Colored household paper decoloring method and paper pulp

Abstract

The invention provides a decolorizing method for colored paper for daily use. The decolorizing method comprises the following steps: providing the colored paper for daily use; the method comprises the following steps: performing pulping treatment on colored household paper under the conditions that the pulping concentration is 4-6%, the addition amount of hydrogen peroxide is 0.5-2% and the pH value is 9.5-11 to obtain pre-bleached pulp; under the conditions that the reaction concentration is 10%-13% and the reaction temperature is 90-105 DEG C, oxygen is introduced into the pre-bleached pulp for decoloration, the reaction time is 30-60 min, and primarily-bleached pulp is obtained; and carrying out chlorine dioxide bleaching decoloration on the primarily bleached pulp under the conditions that the reaction concentration is 10-13%, the reaction temperature is 50-70 DEG C and the pH value is 2-3 to obtain the decolorized paper pulp. According to the decolorizing method for the colored household paper, on the basis of original pulping and papermaking process configuration, decolorizing treatment of the colored waste paper can be achieved without adding additional processes and equipment, then effective utilization of the waste paper of the colored household paper is achieved, and the production cost is reduced. The invention further provides the paper pulp prepared by adopting the decolorizing method for the colored household paper. The paper pulp can be directly used for papermaking of the household paper.

Description

Technical Field

[0001] This application relates to the field of household paper technology, specifically to a method for decolorizing colored household paper and the pulp. Background Technology

[0002] In recent years, as an indispensable daily consumer product in people's lives and work, the styles of household paper have emerged in an endless stream. Household paper products with colorful patterns or different colors as the whole have become the preferred choice for young people who pursue individuality.

[0003] The production of colored tissue paper inevitably generates a large amount of waste paper during the research and development, trial production, production debugging, formal production, and downstream processing. According to traditional recycling processes, color removal from this waste paper requires specific technologies and specialized processing equipment. Currently, no tissue paper company effectively recycles colored waste paper; it is typically discarded directly, resulting in significant waste and persistently high production costs. Summary of the Invention

[0004] In view of this, this application provides a method for decolorizing colored household paper to facilitate the effective recycling of colored waste paper. This application also provides a pulp obtained by using the method for decolorizing colored household paper, which can be directly used for the production of household paper.

[0005] This application provides a method for decolorizing colored tissue paper, including the following steps: S1. Provide colored household paper; S2. Pulping: The colored tissue paper is pulped under the conditions of pulp concentration of 4%-6%, hydrogen peroxide addition of 0.5%-2%, and pH value of 9.5-11 to obtain pre-bleached pulp; S3. Oxygen Decolorization: Under the conditions of reaction concentration of 10%-13% and reaction temperature of 90-105℃, oxygen is introduced into the pre-bleached pulp for decolorization, and the oxygen dosage is 20-25 kg / ADT, to obtain the initial bleached pulp; S4. Bleaching and decolorization: Under the conditions of reaction concentration of 10%-13%, reaction temperature of 50-70℃, and pH value of 2-3, the primary bleached pulp is subjected to chlorine dioxide bleaching and decolorization, with a chlorine dioxide dosage of 20-30 kg / ADT, to obtain decolorized pulp.

[0006] As a further improvement to the above scheme, step S2 is carried out in a hydraulic pulper for a pulping time of 30-40 minutes.

[0007] As a further improvement to the above scheme, in step S2, steam is used to heat the pulp to a temperature of 60-85℃; caustic soda is added to adjust the pH value to 9.5-11.

[0008] As a further improvement to the above scheme, the S3 oxygen decolorization reaction time is 30-60 min, and 1.2%-1.8% sodium hydroxide is added to the pre-bleached pulp during the oxygen decolorization process.

[0009] As a further improvement to the above scheme, in step S3, the pre-bleached slurry is first pumped into the oxygen decolorization tank and mixed with the cooked unbleached slurry, and then the mixed slurry is sent to the oxygen reaction tower for decolorization.

[0010] As a further improvement to the above scheme, the pre-bleached slurry accounts for 5%-10% of the total amount of the mixed slurry.

[0011] As a further improvement to the above scheme, the oxygen reaction tower is an upflow oxygen drift tower with a top pressure of 0.3-0.9 MPa.

[0012] As a further improvement to the above scheme, step S4 is carried out in a chlorine dioxide bleaching tower for 2-4 hours.

[0013] This application also provides pulp obtained by any of the above-described methods for decolorizing colored household paper.

[0014] As a further improvement to the above scheme, the pulp has a brightness of 84-88% ISO, a viscosity of 800-900 ml / g, and an ash content of 0.2-0.4%.

[0015] Beneficial Effects: This application provides a method for decolorizing colored tissue paper. Based on the existing pulping and papermaking process, it achieves the decolorization of colored waste paper without the need for additional processes or equipment, thereby realizing the effective utilization of colored tissue paper waste and reducing production costs. This application also provides pulp produced using this method for decolorizing colored tissue paper, which can be directly used in the production of tissue paper. Detailed Implementation

[0016] The present application will be further described in detail below with reference to embodiments, so that the advantages and features of the present application can be more easily understood by those skilled in the art, thereby providing a clearer and more definite definition of the scope of protection of the present application. It should be particularly noted that the following embodiments are only used to illustrate the present application and do not limit the scope of the present application. Similarly, the following embodiments are only some embodiments of the present application and not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present application.

[0017] As mentioned earlier, a large amount of waste paper is inevitably generated during the R&D, trial production, production debugging, formal production, and downstream processing of colored tissue paper. According to conventional recycling processes, the colored waste paper must first undergo decolorization, which requires specific processes and even specialized equipment. Therefore, currently, no tissue paper company can effectively recycle colored waste paper. This application provides a decolorization method for colored tissue paper that achieves efficient recycling of colored waste paper without requiring specialized equipment or additional process steps.

[0018] The method for decolorizing colored household paper includes the following steps: S1. Provide colored household paper.

[0019] This colored household paper is colored waste paper generated during the process of new product development, trial production, production debugging, formal production, and back-end processing. Its color is mostly achieved by using edible pigments or natural pigments, unlike cultural paper or other packaging paper products which use direct dyes. Its color fastness is relatively low, and the difficulty of color removal is relatively small.

[0020] S2. Pulping: The colored tissue paper is pulped under the conditions of pulp concentration of 4%-6%, hydrogen peroxide addition of 0.5%-2%, and pH value of 9.5-11 to obtain pre-bleached pulp.

[0021] This step is carried out in a hydraulic pulper, and the pulping time is 30-40 minutes.

[0022] The hydraulic pulper is an existing piece of equipment in the pulping section of the tissue paper manufacturing process, used for breaking down the finished pulp board / pulp in tissue paper raw materials.

[0023] Furthermore, the pulping temperature is 60-85℃ to accelerate the process of breaking down the colored tissue paper into pulp fibers, and the heating method is steam heating.

[0024] Furthermore, caustic soda is added to adjust the pH value to 9.5-11.

[0025] S3. Oxygen Decolorization: Under the conditions of a reaction concentration of 10%-13% and a reaction temperature of 90-105℃, oxygen is introduced into the pre-bleached pulp for decolorization. The oxygen dosage is 20-25 kg / ADT, to obtain the initial bleached pulp.

[0026] Furthermore, the S3 oxygen decolorization reaction time is 30-60 minutes. During the oxygen decolorization process, 1.2%-1.8% sodium hydroxide is added to the pre-bleached pulp to accelerate the oxygen decolorization process.

[0027] In a preferred embodiment, in the oxygen decolorization step, the pre-bleached slurry is first pumped into the pre-oxygen decolorization slurry tank and mixed with the cooked unbleached slurry, and then the mixed slurry is sent to the oxygen reaction tower for oxygen decolorization.

[0028] The oxygen pre-de-slurry tank and oxygen reaction tower are existing equipment in the pulping production line of the tissue paper manufacturing process, used for bleaching treatment in the washing and bleaching section of the cooked unbleached pulp in tissue paper raw materials.

[0029] In this embodiment, the colored pre-bleached pulp is mixed with the cooked unbleached pulp and then subjected to oxygen bleaching and decolorization together. This does not add any additional process steps, and the oxygen decolorization wastewater is treated together with the original washing and bleaching section in the intermediate wastewater treatment. This method is highly operable and does not incur any additional treatment burden.

[0030] In this embodiment, the colored pre-bleached pulp is mixed with the cooked unbleached pulp and then fed into the main system for decolorization. The decolorization effect is good and has little impact on the product quality and operational performance of the original washing and bleaching section. This method for decolorizing household paper is suitable for processing large batches of waste colored household paper.

[0031] Furthermore, the pre-bleached pulp accounts for 5%-10% of the total mixed pulp. The inventors of this application have discovered that when the proportion of colored pre-bleached pulp in the mixed pulp exceeds 10%, it affects the color of the original system pulp and increases the difficulty of oxygen bleaching and decolorization of the mixed pulp. In addition, since pigments entering the intermediate wastewater increase chemical oxygen demand (COD) consumption, a proportion of colored pre-bleached pulp exceeding 10% also affects the treatment of the intermediate wastewater. However, when the amount of colored pre-bleached pulp used is less than 10%, its impact on the original washing and bleaching section is minimal. To improve treatment efficiency, the amount of pre-bleached pulp used is set to be no less than 5%.

[0032] Furthermore, the oxygen reaction tower is an upflow oxygen drift tower, into which medium-pressure steam is introduced simultaneously with oxygen, and the pressure at the top of the tower is 0.3-0.9 MPa.

[0033] S4. Bleaching and decolorization: Under the conditions of reaction concentration of 10%-13%, reaction temperature of 50-70℃, and pH value of 2-3, the primary bleached pulp is subjected to chlorine dioxide bleaching and decolorization, with a chlorine dioxide dosage of 20-30 kg / ADT, to obtain decolorized pulp.

[0034] Furthermore, the bleaching and decolorization step is carried out in a chlorine dioxide bleaching tower, with a reaction time of 2-4 hours. The chlorine dioxide bleaching tower is an existing piece of equipment in the pulping production line of the tissue paper manufacturing process, used for bleaching treatment in the washing and bleaching section of the cooked unbleached pulp in tissue paper raw materials.

[0035] Furthermore, the chlorine dioxide bleaching tower is a chlorine dioxide upflow / downflow tower.

[0036] Before being fed into the chlorine dioxide riser tower, the initial bleaching slurry passes through a medium-concentration riser, a steam ejector, and a mixer in sequence. The mixer is equipped with a ClO2 feed port.

[0037] The method for decolorizing colored household paper provided in this application adopts the existing processes and equipment of the pulping production line in the household paper manufacturing process for pulping, oxygen decolorization and bleaching decolorization. That is, based on the original pulping and papermaking process configuration, the decolorization treatment of colored waste paper can be achieved without adding additional processes and equipment, which can realize the effective utilization of colored household paper waste paper and reduce production costs.

[0038] It should be noted that the percentage concentration, amount added, dosage, and ratio in this application are all based on oven-dry slurry.

[0039] This application also provides a pulp obtained by any of the above-mentioned methods for decolorizing colored tissue paper, which can be directly used for tissue paper production.

[0040] Furthermore, the pulp has a brightness of 84-88% ISO, a viscosity of 800-900 ml / g, and an ash content of 0.2-0.4%. In addition, the tensile index, tear index, and bursting index of the pulp all meet the requirements for first-class products of the enterprise.

[0041] In this application, the standards / methods for detecting / judging the relevant physical properties of the pulp are as follows: 1. The whiteness of the pulp is tested according to GB / T8940.2-2002; the viscosity of the pulp is tested according to GBT-1548; the ash content of the pulp is tested according to GB / T742. 2. The tensile index, tear index, and bursting index of the pulp are tested according to QB / T3704, and the testing conditions are a pulp freeness of 45°SR and a sheet basis weight of 60 g / m³. 2 ; 3. Criteria for determining first-class products: When the pulp is softwood pulp, the criteria for determining tensile index, tear index, and burst index shall be the same as those for bleached sulfate softwood pulp (QB / T1678—2017); when the pulp is hardwood pulp, the criteria for determining tensile index, tear index, and burst index shall be the same as those for bleached sulfate hardwood pulp (QB / T1678—2017); when the pulp is bamboo pulp, the criteria for determining bleached sulfate bamboo pulp (GBT 24322-2009) shall be used.

[0042] The following are specific embodiments of this application: Example 1: This example provides a method for decolorizing colored tissue paper, including the following steps: S1-1. Provide colored household paper, which is waste paper with overall coloring.

[0043] S1-2. The colored tissue paper is pulped in a hydrapulper with a pulp concentration of 4%, hydrogen peroxide addition of 0.5%, pH value of 11, and steam heating to raise the pulp temperature to 60°C for 30 minutes to obtain pre-bleached pulp.

[0044] S1-3. First, the pre-bleached pulp is pumped into the oxygen decolorization tank and mixed with cooked unbleached hardwood pulp. Then, the mixed pulp is sent to the oxygen reaction tower for decolorization. Specifically, under the conditions of a reaction concentration of 12% and a reaction temperature of 105°C, oxygen is introduced into the mixed pulp for decolorization, and the reaction time is 45 minutes to obtain the initial bleached pulp.

[0045] In this embodiment, the pre-bleached slurry accounts for 5% of the total amount of the mixed slurry, the oxygen reaction tower is an upflow oxygen bleaching tower, the pressure at the top of the tower is controlled at 0.6 MPa, and the oxygen consumption is 22 kg / ADT.

[0046] S1-4. Under the conditions of reaction concentration of 10%, reaction temperature of 60℃, and pH value of 3, the primary bleached pulp is subjected to chlorine dioxide bleaching and decolorization, with a chlorine dioxide dosage of 25 kg / ADT and a reaction time of 3 h, to obtain decolorized pulp A.

[0047] Testing revealed that pulp A had a brightness of 86.9% ISO, a viscosity of 870 ml / g, an ash content of 0.24%, a tensile index of 63 N·m / g, and a tear index of 6.8 mN·m. 2 / g, bursting index is 4.0 kPa·m 2 / g.

[0048] Example 2: This example provides a method for decolorizing colored tissue paper, including the following steps: S2-1. Provide colored household paper, which is waste paper with partial coloring.

[0049] S2-2. The colored tissue paper is pulped in a hydrapulper with a pulp concentration of 5%, hydrogen peroxide addition of 1%, pH value of 9.5, and steam heating to raise the pulp temperature to 85°C for 35 minutes to obtain pre-bleached pulp.

[0050] S2-3. First, the pre-bleached pulp is pumped into the oxygen decolorization tank and mixed with the cooked unbleached bamboo pulp. Then, the mixed pulp is sent to the oxygen reaction tower for decolorization. Specifically, under the conditions of a reaction concentration of 10% and a reaction temperature of 90°C, oxygen is introduced into the mixed pulp for decolorization, and the reaction time is 30 minutes to obtain the initial bleached pulp.

[0051] In this embodiment, the pre-bleached slurry accounts for 10% of the total mixed slurry, the oxygen reaction tower is an upflow oxygen bleaching tower, the pressure at the top of the tower is controlled at 0.9 MPa, and the oxygen consumption is 25 kg / ADT.

[0052] S2-4. Under the conditions of reaction concentration of 11%, reaction temperature of 50℃, and pH value of 2, the primary bleached pulp was subjected to chlorine dioxide bleaching and decolorization, with a chlorine dioxide dosage of 30 kg / ADT and a reaction time of 4 h, to obtain decolorized pulp B.

[0053] Testing revealed that pulp B had a brightness of 87.2% ISO, a viscosity of 820 ml / g, an ash content of 0.4%, a tensile index of 64 N·m / g, and a tear index of 11.6 mN·m. 2 / g, bursting index is 3.9 kPa·m 2 / g.

[0054] Example 3: This example provides a method for decolorizing colored tissue paper, including the following steps: S3-1. Provide colored household paper, which is waste paper with partial color printing.

[0055] S3-2. The colored tissue paper is pulped in a hydrapulper with a pulp concentration of 6%, hydrogen peroxide addition of 2%, pH value of 10, and steam heating to a pulp temperature of 75°C for 40 minutes to obtain pre-bleached pulp.

[0056] S3-3. First, the pre-bleached pulp is pumped into the oxygen decolorization tank and mixed with cooked unbleached softwood pulp. Then, the mixed pulp is sent to the oxygen reaction tower for decolorization. Specifically, under the conditions of a reaction concentration of 13% and a reaction temperature of 100°C, oxygen is introduced into the mixed pulp for decolorization, and the reaction time is 60 minutes to obtain the initial bleached pulp.

[0057] In this embodiment, the pre-bleached slurry accounts for 7% of the total amount of the mixed slurry, the oxygen reaction tower is an upflow oxygen bleaching tower, the pressure at the top of the tower is controlled at 0.3 MPa, and the oxygen consumption is 20 kg / ADT.

[0058] S3-4. Under the conditions of reaction concentration of 13%, reaction temperature of 70℃, and pH value of 2.5, the primary bleached pulp was subjected to chlorine dioxide bleaching and decolorization, with a chlorine dioxide dosage of 20 kg / ADT and a reaction time of 2 h, to obtain decolorized pulp C.

[0059] Testing revealed that pulp C had a brightness of 87.8% ISO, a viscosity of 900 ml / g, an ash content of 0.2%, a tensile index of 71 N·m / g, and a tear index of 10.4 mN·m. 2 / g, bursting index is 4.9 kPa·m 2 / g.

[0060] In summary, the tensile index, tear index, and bursting index of pulp A, pulp B, and pulp C all meet the requirements for first-class products in QB / T1678-2017.

[0061] Pulp A, pulp B, and pulp C can all be directly used for the production of household paper.

[0062] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for decolorizing colored household paper, characterized in that, Includes the following steps: S1. Provide colored household paper; S2. Pulping: The colored tissue paper is pulped under the conditions of pulp concentration of 4%-6%, hydrogen peroxide addition of 0.5%-2%, and pH value of 9.5-11 to obtain pre-bleached pulp; S3. Oxygen Decolorization: Under the conditions of reaction concentration of 10%-13% and reaction temperature of 90-105℃, oxygen is introduced into the pre-bleached pulp for decolorization, and the oxygen dosage is 20-25 kg / ADT, to obtain the initial bleached pulp; S4. Bleaching and decolorization: Under the conditions of reaction concentration of 10%-13%, reaction temperature of 50-70℃, and pH value of 2-3, the primary bleached pulp is subjected to chlorine dioxide bleaching and decolorization, with a chlorine dioxide dosage of 20-30 kg / ADT, to obtain decolorized pulp.

2. The method for decolorizing colored household paper according to claim 1, characterized in that, Step S2 is carried out in a hydraulic pulper for 30-40 minutes.

3. The method for decolorizing colored household paper according to claim 1, characterized in that, In step S2, steam is used to heat the pulp to a temperature of 60-85℃; caustic soda is added to adjust the pH to 9.5-11.

4. The method for decolorizing colored household paper according to claim 1, characterized in that, The S3 oxygen decolorization reaction time is 30-60 minutes. During the oxygen decolorization process, 1.2%-1.8% sodium hydroxide is added to the pre-bleached pulp.

5. The method for decolorizing colored household paper according to claim 1, characterized in that, In step S3, the pre-bleached slurry is first pumped into the oxygen decolorization tank and mixed with the cooked unbleached slurry. The mixed slurry is then sent to the oxygen reaction tower for decolorization.

6. The method for decolorizing colored household paper according to claim 5, characterized in that, The pre-bleached slurry accounts for 5%-10% of the total volume of the mixed slurry.

7. The method for decolorizing colored household paper according to claim 5, characterized in that, The oxygen reaction tower is an upflow oxygen drift tower with a top pressure of 0.3-0.9 MPa.

8. The method for decolorizing colored household paper according to claim 1, characterized in that, Step S4 is carried out in a chlorine dioxide bleaching tower for 2-4 hours.

9. A pulp obtained by the decolorization method for colored household paper as described in any one of claims 1-8.

10. The pulp according to claim 9, characterized in that, The pulp has a brightness of 84-88% ISO, a viscosity of 800-900 ml / g, and an ash content of 0.2-0.4%.