Cardboard paper and preparation method thereof

Abstract

The invention belongs to the technical field of papermaking, and particularly relates to cardboard paper and a preparation method thereof. The cardboard paper is prepared from the following raw material components: slurry, polyaluminum chloride, a dry strength agent, a multifunctional additive, a GCC wrapping agent and a surface sizing agent. The preparation method of the cardboard paper comprises the following steps: preparing pulp from bamboo fibers and waste paper fibers, wherein the pulp is divided into surface pulp, core pulp and bottom pulp; sequentially and respectively adding polyaluminum chloride, a dry strength agent and a GCC wrapping agent into the surface pulp, the core pulp and the bottom pulp, stirring and uniformly mixing; then adding the multifunctional additive into the core pulp and the bottom pulp, stirring and uniformly mixing; the surface pulp, the core pulp and the bottom pulp are respectively screened out to obtain accepted pulp, and the accepted pulp is sequentially subjected to the procedures of net feeding, squeezing, pre-baking, surface sizing, post-baking, press polishing and curling to obtain the product. The method can meet the requirements of production indexes, and solves the problems of poor national waste quality, shortage of American waste raw materials and high production cost.

Description

Technical Field

[0001] This invention belongs to the field of papermaking technology, specifically relating to a type of corrugated paper and its preparation method. Background Technology

[0002] As a core category of packaging paper, corrugated board is widely used in transportation packaging, commodity packaging and other scenarios. Its mechanical properties (bursting strength, tensile strength, folding strength, etc.) and production costs directly determine the application adaptability and economic benefits in the packaging industry.

[0003] To address the raw material shortage caused by reduced imports of waste paper, papermaking technology has begun seeking new alternatives. In actual production, there is a shortage of US waste paper (#12 and #13), key raw materials for high-grade packaging paper. Adding wood pulp to domestic waste paper for high-grade packaging paper production increases costs, and excessive wood pulp can negatively impact the production process. To alleviate the raw material shortage, the industry has experimented with adding wood pulp to domestic waste paper for high-grade linerboard production. However, the high price of wood pulp significantly increases production costs; furthermore, excessive wood pulp alters the pulp's drainage properties and forming characteristics, disrupting the stability of the original production process and causing a series of production problems.

[0004] Bamboo fiber, as a renewable biomass resource, possesses natural advantages such as moderate fiber length, high mechanical strength, wide availability, and low price, making it an ideal raw material to replace some waste paper or wood pulp in the production of linerboard. However, when bamboo fiber is mixed with domestic waste paper for pulping, traditional processes struggle to address the core issues of poor fiber bonding and low efficiency of additives, resulting in significant fluctuations in the mechanical properties of the finished linerboard and failing to meet the requirements of high-end packaging. Furthermore, the additive systems commonly used in existing linerboard production lack specificity and are difficult to adapt to the composite pulp system of bamboo fiber and waste paper fiber, further limiting the large-scale application of bamboo fiber in linerboard production.

[0005] Therefore, developing a technical solution that uses bamboo fiber and waste paper fiber as the main raw materials, optimizes the raw material ratio, auxiliary agent system and production process, can solve the industry pain points of shortage of American waste paper and poor quality of domestic waste paper, and can also ensure the mechanical properties of linerboard and reduce production costs, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a linerboard and its preparation method. Bamboo fiber is used to replace the previously used American waste paper. The pulp is obtained through processes such as mixing and dissolving domestic waste paper. Through raw material formulation and production processes, the required production indicators can be met, solving the problems of poor quality domestic waste paper and the shortage and high production costs of American waste paper.

[0007] To achieve the above-mentioned objectives of this invention, the specific technical solution adopted by this invention is as follows: A type of linerboard, the raw materials of which include the following components: pulp, polyaluminum chloride, dry strength agent, multifunctional additive, GCC coating agent and surface sizing agent.

[0008] Preferably, the pulp consists of surface pulp, core pulp, and bottom pulp, with a mass ratio of 2-3:3-4:3.5-4.5; the raw materials for the pulp are bamboo fiber and waste paper fiber, with a mass ratio of 0.8-1.5:8.5-9.2. This ratio can fully utilize the advantages of high strength of bamboo fiber and low cost of waste paper fiber, achieving a balance between performance and cost.

[0009] Preferably, the polyaluminum chloride contains 10-20% alumina, 0-0.20% insoluble matter, 40.0-85.0% basicity, has a density of 1.12-2.50 g / cm³ at 20°C, a pH of 3.5-5.0 in a 1% aqueous solution, and a mass ratio of 10-15 kg / t to linerboard. Its function is to adjust the pH of the pulp system to a suitable range, initially neutralize the negative charge on the fiber surface, promote the aggregation of fine fibers and fillers, and create conditions for the effective adsorption and action of subsequent functional additives.

[0010] Preferably, the dry strength agent is a modified amphoteric cationic multi-component network polyacrylamide polymer with a viscosity-average molecular weight of 1 million to 3 million, a solid content of 14% to 16%, a pH value of 3.5 to 5.5, and a viscosity of 3000 to 9000 mPa·s at 25°C.

[0011] More preferably, the mass ratio of the dry strength agent to the linerboard is 30-50 kg / t, and the ratio of the dry strength agent added to the top pulp, core pulp, and bottom pulp is 0-5:15-20:15-25. This dry strength agent has both anionic and cationic groups on its molecular chain, enabling it to strongly adsorb ions onto fibers, fine fibers, and other ionic substances in the system. During the drying process, it further enhances the bonding between fibers through hydrogen bonds, thereby significantly improving the dry strength of the paper. Simultaneously, it plays a good role in retention and filtration in the wire section.

[0012] Preferably, the multifunctional additive is a modified amphoteric polyacrylamide biopolymer solution with a viscosity-average molecular weight of 1-2 million, a solid content of 18-21%, and a density of 1.03-1.08 g / cm³ at 25°C. 3The pH value is 4.0-6.0, and the viscosity at 25℃ using a #1 rotor at 60 r / min is 0-50 mPa·s. The mass ratio of the multifunctional additive to the produced linerboard is 5-10 kg / t. No multifunctional additive is added to the face pulp, and the ratio of the multifunctional additive added to the core pulp and bottom pulp is 1.5-4.5:3.5-5.5. This multifunctional additive can further improve the cohesive force between fibers, particularly helping to improve the strength of the wet paper sheet and reduce the risk of paper breakage in the press section; at the same time, by balancing the system charge, it optimizes the water filtration and retention performance during the papermaking process, improving the operating efficiency of the paper machine.

[0013] Preferably, the GCC encapsulating agent is prepared by mixing calcium carbonate encapsulating agent (mass ratio 2:4:1), anionic polyacrylamide (number average relative molecular weight ≥7 million), and triethylhexylphosphoric acid, and then diluting with water at a mass ratio of 1:150.

[0014] More preferably, the mass ratios of GCC encapsulating agent in the face pulp, core pulp, and bottom pulp to the produced linerboard are 3-15, 0.01-15, and 0.01-15 kg / t, respectively. Its function is to effectively encapsulate fine particles such as calcium carbonate (GCC) filler in the pulp through a polymer network, enhancing their bonding with fibers, reducing loss, and helping to improve the stiffness, opacity, and surface smoothness of the finished paper.

[0015] Preferably, the surface sizing agent is composed of a cationic styrene-acrylate copolymer and starch in a mass ratio of 1:10; the styrene-acrylate copolymer has a solid content of 29-31%, a pH value of 1.0-4.0, and a viscosity of 10-50 mPa·s at 25°C using a #1 rotor at 60 r / min; the mass ratio of the styrene-acrylate copolymer to the linerboard is 1.0-2.0 kg / t; the starch is selected from one or both of virgin corn starch and cassava starch, with a moisture content of 6-14%, a dry basis starch acidity of 0-1.8°T, and a fineness of 95-99%; the mass ratio of the starch to the linerboard is 10-20 kg / t, and the ratio of starch in the front sizing amount to the back sizing amount is 4-8:6-12, the starch concentration is 9-12%, and the viscosity is 20-35 mPa·s. This sizing system can improve the surface strength and water resistance of paper.

[0016] This invention also relates to a method for preparing the above-mentioned corrugated paperboard, comprising the following steps: (1) Bamboo fiber and waste paper fiber are made into pulp, and the pulp is divided into surface pulp, core pulp and bottom pulp; (2) Add polyaluminum chloride, dry strength agent and GCC coating agent to the top slurry, core slurry and bottom slurry in sequence, stir and mix evenly; (3) Then add the multifunctional additive to the core slurry and the bottom slurry, stir and mix evenly; (4) Select good pulp from the surface pulp, core pulp and bottom pulp respectively, and then process them in sequence through the following steps: netting, pressing, pre-drying, surface sizing, post-drying, calendering and curling.

[0017] Preferably, the pulping process in step (1) involves breaking down, screening and purifying bamboo fiber and waste paper fiber, thermally dispersing and refining them to produce pulp.

[0018] More preferably, the fragmentation concentration is 3-6%, the fragmentation time is 30-40 min; the thermal dispersion temperature is 90-100℃, the dispersion time is 3-10 min; the pulping concentration is 4-6%, the surface pulping degree is 35-45SR, and the core pulp and bottom pulping degree is 30-40SR.

[0019] Preferably, in step (2), the stirring speed is 300-500 r / min, the mixing time is 15-25 min, and the mixing temperature is 40-50℃; in step (3), the stirring speed is 200-400 r / min, the mixing time is 10-20 min, and the mixing temperature is 40-50℃; in step (4), the sieve size for screening good pulp is 100-120 mesh, the pre-drying temperature is 100-120℃, and the post-drying temperature is 110-130℃.

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention uses bamboo fiber to replace American waste or part of wood pulp and combines it with domestic waste to prepare pulp. This solves the problems of American waste shortage and poor quality of domestic waste, and also reduces production costs (the cost of bamboo fiber raw materials is only 60-70% of that of wood pulp). At the same time, the high strength characteristics of bamboo fiber provide a foundation for improving the mechanical properties of linerboard.

[0021] (2) The present invention has designed a composite additive system of “polyaluminum chloride + dry strength agent + GCC coating agent + multifunctional additive + surface sizing agent”. The additives work together to improve the bonding between bamboo fiber and waste paper fiber, and also improve the pulp’s water filtration and retention properties, as well as the paper’s dry strength and surface properties, thus solving the problem of poor compatibility of traditional additives. Attached Figure Description

[0022] Figure 1 This is a flowchart of the cardboard box manufacturing process. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments. The following embodiments are not intended to limit the present invention, but only to illustrate the present invention. Unless otherwise specified, the experimental methods used in the following embodiments are generally performed under conventional conditions. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0024] Polyaluminum chloride, purchased from Ma'anshan Jianding Chemical Co., Ltd., has an alumina mass fraction ≥10%, a basicity of 50.0-85.0%, an insoluble content of 0-0.20%, a density of 1.12-2.50 g / cm3 at 20℃, and a pH value of 3.5-5.0 for a 1% aqueous solution.

[0025] The dry strength agent (a modified amphoteric cationic multi-component network polymer based on PAM) was purchased from Zhejiang Chuanhua Huayang Chemical Co., Ltd., model: Chuanhua DS-1502A. Its viscosity-average molecular weight is 1 million-3 million, solid content is 14-16%, pH value is 3.5-5.5, and viscosity at 25℃ is 3000-9000 mPa·s.

[0026] The multifunctional additive (a solution of amphoteric biopolymer modified with PAM as the main component) was purchased from Nanjing Shipei Environmental Protection Technology Co., Ltd., model: LEES FUNCTION 300C, with a pH value (1% aqueous solution, 25℃) of 2.0-5.0 and a viscosity (25℃) of 3000-13000 mPa·s.

[0027] Calcium carbonate encapsulating agent, purchased from Shanghai Kuasui Industrial Co., Ltd., model: Kuasui SC413.

[0028] Anionic polyacrylamide, purchased from Shandong Nuoer Biotechnology Co., Ltd., model: polyacrylamide / anionic, with a solid content (%) ≥ 88 and a number-average relative molecular weight ≥ 7 million.

[0029] The cationic styrene-acrylate copolymer emulsion, purchased from Dongguan Yuanxiang Biotechnology Co., Ltd., model: Yuanxiang B20, has a solid content (%) of 30±2 and a viscosity (25℃, 1# rotor, 60r / min) of mpa·s≤100.

[0030] Corn / cassava starch, purchased from Nanjing State Farms Industry (Group) Co., Ltd., with a fineness % (100 mesh) ≥ 98.5%, acidity (dry basis °T) ≤ 1.8, and moisture content of 6-14%.

[0031] Example 1 1. A type of corrugated cardboard, the raw materials of which are as follows: Pulp: 100kg bamboo fiber and 900kg waste paper fiber, to make 250kg surface pulp, 350kg core pulp and 400kg bottom pulp (mass ratio 2.5:3.5:4.0).

[0032] Polyaluminum chloride: 12kg, of which 4kg are used for the top dressing, core dressing and bottom dressing.

[0033] Dry strength agent (modified amphoteric cationic multi-component network polymer mainly composed of PAM (polyacrylamide): 40 kg, including 3 kg of top dressing, 18 kg of core dressing, and 19 kg of bottom dressing (ratio 3:18:19).

[0034] Multifunctional additive (amphoteric biopolymer solution modified mainly with PAM): 8 kg, including 3 kg of core slurry and 5 kg of bottom slurry (ratio 3:5).

[0035] GCC encapsulation agent: It is a compound of calcium carbonate encapsulation agent, anionic polyacrylamide and reagent-grade triethylhexyl phosphate in a mass ratio of 2:4:1. When using, dilute it with water at a mass ratio of 1:150 and stir well.

[0036] The coating agent content of the top layer, core layer, and bottom layer slurries is as follows: 10 kg for the top layer, 8 kg for the core layer, and 8 kg for the bottom layer.

[0037] Surface sizing agent: 1.5 kg of cationic styrene-acrylate copolymer emulsion and 15 kg of cassava starch; the sizing agent is prepared by mixing the above cationic styrene-acrylate copolymer emulsion with the gelatinized starch, with 6 kg of front-side surface sizing starch and 9 kg of back-side surface sizing starch (ratio 6:9), the starch gelatinization concentration is 10.0±0.5%, and the paste viscosity is 24-26 mPa·s (25℃).

[0038] 2. The above-mentioned process flow chart for preparing linerboard is as follows: Figure 1 As shown, the specific steps are as follows: (1) Pulp preparation: Bamboo fiber and waste paper fiber are mixed and crushed by a high-consistency pulper (concentration 5%, time 35min), screened and purified by pressure screen and slag remover, hot dispersed at 95℃ for 6min, and refined by a double disc refiner (concentration 5%, surface pulp refinement degree 40°SR, core pulp and bottom pulp refinement degree 35°SR). After the pulp is made, it is divided into surface pulp, core pulp and bottom pulp. (2) First stage of additive addition: Add polyaluminum chloride, dry strength agent and GCC coating agent to the corresponding slurry in sequence, and stir at 350 r / min and 45℃ for 20 min; (3) Second stage of additive addition: Add the multifunctional additive to the core slurry and bottom slurry, and stir at 300 r / min and 45℃ for 15 min; (4) Forming and post-processing: The pulp is screened through a 110-mesh screen, fed onto a wire paper machine (concentration 1.0%), pressed by three rollers (pressure 0.7MPa), pre-drying (110℃, moisture 18%), film transfer sizing (65℃), post-drying (120℃, moisture 7%), hard calendering (0.35MPa), and rolled to obtain the finished product.

[0039] Example 2 1. A type of corrugated cardboard, the raw materials of which are as follows: Pulp: 80kg bamboo fiber and 920kg waste paper fiber, made into 220kg surface pulp, 380kg core pulp and 400kg bottom pulp (mass ratio 2.2:3.8:4.0).

[0040] Polyaluminum chloride: 10kg, of which the amount of top dressing, core dressing and bottom dressing is 3.3kg each.

[0041] Dry strength agent: 35kg, including 2kg top dressing, 15kg core dressing, and 18kg bottom dressing (ratio 2:15:18).

[0042] Multifunctional additive: 6kg, including 2kg core slurry and 4kg bottom slurry (ratio 2:4).

[0043] GCC encapsulation agent: It is a compound of calcium carbonate encapsulation agent, anionic polyacrylamide and reagent-grade triethylhexyl phosphate in a mass ratio of 2:4:1. When using, dilute it with water at a mass ratio of 1:150 and stir well.

[0044] The GCC coating agent content of the top layer, core layer, and bottom layer slurries is 8 kg for the top layer, 5 kg for the core layer, and 5 kg for the bottom layer, respectively.

[0045] Surface sizing agent: 1.2 kg cationic styrene-acrylate copolymer emulsion, 12 kg corn starch; the sizing agent is prepared by mixing the above cationic styrene-acrylate copolymer emulsion with the gelatinized starch, with 5 kg of front-side surface sizing starch and 7 kg of back-side surface sizing starch (ratio 5:7), the starch gelatinization concentration is 9.0±0.5%, and the paste viscosity is 22-24 mPa·s (25℃).

[0046] 2. The preparation method of the above-mentioned corrugated board is as follows: (1) Pulp preparation: Bamboo fiber and waste paper fiber are mixed and crushed by a high-consistency pulper (4% concentration, 30 min time), screened and purified by pressure screen and slag remover, hot dispersed at 90℃ for 10 min, and refined by a double disc refiner (4% concentration, surface pulp refinement degree 35°SR, core pulp and bottom pulp refinement degree 30°SR). After the pulp is made, it is divided into surface pulp, core pulp and bottom pulp. (2) First stage of additive addition: Add polyaluminum chloride, dry strength agent and GCC coating agent to the corresponding slurry in sequence, and stir at 300 r / min and 40℃ for 25 min; (3) Second stage of additive addition: Add multifunctional additives to core slurry and bottom slurry, and stir at 200 r / min and 40℃ for 20 min; (4) Forming and post-processing: 100-mesh screen is used to screen good pulp, which is then fed onto a wire paper machine (concentration 0.8%), pressed by three rollers (pressure 0.6MPa), pre-drying (100℃, moisture 20%), film transfer sizing (60℃), post-drying (110℃, moisture 8%), hard calendering (0.3MPa), and curled to obtain the finished product.

[0047] Example 3 1. A type of corrugated cardboard, the raw materials of which are as follows: Pulp: 120kg bamboo fiber and 880kg waste paper fiber, made into 280kg surface pulp, 320kg core pulp and 400kg bottom pulp (mass ratio 2.8:3.2:4.0).

[0048] Polyaluminum chloride: 15kg, of which 5kg are used for the top dressing, core dressing and bottom dressing.

[0049] Dry strength agent: 48kg, including 4kg top dressing, 20kg core dressing, and 24kg bottom dressing (ratio 4:20:24).

[0050] Multifunctional additive: 9kg, including 4kg core slurry and 5kg bottom slurry (ratio 4:5).

[0051] GCC encapsulation agent: It is a compound of calcium carbonate encapsulation agent, anionic polyacrylamide and reagent-grade triethylhexyl phosphate in a mass ratio of 2:4:1. When using, dilute it with water at a mass ratio of 1:150 and stir well.

[0052] The GCC coating agent content of the top layer, core layer and bottom layer slurries is 12 kg for the top layer, 12 kg for the core layer and 12 kg for the bottom layer, respectively.

[0053] Surface sizing agent: 1.8 kg cationic styrene-acrylate copolymer emulsion, 18 kg corn starch and cassava starch (1:1); the sizing agent is prepared by mixing the above cationic styrene-acrylate copolymer emulsion with the gelatinized starch, with 7 kg of front-side surface sizing starch and 11 kg of back-side surface sizing starch (ratio 7:11), the starch gelatinization concentration is 12.0±0.5%, and the paste viscosity is 30-32 mPa·s (25℃).

[0054] 2. The preparation method of the above-mentioned corrugated board is as follows: (1) Pulp preparation: Bamboo fiber and waste paper fiber are mixed and crushed by a high-consistency pulper (6% concentration, 40 min time), screened and purified by pressure screen and slag remover, hot dispersed at 100℃ for 3 min, and refined by a double disc refiner (6% concentration, surface pulp refinement degree 45°SR, core pulp and bottom pulp refinement degree 40°SR). After the pulp is made, it is divided into surface pulp, core pulp and bottom pulp. (2) First stage of additive addition: Add polyaluminum chloride, dry strength agent and GCC coating agent to the corresponding slurry in sequence, and stir at 500 r / min and 50℃ for 15 min; (3) Second stage of additive addition: Add multifunctional additives to core slurry and bottom slurry, and stir at 400 r / min and 50℃ for 10 min; (4) Forming and post-processing: Screen the good pulp with a 120-mesh screen, put it on the wire paper machine (concentration 1.2%), press it with three rollers (pressure 0.8MPa), pre-dry (120℃, moisture 15%), film transfer sizing (70℃), post-dry (130℃, moisture 6%), hard calender (0.4MPa), and curl it to obtain the finished product.

[0055] Comparative Example 1 The difference between this comparative example and Example 1 is that the pulp raw material is 1000 kg of domestic waste (without bamboo fiber), while the proportions and preparation methods of the other raw materials are the same as in Example 1.

[0056] Comparative Example 2 The only difference between this comparative example and Example 1 is that the total amount of polyaluminum chloride (PAC) added is reduced to 5 kg / t of oven-dry paper (equal amounts added to each layer). All other raw materials, proportions, and processes are exactly the same.

[0057] Comparative Example 3 The only difference between this comparative example and Example 1 is that the dry strength agent used is replaced with conventional anionic polyacrylamide (model: APAM-50, viscosity-average molecular weight of 450,000-550,000, solid content ≥89%), which is added after being converted to the commercial dosage at the same dry weight addition amount (40 kg / t) as the dry strength agent in Example 1. All other raw materials, proportions and processes are exactly the same.

[0058] Comparative Example 4 The only difference between this comparative example and Example 1 is that the multifunctional additive LEES FUNCTION 300C is not added. All other raw materials, proportions, and processes are exactly the same.

[0059] Comparative Example 5 The only difference between this comparative example and Example 1 is that the GCC encapsulating agent used is only anionic polyacrylamide, and the three-component compound system described in this invention is not employed. Its total dry weight is equivalent to the total dry weight of the three-layer GCC encapsulating agent compound in Example 1 (20 kg / t), and it is distributed among the three layers in the same proportion. All other raw materials, proportions, and processes are completely identical.

[0060] Comparative Example 6 The only difference between this comparative example and Example 1 is that the oven-dry mass ratio of cationic styrene-acrylate copolymer emulsion (Yuanxiang B20) to cassava starch in the surface sizing agent is adjusted to 1:5. All other raw materials, proportions, and processes are exactly the same.

[0061] Effect test The linerboard prepared in Examples 1-3 and Comparative Examples 1-6 above (basis weight of 130±4 g / m²) 2 Key mechanical properties were tested, and the results are recorded in Table 1 below.

[0062] Test standards: bursting strength refers to GB / T 6545-1998, tensile strength refers to GB / T 12914-2018, flexural endurance refers to GB / T 457-2008, and surface smoothness refers to GB / T 456-2002; Ash content: Refer to GB / T 742-2018 "Determination of ash content in papermaking raw materials, pulp, paper and paperboard", ignite at 575±25℃ to constant weight.

[0063] Table 1 Test Results

[0064] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A containerboard, characterized in that, The raw material of the boxboard includes the following components: pulp, polyaluminum chloride, dry strength agent, multifunctional additive, GCC coating agent and surface sizing agent; The pulp is composed of face pulp, core pulp and bottom pulp with a mass ratio of 2-3:3-4:3.5-4.5, the raw material of the pulp includes bamboo fiber and waste paper fiber, and the mass ratio of the bamboo fiber and the waste paper fiber is 0.8-1.5:8.5-9.

2.

2. The containerboard according to claim 1, characterized in that The polyaluminum chloride contains 10-20% of alumina, 0-0.20% of insoluble substance, 40.0-85.0% of salt base, and has a density of 1.12-2.50 g / cm at 20℃ 3 The pH value of 1% polyaluminum chloride aqueous solution is 3.5-5.

0.

3. The containerboard as claimed in claim 1, characterized in that The mass ratio of the polyaluminum chloride to the boxboard is 10-15 kg / t, and the adding amount of the polyaluminum chloride in the face pulp, the core pulp and the bottom pulp is 3.3-5.0 kg / t.

4. The containerboard as claimed in claim 1, characterized in that The dry strength agent is modified amphoteric partial positive multi-component network polyacrylamide polymer with a viscosity average molecular weight of 1-3 million, a solid content of 14-16%, a pH value of 3.5-5.5 and a viscosity of 3000-9000 mpa·s at 25℃; And / or, the mass ratio of the dry strength agent to the produced boxboard is 30-50 kg / t, and the adding amount ratio of the dry strength agent in the face pulp, the core pulp and the bottom pulp is 0-5:15-20:15-25.

5. The containerboard as claimed in claim 1, characterized in that The multifunctional additive is modified amphoteric polyacrylamide biopolymer solution with a viscosity average molecular weight of 1-2 million, a solid content of 18-21%, a density of 1.03-1.08 g / cm³ at 25℃, a pH value of 4.0-6.0 at 25℃ and a viscosity of 0-50 mpa·s at 25℃ using a 1# rotor at 60 r / min; And / or, the mass ratio of the multifunctional additive to the boxboard is 5-10 kg / t, no multifunctional additive is added in the face pulp, and the adding amount ratio of the multifunctional additive in the core pulp and the bottom pulp is 1.5-4.5:3.5-5.

5.

6. The containerboard as claimed in claim 1, characterized in that The GCC coating agent includes calcium carbonate coating agent, anionic polyacrylamide and triethylhexyl phosphate, and the number average relative molecular weight of the anionic polyacrylamide is ≧7 million; And / or, the preparation of the GCC coating agent includes compounding the calcium carbonate coating agent, the anionic polyacrylamide and the triethylhexyl phosphate with a mass ratio of 2:4:1, and then diluting with water 145-155 times the total mass of the calcium carbonate coating agent, the anionic polyacrylamide and the triethylhexyl phosphate to obtain the GCC coating agent; And / or, the mass ratio of the GCC coating agent in the face pulp, the core pulp and the bottom pulp to the produced boxboard is 3-15, 0.01-15 and 0.01-15 kg / t, respectively.

7. The containerboard as claimed in claim 1, characterized in that The surface sizing agent includes cationic styrene-acrylate copolymer and starch with a mass ratio of 1:10; And / or, the solid content of the cationic styrene-acrylate copolymer is 29-31%, the pH value is 1.0-4.0, the viscosity is 10-50 mpa·s at 25℃ using a 1# rotor at 60 r / min, and the mass ratio of the styrene-acrylate copolymer to the produced boxboard is 1.0-2.0 kg / t. And / or, the starch is selected from one or both of native corn and cassava starch, the starch having a moisture content of 6-14%, a dry basis starch acidity of 0-1.8 °T, a fineness of 95-99%, and a mass ratio of the starch to the produced boxboard paper of 10-20 kg / t, wherein the ratio of the amount of starch in the front surface sizing amount to the back surface sizing amount is 4-8:6-12; the starch has a feeding concentration of 9-12 wt% and a viscosity of 20-35 mpa·s.

8. A method of producing the containerboard according to any one of claims 1 to 7, characterized by The method comprises the following steps: (1) preparing a slurry from bamboo fibers and waste paper fibers, and dividing the slurry into face pulp, core pulp and bottom pulp; (2) adding polyaluminum chloride, dry strength agent and GCC coating agent into the face pulp, core pulp and bottom pulp in sequence, stirring and mixing uniformly; (3) then adding a multifunctional additive into the core pulp and bottom pulp, stirring and mixing uniformly; (4) screening the face pulp, core pulp and bottom pulp to obtain good pulp, and sequentially performing the processes of netting, pressing, pre-drying, surface sizing, post-drying, polishing and curling to obtain the product.

9. The method of making a boxboard according to claim 8, characterized in that, In step (1), the operation of preparing the slurry is performed after the bamboo fibers and waste paper fibers are subjected to disintegration, screening and purification, heat dispersion and grinding treatment; the disintegration concentration is 3-6%, the disintegration time is 30-40 min; the heat dispersion temperature is 90-100 °C, and the dispersion time is 3-10 min; the grinding concentration is 4-6%, the face pulp grinding consistency is 35-45 SR, and the core pulp and bottom pulp grinding consistencies are 30-40 SR.

10. The method of making a boxboard according to claim 8, characterized in that, In step (2), the stirring speed is 300-500 r / min, the mixing time is 15-25 min, and the mixing temperature is 40-50 °C; in step (3), the stirring speed is 200-400 r / min, the mixing time is 10-20 min, and the mixing temperature is 40-50 °C; in step (4), the screening mesh number for screening the good pulp is 100-120 mesh, the pre-drying temperature is 100-120 °C, and the post-drying temperature is 110-130 °C.

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