JP2022549123A - Short-Procedure ECF Bleaching Process X/DZP (X/ZDP) for Kraft Wood Pulp - Google Patents

Abstract

A short-procedure ECF bleaching process X/DZP (or X/ZDP) for kraft wood pulp is provided. The present invention belongs to the technical field of pulping and papermaking and relates to a short procedure ECF bleaching process X/DZP (or X/ZDP) for kraft wood pulp, which after oxygen delignification A sequential bleaching (X/D) step (1) in which the kraft wood pulp is subjected to X/D sequential bleaching without washing between X and D, and ozone is applied to the pulp after X/D sequential bleaching. Ozone bleaching (Z) step (2) to perform bleaching and finally hydrogen peroxide bleaching to the pulp after ozone bleaching to obtain a fully bleached pulp (88% ISO) hydrogen peroxide bleaching ( P) Step (3) and the D and Z positions in the above bleaching procedure can be interchanged, changing the process from X/DZP to X/ZDP results in the final bleaching and step (4), which does not affect the result. The X/DZP (or X/ZDP) bleaching procedure is reduced from 4 bleaching stages to 3 bleaching stages compared to the conventional D-Eo-DD bleaching procedure, Ozone and hydrogen peroxide green bleaches are used and there is only one chlorine dioxide bleaching stage. Therefore, the bleaching method provided by the present invention significantly reduces the consumption of bleaching water and the toxicity of wastewater, and with the same brightness of the final pulp, reduces the consumption of chlorine dioxide by more than 50%, and reduces the consumption of water by more than 50%. reduce the volume by more than 20%.

Description

Cross-reference to related applications

The present application was filed with the Chinese Patent Office on August 7, 2020, application number 202010789553.5, titled "Short Procedure ECF Bleaching Process for Kraft Wood Pulp X/DZP (X/Z- D-P)”, the entire content of which is incorporated into this application by reference.

The present invention relates to the technical field of pulping and papermaking, in particular to the short-procedure ECF bleaching process X/DZP (or X/ZDP) for kraft wood pulp.

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

The pulping and paper industry is one of the basic raw material industries of the national economy and has always occupied an important position in the world's industrial manufacturing industry. The level of paper and paperboard production and consumption has become an important indicator of a country's economic development and social progress. In China, raw materials for pulping and papermaking are mainly divided into three categories: wood pulp, non-wood pulp and waste paper pulp. The wood pulps used in the pulping and paper industry are mainly hardwoods such as early poplar and early eucalyptus, which are characterized by rapid growth, strong adaptability, loose material, good chemical absorption, high cellulose and hemicellulose content. It has characteristics such as quantity. They can be used in the production of pulp types such as chemical pulp, semi-chemical pulp, mechanical pulp and the like.

At present, China has become the world's leading country in the production and consumption of paper products, but the resource, energy and environmental constraints facing the paper industry are becoming more and more prominent. Recycling, low carbon and green economy have become new development themes. Improvement of the pulping process, control of production costs, improvement of paper quality, reduction of pollution load in the production process, etc. are problems that must be solved urgently, and have become research hotspots for scientists and engineers. there is Chlorine-free bleaching, fully chlorine-free bleaching, and biological bleaching technologies are alternatives to traditional bleaching technologies for the production of high strength, high brightness pulp to meet the requirements of energy saving, emission reduction, green and low carbon development models. Bleach technology.

However, existing ECF bleaching processes suffer from problems such as high water consumption for bleaching and toxic chlorides in the wastewater, and there is also a need to improve bleaching efficiency.

To overcome the above problems, the present invention provides a short-procedure ECF bleaching process X/DZP (or X/ZDP) for kraft wood pulp. To effectively improve the brightness of pulp on the premise of ensuring the physical strength of paper made of bleached kraft pulp.

The present invention is realized by the following technical solutions. All pulp densities referred to below are in weight percent unless otherwise specified. All reagent and drug dosages involved are based on absolute dry pulp, unless otherwise specified.

To achieve the above technical objectives, the present invention adopts the following technical solutions.

A first aspect of the present invention is X/DZP or X/ZDP bleaching the pulp after oxygen delignification treatment,
wherein during the X/DZP bleaching process no pulp washing is performed between the X bleaching stage and the D bleaching stage;
Short-procedure ECF bleaching method X/DZP (or X/Z- DP).

Compared to conventional D-Eo-D-D bleaching procedures, the X/DZP (or X/ZDP) bleaching procedure of the present invention reduces from four bleaching stages to three bleaching stages. It is reduced, uses ozone and hydrogen peroxide green bleaches, and has only one chlorine dioxide bleaching stage. Therefore, the bleaching water consumption and wastewater toxicity of the bleaching process provided by the present invention are greatly reduced. Chlorine dioxide consumption is reduced by more than 50% and water consumption is reduced by more than 20% for the same final brightness compared to conventional D-Eo-D-D bleaching procedures.

A second aspect of the invention provides a paper base material prepared by the bleaching method described above.

The pulp prepared according to the present invention has excellent brightness and strength performance, effectively improving the brightness of pulp on the premise of ensuring the physical strength of paper made of kraft bleached pulp. In the present invention, said brightness and strength performance refer to the brightness and strength performance of paper prepared from the pulp.

A third aspect of the invention provides the application of the above paper-based material in the manufacture of paper products.

The pulp prepared in this application has excellent brightness and strength performance, so the consumption of bleaching water and toxicity of wastewater are greatly reduced, and it is expected to be widely used in the production of paper products. be.

Beneficial effects of the present invention are as follows.
(1) Compared to the conventional DEODD bleaching procedure, the X/DZP (or X/ZDP) bleaching procedure of the present invention reduces from four bleaching stages to three It is reduced to bleaching stages, uses ozone and hydrogen peroxide green bleaches, and has only one chlorine dioxide bleaching stage. Therefore, the bleaching method of the present invention greatly reduces the consumption of bleaching water and toxicity of wastewater, and with the same final brightness, the consumption of chlorine dioxide is reduced by more than 50%, and the consumption of water is More than 20% reduction.
(2) The pulp prepared according to the present invention has excellent brightness and strength performance, and effectively improves the brightness of the pulp on the premise of ensuring the physical strength of paper made of kraft bleached pulp. do.
(3) The method of the present invention is simple, low cost, highly practical, and easy to spread.

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

Note that the terminology used herein is for the purpose of describing the mode of practice only and is not intended to be limiting of example embodiments in accordance with the invention. As used herein, the singular forms are also intended to include the plural forms unless the context clearly dictates otherwise. It is further understood that when the terms "contain" and/or "comprise" are used herein, they indicate that there are features, steps, operations, devices, components, and/or combinations thereof. want to be

In the present invention, in X/DZP (or X/ZDP), D stands for chlorine dioxide bleaching, Z for ozone bleaching, X for xylanase bleaching, and P for hydrogen peroxide bleaching.

A short-procedure ECF bleaching process X/DZP (or X/ZDP) for kraft wood pulp, the steps of which are as follows:
(1) Preparation of pulp: Wood chips are steamed and boiled by Kraft method, then washed and sieved to obtain unbleached pulp, then oxygen delignification is performed on the unbleached pulp to obtain pulp. obtain.
(2) ECF Bleaching: The bleaching procedure for the above pulp is the X/DZP bleaching process. Among them, X/D bleaching sequentially, no pulp washing between X and D bleaching, pulp washing between X/D stage, Z stage and P stage; Z can be transposed, i.e. change the process from X/DZP to X/ZDP, where X/Z is sequential bleaching, pulp No washing is done and the exchange of D and Z does not affect the final bleaching result.

Our studies show that our bleaching process has superior strength performance indicators to conventional XZDP or XDZP bleached pulps because there is no intermediate wash. was found.

In order to obtain the best bleaching effect, the present invention optimizes the bleaching process conditions. In some examples, the bleaching process conditions are as follows. X/D bleaching stage: xylanase usage in X is 5-20 U/g pulp, pulp consistency is 10-15%, pH value is 5-9, bleaching temperature is 50-80°C, bleaching time is 60-120 minutes. and the amount of _ClO2 used in D is 0.5-1.0%, the pulp consistency is 10-15%, the pH value is 2-4, the bleaching temperature is 50-80°C, and the bleaching time is 30-180 minutes. is. Z bleaching stage: pulp consistency is 10-15%, pH value is 2-4, bleaching temperature is 50-80°C, bleaching time is 0.5-5 minutes, amount of ethylene glycol is 1-3%, ozone is The amount used is 0.2-1.5%. P bleaching stage: H ₂ O ₂ usage is 1-3%, pulp consistency is 10-15%, pH value is 11-12, temperature is 80-90° C., bleaching time is 90-120 minutes. By using the above process conditions, the brightness of the pulp can be effectively improved on the premise of ensuring the physical strength of the bleached kraft pulp to paper.

Furthermore, the specific method of said X is as follows. Adjust the pulp consistency to 10-15%, adjust the pH value to 5-9, keep the pulp temperature at 50-80 ℃, add xylanase 5-20 U/g pulp, hold for 60-120 minutes, and add xylanase is used to degrade the xylan deposited on the surface of the pulp fibers and the lignin-carbohydrate complex structures in the pulp. After X, proceeding directly to Z or D without washing is beneficial for bleach penetration and lignin elution, improves bleach efficiency, and improves pulp bleaching effectiveness.

In order to reduce chlorine dioxide usage and reduce bleaching costs, the present invention limits the process conditions for D. In some embodiments, specific methods of D are as follows. The pH value is adjusted to 2.0-4.0, the pulp consistency is maintained at 10-15%, the temperature is 50-80° C., D is performed, and the amount of ClO ₂ is 0.5-1. 0%, bleaching time is 30-180 minutes, allowing more chlorine dioxide to participate in the bleaching process, saving chlorine dioxide usage.

The present invention studies the effect of ozone usage on kraft wood pulp brightness, hardness, and viscosity. Thus, in some embodiments, specific methods for said Z are as follows. Adjust the pH value to 2.0-4.0, keep the pulp density at 10-15%, add 1-3% ethylene glycol, bleaching temperature is 50-80 ℃, mix evenly, Z is carried out, and the amount of ozone used is 0.3 to 1.5%, and the bleaching time is 0.5 to 5 minutes to obtain pulp with high strength and high brightness.

Studies have shown that pH value, temperature, concentration, and time have a greater impact on the P effect. Therefore, in some embodiments, specific methods for said P are as follows. Washing the pulp after Z or D, adjusting the pH value to 11-12, adding 1-3% hydrogen peroxide under the conditions of pulp consistency of 10-15%, temperature of 80-90 ℃, The bleaching time is 90-120 minutes, which can better improve the brightness of pulp, reduce production costs and improve economic benefits.

In the present invention, X is performed on the pulp, then D is performed, then Z is performed on the pulp obtained from D, and P is performed on the pulp obtained from Z, or Do X, then Z, then D for the pulp obtained from Z, and P for the pulp obtained from D.

In addition, the pulp after the above bleaching treatment is used to skim the paper.

Another embodiment of the present disclosure provides a paper base material prepared from bleached pulp obtained by the bleaching method described above. The bleached pulp paper base material not only has better physical strength performance, but also has higher brightness.

The invention also provides the application of the above paper-based material in the manufacture of paper products.

The present invention will now be described in more detail with reference to specific examples. It should be noted that the above specific examples are illustrative rather than limiting of the present invention.

Brightness measurement: The pulp is degraded in a fiber decomposer, then papered with an Austrian Kaiser handsheet, and then measured with a YQ-Z-48B brightness meter.
Folding endurance: Measured by MIT folding endurance tester made in China.
Specific Bursting Strength: Measured on a Bursting Tester from the Swedish company L&W.
Specific Tensile Strength: Measured by XLWA(B) intelligent electronic tensile tester made in China.
All remaining experimental methods not described in detail are conventional test methods in the field.

The present invention uses xylanase bleaching, a combination of chlorine dioxide with ozone and hydrogen peroxide to perform a bleaching treatment of the X/DZP (or X/ZDP) bleaching procedure on pulp. to obtain pulp with higher brightness and strength. Specifically, it is as follows.

Comparative Example 1:
The steps are as follows.
(1) Eucalyptus steaming conditions are as follows. The amount of alkali used is 21%, the liquid ratio is 1:5, the degree of vulcanization is 25%, the cooking temperature is 170°C, with small exhaust at 105°C, the heating time is 100 minutes, and the temperature holding time is 90 minutes. After steaming, washing and screening were performed to obtain unbleached kraft pulp.
(2) Conditions for oxygen delignification are as follows. Adjust the concentration of unbleached kraft pulp to 10%, the amount of NaOH used to ₃ %, the amount of MgSO4 used to 0.6%, the oxygen pressure to 0.6 Mpa, the temperature to 100 ° C, and the temperature holding time to 60 minutes. and then washed to obtain oxygen delignified pulp.
(3) ECF bleaching: A four-step bleaching procedure D-Eo-DD was performed on the oxygen delignified pulp. The process conditions for the D bleach stage are as follows. The pulp consistency was 10%, the total amount of ClO ₂ used in the three stages was 1.5-2.0%, the pH value was 2.0, the bleaching temperature was 60°C, and the bleaching time was 30-60 minutes. After washing the slurry, the E 2 _O bleach stage treatment is carried out, the process conditions are as follows. The pulp concentration was 10-15%, the pH value was 11-12, the oxygen pressure was 0.4 Mpa, the temperature was 80-90° C., and the alkaline treatment time was 30-60 minutes. After bleaching was finished, the pulp was washed.
(4) Peeled paper: Eucalyptus Kraft steamed unbleached pulp, oxygen delignified pulp, D-EoDD bleached pulp were each beaten to 35° SR, and then each pulp fiber was was decomposed and uniformly dispersed, and paper with a basis weight of 60 g/m ² was made with a handcombine.
(5) Table 1 shows the performance index of the unbleached pulp, oxygen delignified pulp, and D-Eo-DD bleached pulp after eucalyptus craft steaming.

Example 1:
The steps are as follows.
(1) ECF bleaching: X/DZP three bleaching stage bleaching procedure for eucalyptus kraft pulp after undergoing oxygen delignification (same preparation method as step 1), 2) of comparative example) was bleached. The X/D stage bleaching was performed first, the process conditions for X being as follows. The pulp consistency is 10%, the amount of xylanase used is 15 U/g pulp, the pH value is 5, the bleaching temperature is 60° C., and the bleaching time is 60 minutes. The pulp was not washed and was subjected to D and the process conditions were as follows. Pulp consistency is 10%, _ClO2 usage is 0.3%, pH value is 2.0, bleaching temperature is 60°C, bleaching time is 30 minutes. After cleaning, a Z-stage is performed and the process conditions are as follows. The pulp consistency is 10%, the pH value is 2, the bleaching temperature is 60° C., the bleaching time is 2 minutes, the amount of ozone used is 0.3%, and the amount of ethylene glycol is 2%. After washing the pulp, the P-stage is performed and the process conditions are as follows. The H ₂ O ₂ usage was 3%, the pulp consistency was 10%, the pH value was 11.0, the temperature was 85°C, the bleaching time was 120 minutes, and the pulp was washed after bleaching was finished.
Alternatively, bleaching was performed by swapping the D and Z positions without changing the bleaching parameters.
(2) Paper was made: After beating the above bleached pulp to 35° SR, the pulp fibers were decomposed and uniformly dispersed with a fiber disintegrator, and then paper with a basis weight of 60 g / m ² was made with a hand paper machine. I was hungry.
(3) As shown in Table 2 for the performance index of the obtained X/DZP (or X/ZDP) bleached pulp, the control group was oxygen delignified pulp and D-Eo-D -D is a bleached pulp that has undergone a 4-stage bleaching procedure, and Example 1 is a bleached pulp that has undergone a 3-stage bleaching procedure, where the oxygen delignified pulp is X ₁₅ /D _0.3 -ZP ₃ . .

Results: After detection, the eucalyptus kraft pulp after oxygen delignification was bleached with _X15 / _{D0.3 -} ZP3. It has a tensile strength of 45.19 N·m/g, a specific burst strength of 3.59 kPa·m ² ·g ⁻¹ , a folding endurance of 23 times, and a kappa value of 0.95. The brightness of the pulp increased by 44.08% and the kappa value decreased by 82.16% after X ₁₅ /D _0.3 -ZP ₃ bleaching compared with the oxygen delignified pulp of the control group. Bleaching to a similar brightness compared to the D _0.5 -Eo-D _0.5 -D _0.5 bleached pulp of the control group showed that the dioxide of the X ₁₅ /D _0.3 -ZP ₃ bleaching process Chlorine usage was reduced by 85.0% with no apparent change in strength performance index.

Example 2:
The steps are as follows.
(1) ECF bleaching: X/DZP three bleaching stage bleaching procedure for eucalyptus kraft pulp after undergoing oxygen delignification (same preparation method as step 1), 2) of comparative example) was bleached. The X/D stage bleaching was performed first, the process conditions for X being as follows. The pulp consistency is 12%, the amount of xylanase used is 15 U/g pulp, the pH value is 6, the bleaching temperature is 60°C, and the bleaching time is 60 minutes. The pulp is not washed and then D, the process conditions are as follows. Pulp consistency is 12%, _ClO2 usage is 0.5%, pH value is 2.0, bleaching temperature is 60°C, bleaching time is 30 minutes. After washing the pulp, the Z-stage is performed and the process conditions are as follows. The pulp consistency is 12%, the pH value is 2, the bleaching temperature is 60°C, the bleaching time is 30 minutes, the amount of ozone used is 0.9%, and the amount of ethylene glycol is 2%. After washing the pulp, the P-stage is performed and the process conditions are as follows. The H ₂ O ₂ usage was 1.5%, the pulp consistency was 10%, the pH value was 11.0, the temperature was 90° C., the bleaching time was 120 minutes, and after the bleaching was finished, the pulp was washed.
Alternatively, bleaching was performed by swapping the D and Z positions without changing the bleaching parameters.
(2) Paper was made: After beating the above bleached pulp to 35° SR, the pulp fibers were decomposed and uniformly dispersed with a fiber disintegrator, and then paper with a basis weight of 60 g / m ² was made with a hand paper machine. I was hungry.
(3) As shown in Table 3 for the performance index of the obtained X/DZP (or X/ZDP) bleached pulp, the control group was the pulp after oxygen delignification and D-Eo - DD, and Example 2 is a pulp after oxygen delignification subjected to a three-stage bleaching procedure of X ₁₅ /D _0.5 -ZP _1.5 . It was a hard pulp.

Results: after detection, eucalyptus kraft pulp after oxygen delignification X ₁₅ /D _0.5 -ZP _1.5 performance index of bleached pulp is 87.8% ISO brightness, specific tensile It has a strength of 51.66 N·m/g, a specific burst strength of 3.908 kPa·m ² ·g ⁻¹ , a folding endurance of 25 times, and a kappa value of 1.23. After X ₁₅ /D _0.5 -ZP _1.5 bleaching, the brightness of the pulp increased by 42.30% and the kappa value decreased by 76.67% compared with the oxygen delignified pulp of the control group. . Bleached to similar brightness compared to the D _0.5 -Eo-D _0.5 -D _0.5 bleached pulp of the control group, the X ₁₅ /D _0.5 -ZP _1.5 bleaching process chlorine dioxide usage was reduced by 75.0%, with some improvement in strength performance index.

Example 3:
The steps are as follows.
(1) ECF bleaching: For eucalyptus kraft pulp after undergoing oxygen delignification (same preparation method as in steps 1), 2) of the comparative example), a three bleaching stage procedure of X/DZP bleached. The X/D stage bleaching was performed first, the process conditions for X being as follows. The pulp consistency is 15%, the amount of xylanase used is 10 U/g pulp, the pH value is 7, the bleaching temperature is 70° C., and the bleaching time is 60 minutes. The pulp was not washed and was subjected to D and the process conditions were as follows. Pulp consistency is 15%, _ClO2 usage is 0.5%, pH value is 2.0, bleaching temperature is 70°C, bleaching time is 30 minutes. After washing the pulp, the Z-stage is performed and the process conditions are as follows. The pulp consistency is 15%, the pH value is 2, the bleaching temperature is 70° C., the bleaching time is 5 minutes, the amount of ozone used is 0.9%, and the amount of ethylene glycol is 2%. After washing the pulp, the P-stage is performed and the process conditions are as follows. The H ₂ O ₂ usage was 2%, the pulp consistency was 10%, the pH value was 11.0, the temperature was 85°C, the bleaching time was 120 minutes, and the pulp was washed after bleaching was finished.
Alternatively, bleaching was performed by swapping the D and Z positions without changing the bleaching parameters.
(2) Paper was made: After beating the above bleached pulp to 35° SR, the pulp fibers were decomposed and uniformly dispersed with a fiber disintegrator, and then paper with a basis weight of 60 g / m ² was made with a hand paper machine. I was hungry.
(3) As shown in Table 4, the performance index of the obtained X/DZP (or X/ZDP) bleached pulp, the control group was the pulp after oxygen delignification and D-Eo - DD, and Example 3 is a pulp after oxygen delignification subjected to a three-stage bleaching procedure of X ₁₀ /D _0.5 -ZP ₂ . Met.

Results: after detection, eucalyptus kraft pulp after oxygen delignification performed X ₁₀ /D _0.5 -ZP ₂ bleached pulp performance index of whiteness 88.4% ISO, specific tensile strength 46.76 N·m/g, specific burst strength of 3.607 kPa·m ² ·g ⁻¹ , folding endurance of 24 times, and kappa value of 1.04. The brightness of the pulp increased by 43.27% and the kappa value decreased by 80.26% after X ₁₀ /D _0.5 -ZP ₂ bleaching compared with the oxygen delignified pulp of the control group. Bleaching to a similar brightness compared to the D _1.0 -Eo-D _0.5 -D _0.5 bleached pulp of the control group showed that the dioxide of the X ₁₀ /D _0.5 -ZP ₂ bleaching process Chlorine usage was reduced by 75.0% with some improvement in strength performance index.

Example 4:
The steps are as follows.
(1) ECF bleaching: For eucalyptus kraft pulp after oxygen delignification (same preparation method as in steps 1), 2) of the comparative example), a three-step bleaching procedure of X/DZP was applied. gone. The X/D stage bleaching was performed first, the process conditions for X being as follows. The pulp consistency is 10%, the amount of xylanase used is 10 U/g, the pH value is 9, the bleaching temperature is 70° C., and the bleaching time is 90 minutes. The pulp was not washed and was subjected to D and the process conditions were as follows. Pulp consistency is 10%, _ClO2 usage is 0.5%, pH value is 4.0, bleaching temperature is 70°C, bleaching time is 30 minutes. After washing the pulp, the Z-stage is performed and the process conditions are as follows. The pulp consistency is 10%, the pH value is 3, the bleaching temperature is 70° C., the bleaching time is 4 minutes, the amount of ozone used is 0.9%, and the amount of ethylene glycol is 2%. After washing the pulp, the P-stage is performed and the process conditions are as follows. The H ₂ O ₂ usage was 3%, the pulp consistency was 10%, the pH value was 11.0, the temperature was 85°C, the bleaching time was 120 minutes, and the pulp was washed after bleaching was finished. Alternatively, bleaching was performed by swapping the D and Z positions without changing the bleaching parameters.
(2) Paper was made: After beating the above bleached pulp to 35° SR, the pulp fibers were decomposed and uniformly dispersed with a fiber disintegrator, and then paper with a basis weight of 60 g / m ² was made with a hand paper machine. I was hungry.
(3) As shown in Table 5 for the performance index of the obtained X/DZP (or X/ZDP) bleached pulp, the control group was the pulp after oxygen delignification and D-Eo Example 4 is a pulp after oxygen delignification subjected to a three-stage bleaching procedure of X ₁₀ /D _0.5 -ZP ₃ . there were.

Results: after detection, the eucalyptus kraft pulp after oxygen delignification was bleached with X ₁₀ /D _0.5 -ZP ₃ , the pulp performance indicators were whiteness 88.6% ISO, specific tensile strength It has a thickness of 44.48 N·m/g, a specific burst strength of 3.21 kPa·m ² ·g ⁻¹ , a folding endurance of 24 times, and a kappa value of 1.01. After X ₁₀ /D _0.5 -ZP ₃ bleaching, the brightness of the pulp increased by 43.60% and the kappa value decreased by 80.83%, compared with the oxygen delignified pulp of the control group. Compared with the D _0.5 -Eo-D _0.5 -D _0.5 bleached pulp in the control group, after X ₁₀ /D _0.5 -ZP ₃ bleaching, the brightness of the pulp is 1.4 degrees Chlorine dioxide usage decreased by 66.67% and the strength performance index decreased slightly. Compared to D _0.5 -Eo-D _0.5 -D _0.5 bleached pulp in the control group, bleaching to similar brightness shows that the X ₁₀ /D _0.5 -ZP ₃ bleaching process Chlorine usage was reduced by 75.0% with no appreciable change in strength performance index.

Example 5:
The steps are as follows.
(1) ECF bleaching: For eucalyptus kraft pulp after oxygen delignification (same preparation method as in steps 1), 2) of the comparative example), a three bleaching stage bleaching procedure of X/DZP was applied. gone. The X/D stage bleaching was performed first, the process conditions for X being as follows. The pulp consistency is 15%, the amount of xylanase used is 10 U/g pulp, the pH value is 8, the bleaching temperature is 80° C., and the bleaching time is 60 minutes. The pulp was not washed and was subjected to D and the process conditions were as follows. Pulp consistency is 15%, _ClO2 usage is 0.7%, pH value is 3.5, bleaching temperature is 80°C, bleaching time is 30 minutes. After washing the pulp, the Z-stage is performed and the process conditions are as follows. The pulp consistency is 15%, the pH value is 3.5, the bleaching temperature is 80°C, the bleaching time is 5 minutes, the amount of ozone used is 0.9%, and the amount of ethylene glycol is 2%. After washing the pulp, the P-stage is performed and the process conditions are as follows. The H ₂ O ₂ usage was 3%, the pulp consistency was 10%, the pH value was 11.0, the temperature was 85°C, the bleaching time was 120 minutes, and the pulp was washed after bleaching was finished. Alternatively, bleaching was performed by swapping the D and Z positions without changing the bleaching parameters.
(2) Paper was made: After beating the above bleached pulp to 35° SR, the pulp fibers were decomposed and uniformly dispersed with a fiber disintegrator, and then paper with a basis weight of 60 g / m ² was made with a hand paper machine. I was hungry.
(3) As shown in Table 6, the performance index of the obtained X/DZP (or X/ZDP) bleached pulp, the control group was the pulp after oxygen delignification and D-Eo -DD, and Example 5 is obtained by bleaching the pulp after oxygen delignification with a three-stage bleaching procedure of X ₁₀ /D _0.7 -ZP ₃ . It was a pulp.

Results: After detection, the pulp performance index after bleaching the eucalyptus kraft pulp after oxygen delignification with X/DZP was 89.0% ISO for brightness and 44.21 N for specific tensile strength. m/g, specific burst strength of 3.12 kPa·m ² ·g ⁻¹ , folding endurance of 24 times, and kappa value of 1.12. The brightness of the pulp increased by 44.25% and the kappa value decreased by 77.42% after X ₁₀ /D _0.7 -ZP ₃ bleaching compared with the oxygen delignified pulp of the control group. After X ₁₀ /D _0.7 -ZP ₃ bleaching, compared with D _0.5 -Eo-D _0.5 -D _0.5 bleached pulp in the control group, the brightness of the pulp is 1.8 degrees , resulting in a 53.3% reduction in chlorine dioxide usage and a slight decrease in strength performance index. Compared to the D _0.5 -Eo-D _0.5 -D _0.5 bleached pulp of the control group, when bleached to similar brightness, the X ₁₀ /D _0.7 -ZP ₃ bleaching process chlorine dioxide usage decreased by 65.0% and the strength performance index decreased slightly.

Example 6:
The steps are as follows.
(1) ECF bleaching: X/DZP three-step bleaching procedure for eucalyptus kraft pulp after undergoing oxygen delignification (same preparation method as in steps 1), 2) of the comparative example) was bleached. The X/D stage bleaching was performed first, the process conditions for X being as follows. The pulp consistency is 12%, the amount of xylanase used is 10 U/g pulp, the pH value is 5, the bleaching temperature is 75°C, and the bleaching time is 60 minutes. The pulp was not washed and was subjected to D and the process conditions were as follows. Pulp consistency is 13%, _ClO2 usage is 1.0%, pH value is 2.5, bleaching temperature is 75°C, bleaching time is 30 minutes. After washing the pulp, the Z-stage is performed and the process conditions are as follows. The pulp consistency is 13%, the pH value is 2.5, the bleaching temperature is 75°C, the bleaching time is 3 minutes, the amount of ozone used is 0.9%, and the amount of ethylene glycol is 2%. After washing the pulp, the P-stage is performed and the process conditions are as follows. The H ₂ O ₂ usage was 3%, the pulp consistency was 15%, the pH value was 11.0, the temperature was 85° C., the bleaching time was 120 minutes, and the pulp was washed after bleaching was finished.
(2) Paper was made: After beating the above bleached pulp to 35° SR, the pulp fibers were decomposed and uniformly dispersed with a fiber disintegrator, and then paper with a basis weight of 60 g / m ² was made with a hand paper machine. I was hungry.
(3) The performance index of the obtained X/DZP (or X/ZDP) bleached pulp is shown in Table 7. The control group was the pulp after oxygen delignification and D-Eo - DD, and Example 6 is the pulp after oxygen delignification was bleached with a three-stage bleaching procedure of X ₁₀ /D _1.0 -ZP ₃ . It was the pulp obtained.

Results: After bleaching the eucalyptus kraft pulp after oxygen delignification after detection with X ₁₀ /D _1.0 -ZP ₃ , the pulp performance index is 89.8% ISO brightness and 0 Kappa value. .94. After X ₁₀ /D _1.0 -ZP ₃ bleaching, the brightness of the pulp increased by 45.54% and the kappa value decreased by 72.90% compared to the oxygen delignified pulp of the control group. Compared with the D _1.0 -Eo-D _0.5 -D _0.5 bleached pulp in the control group, after X ₁₀ /D _1.0 -ZP ₃ bleaching, the brightness of the pulp is 1.4 degrees Chlorine dioxide usage was reduced by 50.0% and the strength performance index was reduced to some extent.

Finally, it should be noted that the above descriptions are only preferred embodiments of the invention and are not intended to limit the invention. Although the present invention has been described in detail with reference to the preceding embodiments, for those skilled in the art, they can still modify the technical solutions described in the preceding embodiments, or Some can be replaced equally. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall all fall within the protection scope of the present invention. Although the above describes the modes for implementing the invention of the present invention, it is not intended to limit the scope of protection of the present invention, but those skilled in the art can make creative work based on the technical solutions of the present invention. It should be understood that various modifications or variations that can be made by persons skilled in the art without any modifications still fall within the protection scope of the present invention.

Claims (10)

A short-procedure ECF bleaching process X/DZP or X/ZDP for kraft wood pulp, wherein the pulp after oxygen delignification is treated with X/DZP or X/Z- DP bleaching,
wherein during the X/DZP bleaching process no pulp washing is performed between the X bleaching stage and the D bleaching stage;
A bleaching process characterized in that during the X/ZDP bleaching process no pulp washing is performed between the X bleaching stage and the Z bleaching stage. X is characterized in that the amount of xylanase used is 5-20 U/g pulp, the pulp concentration is 10-15%, the pH value is 5-9, the bleaching temperature is 50-80°C, and the bleaching time is 60-120 minutes. The bleaching method according to claim 1, wherein In D, the amount of ClO ₂ used is 0.5-1.0%, the pulp consistency is 10-15%, the pH value is 2-4, the bleaching temperature is 50-80°C, and the bleaching time is 30-180 minutes. The bleaching method according to claim 1, characterized by: In Z, the pulp concentration is 10-15%, the pH value is 2-4, the bleaching temperature is 50-80°C, the bleaching time is 0.5-5 minutes, the amount of ethylene glycol used is 1-3%, and the amount of ozone used is The bleaching method according to claim 1, characterized in that it is 0.2-1.5%. In P, the amount of H ₂ O ₂ used is 1-3%, the pulp consistency is 10-15%, the pH value is 11-12, the temperature is 80-90°C, and the bleaching time is 90-120 minutes. The bleaching method according to claim 1, wherein Before ECF bleaching, the wood chips are steamed and boiled by the Kraft method, followed by washing and screening to obtain unbleached pulp, and then oxygen delignification of the unbleached pulp to obtain pulp. The bleaching method according to claim 1, characterized by: 2. Bleaching process according to claim 1, characterized in that during the X/DZP bleaching process, pulp washing is carried out between the X/D, Z and P stages. 2. The bleaching method of claim 1, wherein said oxygen delignification treatment is an enhanced oxygen delignification treatment. A paper base material prepared by the bleaching process according to any one of claims 1-8. Application of the paper base material according to claim 9 in the manufacture of paper products.