A high-strength composite core paperboard and a manufacturing method thereof

Abstract

The present invention provides a high-strength composite core paperboard and a manufacturing method thereof. The high-strength composite core paperboard comprises a surface layer, a bottom layer and a core layer located therebetween. The surface layer, the core layer and the bottom layer are bonded together by an adhesive. The bottom layer is made of bottom layer pulp, the core layer is made of core layer pulp, and the surface layer is made of surface layer pulp. The bottom layer pulp comprises OCC pulp and book pulp, the core layer comprises OCC pulp, and the surface layer comprises office waste paper pulp, book pulp, nano filler and cellulase. The present invention ensures good tightness and integrity among the surface layer, the core layer and the bottom layer through the mutual matching of the fibers contained in the surface layer, the core layer and the bottom layer, and the layers are not easy to be delaminated and have a large interlayer bonding force. In addition, nano fillers are added to the surface layer pulp to help fill the gaps between the fibers and enhance the density, strength and smoothness of the surface layer. A small amount of cellulase is also added to the surface layer pulp to remove tiny fiber hairs on the fibers, thereby improving the smoothness and brightness of the surface layer.

Description

Technical Field

[0001] The invention relates to the technical field of papermaking, and in particular to a high-strength composite core paperboard and a manufacturing method thereof. Background Art

[0002] Core paperboard is an industrial thick paperboard made from recycled waste paper. It is used as a base material in the packaging and printing industry to make wine boxes, gift boxes, cosmetics and other packaging boxes. Traditional wine boxes are made of core paperboard and white paper. The core paperboard has a high bulk thickness, but because of the addition of more wood fiber, the interlayer strength of the core paperboard is generally not higher than 250kpa (the industry standard is 190kpa), and the surface smoothness of the core paperboard is low due to the raw material ratio and molding relationship during the papermaking process. In addition, another disadvantage of ordinary gray paperboard as a composite paper is that the product color is yellowish or grayish, and the brightness value is low.

[0003] Therefore, there is an urgent need to develop a composite paperboard for high-end wine boxes with high strength, high smoothness and high brightness. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a high-strength composite core paperboard to solve the problems of low interlayer strength, uneven surface and low brightness value of the core paperboard in the prior art. At the same time, the present invention will also provide a method for manufacturing a high-strength composite core paperboard.

[0005] In order to achieve the above-mentioned object and other related objects, the present invention provides the following technical solutions:

[0006] According to a first aspect of the present invention, a high-strength composite core paperboard is provided, comprising a surface layer, a bottom layer and a core layer located therebetween, wherein the surface layer, the core layer and the bottom layer are bonded together by an adhesive, the bottom layer is made of bottom layer pulp, the core layer is made of core layer pulp, and the surface layer is made of surface layer pulp; the bottom layer pulp comprises OCC pulp and book pulp, the core layer comprises OCC pulp, and the surface layer comprises office waste paper pulp, book pulp, nanofiller and cellulase.

[0007] The present invention ensures good tightness and integrity among the surface layer, core layer and bottom layer through the mutual matching of the fibers contained in the surface layer, and is not easy to be delaminated. In addition, the present invention adds nano fillers to the surface layer slurry to help fill the gaps between the fibers and enhance the density and smoothness of the surface layer; a small amount of cellulase is also added to remove the tiny fiber hairs on the fibers, thereby improving the smoothness and brightness of the surface layer; the nano fillers and cellulase are combined with the office waste paper pulp and book paper pulp in the surface layer slurry to ensure the structural strength of the surface layer, as well as the brightness and soft color of the surface layer, thereby ensuring the appearance requirements of product packaging.

[0008] Furthermore, the surface layer slurry comprises 15-25 parts by weight of office waste paper pulp, 70-85 parts by weight of book pulp, 2-3 parts by weight of nano filler and 0.05-0.2 parts by weight of cellulase.

[0009] Furthermore, the nano filler includes at least one of nano calcium carbonate, nano barium titanate, nano cellulose, nano kaolin, and nano titanium dioxide.

[0010] Furthermore, the core layer slurry also includes carboxymethyl cellulose and a cationic surfactant. Carboxymethyl cellulose as a natural adhesive can enhance the bonding force between the core layer and the upper and lower layers, and can improve the structural strength of the core layer; the cationic surfactant helps the fiber flocculation of the core layer slurry during pulping and molding, improves the tear resistance of the core layer, and can enhance the water resistance of the paper and increase the bonding force of the fibers, thereby improving the interlayer bonding force.

[0011] Furthermore, the cationic surfactant is a quaternary ammonium salt surfactant, and the quaternary ammonium salt surfactant includes at least one of trimethylammonium sulfate, quaternized polyacrylamide, and benzyltrimethylammonium chloride.

[0012] Furthermore, the core layer slurry includes 95-99.5 parts by weight of OCC slurry, 0.3-1.5 parts by weight of carboxymethyl cellulose and 0.05-0.15 parts by weight of cationic surfactant.

[0013] Furthermore, the bottom slurry also includes nanosilver. Nanosilver can be evenly dispersed in the bottom slurry, giving the bottom layer the ability to sterilize and deodorize, and is more suitable for high-end packaging materials.

[0014] Furthermore, the bottom layer slurry includes 60-70 parts by weight of OCC slurry, 30-40 parts by weight of book pulp and 0.01-0.1 parts by weight of nano silver.

[0015] Furthermore, the beating degree of the surface layer slurry is between 30 and 34°SR; the beating degree of the core layer slurry is between 20 and 25°SR; and the beating degree of the bottom layer slurry is between 30 and 35°SR.

[0016] The beating degree will directly affect the performance and quality of each layer; a lower beating degree of the core layer can ensure sufficient fiber length, thereby ensuring the thickness and mechanical strength of the core layer, and increasing the bonding ability between the core layer and the bottom layer and the surface layer; a higher beating degree of the surface layer and the bottom layer can improve the surface smoothness and brightness of the core paperboard.

[0017] Furthermore, the adhesive is modified starch, which can provide good bonding strength and flexibility, and is environmentally friendly and easy to recycle.

[0018] Furthermore, the modified starch is obtained by modifying natural starch through a multifunctional cross-linking agent, which can significantly enhance the mechanical stability and shear resistance of the starch, and is particularly suitable for core paperboards that require high mechanical strength.

[0019] Furthermore, the multifunctional cross-linking agent includes at least one of epichlorohydrin, phosphoric acid and citric acid.

[0020] According to a further update, the modified starch is obtained by the following preparation method: the natural starch is completely dispersed in water, an alkaline solution is added to adjust the pH to 9-11, then 0.1-3.0wt% of a multifunctional cross-linking agent is added, and the mixture is fully reacted at 50-60°C, and then an acidic solution is added to adjust the pH to neutral to obtain the modified starch.

[0021] A second aspect of the present invention provides a method for manufacturing a high-strength composite core paperboard, comprising the following steps:

[0022] (1) Pulp preparation: preparing OCC pulp, book pulp and office waste paper pulp respectively;

[0023] (2) Slurry preparation: prepare the base slurry, core layer slurry and surface layer slurry in proportion;

[0024] (3) Papermaking: The slurry obtained above is sequentially subjected to dehydration forming in a mesh section, dehydration by squeezing in a press section, and drying in a drying section to obtain a bottom layer, a core layer, and a surface layer respectively;

[0025] (4) Bonding: Spraying modified starch between the core layer and the surface layer, and between the core layer and the bottom layer, and then pressing the bottom layer, the core layer and the surface layer with a pressing roller, and obtaining a core paperboard after drying;

[0026] (5) Post-treatment: The core paperboard is subjected to corona treatment, and then calendered, surface sizing and dried to obtain the high-strength composite core paperboard.

[0027] Among them, the present invention performs corona treatment on the core paperboard during the post-treatment process, which can significantly improve the free energy of the core paperboard surface, enhance the adhesion of the subsequent gluing, and make the surface smoother and brighter.

[0028] Furthermore, the sizing agent is cationic starch, and the sizing process is as follows:

[0029] name Hanging volume positive gsm Hanging volume gsm Solid content of positive resist (%) Adhesive solid content (%) Starch 0.2~0.3 0.5~0.6 10~15 8~12

[0030] As described above, the high-strength composite core paperboard and the manufacturing method thereof of the present invention have the following beneficial effects:

[0031] 1. The present invention ensures good tightness and integrity among the surface layer, core layer and bottom layer through the mutual matching of the fibers contained in the surface layer, core layer and bottom layer, and is not easy to be delaminated. The interlayer bonding force is large and greater than 428kPa. In addition, the present invention adds nanofillers to the surface layer slurry to help fill the gaps between the fibers and enhance the density and smoothness of the surface layer; a small amount of cellulase is also added to remove the tiny fiber hairs on the fibers, thereby improving the smoothness and brightness of the surface layer; the nanofillers and cellulase are combined with the office waste paper pulp and book pulp in the surface layer slurry to ensure the structural strength of the surface layer, as well as the brightness and soft hue of the surface layer, thereby ensuring the appearance requirements of product packaging.

[0032] 2. The present invention uses starch modified by a multifunctional cross-linking agent as an adhesive to bond the surface layer, the core layer and the bottom layer. The multifunctional cross-linking agent can introduce chemical bonds into starch molecules to form a stable network structure between the starch molecules and the fibers, thereby enhancing the bonding strength between the two, improving the interlayer bonding force of each layer, and significantly increasing the mechanical stability and shear resistance of the core paperboard.

[0033] 3. The present invention performs corona treatment on the core paperboard during the post-processing process, which can significantly increase the free energy of the core paperboard surface, enhance the adhesion of the subsequent gluing, and make the surface smoother and brighter. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It shows a schematic diagram of the structure of the high-strength composite core paperboard disclosed in Example 1 of the present invention.

[0035] Component number description:

[0036] 1. Surface layer; 2. Core layer; 3. Bottom layer. DETAILED DESCRIPTION

[0037] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0038] A modified starch is prepared by uniformly mixing natural starch with an appropriate amount of water to obtain starch slurry, adding sodium hydroxide to the starch slurry to adjust the pH to 10, then adding 1wt% of epichlorohydrin and 0.5wt% of phosphoric acid, reacting them fully at 50°C, and then adding hydrochloric acid to adjust the pH to neutral to obtain the modified starch.

[0039] Example 1

[0040] A high-strength composite core paperboard, the manufacturing method of which comprises the following steps:

[0041] (1) Pulp preparation: preparing OCC pulp, book pulp and office waste paper pulp respectively;

[0042] (2) Slurry preparation: preparing a bottom layer slurry, a core layer slurry and a surface layer slurry respectively in proportion; the surface layer slurry comprises 20 parts by weight of office waste paper pulp, 78 parts by weight of book pulp, 2 parts by weight of nano calcium carbonate and 0.1 parts by weight of cellulase; the core layer slurry comprises 99 parts by weight of OCC pulp, 1 part by weight of carboxymethyl cellulose and 0.1 parts by weight of trimethyl ammonium sulfate surfactant; the bottom layer slurry comprises 65 parts by weight of OCC pulp, 35 parts by weight of book pulp and 0.05 parts by weight of nano silver;

[0043] (3) Papermaking: The slurry obtained above is sequentially subjected to dehydration forming in a mesh section, dehydration by squeezing in a press section, and drying in a drying section to obtain a bottom layer 3, a core layer 2, and a surface layer 1, respectively;

[0044] (4) Bonding: Spraying the modified starch between the core layer and the surface layer, and between the core layer and the bottom layer, and then pressing the bottom layer, the core layer and the surface layer with a pressing roller, and obtaining a core paperboard after drying;

[0045] (5) Post-treatment: The core paperboard is subjected to corona treatment, and then calendered, surface sizing, and dried to obtain the high-strength composite core paperboard. The high-strength composite core paperboard comprises a surface layer 1, a bottom layer 3, and a core layer 2 located therebetween.

[0046] Example 2

[0047] A high-strength composite core paperboard, the manufacturing method of which comprises the following steps:

[0048] (1) Pulp preparation: preparing OCC pulp, book pulp and office waste paper pulp respectively;

[0049] (2) Slurry preparation: preparing a bottom layer slurry, a core layer slurry and a surface layer slurry respectively in proportion; the surface layer slurry comprises 20 parts by weight of office waste paper pulp, 78 parts by weight of book pulp, 1 part by weight of nano barium titanate, 1 part by weight of nano kaolin and 0.1 part by weight of cellulase; the core layer slurry comprises 99 parts by weight of OCC pulp, 1 part by weight of carboxymethyl cellulose and 0.1 part by weight of quaternized polyacrylamide surfactant; the bottom layer slurry comprises 65 parts by weight of OCC pulp, 35 parts by weight of book pulp and 0.05 parts by weight of nano silver;

[0050] (3) Papermaking: The slurry obtained above is sequentially subjected to dehydration forming in a mesh section, dehydration by squeezing in a press section, and drying in a drying section to obtain a bottom layer, a core layer, and a surface layer respectively;

[0051] (4) Bonding: Spraying the modified starch between the core layer and the surface layer, and between the core layer and the bottom layer, and then pressing the bottom layer, the core layer and the surface layer with a pressing roller, and obtaining a core paperboard after drying;

[0052] (5) Post-treatment: The core paperboard is subjected to corona treatment, and then calendered, surface sizing and dried to obtain the high-strength composite core paperboard.

[0053] Example 3

[0054] A high-strength composite core paperboard, the manufacturing method of which comprises the following steps:

[0055] (1) Pulp preparation: preparing OCC pulp, book pulp and office waste paper pulp respectively;

[0056] (2) Slurry preparation: preparing a bottom layer slurry, a core layer slurry and a surface layer slurry respectively in proportion; the surface layer slurry comprises 20 parts by weight of office waste paper pulp, 80 parts by weight of book pulp, 1 part by weight of nano calcium carbonate and 0.1 parts by weight of cellulase; the core layer slurry comprises 95 parts by weight of OCC pulp, 1 part by weight of carboxymethyl cellulose and 0.1 parts by weight of benzyltrimethylammonium chloride surfactant; the bottom layer slurry comprises 60 parts by weight of OCC pulp, 35 parts by weight of book pulp and 0.05 parts by weight of nano silver;

[0057] (3) Papermaking: The slurry obtained above is sequentially subjected to dehydration forming in a mesh section, dehydration by squeezing in a press section, and drying in a drying section to obtain a bottom layer, a core layer, and a surface layer respectively;

[0058] (4) Bonding: Spraying the modified starch between the core layer and the surface layer, and between the core layer and the bottom layer, and then pressing the bottom layer, the core layer and the surface layer with a pressing roller, and obtaining a core paperboard after drying;

[0059] (5) Post-treatment: The core paperboard is subjected to corona treatment, and then calendered, surface sizing and dried to obtain the high-strength composite core paperboard.

[0060] Comparative Example 1

[0061] A composite core paperboard, the manufacturing method of which comprises the following steps:

[0062] (1) Pulp preparation: preparing OCC pulp, book pulp and office waste paper pulp respectively;

[0063] (2) Slurry preparation: preparing a bottom layer slurry, a core layer slurry and a surface layer slurry respectively in proportion; the surface layer slurry comprises 20 parts by weight of office waste paper pulp, 78 parts by weight of book pulp and 2 parts by weight of nano calcium carbonate; the core layer slurry comprises 99 parts by weight of OCC pulp, 1 part by weight of carboxymethyl cellulose and 0.1 parts by weight of trimethyl ammonium sulfate surfactant; the bottom layer slurry comprises 65 parts by weight of OCC pulp, 35 parts by weight of book pulp and 0.05 parts by weight of nano silver;

[0064] (3) Papermaking: The slurry obtained above is sequentially subjected to dehydration forming in a mesh section, dehydration by squeezing in a press section, and drying in a drying section to obtain a bottom layer, a core layer, and a surface layer respectively;

[0065] (4) Bonding: Spraying the modified starch between the core layer and the surface layer, and between the core layer and the bottom layer, and then pressing the bottom layer, the core layer and the surface layer with a pressing roller, and obtaining a core paperboard after drying;

[0066] (5) Post-treatment: The core paperboard is subjected to corona treatment, and then calendered, surface sizing and dried to obtain a composite core paperboard.

[0067] Comparative Example 2

[0068] A composite core paperboard, the manufacturing method of which comprises the following steps:

[0069] (1) Pulp preparation: preparing OCC pulp, book pulp and office waste paper pulp respectively;

[0070] (2) Slurry preparation: preparing a bottom layer slurry, a core layer slurry and a surface layer slurry respectively in proportion; the surface layer slurry comprises 20 parts by weight of office waste paper pulp, 78 parts by weight of book pulp, 2 parts by weight of nano calcium carbonate and 0.1 parts by weight of cellulase; the core layer slurry comprises 99 parts by weight of OCC pulp, 1 part by weight of carboxymethyl cellulose and 0.1 parts by weight of trimethyl ammonium sulfate surfactant; the bottom layer slurry comprises 65 parts by weight of OCC pulp, 35 parts by weight of book pulp and 0.05 parts by weight of nano silver;

[0071] (3) Papermaking: The slurry obtained above is sequentially subjected to dehydration forming in a mesh section, dehydration by squeezing in a press section, and drying in a drying section to obtain a bottom layer, a core layer, and a surface layer respectively;

[0072] (4) Bonding: Spray unmodified starch between the core layer and the surface layer, and between the core layer and the bottom layer, and then use a pressing roller to press the bottom layer, the core layer and the surface layer together, and then dry to obtain a core paperboard;

[0073] (5) Post-treatment: The core paperboard is subjected to corona treatment, and then calendered, surface sizing and dried to obtain a composite core paperboard.

[0074] Comparative Example 3

[0075] A composite core paperboard, the manufacturing method of which comprises the following steps:

[0076] (1) Pulp preparation: preparing OCC pulp, book pulp and office waste paper pulp respectively;

[0077] (2) Slurry preparation: preparing a bottom layer slurry, a core layer slurry and a surface layer slurry respectively in proportion; the surface layer slurry comprises 20 parts by weight of office waste paper pulp, 78 parts by weight of book pulp, 2 parts by weight of nano calcium carbonate and 0.1 parts by weight of cellulase; the core layer slurry comprises 99 parts by weight of OCC pulp, 1 part by weight of carboxymethyl cellulose and 0.1 parts by weight of trimethyl ammonium sulfate surfactant; the bottom layer slurry comprises 65 parts by weight of OCC pulp, 35 parts by weight of book pulp and 0.05 parts by weight of nano silver;

[0078] (3) Papermaking: The slurry obtained above is sequentially subjected to dehydration forming in a mesh section, dehydration by squeezing in a press section, and drying in a drying section to obtain a bottom layer, a core layer, and a surface layer respectively;

[0079] (4) Bonding: Spraying the modified starch between the core layer and the surface layer, and between the core layer and the bottom layer, and then pressing the bottom layer, the core layer and the surface layer with a pressing roller, and obtaining a core paperboard after drying;

[0080] (5) Post-processing: calendering, surface sizing and drying the core paperboard to obtain the composite core paperboard.

[0081] Performance Testing

[0082] The high-strength composite core paperboards prepared in Examples 1 to 3 and the composite core paperboards prepared in Comparative Examples 1 to 3 were subjected to relevant performance tests, and the test results are shown in Table 1:

[0083] Table 1. Performance test results of Examples 1 to 3 and Comparative Examples 1 to 3

[0084]

[0085] According to the comparison between Example 1 and Comparative Example 1, the present invention can remove tiny fiber hairs on the fibers by adding cellulase to the surface layer slurry, thereby improving the smoothness of the surface layer, and can promote the close arrangement of fibers and reduce gaps, thereby improving the structural strength of the composite core paperboard.

[0086] According to the comparison between Example 1 and Comparative Example 2, the modification of the multifunctional cross-linking agent can introduce chemical bonds into the starch molecules, so that a stable network structure is formed between the starch molecules and the fibers, thereby enhancing the bonding strength between the two and improving the interlayer bonding force.

[0087] According to the comparison between Example 1 and Comparative Example 3, the corona treatment can significantly increase the free energy of the core paperboard surface, enhance the adhesion of the subsequent sizing, and make the surface of the core paperboard smoother and brighter.

[0088] In summary, the present invention ensures good tightness and integrity among the surface layer, core layer and bottom layer through the mutual matching of the fibers contained in the surface layer, core layer and bottom layer, and is not easy to be delaminated and has strong interlayer bonding force; in addition, nano fillers are added to the surface layer slurry to help fill the gaps between the fibers and enhance the density, strength and smoothness of the surface layer; a small amount of cellulase is also added to the surface layer slurry to remove the tiny fiber hairs on the fibers, thereby improving the smoothness and brightness of the surface layer. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0089] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A high-strength composite core paperboard, characterized in that: It comprises a surface layer, a bottom layer and a core layer located therebetween, wherein the surface layer, the core layer and the bottom layer are bonded together by an adhesive, the bottom layer is made of bottom layer slurry, the core layer is made of core layer slurry, and the surface layer is made of surface layer slurry; The bottom layer slurry comprises 60-70 parts by weight of OCC slurry, 30-40 parts by weight of book pulp and 0.01-0.1 parts by weight of nano silver; The core layer slurry comprises 95-99.5 parts by weight of OCC slurry, 0.3-1.5 parts by weight of carboxymethyl cellulose and 0.05-0.15 parts by weight of a cationic surfactant, wherein the cationic surfactant is a quaternary ammonium salt surfactant; The surface layer slurry comprises 15-25 parts by weight of office waste paper pulp, 70-85 parts by weight of book pulp, 2-3 parts by weight of nano filler and 0.05-0.2 parts by weight of cellulase, wherein the nano filler comprises at least one of nano calcium carbonate, nano barium titanate, nano cellulose, nano kaolin and nano titanium dioxide; The beating degree of the surface layer slurry is between 30 and 34°SR; the beating degree of the core layer slurry is between 20 and 25°SR; the beating degree of the bottom layer slurry is between 30 and 35°SR; The adhesive adopts modified starch, and the modified starch is obtained by modifying natural starch through a multifunctional cross-linking agent, and the multifunctional cross-linking agent comprises epichlorohydrin and phosphoric acid.

2. The high-strength composite core paperboard according to claim 1, characterized in that: The modified starch is obtained by the following preparation method: natural starch is completely dispersed in water, an alkaline solution is added to adjust the pH to 9-11, 0.1-3.0 wt% of a multifunctional cross-linking agent is added, the mixture is fully reacted at 50-60° C., and an acidic solution is added to adjust the pH to neutral to obtain the modified starch.

3. A method for manufacturing a high-strength composite core paperboard according to claim 1 or 2, characterized in that: The following steps are involved: (1) Pulp preparation: preparing OCC pulp, book pulp and office waste paper pulp respectively; (2) Slurry preparation: prepare the base slurry, core layer slurry and surface layer slurry in proportion; (3) Papermaking: The slurry obtained above is sequentially subjected to dehydration forming in a mesh section, dehydration by squeezing in a press section, and drying in a drying section to obtain a bottom layer, a core layer, and a surface layer respectively; (4) Bonding: Spraying modified starch between the core layer and the surface layer, and between the core layer and the bottom layer, and then pressing the bottom layer, the core layer and the surface layer with a pressing roller, and obtaining a core paperboard after drying; (5) Post-treatment: The core paperboard is subjected to corona treatment, and then calendered, surface sizing and dried to obtain the high-strength composite core paperboard.

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