DE1947931C3 - Process for bleaching lignocellulosic material - Google Patents

Description

Lignocellulose pulp made by the sulfate or sulfite process is common to many Applications are too dark in color and must therefore be bleached. The dark color is due to the Causes lignin component of the pulp. The bleaching is particularly necessary for sulphate pulps, which contain larger amounts of residual lignin than sulphite pulps. The remaining lignin in the sulphate pulps is also less sensitive to one for structural reasons chemical treatment. Generally, chlorine is used in the bleaching of lignocellulose pulps initiate, after which an extraction of the chlorine-treated palps by means of an alkali, such as e.g. sodium hydroxide. These treatments are in turn followed by one or more oxidation and extraction treatments. For sulphate pulps it is usually necessary to have at least five stages followed by washing after each step to produce a fully bleached pulp. The sequence chlorination-alkali extraction-chlorine dioxide treatment-alkali extraction-chlorine dioxide treatment (abbreviated C-E-D-E-D) is typical of the current practice. There will be too other sequences are used, including hypochlorite and alkaline hydrogen peroxide treatments be made. There are many variations on the chlorine bleaching process, the main ones being aim to increase the degree of bleaching and reduce pulp degradation by the bleaching agents. However, chlorine is still used in the initial treatments of the pulp. The chlorine bleaching Unfortunately, it has the disadvantage that the reaction of chlorine with the pulp causes formation of chlorine aromatic materials, due to their toxicity and their high C. O. D. contamination problems arise. However, chlorine is the preferred bleach because it is readily available and is cheap.

It has now been found that this improves the chlorine bleaching of a lignocellulose pulp can be that the chlorine treated pulp in the presence of an alkali base at superatmospheric Pressure treated with gaseous oxygen, the reaction products then from the Pulp to be washed out. A lignocellulose pulp treated in this way can by one or several bleaching stages can be further bleached to a high brightness without significant degradation entry. The new bleaching process reduces the CC D. of contaminated wastewater and only creates minimal amounts of toxic chlorinated aromatic materials.

The object of the present invention is to provide a method for bleaching lignocellulose pulp to a high brightness, which process is a results in improved brightness stability and sufficient strength properties and also as a whole Is cheaper than the known process and also to create a bleaching process, whose waste water only are slightly contaminated.

The process according to the invention for bleaching lignocellulosic material contains the following initial work steps: (1) Treatment of the lignocellulosic material in an aqueous suspension of a consistency of 3 to 7 percent by weight at room temperature with a chlorine-containing reagent with a chlorine equivalent of 2 to 8 percent by weight for 10 to 60 minutes and (2) Contacting the chlorine-treated lignocellulosic material with 2 to 3 percent by weight of an alkaline medium, whereupon the alkaline material in aqueous suspension has a consistency of 3 to 12 percent by weight with oxygen or an oxygen-containing gas under a pressure of 2.1 to 14 kg / cm ² is treated at a temperature of 100 to 200 C for 10 to 30 minutes and the lignocellulose material is washed with water after completion of the work step (1) and / or (2).

The process is characterized in that the chlorine-containing reactant of stage (1) from a mixture of chlorine and chlorine dioxide or of chlorine dioxide with subsequent chlorine treatment without intermediate washing or of hypochlorite with subsequent chlorine treatment.

The wood pulp can be washed at the end of step (1), reducing the amount of pulp in step (2) required alkali base is reduced. In step (1) it is advantageous to use a small amount of chlorine dioxide Add ammonia or an ammonium salt, as is also done in the known method to to preserve the viscosity of the pulp. In step (2) it is advantageous to use together with the alkali base during to use magnesium carbonate or magnesium oxide for oxygen treatment. The usage however, these reagents are optional.

At the end of the two stages of the process, the lignocellulose pulp is delignified to a greater extent than according to the corresponding levels of one

conventional process, resulting in a lower permanganate number and a higher brightness expresses. The pulp is in a condition that it can be easily bleached to an even higher brightness. The additional bleaching treatment required depends on the type of pulp and the concentration of the in Stage (1) used chlorine. When bleaching sulphite wood pulp, a single additional treatment is such as a treatment with chlorine dioxide, is sufficient, even after a conventional one Chlorination / alkali extraction to achieve a brightness of 90. However, after chlorination / alkaline oxygen treatment plus a single additional chlorine dioxide level, the brightness of a sulphate pulp with the same amount of chemicals used higher and better stable; conversely, the concentration of chlorine can be reduced by the to achieve the same brightness value. When bleaching sulphate wood pulp using concentrations of chlorine in the step (1) which are similar to a conventional method (for example 5 to 6 "", based on the pulp) and after a chlorination / alkaline oxygen treatment

(CO-), using the conventional D-E-D levels, the pulp is bleached to an exceptional brightness value, for example 92.5 to 93.0 with an exceptionally small inversion of 0.5 to 1.0 . The sole use of a single chlorine dioxide level COD results in a brightness of 89 to 91 with a slight inversion of 1.0 to 2.0.

Alternatively, after chlorination, the pulp can be subjected to an alkaline oxygen treatment (C-O-) The specified sequences are subjected to further treatments: chlorination, alkaline Oxygen treatment, hypochlorite treatment; Chlorination, alkaline oxygen treatment, peroxide treatment; Chlorination, alkaline oxygen treatment, Hypochlorite treatment, chlorine dioxide treatment; or chlorination, alkaline oxygen treatment, Hypochlorite treatment, chlorine dioxide treatment, alkali extraction, chlorine dioxide treatment.

Alternatively, the amount of chlorine used in step (1) can be reduced to 50% of its conventional value (for example 2 to 3 "") can be decreased, and when C-O- is followed by the combination D-E-D, with the chemical concentrations otherwise the same, then the brightness value is the same and the brightness stability is then better than a conventional process that uses the larger amount of chlorine. the high brightness values can be achieved without severe pulp degradation occurring (e.g. Viscosities from 15 to 25).

If the process is applied to the bleaching of sulphate wood pulp then the working conditions are typically as follows:

Sulphate wood pulp in aqueous suspension with a consistency of 3 to 7% is made at room temperature treated with 2 to 8% chlorine for 10 to 60 minutes. The percentages are expressed in weight and based on Oven dried pulp sourced. The maximum amount of chlorine depends on the lignin content of the unbleached Pulp and usually exceeds the concentration of chlorine used in conventional bleaching.

The wood pulp treated with chlorine can optionally be washed with water. When washed, the wood pulp is treated with 2 to 3 "" sodium hydroxide and optionally with 1 "" magnesium carbonate or magnesium oxide. If not washed, the wood pulp is treated with sufficient sodium hydroxide to neutralize the acidity and to create an excess of 2 "" sodium hydroxide. 1 "/" magnesium carbonate or magnesium oxide is also added if necessary. The washing step can be omitted if lower chlorine concentrations are used in the first chlorine treatment. The omission of washing has the advantage that contaminated waste water is avoided at this stage of the process. The alkaline pulp with a consistency of 3 to 12 ° _o is then (preferably) heated to a maximum of 130 ° C. under an oxygen pressure of 3.4 atm and with stirring in an autoclave for a period of 2 to 3 minutes. It is kept at 130 ° C. for 10 minutes under an oxygen pressure of 3.5 atm.

The permanganate number of the wood pulp after completion of the oxygen treatment depends on that in the chlorine concentration used for the first chlorine treatment. With the chlorine concentrations, as in Using conventional methods, the C-O modification gives im permanganate numbers Range from 0.5 to 1.5. With a chlorine concentration of approximately 40 to 50 "" of the normal Permanganate numbers ranging from 3.0 to 4.5 were obtained.

The oxygenated wood pulp is then washed with water to remove the reagents and Separate reaction products. The washed wood pulp is then at a consistency of 12 ",, treated with 1 "" chlorine dioxide for 3 hours at 80 C.

The brightness value after the end of the chlorine dioxide treatment achieved depends on the concentration of chlorine used in the first chlorine treatment away. If the chlorine concentration is the same as the C-B sub-sequence then this gives C-O modification brightness values in the vicinity of 90 with only a slight inversion. If little chlorine is used and if other conditions are kept constant then that is Brightness lower and an additional bleach stage may be required. Even the highest For brightness values, the viscosity of the pulp remains in the acceptable range of 15-20.

The reagent used in the first stage of the bleaching process is usually chlorine. However can contain chlorine-containing compounds such as chlorine dioxide, sodium hypochlorite or calcium hypochlorite partially or completely replace the chlorine in the first stage. The chlorine dioxide / chlorine treatment can performed either simultaneously or sequentially will. The first stage is carried out under acidic conditions.

The alkali base used in the second stage of the process is usually sodium hydroxide. It however, potassium hydroxide or sodium or potassium carbonate or calcium hydroxide would also be suitable. The magnesium carbonate optionally used in the second stage helps to delay the Degradation of lignocellulose pulp. In step (1) ammonia can be used to break down the To delay pulp.

The treatment of the alkaline lignocellulose pulp with oxygen is carried out at a pressure in the range of 2.1 to 70 atm in one container. The wood pulp is during the oxygen treatment that Takes 10 to 30 minutes, kept at a temperature in the range of 100 to 200 ° C with stirring. The lignocellulose pulp is mixed with water so that a consistency of 3 to 12% is obtained.

Instead of pure oxygen, air can be used at an appropriate pressure, i.e. that the pressure should be five times higher than when using pure oxygen. Furthermore, the Oxygen is added to the extraction stage in a chemically bonded form, so that oxygen is in statu nascendi arises during the treatment. For example, the oxygen can be in the form of metal peroxides can be added.

It is clear to a person skilled in the art that the conditions for the treatment must be selected according to the type of lignocellulose pulp in order to obtain the optimal treatment / u. At the start of the oxygen treatment, depending on the pressure vessel used, it may be appropriate to preheat the pulp to less than the maximum oxygen pressure.

When treating the lignocellulose pulp with gaseous oxygen, it is preferred to use the pulp To treat the alkaline pulp with an alkaline material, gaseous oxygen under pressure suspend and finally bring the reaction mixture to the reaction temperature. It was found, that this sequence results in less degradation of the lignocellulose pulp than if the pulp before Oxygen addition is heated.

The higher dissolution of the lignin in the lignocellulose pulp, which is achieved by the method according to the invention is achieved by an interaction of the first chlorine treatment and the subsequent one alkaline oxygen treatment. When the use of oxygen in the second stage is omitted, so that the well-known sequence of chlorine / alkali extraction results, then has the Permanganate number of a sulfate wood pulp (which in the unbleached state has a permanganate number of 18 to 20) at the end of the extraction stage with a first chlorine treatment with 5 to 6% a value of 4 to 6 and with a first chlorine treatment with 2 to 3 "" a value of more than 9. Comparable values for permanganate numbers of sulphate wood pulps which have been treated according to the invention 1.0 to 1.5 or 3.0 to 4.5. When the chlorination stage of the present process is omitted, so that only the alkaline oxygen treatment remains, then a sulfate wood pulp treatment achieves a permanganate number of about 7, at the same time pulp degradation occurs, as expressed in a viscosity value of around 10.

In the description, under the expressions »brightness«, »permanganate number« and »viscosity« meant characterizing values for wood pulps obtained by the following standard procedures will:

Brightness: - TAPPI Standard T 217 m, 218m. Permanganate number: - - TAPPI Standard T 214 m. Viscosity: - TAPPI Standard T 230 sm (0.5 Γ)

The brightness inversion is expressed in brightness values that are determined after the brightness platc Has been heated to 105 C for 1 hour.

example 1

A sulphate wood pulp obtained from conifers

was (mainly spruce and balsam fir) and the

a permanganate number of 18.4 and a viscosity

of 27.8 was subjected to the sequence of 5 bleaching stages given below:

1. The wood pulp, which had a consistency of 3.5 ", ^{was treated with 2.0% chlorine at 20 °} C. for 45 minutes. The wood pulp was then washed with water.

2. The chlorine-treated wood pulp with a consistency of 7.0% was treated with 5.0% sodium hydroxide and placed in an autoclave. The alkaline wood pulp was then treated with oxygen under a pressure of 11.2 at and at a temperature of 100 ^{° C. for 30 minutes.} The wood pulp was then washed. The wood pulp at the completion of this stage had a permanganate value of 4.0 and a viscosity of 21.2 cps

3. The oxygen-treated wood pulp, the consistency of 12.0 "had ,,, was then treated with 1.0" treated "Chordioxyd for 3 hours at 70 ⁰ C. The wood pulp was then washed.

4. The wood pulp, which had a consistency of 12.0 ", was then extracted ^{with 0.5" sodium hydroxide at 60 ° C. for 1.5 hours.} The wood pulp was then washed.

5. The wood pulp, which had a consistency of 12.0 ", was then ^{treated with 0.3" chlorine dioxide at 70 °} C. for 3 hours. The wood pulp was then washed with water. The bleached product had a brightness of 87.9 and a viscosity of 18.4c.ps

Example 2

A sample of sulphate wood pulp obtained from conifers (mainly spruce and balsam fir) and which had a permanganate number of 18.4 became the sequence given below subjected to five bleaching stages:

1. The wood pulp was placed in polyethylene bags with hand stirring for 10 minutes at a consistency of 7 " long chlorinated.

2. Sufficient sodium hydroxide solution was added to the unwashed pulp so that a: complete Reaction with the chlorine added in stage 1 resulted and an excess of 3.0% sodium hydroxide remained. The wood pulp was stirred for 2 minutes and placed in an autoclave. While In a preheating period, an oxygen pressure of 6.3 atm was generated in the autoclave. The oxygen treatment was then done at 11.2 atm for 30 minutes. The pulp was then washed with water and then subjected to three further stages according to Example 1.

3. pulp consistency 12.0%, 1.0% chlorine dioxide for 3 hours at 70 ⁰ C.

4. Alkali extraction with 0.5% sodium hydroxide for 1.5 hours at 6O ⁰ C and a consistency of 12%.

5. pulp consistency 12.0%, 0.3% chlorine dioxide for 3 hours at 70 ⁰ C. The wood pulp was washed after the end of stages 3, 4 and 5 respectively with water.

The reagents of the first two stages and the reaction conditions and the properties obtained the Holznulne are in Tnhfllo I anocopKi-n

7th sodium 1 947 931 Permanganate-
number after the Brightness at 8th Reversal of hydroxide. % 2nd stage end Image brightness Chlorination time, 4.14 10.07 65.75 Viscosity am 3.1 Chlorine. % min 4.14 Table I. 7.1 83.7 bark. cP 2.6 60 4.14 Temperature of
Oxygen be 7.3 81.1 16.23 2.6 1.0 10 5.28 plot, C 6.45 84.1 13.6 3.3 1.0 10 5.28 100 6.1 86.2 14.3 1.4 1.0 60 5.28 100 5.5 87.1 15.88 3.0 2.0 10 6.42 110 4.55 89.7 14.4 2.7 2.0 10 6.42 100 4.2 90.2 14.8 1.9 2.0 60 6.42 100 3.8 89.0 15.75 1.6 3.0 10 110 15.1 3.0 10 100 14.8 3.0 100 110

Example 3

A sulphate wood pulp obtained from conifers (mainly spruce and balsam fir) and which had a permanganate number of 18.4 became the basic stages of the bleaching process subjected, namely, chlorination and alkaline oxygen treatment. There were six separate ones Tests carried out. Samples (6) of a washed one weighing 13.1 g Pulp with 5.25% consistency was mixed with various amounts of chlorine for 10 minutes long treated. The wood pulp was not washed, but treated with sufficient sodium hydroxide to so that after neutralization of the acidity an excess of 4.0% remained. The ones with sodium hydroxide treated wood pulp was stirred for 2 minutes. 1.0% magnesium carbonate then became the Wood pulp added, which was stirred for an additional minute. Each sample was taken separately for 30 minutes treated in an autoclave with oxygen at 11.2 at pressure. There were two temperatures at the Oxygen treatment used, namely 120 and 130 ° C. After completion of the oxygen treatment the wood pulp was washed with water and the permanganate number was determined. The results are given in Table II.

1.34%
5.53%
120 C
9.0 Tables 4.0%
8.56%
120 ^c C
2.8 1.34%
6.9%
130C
5.8 2.68%
7.05%
130 C
4.2 4.0%
8.56% Added chlorine
Added sodium
hydroxide 2.68%
7.05%
120'C
5.1 130 C
2.3 Temperature of the sour
fabric treatment
Permanganate number according to the
Oxygen treatment ..

It can be seen that at a concentration of 1.34% chlorine during the chlorine treatment, a wood pulp is obtained with a relatively high permanganate number.

Example 4

A sulphate wood pulp obtained from conifers (mainly spruce and balsam fir) and which had a permanganate number of 18.4 subjected to a bleaching sequence using six separate tests.

A. 13.1 g of wood pulp having a consistency of 5.25 "" were chlorinated with 5.35% chlorine for 10 minutes Handrührung. The wood pulp was then washed twice with I ^1/2 liters of water and crumbled in a Hobart mixer 4.0% sodium hydroxide was added to the wood pulp and this was stirred for 2 minutes before it was placed in an autoclave, in which the wood pulp was treated for 30 minutes under an oxygen pressure of 11.2 atmospheres at 100 ° C Pulp was then determined.

B. 22.0 g of wood pulp with a consistency of 11.3% was treated with 4.0% chlorine for 10 minutes with hand stirring at room temperature. The wood pulp was then _{washed twice with 1 1/2} liters of water.

The wood pulp was then crumbled and treated with 2.4% sodium hydroxide for 2 minutes with stirring. The wood pulp was then treated in an autoclave at 100 ° C. for 30 minutes with oxygen at a pressure of 11.2 at. The pulp was at 100 ⁰ C pretreated untei an oxygen pressure of 6.3. The permanganate number was then measured. The wood pulp was then treated in a third stage at a consistency of 12% with 0.8% chlorine dioxide for 3 hours at 70.degree. Those with chlorine

SS dioxide treated pulp was extracted next in Einei fourth stage at a consistency of 12% with 0.4% sodium hydroxide I ^1/2 hours bed 6O ⁰ C. The extracted wood pulp was then subjected to a fifth treatment at 12% consistency with 0.3% chlorine dioxide for 3 hours at 70 ⁰ C. The brightness of the wood pulp was then determined.

C. 22.0 grams of wood pulp was added to the bleaching sequence of Subject to sample B, with the difference that in dei first stage 3.18% chlorine was used.

D. 17.5 g wood palp with a consistency of 7.0 "were treated with 4.0% chlorine for 10 minutes with stirring at room temperature. The wood pulp was then _{washed twice with 1 1/2} liters of water

509626/10

and crumbled in a Hobart mixer. 2.0 "" Sodium hydroxide was then added and the wood pulp was stirred for 2 minutes and placed in an autoclave. The wood pulp had a consistency of 7.0 ". The wood pulp was at vorerhiitzt in the autoclave for 12 minutes at a SauerstofTdruck of 6.3 and then 30 minutes under an oxygen pressure of 11.2 at 100 ⁰ C heated. The wood pulp was then _{washed twice with 1/2} liter of water. The permanganate number of the wood pulp was then determined. The pulp was then subjected to the three stages 3, 4 and 5 of sample B, but in the

Chlorine dioxide treatment in stage 3 1.0 ",,, Chlordioxyc and at stage 4, 0.5 "" sodium hydroxide was used. At the end of the fifth stage, it became sacred measured.

ο ^E u ¹⁷ A ^{5 8 Holz} P ^ul P ^e were subjected to the bleaching sequence before t ^rO r ι £, with the difference that in stage 1 5.0 "" chlorine were used.

The ^{5 8 Wood} P ^ul P ^e were the bleaching sequence of

it ¹ "ρ i? _n T ^t i? ' ^{Orren-mil the} difference that were used in Stage 1 6.0 ",, chlorine

? 'i ^{Codes of the Ble} ' C "sequence are given in TaI.

Table III

sample

Used chlorine

Used sodium hydroxide

Permanganate number according to
Level 2

Brightness after level 5 ...

5.35%

4.0%

2.83

4.0% 2.4%

4.6

87.7 3.18%
2.4%

4.95
85.5

4.0%
2.0%

6.1

85.3

5.0% 2.0%

4.15 90.0

6.0% 2.0%

3.7 90.5

Example 5

A sulfate wood pulp obtained from conifers (mainly spruce and balsam fir) and having a permanganate number of 18.4 was subjected to six separate bleaching tests. 17.5 g (oven-dried) wood pulp were treated with various amounts of chlorine for 10 minutes at room temperature and at a consistency of 7 _"o chlorinated.

35 Natnumhydroxyd was added and 2 minutes AT ^space P i ^{em erat} "pure stirred. 1 \ magnesium ^W u ψ ^{to provide} ß ^e 8 <"^"d 1 minute einge- ^Ie ^ ° Tu ^{PE was then placed in an} autoclave, HJ. ^{And at various} temperatures iedenen 30 Minu η long under an oxygen pressure of 11.2 at Ho S'ι ^Pe ™ ^{ix ana} tzahl and the viscosity of Hobpulpe were then determined.

LT ^ i ^ ^pale ^ fol _g e are in the

Added chlorine

Added sodium hydroxide

Oxygen treatment temperature

Pcr.Tianganate number

viscosity

Table IV

It can be seen that a low concentration of chlorine gives, on average, higher permanganate numbers.

Example 6

A sulfate wood pulp obtained from conifers (mainly spruce and balsam fir) and having a permanganate number of 18.4 was subjected to five separate bleaching tests. 52.5 g (oven-dried) parts of a wood pulp were washed twice with 4 liters of water and then chlorinated with various chlorine concentrates for 10 minutes at room temperature at a consistency of 3.0 ". During the chlorination, the wood pulp was mechanically stirred. The wood pulp was then washed twice with 3 liters of water. The washed pulp was broken up in a Waring blender at a consistency of 3 "" and on a filter funnel to a consistency of 7 ° _o concentrated. 3.0 "" sodium hydroxide and 1.0 "" magnesium car-

1.0% 2.0% 3.0% 1.0% 5.0% 6.0% 4.14% 5.28% 6.42% 4.14% 3.0% 3.0% 12O ⁰ C
10.6
22.9 cP 120'C
6.9
21.7 cP 120 C
4.9
21.7 cP 123 C
7.1
20.3 c P 120 C
2.4
22, OcP 120 C
2.9
21.5cP

Se

^rHoIz P ^u 'P ^{e set by hand for} 3 minutes ⁿ . ^{άΆηη in the} autoclave

^{the following conditions}

ss

^{'At 60} ^^ ™ * "minutes at ^{oF 6 3} subsequent ^Beha" dJung stirring at ² ^ ^{And the W} ^ given ^the Sauerstofllehand- <üe V-Skosuat

' ^{D and E} draws smd)

- * ^Hfel

6 ₅ ^0A

the

Snn nlch ^ in f _A V ^keh

dfoxvdSnHi ^{5 Mmuten}
Oxide treatment measured.

at 12.5 g

treated at 70 ^{0 C.}

^ ^ ^the & sulfur-

The wood pulp, which had a consistency of 12%, was then at 60 ° C for 1/2 hour with 0.5% sodium hydroxide extracted.

In stage 5, the wood pulp, which had a consistency of 12%, was treated with 0.3% chlorine dioxide ^{at 70 ° C. for 3 hours.} The lightness and inversion were measured after treating the wood pulp with sulfur dioxide for 5 minutes. The viscosity of the wood pulp was also measured. D. A 12.5 g sample of the oxygenated wood pulp was subjected to three rapid bleaching stages, each lasting 10 minutes, each with vigorous agitation:

Level 3: 1.0% chlorine dioxide, 4%, consistency,

Temperature 70 ⁰ C. Level 4: 0.5% sodium hydroxide, 4% consistency,

Temperature 6O ⁰ C. Level 5: 0.3 ",, chlorine dioxide, 4% consistency,

Temperature 70 ⁰ C.

The brightness and transformation of the wood pulp after 5 minutes of treatment with Sulfur dioxide and the brightness and transformation of a wood pulp without such treatment would be measured.

E. In stage 3, 1% chlorine dioxide was mixed with 12.5 g of wood pulp, which had a consistency of 12%, at 70 ^° C. for 3 hours. The brightness after treatment with sulfur dioxide for 5 minutes and the brightness conversion were then measured.

In the fourth Srufe the wood pulp, which had a consistency of 12% was extracted with 0.5% sodium hydroxide I ^1/2 hours at 6O ⁰ C. In stage 5, the wood pulp was treated with a consistency of 12% with 0.3% chlorine dioxide for 3 hours at 70 ° C. The brightness after the treatment with sulfur dioxide, the brightness conversion and the viscosity were then measured. The ratios of the bleaching sequences are shown in Table V.

Table V

sample

Chlorine used in the first stage. Used in the second stage

Sodium hydroxide

Oxygen treatment temperature .. Permanganate number after the second stage

Viscosity after the second stage

Brightness after the third level

(SO ₂ -treated wood pulp)

Brightness reversal after the third stage brightness (SO ₂ -treated pulp) after

the fifth stage

Brightness reversal (SO _{2 -treated}

Pulp) after the fifth stage

Brightness, untreated pulp, after

the fifth stage

Lightness inversion (untreated pulp)

after the fifth stage

Viscosity after the fifth stage

5.0%

3.0% 150 ° C

1.0 11, OcP 6.0%

3.0%
150 ⁰ C

0.85
10.7 cP

5.0%

3.0%

: I43 ° C

0.65

13.7cP

90.4

1.5

92.6
0.7

12.5 cP

6.0%

3.0%

140 ° C

0.75

13, IcP

89.5
1.4

88.2
1.1

6.0%

3.0%

130'C

0.85

15, IcP

90.3
1.9

92.8
1.0

12.65cP

It can be seen that Example 6 was carried out on the concentrated chlorine. The sodium hydroxide and 1.0% treatments a brightness of 90 after level 3 50 magnesium carbonate were the chlorine-treated can be obtained. Pulp, which had a consistency of 7% while

Added 3 minutes with vigorous hand stirring. the

Example 7 Oxygen treatment was carried out at a pressure of

11.2 at, with preheating at a

A sulfate wood pulp obtained from conifers with a pressure of 6.3 atm. In four of the bleaching processes it had been (mainly spruce and balsam fir)
and which had a permanganate number of 18.4

subjected to five separate multi-stage bleaching processes. The initial chlorinations were made as in a treatment with chlorine dioxide was used in a third stage. The key figures of the bleaching treatments are given in Table VI below.

Table Vl A. B. C. D. E. sample 6.0%
3.0%
147 C 5.0%
3.0%
144 C 6.0%
3.0%
140 C 5.0%
3.0%
140 C 6.0%
3.0%
135 C Chlorine used in stage 1
Applied in level 2
Sodium hydroxide Oxygen treatment temperature.

sample

Preheating time (min)

Time of oxygen treatment

11.2 at (min)

Permanganate number after the second stage Viscosity after the second stage (cP) .. Applied in the third stage

Chlorine dioxide

Brightness after the third level

Brightness inversion after the third level Viscosity after the third level (cP) ..

continuation

14th

20th

1.0 11.8

12th

10

1.8
15.8

1.0
90.7

1.7
13.3

12th

10
1.5
15.9

1.0
90.45

1.75
13.4

1.7
18.3

1.0
90.0

2.1
15.4

2.4
17.9

1.0
90.3

1.9
15.3

Example 8

A sulfate wood pulp obtained from conifers (mainly spruce and balsam fir) and having a permanganate number of 18.4 was subjected to six separate three-step bleaching processes. Samples of the wood pulp weighing 52.5 g (dried in the oven) were treated after washing to a consistency of 3% with 10 ml of 2% ammonium chloride solution and 5 to 6% chlorine. The chlorine treatment was carried out at room temperature for 10 minutes with stirring. The wood pulp was then washed twice with 3 liters of water. To the wood pulp, 1.0% magnesium carbonate and 3.0% sodium hydroxide were then added while stirring for 3 minutes. The wood pulp was then placed in an autoclave and preheated under an oxygen pressure of 6.3 atm, followed by treatment under an oxygen pressure of 11.2 atm for 30 or 20 minutes. In a third stage, the wood pulp, which had a consistency of 12%, was ^{treated with 1.0% chlorine dioxide at 70 °} C. for 3 hours. The plates for the determination of brightness were made using a treatment with sulfur dioxide. The indices of the bleaching processes are given in Table VII.

sample

Chlorine used in stage 1

Sodium hydroxide applied in stage 2

Preheating time (min)

Oxygen treatment temperature .. Oxygen treatment time (min) ...

Permanganate number according to level 2

Level 2 viscosity (cP)

Level 3 brightness

Holiness Reversal

Table VII A. B. C. D. E. F. 5.0% 6.0% 5.0% 6.0% 5.0% 6.0% 3.0% 3.0% 3.0% 3.0% 3.0% 3.0% 4th 8th 2 5 4th 4th 130C 130'C 120'C 120 ° C 110 C 110 C 30th 30th 30th 20th 30th 30th U 0.85 1.3 1.35 1.4 1.15 18.1 17.4 19.1 20.03 20.0 20.0 88.6 89.9 88.6 89.4 89.0 89.7 1.5 1.3 1.6 1.6 1.5 1.8

Example 9

A sulphate wood pulp obtained from conifers (mainly spruce and balsam fir) and which had a permanganate rating of 18.4, underwent six separate three-step bleaching processes subject.

In stage 1, the wood pulp, which had a consistency of 3%, was used for 10 minutes at room temperature 0.1 "" ammonia and 5 or 6% chlorine treated.

In step 2, the wood pulp 1.0 ° _o magnesium carbonate and varying amounts of sodium hydroxide were added, after which the wood pulp then stirred for 10 minutes before it was introduced into an autoclave of 140 ⁰ C. The wood pulp was first preheated under an oxygen pressure of 6.3 atm

and then treated for 30 minutes under an oxygen pressure of 11.2 atm.

In stage 3, the wood pulp, which had a consistency of 12%, was treated with 1.0% chlorine dioxide for 3 hours treated for a long time at 70 ° C. The permanganate number and

«3 the viscosity of the wood pulp were after completion of Step 2 was determined, and the brightness was measured after the completion of Step 3. The key figures a the bleaching procedures are shown in Table VIH.

Table VIII

sample A. B. C. D. E. F. Chlorine used in stage 1
Sodium applied in stage 2
hydroxide 5.0%
2.5%
1.6
11.9
85.05 6.0%
• 2.5%
2.0
16.0
89.0 5.0%
2.0%
1.3
15.6
86.6 6.0%
2.0%
1.8
88.75 5.0%
1.5% *)
1.3
85.4 6.0%
1.5% *}
2.0
86.1 Permanganate number after level 2
Viscosity after level 2 (cP)
Brightness after level 3

*) pH of the extraction liquids about 6.0.

Example 10

A sulphate wood pulp obtained from conifers (mainly spruce and balsam fir) and which had a permanganate number of 18.4 subjected to a three-stage bleaching treatment, with a successive treatment with chlorine dioxide and chlorine occurred in the first stage.

1. Two 52.5 g (oven-dried) pulp samples with a consistency of 3 "/" were first treated with chlorine dioxide (0.4 g, 0.48 g) at room temperature and then with chlorine (1.62 g , 1.89 g) corresponding to 5 and 6% chlorine respectively The samples were washed twice with 3 liters of water and divided into 17.5 g (oven-dried) portions.

2. For each of the six 17.5 g samples

3.0 % sodium hydroxide and 1% magnesium carbonate were added. Each portion was placed in an autoclave and heated for 1 to 4 minutes under an oxygen pressure of 6.3 atm and then for 10 minutes under an oxygen pressure of 11.2 atm at various temperatures. The wood pulp was then washed and the permanganate number and viscosity were measured.

3. The wood pulp, which had a consistency of 12 ", was treated with 0.6 "chlorine dioxide at 70 ° C. for 3 hours. The pulp was then washed. Before brightness measurements were made, the pulp was treated with sulfur dioxide. The brightness inversion and viscosity were also measured. The key figures of the bleaching process are in Table IX shown.

Table IX

sample

A. B. C. D. E. 5.0% 6.0% 5.0% 6.0% 5.0% 130 "C 130 ° C 120 "C 120 ° C 110 ° C 1.3 1.2 1.2 1.1 1.4 21.7 21.4 22.0 21.4 22.9 90.4 89.8 90.4 90.5 90.0 2.0 1.9 1.9 1.6 1.9 19.5 19.0 19.7 18.6 19.9

Chlorine-containing compound added in stage 1 (as chlorine equivalent)

Oxygen treatment temperature.

Permanganate number according to level 2

Level 2 viscosity (cP)

Level 3 brightness

Brightness reversal after level 3

Level 3 viscosity (cP)

6.0%
HO-C

1.3

22.6

90.0

1.8

20.2

Example 11

In Examples 11 to 18, the cost of chemicals used in bleaching the wood pulp as a criterion for the effectiveness of the bleaching process taken. The calculations were based on 1 ton of oven dried (OD) material and on 100% yield based. The cost of each chemical was as follows:

Chlorine 3.25 c / lb

Chlorine dioxide 20.0 c / lb

Sodium hydroxide 3.25 c / lb

Sulfur dioxide 2.8 c / lb

A sulphate wood pulp obtained from conifers (mainly spruce and balsam fir) and which has a kappa number of 28.0 and a viscosity of 35.0 c.p. s. became the conventional one Bleaching sequence C-E-D-E-D, a modification of the same (DC) -E-D-E-D and the sequence chlorination, alkaline oxygen treatment, chlorine dioxide treatment, C-O-D, subjected.

Sequence DEDED
Chlorination

Three samples of 100 g each of a pulp with a

Consistency of 3.0% was found with 4.5%, 5.5% and

6.5% chlorine containing 0.1% chlorine dioxide while

chlorinated over a period of 10 minutes at room temperature.

Alkali extraction

The chlorinated pulp, which had a consistency of 12% to, was treated with 4.0% sodium hydroxide during 1 V? Extracted hours at 60 ° C.

Chlorine dioxide treatment

The pulp, which had a consistency of 12 ", was was treated with 0.6 "" chlorine dioxide for 3 hours at 70 ° C.

Alkali extraction

Chlorine dioxide treatment

The pulp, which had a consistency of 12 " _(J. Was extracted with 0.4" sodium hydroxide 1 ¹ I for ₂ hours at 60 ° C.

Chlorine dioxide treatment

The pulp, which had a consistency of 12 "", was mixed with 0.25 "" chlorine dioxide for 3 hours 70 ° C treated.

The pulp metrics and the cost of the chemicals are summarized in Table X.

The pulp, which had a consistency of 12 '! ,, was treated with 0.75 ',' ,, chlorine dioxide for 3 hours at 80 ° C.

The results of the two bleaching tests are given in Table XII.

Table XII Final brightness

End
bright
speed Tabel X Costs. O. D.
unbleached,
S. Chlorine concentrations
tration. % 87.1
89.6
90.4 Final light
reversal Final viscosity.
cP 9.88
10.54
11.19 4.5
5.5
6.5 3.2
3.2
3.1 25.6
26.7
27.2

90.1
89.7

Final brightness inversion

2.1
2.0

Final viscosity, cP

22.0 22.5

Costs, O. D., unbleached, p

7.79 7.79

(DC) - E - D - E - D sequence

The first stage of this sequence consisted of treating the wood pulp to a consistency of 3 ',' ,, exhibited, with chlorine dioxide for 5 minutes Room temperature and a subsequent treatment for 5 minutes with chlorine at room temperature, the reaction mixture was then left to stand at room temperature for 50 minutes. That The reaction mixture was stirred throughout the stage.

The ones used in the following stages -E-D-E-D Conditions were the same as for the sequence C-E-D-E-D.

The results of the bleaching tests are shown in Table XI.

Table XI

Chloride

dioxide-

salary, %

0.61
0.76

Chlorine content,

2.4
3.0

0.915 3.6 91.4

Final brightness

85.4
90.0

Final light

ability

reversal

3.2
3.0
2.6

Final viscosity, cP

29.9
27.3
27.0

Cost, OD.,
unbleached. S.

10.55
11.59
12.61

Calcium hydroxide as base chlorination

Four 100 g pulp samples, which had a consistency of 3 "", were treated with 4.0 "" chlorine, containing 0.1% chlorine dioxide, treated for 10 minutes at 20 ° C.

Oxygen treatment

The pulp, which was 3% consistency, was Treated with various amounts of calcium oxide and with magnesium oxide or magnesium carbonate offset. The pulp was then subjected to an air pressure of 14 atm for 10 minutes in a reactor, with stirring.

The pH of the oxygenated slurry was then adjusted to 3.0 by the addition of sulfur dioxide. The slurry was then filtered and diluted to a consistency of 1.0%; the pH was increased to a value of 8.0 by adding lime water.

Chlorine dioxide treatment

The pulp, which had a consistency of 12%, was mixed with 0.65% chlorine dioxide for 3 hours at 80 ° C treated.

The results of four bleach runs are shown in Table XIII.

C-O-D sequence

In this sequence either sodium hydroxide or calcium hydroxide was used as the base in the oxygen stage used.

Sodium hydroxide as the base

Chlorination

Two 100 g samples of the wood pulp, one Consistency of 3 "" was mixed with 4.0 "" chlorine containing 0.05 "" chlorine dioxide "for 10 minutes Treated at room temperature.

Oxygen treatment

The chlorinated pulp, which had a consistency of 3 "", was treated with 3.0 "" sodium hydroxide and then exposed to an air pressure of 14 atm ^{at 130 ° C. for 10 minutes while stirring.}

Table XlII

5 ° train
set
Lime.
% Use eggs
Additive. % End
bright
speed Final light
kcits-
reverse end
viscosity.
cP ⁵⁵ 2.8 MgO
0.5 86.8 1.3 22.6 3.5 MgO
0.5 90.2 1.9 19.1 6o 2.8 MgCO ₃
1.0 86.2 1.9 22.4 3.5 MgCO,
1.0 89.8 1.7 19.7

Koslcn, O. [)., Un-

bicichl, S.

6.20 6.30 6.20 6.30

It should be noted that the mixtures of lime and magnesium additives that act as reagents are used in dolomitic limestone and dolomitic quicklime.

Example 12

In the bleaching procedure of this example (C-O-D) calcium hydroxide was used as the base with no magnesium added used.

Chlorination

Three 100 g samples of the sulfate wood pulp from example 1, which had a consistency of 3.0 "", were mixed with 4.0 ', "" chlorine, which contained 0.1% chlorine dioxide, at 20 ^° C. for 10 minutes treated.

Oxygen treatment

The pulp had a consistency of 3.0%, was treated with different amounts of lime (calcium oxide) _S i and then at exposed in a reactor under stirring for 10 minutes at 130 ⁰ C at an air pressure 14 days.

The pH of the slurry was then adjusted as described in the last section of Example 11.

Table XIV

Added
Lime. %

Final closure

78.7
86.1
90.2

Final brightness

2.1
1.7
2.1

Final viscosity,
cP

21.3
19.3
• '5.4

Costs. O. D.

unbleached,

6.20
6.30
6.40

Example 13

20th

This example concerns the five-step bleaching sequence C-O-D - E-D, in which either sodium hydroxide or calcium hydroxide is used as the base in the oxygen treatment step.

Sodium hydroxide as the base
Chlorination

Six samples of the sulfate wood pulp, weighing 10O g, which were used in Example 11 and which had a consistency of 3%, were ^{treated with 4.0% chlorine containing 0.1% chlorine dioxide at 20 °} C. for 10 minutes.

Oxygen treatment

In Samples 1 and 2, the pulp, which had a consistency of 3%, was made with 3.0% sodium hydroxide treated. For samples 5 and 6, in which the pulp also had a consistency of 3%, treatment with 3.0% sodium hydroxide and 1.0% dolomitic quicklime took place. For samples 3 and 4 the consistency was 7%; these samples were treated with 3.0% sodium hydroxide. All samples were stirred in a reactor for 10 minutes at 130 "C with air under a pressure of 14 at.

Chlorine dioxide treatment

The pulp, which had a consistency of 12%, was mixed with 0.45% chlorine dioxide for 3 hours at 80 ° C

(Samples 1, 3 and 5) or treated with 0.30% chlorine dioxide (Samples 2, 4 and 6).

Alkali extraction

The pulp had a consistency of 12% was treated with 0.3% sodium hydroxide at 6O ⁰ C 1 ¹ Z ₂ hours.

Chlorine dioxide treatment

The pulp, which had a consistency of 12%, was mixed with 0.20% chlorine dioxide for 3 hours at 80 ° C (Samples 1,3 and 5) or 0.15% chlorine dioxide (samples 2, 4 and 6).

The results are shown in Table XV.

Table XV

Chlorine dioxide treatment

The pulp had a consistency of 12%, was treated with 0.65% chlorine dioxide for 3 hours at 8O ⁰ C. The results of the three experiments are shown in Table XIV.

sample end
light wedge Final light
circumspection
change Final viscosity,
cP Cost, OD,
unbleached.
J 1 90.1 2.0 21.6 7.95 2 88.5 2.1 22.8 7.15 3 91.0 1.9 18.3 7.95 4th 89.7 1.7 19.2 7.15 5 91.4 1.8 21.6 7.95 6th 90.1 1.8 22.1 7.35

Calcium hydroxide as a base

Chlorination

Two 100 g samples of the sulphate wood pulp,

which was used in Example 11 and which has a consistency of 3.0% were mixed with 4.0% chlorine containing 0.1% chlorine dioxide for 10 minutes at 20 ° C

treated.

Oxygen treatment

The pulp, which had a consistency of 3%, was treated with two mixtures of calcium oxide and magnesium oxide (2.8 g CaO, 0.5 g MgO and 3.5 g CaO, 0.5 g MgO), as shown in the table XVI is shown. The pulp was then in a reactor at 130 ⁰ C for 10 minutes while stirring an air pressure of. 14 at exposed.

The pH of the oxygen treated pulp was then adjusted by two separate methods:

(a) Trials 1 and 3: 15g portions of each sample were acidified to a consistency of 1.0% with sulfur dioxide to a pH of 3.0, and after filtering off and diluting to a consistency of 1.0%, the pH further adjusted to pH 8.0 with lime water.
(b) Trials 2 and 4: 15g portions of each sample were slurried to a consistency of 1.0% and adjusted to a pH of 8.0 by adding sulfuric acid.

Chlorine dioxide treatment

All servings were then at a consistency of 12% with 0.4% chlorine dioxide for 3 hours 80 ° C treated.

Alkali extraction

All portions were then washed with 0.25% sodium hydroxide at a consistency of 12 '; extracted for 3 hours at 80 ⁰ C!.

Chlorine dioxide treatment

All portions were then treated with 0.2% chlorine dioxide for 3 hours at SO'C at a consistency of 12%.
The results are shown in Table XVI.

Table XVI

attempt
No. Added
Lime, g NaOH Aauiva-
lent of lime,
% Example 14 MgO, g Unanimity Final wedge
u inkehr
—_ Final viscosity,
cP Cost, O. D.,
unbleached,
S. E-D sequence 1 2.8 4.0 0.5 90.7 1.9 22.1 6.16 2 7.8 4.0 0.5 92.2 1.6 18.9 6.26 3 3.5 5.0 0.5 89.9 1.8 22.1 6.16 4th 3.5 5.0 0.5 90.8 1.5 18.9 6.26 C-O-D-

A sulphate wood pulp made from New Zealand softwood that was unbleached properties

Kappa number 23.8

Viscosity 34.7

was through a conventional C - E - D - E - D sequence and through the sequence C-O-D-E-D bleached.

C-E-D-E-D sequence chlorination

The pulp was left at 3% consistency with 4.24% chlorine containing 0.1% chlorine dioxide for 45 minutes treated for a long time at 25 ° C.

Alkali extraction

The pulp had a consistency of 12%, was treated 1V _{for 2} hours with 2.5% sodium hydroxide at 6O ⁰ C.

Chlorine dioxide treatment

The pulp, which had a consistency of 12%, was mixed with 0.9% chlorine dioxide for 3 hours at 70 ° C

treated. . ,.

Alkali extraction

The pulp had a consistency of 12%, was / treated with 0.5% sodium hydroxide 1 'for 2 hours at 6O ⁰ C.

Chlorine dioxide _{treatment J0}

The pulp, which had a consistency of 12%, was ^{treated with 0.5% chlorine dioxide at 70 °} C. for 3 hours.

The bleached pulp had a brightness value of 91 and the chemical cost was $ 11.07 / ton.

3P

35

40

45 chlorination

Four 100 g samples of the pulp with a consistency of 3% were given two concentrations of chlorine of 3.5% (samples 1 and 3) and 3.0% (samples

2 and 4), each chlorine reagent containing 0.1% chlorine dioxide, treated for 10 minutes at room temperature.

Oxygen treatment

The pulp was made at a consistency of 7% with sodium hydroxide or lime, the magnesium oxide at the concentration shown in Table XVII. The pulp was then in one Reactor of 130 ° C exposed to an air pressure of 14 atm for 10 minutes with stirring.

Chlorine dioxide treatment

The pulp was at a consistency of 12 "with Treated 0.4% chlorine dioxide for 3 hours at 80 ° C.

Alkali extraction

The pulp to a consistency of 12% was treated with 0.3% sodium hydroxide for _{2 hours at 60 ° C.}

Chlorine dioxide treatment

The pulp was made with a consistency of 12%

Treated for 3 hours at 8O ⁰ C with 0.25% chlorine dioxide.

In the case of samples 2 and 4, the products of the oxygen treatment were based on sulfur dioxide adjusted to a pH of 3.0, filtered and diluted to a consistency of 1.0% and again with lime water adjusted to a pH of 8.0. These products then underwent chlorine dioxide treatment as described above subject.

The results of the bleaching are shown in Table XVII.

Table XVII Oxygen treatment conditions CaO MgO Final brightness Final brightness
reversal Final viscosity,
cP Cost, OD,
unbleached,
4 ' sample NaOH - - 2.5 2.8 0.5 91.2 1.3 18.9 7.30 1 - - - 90.2 1.5 21.2 6.07 2 2.5 2.8 0.5 91.1 1.3 18.7 6.97 3 89.0 1.8 20.8 5.74 4th

Example 15

l 947

The pulp was treated with a consistency of 7% in a reactor and at an air pressure of 14 atm with 2.0% sodium hydroxide. The temperature was ^{raised to 130 °} C. with stirring and held at this value for 10 minutes.

Chlorine dioxide treatment (level 3)

The pulp was at a consistency of 12% chlorine dioxide; treated (Sample% 1,0,6 2,0,4 sample "/") for 3 hours at 80 ⁰ C.

Alkali extraction

The pulp was treated with sodium hydroxide (sample 1, 0.5%; sample 2, 0.3%) at 60 ^° C. for _{2 hours at a consistency of 12 ".}

Chlorine dioxide treatment (level 5)

The pulp was treated with 0.25% chlorine dioxide for 3 hours and at 80 ^{° C. at a consistency of 12%.}

The results are given in Table XVIII.

Table XVIII

sample Brightness at
Level 5 Brightness
reversal at
Level 5 viscosity
at level 5,
cP Costs. O. D_
unbleached.
S. 1
2 90.1
90.5 4.6
42 26.4
31.2 6.22
6.66

Alkali extrusion

10

A sulphate wood pulp made from a hardwood which has the bleached properties' from

Kappa number 15.5

Viscosity 57.3

was bleached by the two sequences C-O-D-E-D and C-E-D-E-D. The oxygen treatments were carried out using an improved reactor, the one heavy load on the reactor, more efficient heating and agitation of the pulp, and greater Uniformity and reproducibility of the results allowed. The reactor was used in Examples 15-18.

C-O-D-E-D sequence

Chlorination

Two 100 g samples of the pulp were at a consistency of 3.0% with 2.4% chlorine (sample 1) and 3.0 "" chlorine (Sample 2) at room temperature for 10 minutes.

Oxygen treatment

The pulp had a consistency of 12%, was treated 1V for ₂ hours at 6O ⁰ C with 2.0% sodium hydroxide.

Chlorine dioxide treatment

The pulp had a consistency of 12%, was treated for 3 hours at 8O ⁰ C with 0.7% chlorine dioxide.

Alkali extraction

The, pulp having a consistency of 12%, was treated 1V for ₂ hours at 6O ⁰ C with 5.3% sodium hydroxide.

Chlorine dioxide treatment (level 5)
The pulp had a consistency of 12%, was treated for 3 hours at 8O ⁰ C with 0.3% chlorine dioxide.

The results of the bleaching tests are shown in Table XIX.

Brightness at
Level 5 Table XIX viscosity
at level 5,
cP Cost, O. D
unbleached,
i sample 90.2
90.4 Brightness
reversal at
Level 5 31.6
29.3 7.32
7.64 1
2 6.0
6.3

C-E-D-E-D sequence

Chlorination

Two 100 g samples of the pulp were taken with a consistency of 3% with chlorine (sample 1, 3.0%; sample 2, 3.5%) for 10 minutes at room temperature treated.

It can be seen that the same brightness value is obtained in both bleaching sequences, but that the Sequence C-O-D-E-D gives improved brightness inversion with lower bleaching costs.

Example 16

Two samples of a sulphate wood pulp showing the unbleached properties:

Sample A kappa number 83.4

Sample B Kappa number 59.4

were the conventional bleaching sequence C-E-D-E-D and individually the oxygen bleaching sequence C-O-C / D-E-D and subject to C-O-C-O-D.

C-E-D-E-D sequence

Chlorination

The pulp was treated with chlorine at 3% consistency at room temperature for 45 minutes (Sample A, 15.6%; Sample B, 11.0%).

Alkali extraction

The pulp with a consistency of 12% IV was treated with sodium hydroxide (sample A. 10.0%; sample B, 7.0%) at 60 ^° _{C. for 2 hours.}

Chlorine dioxide treatment

The pulp was treated with a consistency of 12% for 3 hours at 80 ^° C. with 1.0% chlorine dioxide.

Alkali extraction

The pulp was extracted to a consistency of 12 "1" for ₂ hours at 60 ° C. with 0.5 "" sodium hydroxide.

509 626/108

60

26th

Chlorine dioxide treatment (5th stage)

The pulp at a consistency of 12% 3 hours treated with 0.5 "chlorine dioxide at 80 ° C for a long time.

The results of the bleaching are given in Table XX.

Chlorine dioxide treatment (5th stage)

Table XX

sample

A.
B.

brightness at level 5

89.2
90.0

Brightness

reversal at

Level 5

4.2
3.9

viscosity

at level 5.

cP

32.0 20.3

Costs. O.O.,

unbleached,

23.20 18.20

The pulp, which had a consistency of 12%, was heated for 3 hours at 80 ° C with two different: Chlorine dioxide amounts, once with 0.5% and once with 0.75%, treated.

The pulp was then treated with sulfur dioxide before the final brightness values were determined The results are shown in Table XXII

Table XXII

Chlorine dioxide concentration j in stage 5

0.5%
0.75%

Final brightness

90.2
91.4

Final holy

kcils-

reverse

2.2
2.2

Final viscosity, c P

23.9
23.0

Costs. O. D.

unbleached,

13.70 14.70

Example 17

C - O - C / D - E - D sequence - sample A chlorination

The pulp was at 3% consistency at room temperature for 45 minutes with 10.0 "" chlorine treated.

Oxygen treatment

The pulp was made to a consistency of 7 "" for 30 minutes at 130 ° C and at air pressure of 14 at with stirring with 6.0% sodium hydroxide

treated. had, a conventional C-E-D-E-D-

Chlorine dioxide / chlorine treatment, bleaching sequence that resulted in a final strength of 95.

^{3 B} 30 and a C - O - D oxygen bleaching sequence

The pulp was tossed to a consistency of 12 ". For 3 hours at 50 ° C with a mixture of 1.1 ""

Treated with chlorine and 0.1% chlorine dioxide. c-Ct-D A hf I

Alkali extraction

A sulphite wood pulp containing the following unbleached properties

Kappa number 9 _t (

Viscosity? 4 (

The pulp was extracted with a consistency of 12 ",, IV2 hours at 6O ⁰ C with 1.5" ,, sodium hydroxide.

35 chlorination

Two 100 g samples of the pulp were taken with

«. _Λ . l ^m " ^Kon " stoiz of 3% at room temperature 10 minutes

Chlorine dioxide treatment (5th stage) p ^{Uten lam} J ^m H Chlorine treated: Sample 1, 2.0%:

The pulp was made with a consistency of 12 "" ° ^{be2 2} ' ⁵ °° ·
3 hours at 80 ° C with 0.75% chlorine dioxide

r \ - η. .i oxygen treatment

The results of the bleaching are given in Table XXI r>,> Pni u,

shown. ^{υιε pulp} samples which have a consistency of 7% on Table XXI and ⁵ '? 8 ^% ° ρ ", ^{treated with 2} ' ^{0% sodium hy d} ^ xyd (sample 1) table XXI and 2.8 calcium oxide (sample 2)

- S if ^Pul P ^en samples were then stored in a £ n! τ agitated ^{stirring for 10} minutes at 130 ° C exposed to an air pressure of 14 at.

brightness at level 5

89.7

Brightness reversal at Level 5

Viscosity at

Level 5.

cP

35.8

Cost, O. D ..

unbleached.

15.70 sample B

C-O-C-O-D sequence

Chlorination

The pulp, which had a consistency of 3%, was kept at room temperature with stirring for 20 minutes treated with 5.0% chlorine for a long time.

Oxygen treatment **

The pulp, which had a consistency of 7%, was treated with 4.0% sodium hydroxide and then with stirring in a reactor for 10 minutes at a temperature of 130 ° C. and an air pressure of at exposed.

The third and fourth stages were a repetition of the first two stages.

Chlorine dioxide treatment
the one

from

^ ^e3Sta
treated

^the were ^then prepared ^with sulfur dioxide over ^{ie "el"} gk "tstafeln, e, _m Table ΧΧΙΠ shown

Table XXIU

Sample 1

Final brightness

94.2
94.9

Mjhenig kcit reversal

1.6
1.4

F. final viscosity cP

18.3
17 8

Costs. OD .. unbleached

4.00

Example 18 Table XXIV brightness

at level 2

62.4
61.8

Image brightness

84.1
83.3

Final brightness inversion

13.5
18.1

Costs. O. D., unbleached. S.

18.30
18.30

It can be seen that the use of oxygen bleach according to the invention gives a bleached wood pulp having a brightness equal to that is made by a conventional method

A semi-chemical neutral sulphite pulp based on sodium, which has the unbleached properties

Kappa number 91.0

Chlorine requirement 17.0%

was subjected to the C-O-D bleaching sequence.

Chlorination

Two 35 g samples of the pulp were obtained at 3% consistency with 17.0% chlorine at room temperature Treated for 40 minutes.

Oxygen treatment

The pulp, which had a consistency of 7%, was treated with 5.0% sodium hydroxide and then exposed to an oxygen pressure of 11.2 atm at 130 ° C. for 30 minutes with stirring in a reactor.

Chlorine dioxide treatment

The pulp, which had a consistency of 12%, was treated with 1.0% chlorine ^{at 70 ° C. for 3 hours.}

The results of the bleaching are shown in Table XXIV.

but the cost of chemicals is lower.

Example 19

Two samples of sulfate wood pulp obtained from conifers became the following Subject to bleaching sequence: chlorination, treatment ίο with alkaline peroxide under pressure, treatment with chlorine dioxide, C-P-D. A third sample was used as a comparison. The terms of the treatments were as follows:

Chlorination

The wood pulp was in aqueous suspension at a consistency of 3% with 4.0% chlorine and 0.1% Treated chlorine dioxide at room temperature for 10 minutes.

Alkaline peroxide treatment

The chlorine-treated pulp, which had a consistency of 3%, was mixed with the in Reagents shown in Table XXV at a temperature of 130 ° C in a sealed reaction container treated. During the treatment, the pressure reached a maximum value of 3.36 at. The pressure increase was a result of the heating of the contents of the reaction vessel.

Chlorine dioxide treatment

The pulp, which had a consistency of 12%,

was treated with various percentages of chlorine dioxide, which are shown in Table XXV, for 3 hours at 80 ^{° C.} At this stage the first two samples were each divided into two portions.

The results of the bleaching sequence are shown in Table XXV. It can be seen that alkaline peroxide is below Pressure is an effective source of oxygen for bleaching.

sample % Chlorine Table XXV 1 0.5 2 0.65 3 step % Chlorine dioxide 89.9 91.9 comparison % Sodium hydroxide 4.0 1.6 4.0 1.4 4.0 1 % Hydrogen peroxide 0.1 18.8 0.1 183 0.1 % MgSO ₄ -7H ₂ O 5.5 4.0 5.5 2 % Na ₂ SiO ₃ (42 Be) 2.0 2.0 - Final pH (50%) - 1.0 - Permanganate number - 5.0 - brightness 10.3 9.4 10.8 Viscosity cP 2.0 1.5 3.2 % Chlorine dioxide 63.2 68.5 45.3 brightness 17.0 20.3 29.6 Brightness inversion 0.65 0.55 - 3 Viscosity, cP 90.9 90.0 - 1.4 1.6 - - - -

Claims (2)

Patent claims: 1. Process for bleaching lignocellulosic material, using sulphate, sulphite or semi-chemical neutral sulphite wood pulp including the following initial work steps: (1) Treatment of the lignocellulosic material in an aqueous suspension of a consistency of 3 to 7 percent by weight at room temperature with a chlorinated reactant with a chlorine equivalent of 2 up to 8 percent by weight for 10 to 60 minutes and (2) contacting the chlorine-treated lignocellulosic material with 2 to 3 percent by weight of an alkaline medium, whereupon the alkaline material in aqueous suspension has a consistency of 3 to 12 percent by weight with oxygen or an oxygen-containing one Gas is treated under a pressure of 2.1 to 14 kg / cm ² at a temperature of 100 to 200 C for 10 to 30 minutes and the lignocellulosic material is washed with water after completion of work step (1) and / or (2), characterized that the chlorine-containing reaction means of work step (1) consists of a mixture of chlorine and chlorine dioxide or of chlorine dioxide with subsequent chlorine treatment without intermediate washing or of hypochlorite with subsequent chlorine treatment. 2. The method according to claim 1, characterized in that that used in work stage (2) alkaline medium made of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate or potassium hydroxide.