Corrugated cardboard

Abstract

To provide a corrugated cardboard that can be used as a building material with fire resistance, while ensuring that it is also lightweight and easy to work with.SOLUTION: A corrugated cardboard 1 comprises a base material 10 containing expansive graphite.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to corrugated cardboard used as a building material. [Background technology]

[0002] Currently, due to the aging and declining number of construction workers, there is an increasing demand for easier construction. In addition, from the perspective of environmental impact, there is also an increasing demand for reduced carbon dioxide emissions. Regarding these two demands, the former requires lightweight building materials and workability that does not require tools, while the latter requires reduced carbon dioxide emissions during manufacturing and demolition, and insulation. In recent years, the use of corrugated cardboard has been attracting attention as a building material that meets these demands.

[0003] For example, Patent Document 1 discloses a building component having excellent soundproofing, heat insulation, and waterproofing properties, the building component having a base material including a corrugated cardboard layer and a coating layer containing a synthetic resin and provided on at least a portion of the surface of the base material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Utility Model Registration No. 3203947 Summary of the Invention [Problem to be solved by the invention]

[0005] It is possible to meet both of the above requirements by using corrugated cardboard as a building material, but simply using conventional corrugated cardboard does not provide the fire resistance required for building materials, and there are problems with using conventional corrugated cardboard as a building material.

[0006] Therefore, an object of the present invention is to provide a corrugated board that can be used as a fire-resistant building material while also ensuring light weight and good workability. [Means for solving the problem]

[0007] As a result of extensive research, the inventors have found that the above problems can be solved by incorporating expandable graphite into the base material that forms the corrugated board, and have completed the present invention as described below. That is, the present invention provides the following [1] to [3]. [1] Corrugated board with a substrate containing expandable graphite. [2] The cardboard according to [1], wherein the content of the expandable graphite in the base material is 5% by mass or more. [3] The cardboard according to [1] or [2], wherein the base material contains at least one of a boron-based flame retardant and a phosphorus-based flame retardant. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a corrugated board that can be used as a fire-resistant building material while ensuring light weight and good workability. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view of a corrugated board according to one embodiment of the present invention. [Figure 2] 1 is a schematic cross-sectional view of a corrugated board according to one embodiment of the present invention. [Figure 3] 1 is a schematic cross-sectional view of a corrugated board according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in more detail below with reference to embodiments. As shown in Fig. 1, the corrugated board 1 according to the embodiment of the present invention is formed of a base material 10, which is made up of liners 20, 20 and a core 30. The base material 10 of the corrugated board 1 according to the embodiment of the present invention contains expandable graphite.

[0011] The corrugated cardboard 1 according to the embodiment of the present invention is lightweight, easy to process, and ensures excellent workability, making it suitable for use as a building material. Furthermore, the corrugated cardboard 1 has an air layer formed by the core 30, which is the base material 10, making it suitable for use as a building material with excellent heat insulation. Furthermore, the corrugated cardboard 1 is easy to recycle, contributing to the reduction of carbon dioxide emissions.

[0012] <Composition of cardboard> The corrugated cardboard 1 includes a corrugating medium 30 and liners 20, 20 provided on both sides of the corrugating medium 30. The corrugating medium 30 is formed of wave-shaped flutes, and the peaks of the wave-shaped flutes are bonded to the liners 20, 20 on both sides. The liners 20, 20 and the corrugating medium 30 are preferably bonded with an adhesive (not shown). The substrate 10 constituting the corrugating medium 30 and the liner 20 is preferably formed from base paper (corrugating medium raw paper, liner raw paper) as described below.

[0013] The corrugated board 1 may be made of one layer of corrugated board called a single flute, as shown in Figure 1. In this specification, the number of corrugated board layers is the number of corrugated boards 30 provided in the thickness direction of the corrugated board 1. When the corrugated board 1 is made of one layer of corrugated board, it is preferable that it be a so-called double-sided corrugated board, which has a corrugated board 30 and liners 20, 20 provided on both sides of the corrugated board, as shown in Figure 1.

[0014] The corrugated cardboard 1 may be made of two layers of cardboard called double flute, as shown in Fig. 2(a). In addition, if the corrugated cardboard 1 has multiple layers of cardboard, it may be made of three layers of cardboard, as shown in Fig. 2(b), or may be made of four or more layers of cardboard, although not shown. The corrugated board 1 has two or more corrugated board layers, which increases its mechanical strength and makes it suitable for use as a building material that requires high mechanical strength. From the viewpoint of increasing the mechanical strength, the corrugated board 1 preferably has three or more corrugated board layers. The number of cardboard layers of the cardboard 1 is not particularly limited, but from the viewpoint of preventing the thickness from becoming greater than necessary as a building material, it is sufficient to have, for example, 10 layers or less, but 7 layers or less is preferable, and 5 layers or less is more preferable.

[0015] The number of flutes in each core 30 that forms the corrugated flutes is not particularly limited, but should be approximately 20 to 110 per 30 cm, preferably 30 to 100, and more preferably 32 to 55. Furthermore, the flute height in each core 30 should be approximately 1 to 6 mm, preferably 1.5 to 5.5 mm, and more preferably 2.5 to 5.5 mm. Cores 30 with the above number of flutes and flute height can be manufactured for general purposes, and also facilitate improving the mechanical strength of the corrugated cardboard 1.

[0016] Each core 30 may be configured as an A flute, B flute, C flute, or E flute as defined in JIS Z 1516:2003, although there are no particular limitations thereon. The A flute has 34±2 flutes per 30 cm, and the flute height is generally about 5 mm. The B flute has 50±2 flutes per 30 cm, and the flute height is generally about 3 mm. The C flute has 40±2 flutes per 30 cm, and the flute height is generally about 4 mm. The E flute has 93±5 flutes per 30 cm, and the flute height is generally about 1.8 mm.

[0017] When the corrugated board 1 has two or more corrugated board layers, it is preferable that the corrugated board layers have at least two or more types of flutes, as shown in Figures 2(a) and 2(b) and Figures 3(a) and 3(b). Here, it is preferable that the flutes are of different types, with different numbers of flutes, and typically the flute heights also differ according to the number of flutes. In the present invention, by using corrugated board layers with different types of flutes as the corrugated board 1, it becomes easier to obtain building materials with high mechanical strength.

[0018] When the cardboard 1 is made up of two or more types of cardboard layers, it is more preferable that it has two or more types of cardboard layers with different flute types as defined in JIS Z 1516:2003, and when it is made up of two cardboard layers, it is preferable that the cardboard 1 is, for example, any of AB flute, AC flute, AE flute, BC flute, BE flute, or CE flute. Furthermore, when the corrugated cardboard 1 is made up of three or more corrugated cardboard layers, it may have three or more types of flutes, such as ABC flutes and AABE flutes, or it may have two types of flutes, such as ACA flutes, AAB flutes, and AAC flutes. In other words, when the corrugated cardboard 1 is made up of two or more types of corrugated cardboard layers and has three or more corrugated cardboard layers, some of the layers may have the same type of flutes. Note that Figures 2(a), (b) and Figures 3(a), (b) are examples in which two different types of cardboard layers with different flutes are stacked, while Figures 2(b) and 3(b) are examples in which an additional cardboard layer with the same type of flute is also provided.

[0019] When the corrugated board 1 is made up of two corrugated board layers, it may have three liners 20 and a core 30 disposed between each of the liners 20, 20, as shown in Figure 2(a). Similarly, when the corrugated board 1 is made up of three corrugated board layers, it may have four liners 20 and a core 30 disposed between each of the liners 20, 20, as shown in Figure 2(b). That is, in the structure shown in Figures 2(a) and (b), adjacent cores 30 may be bonded to the same liner 20 between them. A similar structure may be used when the corrugated board 1 is made up of four or more corrugated board layers.

[0020] When the cardboard 1 has two or more cardboard layers, adjacent cores 30, 30 may have two liners 20, 20 between them, as shown in Figures 3(a) and (b), in which case the adjacent cores 30, 30 may be adhered to separate liners 20. 3(a) and 3(b), a corrugated cardboard layer consisting of a core 30 and a pair of liners 20, 20 on both sides of the core 30 may be bonded to another corrugated cardboard layer, a liner 20, via an adhesive 40. With this configuration, a corrugated cardboard 1 can be obtained by bonding general-purpose corrugated cardboard with the adhesive 40. This makes it easier to manufacture a partition wall 10 with high mechanical strength using a simple manufacturing method. In addition, in the configuration shown in Fig. 3, there are two liners 20 between adjacent cores 30, 30, but either of the liners between adjacent cores 30, 30 may have two liners as shown in Fig. 3(a) and (b), or either of the liners may have one liners as shown in Fig. 2(a) and (b). Furthermore, the number of liners between adjacent cores 30, 30 is not limited to one or two, but may be three or more.

[0021] When the corrugated board 1 has two or more layers of corrugated board, it is preferable to use a fire-resistant adhesive as the adhesive that bonds the corrugated board layers together. Here, in the configuration shown in Figures 3(a) and 3(b), the adhesive that bonds the corrugated board layers together is preferably the adhesive 40 that bonds the liners 20, 20 together. On the other hand, in the configuration shown in Figures 2(a) and 2(b), the adhesive that bonds the corrugated board layers together is preferably an adhesive (not shown) that bonds at least one of the adjacent corrugations 30, 30 to the liner 20 disposed between these adjacent corrugations 30, 30. By using a fire-resistant adhesive as the adhesive for bonding between layers of corrugated cardboard, a partition wall with high fire resistance can be manufactured. Also, for example, by bonding together multiple sheets of commonly used single-flute corrugated cardboard (double-sided or single-sided) or double-flute corrugated cardboard in the thickness direction using a fire-resistant adhesive, a corrugated cardboard 1 with high fire resistance and mechanical strength can be easily manufactured. Furthermore, when there are three or more cardboard layers, it is preferable that all of the cardboard layers are bonded together with a fire-resistant adhesive, but some of the cardboard layers may be bonded together with a fire-resistant adhesive and some of the cardboard layers may be bonded together with an adhesive other than a fire-resistant adhesive.

[0022] The fire-resistant adhesive is not particularly limited as long as it can be bonded to base paper and has fire resistance, but inorganic adhesives are preferred. Examples of inorganic adhesives include water glass-based adhesives that use water glass as an adhesive component. The water glass-based adhesive may be made of water glass composed of water and silicates such as sodium silicate, but may also contain inorganic fillers and other additives in addition to water glass as appropriate. Using a water glass-based adhesive as the fire-resistant adhesive improves fire resistance while facilitating bonding between liners, which are base paper, or between a liner and a core.

[0023] The thickness of the corrugated cardboard 1 is not particularly limited, but may be, for example, about 5 to 30 mm, preferably 9 to 25 mm, and more preferably 12 to 25 mm. When the thickness of the corrugated cardboard 1 is equal to or greater than the above-mentioned lower limit, it is possible to impart mechanical strength appropriate for use as a building material. Furthermore, when the thickness is equal to or less than the above-mentioned upper limit, the building material as the corrugated cardboard 1 can be used appropriately in buildings without narrowing the living space of the building. The thickness of the corrugated cardboard 1 is the total thickness of the corrugated cardboard 1.

[0024] <Paper raw materials> The base material 10 constituting the corrugated board 1 contains pulp as a paper raw material. Any known pulp can be used without any particular limitation. Specific examples include various pulps derived from wood fibers, such as bleached softwood kraft pulp (NBKP), bleached hardwood kraft pulp (LBKP), unbleached softwood kraft pulp (NUKP), unbleached hardwood kraft pulp (LUKP), groundwood pulp (GP), refiner ground pulp (RGP), chemical pulp (CP), thermomechanical pulp (TMP), and chemithermomechanical pulp (CTMP), as well as non-wood pulps obtained from kenaf, bagasse, bamboo, hemp, straw, etc. Furthermore, the pulp may be recycled paper pulp. The waste paper used as the raw material for waste paper pulp is not particularly limited, but examples include recycled corrugated cardboard, white paper, extra white paper, medium white paper, fine paper, fine coated paper, medium paper, medium coated paper, recycled paper, recycled magazine paper, and recycled newspaper paper. The pulp content in the substrate 10 containing expandable graphite may be, for example, 30% by mass or more, preferably 40% by mass or more, more preferably 45% by mass or more, and may be, for example, 94% by mass or less, preferably 80% by mass or less, more preferably 70% by mass or less.

[0025] <Expandable graphite> The substrate 10 constituting the corrugated board 1 contains expandable graphite. The expandable graphite is preferably contained so as to be dispersed inside the base paper made of pulp. By containing expandable graphite in the substrate 10, the substrate 10 expands appropriately when heated by a fire, and the mechanical strength of the expansion residue after expansion is excellent, improving fire resistance. Note that the expandable graphite referred to here does not substantially expand during the manufacturing process of the corrugated board described below, and the thermal expansion of the substrate 10 containing expandable graphite is maintained. In the corrugated cardboard 1, it is preferable that at least one of the liner 20 and the core 30 serving as the base material 10 contains expandable graphite, but it may also be contained in both the liner 20 and the core 30. When the liner 20 contains expandable graphite, the entire liner 20 in the cardboard 1 may contain expandable graphite, or only a portion of the liner 20 may contain expandable graphite. Also, when the core 30 in the cardboard 1 contains expandable graphite, the entire core 30 in the cardboard 1 may contain expandable graphite, or only a portion of the core 30 may contain expandable graphite. From the viewpoint of exhibiting good fire resistance of the cardboard 1, it is preferable that at least the liner 20, which is arranged as the outermost layer of the base material 10, contains expandable graphite, it is more preferable that the liners 20 of both outermost layers contain expandable graphite, and it is even more preferable that all of the liners 20 and cores 30, which are the base material 10 that constitute the cardboard 1, contain expandable graphite.

[0026] The expansion start temperature of the expandable graphite is not particularly limited, but is preferably 100 to 350°C, more preferably 150 to 300°C, and even more preferably 160 to 250°C. By setting the temperature at or below these lower limits, the expandable graphite is prevented from accidentally expanding due to heating other than that caused by a fire. Furthermore, by setting the temperature at or below these upper limits, the expandable graphite is more likely to reliably expand due to heating caused by a fire. The expansion starting temperature of expandable graphite can be measured by heating a predetermined amount (e.g., 100 mg) of expandable graphite at a constant heating rate (e.g., 10°C / min) and measuring the temperature at which the normal force rises. Any measuring device can be used as long as it is capable of controlling the measurement temperature and measuring the normal stress, and a rheometer, for example, can be used. The expansion ratio of the substrate 10 containing expandable graphite is preferably 3 times or more, and more preferably 10 times or more. The upper limit of the expansion ratio is not particularly limited, but is, for example, 70 times, and preferably 50 times. When a plurality of liners 20 and cores 30 with different expansion ratios are used as the substrate 10, the expansion ratio should be selected within the above range. The expansion ratio can be calculated by feeding a test piece of the substrate 10 into an electric furnace, heating it at 600°C for 30 minutes, measuring the thickness of the test piece, and then dividing the thickness by (thickness of the test piece after heating) / (thickness of the test piece before heating).

[0027] Expandable graphite is produced by treating powder of natural flake graphite, pyrolytic graphite, kish graphite, or the like with an inorganic acid such as concentrated sulfuric acid, nitric acid, or selenic acid, and a strong oxidizing agent such as concentrated nitric acid, perchloric acid, perchlorates, permanganates, dichromates, or hydrogen peroxide to produce a graphite intercalation compound. The produced expandable graphite is a crystalline compound that maintains the layered structure of carbon. The expandable graphite used in the present invention may be one obtained by treating the expandable graphite with an acid and then neutralizing it with ammonia, an aliphatic lower amine, an alkali metal compound, an alkaline earth metal compound, or the like. Examples of the aliphatic lower amine include monomethylamine, dimethylamine, trimethylamine, ethylamine, propylamine, and butylamine. Examples of the alkali metal compounds and alkaline earth metal compounds include hydroxides, oxides, carbonates, sulfates, and organic acid salts of potassium, sodium, calcium, barium, magnesium, and the like.

[0028] The particle size of the expandable graphite is not particularly limited, but is preferably in the range of 20 to 200 mesh. If the particle size is equal to or greater than the lower limit, the degree of expansion of the graphite tends to increase. On the other hand, by setting the particle size equal to or less than the upper limit, the dispersibility when kneading with other materials of the substrate 10 is improved, and moldability is improved.

[0029] The content of expandable graphite in the substrate 10 is preferably 5% by mass or more, more preferably 15% by mass or more, and even more preferably 25% by mass or more. When the content of expandable graphite in the substrate 10 is equal to or greater than the above-mentioned lower limit, the expandable graphite can be reliably expanded by heating in a fire, resulting in good fire resistance. Furthermore, the content of expandable graphite in the substrate 10 is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. When the content of expandable graphite in the substrate 10 is equal to or less than the above-mentioned upper limit, the formability of the substrate 10 is good, and production efficiency can be improved. In addition, the content ratio of expandable graphite in the base material 10 means the content ratio of expandable graphite in the base material containing expandable graphite when a portion of the base material 10 constituting the cardboard 1 contains expandable graphite.

[0030] <Flame retardant> The substrate 10 preferably contains at least one of a boron-based flame retardant and a phosphorus-based flame retardant. The boron-based flame retardant and the phosphorus-based flame retardant are preferably contained inside the base paper that forms the substrate 10, and are preferably contained so as to be impregnated into the base paper, for example. By being impregnated into the base paper, the flame retardant performance is more easily exhibited. Furthermore, from the viewpoint of making it easier to impregnate the base paper with the flame retardant in the process of manufacturing the base paper, the boron-based flame retardant and the phosphorus-based flame retardant are preferably water-soluble.

[0031] In the corrugated cardboard 1, the flame retardant may be contained in at least one of the liner 20 and the core 30 as the base material 10, but is preferably contained in the base material 10 that contains the expandable graphite. By containing a flame retardant in addition to the expandable graphite, the fire resistance of the base material 10 can be further improved.

[0032] Examples of boron-based flame retardants include sodium polyborate, borax, zinc borate, sodium tetraborate, sodium octaborate, and boric acid. Examples of phosphorus-based flame retardants include ammonium polyphosphate, ethylenediamine phosphate, aluminum phosphite, diammonium hydrogen phosphate, carbamate polyphosphate, monoguanidine phosphate, and sodium hexametaphosphate. As the flame retardant, the boron-based flame retardant and the phosphorus-based flame retardant may be used alone or in combination of two or more kinds. The content of the boron-based flame retardant and phosphorus-based flame retardant as flame retardants in the substrate 10 is preferably 1 to 30 mass %, more preferably 5 to 25 mass %, and even more preferably 8 to 20 mass %. In addition, when a portion of the substrate 10 constituting the corrugated board 1 contains a flame retardant, the content ratio of the flame retardant in the substrate containing the flame retardant means the content ratio of the flame retardant in the substrate containing the flame retardant.

[0033] <Other additives> The substrate 10 generally contains glue for adhering the pulp. The glue is not particularly limited, and glues commonly used in corrugated cardboard can be used, such as starches such as cornstarch, wheat starch, tapioca starch, and modified starch. The content of glue in the substrate 10 is not particularly limited, and is, for example, about 1 to 20% by mass, and preferably about 2 to 15% by mass.

[0034] In the present invention, various papermaking additives may be incorporated into the substrate 10 to the extent that they do not impair the intended effects of the present invention. For example, known additives such as retention aids, pigment dispersants, pH adjusters, thickeners, flow improvers, antifoaming agents, foam suppressors, release agents, penetrating agents, UV absorbers, antioxidants, preservatives, mildew inhibitors, fluorescent eliminators, pitch control agents, slime control agents, chemical fixatives such as aluminum sulfate, water-resistant agents such as polyamides, polyamines, and epichlorohydrin, fillers such as clay, talc, and calcium carbonate, basic dyes, acid dyes, anionic direct dyes, and cationic direct dyes may be added singly or in combination.

[0035] <Corrugated board manufacturing method> The manufacturing method of corrugated board includes a base paper manufacturing process and a base material laminating process, as described below.

[0036] 《Base material base paper manufacturing process》 In the base paper manufacturing process, first, raw materials for the base material, such as paper stock, glue, expandable graphite, and flame retardant, are prepared. Examples of raw materials for paper include recycled paper pulp and pulp (wood). Next, the waste paper pulp and pulp as paper raw materials are beaten as necessary to remove foreign matter to produce a fibrous raw material. The obtained fibrous raw material is dispersed in water to obtain a slurry, to which glue, expandable graphite, and a flame retardant are appropriately added and mixed to prepare a paper stock for the base paper. Next, the obtained stock is passed through a paper machine to make paper. The paper machine is not particularly limited, and known paper machines such as a Fourdrinier paper machine, a cylinder paper machine, a hybrid former, and a gap former can be used. A specific papermaking process involves spreading the stock on a wire in the wire part to form paper layers. The moisture content of the paper layers is then reduced in the press part. The moisture content of the paper layers is then further reduced by heating and drying in the dryer part to obtain base base paper. The obtained base base paper becomes base paper for the liner and core, which are the substrates. If the base base paper is liner base paper, it is recommended to perform a process to smooth the surface of the base base paper using a calender. If the base base paper is core base paper, it is recommended to perform a process to form the base base paper into a corrugated shape.

[0037] The basis weight of the liner base paper is not particularly limited, and is, for example, 10 to 800 g / m 2 It is preferable that the density is 20 to 700 g / m 2 More preferably, it is 30 to 600 g / m 2 It is more preferable that: The basis weight of the core raw paper is not particularly limited, and is, for example, 60 to 250 g / m 2 It is preferable that the thickness is 70 to 240 g / m 2 More preferably, it is 80 to 230 g / m 2 It is more preferable that:

[0038] <<Substrate lamination process>> First, adhesive is applied to one side of corrugated core paper, and liner paper is placed on top of the adhesive and pasted together to obtain single-faced corrugated board. Next, adhesive is applied to the other side of the resulting core raw paper for single-faced corrugated cardboard, and liner raw paper is placed on top of the adhesive and pasted together to obtain double-faced corrugated cardboard.

[0039] In the above-described method for manufacturing corrugated board, expandable graphite is contained in both the liner and the core as the base material. However, if the core does not contain expandable graphite, the base material of the base paper may be adjusted so that it does not contain expandable graphite.

[0040] <Application> The corrugated board of the present invention can be used, without particular limitation, as a building material such as a wall material for partition walls, a pillar, etc. Specifically, the corrugated board of the present invention can be used as a building material in places where fire resistance is required. [Example]

[0041] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0042] Details of each component used in each example and comparative example are as follows.

[0043] <Paper raw materials> ·Recycled paper pulp (recycled cardboard) Pulp (kraft pulp)

[0044] <glue> Cornstarch (manufactured by Oji Cornstarch Co., Ltd., product name: Cornstarch)

[0045] <Expandable graphite> Expandable graphite (manufactured by Air Water Corporation, product name: CA-60N, expansion starting temperature 220°C, expansion degree 200 times)

[0046] <Flame retardant> Sodium polyborate (manufactured by SOUFA, product name: Bestboron) Ammonium polyphosphate (Clariant Chemicals, product name: AP422) Ethylenediamine phosphate (manufactured by Albright Wilson, product name: Amguard EDAP) Aluminum phosphite (manufactured by Taihei Chemical Co., Ltd., product name: NSF)

[0047] [Example 1] The paper raw material used for the base material was prepared with a ratio of recycled pulp and virgin pulp of 90:10. Next, a fibrous raw material made of pulp as a paper raw material was dispersed in water to obtain a slurry, and each component was mixed with the slurry according to the formulation shown in Table 1 to prepare a stock for the liner base paper. Next, the obtained paper stock is sprayed onto the paper to make paper, and then the moisture content is reduced by pressing, and the paper is then heated and dried to further reduce the moisture content and produce linerboard (basis weight 150 g / m 2 The obtained liner base paper was further pressed to smooth the surface. In Example 1, in order to produce a corrugated board that does not contain expandable graphite in the core, a stock for the core base paper that does not contain expandable graphite was prepared when preparing the stock for the core base paper, and the obtained stock was similarly made into a core base paper (basis weight 120 g / m 2The resulting core raw paper was subjected to a corrugated treatment. Then, adhesive was applied to one side of the corrugated corrugating medium raw paper, and liner paper was placed on top of the adhesive and bonded together to obtain a single-faced corrugated board. Next, adhesive was applied to the other side of the obtained single-faced corrugated board, and liner paper was placed on top of the adhesive and bonded together to obtain a double-faced corrugated board as Example 1. The fire resistance of the double-faced corrugated cardboard obtained as Example 1 was evaluated. The results are shown in Table 1.

[0048] [Examples 2 to 7, Comparative Example 1] Double-sided corrugated board was obtained by the same manufacturing method as in Example 1, except that the components were mixed according to the formulation shown in Table 1. The fire resistance of each of the obtained double-sided corrugated boards of each Example and Comparative Example was evaluated. The results are shown in Table 1.

[0049] [Measurement method] The methods for measuring and evaluating each physical property are as follows.

[0050] <Fire resistance> A burner (manufactured by Style Co., Ltd., product name: Esper 1, maximum temperature: 1,700°C, heat output: 3,174 kcal / h) was placed so that the distance from the tip of the double-sided cardboard for each example and comparative example was 10 mm. The burner was placed so that the flame would heat the center of the double-sided cardboard. The burner's heat was set to maximum, and after heating for 1 minute, the evaluation was performed based on the following criteria. (Evaluation criteria) 〇: No flames were emitted from the double-sided cardboard after the test ×: Flames erupted from the double-sided cardboard after the test was completed.

[0051] [Table 1]

[0052] As is clear from the results of the above Examples and Comparative Examples, the double-sided corrugated board of the Examples contains expandable graphite in the liner as a base material, and after being heated with a burner, the expandable graphite expands to form an insulating layer, thereby exhibiting fire resistance. In contrast, the double-faced corrugated board of Comparative Example 1 did not contain expandable graphite in the liner as a base material, so flames occurred without forming a heat insulating layer, and the fire resistance was insufficient. [Explanation of symbols]

[0053] 1 cardboard box 10 Base material 20 Liner 30 core 40 Adhesive

Claims

1. A corrugated board comprising a substrate containing expandable graphite.

2. 2. The cardboard according to claim 1, wherein the content of the expandable graphite in the base material is 5% by mass or more.

3. The corrugated board according to claim 1 or 2, wherein the base material contains at least one of a boron-based flame retardant and a phosphorus-based flame retardant.

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