Paper Jam

Abstract

The present application discloses a paperboard. The paperboard includes a bottom layer, a core layer, a lining layer and a surface layer stacked in sequence. The core layer is made of core layer pulp, and the composition of the core layer pulp includes 10-30% of core layer coniferous pulp, 30-50% of first core layer broadleaf pulp and 20-40% of second core layer broadleaf pulp. Among them, the freeness range of the core layer coniferous pulp is 280ml-320ml, the freeness range of the first core layer broadleaf pulp is 380ml-420ml, and the freeness range of the second core layer broadleaf pulp is 200ml-270ml. Through the above method, the paperboard of the present application has high comprehensive performance.

Description

Technical Field

[0001] The present application relates to the technical field of papermaking, and in particular to a paperboard. Background Art

[0002] In recent years, with the popularity of domestic table games and card games, the quality and performance requirements for cardboard are getting higher and higher. And with the emergence of players' demand for game experience and collection, the requirements for the comprehensive performance of cardboard are still rising. In the related technology, the original copperplate cardboard was used to make cards. The stiffness and durability of the existing copperplate cardboard are insufficient, and the comprehensive performance of the existing cardboard cannot meet the needs of players. Summary of the invention

[0003] The embodiments of the present application provide a cardboard having high comprehensive performance.

[0004] The embodiment of the present application provides a cardboard. The cardboard includes a bottom layer, a core layer, a lining layer and a surface layer stacked in sequence. The core layer is made of core layer pulp, and the composition of the core layer pulp includes 10-30% of core layer coniferous pulp, 30-70% of first core layer broadleaf pulp and 20-40% of second core layer broadleaf pulp. Among them, the freeness range of the core layer coniferous pulp is 280mL-320mL, the freeness range of the first core layer broadleaf pulp is 380mL-420mL, and the freeness range of the second core layer broadleaf pulp is 200mL-270mL.

[0005] Optionally, the surface lining is made of surface lining slurry, and the surface lining slurry comprises 20-30% of surface lining coniferous pulp, 30-60% of first surface lining broadleaf pulp, and 20-40% of second surface lining broadleaf pulp;

[0006] The freeness of the coniferous pulp of the surface lining layer is in the range of 280mL-320mL, the freeness of the broadleaf pulp of the first surface lining layer is in the range of 380mL-420mL, the freeness of the broadleaf pulp of the second surface lining layer is in the range of 200mL-270mL, the freeness of the second core layer broadleaf pulp is lower than the freeness of the first core layer broadleaf pulp, and the second core layer broadleaf pulp with low freeness is added to the core layer pulp;

[0007] Optionally, the surface layer is made of surface layer pulp, and the surface layer pulp comprises 20-40% of surface layer conifer pulp and 60-80% of surface layer broadleaf pulp;

[0008] Among them, the freeness range of the surface layer softwood pulp is 250-320mL, and the freeness range of the surface layer broadleaf pulp is 350mL-450mL;

[0009] Optionally, the bottom layer is made of bottom layer pulp, and the bottom layer pulp comprises 20-30% of bottom layer conifer pulp, 30-80% of first bottom layer broadleaf pulp, and 0-40% of second bottom layer broadleaf pulp;

[0010] Among them, the freeness range of the bottom layer of coniferous pulp is 280mL-320mL, the freeness range of the first bottom layer of broadleaf pulp is 380mL-420mL, and the freeness range of the second bottom layer of broadleaf pulp is 200mL-270mL;

[0011] Optionally, the amount of the reinforcing drug in the surface layer, the surface lining layer and the bottom layer is less than or equal to 1%; the amount of the reinforcing drug in the core layer is less than or equal to 3% and greater than or equal to 0.5%;

[0012] Optionally, starch is sprayed between the lining layer and the core layer, and the amount of starch is greater than or equal to 0.5 gsm and less than or equal to 4.5 gsm; starch is sprayed between the bottom layer and the core layer, and the amount of starch is greater than or equal to 0.5 gsm and less than or equal to 4.5 gsm;

[0013] Optionally, the total basis weight of the bottom layer, the core layer, the facing layer and the surface layer is 285-295 gsm, the basis weight of the surface layer is 25-40 gsm, the basis weight of the facing layer is 20-30 gsm, and the basis weight of the bottom layer is 30-40 gsm.

[0014] Optionally, a lining layer is further provided between the bottom layer and the core layer, and the lining layer is made of lining layer pulp, and the lining layer pulp comprises 20-30% of lining layer conifer pulp, 30-50% of first lining layer broadleaf pulp, and 20-40% of second lining layer broadleaf pulp;

[0015] Among them, the freeness range of the coniferous pulp of the bottom lining layer is 280mL-320mL, the freeness range of the broadleaf pulp of the first bottom lining layer is 380mL-420mL, and the freeness range of the broadleaf pulp of the second bottom lining layer is 200mL-270mL.

[0016] Optionally, starch is sprayed between the surface lining layer and the core layer, and the amount of starch is greater than or equal to 0.5 gsm and less than or equal to 4.5 gsm; starch is sprayed between the bottom lining layer and the core layer, and the amount of starch is greater than or equal to 0.5 gsm and less than or equal to 4.5 gsm.

[0017] Optionally, the total weight of the bottom layer, bottom lining layer, core layer, top lining layer and top layer is 285-295gsm, the top layer is 25-35gsm, the top lining layer is 20-30gsm, the bottom lining layer is 20-30gsm, and the bottom layer is 25-35gsm.

[0018] Optionally, the cardboard also includes multiple front coating layers coated on the surface layer and multiple back coating layers coated on the bottom layer, the mass amount of latex in each front coating layer is 12-15%, and the total coating amount of the multiple front coating layers ranges from 28-32gsm; the mass amount of latex in each back coating layer is 12-15%, and the total coating amount of the multiple back coating layers ranges from 28-32gsm.

[0019] Optionally, the core layer also includes a core layer filler, and the core layer filler accounts for 5-10%.

[0020] Optionally, the top layer and the bottom layer are surface-sizing, and the sizing amount ranges from 4.5 to 6.0 gsm.

[0021] The beneficial effects of the present application are as follows: Different from the prior art, the use of the second broadleaf pulp with too low freeness can improve the bonding between layers and fibers of the paperboard, reduce the gaps between layers and fibers, and reduce the sliding between fibers during bending, thereby improving the comprehensive performance of the paperboard, such as the number of times it can withstand beating, stiffness, and the number of times it can withstand folding. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of an embodiment of four-layer papermaking of cardboard of the present application;

[0023] Figure 2 This is a schematic diagram of an embodiment of five-layer papermaking of cardboard of the present application;

[0024] Figure 3 yes Figure 1 Schematic diagram of the front and back of the cardboard after coating;

[0025] Figure 4 yes Figure 2 Schematic diagram of the front and back of the cardboard after coating. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0027] In recent years, with the prevalence of domestic board games and card games, the market has higher and higher requirements for the quality and printing fineness of cards, and the back-end processing requires lamination and reverse glazing, which requires higher flatness and coating strength. The raw materials generally used to make the cards are copperplate cardboard, and in order to reflect the texture of the cards, high-weight copperplate cards are mainly selected. The copperplate cards on the market currently have a high loose thickness, generally greater than 1.2, and the interlayer bonding strength is generally 150-250J / m2. The stiffness is relatively low, and the number of times they can be played is basically less than 30 times. As a result, customers use this type of copperplate card with a low number of play times and a poor experience. In order to meet the game experience and collection needs of high-end players, ordinary copperplate cards have become increasingly difficult to meet the requirements of many customers at home and abroad. Customers hope to have personalized requirements and hope to have higher pursuits in quality. Therefore, the patent aims to develop a special copperplate card for game cards with high playing resistance, high interlayer bonding strength, and high stiffness to meet specific needs. In order to improve the above technical problems, the present application can provide the following embodiments.

[0028] See also Figure 1 The present application provides a cardboard 100, which includes a bottom layer 101, a core layer 103, a lining layer 104 and a surface layer 105 stacked in sequence.

[0029] In one embodiment, the paperboard 100 is manufactured by a four-layer papermaking method of a bottom layer 101, a core layer 103, a surface lining layer 104, and a surface layer 105. Multi-layer papermaking can optimize the quantitative distribution of each layer, thereby alleviating the problem of poor paper machine runnability caused by excessive quantitative weight of a single layer when the number of layers is small, which is conducive to improving the quality of the paperboard 100. In other embodiments, the paperboard 100 can also be manufactured by a five-layer papermaking method of a bottom layer 101, a bottom lining layer 102, a core layer 103, a surface lining layer 104, and a surface layer 105. The five-layer papermaking has a higher papermaking efficiency, and the quality of the paperboard 100 can be further improved.

[0030] In one embodiment, the core layer 103 is made of core layer pulp, and the core layer pulp comprises 10-30% of core layer conifer pulp, 30-70% of first core layer broadleaf pulp, and 20-40% of second core layer broadleaf pulp. The freeness of the core layer conifer pulp is in the range of 280mL-320mL, the freeness of the first core layer broadleaf pulp is in the range of 380mL-420mL, and the freeness of the second core layer broadleaf pulp is in the range of 200mL-270mL.

[0031] The proportion of the core layer of softwood pulp can be, for example, 15-25%, or 10%, 17%, 20%, 23% or 30%. The proportion of the first core layer of broadleaf pulp can be, for example, 30-50%, 40%-50%, or 30%, 35%, 55%, 68% or 70%. The proportion of the second core layer of broadleaf pulp can be, for example, 25-35%, or 20%, 28%, 32% or 40%.

[0032] The freeness of the core softwood pulp may be 290 mL-310 mL, or may be, for example, 295 mL, 300 mL, 315 mL or 320 mL. The freeness of the first core hardwood pulp may be 390 mL-410 mL, or may be, for example, 380 mL, 395 mL, 405 mL or 420 mL. The freeness of the second core hardwood pulp may be 210-260 mL, or may be, for example, 200 mL, 225 mL, 250 mL, 267 mL, etc.

[0033] The core layer conifer pulp is pulp made from coniferous trees, and its fibers are relatively long, and the bonding force between the fibers is relatively strong. The addition of the core layer conifer pulp can ensure that the core layer 103 has appropriate strength and has certain tensile resistance. The first core layer broadleaf pulp and the second core layer broadleaf pulp are pulp made from broadleaf trees, and their fibers are relatively short, and the bonding force between the fibers is relatively weak. The addition of the first core layer broadleaf pulp and the second core layer broadleaf pulp can make the core layer 103 have appropriate softness, and improve the durability of the cardboard 100.

[0034] Freeness is one of the indicators that reflect the water-filtration performance of pulp. Generally speaking, the larger the freeness of pulp, the faster the water-filtration speed. In some embodiments, the water-filtration performance of the above-mentioned pulp is expressed by beating degree, and beating degree and freeness can be converted to each other. This application defines the index of pulp water-filtration performance by freeness.

[0035] Furthermore, the freeness of the second core layer broadleaf pulp is lower than that of the first core layer broadleaf pulp. Adding the second core layer broadleaf pulp with low freeness to the core layer pulp can make the paperboard 100 obtain higher cohesion, reduce the displacement between the core layer fibers, and thus improve the comprehensive performance of the core layer 103.

[0036] In one embodiment, the surface lining 104 is made of a surface lining slurry, and the surface lining slurry comprises 20-30% of a surface lining conifer pulp, 30-60% of a first surface lining broadleaf pulp, and 20-40% of a second surface lining broadleaf pulp. The freeness of the surface lining conifer pulp is in the range of 280 mL-320 mL, the freeness of the first surface lining broadleaf pulp is in the range of 380 mL-420 mL, and the freeness of the second surface lining broadleaf pulp is in the range of 200 mL-270 mL.

[0037] The proportion of coniferous pulp in the surface lining layer can be, for example, 15-25%, or 10%, 18%, 21%, 23% or 30%. The proportion of broadleaf pulp in the first surface lining layer can be, for example, 30-50%, 40%-50%, or 30%, 35%, 55%, 58% or 60%. The proportion of broadleaf pulp in the second surface lining layer can be, for example, 25-35%, or 20%, 29%, 31% or 40%.

[0038] The freeness of the softwood pulp of the facing layer may be 290 mL-310 mL, or may be, for example, 296 mL, 300 mL, 316 mL, or 320 mL. The freeness of the broadleaf pulp of the first facing layer may be 390 mL-410 mL, or may be, for example, 380 mL, 396 mL, 404 mL, or 420 mL. The freeness of the broadleaf pulp of the second facing layer may be 210-260 mL, or may be, for example, 200 mL, 225 mL, 250 mL, 267 mL, etc.

[0039] The coniferous pulp of the surface lining is pulp made from coniferous trees, and its fibers are relatively long, and the bonding force between the fibers is relatively strong. The addition of the coniferous pulp of the surface lining can ensure that the surface lining 104 has appropriate strength and certain tensile resistance. The first surface lining hardwood pulp and the second surface lining hardwood pulp are pulp made from hardwood trees, and their fibers are relatively short, and the bonding force between the fibers is relatively weak. The addition of the first surface lining hardwood pulp and the second surface lining hardwood pulp can make the surface lining 104 have appropriate softness, and improve the durability of the paperboard 100.

[0040] Furthermore, the freeness of the second surface lining layer broadleaf pulp is lower than that of the first surface lining layer broadleaf pulp. The use of the second surface lining layer broadleaf pulp with low freeness in the surface lining layer pulp can make the paperboard 100 obtain higher cohesion, reduce the displacement between the fibers of the surface lining layer 104, and thus improve the comprehensive performance of the surface lining layer 104.

[0041] In one embodiment, the surface layer 105 is made of surface layer pulp, and the composition of the surface layer pulp includes 20-40% of surface layer conifer pulp and 60-80% of surface layer broadleaf pulp. The freeness range of the surface layer conifer pulp is 250-320mL, and the freeness range of the surface layer broadleaf pulp is 350mL-450mL.

[0042] The proportion of softwood pulp in the surface layer may be, for example, 15-25%, or 10%, 17%, 20%, 23% or 35%. The proportion of hardwood pulp in the surface layer may be, for example, 65-75%, or 65%, 70%, 75%, 78% or 79%.

[0043] The freeness of the surface softwood pulp may be 260 mL-310 mL, or may be, for example, 270 mL, 285 mL, 315 mL or 320 mL. The freeness of the surface hardwood pulp may be 365 mL-445 mL, or may be, for example, 380 mL, 395 mL, 405 mL or 420 mL.

[0044] The surface layer of conifer pulp is made of coniferous trees, and its fibers are relatively long and the bonding force between the fibers is relatively strong. The addition of the surface layer of conifer pulp can ensure that the surface layer 105 has a suitable strength and has a certain tensile resistance. The surface layer of broadleaf pulp is made of broadleaf trees, and its fibers are relatively short and the bonding force between the fibers is relatively weak. The addition of the surface layer of broadleaf pulp can make the surface layer 105 have a suitable softness and improve the durability of the paperboard 100.

[0045] In one embodiment, the bottom layer 101 is made of bottom layer pulp, and the bottom layer pulp comprises 20-30% of bottom layer conifer pulp, 30-80% of first bottom layer broadleaf pulp, and 0-40% of second bottom layer broadleaf pulp. The freeness of the bottom layer conifer pulp is in the range of 280mL-320mL, the freeness of the first bottom layer broadleaf pulp is in the range of 380mL-420mL, and the freeness of the second bottom layer broadleaf pulp is in the range of 200mL-270mL.

[0046] The proportion of the bottom layer of softwood pulp can be, for example, 22-28%, or 20%, 24%, 25%, or 29%. The proportion of the first bottom layer of broadleaf pulp can be, for example, 30-50%, 40%-50%, or 30%, 35%, 50%, 55%, 68% or 70%, etc. The proportion of the second bottom layer of broadleaf pulp can be, for example, 10-35%, or 5%, 18%, 30%, 32% or 40%, etc.

[0047] The freeness of the bottom layer of softwood pulp may be 290 mL-310 mL, or may be, for example, 295 mL, 300 mL, 315 mL, or 320 mL. The freeness of the first bottom layer of broadleaf pulp may be 390 mL-410 mL, or may be, for example, 380 mL, 395 mL, 405 mL, or 420 mL. The freeness of the second bottom layer of broadleaf pulp may be 210-260 mL, or may be, for example, 200 mL, 225 mL, 250 mL, or 267 mL.

[0048] The bottom layer of conifer pulp is pulp made from coniferous trees, and its fibers are relatively long, and the bonding force between the fibers is relatively strong. The addition of the bottom layer of conifer pulp can ensure that the bottom layer 101 has a suitable strength and has a certain tensile resistance. The first bottom layer of broadleaf pulp and the second bottom layer of broadleaf pulp are pulp made from broadleaf trees, and their fibers are relatively short, and the bonding force between the fibers is relatively weak. The addition of the first bottom layer of broadleaf pulp and the second bottom layer of broadleaf pulp can make the bottom layer 101 have a suitable softness, and improve the durability of the paperboard 100.

[0049] Furthermore, the freeness of the second bottom layer broadleaf pulp is lower than that of the first bottom layer broadleaf pulp. The use of the second bottom layer broadleaf pulp with low freeness in the bottom layer pulp can make the paperboard 100 obtain higher cohesion, reduce the displacement between the fibers of the bottom layer 101, and thus improve the comprehensive performance of the bottom layer 101.

[0050] In one embodiment, the amount of reinforcing drugs in the surface layer 105, the surface lining layer 104 and the bottom layer 101 is less than or equal to 1%. For example, the amount of reinforcing drugs is 0.2%, 0.5% or 0.8%. The amount of reinforcing drugs in the core layer 103 is less than or equal to 3%, and greater than or equal to 0.5%. For example, the amount of reinforcing drugs in the core layer 103 can be 1.1%, 1.5% or 2.5%. The reinforcing drugs can be, for example, any one of dry strength agents or cationic starch, or a mixture of the two. Reinforcing drugs can increase the strength of each layer. And based on the above embodiments, compared with the prior art, the paperboard 100 of the present application can achieve a higher paperboard strength with less reinforcing drugs. In some embodiments, the amount of reinforcing drugs in the surface layer 105, the surface lining layer 104 and the bottom layer 101 can even be 0.

[0051] In one embodiment, starch is sprayed between the facing layer 104 and the core layer 103, and the amount of starch is greater than or equal to 0.5 gsm and less than or equal to 4.5 gsm. For example, the amount of starch can be 1 gsm, 1.5 gsm, or 3 gsm. Starch is sprayed between the bottom layer 101 and the core layer 103, and the amount of starch is greater than or equal to 0.5 gsm and less than or equal to 4.5 gsm. For example, the amount of starch can be 1 gsm, 1.5 gsm, or 3 gsm.

[0052] The starch may be cassava starch, cationic starch, corn starch, etc., which are not specifically limited here. Spraying starch between the lining layer 104 and the core layer 103 and between the bottom layer 101 and the core layer 103 can ensure the strength of the paperboard 100 .

[0053] In one embodiment, no starch is sprayed between the surface layer 105 and the surface lining layer 104. Such an arrangement is conducive to the bonding between the surface layer 105 and the surface lining layer 104, and can further improve the technical effect of using low freeness broadleaf pulp.

[0054] In one embodiment, the total weight of the bottom layer 101, the core layer 103, the surface lining layer 104 and the surface layer 105 is 285-350gsm, for example, the total weight can be 295gsm, 310gsm or 320gsm. The surface layer 105 is 25-40gsm, for example, 27gsm, 35gsm or 40gsm. The surface lining layer 104 is 20-30gsm, for example, 20gsm, 25gsm or 29gsm. The bottom layer 101 is 30-40gsm, for example, 34gsm or 38gsm. In this weight range, the cardboard 100 has a balanced bulk, stiffness, durability, and interlayer bonding strength, and the customer experience is the best.

[0055] In summary, by using the above-mentioned pulp ratio, freeness, and appropriate parameters control of paper machine hard calendering, soft calendering, and moisture content of the finished paper, the stiffness can reach CD≥8.0mN·m and MD≥16.0mN·m at a bulk thickness of 1.0±0.1 (thickness is equivalent to the basis weight). For example, for copper card with the same basis weight of 370g / m2, the thickness of the copper card generally needs to be about 400um, and the stiffness can reach the above value. The interlayer bonding strength of the coated cardboard 100 produced by this method is ≥500J / m2, the glossiness is ≥55%, and the impact resistance is ≥500 times.

[0056] Based on the above description, the specific embodiment of the four-layer paperboard 100 is introduced as an example. The following embodiment is implemented on a 5-layer fourdrinier paper machine, using a 4-layer papermaking method, with a paper machine width of 8.1m and a designed speed of 900m / min. The product high-end game paperboard 100 has a basis weight of 370g / m2 and a bulk thickness of 1.0cm3 / g. The freeness of high-free broadleaf pulp (first surface layer broadleaf pulp, first surface lining layer broadleaf pulp, first core layer broadleaf pulp, first bottom layer broadleaf pulp) is 380mL, and the freeness of coniferous pulp is 320mL. The basis weight of each layer is introduced as an example, with the basis weight of the surface layer 105 being 27gsm, the basis weight of the surface lining layer 104 being 20gsm, the basis weight of the core layer 103 being 225gsm, and the basis weight of the bottom layer 101 being 38gsm.

[0057] The specific embodiments are as follows:

[0058] First, the first comparative embodiment in the related art is introduced:

[0059] In the related art, the surface layer 105 has a surface layer of 70% broadleaf pulp and a surface layer of 30% coniferous pulp, and the surface layer 105 has a 1% dosage of enhanced medicine. The surface lining layer 104 has a surface layer of 80% broadleaf pulp and a surface layer of 20% coniferous pulp, and the surface lining layer 104 has a 1.5% dosage of enhanced medicine. The core layer 103 has a core layer of 90% broadleaf pulp and a core layer of 10% coniferous pulp, and the core layer 103 has a 2.5% dosage of enhanced medicine. The bottom layer 101 has a bottom layer of 80% broadleaf pulp and a bottom layer of 20% coniferous pulp, and the bottom layer 101 has a 1.5% dosage of enhanced medicine. Low freeness broadleaf pulp is not added in the related art. Among them, the amount of starch sprayed between the surface layer 105 and the surface lining layer 104 is 2.5gsm. The amount of starch sprayed between the surface lining layer 104 and the core layer 103 is 3gsm. The amount of starch sprayed between the core layer 103 and the bottom layer 101 is 2.5 gsm.

[0060] After adopting the above-mentioned ratio in the related technology, the following conclusions were obtained after testing. The interlayer bonding strength was 595 J / m2. In the TV16 test, the front result was 4 times. The back result was 4 times.

[0061] The TV-16 test means: using red ink with a viscosity of 16, printing on the printability tester RI-2, with an ink volume of 0.5 mL, the first ink distribution for 2 minutes, and checking whether bubbles occur after the paper is printed once. If bubbles occur, stop printing and record the number as 0. If bubbles do not occur, continue to distribute the ink for 20 seconds and print the second time. Repeat this process until bubbles occur on the paper, and record the number of times without bubbles. The greater the number, the better the printing strength, which also indicates that the bonding strength between the layers is better.

[0062] The first embodiment of the present application is introduced below:

[0063] In the first embodiment, the surface layer 105 has a surface layer of broadleaf pulp accounting for 70%, a surface layer of coniferous pulp accounting for 30%, and the surface layer 105 has a 0.5% dosage of enhanced medicine. In the surface lining layer 104, the first surface lining layer of broadleaf pulp accounts for 60%, the second surface lining layer of broadleaf pulp accounts for 20%, and the surface lining layer of coniferous pulp accounts for 20%, and the surface lining layer 104 has a 0.5% dosage of enhanced medicine. In the core layer 103, the first core layer of broadleaf pulp accounts for 70%, the second core layer of broadleaf pulp accounts for 20%, and the core layer of coniferous pulp accounts for 10%, and the dosage of enhanced medicine in the core layer 103 is 2.0%. In the bottom layer 101, the first bottom layer of broadleaf pulp accounts for 50%, the bottom layer of coniferous pulp accounts for 30%, and the dosage of enhanced medicine in the bottom layer 101 is 0.5%. Low freeness broadleaf pulp is added in the first embodiment. Among them, no starch is sprayed between the surface layer 105 and the surface lining layer 104. The amount of starch sprayed between the surface lining layer 104 and the core layer 103 is 1.5gsm. The amount of starch sprayed between the core layer 103 and the bottom layer 101 is 1.5 gsm.

[0064] After adopting the ratio in the first embodiment, the following conclusions were obtained after testing: The interlayer bonding strength was 589 J / m2. In the TV16 test, the front side result was 4 times. The back side result was 4 times.

[0065] The second embodiment of the present application is introduced below:

[0066] In the first embodiment, the surface layer 105 has a surface layer of broadleaf pulp accounting for 70%, a surface layer of coniferous pulp accounting for 30%, and the surface layer 105 has a reinforcing drug dosage of 0. In the surface lining layer 104, the first surface lining layer of broadleaf pulp accounts for 60%, the second surface lining layer of broadleaf pulp accounts for 20%, and the surface lining layer of coniferous pulp accounts for 20%, and the surface lining layer of coniferous pulp accounts for 0. In the core layer 103, the first core layer of broadleaf pulp accounts for 70%, the second core layer of broadleaf pulp accounts for 20%, and the core layer of coniferous pulp accounts for 10%, and the core layer of reinforcing drugs uses 1.5%. In the bottom layer 101, the first bottom layer of broadleaf pulp accounts for 50%, the bottom layer of coniferous pulp accounts for 30%, and the bottom layer of reinforcing drugs uses 0. In the second embodiment, low freeness broadleaf pulp is also added, and reinforcing drugs are no longer used in the surface layer 105, the surface lining layer 104 and the bottom layer 101. Among them, starch is not sprayed between the surface layer 105 and the surface lining layer 104. The amount of starch sprayed between the facing layer 104 and the core layer 103 is 1 gsm. The amount of starch sprayed between the core layer 103 and the bottom layer 101 is 1 gsm.

[0067] After adopting the ratio in the second embodiment, the following conclusions were obtained after testing: The interlayer bonding strength was 566 J / m2. In the TV16 test, the front side result was 4 times. The back side result was 4 times.

[0068] The third embodiment of the present application is introduced below:

[0069] In the first embodiment, the surface layer 105 has a surface layer of broadleaf pulp accounting for 70%, a surface layer of coniferous pulp accounting for 30%, and the surface layer 105 has a reinforcing drug dosage of 0. In the surface lining layer 104, the first surface lining layer of broadleaf pulp accounts for 45%, the second surface lining layer of broadleaf pulp accounts for 35%, and the surface lining layer of coniferous pulp accounts for 20%, and the surface lining layer 104 has a reinforcing drug dosage of 0. In the core layer 103, the first core layer of broadleaf pulp accounts for 60%, the second core layer of broadleaf pulp accounts for 30%, and the core layer of coniferous pulp accounts for 10%, and the core layer 103 has a reinforcing drug dosage of 1.5%. In the bottom layer 101, the first bottom layer of broadleaf pulp accounts for 40%, the bottom layer of coniferous pulp accounts for 40%, and the bottom layer 101 has a reinforcing drug dosage of 0. In the third embodiment, a larger proportion of low-free broadleaf pulp is also added, and reinforcing drugs are no longer used in the surface layer 105, the surface lining layer 104, and the bottom layer 101. Among them, starch is not sprayed between the surface layer 105 and the surface lining layer 104. The amount of starch sprayed between the facing layer 104 and the core layer 103 is 1 gsm. The amount of starch sprayed between the core layer 103 and the bottom layer 101 is 1 gsm.

[0070] After adopting the ratio in the second embodiment, the following conclusions were obtained after testing: The interlayer bonding strength was 708 J / m2. In the TV16 test, the front side result was 6 times. The back side result was 6 times.

[0071] In the above specific embodiments, it can be seen from the first comparative example, the first embodiment and the second embodiment that adding low freeness pulp to the four-layer lining, the core layer 103 and the bottom layer 101 can significantly reduce the amount of each reinforcing chemical while ensuring that the strength is basically the same. It can be seen from the second and third embodiments that as the proportion of low freeness broadleaf pulp increases, the reinforcing effect becomes more obvious, and the strength of the cardboard 100 can be improved.

[0072] In one embodiment, see Figure 2 , a backing layer 102 is also arranged between the bottom layer 101 and the core layer 103, that is, the cardboard 100 is made by a five-layer papermaking method. The backing layer 102 is made of a backing layer slurry, and the composition of the backing layer slurry includes 20-30% of a backing layer of coniferous pulp, 30-50% of a first backing layer of broadleaf pulp, and 20-40% of a second backing layer of broadleaf pulp. Among them, the freeness range of the backing layer coniferous pulp is 280mL-320mL, the freeness range of the first backing layer of broadleaf pulp is 380mL-420mL, and the freeness range of the second backing layer of broadleaf pulp is 200mL-270mL.

[0073] The proportion of softwood pulp in the bottom lining layer can be, for example, 22-28%, or 21%, 24%, 27%, or 29%. The proportion of broadleaf pulp in the first bottom lining layer can be, for example, 35-45%, 40%-50%, or 30%, 35%, 45%, 48%, or 49%. The proportion of broadleaf pulp in the second bottom lining layer can be, for example, 25-35%, or 20%, 28%, 32%, or 40%.

[0074] The freeness of the softwood pulp of the backing layer may be 290 mL-310 mL, or may be, for example, 295 mL, 300 mL, 315 mL or 320 mL. The freeness of the broadleaf pulp of the first backing layer may be 390 mL-410 mL, or may be, for example, 380 mL, 395 mL, 405 mL or 420 mL. The freeness of the broadleaf pulp of the second backing layer may be 210-260 mL, or may be, for example, 200 mL, 225 mL, 250 mL, 267 mL, etc.

[0075] The coniferous pulp of the bottom lining layer is pulp made from coniferous trees, and its fibers are relatively long, and the bonding force between the fibers is relatively strong. The addition of the coniferous pulp of the bottom lining layer can ensure that the bottom lining layer 102 has appropriate strength and certain tensile resistance. The first bottom lining layer broadleaf pulp and the second bottom lining layer broadleaf pulp are pulp made from broadleaf trees, and their fibers are relatively short, and the bonding force between the fibers is relatively weak. The addition of the first bottom lining layer broadleaf pulp and the second bottom lining layer broadleaf pulp can make the bottom lining layer 102 have appropriate softness, and improve the durability of the cardboard 100.

[0076] Furthermore, the freeness of the second backing layer broadleaf pulp is lower than that of the first backing layer broadleaf pulp. The use of the second backing layer broadleaf pulp with low freeness in the backing layer pulp can make the paperboard 100 obtain higher cohesion, reduce the displacement between the fibers of the backing layer 102, and thus improve the comprehensive performance of the backing layer 102.

[0077] In one embodiment, starch is sprayed between the surface lining layer 104 and the core layer 103, and the amount of starch is greater than or equal to 0.5gsm and less than or equal to 4.5gsm. For example, the amount of starch can be 1gsm, 1.5gsm, or 3gsm. Starch is sprayed between the bottom lining layer 102 and the core layer 103, and the amount of starch is greater than or equal to 0.5gsm and less than or equal to 4.5gsm. For example, the amount of starch can be 1gsm, 1.5gsm, or 3gsm. Among them, the starch can be cassava native starch, cationic starch, corn native starch, etc., which are not specifically limited here. Spraying starch between the surface lining layer 104 and the core layer 103 and between the bottom lining layer 102 and the core layer 103 can ensure the strength of the cardboard 100.

[0078] On the basis of the previous embodiment, no starch is sprayed between the surface layer 105 and the surface lining layer 104, and no starch is sprayed between the bottom layer 101 and the bottom lining layer 102. Such an arrangement is conducive to the bonding between the surface layer 105 and the surface lining layer 104, and can further improve the technical effect of using low freeness broadleaf pulp.

[0079] In one embodiment, the total weight of the bottom layer 101, the bottom lining layer 102, the core layer 103, the top lining layer 104 and the top layer 105 is 285-350gsm, for example, the total weight can be 295gsm, 310gsm or 320gsm. The top layer 105 is 25-35gsm, for example, 27gsm, 32gsm or 35gsm. The top lining layer 104 is 20-30gsm, for example, 20gsm, 23gsm, 25gsm or 29gsm. The bottom lining layer 102 is 20-30gsm, for example, 20gsm, 25gsm or 29gsm. The bottom layer 101 is 25-35gsm, for example, 27gsm, 29gsm or 32gsm.

[0080] In one embodiment, see Figure 3 and Figure 4 , the cardboard 100 also includes a plurality of front coating layers 106 coated on the surface layer 105 and a plurality of back coating layers 107 coated on the bottom layer 101, the mass amount of latex in each front coating layer 106 is 12-15%, such as 13% or 14%, and the total coating amount of the multi-layer front coating layer 106 ranges from 28-32gsm, such as 29gsm or 31gsm. The mass amount of latex in each back coating layer 107 is 12-15%, such as 13% or 14%, and the total coating amount of the multi-layer back coating layer 107 ranges from 28-32gsm, such as 29gsm or 31gsm. Among them, the front coating layer 106 and the back coating layer 107 can be two coatings or three coatings, which are not specifically limited here. Optionally, the latex type selects styrene-butadiene latex with better strength, tg5~-5℃. If the latex dosage is too low, the coating strength is poor, and the cardboard 100 may be wrinkled due to bending, folding and other external forces during use. The total coating amount cannot be too low, otherwise the tightness of the cardboard 100 cannot be achieved, and the coating amount cannot be too high, otherwise the stiffness of the cardboard 100 cannot be achieved.

[0081] The main component of the coating is 100% heavy calcium carbonate (GCC), the dispersant is polyacrylic acid sodium salt, the dosage is 0.1-0.2%, the defoamer is mineral oil, the dosage is 0.05-0.15%, the lubricant is sodium stearate, the dosage is 0.3-0.6%, the water-resistant agent is one of PAPE or PAPU, the dosage is 0.15-0.5%, the pH of the coating is adjusted to 8-10 with NaOH, and the solid content of the coating is 65-70%.

[0082] In one embodiment, the core layer 103 also includes a core filler, and the core filler accounts for 5-10%. In addition to the control of the raw material ratio, freeness, and coating amount, the amount of core filler is controlled at 5-10%, for example, 8% or 9%. The core filler can be heavy calcium carbonate (GCC) or talcum powder, which is not specifically limited here. Among them, among the parameters of the paper machine, the rear end hard calendering pressure can be 70-80Kn / m, and the soft calendering pressure can be controlled at 40-60Kn / m, so as to ensure that the bulk thickness of the finished paper is controlled at 1.0±0.1 (the thickness is equivalent to the quantitative). The moisture content of the cardboard 100 is controlled at 5.6% to 6.2%.

[0083] In one embodiment, the surface layer 105 and the bottom layer 101 are surface-sizing, and the amount of sizing applied is in the range of 4.5-6.0 gsm. This arrangement can improve the stiffness of the cardboard 100 while ensuring the printing strength of the cardboard 100.

[0084] Based on the above description, the specific embodiments of the four-layer and five-layer paperboard 100 are introduced as examples. The following embodiments are implemented on a five-layer fourdrinier paper machine, using four-layer and five-layer papermaking, with a paper machine width of 8.1m and a designed speed of 900m / min. In the embodiments, the freeness of high-freeness hardwood pulp is 400mL, the freeness of coniferous pulp is 300mL, and the freeness of low-freeness hardwood pulp is 230mL.

[0085] First, the second comparative example is introduced.

[0086] In the related art, a four-layer papermaking method is adopted, in which the surface layer 105 has a quantitative weight of 19gsm, and the surface layer coniferous pulp accounts for 20% of the slurry ratio, and the surface layer broadleaf pulp accounts for 80%. The surface lining layer 104 has a quantitative weight of 18gsm, and the surface layer coniferous pulp accounts for 20% of the slurry ratio, and the surface layer broadleaf pulp accounts for 80%. The core layer 103 has a quantitative weight of 205gsm, and the amount of reinforcing drugs is 1.2%. In the slurry ratio, the core layer coniferous pulp accounts for 10%, the core layer 103 broadleaf pulp accounts for 50%, and the mechanical pulp accounts for 35%. The bottom layer 101 has a quantitative weight of 30gsm, and the bottom layer coniferous pulp accounts for 20% of the slurry ratio, and the bottom layer broadleaf pulp accounts for 80%.

[0087] The glue amount of the surface layer 105 and the bottom layer 101 is 4gsm, the coating amount of the front side is 38gsm, and the coating amount of the back side is 40gsm. The core layer filler amount in the core layer 103 is 30%. 3.5gsm of starch is sprayed between the surface lining layer 104 and the core layer 103, and 3.5gsm of starch is sprayed between the bottom layer 101 and the core layer 103.

[0088] The above papermaking was carried out under the following paper machine parameters: machine speed 1000 m / min, hard calender line pressure 40 Kn / m, soft calender line pressure 20 Kn / m.

[0089] The test data of 100 pieces of cardboard produced under the above conditions are as follows:

[0090] The weight of cardboard 100 is 370gsm under the relevant standard (ISO 536). The thickness is 405um under the relevant standard (ISO534). The moisture is 6.3% under the relevant standard (ISO 287). The transverse stiffness is 8.99mN·m under the relevant standard (ISO2493-2). The longitudinal stiffness is 17.6mN·m under the relevant standard (ISO 2493-2). The roughness / smoothness is 0.67um on the front and 0.86um on the back under the relevant standard (ISO 8791-4). The interlayer bonding strength is 229J / m2 under the test. The impact resistance test is 20 times (instructions for impact resistance test: the LC / T-01 folding resistance tester produced by Ningbo Liancheng Machinery Co., Ltd. is used for the test. The data indicates the maximum number of times the paper can be bent and swung back and forth without wrinkles. The larger the data, the more resistant the paper is to bending and folding. The following impact resistance tests are the same). The anti-picking property is 2.17m / s on the front side and 2.16m / s on the back side under the relevant standard (ISO 3783) test. The TV-16 test is 3 times for both the front and back sides. The flatness test is 2.1um on the front side and 2.2um on the back side (the flatness data uses the OSD Value in the L&W OptiTopo optical roughness meter. This data indicates the deviation value of the unevenness of the paper surface. The smaller the value, the smoother and more uniform the paper surface. The same applies to the flatness test below). The glossiness is 59% on the front side and 58% on the back side under the relevant standard (ISO 8254-1) test.

[0091] The fourth embodiment is introduced, and the fourth embodiment adopts a four-layer papermaking method.

[0092] The surface layer 105 has a quantitative of 27gsm, and the surface layer coniferous pulp accounts for 30% of the pulp ratio, the surface layer broadleaf pulp accounts for 70%, and the surface layer 105 has a reinforcing drug dosage of 0.5%. The surface lining layer 104 has a quantitative of 20gsm, and the surface layer coniferous pulp accounts for 20% of the pulp ratio, the first surface layer broadleaf pulp accounts for 50%, and the second surface lining layer broadleaf pulp accounts for 30%. The surface lining layer 104 has a reinforcing drug dosage of 0.5%. The core layer 103 has a quantitative of 207gsm, and the core layer 103 has a reinforcing drug dosage of 1.5%. The core layer coniferous pulp accounts for 15% of the pulp ratio, the first core layer broadleaf pulp accounts for 45%, and the second core layer broadleaf pulp accounts for 40%. The bottom layer 101 has a quantitative of 38gsm, and the bottom layer coniferous pulp accounts for 30%, the first bottom layer broadleaf pulp accounts for 50%, and the second bottom layer broadleaf pulp accounts for 30%. The bottom layer 101 has a reinforcing drug dosage of 0.5%.

[0093] The glue amount of the surface layer 105 and the bottom layer 101 is 4.5 gsm, the coating amount of the front side is 30 gsm, and the coating amount of the back side is 31 gsm. The core layer filler amount in the core layer 103 is 10%. 3.5 gsm of starch is sprayed between the surface lining layer 104 and the core layer 103, and 3.5 gsm of starch is sprayed between the bottom layer 101 and the core layer 103.

[0094] The above papermaking was carried out under the following paper machine parameters: machine speed 700 m / min, hard calender line pressure 70 Kn / m, soft calender line pressure 40 Kn / m.

[0095] The test data of 100 pieces of cardboard produced under the above conditions are as follows:

[0096] The weight of cardboard 100 is 370gsm under the relevant standard (ISO 536) test. The thickness is 374um under the relevant standard (ISO534) test. The moisture content is 5.8% under the relevant standard (ISO 287) test. The transverse stiffness is 10.7mN·m under the relevant standard (ISO2493-2) test. The longitudinal stiffness is 17.25mN·m under the relevant standard (ISO 2493-2) test. The roughness / smoothness is 0.7um on the front side and 0.91um on the back side under the relevant standard (ISO 8791-4) test. The interlayer bonding strength is 568J / m2 under the test. The impact resistance test is 669 times. The anti-pulling property is 2.28m / s on the front side and 2.35m / s on the back side under the relevant standard (ISO 3783) test. In the TV-16 test, both the front and back sides are tested 4 times. In the flatness test, the front side is 2.2um, and the back side is 2.1um. In the relevant standard (ISO 8254-1) test, the glossiness is 56% on the front side and 56% on the back side.

[0097] The fifth embodiment is introduced, and the fifth embodiment adopts a five-layer papermaking method.

[0098] The surface layer 105 has a quantitative of 30gsm, and the surface layer coniferous pulp accounts for 30% of the pulp ratio, the surface layer broadleaf pulp accounts for 70%, and the surface layer 105 has a reinforcing drug dosage of 0.5%. The surface lining layer 104 has a quantitative of 20gsm, and the surface layer coniferous pulp accounts for 20%, the first surface layer broadleaf pulp accounts for 50%, and the second surface lining layer broadleaf pulp accounts for 30%. The surface lining layer 104 has a quantitative of 0.5%. The core layer 103 has a quantitative of 192gsm, and the core layer 103 has a reinforcing drug dosage of 1.5%. The core layer coniferous pulp accounts for 20%, the first core layer broadleaf pulp accounts for 55%, and the second core layer broadleaf pulp accounts for 25%. The bottom lining layer 102 has a quantitative of 20gsm, and the bottom lining layer coniferous pulp accounts for 20%, the first bottom lining layer broadleaf pulp accounts for 40%, and the second bottom lining layer broadleaf pulp accounts for 40%. The bottom lining layer 102 has a reinforcing drug dosage of 0.5%. The basis weight of the bottom layer 101 is 30gsm, the bottom layer coniferous pulp accounts for 30% of the pulp ratio, the first bottom layer broadleaf pulp accounts for 70%, and the amount of reinforcing drugs used in the bottom layer 101 is 0.5%.

[0099] The glue amount of the surface layer 105 and the bottom layer 101 is 4.5 gsm, the coating amount of the front side is 30 gsm, and the coating amount of the back side is 30 gsm. The core layer filler amount in the core layer 103 is 10%. 3.5 gsm of starch is sprayed between the surface lining layer 104 and the core layer 103, and 3.5 gsm of starch is sprayed between the bottom lining layer 102 and the core layer 103.

[0100] The above papermaking was carried out under the following paper machine parameters: machine speed 900 m / min, hard calender line pressure 80 Kn / m, soft calender line pressure 40 Kn / m.

[0101] The test data of 100 pieces of cardboard produced under the above conditions are as follows:

[0102] The weight of cardboard 100 is 370gsm under the relevant standard (ISO 536) test. The thickness is 370um under the relevant standard (ISO534) test. The moisture content is 5.7% under the relevant standard (ISO 287) test. The transverse stiffness is 10.51mN·m under the relevant standard (ISO2493-2) test. The longitudinal stiffness is 17.08mN·m under the relevant standard (ISO 2493-2) test. The roughness / smoothness is 0.7um on the front side and 0.75um on the back side under the relevant standard (ISO 8791-4) test. The interlayer bonding strength is 580J / m2 under the test. The impact resistance test is 989 times. The anti-pulling property is 2.32m / s on the front side and 2.27m / s on the back side under the relevant standard (ISO 3783) test. In the TV-16 test, the front side is 6 times and the back side is 7 times. In the flatness test, the front side is 1.7um and the back side is 1.7um. The glossiness is 56% on the front side and 56% on the back side under the relevant standard (ISO 8254-1) test.

[0103] In summary, when the cardboard 100 is bent, the deformation often occurs due to a slight displacement between the fibers of the base paper, and the slight displacement between the fibers is mainly reflected in two aspects on the multi-layer cardboard: the displacement between the fibers and the displacement between the fiber layers. Therefore, in order to reduce the displacement between the fibers when the cardboard is bent, the cohesion between the fibers of each layer is improved, and the bonding between the layers is improved. The bonding between the layers and the bonding between the fibers is improved mainly by using low-free hardwood pulp, spraying starch between the layers, and reinforcing drugs in each layer. In addition, by controlling the process parameters of the paper machine, such as hard calendering, soft calendering, fillers, coating amount, etc., the tightness of the base paper and the finished paper is controlled, the gaps between the layers and the fibers are reduced, and the sliding between the fibers when bending is reduced. In addition, because the paper is coated, the strength of the coating must be guaranteed, mainly by selecting the type of latex and ensuring the amount of latex. The present application utilizes the control of the above-mentioned slurry ratio, freeness, moisture, tightness, etc., and the stiffness can reach CD ≥ 8.0 mN·m in the transverse direction and MD ≥ 16.0 mN·m in the longitudinal direction when the bulk thickness is 1.0±0.1 (thickness is equivalent to the quantitative). For example, for a copper card with the same quantitative of 370g / m2, the thickness of the copper card generally needs to be about 400um, and the stiffness can reach the above value. The interlayer bonding strength of the coated cardboard 100 produced by this method is ≥ 500 J / m2, the glossiness is ≥ 55%, and the impact resistance is ≥ 500 times, and the comprehensive performance of the cardboard 100 is improved.

[0104] The above are merely embodiments of the present application and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A kind of cardboard, It is characterized in that include: A bottom layer, a core layer, a lining layer and a surface layer are stacked in sequence; The core layer is made of core layer pulp, and the core layer pulp comprises 10-30% of core layer coniferous pulp, 35-70% of first core layer broadleaf pulp, and 20-32% of second core layer broadleaf pulp; The freeness of the core layer coniferous pulp is in the range of 280mL-320mL, the freeness of the first core layer broadleaf pulp is in the range of 380mL-420mL, the freeness of the second core layer broadleaf pulp is in the range of 200mL-270mL, the freeness of the second core layer broadleaf pulp is lower than the freeness of the first core layer broadleaf pulp, and the second core layer broadleaf pulp with low freeness is added to the core layer pulp; The surface lining is made of surface lining slurry, and the surface lining slurry comprises 20-30% of surface lining coniferous pulp, 35-60% of first surface lining broadleaf pulp, and 20-31% of second surface lining broadleaf pulp; The freeness of the coniferous pulp of the surface lining layer is in the range of 280 mL to 320 mL, the freeness of the broadleaf pulp of the first surface lining layer is in the range of 380 mL to 420 mL, and the freeness of the broadleaf pulp of the second surface lining layer is in the range of 200 mL to 270 mL; The surface layer is made of surface layer pulp, and the surface layer pulp comprises 20-40% of surface layer conifer pulp and 60-80% of surface layer broadleaf pulp; The freeness of the surface layer conifer pulp is in the range of 250-320 mL, and the freeness of the surface layer broadleaf pulp is in the range of 350 mL-450 mL; The bottom layer is made of bottom layer pulp, and the bottom layer pulp comprises 20-29% of bottom layer conifer pulp, 30-80% of first bottom layer broadleaf pulp, and 0-40% of second bottom layer broadleaf pulp; The freeness of the bottom layer of coniferous pulp is in the range of 280 mL to 320 mL, the freeness of the first bottom layer of broadleaf pulp is in the range of 380 mL to 420 mL, and the freeness of the second bottom layer of broadleaf pulp is in the range of 200 mL to 270 mL; The amount of the reinforcing drug in the surface layer, the surface lining layer and the bottom layer is less than or equal to 1%; the amount of the reinforcing drug in the core layer is less than or equal to 3% and greater than or equal to 0.5%; The total weight of the bottom layer, the core layer, the facing layer and the surface layer is 285-295 gsm, the surface layer has a weight of 25-40 gsm, the facing layer has a weight of 20-30 gsm, and the bottom layer has a weight of 30-40 gsm.

2. The cardboard according to claim 1, Features: Starch is sprayed between the lining layer and the core layer, and the amount of starch is greater than or equal to 0.5 gsm and less than or equal to 4.5 gsm; starch is sprayed between the bottom layer and the core layer, and the amount of starch is greater than or equal to 0.5 gsm and less than or equal to 4.5 gsm.

3. The cardboard according to claim 1, Features: A lining layer is also provided between the bottom layer and the core layer, and the lining layer is made of lining layer pulp, and the lining layer pulp comprises 20-30% of lining layer conifer pulp, 30-50% of first lining layer broadleaf pulp, and 20-40% of second lining layer broadleaf pulp; Among them, the freeness range of the coniferous pulp of the bottom lining layer is 280mL-320mL, the freeness range of the broadleaf pulp of the first bottom lining layer is 380mL-420mL, and the freeness range of the broadleaf pulp of the second bottom lining layer is 200mL-270mL.

4. The cardboard according to claim 3, Features: Starch is sprayed between the surface lining layer and the core layer, and the amount of starch is greater than or equal to 0.5gsm and less than or equal to 4.5gsm; starch is sprayed between the bottom lining layer and the core layer, and the amount of starch is greater than or equal to 0.5gsm and less than or equal to 4.5gsm.

5. The cardboard according to claim 3, Features: The total weight of the bottom layer, the bottom lining layer, the core layer, the surface lining layer and the surface layer is 285-295gsm, the surface layer has a weight of 25-35gsm, the surface lining layer has a weight of 20-30gsm, the bottom lining layer has a weight of 20-30gsm, and the bottom layer has a weight of 25-35gsm.

6. The cardboard according to claim 1, Features: The cardboard also includes multiple front coating layers coated on the surface layer and multiple back coating layers coated on the bottom layer, the mass content of latex in each front coating layer is 12-15%, and the total coating amount of the multiple front coating layers ranges from 28 to 32 gsm; the mass content of latex in each back coating layer is 12-15%, and the total coating amount of the multiple back coating layers ranges from 28 to 32 gsm.

7. The cardboard according to claim 1, Features: The core layer also includes a core layer filler, and the core layer filler accounts for 5-10%.

8. The cardboard according to claim 1, Features: The surface layer and the bottom layer are surface-sizing, and the amount of sizing applied is in the range of 4.5-6.0 gsm.

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