A production process of high-performance low-basis weight wet-strength recycled kraft paper by secondary fiber papermaking

Abstract

The application discloses a production process of secondary fiber high-performance low-basis weight wet-strength recycled kraft paper, and aims at solving the technical problem of high material cost and high production energy consumption caused by the fact that the existing high-strength wet-strength paper is generally produced by using 100% virgin wood pulp as raw material. The application comprises the following steps: preparing raw materials, wherein the raw materials comprise American waste recycled pulp board or American waste 12 / 13# and virgin coniferous wood pulp; preparing the American waste recycled pulp board or American waste 12 / 13# into first pulp by a preset first pulping process, preparing the virgin coniferous wood pulp into second pulp by a preset second pulping process, and mixing the first pulp and the second pulp at a paper machine feeding system to become papermaking pulp; adding retention and drainage aids, in-pulp sizing agent and wet-strength agent into the papermaking pulp; conveying the papermaking pulp to a paper machine through the paper machine feeding system, and performing papermaking, squeezing dewatering, drying, sizing and calendering processes on the papermaking pulp by the paper machine, so that the kraft paper product is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of papermaking, in particular to a production process for making high-performance, low-basis-weight, wet-strength recycled kraft paper from secondary fibers. Background Art

[0002] Traditional high-strength wet-strength paper is generally produced using 100% virgin wood pulp (usually mechanical pulp and chemical pulp) as raw material. Its raw material cost and production energy consumption are relatively high. In the current dual-carbon context, traditional high-strength wet-strength paper production still faces problems such as high consumption of virgin wood pulp, high pollution, and high energy consumption.

[0003] Therefore, finding a technical solution that can solve the above technical problems has become an important topic studied by those skilled in the art. Summary of the Invention

[0004] The embodiments of the present invention disclose a production process for high-performance, low-basis-weight wet-strength recycled kraft paper made from secondary fibers, which is used to solve the technical problem that existing high-strength wet-strength paper is generally produced using 100% virgin wood pulp as raw material, resulting in high raw material costs and production energy consumption.

[0005] The present invention provides a production process for producing high-performance, low-basis-weight, wet-strength recycled kraft paper from secondary fibers, comprising the following steps:

[0006] S1. Prepare raw materials, wherein the raw materials include 50%-60% of recycled pulp from US waste or US waste 12 / 13# and 40%-50% of virgin softwood pulp;

[0007] S2. Using recycled pulp from US waste or US waste 12 / 13# to prepare a first pulp, using virgin softwood pulp to prepare a second pulp through a preset second pulping process, and mixing the first pulp and the second pulp at a paper machine loading system to prepare papermaking pulp;

[0008] S3. Adding retention and drainage aids, internal sizing agents, and wet strength agents into the papermaking pulp;

[0009] S4. The papermaking pulp is transported to the paper machine through the paper machine feeding system. The wire section of the paper machine dehydrates and integrates the papermaking pulp to form a wet paper web. The press section of the paper machine presses and dehydrates the wet paper web. Subsequently, the front drying device of the paper machine dries the paper web to obtain base paper. The sizing device of the paper machine applies sizing to the surface of the base paper. Finally, the back drying device of the paper machine dries the base paper for a second time. The base paper is then calendered by the calendering device to obtain the finished kraft paper.

[0010] Optionally, between step S2 and step S1, the following steps are further included:

[0011] A mixture of 1.3% sodium hydroxide and 0.7% disodium hydrogen phosphate is added to the clean water in the treatment tank to form an alkaline solution. The pH value of the alkaline solution is controlled between 8-10 and the temperature of the alkaline solution is greater than 65°C.

[0012] Place the US waste recycled paddle board or US waste 12 / 13# into the treatment tank and soak it in alkali solution for a preset time.

[0013] Optionally, in step S2, the first pulping process specifically includes the following steps:

[0014] a1. Pulp the recycled paddle or 12 / 13# waste from the US and transport it to the high-concentration cleaner;

[0015] a2. The pulp after being processed by the high-concentration cleaner is subjected to coarse screening and graded screening in sequence, and the graded screened pulp is transported to the low-concentration cleaner;

[0016] a3. The slurry treated by the low-concentration cleaner is finely screened and sent to a multi-disc thickener. After being treated by the multi-disc thickener, it is thermally dispersed and finally subjected to a disc grinding and beating process to form a first slurry.

[0017] Optionally, the first pulping process includes the following parameters:

[0018] The crushing concentration of the first slurry is controlled between 4-6%;

[0019] The pressure difference during the coarse screening process is controlled at 20-30kPa; the pressure difference during the graded screening process is controlled at 10-20kPa; the pressure difference during the fine screening process is controlled at 15-25kPa;

[0020] The pulp concentration of the multi-disc thickener is controlled at 0.5-0.8%, the pulp dryness out of the pressing screw is not less than 30%, and the torque is controlled between 30-50%;

[0021] The preheating temperature during the heat dispersion process is not lower than 95°C, and the back pressure is controlled at 150-180kPa;

[0022] The feed power during the disc grinding process is controlled at 600-800 kW, the beating concentration of the first pulp is controlled at 4-6%, and the beating degree of the first pulp is controlled at 28-33°SR.

[0023] Optionally, in step S2, the second pulping process specifically includes the following steps:

[0024] b1. Pulping the virgin softwood pulp and conveying it to a high-consistency cleaner;

[0025] b2. The slurry treated by the high-concentration cleaner is subjected to disc grinding in a disc grinding system to form a second slurry.

[0026] Optionally, the disc grinding system includes a primary disc grinding assembly and a secondary disc grinding assembly in sequence;

[0027] The primary refiner assembly includes two first wood pulp refiners connected in parallel, and the secondary refiner assembly includes two second wood pulp refiners connected in series.

[0028] Optionally, the second pulping process includes the following parameters:

[0029] The feed power of the disc grinding system is controlled at 500-700 kW, the beating concentration of the second slurry is controlled at 4-6%, and the beating degree of the second slurry is controlled at 20-25°SR.

[0030] Optionally, the retention and drainage aid is cationic polyacrylamide CPAM;

[0031] The sizing agent in the slurry is AKD emulsion with cationic charge, wherein the amount of AKD emulsion is controlled at 20-30 kg / t and the pH is controlled at 6-8;

[0032] The wet strength agent is a high-solid PAE type cationic wet strength agent, wherein the addition amount of the PAE type cationic wet strength agent is controlled at 8-15 kg / t.

[0033] Optionally, in step S4, the press section of the paper machine uses two consecutive shoe presses to press and dewater the wet paper web, wherein the pressure of the first shoe press is controlled at 600-800 kN, and the pressure of the second shoe press is controlled at 1000-1200 kN, and the dryness of the wet paper web after leaving the wire section of the paper machine is controlled at 20-23%, and the dryness of the wet paper web leaving the press section of the paper machine is controlled at 49-53%.

[0034] Optionally, in step S4, the step of applying sizing to the surface of the base paper by the sizing device of the paper machine specifically includes:

[0035] c1. Prepare a colloid for sizing by mixing starch, a surface sizing agent, a starch catalyst enhancer, and aluminum sulfate to prepare a colloid, wherein the surface sizing agent accounts for 15-20% of the starch, the starch catalyst enhancer accounts for 0.5-0.6% of the starch, and the aluminum sulfate accounts for 15-20% of the starch;

[0036] c2. Add the colloid into a sizing device, and the sizing device applies sizing to the surface of the base paper.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] In the production process of this embodiment, recycled pulp or 12 / 13# waste from US waste replaces approximately 40-50% of virgin wood pulp to produce high-performance wet-strength recycled kraft paper. This is more environmentally friendly and reduces production costs, while also significantly meeting market demand for product quality and performance. Furthermore, replacing most virgin wood pulp with waste paper not only conserves virgin materials, such as grass, trees, and forests, but also reduces environmental pollution. Compared to mechanical and chemical pulping, the production process of this embodiment achieves superior carbon reduction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 The present invention provides a flow chart of a production process for making high-performance, low-weight, wet-strength recycled kraft paper from secondary fibers. DETAILED DESCRIPTION

[0041] The present invention discloses a production process for high-performance, low-weight wet-strength recycled kraft paper made from secondary fibers, which is used to solve the technical problem that existing high-strength wet-strength paper is generally produced using 100% virgin wood pulp as raw material, resulting in high raw material costs and production energy consumption.

[0042] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0043] See also Figure 1 The embodiment of the present invention provides a production process for producing high-performance, low-weight, wet-strength recycled kraft paper from secondary fibers, comprising the following steps:

[0044] S1. Prepare raw materials, wherein the raw materials include 50%-60% of recycled pulp from US waste or US waste 12 / 13# and 40%-50% of virgin softwood pulp;

[0045] S2. Using recycled pulp from US waste or US waste 12 / 13# to prepare a first pulp, using virgin softwood pulp to prepare a second pulp through a preset second pulping process, and mixing the first pulp and the second pulp at a paper machine loading system to prepare papermaking pulp;

[0046] S3. Adding retention and drainage aids, internal sizing agents, and wet strength agents into the papermaking pulp;

[0047] S4. The papermaking pulp is transported to the paper machine through the paper machine feeding system. The wire section of the paper machine dehydrates and integrates the papermaking pulp to form a wet paper web. The press section of the paper machine presses and dehydrates the wet paper web. Subsequently, the front drying device of the paper machine dries the paper web to obtain base paper. The sizing device of the paper machine applies sizing to the surface of the base paper. Finally, the back drying device of the paper machine dries the base paper for a second time. The base paper is then calendered by the calendering device to obtain the finished kraft paper.

[0048] It should be noted that the recycled paddles from US waste or US waste 12 / 13# and virgin softwood pulp in this embodiment are raw materials that can be purchased on the market. The properties of the recycled paddles from US waste or US waste 12 / 13# and virgin softwood pulp are shown in the following table:

[0049]

[0050] In the production process of this embodiment, recycled pulp or 12 / 13# waste from US waste replaces approximately 40-50% of virgin wood pulp to produce high-performance wet-strength recycled kraft paper. This is more environmentally friendly and reduces production costs, while also significantly meeting market demand for product quality and performance. Furthermore, replacing most virgin wood pulp with waste paper not only conserves virgin materials, such as grass, trees, and forests, but also reduces environmental pollution. Compared to mechanical and chemical pulping, the production process of this embodiment achieves superior carbon reduction efficiency.

[0051] Furthermore, in this embodiment, between step S2 and step S1, the following steps are further included:

[0052] A mixture of 1.3% sodium hydroxide and 0.7% disodium hydrogen phosphate is added to the clean water in the treatment tank to form an alkaline solution. The pH value of the alkaline solution is controlled between 8-10 and the temperature of the alkaline solution is greater than 65°C.

[0053] Place the US waste recycled paddle board or US waste 12 / 13# into the treatment tank and soak it in alkali solution for a preset time.

[0054] It should be noted that, through the above design, the fibers in the American waste recycled paddle or American waste 12 / 13# can be fully stretched, the fiber separation and brooming effect can be improved, and pulping can be easier. Therefore, in the subsequent first pulping process, the disc grinding feed power can be lowered, thereby achieving lower energy consumption and improving the pulp bursting strength.

[0055] Furthermore, in step S2 of this embodiment, the first pulping process specifically includes the following steps:

[0056] a1. Pulp the recycled paddle or 12 / 13# waste from the US and transport it to the high-concentration cleaner;

[0057] a2. The pulp after being processed by the high-concentration cleaner is subjected to coarse screening and graded screening in sequence, and the graded screened pulp is transported to the low-concentration cleaner;

[0058] a3. The slurry treated by the low-concentration cleaner is finely screened and sent to a multi-disc thickener. After being treated by the multi-disc thickener, it is thermally dispersed and finally subjected to a disc grinding and beating process to form a first slurry.

[0059] It should be noted that in the first pulping process, a high-consistency cleaner and a low-consistency cleaner are used to remove heavy impurities in the pulp to avoid affecting the quality of the subsequent finished product;

[0060] In the pulping process described above, coarse screening is used to remove light residue and larger impurities, while fine screening is used to remove some stickies. The coarse screening is an outflow process, with the slurry passing through the screen under the power of the high-speed rotating rotor, while large plastic impurities are squeezed out of the barrel tail pipe. KADANT's UV500 series screen frames are used for coarse screening, combining perforated screens with slotted screens to ensure maximum slurry throughput while ensuring a reasonable average service life. KADANT's UV500 series screen frames are used for fine screening, with screen slots ranging from 0.15mm to 0.25mm, to separate the slurry into good quality pulp and long, medium, and short fibers.

[0061] Specifically, the first pulping process includes the following parameters:

[0062] The crushing concentration of the first slurry is controlled between 4-6%;

[0063] The pressure difference during the coarse screening process is controlled at 20-30kPa; the pressure difference during the graded screening process is controlled at 10-20kPa; the pressure difference during the fine screening process is controlled at 15-25kPa.

[0064] The pulp concentration of the multi-disc thickener is controlled at 0.5-0.8%, the pulp dryness out of the pressing screw is not less than 30%, and the torque is controlled between 30-50%;

[0065] The preheating temperature during the heat dispersion process is not lower than 95°C, and the back pressure is controlled at 150-180kPa;

[0066] The feed power during the disc grinding process is controlled at 600-800 kW, the beating concentration of the first pulp is controlled at 4-6%, and the beating degree of the first pulp is controlled at 28-33°SR.

[0067] Furthermore, in step S2 of this embodiment, the second pulping process specifically includes the following steps:

[0068] b1. Pulping the virgin softwood pulp and conveying it to a high-consistency cleaner;

[0069] b2. The slurry treated by the high-concentration cleaner is subjected to disc grinding in a disc grinding system to form a second slurry.

[0070] It should be noted that the virgin coniferous pulp adopts a multi-stage series disc grinding operation scheme with light beating, which controls the beating degree of the wood pulp to not exceed 25, ensures the fiber strength while allowing the fibers to be fully broomed and loosened, and ensures the tear strength of the paper through the wood pulp.

[0071] The specific disc grinding scheme is as follows: the disc grinding system used in the disc grinding includes a first-stage disc grinding assembly and a second-stage disc grinding assembly in sequence;

[0072] The primary refiner assembly includes two first wood pulp refiners connected in parallel, and the secondary refiner assembly includes two second wood pulp refiners connected in series.

[0073] It should be noted that the first-stage disc refiner assembly is the main stage of wood pulp beating. The two first wood pulp disc refiners are connected in parallel, and the disc refiner specific energy consumption is the same. The two second wood pulp disc refiners of the second-stage disc refiner assembly are connected in series for beating. The disc refiner specific energy consumption of one second wood pulp disc refiner is controlled at 60% of the disc refiner specific energy consumption of the first-stage disc refiner assembly, and the disc refiner specific energy consumption of the other second wood pulp disc refiner is controlled at 80% of the disc refiner specific energy consumption of the first-stage disc refiner assembly.

[0074] In addition, the use of the above-mentioned first-level disc grinding assembly and the second disc grinding assembly to achieve differentiated beating can improve the bursting strength while ensuring the tearing strength. In terms of paper strength effect, the bursting strength can be increased by about 40% and the breaking length can be increased by about 30%.

[0075] Specifically, the second pulping process in this embodiment includes the following parameters:

[0076] The feed power of the disc grinding system is controlled at 500-700 kW, the beating concentration of the second slurry is controlled at 4-6%, and the beating degree of the second slurry is controlled at 20-25°SR.

[0077] Furthermore, the retention and drainage aid in this embodiment is cationic polyacrylamide CPAM;

[0078] It should be noted that the above-mentioned cationic polyacrylamide CPAM can improve the retention of fine fibers of paper pulp and paper fillers on the wire, reduce the interference of paper fillers on the papermaking system, and improve the cleanliness of the white water system, making the papermaking system run more stably.

[0079] Furthermore, the internal sizing agent in this embodiment is AKD emulsion with cationic charge, wherein the amount of AKD emulsion is controlled at 20-30 kg / t and the pH is controlled at 6-8;

[0080] It should be noted that in the prior art, rosin size is generally added to the papermaking pulp to improve the water resistance and water retention of paper. Rosin size requires an acidic environment to achieve a good sizing effect. However, the disadvantage is that a continuous acidic environment will affect the charge balance of the wet-end system, affecting the effectiveness of other wet-end chemicals and hindering the system from maintaining good cleanliness.

[0081] In this embodiment, AKD emulsion with cationic charge is used for internal sizing. The dosage is controlled at 20-30 kg / t and the pH is controlled at about 6-8. The wet end system can be maintained in a moderately alkaline environment, providing good water and moisture resistance for the paper.

[0082] Furthermore, the wet strength agent in this embodiment is a high solid content (30%) PAE type cationic wet strength agent, wherein the addition amount of the PAE type cationic wet strength agent is controlled at 8-15 kg / t.

[0083] It should be noted that the additive is diluted 10-20 times with dilution water and added to the thick stock to fully retain the amino, epoxy, and azetidine groups. By reacting with the negatively charged pulp fibers, it limits fiber stretching. The addition amount is controlled at 8-15 kg / t. The main purpose of adding this additive is to ensure that the paper maintains a certain strength even when immersed in water, thereby improving the paper's wet strength.

[0084] Furthermore, in step S4 of this embodiment, the press section of the paper machine uses two consecutive shoe presses to press and dewater the wet paper web, wherein the pressure of the first shoe press is controlled at 600-800 kN, and the pressure of the second shoe press is controlled at 1000-1200 kN. The dryness of the wet paper web after leaving the wire section of the paper machine is controlled at 20-23%, and the dryness of the wet paper web leaving the press section of the paper machine is controlled at 49-53%.

[0085] It should be noted that the above design utilizes two consecutive shoe presses in the press section of the paper machine. This improves dewatering efficiency by increasing peak pressure and rapidly reducing pressure at the end of the nip, minimizing rewetting and improving dryness at the nip exit, thereby reducing dryer steam consumption. Furthermore, a profile steam box has been added to the first press position. By observing profile moisture deviations, single-point local adjustments can be made to reduce profile deviations and improve base paper uniformity.

[0086] Furthermore, in step S4 of this embodiment, the step of the sizing device of the paper machine applying sizing to the surface of the base paper specifically includes:

[0087] c1. Prepare a colloid for sizing by mixing starch, a surface sizing agent, a starch catalyst enhancer, and aluminum sulfate to prepare a colloid, wherein the surface sizing agent accounts for 15-20% of the starch, the starch catalyst enhancer accounts for 0.5-0.6% of the starch, and the aluminum sulfate accounts for 15-20% of the starch;

[0088] c2. Add the colloid into a sizing device, and the sizing device applies sizing to the surface of the base paper.

[0089] The purpose of the above-mentioned sizing treatment on the surface of the base paper is:

[0090] 1. Pre-finish the paper surface and improve the paper strength.

[0091] 2. Improve paper properties and further increase production efficiency. The surface sizing can retain almost 100% of the added chemicals.

[0092] 3. In terms of environmental friendliness, surface sizing has more advantages than wet-end additives. Surface sizing can reduce or eliminate chemicals in white water, which helps improve the environment.

[0093] It should be further explained that the sizing device used in this embodiment is specifically a film transfer sizing machine, which pre-treats the paper surface with glue. The starch in the glue forms a starch film that fills the surface pores of the paper sheet, reducing the pore size and thus reducing liquid penetration. This improves the paper's surface water resistance and printing performance, prevents linting and dusting, and effectively increases the strength and dimensional stability of the finished paper. Furthermore, to reduce starch consumption and improve surface film formation, the film transfer sizing machine uses a small-meter scraper combination to control the amount of glue applied to the surface layer to be approximately 20-30% less than that applied to the bottom layer, resulting in a more stable sizing state.

[0094] By replacing traditional amylase with starch catalytic enhancer, the hydrogen bonds in the starch molecular chain can be cut during cooking. Its free radicals are the same as those in starch and can quickly rearrange with starch to form grafted starch, thereby improving the slurry hanging property of starch slurry and the strength of finished paper.

[0095] In addition, the surface sizing agent addition rate is controlled at 40-60 L / h, the bottom surface sizing agent addition rate is controlled at 60-80 L / h, and the surface sizing agent addition rate is controlled at 3-5 L / min. The purpose of addition is: a) to improve the water absorption properties of the finished paper, prevent water penetration, and improve the dimensional stability of the paper; b) to optimize the paper machine system environment and reduce the interference of anionic waste on the papermaking environment; c) to promote the sizing effect of the sizing agent and improve the surface film formation of the film transfer sizing.

[0096] Furthermore, in step S4 of this embodiment, after obtaining the finished kraft paper, a film coating machine is used to coat the finished paper, thereby reducing the influence of the external environment on the paper and extending the storage time of the finished paper.

[0097] Furthermore, the performance parameters of the kraft paper produced by the above-mentioned production process of high-performance low-weight wet-strength recycled kraft paper using secondary fibers are as follows:

[0098]

[0099] Note: The wet burst test refers to the test under specified test conditions. After the sample is immersed in water for 1 hour, uniform pressure is applied perpendicular to the surface of the sample to test the maximum resistance until the sample breaks.

[0100] In summary, the kraft paper produced by the production process of secondary fiber papermaking high-performance low-weight wet-strength recycled kraft paper has the following advantages:

[0101] 1. In terms of raw material structure, high-performance, low-weight wet-strength recycled kraft paper is made from recycled paddle board or 12 / 13# recycled paper as the main raw materials, which greatly reduces the raw material cost while meeting the quality requirements.

[0102] 2. Using waste paper raw materials to replace most virgin wood pulp can not only save virgin materials (grass, forests, etc.), but also reduce pollution to the environment. Compared with mechanical pulp and chemical pulp, waste paper pulp production has better carbon reduction efficiency.

[0103] 3. In the beating process, we use recycled paddles from US waste or US waste 12 / 13# and virgin softwood pulp for differentiated beating to reduce mechanical damage to the fiber while allowing the fiber to separate and become brooms;

[0104] 4. The disc mill adopts the light beating method of virgin softwood pulp, which makes the virgin wood pulp slightly cut, retaining the fiber length and strength while also greatly saving electricity consumption.

[0105] 5. In the sizing process, AKD in-pulp sizing is adopted to maintain a long-term neutral alkaline environment in the wet end, making other chemicals in the wet end more adaptable and reducing the effects of functional additives (such as wet strength agents) and process additives (such as retention agents) attenuation; at the same time, heavy sizing is adopted to greatly improve the water resistance and anti-penetration properties of the paper.

[0106] 6. In the pressing process, two continuous shoe presses and a horizontal steam box are used to improve dehydration efficiency and horizontal uniformity, improve the dryness of the press area, and thus reduce dry steam consumption.

[0107] 7. In terms of wet strength retention, a high-solid content PAE wet strength agent is selected, which can be adjusted to any proportion through the dilution water system to achieve the wet strength retention effect required by the customer;

[0108] 8. When the paper is packaged off-line, a film wrapping machine is used to wrap the paper, which reduces the impact of the external environment on the paper and extends the storage time of the finished paper.

[0109] The production process of this embodiment utilizes innovative raw material ratios, optimized pulping, chemical processing, and sizing process control to produce high-performance wet-strength recycled kraft paper using recycled pulp or recycled 12 / 13# from US waste to replace approximately 40-50% of virgin wood pulp. This is more environmentally friendly and reduces production costs, while also significantly meeting market demand for product quality and performance. Furthermore, replacing most virgin wood pulp with waste paper not only conserves virgin materials, such as grass, trees, and forests, but also reduces environmental pollution. Compared to mechanical and chemical pulping, the production process of this embodiment achieves superior carbon reduction efficiency.

[0110] The above is a detailed introduction to the production process of high-performance, low-weight, wet-strength recycled kraft paper made from secondary fibers provided by the present invention. For those skilled in the art, according to the ideas of the embodiments of the present invention, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation of the present invention.

Claims

1. A production process for producing high-performance, low-weight, wet-strength recycled kraft paper from secondary fibers, characterized in that: The following steps are involved: S1. Prepare raw materials, wherein the raw materials include 50%-60% of recycled pulp from US waste or US waste 12 / 13# and 40%-50% of virgin softwood pulp; S2. Using recycled pulp from US waste or US waste 12 / 13# to prepare a first pulp, using virgin softwood pulp to prepare a second pulp through a preset second pulping process, and mixing the first pulp and the second pulp at a paper machine loading system to prepare papermaking pulp; S3. Adding retention and drainage aids, internal sizing agents, and wet strength agents into the papermaking pulp; S4. The papermaking pulp is conveyed to the paper machine through the paper machine feeding system. The wire section of the paper machine dehydrates and consolidates the papermaking pulp to form a wet paper web. The press section of the paper machine presses and dehydrates the wet paper web. Subsequently, the pre-drying device of the paper machine dries the paper web to obtain base paper. The sizing device of the paper machine applies sizing to the surface of the base paper. Finally, the post-drying device of the paper machine dries the base paper for a second time. The base paper is then calendered by the calendering device to obtain the finished kraft paper. The steps between step S1 and step S2 also include: A solvent consisting of 1.3% sodium hydroxide and 0.7% disodium hydrogen phosphate is added to the clean water in the treatment tank to form an alkaline solution. The pH value of the alkaline solution is controlled between 8 and 10, and the temperature of the alkaline solution is greater than 65°C. Place the recycled paddle board or recycled paddle board 12 / 13# into the treatment tank and soak it in alkali solution for a preset time; The retention and drainage aid is cationic polyacrylamide CPAM; The sizing agent in the slurry is AKD emulsion with cationic charge, wherein the amount of AKD emulsion is controlled at 20-30 kg / t and the pH is controlled at 6-8; The wet strength agent is a high solid content PAE type cationic wet strength agent, wherein the addition amount of the PAE type cationic wet strength agent is controlled at 8-15 kg / t; In step S4, the step of applying sizing to the surface of the base paper by the sizing device of the paper machine specifically includes: c1. Prepare a colloid for sizing by mixing starch, a surface sizing agent, a starch catalyst enhancer, and aluminum sulfate to prepare a colloid, wherein the surface sizing agent accounts for 15-20% of the starch, the starch catalyst enhancer accounts for 0.5-0.6% of the starch, and the aluminum sulfate accounts for 15-20% of the starch; c2. adding the colloid into a sizing device, and applying sizing to the surface of the base paper; Among them, the amount of glue on the surface layer of the base paper is 20-30% less than that on the bottom layer.

2. The production process of secondary fiber papermaking high-performance low-weight wet-strength recycled kraft paper according to claim 1, characterized in that: In step S2, the first pulping process specifically includes the following steps: a1, pulping the American waste regenerated paddle or American waste 12 / 13# and transporting it to a high-consistency cleaner; a2. The pulp after being processed by the high-concentration cleaner is subjected to coarse screening and graded screening in sequence, and the graded screened pulp is transported to the low-concentration cleaner; a3. The slurry treated by the low-concentration cleaner is finely screened and sent to a multi-disc thickener. After being treated by the multi-disc thickener, it is thermally dispersed and finally subjected to a disc grinding and beating process to form a first slurry.

3. The production process of secondary fiber papermaking high-performance low-weight wet-strength recycled kraft paper according to claim 2, characterized in that: The first pulping process includes the following parameters: The crushing concentration of the first slurry is controlled between 4-6%; The pressure difference during the coarse screening process is controlled at 20-30kPa; the pressure difference during the graded screening process is controlled at 10-20kPa; the pressure difference during the fine screening process is controlled at 15-25kPa; The pulp concentration of the multi-disc thickener is controlled at 0.5-0.8%, the pulp dryness out of the pressing screw is not less than 30%, and the torque is controlled between 30-50%; The preheating temperature during the heat dispersion process is not lower than 95°C, and the back pressure is controlled at 150-180kPa; The feed power during the disc grinding process is controlled at 600-800kW, the pulping concentration of the first pulp is controlled at 4-6%, and the beating degree of the first pulp is controlled at 28-33°SR.

4. The production process of secondary fiber papermaking high-performance low-basis-weight wet-strength recycled kraft paper according to claim 1, characterized in that: In step S2, the second pulping process specifically includes the following steps: b1. Pulping the virgin softwood pulp and conveying it to a high-consistency cleaner; b2. The slurry treated by the high-concentration cleaner is subjected to disc grinding in a disc grinding system to form a second slurry.

5. The production process of secondary fiber papermaking high-performance low-basis-weight wet-strength recycled kraft paper according to claim 4, characterized in that: The disc grinding system comprises a primary disc grinding assembly and a secondary disc grinding assembly in sequence; The primary refiner assembly includes two first wood pulp refiners connected in parallel, and the secondary refiner assembly includes two second wood pulp refiners connected in series.

6. The production process of secondary fiber papermaking high-performance low-basis-weight wet-strength recycled kraft paper according to claim 4, characterized in that: The second pulping process includes the following parameters: The feed power of the disc grinding system is controlled at 500-700kW, the beating concentration of the second pulp is controlled at 4-6%, and the beating degree of the second pulp is controlled at 20-25°SR.

7. The production process of secondary fiber papermaking high-performance low-basis-weight wet-strength recycled kraft paper according to claim 1, characterized in that: In step S4, the press section of the paper machine uses two consecutive shoe presses to press and dewater the wet paper web, wherein the pressure of the first shoe press is controlled at 600-800 kN, and the pressure of the second shoe press is controlled at 1000-1200 kN. The dryness of the wet paper web after leaving the wire section of the paper machine is controlled at 20-23%, and the dryness of the wet paper web before leaving the press section of the paper machine is controlled at 49-53%.

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