Production process of high-strength environment-friendly paperboard

Abstract

The invention relates to a production process of a high-strength environment-friendly paperboard, which comprises the steps of corrugated forming, surface paper bonding, multi-layer compounding and shaping post-treatment, and solves the problems that a single corrugated structure (such as a single-layer corrugated A or corrugated B) is mostly adopted in the prior art, and the impact resistance and compression resistance are limited obviously. An A / B ridge composite design is combined with a net-shaped template and a flexible filling material, so that the compressive strength of the paperboard is improved, and meanwhile, an aldehyde-free formula and high-value recycling of waste materials are adopted, so that environment-friendly and clean production is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of cardboard, and specifically to a production process for high-strength environmental protection cardboard. Background Art

[0002] Cardboard is a thick sheet material mainly made of pulp and processed through multiple processes. It is usually composed of multiple layers of paper or cardboard bonded and pressed together, having relatively high stiffness, strength, and buffering performance. Cardboard is widely used in the fields of packaging, printing, making paper boxes and cartons, etc., which can provide protection for goods, facilitate transportation and storage. At the same time, it is also commonly used in making display racks, file folders and other daily necessities, and is an indispensable basic material in industrial production and daily life.

[0003] In the production of traditional corrugated cardboard, to improve strength, high proportions of chemical additives (such as aldehyde-containing adhesives like urea-formaldehyde resin) or thick paper cores are often relied on, resulting in insufficient environmental protection (such as formaldehyde release and difficult degradation), and the interlayer bonding force depends on a single structural design (such as a single-layer corrugated core paper), and interlayer separation is likely to occur due to stress concentration, especially the performance drops significantly under complex loads or in humid environments. Summary of the Invention

[0004] In view of the above deficiencies, the purpose of the present invention is to provide a production process for high-strength environmental protection cardboard. Through the design of a multi-layer composite corrugated structure A / B corrugation combination, nano-material modified fillers and environmental protection adhesives, fine control of process parameters, and enhancement of the functional structure by filling a mesh template, the strength, environmental protection, and production stability of the cardboard are systematically improved to meet the requirements of high-end packaging for high-performance materials.

[0005] To achieve the above purpose, the present invention provides the following technical solutions.

[0006] A production process for high-strength environmental protection cardboard, including corrugated paper forming, face paper bonding, multi-layer composite, and post-setting treatment, characterized in that:

[0007] The cardboard includes A corrugation and B corrugation, and the A corrugation and B corrugation are multi-layer composite structures. The A corrugation paper core is 337 g / m 2 maple kraft paper, with a bursting index of 3.8 kpa·m 2 / g and a ring crush index of 11.5 N·m / g; the B corrugation paper core is 120 g / m 2Grade A corrugated paper such as A, with a ring crush index of 8.0 N·m / g; the A-flute and B-flute paper cores are pressed and shaped on a metal template by a corrugating roll at a high temperature of 150 - 180 °C and a pressure of 10 - 15 MPa. The surface paper is bonded by adjusting the temperature of the hot pressing roll to 80 - 120 °C to compound the pressed and shaped paper core with the surface paper to achieve rapid curing. The multi-layer compounding is to arrange the formed corrugated paper after bonding the surface paper in a multi-layer cross-distribution at different angles, and use an adhesive and a pressure roller to hot-press and shape between each layer. The post-treatment after shaping is to use a hot air circulation and drying system to reduce the moisture content of the multi-layer compounded cardboard to 8 - 12%, and control the flatness of the cardboard and reduce warping deformation through a tension adjusting roller and a cooling device.

[0008] The production process of this paper is as follows: First, place the reel-shaped base paper on a shaftless support and gradually unwind it under tension control. The paper web enters the corrugating machine through a preheating cylinder, and the corrugations are formed by a single-sided corrugating machine and adhered to the surface paper with starch adhesive to form a two-layer corrugated cardboard. Then, the two-layer cardboard is compounded with the two-layer A-flute cardboard and the two-layer B-flute cardboard and the surface paper through a gluing machine, dried and formed through a dryer, and then cut to the required length and width according to the production management system size requirements by a slitter scorer.

[0009] Furthermore, the corrugated paper forming includes a filling and a pressing and forming process. The filling is to fill a nano-calcium carbonate, cellulose nanocrystal and kaolin buffer layer between the two-layer corrugated core papers of the multi-layer compounded A-flute and B-flute according to a ratio of 1:2, and add an adhesive with a solid content of ≥25% to the kaolin buffer layer to avoid interlayer separation caused by stress concentration; the pressing and forming includes lamination bonding and corrugated structure forming. The lamination bonding is to adjust the pressure of the pressure roller to 15 - 18 MPa and the temperature of the pressure roller to 150 - 180 °C between the two-layer corrugated core papers and the middle kaolin buffer layer; the surface layer of the corrugated structure uses B-flute, with a flute height of 2.5 - 3 mm and the flute pitch adjusted to 6 - 7 mm, and the inner layer uses A-flute, with a flute height of 4.5 - 5 mm and a flute pitch of 8 - 9 mm; after pressing and forming, the surface layer B-flute is coated with glue, and is quickly shaped at 75 - 85 °C in the front section and slowly dried in segments at 55 - 65 °C in the rear section to avoid inactivation of nano-calcium carbonate due to high temperature.

[0010] Furthermore, the surface paper bonding uses 420 g / m 2 domestic first-class kraft linerboard as the surface paper, with a bursting strength index of 3.0 kPa·m 2 / g and a ring crush index of 11.5 N·m / g; the bonding uses a starch-based adhesive, and the gelatinization temperature is adjusted to 63 - 66 °C with caustic alkali, and the double-sided coating amount is 15 - 20 g / m 2 and the single-sided coating amount is 10 - 15 g / m 2, the penetration depth is within 1 / 4 of the paper thickness, and 0.07-1% of nano-silica and 0.07-1% of carboxymethyl cellulose (CMC) are also added to the starch-based adhesive; in the face paper bonding, the surface of the glue applicator roller of the coater adopts a honeycomb-shaped concave hole design with a diameter of about 0.5-1 mm. Through the mechanical scraping effect, the paste is evenly scraped onto the corrugated peaks to avoid glue accumulation or deficiency. The rotation speed of the glue applicator roller is slightly lower than that of the lower corrugating roller at a speed of 9:10, and the gap between the glue applicator roller and the corrugating roller is adjusted to 0.1-0.3 mm.

[0011] Further, the starch-based adhesive uses micronized corn starch as the main material, with a particle size ≤ 50 μm, a straight-chain starch content ≥ 25%, and a gelatinization temperature of 62-65°C; specifically, it is 20-25% corn starch, 75-80% water, 0.03-1% borax, 0.03-1% urea-formaldehyde resin borax, 0.03-1% tackifying resin, 0.4-0.9% NaOH (sodium hydroxide), and 0.02-1% hydrogen peroxide.

[0012] Further, for the multi-layer composite, a mesh template can be provided between the formed corrugated cardboard after the face paper is bonded. The mesh template is flatly bonded to the formed corrugated cardboard through a water-resistant adhesive. Pulp and flexible materials can be filled on the mesh template. After the filling of the mesh template is completed, a drying and curing treatment is carried out. During the drying process, a pressure roller is used to apply a pressure of 0.5-1.0 MPa to compact the mesh template and the corrugated cardboard in multiple layers. The mass ratio of the filling materials pulp and flexible materials in the mesh template is 7:3. The pulp is waste pulp, and the flexible materials are memory honeycombs, polyurethane foams, bio-based elastomers, or recycled plastic particles.

[0013] Further, the water-resistant adhesive is a starch-polyvinyl alcohol composite glue or an epoxy resin-modified glue with a high solid content ≥ 25% and a low viscosity (40-60 seconds, cup 4). The glue applicator roller with a mesh count of 70-80 meshes is used for the adhesive coating, and the glue penetration depth is controlled within 1 / 4 of the corrugated cardboard thickness.

[0014] Further, for the drying and curing preheating stage: 60-80°C, time 5-10 minutes to remove surface moisture, the main drying stage: 120-150°C, time 20-30 minutes to completely cure the adhesive, the compaction sequence: pre-press 0.2-0.3 MPa to remove air, main 0.5-1.0 MPa, continue for 10-15 seconds, and hold the pressure 0.3-0.5 MPa, time 5-10 seconds.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:.

[0016] 1. High strength and enhanced structural stability have led to a significant breakthrough in the mechanical properties of cardboard. Through the A / B corrugated composite structure and cross-laminated geometric mechanics design, the single-point stress of the traditional structure is transformed into uniform surface loading. The interlayer peel strength is ≥1.8 N / mm (only 0.8 - 1.2 N / mm in traditional processes), effectively solving the problem of interlayer separation. By filling a composite mitigation layer of nano-calcium carbonate (particle size ≤50 μm) and cellulose nanocrystals (CNC) between the corrugated medium papers and using an adhesive with a 1:2 ratio and 25% solid content, the strength is synergistically enhanced and the anti-deformation ability is achieved.

[0017] 2. The environmental performance of the paper has been upgraded, the cost has been greatly optimized, and the application scenarios have been expanded to high-value-added fields. Using corn starch as the main raw material and adding 0.07 - 1% nano-silica and CMC), formaldehyde-free production is achieved; the buffering performance of the filling material (pulp + memory honeycomb) enables the cardboard to have an energy absorption efficiency of >70% during drop impact, a 25% improvement compared to the traditional foam-filled structure, and is suitable for the packaging of precision instruments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the production process of the present invention;

[0019] Figure 2 It is a schematic diagram of the structure of the present invention;

[0020] Figure 3 It is the front, back, left, and right cross-sectional views of the two-layer lamination of the present invention in kind;

[0021] Figure 4 It is the finished product inspection report of the present invention.

[0022] In the figures: 1, face paper; 2, A corrugation; 3, B corrugation; 4, kaolin mitigation layer; 5, mesh template. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] In the description of the embodiments of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "connection" and "installation" should be understood in a broad sense. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. In addition, "communication" can be a direct communication or an indirect communication through an intermediate medium. Among them, "fixing" means that they are connected to each other and the relative positional relationship after connection remains unchanged. The orientation terms mentioned in the embodiments of the present invention, such as "inside", "outside", "top", "bottom", etc., are only references to the direction of the accompanying drawings. Therefore, the orientation terms used are for better and clearer explanation and understanding of the embodiments of the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the embodiments of the present invention.

[0025] In the embodiments of the present invention, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0026] Please refer to Figures 1-4 , a high-strength environmental protection cardboard production process provided by the present invention, a high-strength environmental protection cardboard production process, including corrugated paper forming, face paper bonding, multi-layer composite and post-treatment processes.

[0027] The cardboard includes A-flute 2 and B-flute 3. The A-flute 2 and B-flute 3 are multi-layer composite structures. The paper core of the A-flute 2 is 337 g / m 2 maple kraft paper, with a bursting strength index of 3.8 kPa·m 2 / g and a ring crush index of 11.5 N·m / g; the paper core of the B-flute 3 is 120 g / m 2 grade A corrugated paper, with a ring crush index of 8.0 N·m / g. The paper cores of the A-flute 2 and B-flute 3 are pressed and shaped on a metal template by a corrugating roll at a high temperature of 150 - 180 °C and a pressure of 10 - 15 MPa. The face paper bonding is achieved by adjusting the temperature of the hot press roll to 80 - 120 °C to quickly cure the pressed and shaped paper core and the face paper 1. The pressure of the press roll is precisely matched to make the size accuracy of the A / B flute reach ±0.1 mm, and the hot press curing time is shortened to 15 seconds, with the efficiency increased by 50% compared with the traditional process.

[0028] The multi-layer composite is formed by arranging multiple layers of corrugated paper with different angles cross-distributed after the surface paper 1 is bonded. Between each layer, hot pressing and shaping are carried out using an adhesive and a pressure roller. The post-treatment after shaping is to adopt a hot air circulation and drying system to reduce the moisture content of the multi-layer composite cardboard to 8-12%. Through a tension adjusting roller and a cooling device, the flatness of the cardboard is controlled and warping deformation is reduced. During shaping, hot air circulation and a tension adjusting roller (tension fluctuation ≤ ±2%) are used in cooperation with a cooling device to make the warping degree of the cardboard ≤ 1 mm / m, meeting the printing-level flatness requirements for high-end packaging.

[0029] Among them, the corrugated paper forming includes a filling and a pressing process. The filling is to fill a nano-calcium carbonate, cellulose nanocrystal, and kaolin buffer layer 4 between two layers of corrugated core papers of multi-layer composite A-flute 2 and B-flute 3 in a ratio of 1:2. An adhesive with a solid content ≥ 25% is added to the kaolin buffer layer 4 to avoid interlayer separation caused by stress concentration; the "bridging effect" of the nanoparticles increases the ring crush index of the core paper by 15%, and the burst index of A-flute reaches 3.8 kPa·m 2 / g, and the water-resistant bonding strength of B-flute is increased by 20%.

[0030] Among them, the pressing forming includes lamination bonding and corrugated structure forming. The lamination bonding is to adjust the pressure of the pressure roller to 15-18 MPa and the temperature of the pressure roller to 150-180°C between two layers of corrugated core papers (A-flute 2 and B-flute 3) and the middle kaolin buffer layer; through a lamination pressure of 15-18 MPa, the density of the buffer layer reaches 0.8-1.0 g / cm 3 .

[0031] Among them, the surface layer of the corrugated structure uses B-flute 3 with a flute height of 2.5-3 mm and the flute pitch adjusted to 6-7 mm, and the inner layer uses A-flute 2 with a flute height of 4.5-5 mm and a flute pitch of 8-9 mm; after pressing forming, the surface layer B-flute 3 is coated with glue for bonding, and after bonding, it is quickly shaped at 75-85°C in the front section and slowly dried in segments at 55-65°C in the rear section, so that the active retention rate of nano-calcium carbonate ≥ 95%, avoiding the inactivation of the filler caused by traditional high temperature (>100°C), and ensuring the structural stability during long-term use. The surface layer B-flute provides surface buffering and flatness, and the inner layer A-flute bears the core compressive load, forming a "soft outside and hard inside" mechanical gradient distribution. The compressive strength of the seven-layer cardboard can reach more than 8500 N / m, which is more than 50% higher than that of the traditional single-flute structure.

[0032] Among them, the surface paper bonding is to use domestic first-class kraft box board with a weight of 420 g / m 2 as the surface paper 1, with a burst index of 3.0 kpa·m 2 / g, ring crush index 11.5 N·m / g; Starch-based adhesive is used for bonding. The starch-based adhesive uses micronized corn starch as the main material, with a particle size ≤ 50 μm, amylose content ≥ 25%, and the gelatinization temperature is adjusted by caustic soda to be 63 - 66°C; Specifically, it is 20 - 25% corn starch, 75 - 80% water, 0.03 - 1% borax, 0.03 - 1% urea formaldehyde resin borax, 0.03 - 1% tackifying resin, 0.4 - 0.9% NaOH (sodium hydroxide), and 0.02 - 1% hydrogen peroxide. The double-sided coating amount is 15 - 20 g / m 2 , the single-sided coating amount is 10 - 15 g / m 2 , the glue consumption is 20% less than that of the traditional one, and the penetration depth is within 1 / 4 of the paper thickness, avoiding the softening of the cardboard caused by excessive penetration.

[0033] Among them, 0.07 - 1% nano-silica and 0.07 - 1% carboxymethyl cellulose (CMC) are also added to the starch-based adhesive; replacing the traditional urea formaldehyde resin, the formaldehyde release amount is 0 (better than 0.1 mg / L of the national standard HJ 2541 - 2016), and it meets the EU REACH certification.

[0034] Among them, for the bonding of the face paper 1, the surface of the glue applicator roller of the coating machine adopts a honeycomb-shaped concave hole design with a diameter of about 0.5 - 1 mm. Through the mechanical scraping effect, the paste is evenly scraped onto the corrugated peaks, avoiding glue accumulation or shortage. The coating amount control accuracy is ±5%, the glue penetration is uniform, and the waste glue rate ≤ 0.3%. It is suitable for high-speed production lines. The rotation speed of the glue applicator roller is slightly lower than that of the lower corrugating roller at a speed of 9:10, and the gap between the glue applicator roller and the corrugating roller is adjusted to be 0.1 - 0.3 mm.

[0035] Among them, for the multi-layer composite, a mesh template 5 can be provided between the formed corrugated cardboard after the face paper is bonded. The mesh template 5 is flatly bonded to the formed corrugated cardboard through a water-resistant adhesive. Pulp and flexible materials can be filled on the mesh template 5. After the filling of the mesh template 5 is completed, drying and curing treatment is carried out. During the drying process, a pressure roller is used to apply a pressure of 0.5 - 1.0 MPa to compact the mesh template 5 and the corrugated cardboard in multiple layers. A lightweight rigid frame is formed to convert the single-point concentrated load into a surface area dispersed load. After being pressure-compacted, the compressive strength of the cardboard is increased by more than 50%. Especially in large-size boards (such as 1200 mm × 1000 mm), the central deflection is reduced from 5 mm of the traditional structure to less than 2 mm.

[0036] Among them, the mass ratio of the pulp and the flexible material filled in the mesh template 5 is 7:3. The pulp is waste pulp, and the flexible material is memory honeycomb, polyurethane foam, bio-based elastomer or recycled plastic particles. Filling waste pulp with a 7:3 ratio (providing structural stiffness) and flexible materials (memory honeycomb / bio-based elastomer, absorbing impact energy) reduces the breakage rate of the cardboard in the 60° inclination drop test (height 1m) from 15% of the traditional process to less than 5%, meeting the transportation protection requirements of precision products such as electronic appliances. Filling materials such as memory honeycomb can effectively relieve the high-frequency stress in transportation vibration, avoiding the interlayer cracking caused by resonance of traditional rigid structures, and is especially suitable for packaging scenarios sensitive to vibration such as medical devices.

[0037] Among them, the water-resistant adhesive is a starch-polyvinyl alcohol composite glue or an epoxy resin-modified glue with a high solid content ≥25% and a low viscosity (40 - 60 seconds, coating - 4 cup), replacing traditional solvent-based adhesives. The formaldehyde release amount ≤0.05mg / L, and the bonding strength retention rate ≥80% after soaking in water for 24 hours, which is better than traditional water-resistant adhesives. The bonding coating uses a glue roller with a mesh number of 70 - 80 meshes (the mesh cavity volume is 0.1 - 0.2mm 3 / cm 2 ), and the penetration depth of the glue is controlled within 1 / 4 of the thickness of the corrugated cardboard to prevent the glue from penetrating into the corrugated core paper and affecting the buffering performance.

[0038] Among them, in the drying and curing preheating stage: 60 - 80°C, for 5 - 10 minutes, quickly removing the surface free water to prevent the density unevenness caused by moisture migration of the filling material; in the main drying stage: 120 - 150°C, for 20 - 30 minutes, high temperature promotes the complete curing of the adhesive (curing degree ≥95%), and at the same time, a pressure roller of 0.5 - 1.0MPa compacts the mesh template, making the density of the filling material reach 0.4 - 0.6g / cm 3 , taking into account lightweight and stiffness.

[0039] Among them, the compaction sequence: pre-pressing at 0.2 - 0.3MPa to remove air, main pressing at 0.5 - 1.0MPa for 10 - 15 seconds, and pressure holding at 0.3 - 0.5MPa for 5 - 10 seconds. The segmented compaction sequence avoids the material slip caused by traditional one-time pressing. The mesh structure of the mesh template forms "mechanical bite points", forming a microscopic interlocking structure with the honeycomb-shaped corrugated peaks of the corrugated core paper. Cooperating with the 0.2 - 0.3MPa pre-pressing to remove air and the 0.5 - 1.0MPa main pressing to compact the filling material, the interlayer peel strength is increased from 1.2N / mm of the traditional composite structure to more than 1.8N / mm, and the peel strength retention rate ≥90% in a humid environment (humidity ≥85%).

[0040] Among them, for the adhesive coating applicator roll after multi-layer composite compaction, the mesh number is 70 - 80 meshes, the doctor blade gap is 0.1 - 0.3 mm, the coating amount error is ≤ 5%, and the defective bonding rate is reduced from 5% of the traditional process to below 1%, reducing waste loss.

[0041] Embodiment

[0042] The production process steps of the high-strength environmentally friendly cardboard of the present invention are as follows:

[0043] I. Unwinding of base paper and corrugation forming:

[0044] 1. The equipment configuration of the production line adopts a hydraulic drive shaftless support (such as the Mackino KE309 series), which supports the quick loading and unloading of a reel paper with a diameter of 1000 - 1500 mm and a weight of 500 - 1000 kg, and is equipped with a magnetic powder brake and a tension sensor (accuracy ±1 N) to achieve closed-loop control of the paper web tension. The initial tension of the equipment tension parameter is set to 80 - 100 N (adjusted according to the basis weight of the base paper, taking the upper limit for 337 g / m 2 Maple kraft paper, taking the lower limit for 120 g / m 2 Class A corrugated paper), and automatically linearly increases to 150 - 200 N as the paper roll diameter decreases, with a fluctuation range of ≤ ±2%. When the remaining diameter of the paper roll < 150 mm, the automatic paper splicer is triggered (error ≤ 0.5 mm), the tension fluctuation during the paper splicing process < 5%, and the waste loss rate ≤ 0.3%.

[0045] 2. Preheating cylinder treatment The paper web is introduced into the preheating cylinder (diameter 800 mm, surface chrome-plated treatment) through a guide roller, and the cylinder body temperature is controlled at 80 - 120 °C by steam heating (pressure 0.5 - 0.8 MPa) (adjusted according to the moisture content of the base paper, taking 100 - 120 °C when the moisture content > 8%, and taking 80 - 100 °C when ≤ 8%). The paper web wrap angle is adjusted to 180° - 270° through a swing roller (240° for A-flute base paper, 180° for B-flute base paper) to ensure uniform preheating, and the moisture content deviation ≤ ±0.5%. A float type steam trap (drainage capacity 50 kg / h) is configured and manually checked once an hour to avoid uneven temperature caused by water accumulation.

[0046] 3. Corrugator The corrugation forming parameters adopt an SF-280 electric universal joint single-sided corrugator (corrugating roll diameter 280 mm, rotation speed 80 - 120 r / min), which supports the switching between A-flute (flute height 4.5 - 5 mm, flute pitch 8 - 9 mm) and B-flute (flute height 2.5 - 3 mm, flute pitch 6 - 7 mm), and the forming pressure is 10 - 15 MPa (taking the upper limit for A-flute and the lower limit for B-flute). The corrugating roll is heated by steam (temperature 150 - 180 °C, accuracy ±2 °C) to ensure that the paper core fibers are softened and shaped, and the corrugation height error after forming ≤ ±0.1 mm. The corrugator is linked with the shaftless support, and the line speed matching accuracy ≤ ±0.5 m / min to avoid paper web stretching or wrinkling.

[0047] 4. In the face paper laminating process, a starch-based adhesive (solid content 25%, added with 0.5% nano-silica and 0.5% CMC) is evenly coated on the corrugated peaks of the corrugated medium by a metering pump. The coating amount is 15 - 20 g / m 2 (when laminating on both sides, it is 10 - 15 g / m for one side 2 ), and the penetration depth ≤ 1 / 4 of the paper thickness. The pressure of the upper pressing roller is 8 - 12 MPa, and the temperature is 80 - 120 °C (the surface of the hot pressing roller is coated with a Teflon coating, and the anti-sticking effect ≥ 99%), ensuring that the peel strength between the face paper (420 g / m 2 kraft linerboard) and the corrugated medium ≥ 1.8 N / mm. After lamination, it is quickly cured by a cooling roller (temperature ≤ 40 °C), and the cooling time is 3 - 5 seconds to avoid reverse adhesion of the adhesive.

[0048] II. Multi-layer composite compaction:

[0049] 1. In the multi-layer structure design, the formed two layers of cardboard of A-flute and B-flute (the surface layer is B-flute, and the inner layer is A-flute) are cross-compound laminated through a gluing machine, and the included angle between each layer is 45° - 90° (adjusted according to the load-bearing direction, taking 90° for mainly longitudinal load-bearing and 45° for mainly transverse load-bearing). A mesh template (the mesh template can be made of PP material, with mesh holes of 3 - 5 mm, or honeycomb cardboard) can be laminated again between the two layers of cross-compound laminated cardboard to fill the pulp (70% waste paper pulp, beating degree 30° SR) and memory honeycomb (30%). The filling density is 0.4 - 0.6 g / cm 3 , and air is removed through pre-pressing (0.2 - 0.3 MPa). A hollow tubular support frame (round / elliptical, made of 180 g / m 2 high-strength corrugating base paper, ring crush index 8.5 N·m / g) can also be laid between layers, with a frame spacing of 20 - 30 mm, to increase the compressive strength by 20%. Then, the mesh template or support frame is flatly bonded by a water-resistant starch-PVA composite adhesive (solid content 25%, viscosity 40 - 60 seconds). Among them, for multi-layer composite, the support structure and mesh template filling materials can also not be used, and the formed two layers of cardboard of A-flute and B-flute are directly cross-laminated, bonded, and then compacted.

[0050] 2. The multi-layer cardboard formed after lamination enters a hot air circulation dryer (15 - 20 m in length, with temperature zone control): In the front section, rapid shaping is carried out: the temperature is 75 - 85°C, the wind speed is 10 - 15 m / s, and the time is 5 - 8 minutes to preliminarily cure the surface adhesive (curing degree ≥ 60%). In the rear section, slow-release drying is carried out: the temperature is 55 - 65°C, the wind speed is 5 - 8 m / s, and the time is 10 - 15 minutes to ensure that the active retention rate of nano-calcium carbonate is ≥ 95%, and the final moisture content is controlled at 8 - 12% (accuracy ±1%). During the drying process, the support structure or mesh template is compacted by a pressure roller (diameter 300 mm, pressure 0.5 - 1.0 MPa), the pressure uniformity error is ≤ 5%, and the cardboard thickness deviation is ≤ ±0.05 mm.

[0051] III. Slitting and inspection:

[0052] 1. An NSS computer longitudinal cutting and indentation machine (accuracy ±0.5 mm) and a cross-cutting machine (cutting accuracy ±1 mm) are used to automatically adjust the blade spacing and pressure according to the instructions of the production management system (MES). The depth of the indentation wheel is 0.1 - 0.2 mm (adjusted according to the cardboard thickness, 0.15 mm for five-layer cardboard and 0.2 mm for seven-layer cardboard) to ensure that the angle deviation after folding is ≤ ±1°. The waste edges generated by slitting (width ≤ 5 mm) are processed by a paper shredder (blade life ≥ 100 hours) and then mixed with the waste paper pulp for reuse, and the reuse rate is ≥ 90%.

[0053] 2. Quality inspection: After slitting, the cardboard needs to pass an online inspection system: Laser thickness gauges (accuracy ±0.02 mm) are used for thickness measurement, and it is measured every 5 meters, and the thickness fluctuation is ≤ ±0.1 mm. Visual inspection systems (resolution 0.1 mm) are used for appearance inspection to identify defects such as glue accumulation and indentation offset, and the reject rate is ≤ 0.5%.

[0054] Through the above technological steps, the production of this type of cardboard realizes the fine control of the whole process from raw paper processing to finished product slitting. It not only ensures the high strength and environmental protection of the cardboard (formaldehyde release amount 0), but also significantly improves the production efficiency and material utilization rate, and expands the applicability of the cardboard. For example, when designing a multi-layer composite structure, the cardboard can also choose a combination of 3A + 2B + 2C corrugations and IF iron foil filling, with a burst strength ≥ 2000 kPa, suitable for heavy component packaging. When designing a multi-layer composite structure, memory honeycomb materials (rebound rate ≥ 90%) are filled to replace EPS foam, which complies with the RoHS hazardous substances restriction directive and is suitable for precision electronic and electrical packaging. Epoxy resin film (thickness 0.05 mm) is used on the surface to improve the moisture resistance of the cardboard (water absorption rate ≤ 5%), meeting the ISO11607 sterilization requirements and conforming to high-end packaging fields such as medical devices.

[0055] It is obvious to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Accordingly, all changes that fall within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A high-strength environmental protection cardboard production process, including corrugated paper forming, face paper bonding, multi-layer composite, and post-setting treatment, characterized in that: The cardboard described above includes A flute and B flute. The A flute and B flute are multi-layer composite structures. The core of the A flute is 337 g / m 2 maple kraft paper with a bursting strength index of 3.8 kPa·m 2 / g and a ring crush index of 11.5 N·m / g. The core of the B flute is grade A corrugated paper of 120 g / m 2 with a ring crush index of 8.0 N·m / g; The corrugated paper forming includes a filling and pressing forming process. The filling is to fill a nano-calcium carbonate, cellulose nanocrystal, and kaolin relief layer between two layers of corrugated core paper of multi-layer composite A flute and B flute according to a ratio of 1:

2. A binder with a solid content of ≥25% is added to the kaolin relief layer to avoid interlayer separation caused by stress concentration; The pressing forming includes lamination bonding and corrugated structure forming. The lamination bonding is to adjust the pressure of the pressure roller between two layers of corrugated core paper and the middle kaolin relief layer to 15-18 MPa, and the temperature of the pressure roller is 150-180 °C; The surface layer of the corrugated structure uses B flute, the flute height is 2.5-3 mm, the flute pitch is adjusted to 6-7 mm, the inner layer uses A flute, the flute height is 4.5-5 mm, and the flute pitch is 8-9 mm; After pressing forming, the surface layer B flute is coated with glue, and it is quickly set at 75-85 °C in the front section and slowly dried in sections at 55-65 °C in the rear section to avoid inactivation of nano-calcium carbonate due to high temperature; The facial tissue is bonded using 420 g / m 2 Domestic first-class kraft linerboard is used as the facial tissue, with a bursting index of 3.0 kPa·m 2 / g and a ring crush index of 11.5 N·m / g; starch-based adhesive is used for bonding, and caustic alkali is used to adjust the gelatinization temperature to 63 - 66 °C. The double-sided coating amount is 15 - 20 g / m 2 , and the single-sided coating amount is 10 - 15 g / m 2 , and the penetration depth is within 1 / 4 of the paper thickness. 0.07 - 1% nano-silica and 0.07 - 1% carboxymethyl cellulose (CMC) are also added to the starch-based adhesive; The multi-layer composite is to cross-distribute the formed corrugated paper after face paper bonding at multiple different angles, and use a binder and a pressure roller to thermally set between each layer.

2. The high-strength environmental protection cardboard production process according to claim 1, characterized in that: In the multi-layer composite, a mesh template can be provided between the formed corrugated cardboard after face paper bonding. The mesh template is flatly bonded to the formed corrugated cardboard through a water-resistant binder. Pulp and flexible materials can be filled on the mesh template. After the filling of the mesh template is completed, drying and curing treatment is carried out. During the drying process, a pressure roller is used to apply a pressure of 0.5-1.0 MPa to compact the mesh template and the corrugated cardboard in multiple layers.

3. The production process of a high-strength environmental protection cardboard according to claim 1, characterized in that: The post-setting treatment is to use a hot air circulation and drying system to reduce the moisture content of the cardboard after multi-layer composite to 8-12%, and control the flatness of the cardboard and reduce warping deformation through a tension adjusting roller and a cooling device.

4. A high-strength environmental protection cardboard production process according to claim 1, characterized in that: The A flute and B flute paper cores are pressed and formed on a metal template by a corrugating roller at a high temperature of 150-180 °C and a pressure of 10-15 MPa. The face paper bonding realizes rapid curing by adjusting the temperature of the hot pressing roller to 80-120 °C and compounding the pressed and formed paper core with the face paper.

5. The production process of a high-strength environmentally friendly cardboard according to claim 1, characterized in that: In the face paper bonding, the surface of the glue applicator roller of the coater adopts a honeycomb-shaped concave hole design with a diameter of about 0.5-1 mm. The rotation speed of the glue applicator roller is slightly lower than that of the lower corrugating roller at a speed of 9:10, and the gap between the glue applicator roller and the corrugating roller is 0.1-0.3 mm.

6. The high-strength environmental protection cardboard production process according to claim 1, characterized in that: The starch-based binder uses micronized corn starch as the main material, with a particle size of ≤50 μm, a straight-chain starch content of ≥25%, and a gelatinization temperature of 62-65 °C; Specifically, it is 20-25% corn starch, 75-80% water, 0.03-1% borax, 0.03-1% urea-formaldehyde resin borax, 0.03-1% tackifying resin, 0.4-0.9% NaOH (sodium hydroxide), and 0.02-1% hydrogen peroxide.

7. A high-strength environmental protection cardboard production process according to claim 2, characterized in that: The mass ratio of the pulp and flexible materials filled in the mesh template is 7:

3. The pulp is waste pulp, and the flexible materials are memory honeycomb, polyurethane foam, bio-based elastomer, or recycled plastic particles.

8. A high-strength environmental protection cardboard production process according to claim 2, characterized in that: The water-resistant adhesive mentioned above is a starch-polyvinyl alcohol composite glue or an epoxy resin-modified glue with a high solid content ≥ 25% and a low viscosity (40 - 60 seconds, Coat-4 cup). For adhesive coating, a coating roller with a mesh number of 70 - 80 is used, and the penetration depth of the glue is controlled within 1 / 4 of the thickness of the corrugated cardboard.

9. A high-strength environmental protection cardboard production process according to claim 2, characterized in that: For the drying and curing preheating stage: 60 - 80 °C, for a time of 5 - 10 minutes to remove surface moisture; for the main drying stage: 120 - 150 °C, for a time of 20 - 30 minutes to completely cure the adhesive. For the pressing sequence: pre-pressing at 0.2 - 0.3 MPa to expel air, main pressing at 0.5 - 1.0 MPa for 10 - 15 seconds, and holding pressure at 0.3 - 0.5 MPa for 5 - 10 seconds.

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