FI60732C - FOERFARANDE FOER DELIGNIFIERING AV LIGNOCELLULOSAMATERIAL - Google Patents

Description

ANNOUNCEMENT / λπ 7 O

JgSA IBJ (11) utläggningsskrift 6U 'C ^ ftateritti issued on 10 03 1982 (¾¾¾ Patent aeddelat V vy (51) Kr.ik.3 / I «.ci.3 D 21 C 3/02, 9/10 FINLAND —FINLAND ( H) Patent application— PatentansAkninf 780889 (22) HakamUplIvI - Anattknlngadag 21.03.78 ^ * (23) Alkupllvt - Glttlfhatadaj 21.03.78 (41) Tullut |

Patent and Registration Office .... .... _ .. , _ . . (44) Date of NShUvIkalpanon and lunar launch. -

Patent- och registerstyrelsen 'Aniökan utlagd och utUkriften pubikerad 30.11.8l (32) (33) (31) Pyritty etuoikeus - Begird priorltet (71) Rauma-Repola Oy, Helsinki, FI; Rauma Factories, 26100 Rauma 10,

Suomi-Finland (FI) (72) Henrik Bruun, Turku, Risto Sjöholm, Bishop's Cross, Lars Gädda,

The present invention relates to a process for the rapid delignification of lignocellulosic material by oxygen-alkali treatment. pulp production or pulp bleaching are as follows: 1. Various coniferous deciduous trees used as raw material in pulp production.

2. Various grasses, straw or other similar lignocellulosic materials.

3. Pulp obtained from various lignocellulosic materials referred to in points 1 and 2 by various commonly used chemical and semi-chemical pre-treatment methods and / or mechanical defibering methods.

4. Pulp obtained from the lignocellulosic materials mentioned in 1 and 2 by means of various commonly used cellulose cooking methods.

5. Pulp obtained from the lignocellulosic materials mentioned in points 1 and 2 in connection with various commonly used bleaching processes.

6. In particular, a lignocellulosic material pretreated by a method similar to or similar to the first stage of oxygen-alkali treatment.

2. Lignocellulosic materials are made into pulp by a variety of methods. The most important of these methods are based on the reaction of sulfur or sulfur-containing compounds with lignin and the consequent delignification.

Of these sulfur-based methods, the most important are sulfate and sulfite methods and their variants. These methods can be used to produce pulp for a wide variety of purposes and, since the pulps produced by these methods can be bleached, the possibilities for use are further increased.

3. When bleaching pulp, chlorine and / or chlorine derivatives such as chlorine dioxide and hypochlorite are most often used. These chemicals react with the residual lignin (lignin remaining in the pulp after pulp cooking) and make the reaction products soluble. The residual lignin in the pulp soup is colored in terms of visual properties (especially in the sulphate process), so that the brightness of the pulp naturally increases when it is removed.

4. Sulfur-based pulp production methods as well as chlorine-based bleaching methods are very widely used. Requirements based on environmental protection and the improvement of working conditions place ever stricter restrictions on sulfur and chlorine (sulfur emissions such as mercaptan, hydrogen sulphide and various sulphides into the atmosphere, as well as sulfur and chlorine emissions, eg chlorinated phenols into water bodies). This fact has led to the development of pulp production and pulp bleaching methods that not only retain the best pulp properties, pulp bleachability and bleached pulp properties comparable to sulphate and sulphite pulps, but are also more environmentally and workplace friendly.

5. Soda-ash or alkali treatment methods enable the production of pulp without sulfur compounds and thus largely meet the requirements of environmental protection and working conditions. Pure alkali treatment as a useful pulping method is only suitable for hardwoods, but the resulting pulp does not have a strength of 3 6073? not comparable to the corresponding pulp obtained by the sulphate process. As a result, efforts have been made to develop alkali treatment applications that would allow softwoods to be used as a raw material and to produce pulp with properties that are largely comparable to or even better than sulphate and sulphite pulp.

6. Oxygen-alkali treatment is one application of alkali treatment, e.g. 895-756, which has been much developed. The two-stage oxygen-alkali treatment, in which the wood raw material (chips) is softened in the first stage by treatment with alkali and heat so that it can be easily defibered and the actual delignification with oxygen and alkali in the second stage, is best known of these variations. This two-step oxygen-alkali process produces pulp which is completely comparable in yield to the pulp obtained by the sulphate process, in some cases even better by the oxygen-alkali process. Instead, the strength properties are clearly inferior in the case of oxygen-alkali pulp. This is largely due to undesired reactions that shorten alkali cellulose molecules. This can be established by analyzing the degree of polymerization of the pulps.

7. The process according to the invention is characterized in that the delignification is selectively accelerated considerably by the in situ formation of singlet oxygen, which is obtained by adding to the treatment solution at the beginning and / or during the treatment 0.01-10% of perborate or peroxide based on the lignocellulosic material. By providing favorable conditions for the formation of singlet oxygen, the selectivity of delignification at the beginning of the treatment can be considerably improved and the delignification substantially accelerated. For the above reasons, the yield when treating the lignocellulosic material as required by the invention will be considerably improved, since the undesired alkali-cleavage reactions of the alkali caused by the shortening of the treatment time do not take place on a similar scale as before. Namely, singlet oxygen has been found to react to a greater extent with lignin containing double bond and phenyl groups than undesirably with cellulose molecules. In this case, the improvement in yield also results in an improvement in the strength properties of the fibers.

11 6 0 7 3 2

The above-mentioned properties which have a positive effect on the delignification of the additives used in connection with the oxygen-alkali treatment will become clear from the following examples.

8. Delignification has been studied by UV microspectrophotometry. The method is based on the fact that the absorption of lignin at a wavelength of 280 nm can be determined from different parts of the cross-sections of wood fibers with a thickness of 1 μm directly, e.g. The determination is carried out in such a way that a narrow UV light beam with a diameter of 1.4 μm moves directly over the fiber wall and the value of the light absorption of lignin in the fiber wall is recorded on a plotter from which the corresponding absorptions of different parts of the wall can be calculated. When determined at a wavelength of 280 nm, which is one of the absorption peaks of lignin in the UV range, the resulting absorption is a measure of the amount of lignin in that part of the fiber. The correct absorbance value is obtained by relating the measured value of the sample to the measured values of the absorptions of known filters. By monitoring the change in absorption during the treatment, it is possible to calculate the degree of delignification of the pulp from the results obtained. Samples taken at specified times during processing are prepared by cutting 1.0 μm thick sections of fibers deep-cooled to -60 to -80 ° C without coatings with an ultramicrotome.

9. The process of the present invention, which can produce pulp in higher yields in a shorter time and which also provides significant energy savings and is particularly environmentally and workplace friendly, treats lignocellulosic material under the following conditions: Treatment in a closed reactor at time conditions based on the weight of dry lignocellulosic material, at a temperature of 100-180 ° C. The active ingredients in the treatment are not only alkali but also oxygen, O2 pressure 0.1-2.0 MPa and perborate or peroxide 0.01-10% based on dry lignocellulosic material. The active ingredient may be added to the treatment solution at the beginning or during the treatment. Both additives 5 60732 can also be used together in a similar manner. The ratio of dry lignocellulosic material to water should be in the range of 1-20%.

10. The following examples are intended to illustrate the delignification improvements obtained with oxygen-alkali treatment with additives found above. Pine industrial chips were treated by a generally known pretreatment method according to a two-stage oxygen-alkali cooking. The obtained pretreated chips were further defibered with a Sprout-Waldron unilateral plate sprayer, the pulp obtained from which served as a test material.

The treatment according to the method was performed with 0.5 l of group cooking in the above test material under the following conditions:

temperature 130 ° C

material pre-treated pine industrial chips alkali 8% NaOH in relation to the weight of the dry lignocellulosic material oxygen pressure 0.7 MPa wood / water 1/15 amount of additive 2% by weight of the dry lignocellulosic material weight of lignin at the beginning of the experiments 25-3% EXAMPLE 1

The results obtained using Na-perborate as an additive are shown below A ordinary oxygen-alkali treatment B "" +2/2 perborate

Delignification yield of pulps (%) processing time (min) degree (%) __ spring tree summer tree spring tree summer tree

ABABAB AB AB

0 0 0 0 100 100 0 0 0 0 20 20 20 20 93.0 98.5 23 15 31 19 * 10 40 40 40 86.5 92.0 54 35 66 42 60 60 60 60 80.0 83.0 108 74 111 79 6 60732 EXAMPLE 2

The results obtained using peroxide as an additive are shown below A ordinary oxygen-alkali treatment B "" + 2% peroxide

Delignification yield of pulps {%) processing time (min) degree (%) _ spring tree summer tree yield (%) spring tree summer tree

ABABAB AB AB

0 0 0 0 100 100 0 0 0 0 20 20 20 20 93.0 98.5 23 13 31 13 40 40 40 40 86.5 94.0 54 31 66 31 60 60 60 60 80.0 83.0 108 6l 111 63 EXAMPLE 3

The results obtained from the test runs at different perborate concentrations are as follows: perborate (%) yield {%) kappa 1 45.8 29 2 45.8 29 3 · 45.1 26 4 45.0 26 5 44.9 25

Claims (5)

7 6 O 7 X 9 Claims A process for delignifying a lignocellulosic material by means of an oxygen-alkali treatment, characterized in that the delignification is selectively accelerated considerably by the formation of singlet oxygen in statu nendicendi obtained by adding to the treatment solution at the beginning and / or during treatment -sidia. Process according to Claim 1, characterized in that the delignification of the cellulose pulps obtained from the various chemical treatments is continued by said process. Process according to Claim 1 or 2, characterized in that accelerating delignification is applied in connection with known bleaching processes. Process according to one of the preceding claims, characterized in that the chemical or chemical mixture which considerably accelerates delignification is added in stages during the treatment. Process according to one of the preceding claims, characterized in that the delignified pulp is further treated with conventional chemicals.