EP2180095B1 - Production method for bleached organic fibre materials, use of a bleaching agent for bleached organic fibre materials and bleached fibre materials - Google Patents

Description

The invention relates to a production method for bleached wood fibers according to the preamble of claim 1, the use of a bleaching mixture and bleached wood pulp according to the preamble of claim 9.

For the production of bleached organic fiber materials, such as bleached wood fibers or wood pulp, a Bieichmischung, also called bleaching or bleaching solution, in which inter alia hydrogen peroxide is present, is often used. In this case, there is often the problem that hydrogen peroxide is decomposed due to heavy metal ions, which can be introduced into the bleach by different means. Hydrogen peroxide is catalytically decomposed in the presence of heavy metal ions. In addition, additional reagents are often added to the bleach, resulting in higher costs. Hydrogen peroxide acts oxidatively.

DE 43 40 043 A1 describes a use of nitrogen-containing complexing agents in the bleaching of wood pulps. It describes the use of special nitrogen-containing complexing agents in pulp bleaching with hydrogen peroxide. Here are the alkaline Wasserstoffperoxidblelche, which is usually provided with sodium water glass, alkali and standard metal complexing agents, novel, biodegradable more complexing agents added. These complexing agents result in high costs.

DE 196 14 587 A1 describes a method and a bleaching solution for bleaching cellulosic fibers. The method is used to activate aqueous, alkaline and / or alcoholic alkaline bleaching solutions which release hydrogen peroxide and are used under oxygen pressure and / or nitrogen pressure to bleach cellulosic primary or secondary pulps for papermaking or bleaching of chemical pulps. To activate the peroxide compound, a combination consisting of isomeric diazaphenanthrenes, for example phenanthrolines, and / or individually or as a mixture, a combination consisting of dipyridyls is used individually or as a mixture. It is also possible to use a mixture with a combination of polyalpha-hydroxyacrylate and / or phosphonates and / or polyaminocarboxylates or oxi- or polyoxl compounds having 2 to 7 carbon atoms in the carbon chain. Such mixtures are complicated and time consuming and costly.

DE 31 10 882 C2 describes a method and apparatus for bleaching chemically produced pulps with ozone. Here, a method and an apparatus for bleaching chemically produced pulp with ozone in connection with a refinement process will be described.

US 6 056 853 A discloses a process for paraffin bleaching pulp using only MgO as the alkaline reagent. Particularly advantageous particle sizes were identified as MgO particles with a d ₅₀ value of between 5 and 500 μm. The particle surface has a range between 20-60 m ² / g.

U.S. 5,571,378 discloses a process for high pH metal ion chelation of pulp.

In promoting and eliminating harmful metal ions and organic extractives from delignification , bleaching is carried out to pulp, preferably with a kraft pulp.

EP 0 595 386 discloses a process for bleaching lignocellulosic pulp which comprises treating the pulp in the presence of a magnesium compound, wherein the pulp is washed and subsequently bleached with a peroxide-containing compound.

In the bleaching of organic fiber materials are often additionally alkaline substances such. For example, sodium hydroxide solution. This caustic soda solution used for bleaching has the disadvantage that it is relatively expensive. Although caustic soda contributes to a higher bleaching effect, but due to the high alkalinity also organic substances are increasingly brought into the bleaching solution. These lead to a significantly increased COD (Chemical Oxygen Demand) value in the wastewater.

Thus, it is an object of the invention to provide a production process for bleached wood fibers and the use of a bleaching mixture for this purpose, which are inexpensive and less harmful to the environment.

This object is achieved according to the features of patent claims 1, 6 and 9.

Surprisingly, it has been found that the use of sub-microscale and nanoscale Ca and / or Mg compound particles in such bleaching solutions leads, on the one hand, to favorably produced Ca and Mg compound particles and thus to a low-cost production process and, on the other hand can be obtained by saving the caustic soda a little umweitschädliches method and a bleaching mixture for this purpose with high bleaching effect. The total cost can even be reduced.

Such Ca or Mg compound particles are relatively inexpensive to produce and can be produced with little contamination, ie with a small proportion of heavy metal ions, which has a catalytically degrading effect on the containing peroxide or hydrogen peroxide. As a result of the catalytically degrading effect of heavy metal ions on the peroxide which has taken place so far, this was no longer available in the actual bleaching process. This resulted in higher manufacturing costs.

As is known, Ca compounds have a higher pH and thus achieve a stronger bleaching effect for the organic fiber materials. However, Ca ions also tend to form insoluble compounds such. As oxalates, which can be deposited in the manufacturing process adversely within the bleaching mixture. This is avoided by the use of sparingly soluble Ca-compound particles in a variant of the invention in which only Mg ions contribute to the bleaching action.

According to the invention, the bleaching mixture for use in a production process for bleached wood fibers or wood pulp, hydrogen peroxide, alkaline or alkaline reacting materials, and - based on particle diameter - submicroscale or nanoscale Ca and / or Mg compound particles for bleaching the organic fiber materials.

Advantageously, the submicroscale particles have a diameter of 0.1-0.3 μm.

The nanoscale particles may advantageously have a diameter of less than 100 nm.

Both the submicron-scale and the nanoscale particles are preferably formed in an oval and / or spherical shape. They are therefore not platelet or fibrous in shape.

The specified particle diameters refer to a measurement as d50 by means of laser diffraction, eg Cilas apparatus, Quantachrome, REM (scanning electron microscopy) or TEM (transmission electron microscopy). Preference is given to submicron-scale or nanosize compound particles of the compounds CaO, Ca (OH) ₂ . CaCO ₃ , MgO, Mg (OH) ₂ and mixtures thereof. This can be done in any ratio and in the form of secondary products, powder and aqueous suspension.

As raw materials for the production of the Mg and / or Ca compound particles, preference is given to using natural, comparatively pure carbonates, such as, for example, MgCa (CO ₃ ) ₂ (dolomite). Alternatively, synthetic preferably chemically pure materials can be used for this purpose.

As an alternative to the natural Ca and / or Mg compound mentioned here as raw material, it is also possible to use all other naturally occurring or synthetic mixed compounds of this or related type as the basis for Ca and / or Mg compound particles and thus for the bleaching mixture. An example of this is, for example, huntite, which is a Ca-Mg-CO ₃ mixed compound.

Likewise, all mixtures or compounds of the proposed here Ca or Mg compounds and their derivatives can be mixed with all other suitable Ca or Mg or other compounds to obtain a modification, which ultimately leads to a similar result in the function, if appropriate to amplify, mitigate or delay the desired properties. This applies in particular to compounds of the second main group of the periodic table or other divalent metal ions.

Bleached wood pulps, especially wood pulp, can be bleached by such a bleach mixture. This is advantageous to use in the paper industry. The bleaching of such wood fibers usually takes place oxidatively with the aid of hydrogen peroxide. In addition, water glass, alkaline or alkaline materials and complexing agents may be present.

The Ca and / or Mg compound particles used according to the invention for the bleaching mixture can be prepared both as a powder and in the form of a suspension.

Due to the use of submicroscale and nanoscale Ca and / or Mg compound particles, it can be achieved that the use of these primary articles results in a very high reactivity and thus bleaching effect within the bleaching mixture, also due to the increased surface fraction due to the multiplicity of particles.

The Ca and / or Mg compound particles are preferably produced in the sub-microscale and nanoscale range by at least partially converting natural carbonates into the oxides by thermal processes. By choosing the appropriate process parameters during the thermal treatment, primary particles become submicron and nanoscale grain sizes receive. By the implementation of these they are in other compounds, eg. As the hydrates, transferred, wherein the grain size of the primary particles practically does not change. This preserves the submicron or nanoscale particle sizes.

With the Ca and / or Mg compound particles and the bleaching mixture associated therewith, it is particularly advantageous for them to be selected by the choice of the parameters of the thermal intermediates Particulate and full calcinate can be selected to suit specific three-phase systems of CaCO _3, MgO and CaO or CaCO _3, Mg (OH) ₂ and Ca (OH) ₂ to achieve the ideal combination of reactivity and deposits or other beneficial properties.

The Ca and Mg products are also inexpensive and chemically highly pure, so that almost no secondary contamination by metal or heavy metal ions takes place and therefore also saves complexing agent and still sufficient quality can be achieved. The high chemical purity of the product is also reflected in the very high whiteness, which brings additional advantages in the production of very light fiber products.

Fig. 1a und 1 b

zeigen REM- Aufnahmen von natürlichem Mg(OH)₂;

Fig. 2a und 2b

zeigen REM- Aufnahmen von synthetischem Mg(OH)₂;

Fig. 3a und 3b

zeigen REM- Aufnahmen von teilkalzinierten bzw. vollkalziniertem Dolomit;

Fig. 4a und 4b

zeigen REM- Aufnahmen von teilkalzinierten bzw. vollkalziniertem Dolomit;

Fig. 5a und 5b

zeigen REM- Aufnahmen von teilkalzinierten bzw. vollkalziniertem Dolomit;

Fig. 6a und 6b

zeigen REM- Aufnahmen von teilkalzinierten bzw. vollkalziniertem Dolomit;

Fig. 7a und 7b

zeigen REM-Aufnahmen von hydratisiertem Dolomit; und

Fig. 8a und 8b

zeigen REM-Aufnahmen von hydratisiertem Dolomit.

It is shown in:

Fig. 1a and 1b

show SEM images of natural Mg (OH) ₂ ;

Fig. 2a and 2b

show SEM images of synthetic Mg (OH) ₂ ;

Fig. 3a and 3b

show SEM images of partially calcined or fully calcined dolomite;

Fig. 4a and 4b

show SEM images of partially calcined or fully calcined dolomite;

Fig. 5a and 5b

show SEM images of partially calcined or fully calcined dolomite;

Fig. 6a and 6b

show SEM images of partially calcined or fully calcined dolomite;

Fig. 7a and 7b

show SEM images of hydrated dolomite; and

Fig. 8a and 8b

show SEM images of hydrated dolomite.

Examples of how they might be present after calcination and hydration in the bleaching mixture. Example 1: Reference 1 (negative example)

Fig. 1a. 1b show SEM images of natural Mg (OH) ₂ .
The Mg (OH) ₂ contains fine, natural particles in a particle size of about 1-3 μm, occasionally also finer.

Example 2: Reference 2 (negative example)

Fig. 2a, 2b show SEM images of synthetic Mg (OH) ₂ .
Synthetic Mg (OH) ₂ shows well-formed crystals. The grain size is about 0.5-1 microns. Isolated units are available.

Example 3: (positive example)

For this purpose, dolomite CaMg (CO ₃ ) _{2 is converted} at elevated temperature in partially to fully calcined dolomite (CaCO ₃ and MgO via a three-phase system CaO, CaCO ₃ and MgO up to CaO and MgO). By choosing the temperature profile shown and the heating time can be submicron or nanoscale MgO and CaCO ₃ (Teilkalzinierung) analogous to the three-phase system to produce MgO and CaO (Vollkalzinat).

Calcination of partial calcinate (CaCO ₃ and MgO):

Table 1. Calcination Partial calcinate (CaCO ₃ and MgO). Area prefers More preferred Even more preferred Temperature, ° C 600-1300 650-1200 700-1000 750-950 Time, min. 0-300 min 0-180 0-90 0-60

Calcination of full calcine (CaO and MgO):

Table 2. Calcination of full calcine (CaO and MgO) Area prefers More preferred Even more preferred Temperature, ° C 750-1450 800-1400 900-1300 1000-1200 Time, min. 0-300 min 0-180 0-90 0-60

Fig. 3a, 3b and 4a, 4b show SEM images of partially calcined or fully calcined dolomite.

In partially calcined dolomite primary particles of MgO and CaCO _{3 can be seen} in a grain size of 50 to 100 nm.

In fully calcined dolomite, the primary particles are also present in a particle size of 50 to 100 nm and consist of CaO and MgO.

Example 4 (positive example)

Nanoscale primary particles in partially calcined to fully calcined dolomite can also be obtained when dolomite is brought to very high temperature within a very short time.

Calcination of partial calcinate:

Table 3. Calcination of partial calcinate. Area prefers More preferred Even more preferred Temperature, ° C 700-1700 800-1650 900-1600 1000-1500 Time, s 0-240 0-180 0-120 0-60

Calcination of full calcine:

Table 4. Calcination of full calcine. Area prefers More preferred Even more preferred Temperature, ° C 700-1700 800-1650 900-1600 1000-1500 Time, s. 0-1200 min 0-900 0-720 0-600

Fig. 5a, 5b and 6a, 6b show SEM images of partially calcined or fully calcined dolomite.

The partially to fully calcined materials obtained in the short-time calcination also contain nanoscale primary particles with a particle size of 50-100 nm.

Example 5 (positive example)

In partially calcined dolomite (from Example 3 or 4), the MgO can be converted by aqueous hydration in submicron or nanoscale Mg (OH) ₂ particles, the size of the CaCO ₃ particles is retained. These particles can then be added to the bleaching mixture. The degree of conversion of MgO to Mg (OH) 2 is> 80% up to> 90% of theory.

hydration

Table 5. Hydration. Area prefers More preferred Even more preferred Suspension, dry matter TS in% 0-99 0-85 0-70 0-65

Fig. 7a, 7b show SEM images of hydrated dolomite from Example 3 and 4. Example 5.

The material contains aggregates and exposed particles. The grain size of the primary particles is about 50-200 nm. These consist of Mg (OH) ₂ and CaCO ₃ .

Example 6 (positive example)

In fully calcined dolomite (from Example 3 or 4), both MgO and CaO can be converted by aqueous hydration in submicron or nanoscale Mg (OH) ₂ - and Ca (OH) ₂ particles, the size of the original oxide particles preserved. The degree of conversion of MgO to Mg (OH) ₂ or of CaO to Ca (OH) ₂ is> 90% of theory.

hydration

Table 6. Hydration. Area prefers More preferred Even more preferred Suspension, dry matter TS in% 0-99 0-85 0-70 0-65

Fig. 8a, 8b show SEM images of hydrated dolomite from Example 3 and 4. Example 6.

The material contains aggregates and exposed particles. The grain size of the primary particles is about 50-200 nm. These consist of Mg (OH) ₂ and Ca (OH) ₂ .

rating

The examples show that it is possible in the way described here to produce oxides, carbonates and hydroxides in submicron or nanoscale primary grain size, which differ in size and purity from the previously known analogous materials and by the very high Reactivity are particularly suitable for the bleaching of organic fiber materials.

Product description Partially calcined dolomite: MgO and CaCO ₃

Table 7. Partially Calcined Dolomite MgO and CaCO ₃ . unit Area Prefers More preferred Chem. Composition SiO ₂ ma% <10 <5 <1 Al ₂ O ₃ ma% <3 <0.5 <0.1 Fe ₂ O ₃ ma% <3 <0.5 <0.1 MnO ₂ ma% <1 <0.5 <0.1 TiO ₂ ma% <1 <0.5 <0.1 K ₂ O ma% <5 <3 <1 Na ₂ O ma% <5 <3 <1 Moisture, 120 ° C ma% <5 <3 <1 Balance except CaO, MgO and CO ₂ ma% <10 <5 <2 Mineral content MgCO ₃ ma% <15 <10 <5 CaCO ₃ ma% <85 <80 <75 MgO ma% > 20 > 23 > 25 CaO ma% <10 <5 <3 Mg (OH) ₂ ma% <10 <7 <5 Ca (OH) ₂ ma% <10 <5 <3 quartz ma% <5 <3 <1 rest ma% <10 <7 <3 Phys. dates Whiteness R 457 % > 75 > 80 > 85 L > 70 > 75 > 80 Abrasion Einlehner mg <500 <250 <100 Nassiebrst. > 100 microns ma% <3 <1 <0.5 Spec. Surface BET m2 / g > 1 > 2 > 3 Grain size Laser bending. microns > 40 ma% <50 <40 <30 <40 ma% > 20 > 30 > 40 <30 ma% > 25 > 35 > 45 <20 ma% > 30 > 40 > 50 <10 ma% > 20 > 30 > 40 <5 ma% > 10 > 20 > 30 <2 ma% > 5 > 10 > 15 <1 ma% > 1 > 2 > 3 Primary particles REM, nm > 300 Ma -% * <50 <40 <30 <300 Ma -% * > 30 > 40 > 50 <200 Ma -% * > 20 > 30 > 40 <100 Ma -% * > 10 > 20 > 30 <50 Ma -% * > 5 > 10 > 15 * Image Exploitation

• Ziel Primärkorngröße: Schwerpunkt bei 50-200 nm
• Ziel Korngröße mittels Laserbeugung, z.B. Cilas-Gerät, Fa. Quantachrome: d99=20, d90=10. d50=2 µm

Most preferred:

• Target primary grain size: center of gravity at 50-200 nm
• Target particle size by means of laser diffraction, eg Cilas instrument, Quantachrome: d99 = 20, d90 = 10. d50 = 2 μm

Fully calcined dolomite: MgO and CaO:

Table 8. Fully Calcined Dolomite MgO and CaO. unit Area Prefers More preferred Chem. Content SiO ₂ ma% <10 <5 <1 Al ₂ O ₃ ma% <3 <0.5 <0.1 Fe ₂ O ₃ ma% <3 <0.5 <0.1 MnO ₂ ma% <1 <0.5 <0.1 TiO ₂ ma% <1 <0.5 <0.1 K ₂ O ma% <5 <3 <1 Na ₂ O ma% <5 <3 <1 Moisture, 120 ° C ma% <5 <3 <1 Balance except CaO, MgO and CO ₂ ma% <10 <5 <2 Mineral content MgCO ₃ ma% <10 <7 <5 CaCO ₃ ma% <10 <7 <5 MgO ma% > 25 > 30 > 35 CaO ma% > 40 > 45 > 50 Mg (OH) ₂ ma% <10 <7 <5 Ca (OH) ₂ ma% <10 <7 <5 quartz ma% <5 <3 <1 rest ma% <10 <7 <3 Phys. dates Whiteness R 457 % > 75 > 80 > 85 L > 70 > 75 > 80 Abrasion Einlehner mg <500 <250 <100 Nassiebrst. > 100 microns ma% <3 <1 <0.5 Spec. Surface BET > 1 > 2 > 3 Grain size Laser bending. microns > 40 ma% <50 <40 <30 <40 ma% > 20 > 30 > 40 <30 ma% > 25 > 35 > 45 <20 ma% > 30 > 40 > 50 <10 ma% > 20 > 30 > 40 <5 ma% > 10 > 20 > 30 <2 ma% > 5 > 10 > 15 <1 ma% > 1 > 2 > 3 Primary particles REM, nm > 300 Ma -% * <50 <40 <30 <300 Ma -% * > 30 > 40 > 50 <200 Ma -% * > 20 > 30 > 40 <100 Ma -% * > 10 > 20 > 30 <50 Ma -% * > 5 > 10 > 15 * Image Exploitation

Mostly preferred
Target primary grain size: center of gravity at 50-200 nm
Target particle size by means of laser diffraction, eg Cilas instrument, Quantachrome: d99 = 20, d90 = 10. d50 = 2 μm

Partially calcined dolomite (MgO and CaCO ₃ after aqueous hydration: Table 9. Partially calcined dolomite (MgO and CaCO3) after aqueous hydration. unit Area Prefers More preferred Chem. Content SiO ₂ ma% <10 <5 <1 Al ₂ O ₃ ma% <3 <0.5 <0.1 Fe ₂ O ₃ ma% <3 <0.5 <0.1 MnO ₂ ma% <1 <0.5 <0.1 TiO ₂ ma% <1 <0.5 <0.1 K ₂ O ma% <5 <3 <1 Na ₂ O ma% <5 <3 <1 Balance except CaO, MgO CO ₂ and H2O ma% <10 <5 <2 Mineral content MgCO ₃ ma% <15 <10 <5 CaCO ₃ ma% <85 <80 <75 MgO ma% <10 <5 <3 CaO ma% <10 <5 <3 Mg (OH) ₂ ma% > 25 > 30 > 32 Ca (OH) ₂ ma% <10 <5 <3 quartz ma% <5 <3 <1 rest ma% <10 <7 <3 Phys. dates Whiteness R 457 % > 75 > 80 > 85 L > 70 > 75 > 80 Abrasion Einlehner mg <500 <250 <100 Nassiebrst. > 100 microns ma% <3 <1 <0.5 Spec. Surface BET m2 / g > 1 > 2 > 3 Grain size Laser bending. microns > 40 ma% <50 <40 <30 <40 ma% > 20 > 30 > 40 <30 ma% > 25 > 35 > 45 <20 ma% > 30 > 40 > 50 <10 ma% > 20 > 30 > 40 <5 ma% > 10 > 20 > 30 <2 ma% > 5 > 10 > 15 <1 ma% > 1 > 2 > 3 Primary particles REM, nm > 300 Ma -% * <50 <40 <30 <300 Ma -% * > 30 > 40 > 50 <200 Ma -% * <80 <70 <60 <100 Ma -% * <80 <70 <60 <50 Ma -% * > 5 > 10 > 15 * Image Exploitation

Mostly preferred
Target primary grain size: center of gravity at 150-300 nm
Target particle size by means of laser diffraction, eg Cilas instrument, Quantachrome: d99 = 20, d90 = 10. d50 = 2 μm

Partially calcined dolomite (MgO and CaO) after aqueous hydration: Table 10. Partially calcined dolomite (MgO and CaO) after aqueous hydration. unit Area Prefers More preferred Chem. Content SiO ₂ ma% <10 <5 <1 Al ₂ O ₃ ma% <3 <0.5 <0.1 Fe ₂ O ₃ ma% <3 <0.5 <0.1 MnO ₂ ma% <1 <0.5 <0.1 TiO ₂ ma% <1 <0.5 <0.1 K ₂ O ma% <5 <3 <1 Na ₂ O ma% <5 <3 <1 Moisture, 120 ° C ma% <5 <3 <1 Balance except CaO, MgO CO ₂ and H ₂ O. ma% <10 <5 <2 Mineral content MgCO ₃ ma% <10 <7 <5 CaCO ₃ ma% <10 <7 <5 MgO ma% <10 <5 <3 CaO ma% <10 <5 <3 Mg (OH) ₂ ma% > 25 > 30 > 35 Ca (OH) ₂ ma% > 40 > 45 > 50 quartz ma% <5 <3 <1 rest ma% <10 <7 <3 Phys. dates Whiteness R 457 % > 75 > 80 > 85 L > 70 > 75 > 80 Abrasion Einlehner mg <500 <250 <100 Nassiebrst. > 100 microns ma% <3 <1 <0.5 Spec. Surface BET > 1 > 2 > 3 Grain size Laser bending. microns > 40 ma% <50 <40 <30 <40 ma% > 20 > 30 > 40 <30 ma% > 25 > 35 > 45 <20 ma% > 30 > 40 > 50 <10 ma% > 20 > 30 > 40 <5 ma% > 10 > 20 > 30 <2 ma% > 5 > 10 > 15 <1 ma% > 1 > 2 > 3 Primary particles REM, nm > 300 Ma -% * <50 <40 <30 <300 Ma -% * > 30 > 40 > 50 <200 Ma -% * > 20 > 30 > 40 <100 Ma -% * > 10 > 20 > 30 <50 Ma -% * > 5 > 10 > 15 * Image Exploitation

Mostly preferred
Target primary grain size: center of gravity at 150-300 nm
Target particle size by means of laser diffraction, eg Cilas instrument, Quantachrome: d99 = 20, d90 = 10. d50 = 2 μm

Three-phase systems:

As described above, partial-to-full calcined demand-specific three-phase systems of CaCO ₃ , MgO, and CaO can be selected to achieve the ideal combination of reactivity and acceptable deposits.

Examples:

1. a) Oxide-carbonate mixtures:
   • Mixture of components MgO, CaO and CaO ₃ . This product group is chemically between Partial and Vollkalzinat.
2. b) Hydroxide-carbonate mixtures:
   • Mixture of the components Mg (OH) ₂ , Ca (OH) ₂ and CaCO ₃ . The starting material for this product is chemically between partial and full calcine, but was hydrated here.

Alkaline peroxide bleaching of organic fiber materials using the described products

For this purpose, unbleached wood pulp or wood fibers is bleached with peroxide using various alkaline additives and the whiteness and yellowness of the product are determined. At the same time, the COD content is also determined. Table 11. COD Brightn. Yellown. No. NaOH Ca (OH) ₂ Vollkalzinat Teilkalzinat Vollkalzinat Teilkalzinat Mg (OH) 2 NAwg [Kg / T] R457 default default powder powder Slurry / hydrate. Slurry / hydrate. default 0 64.8 25.4 1 1.9 0.0 46.8 63.7 25.3 2 1.9 2.0 51.4 76.7 18.3 3 0.9 0.0 27.7 67.7 23.0 4 0.9 2.0 29.1 74.0 20.2 5 0.9 0.0 30.3 69.8 22.4 6 0.9 2.0 30.6 75.2 19.5 7 0.9 0.0 26.4 74.7 20.1 8th 0.9 2.0 29.4 75.9 19.3 9 0.9 0.0 31.6 74.1 20.4 10 0.9 2.0 34.4 75.7 19.3 11 0.9 0.0 30.2 74.0 20.3 12 0.9 2.0 32.3 76.1 19.0 13 0.9 0.0 32.9 75.9 19.3 14 0.9 2.0 35.1 75.8 19.3 COD brightn, Yellown. No. NaOH Ca (OH) ₂ Vollkalzinat Teillkalzinat Vollkalzinat Tellkalzinat Mg (OH) 2 NAwg [Kg / t] R457 default default powder powder Slurry / hydrate. Slurry / hydrate. default 0 64.6 25.4 1 1.9 0.0 46.8 63.7 25.3 2 1.9 2.0 61.4 76.7 18.3 3 0.9 0.0 27.7 67.7 23.0 4 0.9 2.0 29.1 74.0 20.2 6 0.9 0.0 30.3 69.8 22.4 6 0.9 2.0 30.6 75.2 19.5 7 0.9 0.0 26.4 74.7 20.1 8th 0.9 2.0 29.4 75.9 19.3 9 0.9 0.0 31.6 74.1 20.4 10 0.9 2.0 34.4 75.7 19.3 11 0.9 0.0 30.2 74.0 20.3 12 0.9 2.0 32.3 76.1 19.0 13 0.9 0.0 32.9 75.9 19.3 14 0.9 2.0 35.1 75.8 19.3 NaWG = soda water glass complexing agent: Na5DTPA
Solids content = 23% COD = chemical oxygen demand
Brightn. = Whiteness R 457 Temperature = 65 ° C
Duration = 3 h H2O2 = 3

Bleached organic fiber materials, such as wood fibers having the highest whiteness and / or lowest yellowness and / or lowest COD in the process water, were then behaving when the described Ca-Mg products were used as the alkaline component for the oxide bleaching.

The Ca-Mg products are better than calcium hydroxide in terms of whitening and are comparable to magnesium hydroxide. The stabilizing effect of water glass is still more pronounced (1 to 2 whiteness points) for all Ca-Mg products than for magnesium hydroxide. Although the highest final whiteness is obtained with sodium silicate with sodium silicate, it is also by far the highest COD value. This is significantly reduced with the Ca-Mg products. The powder (= oxide) or slurry (= hydrate) form shows no differences, both are equally suitable.

Since the purity of the Ca-Mg products are significantly higher and the costs significantly lower than, for example, with sodium hydroxide or Mg (OH) ₂ and also the Ca component can be adapted to the specific requirements (reactivity vs. deposition tendency) are the initially set tasks or goals have been resolved.

It describes organic fiber materials, such as wood fibers produced using submicro and nano-scale calcium and magnesium compounds and their preparation.

The SEM images of the Ca-Mg products show significant differences compared to the already known materials, mainly in the grain size of the primary particles and the grain shape and grain size and the microstructure or the addition of the particles to each other.

From this it can be concluded that the Ca-Mg products differ from the market-known products and because of the submicro- and nano-scale particle size also show a considerable other improved and more extensive functionality in the application, as could be proven by the experiments. As a result, bleached organic fiber materials such as wood fibers of better quality can be produced.

Claims (9)

1. Method of producing bleached wood fibres,
   characterised in that
   a bleach mixture comprising hydrogen peroxide, alkaline or alkaline reaction-producing materials as well as sub-micro scale or nano scale particles of Ca and/or Mg compounds with a particle diameter of between 50 nm and 300 nm is used to bleach the organic fibre materials, and the Ca and/or Mg compound particles are obtained in a preceding production step by partially or completely calcining Ca and/or Mg compounds.
2. Production method as claimed in claim 1,
   characterised in that
   more than 10% of the Ca and/or Mg compound particles have a particle diameter of less than 100 nm.
3. Production method as claimed in one of the preceding claims, characterised in that
   the compound particles have oval and/or spherical shapes.
4. Production method as claimed in one of the preceding claims, characterised in that
   the Ca and/or Mg compound particles are made up of CaO and/or Ca(OH)₂ and/or CaCO₃ and/or MgO and/or Mg(OH)₂.
5. Production method as claimed in one of the preceding claims, characterised in that
   the Ca and/or Mg compound particles are produced in a preceding production step by partially or completely calcining MgCa(CO₃)₂ (dolomite) or other Ca-Mg-Co₃ mixed compounds, such as CaMg₃(CO₃)₄ (huntite).
6. Use of a bleach mixture comprising hydrogen peroxide, alkaline or alkaline reaction-producing materials as well as sub-micro scale or nano scale particles of Ca and/or Mg compounds with a particle diameter of between 50 nm and 300 nm to bleach wood fibres.
7. Use of a bleach mixture as claimed in claim 5 or 6, characterised in that
   more than 10% of the Ca and/or Mg compound particles have a particle diameter of less than 100 nm.
8. Use of a bleach mixture as claimed in claim 5-7, characterised in that
   the Ca and/or Mg compound particles are made up of CaO and/or Ca(OH)₂ and/or CaCO₃ and/or MgO and/or Mg(OH)₂.
9. Bleached wood material,
   characterised in that
   the wood material is produced by a method as claimed in one of preceding claims 1 - 5.

Images