Surface-foamed paper and paperboard coated with thermosensitive micro-foaming agent

Abstract

The present invention relates to surface-foamed paper and paperboard coated with a thermosensitive micro-foaming agent and, more specifically, to surface-foamed paper and paperboard that exhibit excellent shock absorption and buffering performance by coating the surface of paper with a foaming mixture comprising a micro-foaming agent and starch, and then foaming the micro-foaming agent through high-temperature drying. In addition, the present invention relates to eco-friendly surface-foamed paper and paperboard using a foam material that can volumetrically expand on the surface of paper and paperboard.

Description

Surface-foamed paper and paperboard coated with heat-sensitive microfoaming agent

[0001] The present invention relates to surface-foamed paper and paperboard coated with a heat-sensitive micro-foaming agent, and more particularly, to surface-foamed paper and paperboard exhibiting excellent shock absorption and cushioning performance by coating a foaming mixture containing a micro-foaming agent and starch on the surface of paper and then foaming the micro-foaming agent through a high-temperature drying process.

[0002]

[0003] The destruction of the ecosystem caused by discarded plastic-based cushioning and packaging materials is accelerating. Styrofoam and other plastic-based cushioning and packaging materials are non-biodegradable when disposed of in soil or the ocean, raising concerns that by 2050, the amount of plastic in the ocean will outnumber the number of fish. Cellulose-based pulp molds are widely used as an alternative to plastic-based cushioning and packaging materials. However, they require excessive volume and a large amount of waste paper fiber and pulp to achieve a cushioning effect, necessitating additional lightweighting methods.

[0004] Due to the limitations described above, cellulose-based pulp molds are widely used as a means of replacing Styrofoam and plastic-based cushioning materials and packaging materials. However, cushioning materials manufactured using the pulp mold method have problems such as increased unit cost of cushioning materials due to the use of excessive amounts of pulp, reduced shock absorption ability, which raises concerns about damage to packaged goods, and increased packaging volume due to excessive volume caused by spaces for providing cushioning performance.

[0005] Due to the above problems, there is a need to develop eco-friendly paper and cardboard using expandable foam materials.

[0006]

[0007] The present invention provides surface-foamed paper and paperboard coated with a heat-sensitive microfoaming agent, which is produced by coating a heat-sensitive microfoaming agent on the surface of paper and paperboard to solve the above-mentioned problems.

[0008] In addition, it is an object of the present invention to provide surface-foamed paper and paperboard exhibiting excellent shock absorption and cushioning performance, heat and sound insulation, heat insulation and electrical insulation effects, etc.

[0009] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the art from the description of the present invention.

[0010]

[0011] In order to achieve the above object, the present invention provides a surface-foamed paper coated with a heat-sensitive microfoaming agent, comprising: a paper base; and a foaming layer formed by coating a foaming mixture on the surface of the paper base and then foaming it; wherein the foaming mixture includes a microfoaming agent and starch in a gel state.

[0012] In the present invention, the foam layer is characterized in that it is formed by foaming the fine foaming agent.

[0013] In the present invention, the paper base is characterized in that it is at least one selected from the group consisting of natural virgin pulp, newspaper waste paper, magazine waste paper, kraft waste paper, corrugated cardboard waste paper, and foamed paper.

[0014] In the present invention, the foam layer is characterized in that it is formed on one or both sides of the surface of the paper base.

[0015] In the present invention, the foam mixture is applied to the surface of the paper base at a density of 15 to 45 g / m 2 It is characterized by being applied in an amount of .

[0016] In the present invention, the foaming mixture is characterized in that it comprises 5 to 40 wt% of the fine foaming agent and 60 to 95 wt% of the gelatinized starch relative to 100 wt% of the foaming mixture.

[0017] In the present invention, the fine foaming agent is characterized in that it is at least one selected from the group consisting of a water-dispersible acrylic fine foaming agent, a methacrylic fine foaming agent, and an acrylonitrile fine foaming agent.

[0018] In the present invention, the micro foaming agent is characterized in that it is a spherical particle having a diameter of 5 to 20 ㎛.

[0019] In the present invention, the micro foaming agent is characterized in that it foams at 80 to 150°C.

[0020] In the present invention, the starch is characterized by being gelatinized at 85 to 95°C.

[0021] In the present invention, the starch is characterized in that it is one selected from the group consisting of oxidized starch and cationic starch.

[0022] In the present invention, the starch is characterized by having a concentration of 10 to 40%.

[0023] In the present invention, the foaming mixture is characterized in that it additionally includes at least one selected from the group consisting of guar gum and a sizing agent.

[0024] In the present invention, the surface foam paper has a basis weight of 30 to 100 g / m 2 It is characterized by being.

[0025] The present invention provides a surface-foamed cardboard coated with a heat-sensitive microfoaming agent, comprising: a cardboard; and a foaming layer formed by coating a foaming mixture on the surface of the cardboard and then foaming it; wherein the foaming mixture comprises a microfoaming agent and starch in a gel state.

[0026]

[0027] By means of solving the above problem, the present invention can provide surface-foamed paper and paperboard coated with a heat-sensitive microfoaming agent, which is produced by coating a heat-sensitive microfoaming agent on the surface of paper and paperboard and foaming the surface.

[0028] In addition, the present invention can provide surface-foamed paper and paperboard exhibiting excellent shock absorption and cushioning performance, heat and sound insulation, heat insulation and electrical insulation effects.

[0029] In addition, the present invention can provide surface-foamed paper and paperboard that do not require the use of a large amount of pulp raw material as in a conventional pulp mold and do not require excessive volume to impart cushioning performance.

[0030] In addition, the present invention can provide environmentally friendly surface foamed paper and paperboard using a micro foaming agent and starch, which is an environmentally friendly polymer.

[0031] In addition, the present invention can provide surface-foamed paper and paperboard capable of forming a foam coating layer of coated paper and white paperboard, etc.

[0032] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0033]

[0034] Figure 1 is a drawing showing a method for manufacturing surface-foamed paper coated with a heat-sensitive micro-foaming agent according to the present invention.

[0035] Figure 2 is a drawing showing a surface foamed paper coated with a heat-sensitive microfoaming agent according to the present invention.

[0036] FIG. 3 is a drawing showing a surface sizing process of surface foam paper coated with a microfoaming agent using a size press according to the present invention.

[0037] FIG. 4 is a drawing showing SEM photographs of the shape of the microfoam agent of the surface foam paper coated with the microfoam agent according to the present invention (a) before the microfoam agent is foamed and (b) after the microfoam agent is foamed.

[0038] FIG. 5 is a drawing showing SEM photographs taken at 200 magnification of (a) a paper surface not coated with a foaming agent, (b) a surface foamed paper surface coated with a microfoaming agent, and (c) a surface foamed paper surface according to the present invention at 200 magnification and 500 magnification.

[0039] FIG. 6 is a drawing showing SEM photographs taken at 500 magnification of (a) the surface of a paper not coated with a foaming agent, (b) 500 magnification of a cross-section of a surface foamed paper coated with a microfoaming agent, and (c) 1,000 magnification according to the present invention.

[0040] Figure 7 is a drawing showing the change in foaming rate according to the application amount of the foaming agent of examples and comparative examples according to the present invention.

[0041] Figure 8 is a drawing showing surface roughness according to the application amount of the foaming agent of examples and comparative examples according to the present invention.

[0042] Figure 9 is a drawing showing the permeability according to the application amount of the foaming agent of the examples and comparative examples according to the present invention.

[0043] Figure 10 is a drawing showing the tensile strength according to the application amount of the foaming agent of examples and comparative examples according to the present invention.

[0044] Figure 11 is a drawing showing the tensile strength according to the application amount of the foaming agent of examples and comparative examples according to the present invention.

[0045] Fig. 12 is a drawing showing a surface foamed cardboard coated with a heat-sensitive micro-foaming agent according to the present invention.

[0046]

[0047] The terms used in this specification have been selected from widely used, current terms, taking into account the functions of the present invention. However, these terms may vary depending on the intentions of those skilled in the art, precedents, the emergence of new technologies, etc. Furthermore, in certain cases, terms may be arbitrarily selected by the applicant, in which case their meanings will be described in detail in the relevant description of the invention. Therefore, the terms used in this invention should not be defined simply as names, but rather based on their inherent meanings and the overall content of the present invention.

[0048] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0049] Numerical ranges are inclusive of the values ​​defined in the ranges above. Any maximum numerical limitation given throughout this specification includes any lower numerical limitation, as if that lower numerical limitation were explicitly stated. Any minimum numerical limitation given throughout this specification includes any higher numerical limitation, as if that higher numerical limitation were explicitly stated. Any numerical limitation given throughout this specification will include any better numerical range within the broader numerical range, as if that narrower numerical limitation were explicitly stated.

[0050]

[0051] Surface-foamed paper coated with heat-sensitive microfoaming agent

[0052] The present invention relates to surface-foamed paper coated with a heat-sensitive microfoaming agent.

[0053] The present invention relates to a surface-foamed paper coated with a heat-sensitive microfoaming agent, comprising: a paper base; and a foaming layer formed by coating a foaming mixture on the surface of the paper base and then foaming the foaming mixture; wherein the foaming mixture comprises a microfoaming agent and starch in a gel state.

[0054] The surface-foamed paper may be a paper that is coated and foamed on the surface of a paper base by mixing a natural adhesive, which is a gel-like starch, and a fine foaming agent. The surface-foamed paper may be capable of preventing the fine foaming agent from being retained in or escaping from the fiber network of the paper base.

[0055] In addition, the above-mentioned micro-foaming agent may be coated on the surface so as not to interfere with the bonding of cellulose pulp fibers constituting the paper, thereby maintaining the strength of the paper while forming a foam layer on the surface to improve the physical strength.

[0056] The above surface foam paper may provide excellent cushioning performance to the paper because the hydrocarbon inside the microfoam coated on the surface of the paper expands to 4 to 6 times its diameter and 40 to 60 times its volume at a temperature above an appropriate temperature, leaving a cavity structure with a shell thickness of about 0.05 to 0.5 ㎛. The above surface foam paper relates to surface foam paper having excellent cushioning performance by foaming the microfoam in a drying step. The above surface foam paper has the same basis weight (g / m 2 ) may have a large bulk.

[0057] In the present invention, the foam layer may be formed by foaming the fine foaming agent. As shown in Fig. 2, the surface foam paper exhibits excellent shock absorption due to the foam structure of the foam layer, and can replace cushioning corrugated cardboard such as flat corrugated cardboard, and can be used as wallpaper base paper, flooring paper, and steel plate interlayer paper for the purpose of shock absorption and insulation. In addition, the electrical insulation effect due to the foam structure is also improved, and can be used as an insulator between copper wires inside high-voltage and medium-low-voltage wires.

[0058] In the present invention, the paper base may be at least one selected from the group consisting of natural virgin pulp, newspaper waste paper, magazine waste paper, kraft waste paper, corrugated paper, and foamed paper, but is not limited thereto.

[0059] In the present invention, the foam layer may be formed on one or both sides of the surface of the paper base.

[0060] In the present invention, the foam mixture is applied to the surface of the paper base at a density of 15 to 45 g / m 2 It may be applied in an amount of 15 g / m of the foam mixture. 2 If applied in an amount less than 45 g / m, the foam layer may be formed very small, which may cause a problem in that the shock absorption and relaxation effect through the foam layer is reduced. 2 If applied in excess, the bonding strength with the paper base may be reduced.

[0061] In the present invention, the foaming mixture may contain 5 to 40 wt% of the fine foaming agent and 60 to 95 wt% of the gelatinized starch relative to 100 wt% of the foaming mixture. If the fine foaming agent is contained in an amount less than 5 wt%, the foaming effect may not be sufficiently exhibited, and if it is contained in an amount exceeding 40 wt%, the durability of the surface foamed paper produced may be reduced.

[0062] In the present invention, the fine foaming agent may be at least one selected from the group consisting of a water-dispersible acrylic fine foaming agent, a methacrylic fine foaming agent, and an acrylonitrile fine foaming agent.

[0063] In the present invention, the microfoaming agent may be a spherical particle having a diameter of 5 to 20 μm, but is not limited thereto. The microfoaming agent may expand to 80 to 100 μm after foaming to form a large number of cavities, thereby improving the lightweight performance of the foaming layer.

[0064] In the present invention, the microfoaming agent may be foamed at a temperature of 80 to 150°C, but is not limited thereto. When the microfoaming agent is heated to 80 to 150°C, the microfoaming agent may be foamed up to 4 to 6 times its diameter and up to 40 to 60 times its volume.

[0065] In the present invention, the starch may be gelatinized at 85 to 95°C. The gelatinized starch may serve as a type of carrier that prevents the fine foaming agent from detaching from the surface of the paper base after foaming.

[0066] In the present invention, the starch may be any one selected from the group consisting of oxidized starch and cationic starch. The starch may not only enhance the chemical bonding of the microfoaming agent with the paper base material to fix it, but may also improve the dry strength of the surface-foamed paper.

[0067] In the present invention, the starch may have a concentration of 10 to 40%. If the concentration of the starch is less than 10%, the viscosity of the starch may be low, which may cause a problem in which the bonding between the paper base material and the microfoaming agent is reduced. If the concentration of the starch exceeds 40%, the viscosity of the starch may be too high, which may cause a problem in which the paper exhibits high viscosity even after drying.

[0068] In the present invention, the foaming mixture may further include at least one selected from the group consisting of guar gum and a sizing agent. The sizing agent may be an alkyl ketene dimer. The alkyl ketene dimer may directly bond with the hydroxyl group (-OH) of cellulose to form a hydrophobic barrier film on the paper, thereby improving the water resistance of the surface foamed paper. The sizing agent may be included in an amount of 0.3 to 0.9 wt% based on 100 wt% of the dry weight of the starch, but is not limited thereto.

[0069] In the present invention, the surface foam paper has a basis weight of 30 to 100 g / m 2 It may be 30 to 100 g / m 2The low-weight surface foam paper can replace non-biodegradable packaging vinyl such as bubble wrap and cushioning corrugated board such as flat corrugated board, and can be used for wallpaper base paper and flooring paper for shock absorption and insulation purposes, steel plate interlayer paper, cardboard, etc. In addition, the electrical insulation effect due to the surface foam structure is also improved, so it can be used as an insulator between copper wires inside high-voltage and medium-low voltage wires.

[0070] In addition, the surface foam paper may exhibit excellent water resistance when used as a covering paper for fruits during fruit cultivation, and may help uniform coloring of fruits by reflecting sunlight due to the internal foam structure of the covering paper, prevent diseases and pests, exhibit a heat retention effect due to sudden temperature drops, and prevent damage to fruits due to external impact during transportation and storage after harvest.

[0071] In addition, the surface foam paper may have excellent heat and cold insulation effects when used on the outer surface of a paper cup base, and may improve the frictional resistance of the bottom surface of the paper cup, thereby minimizing user discomfort caused by slipping on a table.

[0072]

[0073] Method for manufacturing surface-foamed paper coated with a heat-sensitive microfoaming agent

[0074] The present invention relates to a method for manufacturing surface-foamed paper coated with a heat-sensitive microfoaming agent.

[0075] The present invention relates to a method for manufacturing surface-foamed paper coated with a heat-sensitive microfoaming agent, comprising the steps of: gelatinizing a starch solution to produce a gel; diluting the starch solution in the gel state to produce a starch dilution; adding and mixing a microfoaming agent to the starch dilution to produce a foaming mixture; coating the foaming mixture on the surface of a paper base; and drying the paper coated with the foaming mixture to foam the microfoaming agent.

[0076] The above manufacturing method may be a method of manufacturing surface-foamed paper by mixing a natural adhesive, which is a gel-state starch, and a fine foaming agent, coating and foaming the mixture on the surface of paper stock, and the like. The above method of manufacturing surface-foamed paper may prevent the fine foaming agent from being retained in or escaping from the fiber network of the paper stock.

[0077] In addition, the manufacturing method may be a method of coating the micro foaming agent on the surface of the paper base material so as not to interfere with the bonding of cellulose pulp fibers constituting the paper, thereby maintaining the strength of the paper and forming a foam layer on the surface to improve the physical strength.

[0078] The surface foam paper manufactured according to the above manufacturing method includes a paper base paper; and a foam layer formed by coating a foam mixture on the surface of the paper base paper and then foaming it; wherein the foam mixture may be a surface foam paper coated with a heat-sensitive microfoaming agent, the heat-sensitive microfoaming agent including a microfoaming agent and a gel-state starch.

[0079] In the present invention, the starch solution may be at least one selected from the group consisting of oxidized starch and cationic starch. The starch may not only enhance the chemical bonding of the microfoaming agent with the paper base material to fix it, but may also improve the dry strength of the surface-foamed paper.

[0080] In the present invention, the step of gelatinizing the starch solution to form a gel may be gelatinizing at a temperature of 85 to 95°C for 20 to 30 minutes. The starch gelatinized through this step may serve as a type of carrier that prevents the fine foaming agent from detaching from the surface of the paper base after foaming.

[0081] In the present invention, the step of preparing the starch dilution may be diluting the starch solution in a gel state to a concentration of 10 to 40%. If the starch concentration is diluted to less than 10%, the viscosity of the starch may be low, which may cause a problem in which the bonding between the paper base material and the microfoaming agent is reduced. If the starch is diluted to more than 40%, the viscosity of the starch may be too high, which may cause a problem in which the paper exhibits high viscosity even after drying.

[0082] In the present invention, the step of preparing the foam mixture may include adding 5 to 40 wt% of the fine foaming agent relative to 100 wt% of the foam mixture. If the fine foaming agent is added in an amount less than 5 wt%, the foaming effect may not be sufficiently achieved, and if it is added in an amount exceeding 40 wt%, the durability of the surface foamed paper produced may be reduced.

[0083] In the present invention, the step of preparing the foam mixture may further include a step of adding at least one selected from the group consisting of guar gum and a sizing agent. The sizing agent may be an alkyl ketene dimer. The alkyl ketene dimer may directly bond with a hydroxyl group (-OH) of cellulose to form a hydrophobic barrier film on the paper, thereby improving the water resistance of the surface foamed paper. The sizing agent may be added in an amount of 0.3 to 0.9 wt% relative to 100 wt% of the dry weight of the starch, but is not limited thereto.

[0084] In the present invention, the fine foaming agent may be at least one selected from the group consisting of a water-dispersible acrylic fine foaming agent, a methacrylic fine foaming agent, and an acrylonitrile fine foaming agent.

[0085] In the present invention, the microfoaming agent may be a spherical particle having a diameter of 5 to 20 μm, but is not limited thereto. The microfoaming agent may expand to 80 to 100 μm after foaming to form a large number of cavities, thereby improving the lightweight performance of the surface foamed paper.

[0086] In the present invention, the step of coating the foam mixture on the surface of the paper base paper may include the steps of: transporting the paper base paper to a size press; supplying the foam mixture to the size press; and coating the foam mixture on the surface of the paper base paper using the size press. The step of coating the foam mixture on the surface of the paper base paper may be coating through the size press as shown in Fig. 3, thereby suppressing an increase in unit price and improving the weight reduction of the paper base paper by using an appropriate amount of the foam mixture.

[0087] In the present invention, the step of foaming the fine foaming agent may be, but is not limited to, drying at 80 to 150°C. When the fine foaming agent is heated to 80 to 150°C, the fine foaming agent may be foamed up to 4 to 6 times its diameter and up to 40 to 60 times its volume.

[0088]

[0089] Surface-foamed cardboard coated with heat-sensitive microfoaming agent

[0090] The present invention relates to a surface-foamed cardboard coated with a heat-sensitive micro-foaming agent.

[0091] The present invention relates to a surface-foamed cardboard coated with a heat-sensitive microfoaming agent, comprising: a cardboard base; and a foaming layer formed by coating a foaming mixture on the surface of the cardboard base and then foaming the foaming mixture; wherein the foaming mixture comprises a microfoaming agent and starch in a gel state.

[0092] The surface-foamed cardboard may be a board that is coated and foamed by mixing a natural adhesive, which is a gel-state starch, and a fine foaming agent on the surface of the board. The surface-foamed cardboard may be capable of preventing the fine foaming agent from being retained in or escaping from the fiber network of the board.

[0093] In addition, the above-mentioned micro-foaming agent may be coated on the surface so as not to interfere with the bonding of cellulose pulp fibers constituting the cardboard, thereby maintaining the strength of the cardboard and forming a foam layer on the surface to improve the physical strength.

[0094] The above surface foamed cardboard may provide excellent cushioning performance to the cardboard because the hydrocarbon inside the microfoam coated on the surface of the cardboard expands to 4 to 6 times its diameter and 40 to 60 times its volume at a temperature above an appropriate temperature, leaving a cavity structure with a shell thickness of about 0.05 to 0.5 ㎛. The above surface foamed cardboard relates to foamed cardboard having excellent cushioning performance by foaming the microfoam in a drying step. The above surface foamed cardboard has the same basis weight (g / m 2 ) may have a large bulk.

[0095] In the present invention, the foam layer may be formed by foaming the fine foaming agent. As shown in Fig. 12, the surface foam cardboard exhibits excellent shock absorption due to the foam structure of the foam layer, and thus can replace cushioning corrugated cardboard such as flat corrugated cardboard, and can be used as wallpaper base paper, flooring paper, and steel plate interlayer paper for the purpose of shock absorption and insulation. In addition, the electrical insulation effect due to the foam structure is also improved, and thus can be used as an insulator between copper wires inside high-voltage and medium-low-voltage wires.

[0096] In the present invention, the foam layer may be formed on one or both sides of the surface of the cardboard.

[0097] In the present invention, the foam mixture is applied to the surface of the cardboard at a density of 15 to 45 g / m 2 It may be applied in an amount of 15 g / m of the foam mixture. 2 If applied in an amount less than 45 g / m, the foam layer may be formed very small, which may cause a problem in that the shock absorption and relaxation effect through the foam layer is reduced. 2 If applied in excess, the bonding strength with the cardboard may be reduced.

[0098] In the present invention, the foaming mixture may contain 5 to 40 wt% of the fine foaming agent and 60 to 95 wt% of the gelatinized starch relative to 100 wt% of the foaming mixture. If the fine foaming agent is contained in an amount less than 5 wt%, the foaming effect may not be sufficiently exhibited, and if it is contained in an amount exceeding 40 wt%, the durability of the foamed cardboard produced may be reduced.

[0099] In the present invention, the fine foaming agent may be at least one selected from the group consisting of a water-dispersible acrylic fine foaming agent, a methacrylic fine foaming agent, and an acrylonitrile fine foaming agent.

[0100] In the present invention, the microfoaming agent may be a spherical particle having a diameter of 5 to 20 μm, but is not limited thereto. The microfoaming agent may expand to 80 to 100 μm after foaming to form a large number of cavities, thereby improving the lightweight performance of the foaming layer.

[0101] In the present invention, the microfoaming agent may be foamed at a temperature of 80 to 150°C, but is not limited thereto. When the microfoaming agent is heated to 80 to 150°C, the microfoaming agent may be foamed up to 4 to 6 times its diameter and up to 40 to 60 times its volume.

[0102] In the present invention, the starch may be gelatinized at 85 to 95°C. The gelatinized starch may serve as a type of carrier that prevents the micro-foaming agent from detaching from the surface of the paperboard after foaming.

[0103] In the present invention, the starch may be any one selected from the group consisting of oxidized starch and cationic starch. The starch may not only enhance the chemical bonding of the microfoaming agent with the paperboard and thereby fix it, but may also improve the dry strength of the paperboard.

[0104] In the present invention, the starch may have a concentration of 10 to 40%. If the concentration of the starch is less than 10%, the viscosity of the starch may be low, which may cause a problem in which the bonding between the cardboard and the microfoaming agent is reduced. If the concentration of the starch exceeds 40%, the viscosity of the starch may be too high, which may cause a problem in which the cardboard exhibits high viscosity even after drying.

[0105] In the present invention, the foaming mixture may further include at least one selected from the group consisting of guar gum and a sizing agent. The sizing agent may be an alkyl ketene dimer. The alkyl ketene dimer may directly bond with the hydroxyl group (-OH) of cellulose to form a hydrophobic barrier film on the paperboard, thereby improving the water resistance of the surface foamed paperboard. The sizing agent may be included in an amount of 0.3 to 0.9 wt% relative to 100 wt% of the dry weight of the starch, but is not limited thereto.

[0106] In the present invention, the surface foam board has a basis weight of 100 to 300 g / m 2 It may be 100 to 300 g / m 2High-bay weight surface foam cardboard has excellent cushioning effect and can prevent damage to packaged goods. In addition, it can replace non-biodegradable packaging vinyl such as bubble wrap and cushioning cardboard such as flat cardboard, and can be used for wallpaper base paper and flooring paper, steel sheet, cardboard, etc. for shock-absorbing and insulating purposes.

[0107] Conventional high-basis-weight paperboards based on cellulose fibers experience a decrease in thickness due to hydrogen bonding between cellulose fibers during the pressing and drying processes of the papermaking process. To improve this, a middle layer (midlle or filler ply) is laminated with paperboard manufactured from bleached (chemical) thermomechanical pulp, or high-basis-weight paperboard is manufactured. However, as the thickness of the paperboard decreases, the stiffness of the paperboard decreases, which can cause significant problems in printing or packaging paper. Therefore, the foamed paperboard according to the present invention can be manufactured by laminating foamed paperboard in the middle layer instead of using thermomechanical pulp.

[0108] The above-mentioned foam board may be used as a corrugated board and back liner as shown in (b) of Fig. 12 when manufacturing corrugated board including a corrugated core as shown in (a) of Fig. 12, and may not only improve the cushioning effect but also simplify the cardboard manufacturing process. In particular, when the above-mentioned foam board is used as a corrugated core having a corrugation height of 1.2 mm or less, such as an E-corrugation of corrugated board, the compressive strength and cushioning effect of the corrugated board may be improved.

[0109]

[0110] Method for manufacturing surface-foamed cardboard coated with a heat-sensitive microfoaming agent

[0111] The present invention relates to a method for manufacturing a surface-foamed cardboard coated with a heat-sensitive micro-foaming agent.

[0112] The present invention relates to a method for manufacturing a surface-foamed cardboard coated with a heat-sensitive microfoaming agent, comprising the steps of: gelatinizing a starch solution to produce a gel; diluting the starch solution in the gel state to produce a starch dilution; adding and mixing a microfoaming agent into the starch dilution to produce a foaming mixture; coating the foaming mixture on the surface of cardboard; and drying the cardboard coated with the foaming mixture to foam the microfoaming agent.

[0113] The above manufacturing method may be a method of manufacturing surface-foamed cardboard by mixing a natural adhesive, which is a gel-state starch, and a fine foaming agent, coating and foaming the mixture on the surface of the cardboard. The above method of manufacturing surface-foamed cardboard may prevent the fine foaming agent from being retained in or escaping from the fiber network of the cardboard.

[0114] In addition, the manufacturing method may be a method of coating the micro foaming agent on the surface of the cardboard so as not to interfere with the bonding of cellulose pulp fibers constituting the cardboard, thereby maintaining the strength of the cardboard and forming a foam layer on the surface to improve the physical strength.

[0115] The surface foamed cardboard manufactured according to the above manufacturing method includes: cardboard; and a foam layer formed by coating a foam mixture on the surface of the cardboard and then foaming it; wherein the foam mixture may be a surface foamed cardboard coated with a heat-sensitive microfoaming agent, the microfoaming agent including a microfoaming agent and a gel-state starch.

[0116] In the present invention, the starch solution may be at least one selected from the group consisting of oxidized starch and cationic starch. The starch may not only enhance the chemical bonding of the microfoaming agent with the paperboard and thereby fix it, but may also improve the dry strength of the paperboard.

[0117] In the present invention, the step of gelatinizing the starch solution to form a gel may be gelatinizing at a temperature of 85 to 95°C for 20 to 30 minutes. The starch gelatinized through this step may serve as a type of carrier that prevents the fine foaming agent from detaching from the surface of the cardboard after foaming.

[0118] In the present invention, the step of preparing the starch dilution may be diluting the starch solution in a gel state to a concentration of 10 to 40%. If the starch concentration is diluted to less than 10%, the viscosity of the starch may be low, which may cause a problem in which the bonding between the cardboard and the microfoaming agent is reduced. If the starch is diluted to more than 40%, the viscosity of the starch may be too high, which may cause a problem in which the cardboard exhibits a high viscosity even after drying.

[0119] In the present invention, the step of preparing the foam mixture may include adding 5 to 40 wt% of the fine foaming agent relative to 100 wt% of the foam mixture. If the fine foaming agent is added in an amount less than 5 wt%, the foaming effect may not be sufficiently achieved, and if it is added in an amount exceeding 40 wt%, the durability of the foamed cardboard produced may be reduced.

[0120] In the present invention, the step of preparing the foam mixture may further include a step of adding at least one selected from the group consisting of guar gum and a sizing agent. The sizing agent may be an alkyl ketene dimer. The alkyl ketene dimer may directly bind to a hydroxyl group (-OH) of cellulose to form a hydrophobic barrier film on the paperboard, thereby improving the water resistance of the surface foamed paperboard. The sizing agent may be added in an amount of 0.3 to 0.9 wt% relative to 100 wt% of the dry weight of the starch, but is not limited thereto.

[0121] In the present invention, the fine foaming agent may be at least one selected from the group consisting of a water-dispersible acrylic fine foaming agent, a methacrylic fine foaming agent, and an acrylonitrile fine foaming agent.

[0122] In the present invention, the microfoaming agent may be a spherical particle having a diameter of 5 to 20 μm, but is not limited thereto. The microfoaming agent may expand to 80 to 100 μm after foaming to form a large number of cavities, thereby improving the lightweight performance of the foamed cardboard.

[0123] In the present invention, the step of coating the foam mixture on the surface of cardboard may include the steps of: transporting the cardboard to a size press; supplying the foam mixture to the size press; and coating the foam mixture on the surface of the cardboard using the size press. The step of coating the foam mixture on the surface of the cardboard may be coating through the size press as shown in Fig. 3, thereby suppressing an increase in unit price and improving the weight reduction of the cardboard by using an appropriate amount of the foam mixture.

[0124] In the present invention, the step of foaming the fine foaming agent may be, but is not limited to, drying at 80 to 150°C. When the fine foaming agent is heated to 80 to 150°C, the fine foaming agent may be foamed up to 4 to 6 times its diameter and up to 40 to 60 times its volume.

[0125] Conventional high-basis-weight paperboards based on cellulose fibers experience a decrease in thickness due to hydrogen bonding between cellulose fibers during the pressing and drying processes of the papermaking process. To improve this, a middle layer (midlle or filler ply) is laminated with paperboard manufactured from bleached (chemical) thermomechanical pulp, or high-basis-weight paperboard is manufactured. However, as the thickness of the paperboard decreases, the stiffness of the paperboard decreases, which can cause significant problems in printing or packaging paper. Therefore, the foamed paperboard according to the present invention can be manufactured by laminating foamed paperboard in the middle layer instead of using thermomechanical pulp.

[0126] The above-mentioned foam board may be used as a corrugated board and back liner as shown in (b) of Fig. 12 when manufacturing corrugated board including a corrugated core as shown in (a) of Fig. 12, and may not only improve the cushioning effect but also simplify the cardboard manufacturing process. In particular, when the above-mentioned foam board is used as a corrugated core having a corrugation height of 1.2 mm or less, such as an E-corrugation of corrugated board, the compressive strength and cushioning effect of the corrugated board may be improved.

[0127]

[0128] Example

[0129] Hereinafter, examples of the present invention will be described in detail, but it is obvious that the present invention is not limited to the following examples.

[0130] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. The embodiments are provided solely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention. The present invention is defined solely by the scope of the claims.

[0131]

[0132] <Example 1> Surface-foamed paper coated with a heat-sensitive microfoaming agent

[0133] Oxidized starch with a concentration of 25% was gelatinized at 90 to 95°C for about 20 to 25 minutes and then cooled at a temperature of 40 to 50°C. 20 g of a fine foaming agent was mixed with the cooled oxidized starch to prepare a mixed solution. The mixed solution was applied at a size press at a dosage of 33 g / m. 2 The paper was applied to the surface of the paper base in a state adjusted to . The paper to which the mixed solution was applied was transferred to a drying device at a temperature of 100 to 150°C and then dried to foam the fine foaming agent, thereby manufacturing surface-foamed paper coated with a heat-sensitive fine foaming agent.

[0134]

[0135] <Example 2> 20 g / m 2 Surface foam paper applied with an amount of

[0136] The application amount of the above mixed solution is 20 g / m 2 Surface foam paper was manufactured in the same manner as in Example 1 except that the adjustment was made.

[0137]

[0138] <Comparative Example 1> Paper not coated with heat-sensitive microfoaming agent

[0139] Paper of similar thickness and size to Example 1 above was prepared.

[0140]

[0141] <Experimental Example 1> Surface Analysis of Surface-Foamed Paper

[0142] To analyze the surface of the surface foam paper of the present invention, the following experiment was performed.

[0143]

[0144] <Experimental Example 1-1> SEM analysis before and after microfoam foaming

[0145] The surface foam paper manufactured in Example 1 was analyzed by taking photographs before and after foaming of the microfoaming agent contained therein using a scanning electron microscope (SEM) at 1,000x magnification, and the results are shown in Fig. 4.

[0146] As shown in Fig. 4, the microfoaming agent included in the surface foaming paper of Example 1 showed a significant increase in diameter and volume by 4 to 6 times after foaming compared to before foaming.

[0147]

[0148] <Experimental Example 1-2> SEM analysis of paper surface with and without microfoaming agent

[0149] The surface of the surface-foamed paper manufactured in Example 1 was photographed using a scanning electron microscope (SEM) at 200 and 500 magnifications, and the surface of the paper manufactured in Comparative Example 1 was photographed using an SEM at 200 magnifications, and the results are shown in Fig. 5.

[0150] As shown in Fig. 5 (a), the surface of the paper not coated with the microfoaming agent of Comparative Example 1 showed a very dense texture due to bonding between the cellulose fibers of the paper. On the other hand, as shown in Figs. 5 (b) and (c), the surface of the surface-foamed paper coated with the microfoaming agent of Example 1 showed that the microfoaming agent particles were foamed on the paper surface and covered with large spherical particles, forming spherical foaming agent particles.

[0151]

[0152] <Experimental Example 1-3> SEM analysis of cross-sections of paper with and without microfoaming agent

[0153] The cross-section of the surface foam paper manufactured in Example 1 was photographed using a scanning electron microscope (SEM) at 200 and 1,000 magnifications, and the cross-section of the paper manufactured in Comparative Example 1 was photographed using an SEM at 500 magnifications, and the results are shown in Fig. 6.

[0154] As shown in Fig. 6 (a), the cross-section of the paper of Comparative Example 1 that was not coated with the microfoaming agent showed a very dense structure due to bonding between cellulose fibers. On the other hand, as shown in Figs. 6 (b), (c), and (d), the cross-section of the surface-foamed paper coated with the microfoaming agent of Example 1 showed the formation of honeycomb-shaped hollow cavities created by the foamed microfoaming agents.

[0155]

[0156] Through the above results, it was confirmed that the surface-foamed paper coated with the heat-sensitive microfoaming agent according to the present invention has microfoaming agents formed on the surface of the paper, and thus can exhibit cushioning effects such as shock absorption, heat and sound blocking, heat insulation, and electrical insulation effects.

[0157]

[0158] <Experimental Example 2> Analysis of physical properties of surface-foamed paper

[0159] To evaluate the physical properties of the surface foam paper of the present invention, the following experiments were conducted.

[0160]

[0161] <Experimental Example 2-1> Measurement of foaming rate of surface foam paper

[0162] The thickness of the paper manufactured in the above Examples 1 and 2 and Comparative Example 1 was measured in accordance with ISO 534, and the foaming rate of the paper was calculated by substituting the thickness of the paper before and after foaming of the micro-foaming agent included in the measured paper into [Mathematical Formula 1] below, and the results are shown in Fig. 7.

[0163] [Mathematical Formula 1]

[0164] Expansion ratio (%) = {[thickness of foam paper (㎛) - thickness of paper before foaming (㎛) / thickness of paper before foaming (㎛)] × 100

[0165] As shown in Fig. 7, the surface foam paper coated with the microfoaming agent of Examples 1 and 2 showed a high foaming rate compared to the paper not coated with the microfoaming agent of Comparative Example 1, and the coating rate of Example 2 was 17% and the coating rate of Example 3 was 150%, showing that the foaming rate increased as the coating amount of the mixture including the microfoaming agent increased.

[0166] Through the above results, it was confirmed that the surface foamed paper coated with the heat-sensitive micro-foaming agent according to the present invention exhibits an excellent foaming rate.

[0167]

[0168] <Experimental Example 2-2> Measurement of surface roughness of surface-foamed paper

[0169] The surface roughness of the paper manufactured in the above Examples 1 and 2 and Comparative Example 1 was measured according to ISO 8791-4, and the results are shown in Fig. 8.

[0170] As shown in Fig. 8, compared to the paper not coated with the microfoaming agent of Comparative Example 1, the surface-foamed paper of Examples 1 and 2 showed a reduced surface roughness as the oxidized starch applied together with the microfoaming agent filled the unevenness of the paper surface.

[0171] Through the above results, it was confirmed that the surface foamed paper coated with the heat-sensitive microfoaming agent according to the present invention exhibits low surface roughness and can be used as paper with improved frictional resistance.

[0172]

[0173] <Experimental Example 2-3> Measurement of air permeability of surface-foamed paper

[0174] The permeability of the paper manufactured in the above Examples 1 and 2 and Comparative Example 1 was measured according to ISO 5636-5, and the results are shown in Fig. 9.

[0175] As shown in Fig. 9, compared to the paper not coated with the microfoaming agent of Comparative Example 1, the surface-foamed paper of Examples 1 and 2 showed improved air permeability as the amount of the microfoaming agent added increased, and many pores were formed between the microfoaming agents as the microfoaming agent was foamed.

[0176] Through the above results, it was confirmed that the foam paper containing the heat-sensitive microfoaming agent according to the present invention exhibits high air permeability and can be used as paper with improved air permeability.

[0177]

[0178] <Experimental Example 2-4> Measurement of tensile strength of surface-foamed paper

[0179] The tensile strength of the paper manufactured in Examples 1 and 2 and Comparative Example 1 was measured according to ISO 1924-2, and the results are shown in Fig. 10.

[0180] As shown in Fig. 10, compared to the paper not coated with the microfoaming agent of Comparative Example 1, the surface foamed paper of Examples 1 and 2 showed that the surface strength of the paper was improved by the starch-based surface sizing coating as the amount of the microfoaming agent added increased, resulting in a partial increase in tensile strength.

[0181] Through the above results, it was confirmed that the foamed paper including the heat-sensitive microfoaming agent according to the present invention can be used as paper exhibiting improved physical stability by exhibiting high tensile strength.

[0182]

[0183] <Experimental Example 2-5> Measurement of tear strength of surface foam paper

[0184] The tensile strength of the paper manufactured in the above Examples 1 and 2 and the above Comparative Example 1 was measured according to ISO 1974, and the results are shown in Fig. 11.

[0185] As shown in Fig. 11, compared to the paper not coated with the microfoaming agent of Comparative Example 1, the surface foamed paper of Examples 1 and 2 showed that the surface strength of the paper was improved by the starch-based surface sizing coating as the amount of the microfoaming agent added increased, and thus the tear strength was increased somewhat.

[0186] Through the above results, it was confirmed that the foamed paper containing the heat-sensitive microfoaming agent according to the present invention can be used as paper exhibiting improved physical stability by exhibiting high tensile strength.

[0187]

[0188] The surface foamed paper and paperboard according to the present invention can be used as a cushioning packaging material, wire insulation paper, over-paper, wallpaper, disposable paper cup and cup holder base paper, coated paper, white paper, etc. that can replace bubble wrap depending on the foaming ratio.

[0189] Through this, it is expected that packaging materials that depend on plastic or Styrofoam can be replaced with eco-friendly cushioning materials, thereby contributing to alleviating environmental pollution problems caused by non-biodegradable packaging materials.

Claims

1. Paper base; and A foam layer formed by coating a foam mixture on the surface of the above paper and then foaming it; The above foam mixture is, Surface-foamed paper coated with a heat-sensitive microfoaming agent, comprising a microfoaming agent and a gel-state starch.

2. In paragraph 1, The above foam layer is, Surface-foamed paper coated with a heat-sensitive microfoaming agent, characterized in that the microfoaming agent is formed by foaming.

3. In paragraph 1, The above paper source is, Paper coated with a heat-sensitive microfoaming agent, characterized by being at least one selected from the group consisting of natural virgin pulp, old newspaper, old magazine, kraft paper, old corrugated cardboard, and foamed paper.

4. In paragraph 1, The above foam layer is, Surface-foamed paper coated with a heat-sensitive micro-foaming agent, characterized in that it is formed on one or both sides of the surface of the above-mentioned paper.

5. In paragraph 1, The above foam mixture is, 15 to 45 g / m on the surface of the above paper 2 Surface foamed paper coated with a heat-sensitive microfoaming agent, characterized in that it is applied in an amount of .

6. In paragraph 1, The above foam mixture is, Surface-foamed paper coated with a heat-sensitive microfoaming agent, characterized in that it comprises 5 to 40 wt% of the microfoaming agent and 60 to 95 wt% of the gelatinized starch relative to 100 wt% of the foaming mixture.

7. In paragraph 1, The above fine foaming agent is, Surface-foamed paper coated with a heat-sensitive microfoaming agent, characterized in that the surface-foaming paper comprises at least one selected from the group consisting of the above-mentioned water-dispersible acrylic microfoaming agent, methacrylic microfoaming agent, and acrylonitrile microfoaming agent.

8. In paragraph 1, The above fine foaming agent is, Surface-foamed paper coated with a heat-sensitive microfoaming agent, characterized in that the particles are spherical particles having a diameter of 5 to 20 ㎛.

9. In paragraph 1, The above fine foaming agent is, Surface-foamed paper coated with a heat-sensitive micro-foaming agent, characterized in that it foams at 80 to 150°C.

10. In paragraph 1, The above starch, Surface-foamed paper coated with a heat-sensitive micro-foaming agent, characterized by gelantinization at 85 to 95°C.

11. In paragraph 1, The above starch, Surface-foamed paper coated with a heat-sensitive microfoaming agent, characterized in that the surface-foaming paper is one selected from the group consisting of oxidized starch and cationic starch.

12. In paragraph 1, The above starch, Surface-foamed paper coated with a heat-sensitive microfoaming agent, characterized in that the concentration is 10 to 40%.

13. In paragraph 1, The above foam mixture is, Surface-foamed paper coated with a heat-sensitive microfoaming agent, characterized in that it additionally comprises at least one selected from the group consisting of guar gum and sizing agents.

14. In paragraph 1, The above surface foam paper, Weight 30 to 100 g / m 2 Surface-foamed paper coated with a heat-sensitive microfoaming agent, characterized by:

15. Cardboard; and A foam layer formed by coating a foam mixture on the surface of the above cardboard and then foaming it; The above foam mixture is, Surface-foamed cardboard coated with a heat-sensitive microfoaming agent, comprising a microfoaming agent and a gel-state starch.

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