WO1980000159A1

WO1980000159A1 - Process for attacking a cellulosic plant material by means of amino organic compounds

Info

Publication number: WO1980000159A1
Application number: PCT/DE1979/000065
Authority: WO
Inventors: R Derra; C Derra
Original assignee: Isega Ind Studien; R Derra; C Derra
Priority date: 1978-06-30
Filing date: 1979-06-27
Publication date: 1980-02-07
Also published as: BE877381A; IT1166892B; IT7923989A0; EP0016108A1; NL7904996A; DE2828740A1

Abstract

The process comprises the attacking of a cellulosic plant material, by separation of binding substances, such as lignin, by using amino organic compounds. In most of the known processes which use aqueous solutions or dispersions of the attacking agent, the materials to be separated form with the attacking agent reaction products, in big quantities; too much attacking agent is then used and the binding substances may hardly be used subsequently. Further, excess of waste waters occurs. Here is proposed an attack by extraction, without any addition of water, by means of aromatic compounds, substantially insoluble in water, amino cyclo-alkylated compounds and amino acylated compounds, wherein the reactions of the attacking agent with the binding substances may be suppressed by means of stabilizers. The process is used for the preparation of cellulose, wood pulp and other cellulosic products. In particular, pulps of good solidity and readily bleached may be prepared.

Description

Process for the digestion of cellulose-containing plant material with organic amino compounds,

Technical field

The invention relates to a process for the digestion of cellulose-containing, plant material for the production of cellulose, cellulose and other cellulose-containing products by removing non-cellulose-containing binding substances, such as lignin, resins and waxes from the plant material using organic amino compounds with one or more free or substituted, reactive amino groups.

Underlying state of the art

Digestion of wood and other vegetable raw materials by known processes for the production of cellulose is generally carried out in an aqueous medium. Acidic, alkaline and also neutral processes are known, in which inorganic compounds are generally used for the digestion. In these known processes, the binding substance, such as lignin, resins or waxes, which largely surrounds the cellulose of the plant fiber, is either conducted in water-soluble forms or dispersed in water, either by substitution reactions or by hydrolytic cleavage. In addition to the desired product, there are therefore reaction products between these binding substances and the digestion chemicals. These reaction products such as lignin condensates u. The like. are only accessible to a very limited extent for further use. U.S. Patents 2,192,202 and 2,218,479 to Peterson and Wise are already known to use aliphatic amino compounds for pulp production. The processes described in these patents essentially use water-soluble amino compounds, including in connection with inorganic disintegrants. In these known processes, reactions with the disintegrant also take place to a considerable extent, which on the one hand lead to consumption of disintegrant and on the other hand to reaction products of the binding substances of the plant material, which make further use more difficult.

In the above-mentioned digestion processes, not only the aqueous digestion medium itself with the dissolved binding substances contained therein from the vegetable raw material is obtained as a waste product, considerable amounts of water are also required in order to completely wash out the binding substances in solution or suspension from the cellulose-containing product. Large amounts of waste products and water containing contaminants are produced here. It is among other things common in the widely used sulfate process, to concentrate the leaching, to burn the thickened binding substance for energy generation, to burn and to largely recover the digestion chemicals, however, residual contaminations of the wastewater cannot be completely avoided despite the recovery process and contamination of the atmosphere also occurs during the sulfate process resulting from the digestion, malodorous substances. Air pollution does not generally occur to the extent of the acid sulfite process and the known neutral digestion process as does the sulfate process, but the sewage and recovery problems are usually even more difficult to solve here.

Further, significant wastewater pollution occurs in the process that generally follows the digestion process Bleach the pulp. Compounds containing chlorine are largely used for this purpose, the residues of which cannot be removed from the bleaching effluent with economic means.

The invention has for its object to provide a method for the digestion of cellulose-containing, vegetable material, in which at least the digestion itself and the separation of the binding substances from the fibrous product take place without the use of water, in particular in the manufacture of one for paper production suitable pulp the inherent highest possible pest properties in the plant material should be preserved for the pulp produced and nevertheless a product is produced which is easily bleachable and thus can be brought to the required degrees of whiteness solely by bleaching agents based on oxygen, so that the secondary wastewater pollution is also caused by chlorine-containing bleaching chemicals can be avoided.

An additional object of the invention is to remove the binding substances, namely the lignin, the resins and the waxes, from the vegetable raw material in an unreacted form, as a result of which they can be used as valuable raw materials for further useful applications. A largely non-existent chemical reaction between the disintegrant and the binding substances is further sought for the reason to lose as little disintegrating agent as possible through chemical reaction with the binding substances, or to avoid complex reverse reactions for releasing the disintegrating agent, and to achieve the most complete recovery possible . Disclosure of the invention

The invention consists in a process for the digestion of cellulose-containing plant material for the production of cellulose, cellulose and other cellulose-containing products by removing non-cellulose-containing binding substances, such as lignin, resins and waxes, from the plant material using organic amino compounds with one or more free ones or substituted, reactive amino groups, the process being characterized in that extraction is carried out using one or more aromatic amino compounds, cycloalkyl amino compounds and / or acyl amino compounds without the addition of water.

Since these disintegrants have to penetrate into the plant material in order to dissolve the binding substances, practically only amino compounds of the type mentioned come into being which are liquid under normal conditions, or those solid porms whose melting point is not higher than 150 ° C. In the digestion, which is usually carried out at elevated temperature, the latter compounds are converted into the liquid state.

The amino compounds used according to the invention expediently belong to the general formula

described compounds in which R _{a can be} a cycloalkyl radical of the formals C _n H _2n-1 , an aryl radical or an acyl radical and R _b or R _{c can be} hydrogen or an alkyl radical. Correspondingly, compounds with more than one amino group are also suitable. Suitable compounds which contain an acyl radical or a cycloalkyl radical are, for example, dimethylformamide, cyclohexylamine and cyclohexyldiamine.

Particularly surprising results in solving the problem were achieved when using generally water-insoluble aromatic amines, in which the hydrogen atoms of the amino groups can also be substituted by aliphatic, cyclic and / or aromatic radicals, in which one or more K- Hydrogen atoms can be replaced by oxygen, nitrogen, sulfur and / or phosphorus groups. Aniline, toluidine (O-toluidine) and dimethylaniline may be mentioned as exemplary compounds. To improve the impregnation of the plant material, aliphatic amines can also be mixed to a certain extent with the compounds mentioned.

The selection of the compounds to be used in practice is essentially determined by economic considerations. In general, those amino compounds of interest which may arise in the chemical industry as waste products and compounds of simpler structure, the basic radical or substituents of which for the hydrogen atoms of the amino groups contain only relatively few carbon atoms, are of interest. In addition, amino compounds of lower molecular weight generally have a better ability to penetrate into the vegetable material to be digested.

Best way to carry out the invention

Although the binding substances can be extracted from vegetable raw material using the amino compounds mentioned, in principle also at room temperature and atmospheric pressure, as long as the extraction times are long enough, it is the same as with other digestion processes expedient to work at elevated temperature and pressure, primarily to accelerate the digestion process. For the digestion process itself, temperatures in the range between 200 and 250 C have proven to be particularly useful. If the process is carried out in several stages, pre-impregnation can also be carried out at lower temperatures of around 100 - 150 ° C. It is also expedient to work under pressure, so that the vapor pressure corresponding to the driven temperature is established. This is in any case necessary when using amino compounds whose boiling point is below the driven temperature.

The extraction can take place both in the liquid phase and in the vapor phase of the disintegrant. Depending on the technical conditions, the work can be carried out batchwise or continuously. In a continuous process, extraction in countercurrent has proven to be advantageous.

Depending on the type of plant material to be broken down, whether wood or waste from annual plants, and the type of its preparation, longer or shorter exposure times at different temperatures may be required. The process conditions depend on whether the starting material is in the form of wood chips, chips, chaff or sawdust.

The organic amino compounds can be used individually or in mixtures with one another for the digestion. The aromatic amines, especially aniline and toluidine, are particularly advantageous in that they react very little with the vegetable matter or its components. As a result of their water-insolubility, however, there are certain difficulties in achieving sufficient penetration of the vegetable raw material, especially if this still has a considerable moisture content. It has It has therefore proven to be expedient in many cases to carry out the process according to the invention by largely pre-drying the vegetable material before the actual digestion.

However, better impregnation can also be achieved by using a water-soluble, aliphatic amine such as diethanolamine in addition to an aromatic amine according to the invention, such as aniline or toluidine. The water-soluble amine first penetrates the raw material and absorbs the remaining plant water contained in it. With the water-soluble amine as the carrier, the second amine intended for more effective digestion, for example with a higher boiling point and stronger extracting action, preferably a water-insoluble aromatic amine, can penetrate into the plant material.

If a direct mixture of two such amines is used in a one-step process, the water-soluble amine should make up about 20-40% by weight, preferably about 30% by weight, of the total disintegrant. The proportion of the less soluble water-soluble amine for the pre-impregnation can be reduced if the process is carried out in two stages. In a first step, the plant material is advantageously impregnated with about 10% by weight, based on total disintegrant, of a first water-soluble amine, to which the remaining 90% by weight in the form of another, preferably water-insoluble, aromatic amine is then added in a second process step without first removing the first amine.

The two-stage procedure also offers the advantage that it is possible to work with a lower temperature in the first or impregnation stage. this leads to an energy saving in the overall digestion. Impregnation temperatures between 100 and 150 ° C, preferably 130 ° C, have proven to be suitable, while the intrinsic digestion in the second stage can take place at temperatures between 210 and 240 ° C.

The digestion times under the temperature and pressure conditions given as preferred are generally between 2 and 4 hours for the production of a paper pulp. In the two-stage process, the dwell time in each of the stages is approximately 1-2 hours. With a corresponding variation of the digestion conditions, high yield pulp and semi-pulp can also be obtained with the process according to the invention with very good results.

For the economy of the process according to the invention, but also for the reduction of waste products, it is necessary that the digestion used is largely recovered. becomes. For this purpose, after the digestion process, the disintegrant containing the binding substances is separated from the pulp products in a manner known per se by filtration, pressing and / or centrifuging. Solvent displacement can also be carried out, but this is only expedient if the or one of the amines used for the digestion is used which is not loaded with binding substances, so that no further material has to be introduced into the recovery for the digestion agent . The digestion center is expediently separated from the binding substances by redistillation. However, other known separation processes are possible as long as no water has to be introduced into the circuit for the digestion itself and the washing out of the binding substances from the fibrous product. In certain applications, the quantitative removal of the amino compounds used as disintegrants from the end product can be a problem. For reasons of health damage, pulp for papermaking in particular must no longer contain any aromatic amines. In principle, the pulping agents claimed according to the invention or their residues can be easily removed from the end product of the fiber by neutral organic solvents. Examples of such solvents are ketones, aldehydes or alcohols. If such solvents are used to a lesser extent, they can be recovered separately in the course of redistillation of the disintegrant. Low residual levels of disintegrants can also be removed with inorganic or organic acids or their salts.

Another possibility for removing a residual aromatic amine content from the end product is to treat the fibrous material with nitrous acid in order to convert the amines into azo compounds, which can then be removed using an organic solvent or as a leuco compound. Any solvents used for this purpose can also be recovered in the redistillation of the disintegrant.

The quality of the end product obtained by the process according to the invention is largely independent of the fact whether the removal of the binding substances takes place by pure extraction or whether a reaction between the disintegrant and the binding substances also takes place at the same time. While the use of water-soluble amines to a not insignificant extent also results in reactions with, for example, the lignin, which can even lead to water-soluble lignin compounds in the disintegrant, the aromatic amines have the decisive advantage that they react little with the vegetable substance. If the digesting agent does not react chemically, the lignin and the other substances to be removed are obtained in native form. These represent an important, potential raw material for the manufacture of other products.

However, even when aromatic amines are used, the removal of the binding substances is not completely reaction-free. It was therefore, as already pointed out at the beginning, a further object of the invention to prevent a reaction between the disintegrant and the constituents of the plant material as far as possible by means of suitable additives. It has been found that this can be done successfully if substances are added to the disintegrant that stabilize its active amino groups and that water, etc. is eliminated. prevent from the lignin and cellulose. Organic acids and their derivatives, organic sulfonic acids, acid salts or phosphate esters can be used successfully as such stabilizers. Examples of suitable acidic salts are monosubstituted sulfates of ethylsulfonic acid. Those which contain organic radicals with 1-18 carbon atoms can be used as the phosphate ester. Organic acids, such as stearic acid or adipic acid, can only be used with limited success. By contrast, derivatives of cinnamic acid, but in particular derivatives of propionic acid, have proven to be very advantageous. These stabilizers can generally not be recovered and recycled and remain with the removed binding substances.

The amount of stabilizers added can be up to 8% by weight, based on the digesting agent. When propionic acid derivatives are used, 3-6% by weight, preferably 4-5% by weight, are generally used. The following stabilizers used with success are mentioned as examples:

Stabilizer I: zinc propionate and propionic acid propyl ester in the ratio 1: 1 additionally 1% n-octadecyl-β- (4'-hydroxy -3 ', 5'-di-tert-butylphenyl) propionate based on the amount of stabilizer.

Stabilizer II:

70% - ethyl cinnamate and 30% - butane-σ6-sulfonic acid additionally 0.5% n-octadecyl-ß- (4 ^, -hydroxy-3 ', 5'-di-tert-butyl-phenyl) propionate based on the amount of stabilizer.

Commercial usability

As can be seen in more detail from the examples given further below, the wood digestion with the amino compounds indicated leads to pulps with an extraordinarily high level of pest development and relatively high starting whiteness. If the digestion process is carried out appropriately, the lignin is almost completely removed from the plant material, and in contrast to most of the known digestion processes, the hemicelluloses remain in the fiber material. The almost complete lignin release leads to the relatively high initial whiteness and has the consequence that subsequent bleaching does not have to be a lignin solution, but only a lightening of the cellulose-containing material, which can generally be achieved without chlorine-containing bleaching agents, using only oxygen-based bleaching agents. In this way, the pulp strengths obtained in the digestion process can be obtained and wastewater pollution by bleaching agents containing chlorine is avoided.

With a suitable procedure, the pentosans are also in the structure in the digestion process according to the invention retention of the cellulose composite and have an effect on strengthening paper manufacturing. Basic materials for further processing by acetylation, xanthogenation and nitration can also be obtained from the pulp obtained by further treatment.

Overall, the yield of pulp in the process according to the invention is in the order of up to 70% delignified and resin-free fiber. The degradation of the fiber strength is low, so that papers with the highest strength values can be produced. The physical measured values are in the order of magnitude of kraft paper, and even better if the conditions for drawing down are appropriately managed. Both wood and annual plants or waste products from the annual plants are suitable, e.g. Bagasse, for the claimed digestion. Since subsequent bleaching only serves to lighten the pasers during the practically complete removal of the lignin and not to remove the residual lignin or for subsequent digestion, the amount of chemicals used is considerably less and the strength-reducing process in the bleaching is reduced. The pasers are extracted almost undestroyed and undegraded. The initial grinding degrees are 13-15 ° SR (degree Schopper-Riegler). The grinding process itself happens very quickly. At the same time, the strength increases suddenly and reaches values of 10,000 - 12,000 m tear length for softwood.

All known processes can be used for bleaching. However, the digestion process is particularly suitable in connection with an oxygen bleach, for example a bleach with hydrogen peroxide. A degree of whiteness of 71 - 73 ° is achieved with a 2% use in one step.

The following examples are intended to explain the invention in more detail: Embodiments

a. Spruce wood chips are mixed in a standing cooker with solvent circulation with aniline and 4% stabilizer I based on dry wood and inside

Heated to 220 ° 0 for 70 min. This temperature is held for 3 hours. A pulp is then obtained with a yield of 64.1% and 14.5 ° SR. With a degree of grinding of 44º SR, the rip length is 8,920 m.

b. Wood chips from pine are mixed in a rotary cooker with aniline and 5% Stabilizer II based on dry wood and heated to 220 ° C. After a cooking time of 4 hours, a yield of 63.7% results in a cellulose with 13 ° SR. To

It grows for 25 minutes to 46 ° and 8,780 m tear length.

c. Pine chips are mixed in a rotary cooker with o-toluidine (without stabilizer), heated to 226 ° C at a pressure of 14 atm and a cooking time of 115 min. A pulp with 14 ° SR is obtained. After a grinding time of 25 minutes, the grinding degree increases to 49 ° SR and results in a breaking length of 9,200 m.

d. Spruce chips are cooked in a standing cooker in a mixture of diethanolamine and dirnethylaniline in a ratio of 1: 1 and 6% Stabilizer II at 240 ° C for 2 hours. The fully digested pulp gives a yield of 63.9% with a freeness of 23 ° SR.

e. Pine chips are heated in dimethylformamide and 3 f ° stabilizer I at 218 ° C for 2 hours. The result is a pulp with a yield of 55.8% and 13.5 ° SR. After 25% grinding time, a grinding degree of 67 ° SR and a length of 11,900 m is reached. f. Spruce chips are cooked for 1 1/2 hours at 230 ° C with cyclohexylamine and 3% Stabilizer II. The pulp yield is 61.1% and 16 ° SR. The tear length is 9,840 m at 38 ° SR.

G. Spruce chips are treated in a rotary cooker for 100 min at 130 ° C with diethylamine and 5% stabilizer II and after separation for 120 min with o-toluidine at 210 ° C. A pulp is obtained with 57.7% yield and 12 ° SR. After 25 min, at 42 ° SR 9,740 m tear length results.

H. Spruce chips are first in the rotary cooker with diethylamine and 5% Stabilizer II for 100 min at 130 ° C and after separation with dimethylformamide for 1 hour

Heated to 218 ° C. The pulp yield is 59.6% at 13.5 ° SR. At 36 ° SR, the rip length is 9,480 m.

i. Pine chips are treated with steam at 155 ° C of dimethylformamide and 3% Stabilizer II, after removing the condensate and pressing it results in a pulp of 63.6% yield and 12 ° SR. To

25 min meal, it gives a grinding degree of 63 ° SR and 9,430 m tear length,

k. Pine chips are first heated in a rotary cooker with 10% of the total proportion of the solvent dietha nolamin at 80 ° C for 30 min and then 90% of the total proportion of the solvent with o-toluidine and 4% stabilizer I preheated to 80 C, and then the mixture is added Treated at 210 ° C for 1 hour. The pulp yield is 61.4% and the freeness is 13 ° SR. The tear length is 10,700.

Claims

1. Process for the digestion of cellulose-containing, plant material for the production of cellulose, cellulose and other cellulose-containing products by removing non-cellulose-containing binding substances, such as lignin, resins and waxes, from the plant material using organic amino compounds with one or more free or substituted ones, reactive.amino groups, characterized in that an extraction is carried out using one or more aromatic amino compounds, cycloalkyl amino compounds and / or acyl amino compounds without the addition of water.

2. The method according to claim 1, characterized in that amino compounds are used which are liquid in the normal state and / or solid amino compounds whose melting points are not higher than 150 ° C.

3. The method according to claim 1, characterized in that aromatic amino compounds are used, the substituents for the hydrogen atoms of the amino group (s) are aliphatic, cyclic and / or aromatic radicals, in which one or more carbon atoms by oxygen, nitrogen - Sulfur and / or phosphorus groups can be replaced.

4. The method according to claim 1, characterized in that the amino compounds used to the group of the general formula

Compounds described include, wherein R _{a is} a cyclo alkyl radical of the formula C _n H _2n-1 , an aryl radical or The acyl radical and R or R can be hydrogen or an alkyl radical.

5. The method according to claim 4, characterized in that are used as monoamines for the digestion cyclohexylamine, dimethylformamide, aniline, toluidine or dimethylaniline ver.

6. The method according to claim 1, characterized in that aliphatic amines can be added.

7. The method according to claim 1, characterized in that the extraction takes place at temperatures between 200 and 250 ° C.

8. The method according to claim 1, characterized in that the extraction is carried out under increased pressure of about 10-17 bar.

9. The method according to claim 1, characterized in that the extraction takes place in the vapor phase of the disintegrant.

10. The method according to claim 1, characterized in that the extraction takes place continuously.

11. The method according to claim 10, characterized in that the extraction takes place in countercurrent.

12. The method according to claim 1, characterized in that the extraction is carried out in several stages, the temperature and pressure conditions in the individual stages can be different.

13. The method according to claim 12, characterized in that in a further, following a previous stage, the extraction stage followed by the digesting agent used in the previous extraction stage a further / ^ x> Disintegrant is added without disintegrant being removed at the end of the previous step.

14. The method according to any one of claims 1-13, characterized in that the pure extraction times, depending on the desired degree of digestion and the temperature and pressure conditions, are between 1 and 3 hours.

15. The method according to any one of claims 1-13, characterized in that the disintegrating agent containing the binding substances from the vegetable material is removed from the product by displacement by means of fresh disintegrating agent, filtration, pressing and / or centrifuging, and the disintegrating agent is removed from it contained binding substances are separated and reused in the cycle.

16. The method according to claim 15, characterized in that the separation of the digesting agent or agents from the binding substances is carried out by redistillation.

17. The method according to claim 15, characterized in that the removal of residues of the disintegrant from the

Product is carried out by washing with organic solvents, which can optionally be recovered separately if the disintegrant is redistilled.

18. The method according to claim 15, characterized in that the removal of residues of the digesting agent from the product is carried out by washing with inorganic or organic acids.

19. The method according to claim 15, characterized in that the removal of residues of the disintegrant from the

Product by post-treatment of the product with nitrous acid and thus a transfer of the Amines are carried out in azo compounds which are removed using an organic solvent or as a leuco compound.

20. The method according to any one of claims 1-13, characterized in that the vegetable material is pre-dried before performing the extraction digestion.

21. The method according to any one of claims 1-13, characterized in that stabilizers are added during the extraction digestion, which stabilize the active amino groups of the disintegrating agent and elimination of water and the like. prevent from the lignin and cellulose, and keep the loss of disintegrant caused by side reactions low.

22. Verfahren.nach claim 21, characterized in that as stabilizers organic acids and their

Derivatives, organic sulfonic acids, acid salts or phosphate esters can be used.

23. The method according to claim 22, characterized in that derivatives of propionic acid and cinnamic acid are used as stabilizers.

24. The method according to claim 21, characterized in that up to 8% by weight of stabilizers, based on solubilizer, are used.

25. The method according to claim 23, characterized in that 3 - 6% stabilizers, based on disintegrant, are used.

26. The method according to claim 13, characterized in that a water-soluble amine in a first process step for impregnating the plant material on an aliphatic basis, for example diethanol amine or diethylamine is used, which easily penetrates into the plant material and absorbs the residual water contained in the plant material, and that in a second process step a water-insoluble, aromatic amine, for example aniline or toluidine, is added.

27. The method according to claim 26, characterized in that, based on the total disintegrating agent, the water-soluble amine and the water-insoluble aromatic amine are used in a weight ratio of about 1: 9.

28. The method according to claim 26 or 27, characterized in that the first process stage is carried out at a reduced impregnation temperature between about 120 and 150 ° C and the second stage at a digestion temperature between about 200 and 250 ° C.