A paper-based material for prefabricated liquid packaging box and its preparation method and application

Abstract

The present invention belongs to the field of papermaking technology, and provides a paper-based material for a prefabricated liquid packaging box, and a preparation method and application thereof. The present invention prepares a surface layer slurry, a lining layer slurry, a core layer slurry, and a bottom layer slurry respectively, and then performs papermaking to obtain a paper-based material for a prefabricated liquid packaging box comprising a surface layer, a lining layer, a core layer, and a bottom layer stacked in sequence, wherein each layer of the present invention adopts a specific slurry and its ratio, controls the pulp-to-net speed ratio of each layer, and controls the broken paper beating degree of the core layer, so that the paper achieves the core layering of the base paper on the basis of meeting the requirements of high internal bonding strength and low Z-direction strength, and the structure of each layer is uniform, which is further used to prepare a prefabricated liquid packaging box, and can meet the requirements of embossing and filling.

Description

Technical Field

[0001] The present invention relates to the technical field of papermaking, and more specifically to a paper-based material for a prefabricated liquid packaging box, and a preparation method and application thereof. Background Art

[0002] In recent years, with the development of coating technology and composite materials, the anti-permeability and mechanical strength of liquid packaging paper have been significantly improved, which can better meet the needs of various liquid packaging. Liquid packaging paper is mainly obtained by printing, laminating, creasing, and slitting paper rolls, which are packaged and then transported to the filling plant to be made into boxes for liquid filling. Due to the large size of the coil and its easy damage, the coil needs to be packaged before transportation to avoid damage to the coil during transportation, which increases the difficulty of transportation and reduces the convenience of using the coil. Therefore, a prefabricated liquid packaging box is specially designed. The prefabricated liquid packaging box refers to a packaging box made of paper-based materials that has been processed and formed and can be directly used to fill liquids after laminating, printing, creasing and die-cutting. It can be directly packed and transported to the filling plant for filling and processing. It combines the convenience of prefabricated boxes with the advantages of printability and processing of paper-based materials and is widely used. However, the paper-based material for prefabricated liquid packaging boxes needs to be printed and embossed first, and cracks are prone to appear at the embossing points. The paper-based material is not strong enough, which makes the assembled packaging boxes unstable and lacks structural support, making it difficult to fill liquids, and it is also difficult to stack the packaging boxes together and transport them to the filling plant. Therefore, the current paper-based materials for prefabricated liquid packaging boxes have the problems of insufficient strength and embossing forming performance.

[0003] Therefore, there is an urgent need to develop a paper-based material for prefabricated liquid packaging boxes that can be embossed and not prone to cracks and has high strength, and the prefabricated liquid packaging boxes made therefrom can meet the requirements of stacking, transportation and filling. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a paper-based material for a prefabricated liquid packaging box and a preparation method and application thereof. The natural color paper-based material provided by the present invention has high internal bonding strength and low Z-direction strength (internal bonding strength up to 193 J / m 2 , Z-axis strength is as low as 360kPa), achieving stratification of the base paper core, and uniform structure of each layer, which is further used to prepare prefabricated liquid packaging boxes, can meet the requirements of indentation forming and filling, is easy to indent and form without cracks, and the packaging boxes assembled after indentation forming have a firm structure and can be well filled, carried liquid and stacked for transportation.

[0005] A first aspect of the present invention provides a paper-based material for a prefabricated liquid packaging box.

[0006] Specifically, a method for preparing a paper-based material for a prefabricated liquid packaging box, wherein the paper-based material for a prefabricated liquid packaging box comprises a surface layer, a lining layer, a core layer and a bottom layer stacked in sequence, and the preparation method comprises the following steps:

[0007] Prepare surface layer slurry, lining layer slurry, core layer slurry and bottom layer slurry respectively, and then carry out papermaking to obtain the paper-based material for the prefabricated liquid packaging box;

[0008] The raw materials for preparing the surface layer pulp include, by mass percentage, 60-85% long fiber wood pulp and 15-40% short fiber wood pulp;

[0009] The raw materials for preparing the lining pulp include, by mass percentage, 60-85% long fiber wood pulp and 15-40% short fiber wood pulp;

[0010] The raw materials for preparing the core layer pulp include, by mass percentage, 45-55% chemical mechanical pulp, 15-25% long fiber wood pulp and 20-40% broken paper;

[0011] During the papermaking process, the pulp-to-web speed ratio of the surface layer is 0.960-0.980, and / or the pulp-to-web speed ratio of the lining layer is 0.960-0.980, and / or the pulp-to-web speed ratio of the core layer is 0.975-0.990, and / or the pulp-to-web speed ratio of the bottom layer is 0.965-0.990;

[0012] The core layer broke has a beating degree of 30-45 SR°.

[0013] In the indentation forming performance of paper-based materials, the internal bonding strength, Z-direction strength and indentation forming performance interact with each other, which has a great influence on the mechanical properties of paper-based materials. In particular, when used as packaging materials, the performances of these three are interrelated and jointly determine the overall structural stability and application performance of the paper-based materials. Specifically, if the internal bonding strength is too low, the folding structure after indentation will be unstable or lack structural support. The present invention helps the packaging box assembled by the paper-based material to maintain a stable shape by improving the internal bonding strength. At the same time, low Z-direction strength helps indentation forming, specifically: 1. Reduce the forming force: the strength of the paperboard in the Z direction (along the thickness direction) is low, which means that it is easier to deform in this direction, reducing the pressure required for the processing process; 2. Increase the indentation depth: During the indentation process of the paperboard, if the Z-direction strength is low, the paperboard can flow more easily along the Z direction, so that the indentation forming depth can be increased, reducing the possibility of cracking or uneven deformation of the paperboard; 3. Improve the local deformation ability of the paperboard: low Z-direction strength means that the deformation ability of the paperboard in the thickness direction is strong, which is particularly important for the forming of complex shapes. During the forming process, especially in the local indentation or depression area, low Z-strength can make the paperboard adapt to local deformation more easily, avoiding cracks or uneven deformation caused by stress concentration. However, too high Z-strength may cause the paper-based material to be too hard, making indentation forming difficult, and even causing cracks at the indentation. Therefore, for paper-based materials for liquid packaging, having high internal bonding strength and low internal bonding strength is crucial to meet the indentation forming and filling performance and subsequent use as different packaging materials. Therefore, in the process of producing and preparing paper-based materials, the present invention mainly changes the fiber arrangement direction of each layer of paper-based materials by adjusting the type and ratio of each layer of slurry, controlling the pulp-to-net speed ratio of each layer during the papermaking process (to achieve control of fiber arrangement on the paper machine), and the pulping degree of the core layer, so as to simultaneously adjust the internal bonding strength and Z-strength to achieve the goal of core-to-core stratification of the paper-based material, so as to meet the requirements of subsequent indentation forming and filling performance.

[0014] The pulp-to-wire speed ratio refers to the ratio between the flow rate of the pulp and the wire speed of the paper machine.

[0015] Core-to-core delamination means: in the internal bonding strength and Z-direction strength tests, the performance of separation between the layers of the paper-based material is observed. If the peeling is separated from the core layer, it is core-to-core delamination, indicating that the interlayer fiber distribution of the paper-based material is uniform. The uniform fiber distribution between the surface layer, lining layer, core layer and bottom layer has obvious benefits for the indentation forming and filling performance of the paper-based material. For indentation forming, core-to-core delamination can improve the deformation uniformity and compression resistance of the paper, and it is not easy to crack or damage during the indentation process. In addition, the uniform interlayer fiber distribution can also improve the surface smoothness of the paper-based material and avoid local uneven thickness. For filling performance, uniform fiber distribution helps the paper maintain structural stability when affected by liquid. Paper with uniform fiber distribution can reduce deformation when in contact with liquid, maintain better mechanical properties and physical stability, and enhance anti-permeability during the filling process.

[0016] Internal bonding strength refers to the bonding strength between the layers of paper-based materials.

[0017] Z-direction strength refers to the tensile and compressive resistance of the paper-based material in the direction perpendicular to its surface.

[0018] Preferably, the long fiber wood pulp includes at least one of bleached coniferous wood sulfate pulp, unbleached coniferous wood sulfate pulp, and semi-bleached coniferous wood sulfate pulp, and / or the short fiber wood pulp includes at least one of bleached broadleaf sulfate pulp, bleached chemithermomechanical pulp, unbleached broadleaf sulfate pulp, and semi-bleached broadleaf sulfate pulp, and / or the chemimechanical pulp (chemimechanical pulp) is bleached chemithermomechanical pulp.

[0019] Preferably, the raw materials for preparing the surface layer pulp include, by mass percentage, 60-85% bleached coniferous wood kraft pulp and 15-40% bleached broadleaf wood kraft pulp; and / or, by mass percentage, the raw materials for preparing the lining layer pulp include, by mass percentage, 60-85% bleached coniferous wood kraft pulp and 15-40% bleached broadleaf wood kraft pulp; and / or, by mass percentage, the raw materials for preparing the core layer pulp include, by mass percentage, 45-55% bleached chemical-thermomechanical pulp, 15-25% bleached coniferous wood kraft pulp and 20-40% broken paper.

[0020] Further preferably, calculated by mass percentage, the raw materials for preparing the surface layer pulp include: 70-85% bleached coniferous wood sulfate pulp and 15-25% bleached hardwood sulfate pulp; and / or, calculated by mass percentage, the raw materials for preparing the lining layer pulp include: 70-85% bleached coniferous wood sulfate pulp and 15-25% bleached hardwood sulfate pulp; and / or, calculated by mass percentage, the raw materials for preparing the core layer pulp include: 45-50% bleached chemical thermomechanical pulp, 20-25% bleached coniferous wood sulfate pulp and 30-40% broken paper.

[0021] Preferably, the pulp-to-web speed ratio of the surface layer is 0.965-0.980, and / or the pulp-to-web speed ratio of the lining layer is 0.965-0.980, and / or the pulp-to-web speed ratio of the core layer is 0.975-0.985, and / or the pulp-to-web speed ratio of the bottom layer is 0.965-0.985.

[0022] Preferably, in terms of mass percentage, the raw materials for preparing the bottom layer pulp include: 100% coniferous natural kraft pulp (NUKP). The bottom layer of the present invention adopts NUKP, which, on the one hand, reduces the production cost, and the product is degradable, recyclable, and green and environmentally friendly. On the other hand, it can make the paper-based material meet the strength requirements for the paper-based material during the indentation process. The raw material of NUKP is coniferous wood, and it has not been bleached to destroy the original structure of the fiber. The fibers are longer and the connectivity between the fibers is stronger. Therefore, the bottom layer of the paper-based material made of 100% NUKP has higher tensile strength, tear resistance and compression resistance. When used for liquid packaging, the high-strength bottom layer can effectively prevent the damage and leakage of the packaging box. In addition, NUKP also helps to reduce the warping and deformation of the paper-based material, which is particularly important when the paper-based material for liquid packaging needs to withstand greater pressure.

[0023] Preferably, the core layer has a broke degree of 35-40 SR°.

[0024] Further preferably, the broken paper beating degree of the core layer is 39-40SR°.

[0025] Preferably, the method for preparing the slurry includes crushing, screening, beating and mixing the raw materials for preparing the slurries of the surface layer, lining layer, core layer and bottom layer, respectively, to prepare the surface layer slurry, lining layer slurry, core layer slurry and bottom layer slurry, respectively.

[0026] Preferably, the surface layer slurry, the lining layer slurry, the core layer slurry and the bottom layer slurry all contain cationic starch and a reactive sizing agent.

[0027] Preferably, the reactive sizing agent is an alkyl ketene dimer sizing agent (AKD).

[0028] Preferably, the papermaking comprises filtering water, compounding, pressing, drying, surface sizing, coating and drying again of each layer of slurry in sequence to obtain the paper-based material for the prefabricated liquid packaging box.

[0029] Preferably, the surface sizing uses starch as a sizing agent.

[0030] Preferably, the coating used for the surface coating comprises the following raw material components: china clay, calcined clay, 95 grade calcium carbonate and latex.

[0031] Further preferably, the coating material used for the top coating layer comprises, by weight, 10-20 parts of china clay, 5-15 parts of calcined clay, 70-80 parts of calcium carbonate, and 10-20 parts of latex.

[0032] More preferably, the coating material used for the top coating layer comprises, by weight, 15-20 parts of china clay, 10-15 parts of calcined clay, 75-80 parts of grade 95 calcium carbonate, and 15-20 parts of latex.

[0033] Preferably, the coating used for coating the core layer and the bottom layer comprises the following raw material components: 50 grade calcium carbonate and latex.

[0034] Further preferably, the coating used for coating the core layer and the bottom layer comprises the following raw material components, measured in parts by weight: 90-110 parts of grade 50 calcium carbonate and 10-20 parts of latex.

[0035] More preferably, the coating used for coating the core layer and the bottom layer comprises the following raw material components, measured in parts by weight: 100-110 parts of grade 50 calcium carbonate and 13-15 parts of latex.

[0036] A second aspect of the present invention provides a paper-based material for a prefabricated liquid packaging box.

[0037] A paper-based material for a prefabricated liquid packaging box, prepared by the above-mentioned preparation method, wherein the internal bonding strength of the paper-based material for a prefabricated liquid packaging box is ≥193 J / m 2 , and / or, the Z-direction strength of the paper-based material for the prefabricated liquid packaging box is ≤360 kPa.

[0038] A third aspect of the present invention provides an application of a paper-based material for a prefabricated liquid packaging box.

[0039] The invention discloses an application of a paper-based material for a prefabricated liquid packaging box in the preparation of liquid packaging materials.

[0040] A fourth aspect of the present invention provides a prefabricated liquid packaging box.

[0041] A prefabricated liquid packaging box is made of a paper-based material for the prefabricated liquid packaging box.

[0042] A fifth aspect of the present invention provides a method for preparing a prefabricated liquid packaging box.

[0043] A method for preparing a prefabricated liquid packaging box comprises the following steps:

[0044] The prefabricated liquid packaging box is printed, laminated, embossed and cut using a paper-based material to obtain the prefabricated liquid packaging box.

[0045] Preferably, the gap of the indentation process is 1.2-2 times the thickness of the paper-based material, and / or the pressure of the indentation process is 5-8 KN.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] The present invention prepares surface layer slurry, lining layer slurry, core layer slurry and bottom layer slurry respectively, and then carries out papermaking to obtain a paper-based material for a prefabricated liquid packaging box which is sequentially stacked with a surface layer, a lining layer, a core layer and a bottom layer, wherein each layer of the present invention adopts a specific slurry and its ratio, controls the pulp-to-net speed ratio of each layer, and controls the broken paper beating degree of the core layer, so that the paper achieves core stratification of the base paper on the basis of meeting the requirements of high internal bonding strength and low Z-direction strength, and each layer has a uniform structure, which is further used for preparing a prefabricated liquid packaging box, can meet the requirements of embossing, filling and transportation, can be stacked and placed, and can be transported to a filling plant for direct filling processing of liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a schematic diagram of the structure of each layer of the paper-based material for the prefabricated liquid packaging box according to Example 1 of the present invention;

[0049] Figure 2 These are the folding curves of the paper-based materials of Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0050] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0051] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0052] Unless otherwise specified, the parts referred to in the present invention are parts by mass; the percentages referred to are percentages by mass.

[0053] The raw materials involved in the present invention are:

[0054] NBKP: Bleached softwood kraft pulp (long fiber pulp), manufacturer Celulosa Arauco Y Constitucion S.A. Chile, brand Silver Star.

[0055] LBKP: bleached hardwood kraft pulp (short fiber pulp), manufacturer SUZANO INTERNATIONAL TRADE GMBH., brand Parrot.

[0056] BCTMP: bleached chemical thermomechanical pulp, a mixture of wood pulp A (manufacturer Rayonier AM Canada G.P., brand Tempura maple) and wood pulp B (manufacturer Millar Western Forest Products Ltd. Canada, brand Crystal needle) in a mass ratio of 1:1.

[0057] NUKP: Unbleached softwood kraft pulp (long fiber pulp), manufacturer Celulosa Arauco Y Constitucion S.A. Chile, brand Venus.

[0058] Example 1

[0059] A method for preparing a paper-based material for a prefabricated liquid packaging box, wherein the paper-based material for the prefabricated liquid packaging box comprises a surface layer, a lining layer, a core layer and a bottom layer stacked in sequence, and the preparation method comprises the following steps:

[0060] 1. Preparation of slurry for each layer

[0061] (1) Surface layer: The pulp is crushed by a hydraulic pulper, screened, pulped, mixed, and finally papered on a paper feeder;

[0062] Among them, according to the mass percentage, the raw materials for preparing the surface layer pulp include: 60% NBKP (bleached softwood kraft pulp) + 40% LBKP (bleached hardwood kraft pulp);

[0063] Surface beating degree: NBKP: 23SR°; LBKP: 26SR°;

[0064] (2) Lining layer: After the pulp is crushed by the hydraulic pulper, it is screened, pulped by disc grinding, mixed, and finally papered by the paper feeder;

[0065] Wherein, according to the mass percentage, the raw materials for preparing the lining pulp include: 60% NBKP (bleached softwood kraft pulp) + 40% LBKP (bleached hardwood kraft pulp);

[0066] Lining beating degree: NBKP: 23SR°; LBKP: 26SR°;

[0067] (3) Core layer: The pulp is crushed by a hydraulic pulper, screened, pulped, mixed, and finally papered on a paper feeder;

[0068] The raw materials for preparing the core layer pulp include, by mass percentage: 45% BCTMP (bleached chemical thermomechanical pulp) + 25% NBKP + 30% broken paper;

[0069] Core layer beating degree: BCTMP: 18SR°; NBKP: 22SR°; Broken paper: 40SR°;

[0070] (4) Bottom layer: The pulp is crushed by a hydraulic pulper, then screened, pulped, mixed, and finally papered on a paper machine;

[0071] The raw materials for preparing the bottom pulp include, by mass percentage: 100% NUKP (unbleached softwood kraft pulp), beating degree: 21SR°;

[0072] The addition amount of other preparation raw materials in each layer is:

[0073] (a) Cationic starch (manufacturer: Zhongqing Fengtai, model: FOP-501) added in the surface, lining, core and bottom layers: 3, 3, 2 and 3 kg / ton pulp; added in the pulp preparation process of each layer;

[0074] (b) AKD sizing agent (alkyl ketene dimer sizing agent) in the surface, lining, core and bottom layers: 18, 18, 20, 18 kg / ton of slurry; all added during the slurry preparation process of each layer;

[0075] The broken paper used above: the paper edges cut from the rewinding of Hongta brand 200gsm natural liquid packaging paper and defective products with quality problems are used as raw materials for broken paper, which are put into the broken paper system, and are successively crushed, screened and pulped by a hydraulic pulper, and the beating degree is controlled at 40SR°, so as to obtain broken paper that can be added to the core layer.

[0076] 2. Paper machine section

[0077] ① Web: After filtering the above four layers of pulp, spray starch between the surface lining, lining core and core bottom, and add 3, 5 and 16 kg / ton pulp respectively; then compound, wherein the pulp web speed ratio of each layer is shown in Table 1 below;

[0078] ② Pressing;

[0079] ③ Drying: temperature 110℃, time 50 seconds;

[0080] ④ Surface sizing: The upper and lower rollers are coated with starch for sizing. The surface sizing amount is 4g / m 2 ;

[0081] ⑤ Coating: Each layer is coated with coating separately, among which the back coating uses BGT metering rod, and the surface, core and bottom coatings use TL scraper; the coating formula is:

[0082] The coating used for the topcoat includes: 15 parts of china clay, 10 parts of calcined clay, 75 parts of 95-grade calcium carbonate, and 15 parts of latex (styrene-acrylic latex);

[0083] The coating used for the core and primer layers includes: 100 parts of 50-grade calcium carbonate and 13 parts of latex (styrene acrylic latex);

[0084] Back coating: starch;

[0085] ⑥ Drying: temperature 150℃, time 23 seconds;

[0086] ⑦ Coiling, rewinding, packaging and storage.

[0087] The structure of the paper-based material for the prefabricated liquid packaging box prepared in Example 1 is as follows: Figure 1 As shown, it includes a stacked surface layer (mainly made of bleached chemical long fibers and bleached chemical short fibers), a lining layer (mainly made of bleached chemical long fibers and bleached chemical short fibers), a core layer (mainly made of bleached chemical long fibers and chemical-mechanical pulp) and a bottom layer (mainly made of unbleached chemical long fibers).

[0088] Waste paper or unqualified defective products generated in the preparation process of the paper-based material for the prefabricated liquid packaging box prepared in Example 1 can also be recycled as a raw material for broken paper and put into a broken paper system, and are successively crushed, screened, and beaten by a hydraulic pulper with a beating degree of 40 SR° to obtain broken paper that can be added to the core layer.

[0089] Example 2

[0090] A method for preparing a paper-based material for a prefabricated liquid packaging box, which differs from Example 1 in that the slurry ratios of the surface, lining, and core layer are different, specifically:

[0091] According to the percentage by mass, the raw materials for preparing the surface layer pulp include: 80% NBKP (bleached softwood kraft pulp) + 20% LBKP (bleached hardwood kraft pulp);

[0092] The raw materials for preparing the lining pulp include, by mass percentage: 80% NBKP (bleached softwood kraft pulp) + 20% LBKP (bleached hardwood kraft pulp);

[0093] Calculated by mass percentage, the raw materials for preparing the core layer pulp include: 55% BCTMP (bleached chemical thermomechanical pulp) + 25% NBKP + 20% broken paper.

[0094] Example 3

[0095] A method for preparing a paper-based material for a prefabricated liquid packaging box, which is different from Example 1 in that the beating degrees of the surface, lining and core layer pulps are different, specifically:

[0096] Surface beating degree: NBKP: 30SR°; LBKP: 30SR°;

[0097] Lining beating degree: NBKP: 30SR°; LBKP: 30SR°.

[0098] Core layer beating degree: BCTMP: 25SR°; NBKP: 30SR°; Broken paper: 45SR°.

[0099] Comparative Example 1

[0100] A method for preparing a paper-based material for a prefabricated liquid packaging box is different from Example 1 in that the pulp-to-web speed ratio is adjusted, as shown in Table 1 below.

[0101] Table 1 Pulp-to-net speed ratio of Example 1 and Comparative Example 1

[0102] Example 1 Comparative Example 1 Surface 0.970 0.955 lining 0.970 0.955 Core layer 0.980 0.970 Bottom Layer 0.970 0.960

[0103] Comparative Example 2

[0104] A method for preparing a paper-based material for a prefabricated liquid packaging box, which is different from Example 1 in that the pulping degree of the core layer broken paper is reduced to 28SR°.

[0105] Comparative Example 3

[0106] A method for preparing a paper-based material for a prefabricated liquid packaging box, which is different from Example 1 in that the pulping degree of the core layer broken paper is increased to 46SR°.

[0107] Product effect testing

[0108] 1. Folding curve

[0109] Paper is cut, embossed, and folded to obtain a prefabricated liquid packaging box with a certain spatial structure. If the embossing performance of the paper-based material is poor, it will lead to problems such as difficulty in embossing, and even cracks will appear at the embossing. In the subsequent folding process, the folding may break or crack, the crease is uneven, and the printed pattern or text is unclear at the folding, thereby increasing the scrap rate and other problems, and ultimately affecting the subsequent application of the paper-based product (such as the performance of the packaging box for liquid packaging and transportation of liquid). Since there is no industry-wide unified indicator for the embossing performance of paper at present, the present invention uses a "folding curve" to compare the embossing performance of each paper. The specific method is as follows: cut a 170mm×200mm sample, use an L&W bending stiffness tester, adjust the bending angle to 15°, clamp a section of the sample, and after starting the test, the paper sample will bend to 90°, record the bending angle and the corresponding folding force during the bending to 90° process, and draw a graph based on the data to obtain a folding curve (where the horizontal axis is the folding angle and the vertical axis is the folding force). The folding curve is used to judge the indentation forming performance. The lower the peak value of the folding curve, the better the indentation forming performance.

[0110] The folding curves of the papers obtained in Example 1 and Comparative Example 1 are as follows: Figure 2 As shown in the figure, it can be seen that Example 1 has more excellent indentation forming performance, indicating that the present invention adjusts the pulp-to-web speed ratio of each layer so that the indentation forming performance of the paper-based material can meet the requirements for preparing prefabricated liquid packaging boxes.

[0111] 2. Internal bonding strength, Z-direction strength

[0112] Internal bonding strength: "GB / T 26203-2023 Paper and paper-based materials" Determination of internal bonding strength (Scott type).

[0113] Z-direction strength: "GB / T 31110-2014 Paper and paper-based materials" Determination of Z-direction tensile strength.

[0114] The broken paper beating degree, internal bonding strength and Z-direction strength of the core layer of Example 1, Comparative Example 2 and Comparative Example 3 are shown in the following table.

[0115] Table 2 Internal bonding strength and Z-direction strength of each embodiment and comparative example

[0116] Example 1 Comparative Example 2 Comparative Example 3 Core Broken Paper Beating Degree 40SR° 28SR° 46SR° <![CDATA[Internal bond strength (J / m 2 )]]> 193 175 185 Z-direction strength (kPa) 360 370 438

[0117] As can be seen from the table above, in Example 1, by controlling the core layer broke degree to 40SR°, the internal bonding strength is 193 J / m 2 , Z-axis strength is 360kPa, which is conducive to indentation forming.

[0118] The overall bleached coniferous wood kraft pulp content of the paper base material of Example 2 is higher than that of Example 1, and the indentation forming performance is slightly worse than that of Example 1; the overall beating degree of Example 3 is higher than that of Example 1, and the internal bonding strength of the obtained paper base material is excellent, but the Z-direction strength is higher than that of Example 1.

[0119] The core layer broken paper of Comparative Example 2 has a low beating degree, resulting in low internal bonding strength; the core layer broken paper of Comparative Example 3 has a high beating degree, resulting in excessively high Z-direction strength, both of which are not conducive to the control of the subsequent indentation forming performance of the paper base material.

Claims

1. A method for preparing a paper-based material for a prefabricated liquid packaging box, characterized in that: The paper-based material for the prefabricated liquid packaging box comprises a surface layer, a lining layer, a core layer and a bottom layer which are stacked in sequence, and the preparation method comprises the following steps: Prepare surface layer slurry, lining layer slurry, core layer slurry and bottom layer slurry respectively, and then carry out papermaking to obtain the paper-based material for the prefabricated liquid packaging box; The raw materials for preparing the surface layer pulp include, by mass percentage, 60-85% long fiber wood pulp and 15-40% short fiber wood pulp; The raw materials for preparing the lining pulp include, by mass percentage, 60-85% long fiber wood pulp and 15-40% short fiber wood pulp; The raw materials for preparing the core layer pulp include, by mass percentage, 45-55% chemical mechanical pulp, 15-25% long fiber wood pulp and 20-40% broken paper; During the papermaking process, the pulp-to-web speed ratio of the surface layer is 0.960-0.980, and / or the pulp-to-web speed ratio of the lining layer is 0.960-0.980, and / or the pulp-to-web speed ratio of the core layer is 0.975-0.990, and / or the pulp-to-web speed ratio of the bottom layer is 0.965-0.990; The core layer broke has a beating degree of 30-45 SR°.

2. The preparation method according to claim 1, characterized in that: The long fiber wood pulp includes at least one of bleached softwood kraft pulp, unbleached softwood kraft pulp, and semi-bleached softwood kraft pulp, and / or the short fiber wood pulp includes at least one of bleached hardwood kraft pulp, bleached chemical thermomechanical pulp, unbleached hardwood kraft pulp, and semi-bleached hardwood kraft pulp, and / or the chemical mechanical pulp is bleached chemical thermomechanical pulp.

3. The preparation method according to claim 2, characterized in that: The raw materials for preparing the surface layer pulp include, by mass percentage, 60-85% bleached coniferous wood sulfate pulp and 15-40% bleached broadleaf wood sulfate pulp; and / or, by mass percentage, the raw materials for preparing the lining layer pulp include, by mass percentage, 60-85% bleached coniferous wood sulfate pulp and 15-40% bleached broadleaf wood sulfate pulp; and / or, by mass percentage, the raw materials for preparing the core layer pulp include, by mass percentage, 45-55% bleached chemical thermomechanical pulp, 15-25% bleached coniferous wood sulfate pulp and 20-40% broken paper.

4. The preparation method according to claim 1, characterized in that: The pulp-to-web speed ratio of the surface layer is 0.965-0.980, and / or the pulp-to-web speed ratio of the lining layer is 0.965-0.980, and / or the pulp-to-web speed ratio of the core layer is 0.975-0.985, and / or the pulp-to-web speed ratio of the bottom layer is 0.965-0.

985.

5. The preparation method according to claim 1, characterized in that: The core layer broke has a beating degree of 35-40SR°.

6. The preparation method according to claim 1, characterized in that: The slurry preparation method comprises crushing, screening, beating and mixing the raw materials for preparing the slurries of the surface layer, lining layer, core layer and bottom layer respectively, so as to prepare the surface layer slurry, lining layer slurry, core layer slurry and bottom layer slurry respectively.

7. The preparation method according to claim 1, characterized in that: The papermaking comprises filtering water, compounding, pressing, drying, surface sizing, coating and drying again of each layer of slurry in sequence to obtain the paper-based material for the prefabricated liquid packaging box.

8. A paper-based material for a prefabricated liquid packaging box, characterized in that: The paper-based material for the prefabricated liquid packaging box is prepared by the preparation method according to any one of claims 1 to 7, and the internal bonding strength of the paper-based material for the prefabricated liquid packaging box is ≥ 193 J / m 2 , and / or, the Z-direction strength of the paper-based material for the prefabricated liquid packaging box is ≤360 kPa.

9. Use of the paper-based material for prefabricated liquid packaging boxes according to claim 8 in preparing liquid packaging materials.

10. A prefabricated liquid packaging box, characterized in that: The prefabricated liquid packaging box according to claim 8 is made of paper-based material.

11. The method for preparing the prefabricated liquid packaging box according to claim 10, characterized in that: The steps include: The paper-based material for the prefabricated liquid packaging box of claim 9 is sequentially subjected to printing, lamination, creasing and slitting to obtain the prefabricated liquid packaging box.

12. The preparation method according to claim 11, characterized in that: The gap of the indentation process is 1.2-2 times of the thickness of the paper-based material, and / or the pressure of the indentation process is 5-8 KN.

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