Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C3/00—Pulping cellulose-containing materials
  • D21C3/006—Pulping cellulose-containing materials with compounds not otherwise provided for
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C3/00—Pulping cellulose-containing materials
  • D21C3/003—Pulping cellulose-containing materials with organic compounds

Definitions

• the invention relates to a method for producing a pulp from cellulosic material, the pulp itself and its use.
• Pulp is understood to be a cellulose pulp that is required for the production of cellulose. Paper or cardboard, for example, is then produced from this pulp.
• the pulp-producing industry is finding it increasingly difficult to meet the requirements and requirements relating to environmental protection. In addition, it is e.g. no longer permitted in Germany after the environmental requirements of 1990 to use traditional methods for pulping, such as the sulfate method.
• sulfur-containing disintegrating agents to dissolve the lignin, which acts as a composite, from the cellulose-containing material, only the sulfite process is used in Germany.
• the so-called Acetosolv process emerged, in which the digestion liquid contains at least 50% by weight of acetic acid and additionally a small proportion of hydrochloric acid. After this digestion, the pulp thus obtained is washed with sodium hydroxide solution and optionally also with organic solvents in order to remove the lignin more or less completely.
• a disadvantage of this process is the relatively high acetic acid consumption and the use of sodium hydroxide solution and optionally organic solvents for washing the pulp.
• the pulp obtained in this way is regularly bleached in a subsequent step in order to achieve kappa numbers of at least below 25.
• downstream bleaching by means of a peroxide is provided, with a relatively high consumption of this bleaching agent being disadvantageous.
• EP 0 250 422 B1 has disclosed a process for producing bleached pulp from cellulose-containing material, which is also generally referred to as the Milox process.
• the digestion is carried out in a peroxyformyl, peroxyacetic, peroxypropion or peroxybutyric acid medium, the peroxo acid being obtained by mixing the respective acid with a relatively high proportion of hydrogen peroxide and then carrying out the digestion process.
• This pulping is followed by bleaching of the pulp, which is carried out in alkaline solution, the hydrogen peroxide has been added.
• the disadvantage of this process is again the use of an alkaline solution, such as sodium hydroxide solution, and the high proportion of hydrogen peroxide required.
• the present invention has for its object to provide a method for producing a pulp from cellulose-containing material that works as environmentally friendly as possible and at the same time extremely economical and efficient.
• a preferred embodiment of the method according to the invention is used when the cellulose-containing material used is not so easy to digest. This is the case, for example, with hardwood or coniferous wood, but also with grain straw, depending on the intended use of the pulp obtained from it.
• the cellulosic material is mixed with formic acid and water and heated slightly under reflux by an external energy source. Then a precisely predetermined amount of hydrogen peroxide is slowly added in constant dosage.
• Such a procedure has hitherto not been known by any prior art and enables a very economical procedure because the now exothermic reaction itself provides the heat necessary for cooking. This means that after the initial activation, no further external energy supply is required.
• Digestion solution is understood to mean the sum of the solvent, the cellulose-containing material and constituents, such as lignin and sugar, which may have been extracted therefrom. Furthermore, in the reaction according to the preferred embodiment it is advantageous that the equilibrium in the reaction of the formation of the peracid from formic acid and hydrogen peroxide is continuously shifted to the peracid side by the continuous addition of the hydrogen peroxide.
• aqueous formic acid can be used in a concentration range between approximately 60 to 99% by weight.
• 100% formic acid is not beneficial since at least a certain percentage of water is used in the manufacture of the pulp, i.e. should be present in the shooting process.
• a time period of about 30 to 120 minutes can be specified as the cooking time, depending on the cellulosic material used.
• the predetermined amount of hydrogen peroxide can be approximately 1 to 3% by weight, preferably 1 to 2% by weight, particularly preferably 1% by weight, based on the total weight of the cellulose-containing material and solvent. It is particularly advantageous that only a very small amount of added hydrogen peroxide is necessary, which is sufficient on the one hand to meet the requirements for the whiteness of the pulp thus produced for the production of paper and on the other hand is sufficient to approximately the temperature of the pulping solution to maintain the boiling point of the solvent without supplying additional energy in the form of heat. Good properties of the paper produced from the pulp according to the invention can thus be combined with a minimal expenditure of energy. It has proven advantageous to keep the liquid to material ratio in the range from 20: 1 to 25: 1.
• the method according to the invention can also be modified such that a gas such as air, oxygen, ozone or a comparable gas or a mixture of two or more of these gases is additionally introduced into the solvent.
• a gas such as air, oxygen, ozone or a comparable gas or a mixture of two or more of these gases is additionally introduced into the solvent.
• the oxidative power of these gases is used to increase lignin degradation and thus whiteness, and to lower the kappa number.
• the required digestion time is also reduced.
• the pulp can be separated from the solvent by simple sieving after the cooking time has ended.
• Sieving is understood in the broadest sense, i.e. separation by means of a suitable membrane, a filter or a frit is also possible, in which case the separation can take place continuously.
• the pulp so screened can then be washed with water and / or formic acid. Especially when washing with formic acid, the remaining lignin, which has already been removed from the cellulose-containing material, is washed out. By flushing the pulp with a stirrer, this flushing out can still be promoted.
• a method for producing a pulp from cellulose-containing material which is suitable, for example, for producing paper with a sufficient degree of whiteness (e.g. kappa number ⁇ 10) in a one-step process with minimal energy expenditure.
• the cooking temperature is reduced.
• Aqueous formic acid is then used as the solvent, to which hydrogen peroxide, as already described above, is added.
• the reduced cooking temperature can be around 70 to 80 ° C.
• the cooking temperature is preferably 70 ° C., since an optimum of performic acid is present at this temperature.
• the cooking time can be extended to up to 5 hours to achieve a higher degree of whiteness.
• the cooking time is then preferably about 3 hours, because it was found that after this time the pulp no longer brightened up appreciably. It has also proven advantageous to increase the liquid-to-material ratio to over 25: 1.
• elephant grass (Miscanthus) and / or corn leaves or stems can be used as the cellulose-containing material. Both materials, in particular elephant grass, can be digested very well. It can even the addition of hydrogen peroxide to the solvent can be dispensed with. For example, when using 99% formic acid and a cooking time of one hour, a kappa number of 4.7 was achieved.
• a particular advantage of the process according to the invention is that basically annual plants, in particular grain straw, can be used as the cellulose-containing material. This is particularly important for paper production, since until now wood has been used almost exclusively as the cellulosic material. Worldwide, over 200 million tons of paper are used each year. The demand continues to grow. The deforestation of large forest areas to cover the need for cellulose-containing material brings with it considerable environmental problems, such as climate changes and habitat destruction of flora and fauna. Wherever, if at all, reforestation is carried out, only rapidly growing monocultures are created, which in turn are very susceptible to pests and make no ecological sense. In addition, an increasing need for paper for various purposes can also be found in developing countries or countries of the so-called "third world".
• Wood as a cellulosic material, is usually missing for the usual production.
• the grain straw can serve as a sensible substitute in terms of costs and from an ecological point of view. Straw is often viewed as a nuisance and burned on the fields, which is harmful to the environment.
• Germany alone the total volume of each harvest is around 50 million tons of straw, so there is great potential for cellulosic material. This applies even more to countries such as the USA or Canada, which are known to have huge grain fields.
• the cultivation of simple annual plants can be an opportunity to use difficult soils and in bad climatic conditions. It is possible where the planting of more demanding cereals due to weather or Soil conditions are no longer possible to switch to management by means of simpler annual plants and thus to provide cellulose-containing material for the production of a pulp, which in turn is then used for paper production.
• the method according to the invention can also be applied to the hitherto customary cellulosic materials, such as hardwood or softwood. It is known that " it is generally more difficult with these materials to provide a sufficient degree of whiteness for the paper produced from the pulp, in which case it is advisable to proceed according to the particularly preferred embodiment and to reduce the cooking temperature and the inventive method optionally repeat the extension of the cooking time.
• Another aspect of the present invention relates to the lignin released from the pulp by the method according to the invention. After recycling the formic acid used as solvent, this is obtained by simple distillation from the distillation residue by precipitation in water. As a result of this precipitation of the water-insoluble lignin, it is simultaneously separated from the water-soluble sugars which are also present in the residue.
• the invention also relates to a pulp made of cellulose-containing material which can be obtained by the process according to the invention and optionally according to its preferred or particularly preferred embodiment.
• the invention also relates to the use of the pulp thus obtained for pulp production, for example for the paper industry or for the production of cardboard.
• the pulp produced by the process according to the invention can be used and used wherever pulp is required as a starting material for a product.
• chemical cellulose or another product made from regenerated or chemically modified cellulose can also be produced from the pulp according to the invention.
• the invention also relates to lignin which can be obtained by the process according to the invention.
• This lignin can be safely processed because it does not contain any sulfur or chlorine, as would usually be the case in the prior art processes for producing a pulp.
• the isolated lignin can be used, for example, as a building material, in particular as a starting material for particle board, medium-density fiberboard or as a filler material, if it is decomposed in excess with oxalic acid and either melted or boiled in a saturated formic acid solution and then steamed with cellulose fiber. This creates a waterproof black-brown mass.
• lignin is even more diverse. So it can serve as a starting material for the production of aroma substances such as vanillin or mulled wine aroma.
• the pulp obtained after washing was washed with aqueous formic acid in such a way that further fresh formic acid was added in a concentration range of 60 to 80% by weight, so as to flush out the remaining lignin.
• a paddle stirrer was then inserted into the reaction vessel and stirred for about 1 minute. This whipping by stirring creates a fiberization of the cellulose dressings and the washing out of the lignin is facilitated.
• the formic acid After the formic acid has been separated off, it is distilled off with the formic acid from the digestion reaction described above by simple distillation. A Liebig distillation apparatus with a 300 mm column is used on a laboratory scale. The formic acid used is largely recovered here.
• the lignin dissolved in the residue can easily be precipitated in water and processed further. Dissolved carbohydrates can be obtained by evaporation. The pulp is washed neutral with water and air-dried. A kappa number of 15 and a yield of 45% were achieved. 2. Making a pulp from corn leaves
• Cereal straw, formic acid and water are transferred into the reaction vessel in accordance with the percentages by weight given below and in accordance with the liquid-to-straw ratio also given there.
• this is again a round bottom flask, combined with a ground thermometer and a dimrotre reflux condenser.
• the reaction mixture is then heated slightly under reflux and then slowly hydrogen peroxide of the concentration given below is added continuously.
• the reaction is exothermic, so that the external energy supply, such as here via a heating pad or a heating plate, can at least initially be reduced and then completely eliminated.
• the digestion time is also given below.
• the pulp is separated from the pulping solution by simple sieving and mixed with further fresh formic acid in a concentration of 60 to 80% by weight, so as to flush out the remaining lignin.
• a paddle stirrer is then inserted into the reaction vessel and stirred for about one minute. This creates a defibrillation of the cellulose dressings and the lignin washout is facilitated.
• the formic acid After the formic acid has been separated off, it is recovered with the formic acid from the digestion by simple distillation. A Liebig distillation apparatus and a 300 mm column were again used for this on a laboratory scale. The formic acid used can largely be won. Usually in a percentage of over 95%.
• Digestion times of 30, 45, 60, 90 and 120 minutes were selected in the experiments. These were combined with formic acid concentrations of 50, 60, 75, 80, 85, 90, 95 and 100%.
• the amount of hydrogen peroxide added was varied between 1% and 2%. It was found that an addition of more than 1% does not bring any appreciable advantage, but only complicates the control of the digestion due to the even more violent exothermic reaction.
• the digestion temperature was always kept at the boiling point of the solvent.
• the liquid-to-straw ratio is referred to as the liquor ratio.
• the test parameters shown indicate optimized production processes, although the optimization in test 3.a) was carried out in such a way that not only was a maximum lignin removal achieved, but the lignin itself should still be obtained in as large a quantity as possible. It has been shown that optimal lignin removal is accompanied by an increased breakdown of the lignin to water solubility. The optimization was therefore carried out in such a way that lignin which had not been broken down or altered as far as possible should be obtained in addition to the lignin-free pulp.
• the straw is treated as stated under 3. After the cooking time has ended, a stirrer is used and the pulp obtained is broken down for about 1 minute. Then the pulping solution is separated from the pulp and further processed without drying.
• the parameters of an experiment for producing a pulp with a repetition step are given below.
• the repetition step is labeled 4.b.).
• Cooking temperature approx. 106 c > C 70-80 ° C
• Cooking temperature approx. 106 ° C 70-80 ° C
• the described production possibilities of a pulp can be further improved by using a gas such as air, oxygen, ozone or the like in addition to the digestion in order to utilize its oxidative power in the digestion.
• a gas such as air, oxygen, ozone or the like
• a mixture of two or more of the gases mentioned can also be used.
• the digestion process described above or one of its variants is then carried out in such a way that the corresponding type of gas or a gas mixture is additionally introduced into the reaction vessel from below by means of a wide nozzle. This can be done continuously or discontinuously.
• the escaping gas can then be used again or be disposed of in an environmentally friendly manner using the already known corresponding methods.
• the lignin is mixed with an excess of oxalic acid and melted or, in another process variant, boiled in saturated formic acid solution and then evaporated with cellulose fibers. This creates a waterproof black-brown mass that can be used as a filler or in the manner of a pressboard or fibreboard.

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• 1995
  • 1995-05-03 DE DE19516151A patent/DE19516151A1/de not_active Withdrawn
• 1996
  • 1996-05-02 US US08/945,345 patent/US6183597B1/en not_active Expired - Fee Related
  • 1996-05-02 CA CA002217987A patent/CA2217987A1/fr not_active Abandoned
  • 1996-05-02 AT AT96914167T patent/ATE215632T1/de not_active IP Right Cessation
  • 1996-05-02 PT PT96914167T patent/PT823948E/pt unknown
  • 1996-05-02 DK DK96914167T patent/DK0823948T3/da active
  • 1996-05-02 EP EP96914167A patent/EP0823948B1/fr not_active Expired - Lifetime
  • 1996-05-02 ES ES96914167T patent/ES2175091T3/es not_active Expired - Lifetime
  • 1996-05-02 JP JP8533002A patent/JP3059998B2/ja not_active Expired - Lifetime
  • 1996-05-02 WO PCT/EP1996/001823 patent/WO1996035013A1/fr active IP Right Grant
  • 1996-05-02 DE DE59609018T patent/DE59609018D1/de not_active Expired - Fee Related
  • 1996-05-02 RU RU97120707A patent/RU2139965C1/ru active
  • 1996-05-02 CN CN96193631A patent/CN1098390C/zh not_active Expired - Fee Related

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