A food carton paper finished product pulp and a method for producing the same

Abstract

The present application provides a kind of food carton paper finished pulp and its production method, the production method includes the following steps: wood raw material is sequentially washed dehydration, pre-steaming treatment, compression tear, pre-soaking treatment, first refining, bleaching, second refining, screening, concentration squeeze and remove hydrogen peroxide treatment, preparation low hydrogen peroxide balance food carton paper;Wherein, bleaching agent includes hydrogen peroxide in the bleaching, and the removal hydrogen peroxide treatment includes: biological enzyme hydrogen peroxide digestion agent.The present application first adds hydrogen peroxide in the process of bleaching to improve the high brightness of pulp, and finally removes residual hydrogen peroxide in the pulp by biological enzyme hydrogen peroxide digestion agent, to control the hydrogen peroxide balance in food carton paper.

Description

Technical Field

[0001] This invention relates to the field of papermaking technology, and in particular to a finished pulp for food-grade cardboard and its production method. Background Technology

[0002] Green food packaging is a new trend and development direction in the food packaging industry, and it is also a key area for paper manufacturers to develop food packaging paperboard. Various coated and uncoated food packaging paperboards have emerged as a result. Food contact white cardboard is mainly used as base paper for paper cups, lunch boxes, noodle bowls, lunch buckets, milk cards, aseptic liquid packaging, and oil-proof food cards, etc. The white cardboard base paper must comply with GB4806.8-2022 "National Food Safety Standard for Paper and Paperboard Materials and Products for Food Contact".

[0003] To meet the demand for lightweight paper and improve the whiteness, stiffness, and printing performance of food-grade cardboard, 50%–70% bleached chemimechanical pulp is required as a component of the fiber raw material for white cardboard. Hydrogen peroxide is the most commonly used bleaching agent for bleached chemimechanical pulp; its bleaching decomposition products are oxygen and water, offering advantages such as safety, greenness, and environmental friendliness, and it has been widely applied in the production of bleached chemimechanical pulp.

[0004] However, chemimechanical pulp has several drawbacks during production, including easy oxidation and yellowing of whiteness, low whiteness stability, and high levels of residual hydrogen peroxide in the finished pulp, which can lead to food contamination and adverse health effects after ingestion.

[0005] Therefore, it is necessary to develop a method to control the residual amount of hydrogen peroxide in food-grade cardboard. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the present invention provides a finished pulp for food-grade cardboard and its production method, which solves the problems of easy oxidation and yellowing of white cardboard raw material chemimechanical pulp, low whiteness stability, high hydrogen peroxide residue, and low cleanliness.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a production method for controlling the residual amount of hydrogen peroxide in food cardboard, the production method comprising the following steps:

[0009] Wood raw materials are sequentially subjected to washing and dehydration, pre-steaming treatment, compression and tearing, pre-impregnation treatment, first pulping, bleaching, second pulping, screening, concentration and desqueezing, and hydrogen peroxide removal treatment to prepare food-grade cardboard with low hydrogen peroxide residue; wherein, the bleaching agent in the bleaching includes hydrogen peroxide, and the hydrogen peroxide removal treatment includes: a biological enzyme hydrogen peroxide digester.

[0010] The production method for controlling the residual hydrogen peroxide in food cardboard provided by this invention uses hydrogen peroxide as the bleaching agent, which can improve the whiteness of the cardboard raw material and avoid the problem of oxidation and yellowing. Moreover, after concentration and squeezing, a biological enzyme hydrogen peroxide digester is added, which can directly digest the hydrogen peroxide in the pulp without providing additional heat, thus reducing the yellowing rate of the pulp due to the generation of chromophores induced by heat. Therefore, it has the advantages of being green and environmentally friendly, energy-saving and consumption-reducing, and having stable whiteness.

[0011] Preferably, the wood raw material includes eucalyptus chip raw material.

[0012] Preferably, the cleaning and dehydration includes: removing heavy residue and dust from the wood raw material and dehydrating it.

[0013] Preferably, the heating temperature for the pre-steaming treatment is 75-85°C, for example, 75°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C or 85°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0014] Preferably, the pre-steaming time is 25 to 35 minutes, for example, 25 minutes, 27 minutes, 28 minutes, 29 minutes, 30 minutes, 31 minutes, 32 minutes, 33 minutes, 34 minutes or 35 minutes, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0015] Preferably, the compression tearing includes: compressing and tearing the softened material after pre-steaming treatment.

[0016] Preferably, the compression tearing device includes a spiral compression tearing machine.

[0017] Preferably, the pre-impregnation solution comprises: 25-30 kg / t liquid alkali, 5-10 kg / t hydrogen peroxide, 0.4-1 kg / t hydrogen peroxide stabilizer, and 0.4-1 kg / t chelating agent.

[0018] Among them, 25-30 kg / t liquid alkali can be, for example, 25 kg / t, 25.6 kg / t, 26.2 kg / t, 26.7 kg / t, 27.3 kg / t, 27.8 kg / t, 28.4 kg / t, 28.9 kg / t, 29.5 kg / t or 30 kg / t, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] Hydrogen peroxide concentrations of 5 to 10 kg / t are used, for example, 5 kg / t, 5.6 kg / t, 6.2 kg / t, 6.7 kg / t, 7.3 kg / t, 7.8 kg / t, 8.4 kg / t, 8.9 kg / t, 9.5 kg / t, or 10 kg / t, but are not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] Hydrogen peroxide stabilizer of 0.4 to 1 kg / t, for example, 0.4 kg / t, 0.47 kg / t, 0.54 kg / t, 0.6 kg / t, 0.67 kg / t, 0.74 kg / t, 0.8 kg / t, 0.87 kg / t, 0.94 kg / t or 1 kg / t, etc., but not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0021] The chelating agent concentration is 0.4 to 1 kg / t, for example, it can be 0.4 kg / t, 0.47 kg / t, 0.54 kg / t, 0.6 kg / t, 0.67 kg / t, 0.74 kg / t, 0.8 kg / t, 0.87 kg / t, 0.94 kg / t or 1 kg / t, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] Preferably, the temperature of the pre-impregnation treatment is 85-95°C, for example, it can be 85°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C or 95°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] Preferably, the pre-soaking time is 25 to 35 minutes, for example, 25 minutes, 27 minutes, 28 minutes, 29 minutes, 30 minutes, 31 minutes, 32 minutes, 33 minutes, 34 minutes or 35 minutes, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, the concentration of hydrogen peroxide in the pre-impregnation treatment is 2-3%, the concentration of liquid alkali is 5-7%, and the concentration of wood raw material is 28-31%.

[0025] The concentration of hydrogen peroxide is 2-3%, for example, it can be 2%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9% or 3%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] The concentration of liquid alkali is 5-7%, for example, it can be 5%, 5.3%, 5.5%, 5.7%, 5.9%, 6.2%, 6.4%, 6.6%, 6.8% or 7%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] The concentration of the wood raw material is 28-31%, for example, it can be 28%, 28.4%, 28.7%, 29%, 29.4%, 29.7%, 30%, 30.4%, 30.7% or 31%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Preferably, the pulp concentration of the first pulp is 35-45%, for example, it can be 35%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44% or 45%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0029] Preferably, the first pulp is separated to obtain the first slurry.

[0030] Preferably, the separation includes the slurry after the first grinding being sprayed out under steam pressure and then separated by steam to obtain the first slurry.

[0031] Preferably, the bleaching agent further includes liquid alkali, hydrogen peroxide stabilizer, and chelating agent.

[0032] Preferably, the bleaching process includes a first-stage bleaching and a second-stage bleaching.

[0033] This invention employs an optimized two-stage bleaching method, combining spiral squeezing and washing during the two-stage bleaching process. This effectively removes dissolved residues from the pulp during bleaching, reducing the amount of bleaching chemicals required for subsequent high-brightness applications. Since the second-stage bleaching is a high-concentration process, the pulp requires a higher concentration of hydrogen peroxide to further enhance its whiteness. This necessitates adding most of the hydrogen peroxide bleaching chemicals to the second-stage bleaching step. However, by reusing the filtrate containing a large amount of residual hydrogen peroxide after the high-concentration bleaching (second stage) in the first-stage bleaching, hydrogen peroxide is recycled, reducing overall hydrogen peroxide usage and improving pulp whiteness. Furthermore, the higher residual hydrogen peroxide at the end of the second-stage bleaching process results in a slightly acidic pulp, significantly slowing down oxidation and yellowing during washing and storage. This achieves high whiteness and stable whiteness during storage.

[0034] Preferably, the bleaching agent in the first stage of bleaching includes 9-16 kg / t hydrogen peroxide, 3-6 kg / t liquid alkali, 1-2 kg / t hydrogen peroxide stabilizer, and 1-2 kg / t chelating agent.

[0035] The hydrogen peroxide concentration ranges from 9 to 16 kg / t, and can be, for example, 9 kg / t, 9.8 kg / t, 10.6 kg / t, 11.4 kg / t, 12.2 kg / t, 12.9 kg / t, 13.7 kg / t, 14.5 kg / t, 15.3 kg / t, or 16 kg / t, but is not limited to the listed values. Other unlisted values ​​within this range also apply.

[0036] Liquid alkali is 3 to 6 kg / t, for example, it can be 3 kg / t, 3.4 kg / t, 3.7 kg / t, 4 kg / t, 4.4 kg / t, 4.7 kg / t, 5 kg / t, 5.4 kg / t, 5.7 kg / t or 6 kg / t, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] Hydrogen peroxide stabilizer of 1 to 2 kg / t, for example, can be 1 kg / t, 1.2 kg / t, 1.3 kg / t, 1.4 kg / t, 1.5 kg / t, 1.6 kg / t, 1.7 kg / t, 1.8 kg / t, 1.9 kg / t or 2 kg / t, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] The chelating agent concentration is 1 to 2 kg / t, for example, it can be 1 kg / t, 1.2 kg / t, 1.3 kg / t, 1.4 kg / t, 1.5 kg / t, 1.6 kg / t, 1.7 kg / t, 1.8 kg / t, 1.9 kg / t or 2 kg / t, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] Preferably, in the first stage of bleaching, the concentration of hydrogen peroxide in the slurry is 16-20%, and the concentration of alkali solution is 30-34%.

[0040] The concentration of hydrogen peroxide is 16-20%, for example, it can be 16%, 16.5%, 16.9%, 17.4%, 17.8%, 18.3%, 18.7%, 19.2%, 19.6% or 20%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] The concentration of liquid alkali is 30-34%, for example, it can be 30%, 30.5%, 30.9%, 31.4%, 31.8%, 32.3%, 32.7%, 33.2%, 33.6% or 34%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] Preferably, the bleaching temperature is 101-105℃, for example, it can be 101℃, 101.5℃, 101.9℃, 102.4℃, 102.8℃, 103.3℃, ​​103.7℃, 104.2℃, 104.6℃ or 105℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] Preferably, the bleaching time is 85 to 95 minutes, for example, 85 minutes, 87 minutes, 88 minutes, 89 minutes, 90 minutes, 91 minutes, 92 minutes, 93 minutes, 94 minutes or 95 minutes, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] Preferably, before the first bleaching step, the first slurry is diluted to a slurry concentration of 15-18%, for example, it can be 15%, 15.4%, 15.7%, 16%, 16.4%, 16.7%, 17%, 17.4%, 17.7% or 18%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0045] Preferably, between the first-stage bleaching and the second-stage bleaching, the production method further includes: first diluting the slurry after the first-stage bleaching, and then sequentially performing a first spiral squeeze and a second dilution.

[0046] Preferably, the first dilution is to dilute to a slurry concentration of 8-12%, for example, it can be 8%, 8.5%, 8.9%, 9.4%, 9.8%, 10.3%, 10.7%, 11.2%, 11.6% or 12%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] Preferably, the first spiral extrusion is to extrude to a dryness of 30-35%, for example, it can be 30%, 30.6%, 31.2%, 31.7%, 32.3%, 32.8%, 33.4%, 33.9%, 34.5% or 35%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Preferably, the second dilution is to dilute to a slurry concentration of 27-30%, for example, it can be 27%, 27.4%, 27.7%, 28%, 28.4%, 28.7%, 29%, 29.4%, 29.7% or 30%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0049] Preferably, the bleaching agent in the two-stage bleaching process includes 50-70 kg / t hydrogen peroxide, 20-25 kg / t liquid alkali, 2-3 kg / t hydrogen peroxide stabilizer, and 2-3 kg / t chelating agent.

[0050] The hydrogen peroxide concentration is 50-70 kg / t, for example, it can be 50 kg / t, 53 kg / t, 55 kg / t, 57 kg / t, 59 kg / t, 62 kg / t, 64 kg / t, 66 kg / t, 68 kg / t or 70 kg / t, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0051] Liquid alkali is 20-25 kg / t, for example, it can be 20 kg / t, 20.6 kg / t, 21.2 kg / t, 21.7 kg / t, 22.3 kg / t, 22.8 kg / t, 23.4 kg / t, 23.9 kg / t, 24.5 kg / t or 25 kg / t, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] The amount of hydrogen peroxide stabilizer is 2 to 3 kg / t, for example, it can be 2 kg / t, 2.2 kg / t, 2.3 kg / t, 2.4 kg / t, 2.5 kg / t, 2.6 kg / t, 2.7 kg / t, 2.8 kg / t, 2.9 kg / t or 3 kg / t, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0053] The chelating agent concentration is 2-3 kg / t, for example, it can be 2 kg / t, 2.2 kg / t, 2.3 kg / t, 2.4 kg / t, 2.5 kg / t, 2.6 kg / t, 2.7 kg / t, 2.8 kg / t, 2.9 kg / t or 3 kg / t, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0054] Preferably, the temperature of the two-stage bleaching is 95-100℃, for example, it can be 95℃, 95.6℃, 96.2℃, 96.7℃, 97.3℃, 97.8℃, 98.4℃, 98.9℃, 99.5℃ or 100℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] Preferably, the bleaching time for the two stages is 110 to 130 minutes, for example, 110 minutes, 113 minutes, 115 minutes, 117 minutes, 119 minutes, 122 minutes, 124 minutes, 126 minutes, 128 minutes or 130 minutes, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0056] Preferably, in the two-stage bleaching process, the concentration of hydrogen peroxide in the slurry is 18-22%, and the concentration of alkali solution is 30-34%.

[0057] The concentration of hydrogen peroxide is 18-22%, for example, it can be 18%, 18.5%, 18.9%, 19.4%, 19.8%, 20.3%, 20.7%, 21.2%, 21.6%, or 22%, but is not limited to the listed values. Other unlisted values ​​within this range also apply. The concentration of liquid alkali is 30-34%, for example, it can be 30%, 30.5%, 30.9%, 31.4%, 31.8%, 32.3%, 32.7%, 33.2%, 33.6%, or 34%, but is not limited to the listed values. Other unlisted values ​​within this range also apply.

[0058] Preferably, between the bleaching and the second pulping, the production method further includes: subjecting the pulp after the two-stage bleaching to a second spiral extrusion.

[0059] Preferably, the second spiral extrusion is to extrude to a dryness of 30-35%, for example, 30%, 30.6%, 31.2%, 31.7%, 32.3%, 32.8%, 33.4%, 33.9%, 34.5%, or 35%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0060] Preferably, the slurry concentration of the second grinding pulp is 4 to 6%, for example, it can be 4%, 4.3%, 4.5%, 4.7%, 4.9%, 5.2%, 5.4%, 5.6%, 5.8% or 6%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0061] Preferably, the screening includes screening the slurry at a concentration of 1.0%, regrinding and recycling the screened slurry, and using the resulting second slurry for subsequent thickening and dehydration.

[0062] Preferably, the concentration and squeezing includes first concentrating the slurry to a concentration of 10-12%, such as 10%, 10.3%, 10.5%, 10.7%, 10.9%, 11.2%, 11.4%, 11.6%, 11.8%, or 12%, but not limited to the listed values. Other unlisted values ​​within this range are also applicable. Then, the slurry is squeezed to a dryness of 25% or more using a third screw, such as 25%, 26%, 26.5%, 27%, 27.5%, 28%, 29%, 29.5%, 30%, 30.5%, or 31%.

[0063] Preferably, the bio-enzyme hydrogen peroxide digester comprises a catalase-modified complex.

[0064] Preferably, the catalase-modified complex is CAS 9001-05-2.

[0065] Preferably, the concentration of the bio-enzyme hydrogen peroxide digester and the slurry is 0.15 to 0.2 kg / admt, for example, it can be 0.15 kg / admt, 0.16 kg / admt, 0.17 kg / admt, 0.18 kg / admt, 0.19 kg / admt or 0.2 kg / admt, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0066] As a preferred technical solution of the present invention, the production method includes the following steps:

[0067] (1) The eucalyptus wood chips are washed to remove the heavy residue and dust on the surface of the eucalyptus wood chips, and then dehydrated to obtain the dehydrated material.

[0068] (2) The dehydrated material described in step (1) is heated to 75-85°C and pre-steamed for 25-35 minutes to soften the eucalyptus chip raw material and obtain softened material.

[0069] (3) The softened material described in step (2) is compressed and torn using a spiral compression shredder to obtain the compressed and torn material.

[0070] (4) Add a pre-impregnation solution to a pre-impregnation tank. The pre-impregnation solution includes: 25-30 kg / t caustic soda, 5-10 kg / t hydrogen peroxide, 0.4-1 kg / t hydrogen peroxide stabilizer, and 0.4-1 kg / t chelating agent. Immerse the compressed and torn material in the pre-impregnation tank at 85-95°C for 25-35 min. The concentration of hydrogen peroxide in the pre-impregnation treatment is 2-3%, the concentration of caustic soda is 5-7%, and the concentration of wood raw material is 28-31%. The pre-impregnated material is obtained.

[0071] (5) The pre-impregnated material described in step (4) is subjected to a first grinding process. The concentration of the first grinding process is 35-45%. The slurry after the first grinding process is sprayed out with steam pressure and separated by steam-slurry separation to obtain the first slurry.

[0072] (6) First, dilute the first slurry to a slurry concentration of 15-18%, then add 9-16 kg / t hydrogen peroxide, 3-6 kg / t liquid alkali, 1-2 kg / t hydrogen peroxide stabilizer, and 1-2 kg / t chelating agent. Perform a first-stage bleaching at 101-105℃ for 85-95 minutes. During the first-stage bleaching, the concentration of hydrogen peroxide in the slurry is 16-20%, and the concentration of liquid alkali is 30-34%. Then, dilute the slurry after the first-stage bleaching to a slurry concentration of 15-18%. The pulp concentration is 8-12%, and then it is squeezed dry to 30-35% dryness using the first screw press. Then, 50-70 kg / t hydrogen peroxide, 20-25 kg / t liquid alkali, 2-3 kg / t hydrogen peroxide stabilizer and 2-3 kg / t chelating agent are added. The pulp is then subjected to a second-stage bleaching process at 95-100℃ for 110-130 min. During the second-stage bleaching, the concentration of hydrogen peroxide in the pulp is 18-22% and the concentration of liquid alkali is 30-34%, resulting in the pulp after the second-stage bleaching.

[0073] (7) The pulp is diluted to a concentration of 27-30% and then the pulp after the second bleaching is squeezed to a dryness of 30-35%. Then, the pulp is ground to a concentration of 4-6%. The pulp is then screened at a concentration of 1.0%. The slurry after screening is ground and recycled. The second pulp is used for subsequent thickening and squeezing.

[0074] (8) The second slurry is concentrated to a slurry concentration of 10-12%, and then squeezed dry by a third screw to a dryness of more than 25% to obtain the third slurry;

[0075] (9) The third slurry in step (8) is diluted with white water and a biological enzyme hydrogen peroxide digester is added to remove hydrogen peroxide and obtain the finished slurry.

[0076] (10) The finished pulp described in step (9) is manufactured to obtain food cardboard with low hydrogen peroxide content.

[0077] Optionally, the liquid phase extruded in the first, second, and third screw extrusion processes is recycled for the first-stage bleaching. This invention recycles the liquid phase extruded in the first, second, and third screw extrusion processes for the first-stage bleaching, reusing 70-80% of the residual hydrogen peroxide after bleaching. This saves on hydrogen peroxide, a bleaching agent, and reduces the amount of residual hydrogen peroxide in the pulp, which is then sent to subsequent stages. The bleaching stage employs a two-stage bleaching process. The majority of the bleaching agent is added to the second stage bleaching. The residual agent is largely recovered by recycling the second-stage pressing filtrate. Simultaneously, most of the hydrogen peroxide is added to the second stage bleaching, extending the bleaching time. This results in a slightly acidic pulp at the bleaching endpoint due to the higher hydrogen peroxide content, which slows down the oxidative yellowing of the pulp under high-temperature conditions. This achieves high and stable pulp whiteness while maintaining its overall brightness.

[0078] Secondly, the present invention provides a food cardboard, which is manufactured using the production method described in the first aspect for controlling the residual amount of hydrogen peroxide in the food cardboard.

[0079] Preferably, the residual hydrogen peroxide content in the food cardboard is 0-100 mg / L, for example, it can be 0 mg / L, 1 mg / L, 2 mg / L, 5 mg / L, 10 mg / L, 20 mg / L, 25 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, 80 mg / L, 90 mg / L or 100 mg / L, etc.

[0080] Preferably, the bulk of the food-grade cardboard is 2.56–2.61 cm. 3 / g, for example, could be 2.56cm 3 / g, 2.57cm 3 / g, 2.58cm 3 / g, 2.59cm 3 / g, 2.60cm 3 / g or 2.61cm 3 / g etc.

[0081] Preferably, the whiteness of the food cardboard is 72-73% ISO, for example, it can be 72% ISO, 72.5% ISO, 73% ISO, 73.5% ISO, 74% ISO, 74.5% ISO or 75% ISO, etc.

[0082] Preferably, the Canadian freeness of the finished food cardboard pulp is 400±20 CSF.

[0083] Preferably, the tensile index of the food-grade cardboard is 23–26 N·m / g, for example, it can be 23 N·m / g, 23.2 N·m / g, 23.3 N·m / g, 23.4 N·m / g, 23.5 N·m / g, 23.8 N·m / g, 24 N·m / g, 24.2 N·m / g, 24.5 N·m / g, 24.8 N·m / g, 25 N·m / g, 25.2 N·m / g, 25.5 N·m / g, 25.8 N·m / g, or 26 N·m / g, etc.

[0084] Compared with the prior art, the present invention has at least the following beneficial effects:

[0085] (1) The production method for controlling the residual hydrogen peroxide in food cardboard provided by the present invention adopts an optimized two-stage bleaching system. During the process, a pressing screw is used for washing, which can wash away the soluble residues in the pulp during the bleaching process and reduce the amount of bleaching chemicals required for high whiteness in the subsequent process. Since the second stage is a high-concentration bleaching process, the pulp has the characteristic that a higher amount of hydrogen peroxide is required to further improve the whiteness. This means that most of the bleaching chemicals, hydrogen peroxide, need to be added to the second-stage bleaching step. However, by reusing the filtrate containing a large amount of residual hydrogen peroxide after pressing the high-concentration bleaching (second stage) into the first-stage bleaching process, the hydrogen peroxide is recycled and reused, reducing the overall amount of hydrogen peroxide used and improving the whiteness of the pulp. Meanwhile, due to the high residual hydrogen peroxide at the end of the second-stage bleaching process, the pulp becomes weakly acidic, which greatly slows down the oxidation and yellowing rate of the pulp during washing and storage in the pulp tower. This results in high whiteness and stable whiteness during storage. Under optimal conditions, the residual hydrogen peroxide in the finished pulp is only below 63 mg / L, the whiteness is above 72% ISO, and the bulk reaches 2.66 cm. 3 / g or higher, with a tensile index of 21.12 N·m / g or higher;

[0086] (2) The production method for controlling the residual amount of hydrogen peroxide in food cardboard provided by the present invention adopts a three-stage spiral extrusion, the washing water is used in reverse, and the washing water in the later stage is recycled to the bleaching stage for washing, which improves the cleanliness of the pulp and saves pulping and washing water.

[0087] (3) The production method for controlling the residual hydrogen peroxide in food-grade cardboard provided by this invention removes residual hydrogen peroxide from the pulp by adding hydrogen peroxide as a digester. The products are oxygen and water. Furthermore, the process of digesting hydrogen peroxide does not require additional heat for the reaction, reducing the rate of yellowing caused by heat-induced chromophores in the pulp. Therefore, it has the advantages of being green and environmentally friendly, energy-saving and consumption-reducing, and having stable whiteness. The pulp has high cleanliness and low chemical residue, achieving high whiteness while also meeting national food safety standards. Attached Figure Description

[0088] Figure 1 This is a flowchart of a production method for controlling the residual amount of hydrogen peroxide in food cardboard, provided in Embodiment 1 of the present invention. Detailed Implementation

[0089] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0090] It should be understood that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0091] The following examples and comparative examples used the following chemicals in the production process: hydrogen peroxide (27.5% concentration), liquid alkali (32% NaOH concentration), hydrogen peroxide stabilizer (heptasodium diethylenetriaminepentamethylenephosphonate, CAS 68155-78-2), chelating agent (pentasodium diethylenetriaminepentaacetate, CAS 140-01-2), and bio-enzyme hydrogen peroxide digester (CAS 9001-05-2), all at a concentration of 100% and a pH of 4.2. In actual use, the concentration was diluted to 15-20 ppm, and the pH was 6.5-7. All amounts of hydrogen peroxide, liquid alkali, and hydrogen peroxide digester mentioned herein are measured at 100% concentration, in kg / octane tonnes.

[0092] In the following examples and comparative examples, an annual production capacity of 300,000 tons / year of PRCAPMP was achieved online, with the main equipment supplier being ANDRITZ.

[0093] Example 1

[0094] This embodiment provides a production method for controlling the residual hydrogen peroxide in food-grade cardboard. (See also...) Figure 1 The production method includes the following steps:

[0095] (1) Eucalyptus raw material (100% domestic eucalyptus, chip size (length and width 11-40mm, thickness 3-5mm, proportion of good chips conforming to size > 88%, sawdust rate ≤ 1%, overall sawdust size length, width and thickness < 4.8mm)) is conveyed into the wood chip silo in the workshop by belt, and then enters the wood chip double-stage washer by conveying screw, and is washed at 80℃ to remove heavy residue and dust on the surface of the eucalyptus raw material. Then, it is dehydrated by three dehydration screws to obtain the dehydrated material.

[0096] (2) The dehydrated material described in step (1) is sent into a pre-steaming chamber and heated to 80°C and pre-steamed for 30 minutes to soften the eucalyptus chip raw material and obtain softened material.

[0097] (3) The wood chips are compressed and torn by applying axial pressure and shear force to the softened material in step (2) with a torque of 350 kNm using a spiral compression shredder (ANDRITZ MSD600) to obtain the compressed and torn material.

[0098] (4) The compressed and torn material described in step (3) is fed into a pre-impregnation tank. A pre-impregnation solution is added to the pre-impregnation tank. The pre-impregnation solution includes: 26 kg / t liquid alkali, 8 kg / t hydrogen peroxide, 0.5 kg / t hydrogen peroxide stabilizer, and 0.5 kg / t chelating agent. The compressed and torn material is then immersed in the pre-impregnation tank and pre-impregnated at 90°C for 30 min. The concentration of hydrogen peroxide in the pre-impregnation treatment is 2%, the concentration of liquid alkali is 5%, and the concentration of wood raw material is 30%. The pre-impregnated material is obtained.

[0099] (5) The pre-impregnated material described in step (4) enters a high-consistency refiner (model TX68, supplier ANDRITZ) for the first refinement. The grinding chamber pressure of the refiner is 300 kPa, the concentration of the first refinement is 40%, and the slurry after the first refinement is sprayed out with steam pressure and separated by a cyclone separator (model Plug Screw Discharger 800, supplier ANDRITZ) to recover the steam and obtain the first slurry (Canadian freeness 750±30 CSF, ISO whiteness range 30~35%).

[0100] (6) First, dilute the first slurry to a slurry concentration of 17%, then add 12 kg / t hydrogen peroxide, 5 kg / t liquid alkali, 1.5 kg / t hydrogen peroxide stabilizer and 1.5 kg / t chelating agent, and perform a first-stage bleaching at 100℃ for 90 min. During the first-stage bleaching, the concentration of hydrogen peroxide in the slurry is 19% and the concentration of liquid alkali is 32%. Then, dilute the slurry after the first-stage bleaching to a slurry concentration of 10%, and then squeeze it dry with a screw press to 32% dryness. Then add 60 kg / t hydrogen peroxide, 22 kg / t liquid alkali, 2.5 kg / t hydrogen peroxide stabilizer and 3 kg / t chelating agent, and perform a second-stage bleaching at 95℃ for 120 min. During the second-stage bleaching, the concentration of hydrogen peroxide in the slurry is 20% and the concentration of liquid alkali is 32%, thus obtaining the slurry after the second-stage bleaching.

[0101] (7) The pulp is diluted to a concentration of 28% and then the pulp after the second bleaching is squeezed to a dryness of 32%. Then, it is ground again at a pulp concentration of 5%. The pulp is then screened at a concentration of 1.0%. The slurry after screening is ground and recycled. The second pulp is used for subsequent thickening and squeezing.

[0102] (8) The second slurry is concentrated to a slurry concentration of 11%, and then squeezed dry by a third screw to a dryness of more than 25% to obtain the third slurry;

[0103] (9) The third slurry in step (8) is diluted with water and a biological enzyme hydrogen peroxide digester is added to remove hydrogen peroxide and obtain the finished slurry.

[0104] (10) The finished pulp described in step (9) is manufactured to obtain food cardboard with low hydrogen peroxide content;

[0105] Furthermore, the liquid phase extruded during the first, second, and third spiral extrusion processes is recycled for a bleaching stage.

[0106] Example 2

[0107] This embodiment provides a production method for controlling the residual hydrogen peroxide in food-grade cardboard, the production method comprising the following steps:

[0108] (1) Eucalyptus raw material (100% domestic eucalyptus, chip size (length and width 11-30mm, thickness 3-4mm, proportion of good chips conforming to size > 88%, sawdust rate ≤ 1%, overall sawdust size length, width and thickness < 4.0mm)) is conveyed into the wood chip silo in the workshop by belt, and then enters the wood chip double-stage washer by conveying screw, and is washed at 75℃ to remove heavy residue and dust on the surface of the eucalyptus raw material. Then, it is dehydrated by three dehydration screws to obtain the dehydrated material.

[0109] (2) The dehydrated material described in step (1) is sent into a pre-steaming chamber and heated to 85°C and pre-steamed for 25 minutes to soften the eucalyptus chip raw material and obtain softened material.

[0110] (3) The wood chips are compressed and torn by applying axial pressure and shear force to the softened material in step (2) with a torque of 300 kNm using a spiral compression shredder (ANDRITZ MSD600) to obtain the compressed and torn material.

[0111] (4) The compressed and torn material described in step (3) is fed into a pre-impregnation tank. A pre-impregnation solution is added to the pre-impregnation tank. The pre-impregnation solution includes: 30 kg / t liquid alkali, 5 kg / t hydrogen peroxide, 0.4 kg / t hydrogen peroxide stabilizer, and 1 kg / t chelating agent. The compressed and torn material is then immersed in the pre-impregnation tank and pre-impregnated at 95°C for 35 min. The concentration of hydrogen peroxide in the pre-impregnation treatment is 3%, the concentration of liquid alkali is 7%, and the concentration of wood raw material is 31%. The pre-impregnated material is obtained.

[0112] (5) The pre-impregnated material described in step (4) enters a high-consistency refiner (model TX68, supplier ANDRITZ) for the first refinement. The grinding chamber pressure of the refiner is 300 kPa, the concentration of the first refinement is 45%, and the slurry after the first refinement is sprayed out with steam pressure and separated by a cyclone separator (model Plug Screw Discharger800, supplier ANDRITZ) to recover the steam and obtain the first slurry (Canadian freeness 750±30 CSF, ISO whiteness range 30~35%).

[0113] (6) First, dilute the first slurry to a slurry concentration of 15%, then add 9 kg / t hydrogen peroxide, 3 kg / t liquid alkali, 1 kg / t hydrogen peroxide stabilizer and 2 kg / t chelating agent, and perform a first-stage bleaching at 101℃ for 85 min. During the first-stage bleaching, the concentration of hydrogen peroxide in the slurry is 16% and the concentration of liquid alkali is 30%. Then, dilute the slurry after the first-stage bleaching to a slurry concentration of 12%, and then squeeze it dry to 35% dryness. Then add 70 kg / t hydrogen peroxide, 20 kg / t liquid alkali, 2 kg / t hydrogen peroxide stabilizer and 2 kg / t chelating agent, and perform a second-stage bleaching at 100℃ for 110 min. During the second-stage bleaching, the concentration of hydrogen peroxide in the slurry is 22% and the concentration of liquid alkali is 34%, thus obtaining the slurry after the second-stage bleaching.

[0114] (7) The pulp is diluted to a concentration of 27% and then the pulp after the second bleaching is squeezed to a dryness of 30%. Then, it is ground again at a pulp concentration of 6%. The pulp is then screened at a concentration of 1.0%. The slurry after screening is ground and recycled. The second pulp is used for subsequent thickening and squeezing.

[0115] (8) The second slurry is concentrated to a slurry concentration of 12%, and then squeezed dry by a third screw to a dryness of more than 25% to obtain the third slurry;

[0116] (9) The third slurry in step (8) is diluted with water and a biological enzyme hydrogen peroxide digester is added to remove hydrogen peroxide and obtain the finished slurry.

[0117] (10) The finished pulp described in step (9) is manufactured to obtain food cardboard with low hydrogen peroxide content;

[0118] Furthermore, the liquid phase extruded during the first, second, and third spiral extrusion processes is recycled for a bleaching stage.

[0119] Example 3

[0120] This embodiment provides a production method for controlling the residual hydrogen peroxide in food-grade cardboard, the production method comprising the following steps:

[0121] (1) Eucalyptus raw material (100% domestic eucalyptus, chip size (length and width 11-30mm, thickness 3-4mm, proportion of good chips conforming to size > 88%, sawdust rate ≤ 1%, overall sawdust size length, width and thickness < 4.0mm)) is conveyed into the wood chip silo in the workshop by belt, and then enters the wood chip double-stage washer by conveying screw, and is washed at 85℃ to remove heavy residue and dust on the surface of the eucalyptus raw material. Then, it is dehydrated by three dehydration screws to obtain the dehydrated material.

[0122] (2) The dehydrated material described in step (1) is sent into a pre-steaming chamber and heated to 75°C and pre-steamed for 35 minutes to soften the eucalyptus chip raw material and obtain softened material.

[0123] (3) The wood chips are compressed and torn by applying axial pressure and shear force to the softened material in step (2) with a torque of 350 kNm using a spiral compression shredder (ANDRITZ MSD600) to obtain the compressed and torn material.

[0124] (4) The compressed and torn material described in step (3) is fed into a pre-impregnation tank. A pre-impregnation solution is added to the pre-impregnation tank. The pre-impregnation solution includes: 25 kg / t liquid alkali, 10 kg / t hydrogen peroxide, 1 kg / t hydrogen peroxide stabilizer, and 0.4 kg / t chelating agent. The compressed and torn material is then immersed in the pre-impregnation tank and pre-impregnated at 85°C for 25 min. The concentration of hydrogen peroxide in the pre-impregnation treatment is 2%, the concentration of liquid alkali is 5%, and the concentration of wood raw material is 28%. The pre-impregnated material is obtained.

[0125] (5) The pre-impregnated material described in step (4) enters a high-consistency refiner (model TX68, supplier ANDRITZ) for the first refinement. The grinding chamber pressure of the refiner is 300 kPa, the concentration of the first refinement is 35%, and the slurry after the first refinement is sprayed out with steam pressure and separated by a cyclone separator (model Plug Screw Discharger800, supplier ANDRITZ) to recover the steam and obtain the first slurry (Canadian freeness 750±30 CSF, ISO whiteness range 30~35%).

[0126] (6) First, dilute the first slurry to a slurry concentration of 18%, then add 16 kg / t hydrogen peroxide, 6 kg / t liquid alkali, 2 kg / t hydrogen peroxide stabilizer and 1 kg / t chelating agent, and perform a first-stage bleaching at 105℃ for 95 min. During the first-stage bleaching, the concentration of hydrogen peroxide in the slurry is 20% and the concentration of liquid alkali is 34%. Then, dilute the slurry after the first-stage bleaching to a slurry concentration of 8%, and then squeeze it dry to 30% dryness. Then add 50 kg / t hydrogen peroxide, 25 kg / t liquid alkali, 2.5 kg / t hydrogen peroxide stabilizer and 2.5 kg / t chelating agent, and perform a second-stage bleaching at 95℃ for 130 min. During the second-stage bleaching, the concentration of hydrogen peroxide in the slurry is 18% and the concentration of liquid alkali is 31.5%, thus obtaining the slurry after the second-stage bleaching.

[0127] (7) The pulp is diluted to a concentration of 28.8% and then the pulp after the second bleaching is squeezed to 35% dryness. Then, it is ground again at a pulp concentration of 5.5%. The pulp is then screened at a concentration of 1.0%. The slurry after screening is ground and recycled. The second pulp is used for subsequent thickening and squeezing.

[0128] (8) The second slurry is concentrated to a slurry concentration of 10%, and then squeezed dry by a third screw to a dryness of more than 25% to obtain the third slurry;

[0129] (9) The third slurry in step (8) is diluted with water and a biological enzyme hydrogen peroxide digester is added to remove hydrogen peroxide and obtain the finished slurry.

[0130] (10) The finished pulp described in step (9) is manufactured to obtain food cardboard with low hydrogen peroxide content;

[0131] Furthermore, the liquid phase extruded during the first, second, and third spiral extrusion processes is recycled for a bleaching stage.

[0132] Example 4

[0133] This embodiment provides a production method for controlling the residual amount of hydrogen peroxide in food cardboard. The production method is the same as that in Embodiment 1 except that the first spiral extrusion is not performed, and will not be described again here.

[0134] Example 5

[0135] This embodiment provides a production method for controlling the residual amount of hydrogen peroxide in food cardboard. The production method is the same as that in Embodiment 1 except that the second spiral extrusion is not performed, and will not be described again here.

[0136] Example 6

[0137] This embodiment provides a production method for controlling the residual amount of hydrogen peroxide in food cardboard. The production method is the same as that in Embodiment 1 except that the third spiral extrusion is not performed, and will not be described again here.

[0138] Example 7

[0139] This embodiment provides a production method for controlling the residual amount of hydrogen peroxide in food cardboard. Except for the fact that the liquid phase extruded in the first spiral extrusion, second spiral extrusion and third spiral extrusion is not reused for a first-stage bleaching, the rest of the production method is the same as in Example 1, and will not be described again here.

[0140] Example 8

[0141] This embodiment provides a production method for controlling the residual amount of hydrogen peroxide in food cardboard. Except for the concentration of hydrogen peroxide in the pulp during the two-stage bleaching process being 15%, the production method is the same as in Embodiment 1, and will not be repeated here.

[0142] Example 9

[0143] This embodiment provides a production method for controlling the residual amount of hydrogen peroxide in food cardboard. Except for the concentration of hydrogen peroxide in the pulp during the two-stage bleaching process being 25%, the production method is the same as in Example 1, and will not be repeated here.

[0144] Example 10

[0145] This embodiment provides a production method for controlling the residual amount of hydrogen peroxide in food cardboard. Except for the concentration of hydrogen peroxide in the pulp during the first bleaching stage being 10%, the production method is the same as in Embodiment 1, and will not be repeated here.

[0146] Example 11

[0147] This embodiment provides a production method for controlling the residual amount of hydrogen peroxide in food cardboard. Except for the concentration of hydrogen peroxide in the pulp during the first bleaching stage being 21%, the production method is the same as in Example 1, and will not be repeated here.

[0148] Example 12

[0149] This embodiment provides a production method for controlling the residual amount of hydrogen peroxide in food cardboard. Except for the use of a single bleaching stage, the production method is the same as that in Embodiment 1, and will not be repeated here.

[0150] Comparative Example 1

[0151] This comparative example provides a production method for controlling the residual amount of hydrogen peroxide in food cardboard. The production method is the same as in Example 1, except that the biological enzyme hydrogen peroxide digester is replaced with sodium sulfite. It will not be described again here.

[0152] The physical properties of the finished slurry with added hydrogen peroxide as a digester according to this invention are as follows: Canadian Freeness 400±20 CSF, bulk 2.5~2.8cm. 3 / g, tensile strength >20 N·m / g, ISO whiteness 73-75%. PCD absolute value <2000ueq / L (based on 5% pulp concentration), COD≤4000mg / L (based on 5% pulp concentration), pH value 5.5-7.5.

[0153] The control effects of residual hydrogen peroxide, amount of hydrogen peroxide digester, pH, whiteness % ISO, bulk and tensile index in the pulp of the above embodiments and comparative examples are compared in Table 1 below.

[0154] Table 1

[0155]

[0156] The following points can be observed from Table 1:

[0157] (1) As can be seen from Examples 1-3, the present invention, by selecting appropriate amounts of liquid alkali and hydrogen peroxide for use in key process control, can achieve a good pulping enhancement effect. Moreover, in conjunction with the use of a high-efficiency hydrogen peroxide digester, it can impart good strength, brightness, and product quality to the finished pulp. The residual hydrogen peroxide in the finished pulp is only below 63 mg / L, the brightness is above 72% ISO, and the bulk reaches 2.66 cm. 3 / g or higher, with a tensile index of 21.12 N·m / g or higher;

[0158] (2) As can be seen from Examples 1 and 4-6, in Example 4, the absence of the first spiral squeeze resulted in the inability to remove the dirty filtrate (mainly lignin oxidation and degradation products generated during the bleaching process) from the first stage of bleaching, affecting the subsequent improvement of overall brightness. Compared with Example 1, the brightness decreased. In addition, the absence of the dirty filtrate from the first stage of bleaching resulted in a higher residual hydrogen peroxide in the pulp. In Example 5, the absence of the second spiral squeeze resulted in the inability to remove the dirty filtrate (mainly lignin oxidation and degradation products generated during the bleaching process) from the second stage of bleaching, affecting the subsequent improvement of overall brightness. Since the second stage of bleaching basically completed the overall bleaching, the brightness of Example 4 was high, but it was still lower than that of Example 1. Furthermore, the second stage of bleaching itself requires the highest amount of hydrogen peroxide. Without removing the dirty filtrate, the residual hydrogen peroxide in the pulp was high. In Example 6, the absence of the third spiral squeeze resulted in the inability to further remove the dirty filtrate (mainly lignin oxidation and degradation products generated during the bleaching process) remaining from the first two stages of bleaching, affecting the improvement of the overall brightness of the pulp. However, it retains more fine fibers, resulting in a decrease in pulp bulk and thickness, but an increase in tensile strength. Furthermore, the three-stage spiral extrusion process does not remove the dirty filtrate, leading to a higher residual hydrogen peroxide content in the pulp. This indicates that the preferred three-stage spiral extrusion design of this invention allows for better control of the residual hydrogen peroxide in food-grade cardboard.

[0159] (3) It can be seen from the combined examples 1 and 7 that in Example 7, no reflux is performed, and the residual hydrogen peroxide in the bleaching process cannot be effectively recovered and reused. Although the amount of dirty filtrate carried to the front end is reduced, the overall bleaching effect is still not as good as that of reflux.

[0160] (4) It can be seen from the combined examples 1 and 8-12 that in examples 8-11, the hydrogen peroxide content in the first and second stages of bleaching is not within the preferred range, which ultimately leads to a higher whiteness or hydrogen peroxide residue in the finished pulp. In example 12, although the hydrogen peroxide in the pulp is reduced due to the use of only one stage of bleaching, the overall whiteness does not meet the requirements. This shows that the present invention preferably uses two stages of bleaching and combines it with three stages of spiral extrusion to better control the residual hydrogen peroxide in food cardboard.

[0161] (5) It can be seen from the combined results of Example 1 and Comparative Example 1 that sodium sulfite was used to eliminate hydrogen peroxide in Comparative Example 1, and the amount of sodium sulfite used was as high as 39.5 kg / admt, which is hundreds of times higher than the 0.2 kg / admt in Example 1, and the thickness of the loose material was reduced.

[0162] The present invention has been illustrated with the above embodiments to illustrate its detailed features, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the selected technical features, additions of auxiliary technical features, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A production method for controlling the residual hydrogen peroxide in food cardboard, characterized in that, The production method includes the following steps: The wood raw materials are sequentially washed and dehydrated, pre-steamed, compressed and torn, pre-impregnated, first pulping, bleaching, second pulping, screening, concentrated and squeezed dry, and hydrogen peroxide removal to obtain food cardboard finished pulp. The finished pulp is then used to manufacture food cardboard with low hydrogen peroxide residue. The bleaching agent in the bleaching process includes hydrogen peroxide, and the hydrogen peroxide removal treatment includes a biological enzyme hydrogen peroxide digester. The bleaching process includes a first-stage bleaching and a second-stage bleaching. In the first-stage bleaching, the concentration of hydrogen peroxide in the slurry is 16-20%, and the concentration of alkali solution is 30-34%. In the second-stage bleaching, the concentration of hydrogen peroxide in the slurry is 18-22%, and the concentration of alkali solution is 30-34%. Between the first-stage bleaching and the second-stage bleaching, the production method further includes: first diluting the slurry after the first-stage bleaching, and then sequentially performing the first spiral extrusion and the second dilution. Between the bleaching and the second pulping, the production method further includes: subjecting the pulp after the two-stage bleaching to a second spiral squeeze; The concentration and desizing process involves first concentrating the slurry to a concentration of 10-12%, and then desizing it with a third screw to a dryness of over 25%. The bio-enzyme hydrogen peroxide digester includes a catalase-modified complex; the catalase-modified complex is CAS 9001-05-2; The concentration of the bio-enzyme hydrogen peroxide digester and the slurry is 0.15~0.2 kg / admt; The residual hydrogen peroxide content in the finished food-grade cardboard pulp is less than 63 mg / L.

2. The production method according to claim 1, characterized in that, The wood raw materials include eucalyptus chip raw materials.

3. The production method according to claim 1, characterized in that, The cleaning and dehydration process includes: removing heavy dust and debris from the woody raw materials and then dehydrating them.

4. The production method according to claim 1, characterized in that, The heating temperature for the pre-steaming treatment is 75~85℃.

5. The production method according to claim 1, characterized in that, The pre-steaming treatment time is 25-35 minutes.

6. The production method according to claim 1, characterized in that, The compression tearing includes: compressing and tearing the softened material after pre-steaming treatment.

7. The production method according to claim 1, characterized in that, The compression tearing device includes a spiral compression tearing machine.

8. The production method according to claim 1, characterized in that, The pre-impregnation solution includes: 25~30 kg / t liquid alkali, 5~10 kg / t hydrogen peroxide, 0.4~1 kg / t hydrogen peroxide stabilizer, and 0.4~1 kg / t chelating agent.

9. The production method according to claim 1, characterized in that, The temperature of the pre-impregnation treatment is 85~95℃.

10. The production method according to claim 1, characterized in that, The pre-soaking treatment time is 25-35 minutes.

11. The production method according to claim 8, characterized in that, The concentration of hydrogen peroxide in the pre-impregnation treatment is 2-3%, the concentration of liquid alkali is 5-7%, and the concentration of wood raw material is 28-31%.

12. The production method according to claim 1, characterized in that, The first pulp has a pulp concentration of 35-45%.

13. The production method according to claim 1, characterized in that, After the first grinding, the pulp is separated to obtain the first slurry.

14. The production method according to claim 13, characterized in that, The separation process involves the first pulping process followed by steam pressure spraying out the pulp, which is then separated by steam to obtain the first pulp.

15. The production method according to claim 1, characterized in that, The bleaching agent also includes liquid alkali, hydrogen peroxide stabilizer, and chelating agent.

16. The production method according to claim 1, characterized in that, The bleaching agent in the first stage of bleaching includes 9~16 kg / t hydrogen peroxide, 3~6 kg / t liquid alkali, 1~2 kg / t hydrogen peroxide stabilizer and 1~2 kg / t chelating agent.

17. The production method according to claim 1, characterized in that, The bleaching temperature for that section is 101~105℃.

18. The production method according to claim 1, characterized in that, The bleaching time for this stage is 85-95 minutes.

19. The production method according to claim 13, characterized in that, Before the first bleaching step, the first slurry is diluted to a slurry concentration of 15-18%.

20. The production method according to claim 1, characterized in that, The first dilution is to dilute to a slurry concentration of 8-12%.

21. The production method according to claim 1, characterized in that, The first spiral extrusion is performed to extrude to a dryness of 30-35%.

22. The production method according to claim 1, characterized in that, The second dilution is to dilute to a slurry concentration of 27-30%.

23. The production method according to claim 1, characterized in that, The bleaching agent in the two-stage bleaching process includes 50-70 kg / t hydrogen peroxide, 20-25 kg / t liquid alkali, 2-3 kg / t hydrogen peroxide stabilizer, and 2-3 kg / t chelating agent.

24. The production method according to claim 1, characterized in that, The temperature for the second stage of bleaching is 95~100℃.

25. The production method according to claim 1, characterized in that, The bleaching time for the two stages is 110-130 minutes.

26. The production method according to claim 1, characterized in that, The second spiral extrusion is to extrude the material to a dryness of 30-35%.

27. The production method according to claim 1, characterized in that, The slurry concentration of the second grinding pulp is 4-6%.

28. The production method according to claim 1, characterized in that, The screening process includes screening the slurry at a concentration of 1.0%, regrinding and recycling the screened slurry, and using the resulting second slurry for subsequent thickening and dehydration.

29. The production method according to claim 1, characterized in that, The production method includes the following steps: (1) The eucalyptus wood chips are washed to remove heavy residue and dust from the surface of the eucalyptus wood chips, and then dehydrated to obtain the dehydrated material; (2) The dehydrated material described in step (1) is heated to 75~85℃ and pre-steamed for 25~35 minutes to soften the eucalyptus chip raw material and obtain softened material; (3) The softened material described in step (2) is compressed and torn using a spiral compression shredder to obtain the compressed and torn material; (4) Add pre-impregnation solution to the pre-impregnation tank, the pre-impregnation solution comprising: 25~30 kg / t liquid alkali, 5~10 kg / t hydrogen peroxide, 0.4~1 kg / t hydrogen peroxide stabilizer and 0.4~1 kg / t chelating agent; and immerse the compressed and torn material in the pre-impregnation tank for pre-impregnation treatment at 85~95℃ for 25~35 min, wherein the concentration of hydrogen peroxide in the pre-impregnation treatment is 2~3%, the concentration of liquid alkali is 5~7% and the concentration of wood raw material is 28~31%, to obtain the pre-impregnated material; (5) The pre-impregnated material described in step (4) is subjected to a first grinding process. The concentration of the first grinding process is 35-45%. The slurry after the first grinding process is sprayed out with steam pressure and separated by steam-slurry separation to obtain the first slurry. (6) First, dilute the first slurry to a slurry concentration of 15-18%, then add 9-16 kg / t hydrogen peroxide, 3-6 kg / t liquid alkali, 1-2 kg / t hydrogen peroxide stabilizer, and 1-2 kg / t chelating agent. Perform a first-stage bleaching at 101-105℃ for 85-95 minutes. During the first-stage bleaching, the concentration of hydrogen peroxide in the slurry is 16-20%, and the concentration of liquid alkali is 30-34%. Then, dilute the slurry after the first-stage bleaching to a slurry concentration of 8-12%. The pulp is then squeezed dry to 30-35% dryness using a first screw press and then diluted to a pulp concentration of 27-30%. Next, 50-70 kg / t hydrogen peroxide, 20-25 kg / t liquid alkali, 2-3 kg / t hydrogen peroxide stabilizer, and 2-3 kg / t chelating agent are added. The pulp is then subjected to a two-stage bleaching process at 95-100℃ for 110-130 minutes. During the two-stage bleaching, the concentration of hydrogen peroxide in the pulp is 18-22%, and the concentration of liquid alkali is 30-34%, resulting in a bleached pulp. (7) The pulp after the second stage of bleaching is squeezed dry to 30-35% dryness by a second screw, and then the pulp is ground at 4-6% pulp concentration. The pulp is then screened at 1.0% concentration. The slurry after screening is ground and recycled. The second pulp is used for subsequent thickening and squeezing. (8) The second slurry is concentrated to a slurry concentration of 10-12%, and then squeezed dry with a third screw to a dryness of more than 25% to obtain the third slurry; (9) The third slurry in step (8) is diluted with white water and a biological enzyme hydrogen peroxide digester is added to remove hydrogen peroxide and obtain the finished slurry. (10) The finished pulp described in step (9) is manufactured to obtain food cardboard with low hydrogen peroxide content.

30. A finished pulp for food-grade cardboard, characterized in that, The finished pulp of the food cardboard is prepared using the finished pulp preparation process described in any one of claims 1 to 29, which is a production method for controlling the residual amount of hydrogen peroxide in food cardboard.

31. The finished food-grade cardboard pulp according to claim 30, characterized in that, The bulk of the finished food-grade cardboard pulp is 2.56~2.61cm. 3 / g.

32. The finished food-grade cardboard pulp according to claim 30, characterized in that, The ISO whiteness of the finished food-grade cardboard pulp is 72-73%.

33. The finished food-grade cardboard pulp according to claim 30, characterized in that, The Canadian freeness of the finished food cardboard pulp is 400±20 CSF.

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