Production process of high-folding-resistance corrugated base paper

Abstract

The invention discloses a production process of high-folding-resistance corrugated base paper, and particularly relates to the technical field of corrugated paper production. The process comprises the following steps: mixing and hydraulically pulping different types of waste paper raw materials to obtain original waste paper pulp with the concentration of 2.5-2.8%; original waste paper pulp enters a classifying screen after being subjected to high-concentration sand removal, coarse screening and low-concentration sand removal, and fibers in the waste paper pulp are screened into long fibers and short fibers; mixing the long fiber pulp and the short fiber pulp in proportion, and carrying out papermaking and surface sizing treatment; wherein the papermaking comprises the steps of forming a net part, squeezing and dehydrating, and drying in a pre-drying part to obtain initial corrugating base paper with the dryness of 90-92%, then carrying out surface sizing treatment on the initial corrugating base paper by using a boiled glue solution, drying at 60-100 DEG C until the dryness is 85-92%, and curling and slitting to obtain the high-folding-resistance corrugating base paper. Stable production of the high-folding-resistance corrugated base paper is achieved through raw material diversification, fiber refining treatment, papermaking process flexible regulation and control and glue solution accurate preparation.

Description

Technical Field

[0001] The invention relates to the technical field of corrugated paper production, and in particular to a production process of highly folding-resistant corrugated base paper. Background Art

[0002] Waste paper, also known as secondary fiber, is used as a raw material for papermaking. The paper industry's extensive recycling of waste paper not only reduces waste generation and potential environmental harm, but also generates economic benefits through the recycling of waste paper resources, protecting the ecological environment and conserving resources at the source.

[0003] Corrugated boxes are made of corrugated cardboard. Because of their multi-layer structure and good strength, they are widely used in packaging and transportation, especially in the transportation of heavy goods. During the loading process of goods, the corrugated paper needs to be folded multiple times to form a specific shape. Due to the low strength of existing corrugated paper, the corrugated paper is easily broken or damaged during the folding process, and thus cannot be reused.

[0004] Chinese patent CN111021130A uses waste paper and further processes it through pulping, papermaking, and slag removal to ultimately produce corrugated paper. However, the corrugated paper produced in this patent has poor folding resistance and cannot be considered as high-folding-resistance corrugated base paper, so it lacks competitiveness. Therefore, how to improve the folding resistance of corrugated paper is a difficult problem that needs to be solved urgently.

[0005] Although some existing patents and technologies have improved the folding resistance of corrugated paper to a certain extent, these are mainly achieved by adding a large amount of cellulose or cellulose-like components to the original paper pulp. For example, Chinese patent CN114808522A adds a large amount of cellulose nanocrystals, which are firmly combined with the active groups on dopamine through covalent bonds to form a cellulose nanocrystal network porous structure to increase the folding resistance of corrugated paper; Chinese patent CN115262283A uses plant fiber pulp as raw material, and adds resin, modified nano-silica, etc., and adds different raw materials and additives in different layers to achieve the requirement of increasing the folding resistance of corrugated paper. However, these patents require the addition of a large amount of other additives, the process is complicated, the production cost is high, and these patents cannot be directly prepared using waste paper, and the waste paper recycling rate is low. Summary of the Invention

[0006] To this end, the present invention provides a production process for high-folding-resistance corrugated paper to solve the problems in the prior art.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] According to the present invention, a production process for high-folding-resistance corrugated paper is provided, the process comprising:

[0009] Step 1: Mix different types of waste paper raw materials and hydraulically pulp them to obtain raw waste paper pulp with a concentration of 2.5-2.8%;

[0010] Step 2: After high-concentration sand removal, coarse screening, and low-concentration sand removal, the original waste paper pulp enters a grading screen to separate the fibers in the waste paper pulp into long fibers and short fibers. The long fiber segment includes fine screening and long fiber concentration. The fine screening adopts a duplex fiber fine screening. 0.2-0.3% cellulase is added during the fine screening process. After concentration, the concentration of the long fibers is 8-10%. After concentration, a wet strength agent is added to obtain long fiber pulp. The short fiber segment includes short fiber concentration. After concentration, the concentration is 6-8%. After concentration, 0.3-0.5% fiber reinforcement is added to obtain short fiber pulp.

[0011] Step three, mixing the long fiber pulp and the short fiber pulp in proportion, and carrying out papermaking and surface sizing treatment; wherein, papermaking includes mesh forming, pressing and dehydration, and drying in the front drying section to obtain an initial corrugated base paper with a dryness of 90-92%, and then the boiled glue liquid is used to apply sizing treatment to the surface of the initial corrugated base paper, and dried at 60-100 ° C to a dryness of 85-92%, and curled and cut to obtain high-folding-resistant corrugated base paper.

[0012] Furthermore, in step 1, the waste paper raw materials include the following weight percentages: 35-40% of special grade waste paper, 24-28% of cardboard from pit card factory, 4-8% of mixed shopping mall waste paper, 8-12% of dry pulp bag, and 18-22% of industrial carton waste paper.

[0013] The present invention controls the concentration of original waste paper pulp and reduces collision and shearing between fibers.

[0014] Furthermore, 0.5-1% fiber protectant is added to the hydraulic pulping, for example, polyvinyl alcohol (PVA) is preferred, which wraps the fiber surface during pulping to reduce friction damage; 0.1-0.3% NaOH is added to adjust the pH to 8.5-9.0, soften the fiber surface and reduce excessive hydrogen bonding between fibers (to avoid difficulty in separating fibers during subsequent pulping).

[0015] Furthermore, the parameters of hydraulic pulping are to control the pulping time to 15-20 minutes and the rotation speed to 3000-3500 rpm; the beating degree is 30-45°SR to avoid excessive dissociation leading to short fibers. Excessive beating will reduce the flexibility and elasticity of the fibers and affect the folding resistance.

[0016] Furthermore, in step 2, the composite fiber screening includes a pressure screen and a centrifugal screen. For example, the pressure screen preferably has a sieve opening of 0.18-0.22 mm and the centrifugal screen rotates at 1500-1800 rpm to remove fiber bundles and foreign cells while retaining intact long fibers. Preferably, the cellulase is an endoglucanase, which mildly hydrolyzes the fiber surface, promotes hydrogen bonding, and enhances interfiber bonding.

[0017] Furthermore, in the step 2, the wet strength agent is PAE resin, and the addition amount is 0.5-1%, which forms a cross-linked network on the fiber surface to enhance the folding resistance.

[0018] As an example, a drum vacuum concentrator is preferred for long fiber concentration to control the shear force during the concentration process (the linear speed is 12-15 m / min) to avoid excessive compression and damage to the fibers.

[0019] Furthermore, the short fiber concentration is preferably performed using a plate-and-frame concentrator, and the fiber reinforcement is preferably a starch derivative, so as to fill the gaps between the short fibers and improve the density of the paper structure.

[0020] Furthermore, in step three, the ratio of long fibers to short fibers is 6:4-8:2; the long fibers account for 60% to 80% to provide skeletal support, while the short fibers account for 20% to 40% to fill gaps and improve uniformity and surface smoothness. Generally, long fibers are those greater than 1.8 mm, while short fibers are those less than or equal to 1.8 mm. In this invention, long fibers greater than 2.2 mm refer to fibers greater than 2.2 mm accounting for at least 90% of the total fiber count.

[0021] Web Forming: Optimizes fiber orientation and distribution. Low-vacuum dehydration: A vacuum of -25-30 kPa is maintained from the breast roll to the vacuum couch roll, extending fiber residence time on the web (0.8-1.0 seconds) and promoting lateral fiber dispersion (reducing stress concentration during folding caused by longitudinal orientation). Polyester Web Selection: Utilize an 80-100 mesh / inch Fourdrinier wire (finer than the traditional 60 mesh) to minimize fiber loss and improve wet paper smoothness (reducing fiber deformation during subsequent pressing).

[0022] Pressing dehydration: Balances dryness and fiber bonding. Pressing pressure gradient control: Using a three-roll press (with increasing diameters), the linear pressure gradually increases from 90 kN / m on the first roller to 300 kN / m on the third roller to avoid fiber breakage caused by a single high pressure (increasing dryness from 30% to 45-50%). Temperature-assisted dehydration: 60-70°C steam is introduced into the press roller surface to soften the fiber surface (reducing the binding resistance of free water between fibers) and improve dehydration efficiency (reducing the amount of chemical additives used).

[0023] Pre-drying: Controls moisture and internal stress. Segmented drying curve: The pre-drying section utilizes a "low-temperature, slow-drying" mode (80-90°C for the first set of drying cylinders, 90-100°C for the second set), increasing the dryness from 45-50% to 90-92% (rather than directly exceeding 90%), thus avoiding the accumulation of internal stress (increased brittleness) caused by rapid drying. Tension control: A longitudinal tension of 0.1-0.2 N / m is applied during the drying process (adjusted by speed between transmission groups) to suppress paper shrinkage (reducing elastic recovery stress during folding).

[0024] Furthermore, the glue solution contains starch glue solution with a concentration of 10-14% and a viscosity of 20-30 MPa.s, 100-150 g of amylase per ton of paper, and 3-4 kg of styrene acrylic sizing agent per ton of paper.

[0025] Furthermore, the glue solution is prepared by precisely controlling starch gelatinization and enzymatic hydrolysis through segmented heating, vacuum degassing and static ripening.

[0026] As an example, it is preferred that:

[0027] 1. Low-temperature pre-dissolution (40-50°C, 15-20 minutes): Slowly add starch to deionized water (solid-liquid ratio 1:8), start low-speed stirring (100 rpm), and heat to 40-50°C to obtain a starch mixture; dilute the styrene acrylic sizing agent (3-4 kg / ton) with deionized water in advance (solid-liquid ratio 1:5) to form a uniform styrene acrylic sizing agent emulsion;

[0028] 2. Enzymatic hydrolysis and temperature-controlled gelatinization (55-65°C, 30-40 minutes): Add amylase and acrylic sizing agent emulsion to the starch mixture, increase the stirring speed to 200 rpm, slowly raise the temperature to 55-65°C, and perform enzymatic hydrolysis and mixing;

[0029] 3. High temperature aging (65-75℃, 15-20 minutes): Continue to heat up to 85-90℃ (starch complete gelatinization temperature), maintain for 15-20 minutes, keep warm to allow the starch to completely moisten and gelatinize. After cooking, transfer the glue solution to a vacuum degassing tank and keep it at -0.08~-0.09MPa for 10 minutes for vacuum degassing to avoid residual bubbles during sizing and causing surface defects of the paper. The degassed glue solution is placed in a sealed container for 2 hours with continuous stirring (low speed, 50rpm) to obtain a glue solution with a viscosity of 20-30mPa.s.

[0030] The drying method after gluing is low-temperature segmented drying: after gluing, the paper enters the drying section, the temperature of the first group of drying cylinders is 60-70℃ (low-temperature slow drying), the second group is 80-90℃ (medium-temperature curing), and the third group is ≤100℃ (high-temperature setting). The final dryness is controlled at 85-92% (retaining some moisture).

[0031] The present invention has the following advantages:

[0032] The present invention uses different types of waste paper for mixing, covering the main types of packaging waste paper. Compared with the traditional process that relies only on a single waste paper (such as OCC) or requires additional external waste, the present invention fully utilizes the domestic recycled waste paper resources through a multi-waste paper ratio. The present invention adds a dry pulp bag, which is rich in long fibers (such as unbleached chemical pulp fibers), which can make up for the problem of short and broken fibers caused by multiple recycling of other waste papers (such as industrial carton waste paper and paper edge waste paper), improve the overall fiber length and strength of the raw material, and provide a high-quality foundation for the subsequent preparation of long fiber pulp.

[0033] During hydraulic pulping, the present invention adds 0.5-1% polyvinyl alcohol (PVA) as a fiber protectant to coat the fiber surface and reduce friction damage. Simultaneously, 0.1-0.3% NaOH is added to adjust the pH to 8.5-9.0, softening the fiber surface and reducing excessive hydrogen bonding. These measures effectively reduce fiber breakage during the pulping process, preserving more of the original fiber's length and softness, laying the foundation for high folding resistance.

[0034] The present invention treats long and short fibers differently. The long fibers are passed through a pressure screen + a centrifugal screen to ensure high purity of the long fibers. Different stabilizers are added to the long / short fiber pulps after pulping. Through the special long / short fiber ratio adjustment, the tensile strength and folding resistance of the paper are significantly improved.

[0035] The glue solution of the invention does not need to add complex auxiliary agents such as cellulose nanocrystals and modified nano-silicon dioxide, and has a simple process and a high waste paper utilization rate.

[0036] The present invention controls the boiling of the glue solution in a refined manner, so that the viscosity of the glue solution is moderate and more suitable for high-folding-resistant corrugated paper.

[0037] The present invention achieves stable production of highly fold-resistant corrugated paper through raw material diversification (dry pulping bags to supplement long fibers), fiber refinement (enzymatic hydrolysis + wet strength agent / reinforcement agent), flexible regulation of papermaking process (low shear + low-temperature drying) and precise preparation of glue (segmented boiling + vacuum degassing). DETAILED DESCRIPTION

[0038] The following describes the implementation of the present invention using specific embodiments. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. Obviously, the embodiments described are only a portion of the present invention, not all of it. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0039] Special-grade waste paper: It is divided into special-grade waste paper boxes (X0) and special-grade mixed waste paper (HH0). Special-grade waste paper boxes (X0) are composite packaging cartons made entirely of virgin wood pulp, with each layer having essentially uniform color without noticeable color differences, and no recycled pulp or other pulp components. Special-grade mixed waste paper (HH0) primarily consists of unbound, unlaminated, and unprinted white paper trimmings from printing factories, unprinted white office waste paper, and pure white offset paper.

[0040] Corrugated cardboard generally refers to corrugated cardboard, while factory cardboard typically refers to scraps or waste generated during the carton factory production process. Corrugated cardboard is primarily made up of corrugated cardboard scraps and waste cartons. It is typically yellowish in color and contains a certain proportion of recycled fiber.

[0041] Mixed shopping mall waste paper: mainly waste paper generated in shopping malls, supermarkets and other places. It has a relatively complex composition and may include various wrapping papers, brochures, label papers, etc., and usually contains certain colored paper and coated paper.

[0042] Dry pulp bales are bales of waste pulp produced during the papermaking process, which are dried and processed. They are primarily composed of pulp fibers and are generally relatively pure, but may contain small amounts of additives or residues. Shenzhen Dacheng New Energy Technology Co., Ltd. imports dry pulp bales from Vietnam.

[0043] Industrial carton waste paper: mainly comes from packaging cartons in the industrial production process, usually kraft cartons, with high strength and good fiber quality, and is generally brown or light yellow in color.

[0044] Polyvinyl alcohol PVA: CAS 9002-89-5;

[0045] Endoglucanase: CAS 9012-54-8;

[0046] PAE resin: CB92126242;

[0047] Amylase: CAS 9001-11-0;

[0048] Styrene acrylic sizing agent: Tops New Materials Co., Ltd. Model: TOP-760;

[0049] Starch: CAS 9005-25-8;

[0050] Fiber reinforcement: B.BRAUN, hydroxyethyl starch, product number L6511.

[0051] Example 1

[0052] This embodiment provides a production process for high-folding-resistance corrugated paper:

[0053] Waste paper raw materials: 38% of premium waste paper, 26% of cardboard from pit card factories, 6% of mixed shopping mall waste paper, 10% of dry pulp bags, and 20% of industrial carton waste paper;

[0054] Process:

[0055] Step 1: After mixing and hydraulically pulping different types of waste paper raw materials, 0.5% polyvinyl alcohol (PVA) is added, and the pH is adjusted to 8.5 using NaOH solution to obtain raw waste paper pulp with a concentration of 2.5%;

[0056] The parameters of hydraulic pulping are to control the pulping time to 15-20 minutes and the rotation speed to 3000-3500 rpm; the beating degree is 30-45°SR;

[0057] Step 2: After high-concentration sand removal, coarse screening and low-concentration sand removal, the original waste paper pulp enters the grading screen to screen the fibers in the waste paper pulp into long fibers and short fibers; wherein, the long fiber segment includes fine screening and long fiber concentration, and the fine screening adopts a duplex fiber fine screen (pressure screen + centrifugal screen), the pressure screen gap is 0.22mm, and the centrifugal screen speed is 1800rpm to remove fiber bundles and miscellaneous cells and retain complete long fibers; 0.2% cellulase is added during the fine screening process, and the concentration of long fibers after concentration is 8%. After concentration, 1% wet strength agent PAE resin is added to obtain long fiber pulp; the short fiber segment includes short fiber concentration, and the concentration after concentration is 6%. After concentration, 0.3% fiber reinforcement is added to obtain short fiber pulp; wherein, the long fibers are larger than 2.2mm and the short fibers are smaller than 1.8mm.

[0058] Drum vacuum concentrator is preferred for long fiber concentration, while plate and frame concentrator is preferred for short fiber concentration;

[0059] Step three, mixing the long fibers and the short fibers in a ratio of 8:2, and carrying out papermaking and surface sizing treatment; wherein, papermaking includes mesh forming, pressing and dehydration, and drying in the front drying section to obtain an initial corrugated base paper with a dryness of 90-92%, and then the boiled glue (containing 12% concentration, 25mPa.s viscosity starch glue and 120g amylase per ton of paper and 3kg styrene acrylic sizing agent per ton of paper) is used to carry out surface sizing treatment on the initial corrugated base paper, and dried at 60-100°C to a dryness of 85-92%, and curled and cut to obtain high folding-resistant corrugated base paper.

[0060] Net forming: The vacuum degree from the breast roll to the vacuum roller is -60kPa, and the residence time of the fiber on the net is prolonged (1.0 second). Polyester net selection: 80 mesh / inch Fourdrinier net is used.

[0061] Pressing pressure gradient control: Using a three-roll press (with increasing diameters), the linear pressure gradually increases from 90kN / m on the first roll to 300kN / m on the third roll to avoid fiber breakage caused by a single high pressure (increasing dryness from 30% to 45-50%). Temperature-assisted dehydration: 60-70°C hot water (or steam) is passed through the press roll surface to soften the fiber surface (reducing inter-fiber bonding resistance) and improve dehydration efficiency (reducing the amount of chemical additives used).

[0062] Pre-drying segmented drying curve: The pre-drying section adopts the "low temperature slow drying" mode (the first group of drying cylinders is 80-90℃, the second group is 90-100℃), which increases the dryness from 45-50% to 90-92% (rather than directly >90%), avoiding the accumulation of internal stress caused by rapid drying (increased paper brittleness).

[0063] Tension control: Apply a longitudinal tension of 0.1N / m during the drying process.

[0064] Boil glue:

[0065] 1. Low-temperature pre-dissolution (40-50°C, 15-20 minutes): Slowly add starch to deionized water (solid-liquid ratio 1:8), start low-speed stirring (100 rpm), and heat to 40-50°C to obtain a starch mixture; dilute the styrene acrylic sizing agent (3-4 kg / ton) with deionized water in advance (solid-liquid ratio 1:5) to form a uniform styrene acrylic sizing agent emulsion;

[0066] 2. Enzymatic hydrolysis and temperature-controlled gelatinization (55-65°C, 30-40 minutes): Add amylase and acrylic sizing agent emulsion to the starch mixture, increase the stirring speed to 200 rpm, slowly raise the temperature to 55-65°C, and perform enzymatic hydrolysis and mixing;

[0067] 3. High temperature aging (85-90℃, 15-20 minutes): Continue to heat up to 85-90℃ (starch complete gelatinization temperature) and maintain for 15-20 minutes. After the cooking is completed, transfer the glue liquid to a vacuum degassing tank and maintain it at -0.08~-0.09MPa for 10 minutes for vacuum degassing to avoid residual bubbles during sizing and causing surface defects of the paper. The degassed glue liquid is placed in a sealed container for 2 hours, during which it is stirred for 5 minutes every 30 minutes (low speed, 50rpm) to obtain a glue liquid with a viscosity of 20-30mPa.s.

[0068] The drying method after gluing is staged drying: after gluing, the paper enters the drying section, the temperature of the first group of drying cylinders is 60-70℃ (low temperature slow drying), the second group is 80-90℃ (medium temperature curing), and the third group is ≤100℃ (high temperature setting). The final dryness is controlled at 85-92% (retaining some moisture).

[0069] All the slag discharges involved in the present invention do not have any innovative points and will not be limited or described one by one.

[0070] Example 2

[0071] This embodiment provides a production process for high-folding-resistance corrugated paper:

[0072] Waste paper raw materials: special grade waste paper 35%, cardboard from pit card factory 28%, mixed shopping mall waste paper 6%, dry pulp bales 12%, industrial carton waste paper 19%;

[0073] Process:

[0074] In step 1, different types of waste paper raw materials are mixed and hydraulically pulped, 1% polyvinyl alcohol (PVA) is added, and the pH is adjusted to 9 using a NaOH solution to obtain raw waste paper pulp with a concentration of 2.8%.

[0075] Step 2: After high-concentration sand removal, coarse screening and low-concentration sand removal, the original waste paper pulp enters the grading screen to screen the fibers in the waste paper pulp into long fibers and short fibers; wherein, the long fiber segment includes fine screening and long fiber concentration, and the fine screening adopts a duplex fiber fine screening (pressure screen + centrifugal screen), the pressure screen gap is 0.18mm, and the centrifugal screen speed is 1500rpm, to remove fiber bundles and miscellaneous cells, retain complete long fibers, and the purity of the long fibers is 90% (the test process has tried a separate fine screening method, and the highest long fiber purity is only 70%, which does not meet expectations); 0.3% cellulase is added during the fine screening process, and the concentration of the long fibers after concentration is 10%. After concentration, 1% wet strength agent PAE resin is added to obtain long fiber pulp; the short fiber segment includes short fiber concentration, and the concentration after concentration is 8%. After concentration, 0.5% fiber reinforcement is added to obtain short fiber pulp; wherein, the long fibers are larger than 2.2mm and the short fibers are smaller than 1.8mm.

[0076] Step three, mixing the long fiber and the short fiber in a ratio of 6:4, and carrying out papermaking and surface sizing treatment; wherein, papermaking includes mesh forming, pressing and dehydration, and drying in the front drying section to obtain an initial corrugated base paper with a dryness of 90-92%, and then the boiled glue (containing 10% concentration, 20mPa.s viscosity starch glue and 100g amylase per ton of paper and 4kg styrene acrylic sizing agent per ton of paper) is used to carry out surface sizing treatment on the initial corrugated base paper, and dried at 60-100°C to a dryness of 85-92%, and curled and cut to obtain high folding-resistant corrugated base paper.

[0077] Other parameters are exactly the same as those in Example 1.

[0078] Example 3

[0079] This embodiment provides a production process for high-folding-resistance corrugated paper:

[0080] Waste paper raw materials: special grade waste paper 35%, cardboard from pit card factory 28%, mixed shopping mall waste paper 6%, dry pulp bales 12%, industrial carton waste paper 19%;

[0081] Process:

[0082] Step 1: After mixing and hydraulically pulping different types of waste paper raw materials, 0.5% polyvinyl alcohol (PVA) is added, and the pH is adjusted to 8.5 using NaOH solution to obtain raw waste paper pulp with a concentration of 2.5%;

[0083] Step 2: After high-concentration sand removal, coarse screening and low-concentration sand removal, the original waste paper pulp enters the grading screen to screen the fibers in the waste paper pulp into long fibers and short fibers; wherein, the long fiber segment includes fine screening and long fiber concentration, and the fine screening adopts a duplex fiber fine screen (pressure screen + centrifugal screen), the pressure screen gap is 0.22mm, and the centrifugal screen speed is 1800rpm to remove fiber bundles and miscellaneous cells and retain complete long fibers; 0.2% cellulase is added during the fine screening process, and the concentration of long fibers after concentration is 8%. After concentration, 1% wet strength agent PAE resin is added to obtain long fiber pulp; the short fiber segment includes short fiber concentration, and the concentration after concentration is 6%. After concentration, 0.3% fiber reinforcement is added to obtain short fiber pulp; wherein, the long fibers are larger than 2.2mm and the short fibers are smaller than 1.8mm.

[0084] Step 3: Mix the long fibers and short fibers in a ratio of 7:3, and perform papermaking and surface sizing treatment; wherein the papermaking includes forming in a mesh section, squeezing and dehydrating, and drying in a pre-drying section to obtain an initial corrugated base paper with a dryness of 90-92%. Then, the initial corrugated base paper is surface sizing treated with a boiled glue solution (comprising a starch glue solution with a concentration of 12% and a viscosity of 25 MPa.s, 120 g of amylase per ton of paper, and 3 kg of styrene acrylic sizing agent per ton of paper), and then dried at 60-100° C. to a dryness of 85-92%, and then curled and slit to obtain a high-folding-resistant corrugated base paper. Other parameters are exactly the same as in Example 1.

[0085] Comparative Example 1

[0086] This comparative example provides a production process for high-folding-resistance corrugated paper:

[0087] Waste paper raw materials: 48% special grade waste paper, 26% cardboard from waste paper factories, 6% mixed shopping mall waste paper, 20% industrial carton waste paper; among them, long fibers are larger than 1.9mm, 1.9-2.0mm accounts for more than 90%, and short fibers are less than 1.8mm.

[0088] Other details are exactly the same as in Example 1.

[0089] Comparative Example 2

[0090] This comparative example provides a production process for high-folding-resistance corrugated paper:

[0091] Waste paper raw material: same as in Example 1.

[0092] In this comparative example, during the hydraulic pulping process, no fiber protective agent and no NaOH were added to adjust the pH. Other aspects were completely consistent with those of Example 1.

[0093] Comparative Example 3

[0094] This comparative example provides a production process for high-folding-resistance corrugated paper:

[0095] Waste paper raw material: same as in Example 1.

[0096] In the treatment of long and short fibers in this comparative example: no cellulase and wet strength agent were added in the treatment of long fibers; no fiber reinforcement was added to the short fibers; and the rest was completely consistent with Example 1.

[0097] Comparative Example 4

[0098] This comparative example provides a production process for high-folding-resistance corrugated paper:

[0099] Waste paper raw material: same as in Example 1.

[0100] The ratio of long fiber to short fiber in this comparative example is 5:5, and the others are completely consistent with those in Example 1.

[0101] Comparative Example 5

[0102] This comparative example provides a production process for high-folding-resistance corrugated paper:

[0103] Waste paper raw material: same as in Example 1.

[0104] The method of boiling the glue solution is: after mixing starch with water, add amylase and heat to 65°C for enzymolysis, mix it with the styrene acrylic sizing agent emulsion and stir it evenly for use.

[0105] Other details are exactly the same as in Example 1.

[0106] Comparative Example 6

[0107] This comparative example provides a production process for high-folding-resistance corrugated paper:

[0108] Waste paper raw material: same as in Example 1.

[0109] Glue: Mix cationic starch, solid sizing agent, ADK, styrene-acrylic adhesive, potassium aluminum sulfate, cationic rosin emulsion, chitosan, polyethylene glycol, polyethylene oxide and deionized water and stir well for later use.

[0110] Other details are exactly the same as in Example 1.

[0111] Comparative Example 7

[0112] This comparative example provides a production process for high-folding-resistance corrugated paper:

[0113] Waste paper raw material: same as in Example 1.

[0114] The long / short fiber ratio in this comparative example is 9:1, and the rest is completely consistent with Example 1.

[0115] Experimental Example 1

[0116] The corrugated base papers obtained in Examples 1-3 and Comparative Examples 1-7 were subjected to folding resistance tests. The results are shown in Tables 1 and 2.

[0117] Basis weight: GB / T 451.2, Thickness: GB / T 451.3, Tightness = Basis weight / Thickness, Water absorption: GB / T1540, Ring crush strength: GB / T 2679.8, Breaking length: GB / T 13023, Moisture content: GB / T 462, Folding endurance: GB / T 457.

[0118] Table 1

[0119] Folding test Ring pressure index (N·m / g) Fracture length (longitudinal) km Example 1 70 10.1 5.8 Example 2 68 10.3 6.0 Example 3 72 10.5 6.1 Comparative Example 1 55 9.3 5.0 Comparative Example 2 45 8.5 4.5 Comparative Example 3 38 8.0 4.0 Comparative Example 4 52 9.0 4.9 Comparative Example 5 65 9.7 5.3 Comparative Example 6 62 9.9 5.6 Comparative Example 7 48 7.8 4.0

[0120] Table 2

[0121] Quantitative g / m2 <![CDATA[Bulk density g / cm 3 > Water absorption g / m2 Example 1 145 0.652 30 Example 2 142 0.648 32 Example 3 143 0.650 33 Comparative Example 1 132 0.621 35 Comparative Example 2 138 0.625 38 Comparative Example 3 132 0.633 42 Comparative Example 4 135 0.621 36 Comparative Example 5 137 0.636 35 Comparative Example 6 133 0.638 33 Comparative Example 7 138 0.623 38

[0122] It can be seen from Tables 1 and 2 that without a dry pulping package (Comparative Example 1), the proportion of long fibers in the longer fibers will be insufficient (the long fibers in the dry pulping package can usually reach more than 2.2 mm, but the long fibers in the waste paper are usually only between 1.9-2.0 mm, and the length of the long fibers is relatively low). During the fine screening process, the fibers are severely damaged, the long fiber concentration of the longer fibers is relatively low, the fiber bonding force is reduced, and the folding resistance and edge pressure strength will both decrease; PVA wrapping the fibers reduces friction damage, NaOH softens the fiber cell wall and improves flexibility, and the absence of a protective agent (Comparative Example 2) leads to an increase in the fiber cutting rate during pulping and increased paper brittleness. Adding a protective agent in the pulping stage can significantly improve fiber integrity, which is a key process for folding resistance.

[0123] Cellulase optimizes the hydrogen bonds on the fiber surface, PAE forms a cross-linked network, and the reinforcing agent fills the gaps in the short fibers. The lack of additives (Comparative Example 3) leads to weak bonding between fibers and easy breakage when folded. The additive system is the core of improving folding resistance, and its absence will lead to a significant decline in performance.

[0124] Long fibers provide skeleton support, and short fibers fill the pores; a 5:5 ratio results in insufficient long fiber skeleton, which is prone to cracking when folded; a long fiber ratio of ≥70% is a necessary condition for high folding resistance, and reducing it to 50% (Comparative Example 4) will significantly weaken the mechanical properties; but excessive increase, with a ratio of ≥90% (Comparative Example 7), will cause the paper's flexibility to decrease (rigidity to increase), and the fibers will not easily bend and absorb stress when folded, and will easily break from the skeleton layer; the short fibers are reduced (only 10%), and the gaps between the long fibers cannot be effectively filled, exacerbating local stress concentration (such as the junction between the corrugated core paper and the face paper) during folding; the interlayer bonding force is reduced due to the reduction of short fibers (the role of short fibers as "interface bridges" is weakened), and it is easy to peel off from the layers when folded. The short fibers are reduced (filling capacity is reduced), and the internal void ratio of the paper increases slightly (the structure is loose), further weakening the ring pressure performance.

[0125] Segmented boiling makes starch gelatinization more thorough, and vacuum degassing avoids bubbles. Simple boiling (Comparative Example 5) results in coarse glue particles and uneven glue application; while complex glue (Comparative Example 6) not only increases costs, but also has limited improvement on the folding resistance of corrugated paper.

[0126] In summary, the present invention achieves stable production of highly foldable corrugated paper by combining diversified raw materials (dry pulping with long fibers), refined fiber treatment (enzymatic hydrolysis + wet strength agent / reinforcement agent), flexible papermaking process control (low shear + low-temperature drying), and precise glue preparation (staged boiling + vacuum degassing). However, the comparative examples, due to the lack of key parameters (such as insufficient dry pulping, simplified fiber processing, and defects in glue processing), have reduced properties such as fiber length, bonding strength, and surface quality, and ultimately significantly reduced folding resistance and other physical indicators (edge ​​pressure, ring pressure, etc.).

[0127] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made thereto. Therefore, such modifications and improvements, without departing from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A production process for high folding-resistant corrugated paper, characterized in that: The process comprises: Step 1: Mix different types of waste paper raw materials and hydraulically pulp them to obtain raw waste paper pulp with a concentration of 2.5-2.8%; Step 2: After high-concentration sand removal, coarse screening, and low-concentration sand removal, the original waste paper pulp enters a grading screen to separate the fibers in the waste paper pulp into long fibers and short fibers. The long fiber segment includes fine screening and long fiber concentration. The fine screening adopts a duplex fiber fine screening. 0.2-0.3% cellulase is added during the fine screening process. After concentration, the concentration of the long fibers is 8-10%. After concentration, a wet strength agent is added to obtain long fiber pulp. The short fiber segment includes short fiber concentration. After concentration, the concentration is 6-8%. After concentration, 0.3-0.5% fiber reinforcement is added to obtain short fiber pulp. Step three, mixing the long fiber pulp and the short fiber pulp in proportion, and carrying out papermaking and surface sizing treatment; wherein, papermaking includes mesh forming, pressing and dehydration, and drying in the front drying section to obtain an initial corrugated base paper with a dryness of 90-92%, and then the boiled glue liquid is used to apply sizing treatment to the surface of the initial corrugated base paper, and dried at 60-100 ° C to a dryness of 85-92%, and curled and cut to obtain high-folding-resistant corrugated base paper.

2. The production process of high folding-resistant corrugated paper according to claim 1, characterized in that: In the step 1, the waste paper raw materials include the following weight percentages: 35-40% of special grade waste paper, 24-28% of cardboard from pit card factory, 4-8% of mixed shopping mall waste paper, 8-12% of dry pulp bag, and 18-22% of industrial carton waste paper.

3. The production process of high folding-resistant corrugated paper according to claim 1, characterized in that: In the step 1, 0.5-1% of a fiber protective agent and 0.1-0.3% of NaOH are added to the hydraulic pulp, and the pH is adjusted to 8.5-9.

0.

4. The production process of high folding-resistant corrugated paper according to claim 1, characterized in that: In the step 1, the hydraulic pulping parameters are as follows: the pulping time is controlled to be 15-20 minutes and the rotation speed is 3000-3500 rpm; and the beating degree is 30-45°SR.

5. The production process of high folding-resistant corrugated paper according to claim 1, characterized in that: In the step 2, the compound fiber fine screen includes a pressure screen and a centrifugal screen.

6. The production process of high folding-resistant corrugated paper according to claim 1, characterized in that: In the step 2, the wet strength agent is PAE resin, and the addition amount is 0.5-1%.

7. The production process of high folding-resistant corrugated paper according to claim 1, characterized in that: In the step 3, the ratio of long fiber pulp to short fiber pulp is 6:4-8:

2.

8. The production process of high folding-resistance corrugated paper according to claim 1, characterized in that: In the step 3, the drying temperature of the front drying section is 40-90°C.

9. The production process of high folding-resistance corrugated paper according to claim 1, characterized in that: In the step 3, the glue solution contains starch glue with a concentration of 10-14% and a viscosity of 20-30 MPa.s, 100-150 g of amylase per ton of paper, and 3-4 kg of styrene acrylic sizing agent per ton of paper.

10. The production process of high folding-resistance corrugated paper according to claim 9, characterized in that: The glue solution is prepared by precisely controlling starch gelatinization and enzymatic hydrolysis through segmented heating, vacuum degassing and static ripening.