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 cellulose-containing Material.
• Pulp is understood to be a cellulose pulp that is required for the production of cellulose. This pulp is then used to make paper or cardboard, for example.
• the pulp-producing industry is finding it increasingly difficult to meet the requirements and requirements relating to environmental protection. In addition, it is no longer permitted, for example in Germany after the environmental regulations of 1990, to use traditional pulp production processes such as the sulfate process.
• sulfur-containing disintegrants in order to extract the lignin that acts as a composite from the cellulose-containing material, only the sulfite process is used in Germany.
• the so-called Acetosolv process developed which the digestion liquid contains at least 50% by weight of acetic acid and additionally a small amount of hydrochloric acid. After this information the pulp thus obtained with sodium hydroxide solution and optionally also with organic Solvents washed to make the lignin more or less complete to remove.
• 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-A-0 325 891 has therefore disclosed an improvement in this acetosolve process.
• the improvement essentially consists in that the pulp is no longer washed with sodium hydroxide solution after digestion, but with a C 1-3 carboxylic acid or a mixture of such acids and that the subsequent bleaching is also carried out in the acidic medium with additional Use of hydrogen peroxide or ozone is carried out.
• a carboxylic acid ester such as butyl acetate can also be used as the solvent.
• the C 1-3 carboxylic acid used for washing the pulp can subsequently be used again as a digestion liquid.
• WO-A-82/01902 also discloses a process for producing a pulp from cellulose-containing material using formic acid.
• GB-A-850 367 teaches the use of formic acid in the production of cellulose.
• WO-A-86/05529 has disclosed a process for producing bleached pulp from cellulose-containing material, which is generally also referred to as the Milox process.
• the digestion is carried out in a peroxyformyl, peroxyacetic, peroxypropion or peroxybutyric acid medium, the peroxyacid being obtained by mixing the respective acid with a relatively high proportion of hydrogen peroxide and then carrying out the digestion process.
• This digestion is followed by bleaching of the pulp, which is carried out in an alkaline solution to which 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.
• the method according to the invention as claimed in claim 1 is used, for example, 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 hydrogen peroxide is slowly added in a 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.
• Digestion solution is understood to mean the sum of the solvent, the cellulose-containing material and components, such as lignin and sugar, that 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 combined in one Concentration range between about 60 to 99% by weight can be used.
• the use of 100% formic acid is not cheap, because at least one certain percentage of water in the manufacture of the pulp, i.e. in the digestion process should be present.
• the cooking time can be a period of can be given in about 30 to 120 minutes, depending on the cellulose-containing used Material.
• the predetermined amount of hydrogen peroxide can be about 1 to 3 % By weight, preferably 1 to 2% by weight, particularly preferably 1% by weight on the total weight of cellulosic material and solvent be. It is particularly advantageous here that only a very small amount of added hydrogen peroxide is necessary, which is sufficient to the one hand Requirements for the whiteness of the pulp so produced for the production of paper and which, on the other hand, is sufficient to withstand the temperature of the To keep the digestion solution approximately at the boiling point of the solvent, without supplying additional energy in the form of heat. So that can good properties of the paper made from the pulp can be combined with a minimal expenditure of energy.
• the method according to the invention can further be modified in this regard be that in addition to the solvent a gas such as air, oxygen, ozone or a comparable gas or a mixture of two or more of these Gases is introduced.
• a gas such as air, oxygen, ozone or a comparable gas or a mixture of two or more of these Gases is introduced.
• the oxidative power of these gases is used, which increases lignin degradation and thus whiteness, as well as the kappa number lowers.
• the required digestion time is also reduced.
• the pulp can be easily removed after the cooking time Sieves are separated from the solvent.
• This will sieve understood in the broadest sense, i.e. a separation by a suitable one Membrane, a filter or a frit is also possible, but then that Disconnection can happen continuously.
• the pulp so screened can then be washed with water and / or formic acid. Especially when Washing with formic acid becomes the remaining lignin, which is already out the cellulose-containing material is dissolved out. By opening the pulp by means of a stirrer can still flush this out be promoted.
• 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 at this temperature there is an optimum of performic acid.
• 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 can be used as a cellulose-containing material. and / or corn leaves or stems are used. Both materials, in particular Elephant grass can be easily unlocked. It can even the addition of hydrogen peroxide to the solvent can be dispensed with. For example, when using 99% formic acid and one Cooking time of one hour reaches a kappa number of 4.7.
• a particular advantage of the method according to the invention is, however, that as cellulosic material basically annual plants, especially cereal straw, can be used. This is especially true for papermaking important, because so far almost exclusively as a cellulosic material Wood is used. Worldwide there are over 200 million a year Tons of paper used. The demand continues to grow. The deforestation large forest areas to cover the need for cellulose-containing material but brings significant environmental problems such as climate change and habitat destruction of flora and fauna with them. Where, if any, Reforestation is usually only rapidly growing Monocultures created, which in turn are very pest-prone and ecological are not useful. In addition, developing countries or countries of the so-called "third world" an increasing need for paper for the determine various purposes.
• the process according to the invention is also based on the cellulose-containing processes which have been customary to date Materials such as hardwood or softwood can be used. You know that it is generally more difficult with these materials, an adequate one To provide the whiteness of the paper made from the pulp, it then lends itself, according to the particularly preferred embodiment to proceed and the inventive method while reducing the Repeat cooking temperature and optional extension of cooking time.
• Another aspect of the present invention relates to that from pulp the process of the invention lignin. This is after the Recycling of formic acid used as a solvent by simple Distillation obtained from the distillation residue by precipitation in water. This precipitation of the water-insoluble lignin at the same time makes it of the water-soluble sugars also present in the residue separated.
• the pulp thus obtained is used for pulp production for example for the paper industry or for the production of Cardboard used.
• manufactured pulp can be used and used wherever pulp is used Starting material for a product is required. For example Chemical cellulose or any other product from regenerated or chemical modified cellulose from the pulp.
• Lignin which by the inventive method is available can be safely processed as it is contains no sulfur or chlorine, as is the case in the prior art known methods for producing a pulp would mostly be the case.
• the Isolated lignin can be used, for example, as a construction material, in particular as Starting material for pressboard, medium density fibreboard or as filler be used if it decomposes with excess 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 be used as a raw material for the production of flavorings such as vanillin or mulled wine flavor.
• 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 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 hydrogen peroxide of the concentration given below is slowly 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 is recovered with the formic acid from the digestion by simple distillation. Again on a laboratory scale, a Liebig distillation apparatus and a 300 mm column were used. The formic acid used can largely be recovered here. Usually in a percentage of over 95%.
• 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 also 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 described manufacturing possibilities of a pulp can still be achieved be improved that a gas is used in addition to the digestion like air, oxygen, ozone or the like, for its oxidative power to exploit in the digestion. Also a mixture of two or more the gases mentioned can be used.
• the digestion process described above or one of its variants is then carried out so that additionally into the reaction vessel from below the appropriate gas type or a gas mixture using a wide nozzle is initiated. This can be done continuously or discontinuously.
• the escaping gas can then be used again or disposed of in an environmentally friendly manner using the known methods become.
• an excess of oxalic acid is added to the lignin and melted or according to another process variant in saturated formic acid solution cooked and then evaporated with cellulose fibers.
• a waterproof black-brown mass that can be used as a filler or after Type of pressboard or fiberboard can be used.

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• Paper (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)

Applications Claiming Priority (3)

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

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