. Among the dissolved organic components are mainly lignosulfonates.

The liquor ratio, ie the ratio of the amount of otro annual plants to the chemical solution, is set between 1: 1.5 and 1: 6 for both processes. A liquor ratio of 1: 3 to 1: 5 is preferred. In this range, a good and simple mixing and impregnation of the material to be digested is ensured. For annual plants, a liquor ratio of 1: 4 is preferred.

The mixing or impregnation of the annual plant chips is preferably carried out at elevated temperatures. Heating of wood chips and chemicals - _I4 -

solution to up to 170 ⁰ C, preferably up to 150 ⁰ C, more preferably up to 130 ⁰ C leads to a rapid and uniform digestion of the annual plants. For the mixing or impregnation of the chips, a period of time of up to 30 minutes, preferably of up to 60 minutes, particularly preferably of up to 90 minutes, is advantageous. The optimum time depends, among other things, on the amount of chemicals and the liquor ratio and the type of digestion (liquid or vapor phase).

The digestion of the mixed with the chemical solution or impregnated lignocellulosic material is preferably carried out at temperatures between 120 ⁰ C and 190 ⁰ C, preferably between 150 ⁰ C and 180 ⁰ C. For most annual plants are digestion temperatures between 155 ⁰ C and 170 ⁰ C is set. Higher or lower temperatures can be set, but in this temperature range, the energy expenditure for heating up and accelerating the digestion are in an economic relationship to one another. Higher temperatures can also have a negative effect on the strength and whiteness of the fibers. The pressure generated by the high temperatures can be easily absorbed by appropriate design of the digester. Usually, the duration of the heating is only a few minutes, usually up to 30 minutes, advantageously up to 10 minutes, in particular when heated by means of steam. The duration of the heating can take up to 90 minutes, preferably up to 60 minutes, z. B. when it is digested in the liquid phase and the chemical solution is to be heated together with the wood chips.

The duration of the digestion is chosen primarily depending on the desired fibrous properties. The duration of the digestion can be shortened to up to 2 minutes, z. B. in the case of a vapor phase digestion of annual plants with low lignin content. But it can also be up to 180 minutes, if z. B. the digestion temperature low and the natural lignin content of aufzuschließenden annual plants is high. Even if the initial pH of the digestion is in the neutral range, a long digestion time may be required. Preferably, the digestion time is up to 90 minutes. Particularly preferably, the digestion time is up to 60 minutes, advantageously up to 30 minutes. A digestion time of up to 60 minutes is particularly suitable for annual plants with low lignin content. The use of a quinone component, in particular anthraquinone, allows a reduction of the digestion time to up to 25% of the time required without the addition of anthraquinone. If the use of quinone components is omitted, the digestion time is extended by more than one hour, for example from 45 minutes to 180 minutes, for comparable digestion results.

According to an advantageous embodiment of 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 according to the first inventive method with high chemical use of more than 5% for annual plants, as proposed according to the first method of the invention, initially appears uneconomical. Experiments have shown, however, that only some of the chemicals are consumed during the partial digestion of the lignocellulosic material. The majority of the chemicals are discharged without being used, either before digestion (vapor phase digestion) or after digestion (digestion in the liquid phase). The actual consumption of chemicals is below the amounts used in the digestion solution.

The consumption of chemicals for both inventively proposed methods is determined as the amount of chemicals - based on the originally used amount of chemicals - after removing or separating the chemical solution and, if necessary, the detection of chemical solution, after defibering or in conjunction with a detection the chemical solution is measured. The consumption of chemicals depends on the absolute amount of chemicals used for digestion, based on the otro mass of annual plants to be digested. The higher the use of digestion chemicals, the lower the direct sales of chemicals. When using 27.5% of chemicals based on otro annual crop mass for the first inventive method, for example, only about 30% of the chemicals used are consumed. However, when 15% of chemicals are used per year for otro plants, 60% of the chemicals used are used - l6 -

consumed as could be demonstrated in laboratory experiments. The consumption of chemicals for the first process according to the invention is 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, according to a preferred embodiment of the process during digestion, which is used at the beginning of the digestion.

The chemical consumption for producing one ton of pulp is about 6% to 14% sulfite and / or sulfide component and possibly alkaline and / or acidic component and possibly quinone component based on otro pulp (deciduous and coniferous wood ). According to the invention, this quantity of chemicals is sufficient according to the first proposed method in order to produce a pulp having the predetermined properties. However, in order to ensure a uniform process result and possibly to obtain special, desired pulp properties, it may prove useful according to the first method of the invention to use higher amounts of chemicals for the digestion, z. As the above mentioned up to 30% chemicals based on otro annual plant mass.

The use of these amounts of chemicals at the beginning of the digestion shows advantageous effect in the first process according to the invention, since the fibers obtained in this way have hitherto unavailable properties, in particular high strength properties and high degrees of whiteness. In particular, no digestion process is currently available that produces high strength pulps over a broad pH spectrum from the neutral to the alkaline range. It has proven to be particularly economically attractive that the fibrous materials produced according to the invention are to be ground to predetermined degrees of grinding with much lower energy requirements than known fibrous materials from annual plants. In addition, they develop the high strengths even at unusually low grinding degrees of 20 ⁰ SR.

Excess chemicals are present in both inventive processes after mixing and impregnating the annual plants with the chemical solution or after digestion in the free-flowing liquid. This excess is deducted before digestion (1st alternative) or after digestion (2nd alternative). According to an advantageous embodiment of the method, the composition of the - Y] -

collected chemical solution and then adjusted to a predetermined composition for re-use to produce fibers. The chemical solution that is removed before or after the digestion of annual plants no longer has the initial composition. At least some of the chemicals used for digestion have - as described above - penetrated into the material to be digested and / or has been consumed in the digestion. The unused chemicals can easily be used again for the next digestion. However, it is proposed for both methods of the invention to first determine the composition of the removed chemical solution and then the consumed proportions of z. As sulfite, alkaline component, quinone component or water or alcohol to supplement to restore the predetermined composition for the next digestion. This supplementary step is also called strengthening.

It is to be regarded as a considerable advantage of this measure that the chemical solution contains no or only very few substances, especially when removed before digestion, but also when removed after digestion, which is the next time the recovered chemical solution is used again Disruption proves to be annoying. The first method according to the invention, which is aimed at providing an oversupply of digestion chemicals during the impregnation, can thus be extremely economical despite the initially uneconomic approach of high use of chemicals, because removal or separation and intensification The chemical solution can be carried out easily and inexpensively.

The processes according to the invention are specifically controlled so that only as little as possible of the starting material used is broken down or dissolved. The aim is to produce a pulp which has at least 4% lignin based on the otro pulp, preferably of at least 5% lignin, more preferably of at least 6% lignin, advantageously of at least 7% lignin.

The yield of the inventive method is at least 70%, preferably more than 75%, advantageously more than 80%, in each case based on the used Annual plants. This yield correlates with the above-mentioned lignin content of the pulp. The original lignin content of the annual plants is specific to the species. The loss of yield in the present process is predominantly a loss of lignin. In the case of nonspecific digestion processes, the proportion of carbohydrates is markedly increased; B. because digestion chemicals in an undesirable manner also bring cellulose or hemicelluloses in solution.

A further, advantageous measure is to remove after defibering and optionally grinding the lignocellulosic material, the remaining chemical solution and feed it to a further use. This reuse may include two aspects for both methods in a preferred embodiment. On the one hand, the decomposed during the partial digestion or dissolved in organic material, mainly lignin, continue to be used. It is burned, for example, to gain process energy. Or it is prepared to be used elsewhere. On the other hand, the used and unused chemicals are reprocessed so that they can be used for a renewed, partial digestion of lignocellulosic material. This includes the treatment of used chemicals.

According to a particularly preferred variant of the method according to the invention, the chemical solution used is used extremely efficiently. After defibering and optionally grinding, the pulp is washed to displace the chemical solution as much as possible through water. The filtrate produced in this washing or displacement process contains considerable amounts of chemical solution and organic material. According to the invention, this filtrate is supplied to the removed or separated chemical solution before the chemical solution is fortified and fed to the next digestion. The chemicals and organic components contained in the filtrate do not disturb the digestion. To the extent that they still contribute to the delignification during the next digestion, their content is recorded in the chemical solution and taken into account in determining the amount of chemicals required for this digestion. The further contained in the filtrate chemicals behave inert during the pending digestion. They do not bother. The organic constituents contained in the filtrate are also inert. They will continue to be used after the next digestion in the treatment of the chemical solution, either to generate process energy or otherwise.

It is considered to be particularly advantageous that less filtrate water and fewer chemicals are used for digestion by this filtrate. At the same time a maximum of dissolved organic material is detected. This improved use of the dissolved organic material also improves the economy of the process according to the invention.

In the following, ways of producing and essential properties of the fibrous material according to the invention are explained in more detail by means of exemplary embodiments.

The properties of the fibers were recorded and measured according to the following standards:

The yield was calculated by weighing the raw material used and the pulp obtained after the digestion or bleaching, in each case dried at 105 ^° C. to constant weight (otro).

The lignin content was determined as Klason lignin according to TAPPI T 222 om-98. The acid-soluble lignin was determined according to TAPPI UM 250 The whiteness was determined by preparing the test sheets according to Zellcheming leaflet V / 19/63, measured according to SCAN C 11:75 with a Datacolor elrepho 450 x photometer; the whiteness is given in percent according to ISO standard 2470.

The opacity was determined according to the specifications of Zellcheming-MerkblattVI / 1/66. - The paper technology properties were determined on test sheets, which were prepared according to Zellcheming leaflet V / 8/76. Density was determined according to Zellcheming Regulation V / 11/57. Tear length was determined according to Zellcheming Regulation V / 12/57. The tear resistance was determined according to DIN 53 128 Elmendorf. It is given for a leaf with a leaf weight of 100 g / m ² .

- The degree of grinding was recorded according to Zellcheming leaflet V / 3/62.

Tensile, Tear and Burst Index were determined according to TAPPI 220 sp-96. All percentages in this document are by weight unless otherwise stated.

First method according to the invention Example 1 - Digestion in the liquid phase

Bagasses-chips are alley after steaming (30 minutes with saturated steam at 105 ⁰ C) with a sodium sulphite digestion solution at a liquor ratio of Ba: digestion solution 1: 3 are added. The total use of chemicals was 27.5% based on otro bagasse chips. The pH at the beginning of the digestion was adjusted to pH 8.5 to 9.5.

The impregnated with chemical solution-bagasse chips were heated over a period of 90 minutes at 170 ⁰ C and digested at this maximum temperature for 30 minutes.

Subsequently, the free-flowing liquid was removed by centrifugation, collected and analyzed and strengthened in an arrangement for recycling unconsumed liquid and thus provided for the next digestion.

The open-minded bagasse wood chips were shredded. Aliquots of the pulp so produced were ground for different lengths to determine the strength at different degrees of grinding. The energy required to shred the partially digested bagasse chips was less than 300 kWh / t of pulp.

Example 2

Bagasse woodchips are impregnated with 27.5% chemical additive at a liquor ratio of wood: chemical solution = 1: 5 at 120 ⁰ C in the vapor phase for 120 minutes. The chemicals used are sulfite and 0.1% anthraquinone. At the beginning of the impregnation, a pH of 9.4 sets. After impregnation, the chemical solution is removed.

The chips impregnated with the chemical solution are heated to 170 ^° C. with steam in about 5 minutes. This vapor phase at 170 ⁰ C is about 15-20 minutes held. then the steam is released and within 30 seconds, the digester is cooled to 100 ⁰ C, and it is set to ambient pressure. The wood chips are removed from the stove and shredded. Partial quantities of the bagasse pulp so produced are ground and the ground portions and pulp properties are determined for the ground portions.

Second Inventive Process Example 1 - Digestion in the Liquid Phase

Bagasse wood chips are after a damping (30 minutes with saturated steam at 105 ⁰ C) with a sodium sulfite digestion solution at a liquor ratio of wood: digestion solution 1: 3 added. The total use of chemicals was 15% calculated as sodium sulfite, based on otro bagasse wood chips.

The impregnated with chemical solution-bagasse chips were heated over a period of 90 minutes at 170 ⁰ C and digested at this maximum temperature for 30 minutes. The initial pH was in the range of pH 8.0 to 9.5.

Subsequently, the free-flowing liquid was removed by centrifugation, collected and analyzed in an arrangement for recycling unused liquid and fortified and thus provided for the next digestion. Intensifying means that the specified sulphite concentration is adjusted again by the addition of fresh or recycled sulphite for the next digestion. The chemical consumption in this first digestion is 82%.

The yield is 79.2% based on otro pulp. The breaking length was measured at 16 ⁰ SR with 4.5 km, the Tear index at 7.0 mN * m ² / g. The whiteness was determined after digestion at 41% ISO. Example 2

Bagasse woodchips are impregnated with 23.6% sulphite at a liquor ratio of wood: chemical solution = 1: 5 at 120 ^° C. in the vapor phase for 120 minutes. The chemicals used are sulfite and 0.1% anthraquinone. At the beginning of the impregnation, a pH of 9.4 sets. After impregnation, the chemical solution is removed.

The chips impregnated with the chemical solution are heated to 170 ^° C. with steam in about 5 minutes. This vapor phase at 170 ⁰ C is held for 20 minutes. Then the steam is released and within 30 seconds, the cooker is cooled to 100 ⁰ C, and it sets ambient pressure. The wood chips are removed from the stove and shredded. Partial quantities of the bagasse pulp so produced are ground and the grindings and pulp properties are determined for the ground portions.

At 16 ^° SR, 5 km tenacity and 102 cN / 100 g / m ² paper weight were measured. The whiteness was determined to be 42.6% ISO and the yield was 78.9%.

Claims

claims

1. Lignocellulosic pulp of annual plants with a tearing length of more than 4.5 km at 20 ⁰ SR and a lignin content of at least 8% based on the otro pulp in the unbleached state.

2. Pulp according to claim 1, characterized in that the lignin content of the unbleached pulp is at least 10%, preferably at least 12% and advantageously at least 14% of the otro pulp.

3. Pulp according to claim 1, characterized in that the breaking length is more than 5 km, preferably more than 6 km, more preferably more than 7 km.

4. Pulp according to claim 1, characterized in that it has a tear resistance, which is at a sheet weight of 100 g / m ² at least 45 cN at 20 ⁰ SR.

5. Fiber according to claim 1, characterized in that the unbleached pulp has a whiteness of at least 35% ISO.

6. Lignocellulosic pulp of annual plants with a tearing length of more than 4.5 km at 20 ⁰ SR and a lignin content of at least 7% based on the otro pulp in the bleached state.

7. Pulp according to claim 6, characterized in that the pulp having a lignin content of more than 7% based on the otro pulp after bleaching a whiteness of at least 60% ISO.

8. A pulp according to claim 6, characterized in that the bleached pulp has a whiteness of more than 65% ISO, preferably of more than 70% ISO.

9. Pulp according to claim 7, characterized in that the bleached pulp at 20 ⁰ SR has a breaking length of more than 5 km, preferably more than 6.5 km, advantageously more than 7.5 km.

10. Pulp according to claim 7, characterized in that the bleached pulp having a lignin content of more than 7% at 20 ⁰ SR has a tear strength of more than 45 cN.

11. A method for producing pulp from annual plants with a lignin content of at least 8% based on the otro fiber mass, comprising the steps

- Make a chemical solution with more than 5% chemicals (calculated as NaOH), in each case based on the otro amount of annual plants

Mixing the chemical solution with the annual plants in a predetermined liquor ratio; heating the chemical solution and the annual plants to a temperature above room temperature and then

- either (1st alternative)

Removal of free-flowing chemical solution and digestion of annual plants in the vapor phase - or (2nd alternative)

Digesting annual plants in liquid phase and

Separating the free-flowing chemical solution and the annual plants.

12. A method for producing pulp from lignocellulosic raw material with the steps

Make a chemical solution with less than 20% sulfite (calculated as NaSO 3) based on the amount of lignocellulosic raw material. Mix the chemical solution with wood in a given liquor ratio - heat the chemical solution and the wood to a temperature

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 liquid phase and

Separate the free-flowing chemical solution and the wood.

13. The method according to claim 11 or 12, characterized in that a fiber with a content of at least 8% lignin, preferably at least 10% lignin, advantageously at least 12% lignin, more preferably at least 14% lignin based on otro pulp is produced.

14. The method according to claim 11 or 12, characterized in that for the preparation of the chemical solution sulfites and sulfides, used singly or in mixture.

15. The method according to claim 11, characterized in that for the production of

Chemical solution is used an acidic and / or an alkaline component, in particular an acid, sulfur dioxide, sodium hydroxide and / or a carbonate.

16. The method according to claim 11, characterized in that for digestion an alkaline component and an acidic component, in particular SO2 are used, wherein the ratio of alkaline component: SO2 in a range of 4: 1 to 1.6: 1, preferably to 2 : 1 is set.

17. The method according to claim 14, characterized in that for the preparation of the chemical solution of sodium, potassium, magnesium and / or Ammoniumsulfϊte be used.

18. The method according to claim 11 or 12, characterized in that for the preparation of the chemical solution, a quinone component is used.

19. The method according to claim 11, characterized in that the digestion 10% chemicals or more, preferably 12% chemicals or more, especially preferably 15% chemicals or more are used.

20. Process according to claim 11 or 12, characterized in that the process is carried out at a pH of between 5.5 and 11, preferably between 5.5 and 10, more preferably between 7.5 and 8.5.

21. The method according to claim 11 or 12, characterized in that a liquor ratio annual plants: chemical solution between 1: 1.5 ^and d 1: 1, preferably between 1: 3 and 1: 5 is set.

22. The method according to claim 11 or 12, characterized in that the heating of the chemical solution and the annual plants up to 170 ⁰ C, preferably up to 150 ⁰ C, advantageously up to 130 ⁰ C.

23. The method according to claim 11 or 12, characterized in that the heating of the annual plants and optionally the chemical solution takes up to 90 minutes, preferably up to 60 minutes, advantageously up to 30 minutes, particularly advantageously up to 10 minutes.

24. The method according to claim 11 or 12, characterized in that the digestion of the annual plants at temperatures between 120 ⁰ C and 190 ⁰ C, preferably at temperatures between 150 ⁰ C and 180 ⁰ C, particularly preferably at temperatures between 160 ⁰ C and 170 ⁰ C is performed.

25. The method according to claim 11 or 12, characterized in that the digestion of the annual plants up to 180 minutes, preferably up to 90 minutes, more preferably up to 60 minutes, advantageously up to 30 minutes, more advantageously takes up to 2 minutes.

26. The method according to claim 25, characterized in that the duration of the opening is selected depending on the liquor ratio.

27. The method according to claim 11, characterized in that the consumption of Che- during digestion up to 80%, preferably up to 40%, particularly preferably up to 40%, advantageously up to 20%, particularly advantageously up to 10% of the chemical use at the beginning of the digestion.

28. The method according to claim 12, characterized in that for digesting lignocellulosic raw material with a lignin content of more than 14% based on otro raw material up to 13% sulfite based on otro lignocellulosischen raw material are consumed that for digesting lignocellulosic raw material with a lignin content from 12% to 25% based on otro raw material up to 10% sulphite are consumed, and that for digesting lignocellulosic raw material with a lignin content of up to 10% based on otro raw material less than 10% sulphite are consumed, but at least 5 % Sulfite can be used.

29. The method according to claim 12, characterized in that the consumption of sulfite during the digestion up to 80%, preferably up to 60%, particularly preferably up to 40% of the sulfite used at the beginning of the digestion.

30. The method according to at least one of the preceding claims, characterized in that for the preparation of the chemical solution up to 75 wt .-% of the sulfite from the recycling of already used for the digestion of the chemical solution is used, and that at least 25 wt .-% of the sulfite fresh be added.

31. The method according to claim 30, characterized in that for the preparation of the chemical solution up to 50 wt .-% of the sulfite from the recycling of already used for the digestion of the chemical solution is used, and that at least 50 wt .-% of the sulfite are added fresh.

32. The method according to claim 30 or 31, characterized in that in the preparation of the chemical solution fresh sulfite is added in the following amounts: up to 13% in lignocellulosic raw material of more than 25% lignin based on otro raw material, up to 10% in lignocellulosic Raw material with a lignin content of 20% to 25% based on raw otro material and less than 10% on lignocellulosic raw material with a lignin content of less than 20%, each calculated as NaSO 3 based on otro lignocellulosisch.es raw material.

33. The method according to claim 11 or 12, characterized in that the composition of the removed or separated chemical solution is detected and then adjusted for re-use for the production of fibers to a predetermined composition.

34. The method according to claim 11 or 12, characterized in that after the defibering and optionally grinding the digested lignocellulosic material released chemical solution is removed and a further use is supplied.

35. The method of claim 11, 12 or 34, characterized in that by circulating the digestion solution, the solids content of this recirculated digestion solution by up to 5%, preferably increased by up to 10%, more preferably by up to 15%.

36. The method of claim 11, 12, 34 or 35, characterized in that the recycled digestion solution has up to 1.5 MJ / kg higher calorific value than a freshly prepared digestion solution.