Multi-cylinder and multi-cylinder paperboard papermaking machine and papermaking method

Abstract

The invention relates to the technical field of papermaking, in particular to a multi-rotary-screen multi-cylinder paperboard papermaking machine and a papermaking method, and the papermaking machine comprises a forming part, a pressing part, a front drying part, a semi-dry pressing part, a rear drying part, a calender, a scanning device and a paper cutter which are sequentially arranged; the papermaking method comprises the steps of pulping, pulp preparation, forming, squeezing, pre-drying, semi-dry squeezing, post-drying, calendaring, quality detection and slitting. According to the invention, quality indexes of paper pulp and pulp are strictly controlled in the steps of pulping and proportioning, and an optimal range of the quality indexes of the paper pulp is given; equipment and processes of forming, squeezing and other steps are improved, a forming method that multiple layers of wet paper webs are sequentially manufactured with paper and then compounded is adopted, raw materials are manufactured into paperboard flat paper suitable for being directly used in downstream factories at a time, the paper pulp index and the pulp matching ratio are improved, and the production efficiency is improved. And each layer of wet paper web is manufactured by adopting basically same papermaking equipment and papermaking process parameters, so that the wet paper webs with similar properties can be obtained, and the paper board is not easy to layer, blister and warp and deform.

Description

Technical Field

[0001] The invention relates to the technical field of papermaking, and in particular to a multi-cylinder paperboard papermaking machine and a papermaking method. Background Art

[0002] With the continuous progress of society, green life and environmental awareness have gradually become a mainstream thought in today's world. Replacing wood, plastic, glass and metal with paper has become a consensus for sustainable development. Under this circumstance, various packaging boxes, pallets, boxes and toys made of paper products have emerged. They have the characteristics of light weight, high strength and good cushioning, low cost, and can also print exquisite product information on the surface. In particular, because they use natural plant raw materials, they can be completely degraded within 45 to 90 days in the natural environment, and can also be composted at home. The main component after degradation is organic fertilizer, and no garbage residue or pollution will be generated; at the same time, paper products also have a high recycling and reuse value of recycled paper, so paper products have been constantly appearing in various fields with new faces.

[0003] Among various paper products, one-time formed paperboard is manufactured in one step on the production line, eliminating the intermediate compounding link. Therefore, one-time formed paperboard has better environmental protection, high strength, impact resistance, cushioning and lower cost. One-time formed paperboard occupies an important position in the packaging and printing industry. In the existing production technology, one-time formed paperboard is generally composed of a structure of five or more layers, namely, a surface layer, a surface lining layer, a core layer, a bottom lining layer, and a bottom layer. In the production process, one-time formed paperboard is prone to stratification, blistering, warping, deformation and difficulty in slitting due to the inconsistent pulp properties between layers, poor moisture uniformity, poor drying and high strength of the paperboard itself during the forming, pressing, drying and slitting processes. This leads to quality problems such as low quality of the paperboard, uneven cutting edges of the paperboard and a lot of paper hair. Summary of the invention

[0004] In view of the problems of delamination, blistering, warping and deformation, and difficulty in slitting of paperboard in the prior art solutions, the present invention provides a multi-cylinder paperboard papermaking machine and a papermaking method.

[0005] The present invention provides the following technical solutions:

[0006] A multi-cylinder paperboard papermaking machine, comprising a forming section, a pressing section, a front drying section, a semi-dry pressing section, a rear drying section, a calender, a scanning device and a paper cutter arranged in sequence;

[0007] The forming section comprises a plurality of formers, a first press, a second press, and a plurality of high-position boxes arranged in sequence along the forming net, wherein the high-position boxes are connected to the sizing pipes of the formers through pipelines, the mounting bases of the plurality of formers are lowered in sequence, and an adhesive nozzle is arranged between two adjacent formers;

[0008] The pressing section comprises a plurality of double-felt presses and a plurality of single-felt presses arranged in sequence; the upper roll of the double-felt press is a blind hole roll, and the lower roll is a vacuum roll; the upper roll of the single-felt press is a natural stone roll, and the lower roll is a flat rubber roll;

[0009] The front drying section and the rear drying section each include a plurality of drying cylinder groups arranged in sequence, and the drying cylinder group includes a plurality of drying cylinders connected by a felt transmission;

[0010] The semi-dry pressing section comprises a semi-dry pressing machine, the upper roller of the semi-dry pressing machine is a heat-resistant rubber roller, and the lower roller is a gloss drying cylinder.

[0011] A papermaking method of a multi-cylinder paperboard papermaking machine comprises the following steps:

[0012] Pulping, preparing pulp, filler and dry strength agent, the pulp includes long fiber pulp, short fiber pulp, surface layer pulp, bottom layer pulp, lining layer pulp, core layer pulp and thermomechanical pulp, and controlling multiple indicators of the above-mentioned multiple pulps to be almost consistent, a better indicator is that the concentration of the pulp is 2.5-4.5wt%, the fiber wet weight is 2-5g, and the pH value is 6-8, which is conducive to similar properties of the wet paper web after forming;

[0013] Mixing the pulp, mixing the short fiber pulp, the long fiber pulp, the surface layer pulp, the bottom layer pulp and the dry strength agent to obtain the surface layer pulp and the bottom layer pulp; mixing the core layer pulp, the thermomechanical pulp, the filler and the dry strength agent to obtain the core layer pulp; mixing the lining layer pulp, the thermomechanical pulp, the filler and the dry strength agent to obtain the lining layer pulp;

[0014] Forming, conveying the bottom layer slurry, lining layer slurry, core layer slurry and surface layer slurry to the forming section, using the same papermaking equipment and papermaking process parameters to form the bottom layer wet paper web, bottom lining layer wet paper web, core layer wet paper web, surface lining layer wet paper web and surface layer wet paper web respectively, spraying adhesive between each layer of wet paper web and compounding from bottom to top in sequence to form a paperboard wet paper web; each layer of wet paper web papered using substantially the same papermaking equipment and papermaking process parameters has similar properties, and is bonded by adhesive, so that the paperboard wet paper web is formed in one step, and does not need to be processed or modified in the intermediate process, saving raw materials and energy, reducing waste, and making the paperboard less likely to produce delamination, blistering, warping and deformation, which can enhance the quality of the paperboard on the one hand, and is conducive to the dehydration of the paperboard wet paper web in the forming, pressing and drying steps on the other hand, reducing energy consumption;

[0015] Pressing: the wet paper web of the paperboard is dehydrated by the first lower vacuum pre-pressing, upper vacuum pre-pressing, second lower vacuum pre-pressing, vacuum positive pressure, large roller vacuum positive pressure, large roller blind hole pressure, first stone roller smooth pressure, and second stone roller smooth pressure in sequence; the eight pressing processes can effectively remove moisture from the wet paper web of the paperboard and improve the quality indicators of the wet paper web of the paperboard;

[0016] Pre-drying: the wet paper web after squeezing and dehydration is sent to the pre-drying section to further remove moisture to form a paper web. The adhesive is gelled under high temperature heating to improve the bonding strength between the layers of the paper web.

[0017] Semi-dry pressing, which humidifies the paperboard web with water mist and performs hot pressing in the pressing area composed of a gloss drying cylinder and a lower pressing roller, thereby improving the glossiness and tightness of the paper surface and other quality indicators, and also helps to improve the uniformity of moisture and reduce the risk of warping, deformation, slitting difficulties and other problems;

[0018] Post-drying: the paperboard web is sent to the post-drying section to remove moisture again;

[0019] Calendering: sending the paperboard web into the calender to further improve the quality indicators such as gloss and tightness of the paper surface;

[0020] Quality inspection, scanning the paperboard web to obtain the inspection results, and adjusting the operating parameters of the previous steps to improve the quality of the paperboard web;

[0021] Slitting: cutting the cardboard web into qualified finished flat paper.

[0022] Preferably, in the pulping step,

[0023] The concentration of the short fiber pulp, long fiber pulp, surface layer pulp and bottom layer pulp is 2.5-4.5wt%, the beating degree is 30-50°SR, the fiber wet weight is 2-5g, and the pH value is 6-8;

[0024] The concentration of the lining layer pulp and the core layer pulp is 2.5-4.5wt%, the beating degree is 15-40°SR, the fiber wet weight is 2-5g, and the pH value is 6-8;

[0025] The thermomechanical pulp has a concentration of 2.5-4.5 wt %, a beating degree of 8-20° SR, a fiber wet weight of 2-5 g, a pH value of 6-8, and a 40-mesh screen pass rate of 70-90 wt %.

[0026] Preferably, in the pulping step,

[0027] Using 10-20wt% of waste newsprint, 10-20wt% of office waste paper, 20-50wt% of waste book and magazine paper, and 10-60wt% of packaging waste paper as raw materials, after crushing, deslagging, desanding, screening, and classification, they are concentrated and refined to obtain short fiber pulp and long fiber pulp. The main difference between the two is the fiber length and diameter. The fiber length and diameter of the long fiber pulp are larger, while the fiber length and diameter of the short fiber pulp are smaller.

[0028] Using 40-60 wt% of recycled wood pulp residue and 40-60 wt% of recycled bamboo pulp residue as raw materials, a surface layer pulp is prepared;

[0029] Using 50-70wt% of waste book and magazine paper and 30-50wt% of packaging waste paper as raw materials to prepare bottom pulp;

[0030] Using 50-70 wt% of mixed waste paper and 30-50 wt% of waste paper boxes and waste cardboard as raw materials, a lining pulp is prepared;

[0031] Using 50-70 wt% of mixed waste paper and 30-50 wt% of waste paper boxes and waste cardboard as raw materials to prepare core layer pulp;

[0032] Thermomechanical pulp is prepared by using 50-70wt% of miscellaneous wood chips, 10-20wt% of waste building template chips, 10-20wt% of discarded wood packaging box chips and 10-20wt% of bamboo chips as raw materials, spraying wood chip treatment enzymes uniformly, mixing, fermenting, preheating, refining, screening, deslagging, desanding, concentrating and refining.

[0033] Preferably, in the slurry preparation step,

[0034] The short fiber pulp, the long fiber pulp, the surface layer pulp, the bottom layer pulp and the dry strength agent are mixed in a mass ratio of 10-25:10-25:5-25:25-60:0-5 to prepare the surface layer pulp;

[0035] The short fiber pulp, the long fiber pulp, the surface layer pulp, the bottom layer pulp and the dry strength agent are mixed in a mass ratio of 10-25:10-25:5-25:25-60:0-5 to prepare the bottom layer pulp;

[0036] The core layer pulp, the thermomechanical pulp, the filler and the dry strength agent are mixed in a mass ratio of 20-60:30-50:5-30:0-5 to prepare the core layer pulp;

[0037] The lining slurry, the thermomechanical pulp, the filler and the dry strength agent are mixed in a mass ratio of 20-60:30-50:5-30:0-5 to prepare the lining slurry;

[0038] The concentration, fiber wet weight and pH value of the above-mentioned pulps are almost the same, but the beating degrees are quite different. When the beating degree is high, the pulp fibers are mostly cut, and there are more fine fibers in the pulp. When used in the surface layer and the bottom layer, good paper surface quality can be obtained, and the paper surface is delicate and smooth; when the beating degree is low, the fibers are relatively coarse and not fully destroyed, and there are more long fibers. When used in the core layer and the lining layer, a bridging effect is formed, which is beneficial for water filtration. However, the large difference in beating degree brings another problem: it is more likely to cause delamination and blistering of the cardboard. Therefore, the pulp is prepared in a reasonable ratio. After the pulping is completed, the difference in the beating degree of any two pulps among the surface layer pulp, the bottom layer pulp, the core layer pulp and the lining layer pulp is less than or equal to 10°SR, which effectively solves the problem of delamination and blistering of the cardboard.

[0039] Preferably, in the pulping step,

[0040] The concentration of the filler is 15-20 wt %, and the viscosity is (2.0-4.0)×10 -2 Pa·S, pH value is 6-8, and the passing rate of 120 mesh screen is 95-100wt%;

[0041] The dry strength agent is one of polyacrylamide resin, polyvinyl alcohol, enzyme-modified starch, cationic starch and anionic starch, and the concentration of the dry strength agent is 12.5-20wt%.

[0042] Preferably, in the wet paper web forming step, the bottom layer wet paper web and the top layer wet paper web are both one layer, and the basis weights of the bottom layer wet paper web and the top layer wet paper web are both 15-30 g / m 2 The bottom lining layer wet paper web and the surface lining layer wet paper web are both 2 layers, and the core layer wet paper web is 3 layers. The quantitative weight of each layer of the bottom lining layer wet paper web, the surface lining layer wet paper web, and the core layer wet paper web is the same, and the error does not exceed 1.5%, which helps to obtain wet paper webs with similar physical properties and reduce the risks of delamination, bubbles, warping and deformation of the paperboard after compounding; the dryness of the paperboard wet paper web is 12-20wt%.

[0043] Preferably, in the pressing and dehydrating step, the working line pressures of the first lower vacuum pre-pressing, the upper vacuum pre-pressing, and the second lower vacuum pre-pressing are all 30-60 kN / m, the working line pressures of the vacuum positive pressure and the large roller vacuum positive pressure are all 60-120 kN / m, the working line pressure of the large roller diameter blind hole pressure is 100-160 kN / m, the working line pressures of the first stone roller smooth pressure and the second stone roller smooth pressure are all 60-120 kN / m, and the wet paper dryness of the paperboard after pressing and dehydrating is 40-60 wt%;

[0044] In the semi-dry pressing step, the working line pressures of the gloss drying cylinder and the lower pressing roller are both 30-80 kN / m, and the dryness of the paperboard web after semi-dry pressing is 70-80 wt%.

[0045] Preferably, after the pre-drying step, the dryness of the paperboard web is 85-92 wt %; after the post-drying step, the dryness of the paperboard web is 90-96 wt %.

[0046] Preferably, in the calendering step, the working line pressure of the calender is 30-80 kN / m, and the dryness of the paper web out of the calender is 90-96 wt%.

[0047] The beneficial effects of the present invention are:

[0048] 1. Strictly control the quality indicators of pulp and slurry in the pulping and pulping steps, and give the preferred range of pulp quality indicators and pulping ratio, control the difference in beating degree, which is helpful to improve the delamination and blistering of paperboard during the production process;

[0049] 2. The equipment and process of the steps of forming, pressing, drying, semi-dry pressing, etc. have been improved. A forming method of sequentially making and compounding multiple layers of wet paper webs is adopted to manufacture the raw materials into cardboard flat paper suitable for direct use by downstream factories at one time without the need for processing or modification in the intermediate process. Each layer of wet paper web is made by using basically the same papermaking equipment and papermaking process parameters to obtain wet paper webs with similar properties, and adhesives are used to strengthen the bonding force, so that the cardboard is not prone to delamination, blistering, warping, deformation, and difficulty in slitting. This not only improves the quality of the cardboard, but also facilitates the dehydration of the cardboard during the processes of forming, pressing, drying, etc., thereby reducing its energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is an equipment connection diagram for an embodiment of a papermaking machine.

[0051] Figure 2 Schematic diagram of an embodiment of a forming part.

[0052] Figure 3 A schematic diagram of an embodiment of a press section.

[0053] Figure 4 It is a schematic diagram of an embodiment of the front drying section.

[0054] Figure 5 Schematic diagram of an embodiment of a semi-dry press section.

[0055] Figure numerals: 10, forming section; 11, forming net; 12, former; 13, first press; 14, second press; 15, high-level box; 20, pressing section; 21, double-felt type press; 22, single-felt type press; 30, front drying section; 31, drying cylinder; 40, semi-dry pressing section; 50, rear drying section; 60, calender; 70, scanning device; 80, paper cutter. DETAILED DESCRIPTION

[0056] The following is a more detailed description of the embodiments of the present invention in conjunction with the accompanying drawings and the accompanying drawings so that a person skilled in the art can implement the embodiments after reading the description. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0057] Example 1

[0058] The present invention provides Figure 1-5 The multi-cylinder papermaking machine shown comprises a forming section 10, a pressing section 20, a front drying section 30, a semi-dry pressing section 40, a rear drying section 50, a calender 60, a scanning device 70 and a paper cutter 80 which are arranged in sequence.

[0059] The forming section 10 includes a plurality of formers 12, a first press 13, a second press 14 arranged in sequence along a forming net 11, and a plurality of high-level boxes 15 arranged above the plurality of formers 12, wherein the high-level boxes 15 are connected to the sizing pipes of the formers 12 through pipelines, the mounting bases of the plurality of formers 12 are lowered in sequence, and an adhesive nozzle is arranged between two adjacent formers 12.

[0060] Please refer to Figure 1 , 2 The multiple formers 12 include a first former 121, a second former 122, a third former 123, a fourth former 124, a fifth former 125, a sixth former 126, a seventh former 127, an eighth former 128, and a ninth former 129, which are arranged in sequence from right to left along the forming net 11. The above formers can all adopt the same type of round net formers. The mounting bases of the multiple formers are lowered in sequence from right to left, and the angle α between the connecting line of the multiple mounting bases and the horizontal plane is preferably about 15°. During the pulp dehydration and paperboard forming process, the wet paperboard and water are transferred from high to low, and the water is easier to remove. On the other hand, it is also to prevent water from flowing back to damage the pulp dehydration and the formed paper sheets.

[0061] Four high-level boxes 15 are also arranged above the multiple formers, including the first high-level box 151, the second high-level box 152, the third high-level box 153, and the fourth high-level box 154; the first high-level box 151 is connected to the sizing pipe of the first former 121 through a pipeline to provide the bottom layer slurry and make the bottom layer wet paper web; the second high-level box 152 is connected to the fourth, fifth, and sixth formers through pipelines to provide the core layer slurry and respectively make three layers of core layer wet paper webs; the third high-level box 153 is connected to the second, third, seventh, and eighth formers through pipelines to provide the lining layer slurry and respectively make two layers of bottom lining layer wet paper webs and two layers of surface lining layer wet paper webs; the fourth high-level box 154 is connected to the ninth former 129 through a pipeline to provide the surface layer slurry and make the surface layer wet paper web. According to the needs of the product, the first high-level box 151 and the fourth high-level box 154 can input different types of slurries to distinguish the surface layer and the bottom layer wet paper webs and produce different types of paperboards.

[0062] The same model of multiple formers and the same papermaking process parameters can be used to obtain bottom layer, bottom lining layer, core layer, surface lining layer, and surface layer wet paper webs with similar properties, which is helpful to prevent the paperboard from delamination, blistering, warping and deformation. The specific process is as follows:

[0063] The first former 121 filters the bottom slurry and forms a bottom wet paper web, which is hung on the forming wire 11 and moves forward, and the adhesive nozzle sprays the adhesive evenly on the surface of the bottom wet paper web;

[0064] The second former 122 drains the lining slurry and forms a first bottom lining wet paper web, which is then laminated on the bottom wet paper web moving along with the forming wire 11 and continues to move forward, and the adhesive nozzle sprays the adhesive evenly on the surface of the first lining wet paper web;

[0065] The third former 123 drains the lining slurry and forms a second bottom lining wet paper web, which is then laminated on the wet paper web moving along with the forming wire 11 and continues to move forward, and the adhesive nozzle sprays the adhesive evenly on the surface of the second lining wet paper web;

[0066] The fourth former 124 drains the core layer slurry and forms a first core layer wet paper web, and laminates it on the wet paper web moving along with the forming wire 11 and continues to move forward, and the adhesive nozzle sprays the adhesive evenly on the surface of the first core layer wet paper web;

[0067] The fifth former 125 drains the core layer slurry, forms a second core layer wet paper web, and laminates it on the wet paper web moving along with the forming wire 11 and continues to move forward, and the adhesive nozzle sprays the adhesive evenly on the surface of the second core layer wet paper web;

[0068] The sixth former 126 filters the core layer slurry and forms a third core layer wet paper web, and laminates it on the wet paper web moving along with the forming wire 11 and continues to move forward, and the adhesive nozzle sprays the adhesive evenly on the surface of the third core layer wet paper web;

[0069] The seventh former 127 drains the lining slurry and forms a first lining wet paper web, and laminates it on the wet paper web moving along with the forming wire 11 and continues to move forward, and the adhesive nozzle sprays the adhesive evenly on the surface of the first lining wet paper web;

[0070] The eighth former 128 drains the lining layer slurry, forms a second lining layer wet paper web, and laminates it on the wet paper web moving along with the forming wire 11 and continues to move forward, and the adhesive nozzle sprays the adhesive evenly on the surface of the second lining layer wet paper web;

[0071] The ninth former 129 filters the surface layer slurry and forms a surface layer wet paper web, and then composites it on the wet paper web moving along the forming wire 11 and continues to move forward to form a paperboard wet paper web, which then enters the first press 13 and the second press 14 in sequence for pressing and dehydration.

[0072] The first press 13 and the second press 14 can refer to the relevant technology, wherein the second press 14 is provided with three pairs of press rolls, the upper roll of the first pair of press rolls is a blind hole roll, and the lower roll is a vacuum roll, realizing the initial lower vacuum pre-pressing, the upper roll of the second pair of press rolls is a vacuum roll, and the lower roll is a blind hole roll, realizing the upper vacuum pre-pressing, and the upper roll of the third pair of press rolls is a blind hole roll, and the lower roll is a vacuum roll, realizing the secondary lower vacuum pre-pressing. After three pre-pressings, the free water of the wet paper web of the paperboard is squeezed out, and the water content in the wet paperboard is gradually squeezed to a saturated state.

[0073] The pressing section 20 includes a plurality of double-felt presses 21 and a plurality of single-felt presses 22 arranged in sequence. The upper roller of a pair of pressing rollers of the double-felt press 21 is a blind hole roller, and the lower roller is a vacuum roller; the upper roller of a pair of pressing rollers of the single-felt press 22 is a natural stone roller, and the lower roller is a flat rubber roller. Figure 1 , 3 , three double-felt presses 21 are arranged in sequence, which realize vacuum positive pressure, large-roll vacuum positive pressure, and large-roll blind hole pressure in sequence. As the pressure increases, the water pressure of the wet paper web and the felt gradually increases. Under the action of the pressure difference, the water is squeezed out; two single-felt presses 22 are arranged in sequence, which realize the first stone roller smooth pressure and the second stone roller smooth pressure in sequence to improve the surface flatness, smoothness and other surface properties of the paperboard. The pressing section and the forming section jointly complete eight pressing processes to improve the dryness of the wet paper web of the paperboard.

[0074] Please refer to Figure 1 , 4The front drying section 30 and the rear drying section 50 both include a plurality of drying cylinder groups arranged in sequence, and the drying cylinder groups include a plurality of drying cylinders 31 connected by a felt transmission. The drying cylinders 31 can refer to the relevant technology, and the drying cylinders 31 are heated by steam at a temperature of 130-170°C. The wet paper web of the paperboard is in direct contact with the drying cylinder to cause water evaporation and further remove water. In addition, under the high temperature environment, the adhesive produces a gelation reaction inside the paper web, thereby improving the internal bonding strength of the paperboard.

[0075] Please refer to Figure 1 , 5 The semi-dry pressing section 40 includes a semi-dry pressing machine, the upper roller of the semi-dry pressing machine is a heat-resistant rubber roller, and the lower roller is a gloss drying cylinder. Before the paperboard web enters the semi-dry pressing, the paperboard web is humidified with water mist by a spray nozzle, and then hot pressed by a pressing area composed of a gloss drying cylinder and a heat-resistant rubber roller, so as to improve the quality indexes such as the glossiness and tightness of the paper surface, and help improve the uniformity of moisture, and reduce the risk of problems such as warping, deformation, and difficulty in slitting.

[0076] The calender 60 , the scanning device 70 and the paper cutter 80 may all refer to related art.

[0077] Example 2

[0078] The present invention provides a papermaking method of a multi-cylinder paperboard papermaking machine for manufacturing 700g / m 2 The method comprises the following steps.

[0079] Step 1, pulping, preparing pulp, filler and dry strength agent, the pulp includes long fiber pulp, short fiber pulp, surface layer pulp, bottom layer pulp, lining layer pulp, core layer pulp and thermomechanical pulp. The preparation method and indexes of the above pulp, filler and dry strength agent are as follows.

[0080] Long fiber pulp and short fiber pulp: 20wt% of waste newsprint, 20wt% of office waste paper, 50wt% of waste book and magazine paper, and 10wt% of packaging waste paper are used as raw materials. After crushing, deslagging, desanding, screening, and grading, they are concentrated and refined respectively to obtain short fiber pulp and long fiber pulp; the short fiber pulp has a concentration of 3.5wt%, a beating degree of 45°SR, a fiber wet weight of 2.5g, and a pH value of 7.2; the long fiber pulp has a concentration of 3.5wt%, a beating degree of 25°SR, a fiber wet weight of 4.0g, and a pH value of 7.5.

[0081] Surface pulp: 50wt% recycled wood pulp residue and 50wt% recycled bamboo pulp residue are used as raw materials. The surface pulp is obtained through crushing, deslagging, desanding, screening, concentration and pulping. The concentration is 3.5wt%, the beating degree is 38°SR, the fiber wet weight is 3.5g and the pH value is 7.3.

[0082] Bottom pulp: 50wt% of waste book and magazine paper and 50wt% of packaging waste paper are used as raw materials. The bottom pulp is obtained by crushing, removing slag, removing sand, screening, concentrating and refining. The bottom pulp has a concentration of 3.5wt%, a beating degree of 38°SR, a fiber wet weight of 3.5g and a pH value of 7.4.

[0083] Lining pulp: 50wt% of mixed waste paper, 50wt% of waste paper boxes and waste cardboard are used as raw materials. The lining pulp is prepared through crushing, deslagging, desanding, screening, concentration and pulping. The concentration is 3.5wt%, the beating degree is 30°SR, the fiber wet weight is 3.2g, and the pH value is 7.5.

[0084] Core layer pulp: 50wt% of mixed waste paper, 50wt% of waste paper boxes and waste cardboard are used as raw materials. The core layer pulp is obtained by crushing, removing slag, removing sand, screening, concentrating and refining. The concentration is 3.5wt%, the beating degree is 30°SR, the fiber wet weight is 3.2g, and the pH value is 7.3.

[0085] Thermomechanical pulp: 50wt% of miscellaneous wood chips, 20wt% of waste building template chips, 20wt% of waste wood packaging box chips, and 10wt% of bamboo chips are used as raw materials. The wood chip treatment enzyme is evenly sprayed, mixed, fermented, preheated, refined, screened, deslagging, desanding, concentrated, and refined to obtain thermomechanical pulp with a concentration of 3.5wt%, a beating degree of 15°SR, a fiber wet weight of 4.2g, a pH value of 7.5, and a 40-mesh screen pass rate of 85wt%. The miscellaneous wood chips are agricultural and forestry residues; the wood chip treatment enzyme is one of pectinase, xylanase, cellulase, and hemicellulase, the enzyme dosage is 0.10wt%, the fermentation time is 4 days, and the fermentation temperature is 60°C.

[0086] Filler: 70wt% washed ball clay, 20wt% papermaking sludge, and 10wt% fly ash were mixed and crushed, deslagging, screening, and sand removal to obtain filler with a concentration of 18wt% and a viscosity of 3.0×10 -2 Pa·S, pH value is 7.8, and the pass rate of 120 mesh screen is 95wt%.

[0087] Dry strength agent: The dry strength agent is 12.5wt% polyacrylamide resin, which has the function of enhancing the bonding force between fibers, improving the tensile strength, bursting resistance, folding resistance and stiffness of the paperboard, and improving the physical properties of the paperboard.

[0088] Step 2: prepare the slurry.

[0089] The short fiber pulp, long fiber pulp, surface layer pulp, bottom layer pulp and dry strength agent are mixed in a mass ratio of 20:20:20:38:2 to prepare a surface layer pulp with a beating degree of 36°SR;

[0090] The short fiber pulp, long fiber pulp, surface layer pulp, bottom layer pulp and dry strength agent are mixed in a mass ratio of 20:20:20:38:2 to prepare a bottom layer pulp with a beating degree of 37°SR;

[0091] The core layer pulp, thermomechanical pulp, filler and dry strength agent are mixed in a mass ratio of 33:50:15:2 to obtain a core layer pulp with a beating degree of 26°SR;

[0092] The lining pulp, thermomechanical pulp, filler and dry strength agent are mixed in a mass ratio of 33:50:15:2 to prepare a lining pulp with a beating degree of 28°SR.

[0093] Step 3, forming. The bottom layer slurry, core layer slurry, lining layer slurry, and surface layer slurry are respectively input into the first, second, third, and fourth high-level boxes in Example 1, and multiple formers are used to respectively produce the bottom layer, the first bottom lining layer, the second bottom lining layer, the first core layer, the second core layer, the third core layer, the first surface lining layer, the second surface lining layer, and the surface layer wet paper webs, and adhesive is sprayed between each layer of wet paper webs, and the above-mentioned layers of wet paper webs are compounded from bottom to top to form a paperboard wet paper web. The compounding process can refer to Example 1. Among them, the bottom wet paper web has a basis weight of 20g / m 2 The first backing layer wet paper web weight is 95g / m 2 The second backing layer wet paper web weight is 94g / m 2 The first, second and third core layers of wet paper are all 94g / m 2 The first lining layer wet paper web weight is 94g / m 2 The second side lining wet paper web weight is 95g / m 2 , the surface wet paper weight is 20g / m 2 The final wet paper weight of the paperboard is 700g / m 2 , dryness is 18wt%.

[0094] Step 4, pressing. The formed paperboard wet paper web is pressed and dehydrated by the first press 13, the second press 14 and the pressing part 20. Specifically, the paperboard wet paper web is sequentially pressed by the first lower vacuum prepressing with a working line pressure of 40kN / m, the upper vacuum prepressing with a working line pressure of 45kN / m, the secondary lower vacuum prepressing with a working line pressure of 50kN / m, the vacuum positive pressure with a working line pressure of 70kN / m, the large roller vacuum positive pressure with a working line pressure of 80kN / m, the large roller diameter blind hole pressure with a working line pressure of 100kN / m, the first stone roller smooth pressure with a working line pressure of 80kN / m, and the first stone roller smooth pressure with a working line pressure of 80kN / m, a total of eight pressings, to remove the moisture of the paperboard wet paper web and improve the quality index of the paperboard wet paper web. After pressing, the dryness of the paperboard wet paper web is 48wt%.

[0095] Step 5, pre-drying. The drying cylinder 31 is heated by steam at a temperature of 130-170°C. The wet paper web of the paperboard is in direct contact with the drying cylinder to cause water evaporation and further remove water to form a paperboard web. In addition, under the high temperature environment, the adhesive produces a gelling reaction inside the paper web to improve the internal bonding strength of the paperboard. After the pre-drying is completed, the dryness of the paperboard web is 90wt%.

[0096] Step 6, semi-dry pressing. Before entering the semi-dry pressing, the paperboard web is humidified by water mist through a spray nozzle, and steam with a temperature of 130-170°C is introduced into the gloss drying cylinder for heating. The working line pressure of the gloss drying cylinder and the heat-resistant rubber roller is 60 kN / m, and hot pressing is performed in the pressing area composed of the gloss drying cylinder and the heat-resistant rubber roller. The dryness of the paperboard web leaving the semi-dry pressing section is 80wt%.

[0097] Step 7, post-drying: The drying cylinder is heated by steam at a temperature of 130-170°C. The paperboard web is in direct contact with the drying cylinder to cause water evaporation and further remove water. After the post-drying treatment, the dryness of the paperboard web is 93wt%.

[0098] Step 8: calendering: The paperboard web is calendered on a two-roll calender with a working line pressure of 60 kN / m to further improve the quality indicators such as gloss and tightness of the paper surface.

[0099] Step 9: Quality inspection: After the operator obtains the scanning inspection results of the paperboard web under the action of the QCS scanning device, he / she can adjust the operating parameters of steps 1 to 8 in time to ensure that the paperboard obtains the best quality performance.

[0100] Step 10, slitting: Slitting the paperboard web into qualified finished flat sheets.

[0101] Examples 3 and 4 respectively provide methods for producing a 1000 g / m 2 , 1500g / m 2 The papermaking method of the grey paperboard has the same specific steps as those in Example 2, but the process indicators are different, and the specific differences are shown in Tables 1 to 7.

[0102] Table 1: Comparison of raw material usage in pulping steps

[0103]

[0104] Table 2: Comparison of pulp indicators in pulping steps

[0105]

[0106] Table 3: Pulp ratios in the pulping step

[0107]

[0108] Table 4: Comparison of beating degree after pulp preparation

[0109]

[0110] Table 5: Wet paper web basis weight distribution in each layer during the forming step

[0111]

[0112] Table 6: Paper dryness control after each step

[0113]

[0114] Table 7: Working line pressure in pressing, semi-dry pressing and calendering steps

[0115]

[0116]

[0117] Comparative Example 1

[0118] The pulping and pulping steps are the same as those in Example 2, but the subsequent steps such as molding and pressing adopt the existing process to produce a 700g / m 2 Grey cardboard.

[0119] Comparative Example 2

[0120] The pulping steps were the same as those in Example 2, but different proportions were used in the pulping step, resulting in a large difference in the beating degree of each layer of pulp, as shown in Table 8. The subsequent steps such as molding and pressing were the same as those in Example 2, and a 700 g / m 2 Grey cardboard.

[0121] Table 8: Degree of beating of slurry in each layer of Comparative Example 2

[0122]

[0123] The grey paperboards produced in Examples 2-4 and Comparative Examples 1-2 were tested, and the testing method was based on GB / T4759-2014 Grey Paperboard. The test results are shown in Table 9. It can be seen that compared with Example 2, the internal bonding strength of Comparative Example 1 is significantly reduced, resulting in easy occurrence of delamination, blistering, warping and deformation, which shows that compared with the prior art, the molding, pressing and other process steps adopted by the present invention are helpful to solve the problem of inconsistent pulp properties between the paper webs of each layer of paperboard, and in fact, the probability of delamination, blistering, warping and deformation, and difficulty in slitting of the paperboard in the production process of Example 2 is significantly reduced; compared with Example 2, the internal bonding strength of Comparative Example 2 is reduced, but higher than that of Comparative Example 1, which shows that the present invention controls the beating degree of each layer of pulp in the pulping step within a reasonable range, which helps to improve the problems of delamination, blistering, warping and deformation, and difficulty in slitting of the paperboard.

[0124] Table 9: Grey paperboard index test results

[0125]

[0126] The above are one or more embodiments of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A multi-cylinder paperboard papermaking machine, comprising a forming section, a pressing section, a front drying section, a semi-dry pressing section, a rear drying section, a calender, a scanning device and a paper cutter arranged in sequence, characterized in that: The forming section comprises a plurality of formers, a first press, a second press, and a plurality of high-position boxes arranged in sequence along the forming net, wherein the high-position boxes are connected to the sizing pipes of the formers through pipelines; the mounting bases of the plurality of formers are lowered in sequence, and an adhesive nozzle is arranged between two adjacent formers; The pressing section comprises a plurality of double-felt presses and a plurality of single-felt presses arranged in sequence; the upper roll of the double-felt press is a blind hole roll, and the lower roll is a vacuum roll; the upper roll of the single-felt press is a natural stone roll, and the lower roll is a flat rubber roll; The front drying section and the rear drying section each include a plurality of drying cylinder groups arranged in sequence, and the drying cylinder group includes a plurality of drying cylinders connected by a felt transmission; The semi-dry pressing section comprises a semi-dry pressing machine, the upper roller of the semi-dry pressing machine is a heat-resistant rubber roller, and the lower roller is a gloss drying cylinder.

2. A papermaking method of a multi-cylinder paperboard papermaking machine, characterized in that: The following steps are involved: Pulping, preparing pulp, filler and dry strength agent, the pulp includes long fiber pulp, short fiber pulp, surface layer pulp, bottom layer pulp, lining layer pulp, core layer pulp and thermomechanical pulp; Mixing the pulp, mixing the short fiber pulp, the long fiber pulp, the surface layer pulp, the bottom layer pulp and the dry strength agent to obtain the surface layer pulp and the bottom layer pulp; mixing the core layer pulp, the thermomechanical pulp, the filler and the dry strength agent to obtain the core layer pulp; mixing the lining layer pulp, the thermomechanical pulp, the filler and the dry strength agent to obtain the lining layer pulp; Forming, conveying the bottom layer slurry, lining layer slurry, core layer slurry and surface layer slurry to the forming section, using the same papermaking equipment and papermaking process parameters to form a bottom layer wet paper web, a bottom lining layer wet paper web, a core layer wet paper web, a surface lining layer wet paper web and a surface layer wet paper web, spraying adhesive between the layers of wet paper webs and compounding them in sequence from bottom to top to form a paperboard wet paper web; Pressing, the wet paper web of the paperboard is dehydrated by first lower vacuum pre-pressing, upper vacuum pre-pressing, second lower vacuum pre-pressing, vacuum positive pressure, large roller vacuum positive pressure, large roller blind hole pressure, first stone roller smooth pressure, and second stone roller smooth pressure in sequence; Pre-drying: the wet paper web after pressing and dehydration is sent to the pre-drying section to further remove moisture to form a paper web; Semi-dry pressing, humidifying the paperboard web with water mist, and hot pressing through a pressing zone consisting of a gloss drying cylinder and a lower pressing roller; Post-drying: the paperboard web is sent to the post-drying section to remove moisture again; Calendering: sending the paperboard web into the calender for calendering; Quality inspection, scanning the paperboard web to obtain the inspection results, and adjusting the operating parameters of the previous steps to improve the quality of the paperboard web; Slitting: cutting the cardboard web into qualified finished flat paper.

3. The papermaking method of a multi-cylinder paperboard papermaking machine according to claim 2, characterized in that: In the pulping step, The concentration of the short fiber pulp, long fiber pulp, surface layer pulp and bottom layer pulp is 2.5-4.5wt%, the beating degree is 30-50°SR, the fiber wet weight is 2-5g, and the pH value is 6-8; The concentration of the lining layer pulp and the core layer pulp is 2.5-4.5wt%, the beating degree is 15-40°SR, the fiber wet weight is 2-5g, and the pH value is 6-8; The thermomechanical pulp has a concentration of 2.5-4.5 wt %, a beating degree of 8-20° SR, a fiber wet weight of 2-5 g, a pH value of 6-8, and a 40-mesh screen pass rate of 70-90 wt %.

4. The papermaking method of a multi-cylinder paperboard papermaking machine according to claim 3, characterized in that: In the pulping step, Using 10-20wt% of waste newsprint, 10-20wt% of office waste paper, 20-50wt% of waste book and magazine paper, and 10-60wt% of packaging waste paper as raw materials, after crushing, removing slag, removing sand, screening, and grading, and then concentrating and refining respectively, short fiber pulp and long fiber pulp are obtained; Using 40-60 wt% of recycled wood pulp residue and 40-60 wt% of recycled bamboo pulp residue as raw materials, a surface layer pulp is prepared; The bottom layer pulp is prepared by using 50-70wt% of waste book and magazine paper and 30-50wt% of packaging waste paper as raw materials; the lining layer pulp is prepared by using 50-70wt% of mixed waste paper and 30-50wt% of waste paper boxes and waste cardboard as raw materials; Using 50-70 wt% of mixed waste paper and 30-50 wt% of waste paper boxes and waste cardboard as raw materials to prepare core layer pulp; Thermomechanical pulp is prepared by using 50-70wt% of miscellaneous wood chips, 10-20wt% of waste building template chips, 10-20wt% of discarded wood packaging box chips and 10-20wt% of bamboo chips as raw materials, spraying wood chip treatment enzymes uniformly, mixing, fermenting, preheating, refining, screening, deslagging, desanding, concentrating and refining.

5. The papermaking method of a multi-cylinder paperboard papermaking machine according to claim 3, characterized in that: In the slurry preparation step, The short fiber pulp, the long fiber pulp, the surface layer pulp, the bottom layer pulp and the dry strength agent are mixed in a mass ratio of 10-25:10-25:5-25:25-60:0-5 to prepare the surface layer pulp; The short fiber pulp, the long fiber pulp, the surface layer pulp, the bottom layer pulp and the dry strength agent are mixed in a mass ratio of 10-25:10-25:5-25:25-60:0-5 to prepare the bottom layer pulp; The core layer pulp, the thermomechanical pulp, the filler and the dry strength agent are mixed in a mass ratio of 20-60:30-50:5-30:0-5 to prepare the core layer pulp; The lining slurry, the thermomechanical pulp, the filler and the dry strength agent are mixed in a mass ratio of 20-60:30-50:5-30:0-5 to prepare the lining slurry; After the slurry preparation is completed, the difference in beating degree of any two slurries among the surface layer slurry, the bottom layer slurry, the core layer slurry and the lining layer slurry is less than or equal to 10°SR.

6. The papermaking method of a multi-cylinder paperboard papermaking machine according to claim 5, characterized in that: In the pulping step, The concentration of the filler is 15-20 wt %, and the viscosity is (2.0-4.0)×10 -2 Pa·S, pH value is 6-8, and the passing rate of 120 mesh screen is 95-100wt%; The dry strength agent is one of polyacrylamide resin, polyvinyl alcohol, enzyme-modified starch, cationic starch and anionic starch, and the concentration of the dry strength agent is 12.5-20wt%.

7. The papermaking method of a multi-cylinder paperboard papermaking machine according to claim 2, characterized in that: In the wet paper web forming step, the bottom layer wet paper web and the surface layer wet paper web are both one layer, and the basis weight of the bottom layer wet paper web and the surface layer wet paper web is 15-30 g / m 2 The bottom lining layer wet paper web and the surface lining layer wet paper web are both 2 layers, the core layer wet paper web is 3 layers, and the quantity of each layer of the bottom lining layer wet paper web, the surface lining layer wet paper web, and the core layer wet paper web is the same; the dryness of the paperboard wet paper web is 12 to 20wt%.

8. The papermaking method of a multi-cylinder paperboard papermaking machine according to claim 2, characterized in that: In the pressing and dehydrating step, the working line pressures of the first lower vacuum pre-pressing, the upper vacuum pre-pressing, and the second lower vacuum pre-pressing are all 30-60 kN / m, the working line pressures of the vacuum positive pressure and the large roller vacuum positive pressure are all 60-120 kN / m, the working line pressure of the large roller diameter blind hole pressure is 100-160 kN / m, the working line pressures of the first stone roller smooth pressure and the second stone roller smooth pressure are all 60-120 kN / m, and the wet paper dryness of the paperboard after pressing and dehydration is 40-60 wt%; In the semi-dry pressing step, the working line pressures of the gloss drying cylinder and the lower pressing roller are both 30-80 kN / m, and the dryness of the paperboard web after semi-dry pressing is 70-80 wt%.

9. The papermaking method of a multi-cylinder paperboard papermaking machine according to claim 2, characterized in that: After the pre-drying step, the dryness of the paperboard web is 85-92wt%; after the post-drying step, the dryness of the paperboard web is 90-96wt%.

10. The papermaking method of a multi-cylinder paperboard papermaking machine according to claim 2, characterized in that: In the calendering step, the working line pressure of the calender is 30-80 kN / m, and the dryness of the paper web out of the calender is 90-96 wt%.

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