Coated book paper and method for its production

Abstract

This invention provides a method for preparing coated notebook paper, comprising the following steps: S1, preparing base paper; S2, coating the surface of the base paper to form a coating layer, the coating layer comprising pigments and adhesives, wherein the adhesives comprise polyvinyl alcohol and enzyme-converted starch, comprising 100-110 parts by weight of pigment, 3-5 parts by weight of polyvinyl alcohol, and 10-14 parts by weight of enzyme-converted starch; S3, subjecting the base paper treated in step S2 to a second drying, calendering, and winding process to obtain the coated notebook paper. This application also provides coated notebook paper prepared by the above method. The coated notebook paper prepared by the method provided in this application has a fine surface, smooth writing, minimal pen wear, minimal ink bleeding, and rapid drying. It also possesses good coating strength and anti-bleed-through properties, making it particularly suitable as high-grade notebook paper.

Description

Technical Field

[0001] This invention relates to the field of papermaking technology, and in particular to a coated paper and its preparation method. Background Technology

[0002] Coated paper is a type of paper that has undergone surface coating treatment. It is widely used in printed materials due to its smooth, delicate surface and excellent printability. However, to achieve high gloss and opacity, conventional coated paper typically has a denser coating and uses a large amount of film-forming adhesives such as styrene-butadiene latex. This results in low surface porosity, making it difficult for ink to penetrate quickly when used in notebooks, exercise books, diaries, and other light-colored paper. This leads to slow ink drying after writing, making the ink easily smudged and staining the paper. Furthermore, the coating can cause a stiff writing feel, poor damping, and problems such as powdering and fuzzing when erasing with an eraser.

[0003] Therefore, how to provide a coated paper suitable for writing purposes is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] To address the technical problem that existing coated papers cannot meet writing requirements, this invention provides a method for preparing coated notebook paper; this invention also provides coated notebook paper prepared by the above method. The coated notebook paper prepared by the method provided in this application effectively solves the defects of coated paper when used in notebooks, such as pen tip damage, slow drying, and poor feel, without sacrificing its smooth and delicate advantages. The paper has a delicate surface, smooth and fluid writing, minimal pen tip wear, minimal ink bleeding, and rapid drying. It also possesses good coating strength and anti-bleed-through properties, making it particularly suitable as high-grade notebook paper.

[0005] A method for preparing coated paper includes the following steps: S1. Preparation of base paper; S2. A coating is formed on the surface of the base paper. The coating includes pigments and adhesives. The adhesives include polyvinyl alcohol and enzyme-converted starch. By weight, the adhesives include 100-110 parts by weight of pigment, 3-5 parts by weight of polyvinyl alcohol, and 10-14 parts by weight of enzyme-converted starch. S3. The paper processed in step S2 is dried, calendered, and wound to obtain coated paper.

[0006] Preferably, in step S2, the coating comprises 100-105 parts by weight of pigment, 3-4.5 parts by weight of polyvinyl alcohol, and 11-13 parts by weight of enzyme-converted starch.

[0007] Preferably, the pigment used in the coating is talc powder, and the particle size of the talc powder is d50≤2μm, d97≤10μm, and whiteness≥90%.

[0008] Preferably, the coating further includes 0.2-0.5 parts by weight of wetting agent, 0.3-0.8 parts by weight of lubricant, 0.3-0.8 parts by weight of water-resistant agent, 0.008-0.04 parts by weight of defoamer, and 0.008-0.02 parts by weight of dispersant.

[0009] Preferably, the wetting agent is any one of fatty alcohol polyoxyethylene ether and sodium dodecyl sulfate; The lubricant is any one of calcium stearate, sodium stearate, or polyoxyethylene stearate. The water-resistant agent is any one of zirconium ammonium carbonate, melamine-formaldehyde resin, and polyamide-polyurea resin; The defoamer is any one of polydimethylsiloxane, polyether-modified silicone oil, or higher carbon alcohol polyether; The dispersant is either sodium hexametaphosphate or sodium polyacrylate.

[0010] Preferably, the viscosity of the coating is 580-650 mPa·s, and metering rod coating is used with a coating amount of 14-16 g / m² on both sides. 2 .

[0011] Preferably, in step S1, the base paper is prepared according to the following method: The hardwood pulp is beaten to a freeness of 50-55°SR, and the auxiliary materials are added and mixed. Then, the pulp with a mass percentage concentration of 3-4% is diluted to a concentration of 0.6-0.9%. After sand and gas removal, sizing, fine screening, dewatering and forming, pressing, and first drying, the base paper is obtained.

[0012] Preferably, the hardwood pulp is alkaline hydrogen peroxide bleached poplar disc-milled mechanical pulp; and / or, The auxiliary material is an alkyl ketene dimer sizing agent, with a dosage of 2-4 kg oven-dry per ton of paper.

[0013] Preferably, the first drying process involves drying the paper until the moisture content is 6-7%.

[0014] A coated paper, prepared by any of the methods described above.

[0015] This application discloses a method for preparing coated paper, comprising the following steps: S1, preparing base paper; S2, coating the surface of the base paper to form a coating layer, the coating layer comprising pigments and adhesives, wherein the adhesives comprise polyvinyl alcohol and enzyme-converted starch, comprising 100-110 parts by weight of pigments, 3-5 parts by weight of polyvinyl alcohol, and 10-14 parts by weight of enzyme-converted starch; S3, subjecting the base paper treated in step S2 to a second drying, calendering, and winding process to obtain coated paper. The preparation method provided in this application abandons styrene-butadiene latex, which has strong film-forming properties and hinders penetration, and instead uses polyvinyl alcohol (PVA) and enzyme-converted starch as the main adhesive. Enzyme-converted starch has low viscosity and high solid content, and works synergistically with PVA to provide sufficient coating strength. Due to its weak hydrophilicity and film-forming properties, it forms a porous coating structure, which greatly promotes ink absorption and drying. This avoids the problem of ink penetration being difficult due to the dense, continuous film formed by styrene-butadiene latex, and the coating itself also has excellent air permeability and capillary action, achieving rapid ink absorption and fixation. Experimental verification shows that the coated notebook paper prepared by this invention meets the requirements of high-grade notebooks in key indicators such as basis weight, smoothness, surface strength, and breaking length.

[0016] The applicant also discovered that conventional coated paper is difficult to use with pointed writing instruments such as fountain pens and ballpoint pens, causing significant wear and shortening the lifespan of the pens. After research, the applicant changed the pigment used in the coating to talc, specifying the talc particle size as d50≤2μm, d97≤10μm, and whiteness ≥90%. By completely replacing traditional hard pigments such as heavy calcium carbonate with soft talc, wear on the pen tip (especially the ballpoint) is greatly reduced, extending the pen's lifespan. Furthermore, talc gives the paper a smooth and delicate feel, and combined with the optimized coating, writing is smooth and fluid, without scratching or slipping, while also exhibiting excellent ink-resistant properties.

[0017] This application preferably uses alkaline hydrogen peroxide bleached poplar disc mill mechanical pulp, combined with alkyl ketene dimer (AKD) surface sizing agent to prepare the base paper. This creates a loose and porous structure within the base paper, providing channels for rapid ink penetration and fundamentally solving the problem of slow drying, further improving the ink absorption rate. Preferably, the hardwood pulp is beaten to a freeness range of 50-55°SR. This freeness range ensures fiber bonding strength while maintaining the porous and loose structure of the base paper, laying the foundation for subsequent rapid ink penetration.

[0018] The preferred coating also includes wetting agents, water-resistant agents, defoamers, and dispersants. Wetting agents reduce the surface tension of the coating, improve its coverage and penetration into the base paper, and thus enhance the ink absorption of the finished paper. Lubricants improve the rheological properties of the coating and increase the surface strength of the paper; water-resistant agents give the paper coating the ability to resist moisture or humid environments; defoamers solve the problem of coating foaming; and dispersants disperse talc.

[0019] The wetting agent is preferably any one of fatty alcohol polyoxyethylene ether and sodium dodecyl sulfate. The lubricant is any one of calcium stearate, sodium stearate, and stearic acid polyoxyethylene grease. The water-repellent agent is any one of ammonium zirconium carbonate, melamine-formaldehyde resin, and polyamide-polyurea resin. The defoamer is any one of polydimethylsiloxane, polyether-modified silicone oil, and higher carbon alcohol polyether. The dispersant is any one of sodium hexametaphosphate and sodium polyacrylate. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] Example 1 A method for preparing coated paper includes the following steps: S1. 100% alkaline hydrogen peroxide bleached poplar disc-milled mechanical pulp (APMP pulp) is used, beaten to a freeness of 52°SR, and alkyl ketene dimer sizing agent is added (at a rate of 2.5 kg oven-dry / ton of paper) and mixed thoroughly. At this point, the pulp mass percentage concentration is 3.5%. Then, the pulp is diluted to a mass percentage concentration of 0.8%, and after sand and gas removal, sizing, fine screening, wire dewatering and forming, the pressing is carried out using two shoe presses with pressures of 700 N / cm and 900 N / cm respectively. Then, multi-cylinder drying is used, with the cylinder temperature gradually increased from 50℃ to 115℃ and then decreased back to 50℃, until the paper moisture content is 6.2%, thus obtaining the base paper. S2. A coating is formed on the surface of the base paper. The coating material includes: 100 parts by weight of pigment-coating grade talc (particle size d50≤2μm, d97≤10μm, whiteness≥90%), 3 parts by weight of polyvinyl alcohol (PVA), 11 parts by weight of enzyme-converted starch, 0.3 parts by weight of wetting agent fatty alcohol polyoxyethylene ether, 0.4 parts by weight of lubricant calcium stearate, 0.5 parts by weight of water-resistant agent ammonium zirconium carbonate, 0.02 parts by weight of defoamer polydimethylsiloxane, and 0.008 parts by weight of dispersant sodium polyacrylate. The coating viscosity is 600 mPa·s. Metering rod film coating is used, and the coating amount is 15 g / m² on both sides. 2 ; S3. The base paper processed in step S2 is dried, calendered, and wound to obtain coated sheet paper with a basis weight of 68 g / m². 2 .

[0022] According to the test results, the coated paper prepared in Example 1 has an ink absorption (K&N value) of 51%, a smoothness of 45s, a surface strength of 1.1m / s, a breaking length of 3900m, a sizing degree of 1.75mm, and a whiteness of 76%.

[0023] Example 2 A method for preparing coated paper includes the following steps: S1. 100% alkaline hydrogen peroxide bleached poplar disc-milled mechanical pulp (APMP pulp) is used, beaten to a freeness of 54°SR, and alkyl ketene dimer sizing agent is added (at a rate of 3.5 kg oven-dry / ton of paper) and mixed thoroughly. At this point, the pulp mass percentage concentration is 3.2%. Then, the pulp is diluted to a mass percentage concentration of 0.7%, and after sand and gas removal, sizing, fine screening, wire dewatering and forming, the pressing is carried out using two shoe presses at pressures of 750 N / cm and 850 N / cm respectively. Then, multi-cylinder drying is used, with the cylinder temperature gradually increased from 50℃ to 115℃ and then decreased back to 50℃, until the paper moisture content is 6.5%, thus obtaining the base paper. S2. A coating is formed on the surface of the base paper. The coating material includes: 100 parts by weight of pigment-coating grade talc (particle size d50≤2μm, d97≤10μm, whiteness≥90%), 4 parts by weight of polyvinyl alcohol (PVA), 13 parts by weight of enzyme-converted starch, 0.4 parts by weight of wetting agent fatty alcohol polyoxyethylene ether, 0.6 parts by weight of lubricant stearic acid polyoxyethylene ester, 0.7 parts by weight of water-resistant agent melamine-formaldehyde resin, 0.015 parts by weight of defoamer C12-18 high carbon alcohol polyether, and 0.015 parts by weight of dispersant sodium polyacrylate; the coating viscosity is 650 mPa·s, and the coating is applied by a doctor blade with a coating amount of 14 g / m² on both sides. 2 ; S3. The base paper treated in step S2 is subjected to a second drying, calendering, and winding process to obtain coated sheet paper with a basis weight of 78 g / m². 2 .

[0024] According to the test results, the coated paper prepared in Example 2 has an ink absorption (K&N value) of 48%, a smoothness of 55s, a surface strength of 1.3m / s, a breaking length of 4100m, a sizing degree of 1.65mm, and a whiteness of 77%.

[0025] Example 3 A method for preparing coated paper includes the following steps: S1. 100% alkaline hydrogen peroxide bleached poplar disc-milled mechanical pulp (APMP pulp) is used, beaten to a freeness of 50°SR, and alkyl ketene dimer sizing agent is added (at a rate of 3.8 kg oven-dry / ton of paper) and mixed thoroughly. At this point, the pulp mass percentage concentration is 3.8%. Then, the pulp is diluted to a mass percentage concentration of 0.65%, and after sand and gas removal, sizing, fine screening, wire dewatering and forming, the pressing is carried out using two shoe presses with pressures of 680 N / cm and 920 N / cm respectively. Then, multi-cylinder drying is used, with the cylinder temperature gradually increased from 50℃ to 115℃ and then decreased back to 50℃, until the paper moisture content is 6.8%, thus obtaining the base paper. S2. A coating is formed on the surface of the base paper. The coating material includes: 100 parts by weight of pigment-coating grade talc (particle size d50≤2μm, d97≤10μm, whiteness≥90%), 4.5 parts by weight of polyvinyl alcohol (PVA), 12.5 parts by weight of enzyme-converted starch, 0.45 parts by weight of wetting agent sodium dodecyl sulfate, 0.5 parts by weight of lubricant sodium stearate, 0.35 parts by weight of water-resistant agent polyamide-polyurea resin, 0.035 parts by weight of defoamer polydimethylsiloxane, and 0.012 parts by weight of dispersant sodium hexametaphosphate. The coating viscosity is 580 mPa·s. Air knife coating is used, and the coating amount is 16 g / m² on both sides. 2 ; S3. The base paper treated in step S2 is subjected to a second drying, calendering, and winding process to obtain coated sheet paper with a basis weight of 85 g / m². 2 .

[0026] According to the test results, the coated paper prepared in Example 3 has an ink absorption (K&N value) of 55%, a smoothness of 50s, a surface strength of 0.9m / s, a breaking length of 3750m, a sizing degree of 1.85mm, and a whiteness of 75.5%.

[0027] Comparative Example A traditional coated pure paper formulation was used: the pigment was a mixture of heavy calcium carbonate and kaolin, and the adhesive was styrene-butadiene latex and starch. Paper with the same basis weight as in Example 1 was produced using the same method. The traditional coated paper formulation consisted of 75 parts by weight of 95-grade heavy calcium carbonate, 25 parts by weight of kaolin (sheet clay), 12 parts by weight of styrene-butadiene latex, 3 parts by weight of coated oxidized starch, 0.4 parts by weight of the lubricant calcium stearate, and 0.5 parts by weight of the water-resistant agent potassium zirconium carbonate.

[0028] The comparison revealed that the conventional coated pure paper (smoothness 48 seconds, ink absorption 18%, surface strength 0.9 m / s, breaking length 4025 m, sizing degree 1.50 mm, whiteness 78%) had a K&N value (ink absorption) of less than 20% (18%), an ink drying time exceeding 30 seconds (52 seconds), and noticeable wear on the pen tip ballpoint after continuous writing with a fountain pen under a microscope. In contrast, the paper prepared in the three embodiments of this invention had an ink drying time of less than 5 seconds, exhibited almost no wear on the pen tip, and demonstrated significantly better writing smoothness than the comparative example.

[0029] The above description is merely an embodiment of the present invention. It should be noted that those skilled in the art can make improvements without departing from the inventive concept of the present invention, but these improvements all fall within the protection scope of the present invention.

Claims

1. A method for preparing coated paper, characterized in that, Includes the following steps: S1. Preparation of base paper; S2. A coating is formed on the surface of the base paper. The coating includes pigments and adhesives. The adhesives include polyvinyl alcohol and enzyme-converted starch. By weight, the adhesives include 100-110 parts by weight of pigment, 3-5 parts by weight of polyvinyl alcohol, and 10-14 parts by weight of enzyme-converted starch. S3. The paper processed in step S2 is dried, calendered, and wound to obtain coated paper.

2. The method for preparing coated paper according to claim 1, characterized in that, In step S2, the coating comprises 100-105 parts by weight of pigment, 3-4.5 parts by weight of polyvinyl alcohol, and 11-13 parts by weight of enzyme-converted starch.

3. The method for preparing coated paper according to claim 1, characterized in that, The pigment used in the coating is talc powder, with a particle size of d50≤2μm, d97≤10μm, and whiteness ≥90%.

4. The method for preparing coated paper according to any one of claims 1-3, characterized in that, The coating also includes 0.2-0.5 parts by weight of wetting agent, 0.3-0.8 parts by weight of lubricant, 0.3-0.8 parts by weight of water-resistant agent, 0.008-0.04 parts by weight of defoamer, and 0.008-0.02 parts by weight of dispersant.

5. The method for preparing coated paper according to claim 4, characterized in that, The wetting agent is any one of fatty alcohol polyoxyethylene ether and sodium dodecyl sulfate; The lubricant is any one of calcium stearate, sodium stearate, or polyoxyethylene stearate. The water-resistant agent is any one of zirconium ammonium carbonate, melamine-formaldehyde resin, and polyamide-polyurea resin; The defoamer is any one of polydimethylsiloxane, polyether-modified silicone oil, or higher carbon alcohol polyether; The dispersant is either sodium hexametaphosphate or sodium polyacrylate.

6. The method for preparing coated paper according to claim 4, characterized in that, The coating viscosity is 580-650 mPa·s, and metering rod coating is used, with a coating amount of 14-16 g / m² on both sides. 2 .

7. The method for preparing coated paper according to any one of claims 1-3 and 5-6, characterized in that, In step S1, the base paper is prepared according to the following method: The hardwood pulp is beaten to a freeness of 50-55°SR, and the auxiliary materials are added and mixed. Then, the pulp with a mass percentage concentration of 3-4% is diluted to a concentration of 0.6-0.9%. After sand and gas removal, sizing, fine screening, dewatering and forming, pressing, and first drying, the base paper is obtained.

8. The method for preparing coated paper according to claim 7, characterized in that, Hardwood pulp is alkaline hydrogen peroxide bleached poplar disc-milled mechanical pulp; and / or, The auxiliary material is an alkyl ketene dimer sizing agent, with a dosage of 2-4 kg oven-dry per ton of paper.

9. The method for preparing coated paper according to claim 7, characterized in that, The first drying process is carried out until the paper moisture content is 6-7%.

10. A coated paper, characterized in that, The coated paper is prepared by the method described in any one of claims 1-9.