CN111979818A - Sulfate wood pulp short-procedure ECF bleaching process X/Z/D-EOP-D or X/D/Z-EOP-D - Google Patents

Abstract

The invention belongs to the technical field of papermaking, and relates to a short-program ECF bleaching process X/Z/D-E _OP -D or X/D/Z-E _OP -D of kraft wood pulp, and the steps are as follows: (1) sequential bleaching ( (2) Strengthening Alkali extraction (E _OP ): The sequentially bleached pulp is subjected to hydrogen peroxide and oxygen-enhanced alkaline extraction treatment to further dissolve the residual lignin in the pulp; (3) Supplementary bleaching (D): The above pulp is subjected to dioxide oxidation Chlorine supplemental bleaching gave fully bleached pulp (88% ISO). Through the above bleaching treatment, pulp with higher brightness and strength properties is obtained, X/Z/D-E _OP -D or X/D/Z-E compared to the traditional D‑E _O ‑D‑D bleaching procedure The _OP ‑D bleaching procedure reduces one chlorine dioxide bleaching stage, reducing chlorine dioxide consumption by more than 30% and water consumption by more than 20% with the same final brightness.

Description

A short-program ECF bleaching process for kraft wood pulp X/Z/D-EOP-D or X/D/Z-EOP-D

technical field

The invention belongs to the technical field of papermaking, and in particular relates to a short-program ECF bleaching process X/Z/D-EOP-D or X/D/Z-EOP-D of kraft wood pulp.

Background technique

The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

The production and consumption level of paper and cardboard has become an important indicator to measure a country's economic development level and social progress. Although China has become the world's largest producer and consumer of paper products, the paper industry is faced with a shortage of fiber resources and a heavy load of environmental pollution. Therefore, low-carbon economy and green technology have become the themes of the development of the paper industry. Exploring clean and bleaching technology with low energy consumption and low pollution has always been a research hotspot of scientific and technological workers.

In order to meet the requirements of a circular, low-carbon, and green economic development model, and to solve the problems of high pulp production cost, poor paper quality and environmental pollution in the production process, many papermaking enterprises have gradually adopted traditional pulping and papermaking technology. Adopt cleaner and environmentally friendly pulping and bleaching technologies, such as elemental chlorine-free bleaching (ECF), total chlorine-free bleaching (TCF) and biological bleaching technologies. ECF bleaching technology uses ClO ₂ instead of traditional chlorine and hypochlorite, which significantly reduces environmental pollution, but the chlorine element in ClO ₂ bleach still causes harm to the environment.

SUMMARY OF THE INVENTION

In order to improve and solve the technical defects and deficiencies existing in the existing bleaching technology, the present invention provides a fast-growing eucalyptus light element-free chlorine bleaching process, that is, an elemental chlorine-free bleaching process (Z-ECF) containing ozone bleaching. In order to prepare high-brightness kraft pulp, on the premise of ensuring the physical strength properties of the kraft bleached pulp into paper, the amount of ClO ₂ bleaching agent and the amount of water used for pulp washing in the bleaching process are reduced.

The present invention is achieved through the following technical solutions: the following concentrations of the slurry involved are mass percentages unless otherwise specified; the dosages of the involved reagents and medicines, unless otherwise specified, are relative to the absolute dry pulp .

A first aspect of the present invention provides a short-program ECF bleaching process for kraft wood pulp, comprising:

The wood pulp after oxygen delignification is subjected to X/Z/D ₁ or X/D ₁ /Z sequential bleaching to obtain semi-bleached pulp;

Hydrogen peroxide- and oxygen-enhanced alkaline extraction treatment of sequentially bleached pulp;

Supplementary bleaching with chlorine dioxide D ₂ is performed on the pulp treated by the enhanced alkali extraction to obtain fully bleached pulp;

Wherein, in the X/Z/D ₁ or X/D ₁ /Z sequential bleaching, pulp washing is not performed between X, Z, and D ₁ bleaching.

The present invention adopts X/Z/D-EOP-D or X/D _/ Z-EOP-D bleaching treatment to obtain pulp with higher brightness and strength performance indexes. The Z/DE _OP -D or X/D/ZE _OP -D bleaching procedure reduces one chlorine dioxide bleaching stage, and with the same final brightness, the chlorine dioxide consumption is reduced by more than 30%, and the water consumption is reduced by more than 20% .

The second aspect of the present invention provides fully bleached pulp prepared by any one of the processes.

The high-brightness kraft pulp prepared by the above-mentioned ozone-containing element chlorine _- free bleaching process (Z-ECF) of the present invention reduces the ClO2 bleaching agent in the bleaching process under the premise of ensuring the physical strength properties of the kraft bleached pulp into paper. Dosage and pulp washing water consumption.

The third aspect of the present invention provides the application of the above-mentioned fully bleached pulp in the production of paper and paperboard.

Because the invention can reduce the amount of ClO ₂ bleaching agent and the amount of water used for pulp washing in the bleaching process on the premise of ensuring the physical strength properties of the sulfate bleached pulp into paper, it is expected to be widely used in the paper industry.

The beneficial effects of the present invention are:

(1) The present invention adopts X/Z/D-EOP-D or X/D/Z-EOP-D bleaching treatment to obtain pulp with higher brightness and strength performance indexes, which is compared with the traditional DE _O -DD bleaching procedure , X/Z/DE _OP -D or X/D/ZE _OP -D bleaching procedure reduces one chlorine dioxide bleaching stage, under the condition of the same final whiteness, the chlorine dioxide consumption is reduced by more than 30%, and the water consumption is reduced 20% or more.

(2) The method of the present invention is simple, low in cost, strong in practicability, and easy to popularize.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

A short-program ECF bleaching process of kraft wood pulp X/Z/DE _OP -D or X/D/ZE _OP -D, the steps are as follows:

(1) Pulp preparation: The wood chips are subjected to kraft cooking and then washed and screened to obtain natural pulp; then the natural pulp is subjected to oxygen delignification or enhanced deoxylignin treatment to obtain pulp.

(2) ECF bleaching: the above pulp is subjected to X/Z/D ₁ -E _OP -D ₂ program bleaching, wherein X/Z/D ₁ or X/D ₁ /Z section is sequential bleaching, X, Z, No pulp washing is carried out between D bleaching, and pulp washing is carried out between X/Z/D ₁ or X/D ₁ /Z stage and E _OP stage and D ₂ stage.

Bleaching process technological conditions: X/Z/D ₁ or X/D ₁ /Z section: xylanase-assisted bleaching (X), technological conditions are: xylanase dosage 5～20U/g _pulp , pulp concentration 10～ 15%, pH=5～9, bleaching temperature 50～80℃, bleaching time 60～120min; after bleaching, the pulp does not need to be washed directly for ozone bleaching (Z), the process conditions are bleaching temperature 50～80℃, pulp consistency 10～15%, pH=2～4, bleaching time 0.5～5min, ethylene glycol dosage 1～3%, ozone dosage 0.2～1.5%; after bleaching, the pulp can be directly bleached with chlorine dioxide without washing (D ₁ ), the process conditions are: ClO ₂ dosage 0.2-1.0%, pulp concentration 10-15%, pH=2-4, bleaching temperature 50-80 ℃, bleaching time _30-180min ; The process conditions are: H ₂ O ₂ dosage 1-3%, slurry concentration 10-15%, pH=11-12, oxygen pressure 0.4Mpa, temperature 80-90 ℃, alkali treatment time 30-60min; alkali treatment After the finished pulp is washed, the D ₂ stage bleaching is carried out. The process conditions are: the amount of ClO ₂ is 0.5-1.0%, the pulp concentration is 10-15%, pH=2-4, the bleaching temperature is 50-80°C, and the bleaching time is 30-180min; Since no intermediate washing is performed, the X/Z/D ₁ or X/D ₁ /Z section of the present invention has better strength performance indicators than ordinary XZD or XDZ bleached pulp.

Further, the specific method of the xylanase-assisted bleaching (section X) is: adjusting the pulp concentration to 10-15%, adjusting pH=5-9, maintaining the pulp temperature at 50-80°C, adding xylanase 5- 20u/g, stirring evenly for 60-120min. The study found that ozone and chlorine dioxide bleaching directly without washing after xylanase treatment is beneficial to the penetration of bleaching agents and the dissolution of lignin, which improves the bleaching efficiency of bleaching agents and improves the bleaching effect of pulp.

Further, the specific method of the ozone bleaching (Z section) is: after the pulp is treated with xylanase, adjust the pH value to 2.0-4.0, keep the pulp concentration at 10-15%, add 1-3% ethylene glycol , the bleaching temperature is 50-80 ℃, and the ozone bleaching is carried out with uniform stirring. The ozone dosage is 0.3-1.5%, and the bleaching time is 0.5-5min. The strong oxidative and bleaching properties of ozone are used to improve the bleaching efficiency and the whiteness stability of the pulp. , while reducing the environmental load.

Further, the specific method of chlorine dioxide bleaching (section D ₁ ) is: after the pulp is bleached by ozone, adjust the pH value to 2.0-4.0, keep the pulp concentration at 10-15%, and under the condition of 50-80 ℃, evenly Mixing and bleaching with chlorine dioxide, the amount of ClO ₂ is 0.2~1.0%, and the bleaching time is ₃₀ ~180min. Chlorine dioxide is _one of the main bleaching agents for pulp bleaching. Sequential bleaching, and the cooperation with the subsequent E _OP and D ₂ bleaching stages, the pulp obtained has high whiteness, good strength and little environmental pollution.

Further, the specific method of the hydrogen peroxide and oxygen-enhanced alkali treatment (E _OP section) is: after the pulp is bleached and washed with chlorine dioxide, the pH value is adjusted to 11-12, and the pulp concentration is kept at 10-15% , add 1-3% hydrogen peroxide, keep the oxygen pressure at 0.4Mpa and the temperature at 80-90 ℃, carry out alkaline hydrogen peroxide bleaching, the bleaching time is 30-60min; by adding hydrogen peroxide and oxygen in the alkali treatment process , which not only improves the whiteness of the pulp, but also reduces the amount of chlorine dioxide used in the subsequent bleaching process.

Further, the specific method of chlorine dioxide bleaching (section D ₂ ) is as follows: after the pulp is alkali treated and washed, the pH value is adjusted to 2-4, and the pulp concentration is kept at 10-15%, under the condition of 50-80 ℃ , stir evenly, and perform chlorine dioxide bleaching, the amount of ClO ₂ is 0.5-1.0%, and the bleaching time is 30-180 min. The residual lignin in the pulp is oxidized by chlorine dioxide bleaching (section D ₂ ), and the pulp whiteness is further improved.

Furthermore, papermaking is performed using the pulp after the above-mentioned bleaching treatment.

Another embodiment of the present disclosure provides a pulp paper-based material prepared by the above method. The paper-based material not only has better physical strength properties, but also has higher whiteness.

The present invention will be further described in detail below with reference to specific embodiments. It should be pointed out that the specific embodiments are intended to explain rather than limit the present invention.

In order to enable those skilled in the art to understand the technical solutions of the present disclosure more clearly, the technical solutions of the present disclosure will be described in detail below with reference to specific embodiments.

Determination of brightness: After pulp is decomposed by fiber decompression machine, it is copied into paper on Kaiser method sheet machine produced in Austria, and then measured with YQ-Z-48B brightness meter;

Folding endurance times: Measured with a MIT folding endurance tester made in China.

Burst index: measured with a burst tester produced by the Swedish company L&W.

Tensile index: measured with XLWA (B) intelligent electronic tensile testing machine made in China.

Other experimental methods not described in detail are conventional experimental methods in the art.

In the invention, xylanase-assisted bleaching, ozone, chlorine dioxide combined with hydrogen peroxide and oxygen-enhanced alkali treatment are used to bleach the pulp in the X/Z/D ₁ -E _OP -D ₂ bleaching sequence to obtain low ClO ₂ dosage and high brightness, high strength pulp. details as follows:

Comparative Example 1:

Proceed as follows:

(1) The cooking conditions are: the amount of alkali used is 21%, the liquid ratio is 1:5, the degree of sulfidation is 25%, the cooking temperature is 170 ° C, and a small gas release is carried out at 105 ° C, the heating time is 100min, and the holding time is 90min; Washed and screened to obtain unbleached kraft pulp.

(2) Oxygen delignification conditions are: adjust the concentration of unbleached kraft pulp to 10%, the amount of NaOH to be ₃ %, the amount of MgSO to be 0.6%, the oxygen pressure to be 0.6Mpa, the temperature to be 100°C, the holding time to be 60min, and then washing , to obtain pulp after oxygen delignification.

(3) ECF bleaching: D-Eo-DD four-stage bleaching procedure is performed on the pulp after oxygen delignification. D-stage chlorine dioxide bleaching, the process conditions are: pulp concentration 10%, total amount of ClO ₂ in the third stage 1.5-2.0%, pH = 2.0, bleaching temperature 60 ℃, bleaching time 30-60min; after washing the pulp, carry out EO The process conditions are: pulp concentration 10-15%, pH=11-12, oxygen pressure 0.4Mpa, temperature 80-90℃, alkali treatment time 30-60min; after bleaching, the pulp is washed.

(4) Papermaking: the uncolored pulp after eucalyptus kraft cooking, the pulp after oxygen delignification and the D-Eo-DD bleached pulp were beaten to 35°SR respectively, and then pulp fibers were decomposed in a fiber decompressor respectively, It is dispersed evenly, and it is made into a sheet with a basis weight of 60 g/m ² on a sheet former.

(5) The performance indexes of the obtained eucalyptus wood pulp after kraft cooking, the pulp after oxygen delignification and the D-Eo-D-D bleached pulp are shown in Table 1 below.

Table 1. Performance index of natural pulp after cooking of eucalyptus wood, pulp after oxygen delignification and bleached pulp of D-Eo-D-D

Example 1:

Proceed as follows:

(1) ECF bleaching: X/Z/DE OP-D or X/D/X/Z/DE _OP -D or X/D/ The ZE _OP -D three-stage bleaching program bleaches.

First perform xylanase-assisted bleaching (X), the process conditions are: xylanase dosage 10U/g _pulp , pulp concentration 15%, pH=5, bleaching temperature 55°C, bleaching time 60min; Ozone bleaching (Z) needs to be washed directly, bleaching temperature 55°C, pulp concentration 15%, pH=2, bleaching time 2min, ethylene glycol dosage 2%, ozone dosage 0.3%; after bleaching, the pulp does not need to be washed directly. Chlorine dioxide bleaching (D), the process conditions are: ClO2 dosage 0.5%, pulp concentration 15%, pH= ₂ , bleaching temperature 55°C, bleaching time 30min; after bleaching, the pulp is washed and then subjected to E _OP section treatment. The conditions are: H ₂ O ₂ dosage 1%, pulp concentration 10%, pH=11.5, oxygen pressure 0.4Mpa, temperature 90°C, alkali treatment time 60min; after alkali treatment, the pulp is washed and then bleached with chlorine dioxide. Process conditions It is as follows: the amount of ClO ₂ is 0.5%, the pulp concentration is 10%, pH=2, the bleaching temperature is 60°C, the bleaching time is 30min, and the pulp is washed after the bleaching. In X/Z/D sequential bleaching, the replacement of Z and D positions does not affect the bleaching results.

(2) Papermaking: beat the above-mentioned bleached pulp to 35°SR, then carry out pulp fiber decompression in a fiber decompressor to make it evenly dispersed, and make a paper with a basis weight of 60g/m2 ^on a sheet former Page.

(3) The performance indexes of the obtained X/Z/DE _OP -D or X/D/ZE _OP -D bleached pulp are shown in Table 2 below. The control group is the pulp after oxygen delignification and the pulp after four stages of D-Eo-DD. The pulp obtained after bleaching sequence, Example 1 is the pulp obtained after bleaching by X ₁₀ /Z _0.3 /D _0.5 -E _OP -D _0.5 three-stage bleaching sequence.

Table 2 Performance index of eucalyptus X ₁₀ /Z _0.3 /D _0.5 -E _OP -D _0.5 bleached pulp and control pulp

As shown in Table 2, after eucalyptus sulfate oxygen delignification, the pulp performance index after bleaching by X ₁₀ /Z _0.3 /D _0.5 -E _OP -D _0.5 is: brightness 87.5% ISO, tensile index 51.99N m/g, the burst index was 4.21 kPa·m ² ·g ^-1 , the folding endurance was 28 times, and the kappa value was 1.37. Compared with the oxygen delignified pulp of the control group, after bleaching with X ₁₀ /Z/D _0.5 -E _OP -D _0.5 , the pulp brightness increased by 42.30%, and the kappa value decreased by 76.47%. Compared with D _1.0 -Eo-D _0.5 -D _0.5 bleached pulp in the control group, when bleached to a similar brightness, the chlorine dioxide consumption in the bleaching procedure of X ₁₀ /Z _0.3 /D _0.5 -E _OP -D _0.5 was reduced by 50.0%. Tensile index, burst index and fold endurance were all improved to varying degrees.

Example 2:

Proceed as follows:

(1) ECF bleaching: X/Z/DE OP-D or X/D/X/Z/DE _OP -D or X/D/ The ZE _OP -D three-stage bleaching program bleaches.

First perform xylanase-assisted bleaching (X), the process conditions are: pulp concentration 12%, xylanase dosage 10U/g _pulp , pH=5, bleaching temperature 60°C, bleaching time 60min; Ozone bleaching (Z) needs to be washed directly, bleaching temperature is 60℃, pulp concentration is 12%, pH=2, bleaching time is 3min, ozone dosage is 0.3%, ethylene glycol dosage is 2%; after bleaching, the pulp does not need to be washed directly. Chlorine dioxide bleaching (D), the process conditions are: ClO ₂ dosage 1.0%, pulp concentration 12%, pH=2, bleaching temperature 60°C, bleaching time 30min; after bleaching, the pulp is washed and then subjected to E _OP section treatment. The conditions are: H ₂ O ₂ dosage 1%, pulp concentration 10%, pH=11, oxygen pressure 0.4Mpa, temperature 90°C, alkali treatment time 60min; after alkali treatment, the pulp is washed and then bleached with chlorine dioxide. Process conditions It is as follows: the amount of ClO ₂ is 0.5%, the pulp concentration is 10%, pH=3, the bleaching temperature is 60°C, the bleaching time is 30min, and the pulp is washed after the bleaching. In X/Z/D sequential bleaching, the replacement of Z and D positions does not affect the bleaching results.

(2) Papermaking: beat the above-mentioned bleached pulp to 35°SR, then carry out pulp fiber decompression in a fiber decompressor to make it evenly dispersed, and make a paper with a basis weight of 60g/m2 ^on a sheet former Page.

(3) The performance indexes of the obtained X/Z/DE _OP -D or X/D/ZE _OP -D bleached pulp are shown in Table 3 below. The control group is the pulp after oxygen delignification and the pulp after four stages of D-Eo-DD. The pulp obtained after bleaching sequence bleaching, Example 2 is the pulp obtained after bleaching by X ₁₀ /Z _0.3 /D _1.0 -E _OP -D _0.5 three-stage bleaching sequence.

Table 3 Performance index of eucalyptus X ₁₀ /Z _0.3 /D _1.0 -E _OP -D _0.5 bleached pulp and control pulp

As shown in Table 3, the pulp performance index after eucalyptus sulfate oxygen delignification was bleached by X ₁₀ /Z _0.3 /D _1.0 -E _OP -D _0.5 was: brightness 88.1% ISO, tensile index 47.58N ·m/g, the burst resistance index was 4.07kPa·m ² ·g ^-1 , the number of folding endurance was 23 times, and the kappa value was 1.20. Compared with the oxygen delignified pulp of the control group, after bleaching with X ₁₀ /Z _0.3 /D _1.0 -E _OP -D _0.5 , the pulp brightness increased by 43.11%, and the kappa number decreased by 77.23%. Compared with D _1.0 -Eo-D _0.5 -D _0.5 bleached pulp in the control group, when bleached to the same brightness, the chlorine dioxide consumption in the bleaching procedure of X ₁₀ /Z _0.3 /D _1.0 -E _OP -D _0.5 was reduced by 25.0%, and the anti- Tensile index, burst index and fold endurance were all improved to varying degrees.

Example 3:

Proceed as follows:

(1) ECF bleaching: X/Z/DE OP-D or X/D/X/Z/DE _OP -D or X/D/ The ZE _OP -D three-stage bleaching program bleaches.

First, perform xylanase-assisted bleaching (X), the process conditions are: pulp concentration 11%, xylanase dosage 10U/g _pulp , pH=8, bleaching temperature 70°C, bleaching time 60min; Ozone bleaching (Z) needs to be washed directly, bleaching temperature is 70°C, pulp concentration is 11%, pH=3, bleaching time is 4min, ozone dosage is 0.3%, ethylene glycol dosage is 2%; after bleaching, the pulp does not need to be washed directly. Chlorine dioxide bleaching (D), the process conditions are: ClO2 dosage _0.5 %, pulp concentration 11%, pH=3, bleaching temperature 70°C, bleaching time 30min; after bleaching, the pulp is washed and then subjected to E _OP section treatment. The conditions are: H ₂ O ₂ dosage 1%, pulp concentration 10%, pH=12, oxygen pressure 0.4Mpa, temperature 80°C, alkali treatment time 60min; after alkali treatment, the pulp is washed and then bleached with chlorine dioxide. Process conditions It is as follows: ClO ₂ dosage is 0.3%, pulp concentration is 10%, pH=3, bleaching temperature is 60°C, bleaching time is 30min, and the pulp is washed after bleaching. In X/Z/D sequential bleaching, the replacement of Z and D positions does not affect the bleaching results.

(2) Papermaking: beat the above-mentioned bleached pulp to 35°SR, then carry out pulp fiber decompression in a fiber decompressor to make it evenly dispersed, and make a paper with a basis weight of 60g/m2 ^on a sheet former Page.

(3) The performance indexes of the obtained X/Z/DE _OP -D or X/D/ZE _OP -D bleached pulp are shown in Table 4 below, and the control group is the pulp after oxygen delignification and the pulp after four stages of D-Eo-DD The pulp obtained after bleaching sequence, Example 3 is the pulp obtained after bleaching by X ₁₀ /Z _0.3 /D _0.5 -E _OP -D _0.3 three-stage bleaching sequence.

Table 4 Performance index of eucalyptus X ₁₀ /Z _0.3 /D _0.5 -E _OP -D _0.3 bleached pulp and control pulp

As shown in Table 4, after eucalyptus sulfate oxygen delignification, the pulp performance index after bleaching by X ₁₀ /Z _0.3 /D _0.5 -E _OP -D _0.3 is: brightness 87.3% ISO, tensile index 51.14N ·m/g, the burst index was 4.17kPa·m ² ·g ^-1 , the number of folding endurance was 30 times, and the kappa value was 1.24. Compared with the oxygen delignified pulp of the control group, after bleaching with X ₁₀ /Z _0.3 /D _0.5 -E _OP -D _0.3 , the pulp brightness increased by 41.49%, and the kappa number decreased by 76.47%. Compared with the bleached pulp of D _0.5 -Eo-D _0.5 -D _0.5 in the control group, when bleached to the same brightness, the chlorine dioxide consumption in the bleaching procedure of X ₁₀ /Z _0.3 /D _0.5 -E _OP -D _0.3 was reduced by 47.13%. Tensile index, burst index and fold endurance were all improved to varying degrees.

Example 4:

Proceed as follows:

(1) ECF bleaching: X/Z/DE OP-D or X/D/X/Z/DE _OP -D or X/D/ The ZE _OP -D three-stage bleaching program bleaches.

First, perform xylanase-assisted bleaching (X), the process conditions are: pulp concentration 13%, xylanase dosage 15U/g _pulp , pH=8, bleaching temperature 80°C, bleaching time 60min; Ozone bleaching (Z) needs to be washed directly, bleaching temperature is 80°C, pulp concentration is 13%, pH=3.5, bleaching time is 1min, ozone dosage is 0.3%, and ethylene glycol dosage is 2%; after bleaching, the pulp does not need to be washed directly. Chlorine dioxide bleaching (D), the process conditions are: ClO2 dosage _0.5 %, pulp concentration 13%, pH=3.5, bleaching temperature 80°C, bleaching time 30min; after bleaching, the pulp is washed and then subjected to E _OP section treatment. The conditions are: H ₂ O ₂ dosage 1%, pulp concentration 10%, pH=11, oxygen pressure 0.4Mpa, temperature 90°C, alkali treatment time 60min; after alkali treatment, the pulp is washed and then bleached with chlorine dioxide. Process conditions It is as follows: the amount of ClO ₂ is 0.3%, the pulp concentration is 10%, pH=3, the bleaching temperature is 70°C, the bleaching time is 30min, and the pulp is washed after the bleaching. In X/Z/D sequential bleaching, the replacement of Z and D positions does not affect the bleaching results.

(2) Papermaking: beat the above-mentioned bleached pulp to 35°SR, then carry out pulp fiber decompression in a fiber decompressor to make it evenly dispersed, and make a paper with a basis weight of 60g/m2 ^on a sheet former Page.

(3) The performance indexes of the obtained X/Z/DE _OP -D or X/D/ZE _OP -D bleached pulp are shown in Table 5 below. The control group is the pulp after oxygen delignification and the pulp after four stages of D-Eo-DD. The paper-based material obtained after bleaching sequence bleaching, Example 4 is the pulp obtained after bleaching by X ₁₅ /Z _0.3 /D _0.5 -E _OP -D _0.3 three-stage bleaching sequence.

Table 5 Performance index of eucalyptus X ₁₅ /Z _0.3 /D _0.5 -E _OP -D _0.3 bleached pulp and control pulp

As shown in Table 5, after eucalyptus sulfate oxygen delignification, the pulp performance index after bleaching by X ₁₅ /Z _0.3 /D _0.5 -E _OP -D _0.3 is: brightness 87.5% ISO, tensile index 51.99N ·m/g, the burst index was 4.21 kPa·m ² ·g ^-1 , the folding endurance was 31 times, and the kappa value was 1.27. Compared with the oxygen delignified pulp of the control group, after bleaching with X ₁₅ /Z _0.3 /D _0.5 -E _OP -D _0.3 , the pulp brightness increased by 41.82%, and the kappa number decreased by 75.90%. Compared with the bleached pulp of D _0.5 -Eo-D _0.5 -D _0.5 in the control group, when bleached to the same brightness, the amount of chlorine dioxide in the bleaching procedure of X ₁₅ /Z _0.3 /D _0.5 -E _OP -D _0.3 was reduced by 47.13%. Tensile index, burst index and fold endurance were all improved to varying degrees.

Example 5:

Proceed as follows:

(1) ECF bleaching: X/Z/DE OP-D or X/D/X/Z/DE _OP -D or X/D/ The ZE _OP -D three-stage bleaching program bleaches.

First, perform xylanase-assisted bleaching (X), and the process conditions are: pulp concentration 10%, xylanase dosage 10U/g _pulp , pH=9, bleaching temperature 60°C, bleaching time 60min; Ozone bleaching (Z) needs to be washed directly, bleaching temperature is 60°C, pulp concentration is 10%, pH=2, bleaching time is 3min, ozone dosage is 0.9%, and ethylene glycol dosage is 2%; after bleaching, the pulp does not need to be washed directly. Chlorine dioxide bleaching (D), the process conditions are: pulp concentration 10%, ClO2 dosage 0.3%, pH= ₂ , bleaching temperature 60°C, bleaching time 30min; after bleaching, the pulp is washed and then subjected to E _OP section treatment. The conditions are: H ₂ O ₂ dosage 1%, pulp concentration 10%, pH=11, oxygen pressure 0.4Mpa, temperature 85°C, alkali treatment time 60min; after alkali treatment, the pulp is washed and then bleached with chlorine dioxide. The process conditions It is: pulp concentration 10%, ClO ₂ dosage 0.2%, pH=2, bleaching temperature 60°C, bleaching time 30min, and washing the pulp after bleaching. In X/Z/D sequential bleaching, the replacement of Z and D positions does not affect the bleaching results.

(2) Papermaking: beat the above-mentioned bleached pulp to 35°SR, then carry out pulp fiber decompression in a fiber decompressor to make it evenly dispersed, and make a paper with a basis weight of 60g/m2 ^on a sheet former Page.

(3) The performance indexes of the obtained X/Z/DE _OP -D or X/D/ZE _OP -D bleached pulp are shown in Table 6 below. The control group is the pulp after oxygen delignification and the pulp after four stages of D-Eo-DD. The pulp obtained after bleaching sequence, Example 5 is the pulp obtained after bleaching by X ₁₀ /Z _0.3 /D _0.3 -E _OP -D _0.2 three-stage bleaching sequence.

Table 6 Performance index of eucalyptus X ₁₀ /Z _0.3 /D _0.3 -E _OP -D _0.2 bleached pulp and control pulp

As shown in Table 6, the pulp performance index after eucalyptus sulfate oxygen delignification was bleached by X ₁₀ /Z _0.3 /D _0.3 -E _OP -D _0.2 was: brightness 87.2% ISO, tensile index 53.31N m/g, the burst index was 4.32 kPa·m ² ·g ^-1 , the folding endurance was 33 times, and the kappa value was 1.31. Compared with the oxygen delignified pulp of the control group, after bleaching with X ₁₀ /Z _0.3 /D _0.3 -E _OP -D _0.2 , the pulp brightness increased by 41.33%, and the kappa number decreased by 75.14%. Compared with D _0.5 -Eo-D _0.5 -D _0.5 bleached pulp in the control group, when bleached to the same brightness, the amount of chlorine dioxide in the bleaching procedure of X ₁₀ /Z _0.3 /D _0.3 -E _OP -D _0.2 was reduced by 66.67%, and the anti- Tensile index, burst index and fold endurance were all improved to varying degrees.

Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will still Modifications may be made to the technical solutions described in the foregoing embodiments, or equivalent replacements may be made to some of them. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention. Although the specific embodiments of the present invention are described above, they do not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solutions of the present invention, those skilled in the art can make Various modifications or deformations made are still within the protection scope of the present invention.

Claims (10)

1. A kraft short-run ECF bleaching process comprising:

subjecting the oxygen delignified wood pulp to X/Z/D₁Or X/D₁the/Z order bleaches to produce half-bleaching paperPulping;

carrying out hydrogen peroxide and oxygen enhanced alkaline extraction treatment on the sequentially bleached pulp;

chlorine dioxide D is carried out on the pulp after the strengthening alkali extraction treatment₂Supplementary bleaching to obtain fully bleached pulp;

wherein, the X/Z/D₁Or X/D₁In the/Z sequential bleaching, X, Z, D₁No pulp wash was performed between bleaches.

2. The kraft short process ECF bleaching process of claim 1, wherein the greige stock is produced using a sulfate process.

3. The kraft short-run ECF bleaching process of claim 1, wherein the oxygen delignification is replaced with an enhanced oxygen delignification.

4. The kraft short-run ECF bleaching process of claim 1, wherein the xylanase-assisted bleaching X is carried out under process conditions of: the dosage of xylanase is 5-20U/g_{Pulp and its production process}The pulp concentration is 10-15%, the pH value is 5-9, the bleaching temperature is 50-80 ℃, and the bleaching time is 60-120 min.

5. The sulfate wood pulp short-procedure ECF bleaching process according to claim 1, wherein the ozone bleaching Z is performed under the conditions of a bleaching temperature of 50-80 ℃, a pulp concentration of 10-15%, a pH of 2-4, a bleaching time of 0.5-5 min, an ethylene glycol amount of 1-3% and an ozone amount of 0.2-1.5%.

6. The kraft short-run ECF bleaching process of claim 1, wherein chlorine dioxide bleaching D₁The process conditions are as follows: ClO₂The dosage is 0.2-1.0%, the pulp concentration is 10-15%, the pH value is 2-4, the bleaching temperature is 50-80 ℃, and the bleaching time is 30-180 min.

7. The kraft short-run ECF bleaching process of claim 1, whereinIn the above, X/Z/D₁Or X/D₁Segment Z and E_OPSegment and D₂Pulp washing is performed between the stages.

8. The kraft short-run ECF bleaching process of claim 1, wherein E is_OPThe process conditions of the section treatment are as follows: h₂O₂1-3% of dosage, 10-15% of pulp concentration, 11-12% of pH, 0.4Mpa of oxygen pressure, 80-90 ℃ of temperature and 30-60min of alkali treatment time;

or, D₂The section bleaching process conditions are as follows: ClO₂The dosage is 0.5-1.0%, the pulp concentration is 10-15%, the pH value is 2-4, the bleaching temperature is 50-80 ℃, and the bleaching time is 30-180 min.

9. A fully bleached pulp produced by the process of any one of claims 1 to 8.

10. Use of the fully bleached pulp of claim 9 in the production of paper and paperboard.