Highly transparent tracing paper and use in high-end packaging paper

Abstract

The present application relates to the technical field of papermaking, and particularly relates to a coating material for a high-transparency drawing paper surface coating layer, a high-transparency drawing paper prepared by the coating material and application of the high-transparency drawing paper in high-end packaging paper. The coating material for the high-transparency drawing paper surface coating layer is composed of the following components in percentage by mass: polyvinyl alcohol 10-20%, nano-silicon dioxide 2.0-8.0%, glycerol 1.0-5.0%, polyurethane particles 1.0-3.0%, natural resin 0.5-3.0%, and water in a remainder to 100%. By using the coating material of the present application on the surface coating layer of the drawing paper, the phenomenon of crease whitening of the high-transparency drawing paper is improved, and the composite requirements of transparency, flexibility and environmental protection of the high-transparency drawing paper in the high-end packaging field are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of papermaking, in particular to a coating for the surface coating of high-transparency drawing paper, and a high-transparency drawing paper prepared by the coating and its application in high-end packaging paper. BACKGROUND

[0002] Among the varieties of paper, the use of a special paper, drawing paper, is very unique. Drawing paper was once indispensable to engineering drawing. Before the popularization of computers, the best way to preserve engineering drawings for a long time was to make blueprints. To make blueprints from drawings drawn by engineers, it is necessary to use drawing paper for tracing. Moreover, because drawing paper has a very small shrinkage rate and good water resistance, some nautical charts are also made of drawing paper.

[0003] With the popularization of computer drawing and the use of CAD and other drawing tools, computer drawing has basically replaced manual drawing, and the use of drawing printers has declared that drawing paper has basically left the drawing industry.

[0004] However, with the improvement of people's living standards, the packaging requirements for gifts and high-end commodities are becoming higher and higher. The unique appearance and printing performance of drawing paper have been recognized by the packaging industry and introduced into the high-end packaging industry. Its nearly transparent paper quality, matte texture, superior printing performance, and appropriate stiffness have successfully replaced plastic and cartons in the high-end application field of the packaging industry. At the same time, as printed matter such as trademarks, it is very suitable for use in high-end gift, cake, moon cake and cigarette trademark printing.

[0005] When drawing paper is used in the high-end packaging industry, it has always been a crushing presence, but when it is used in the outermost layer of packaging, there is always a problem that cannot be overcome. Because the beating degree of the raw material used for drawing paper is very high, generally above 85°SR, to achieve a nearly transparent effect, the fiber brought by high consistency has basically disappeared. When the paper is folded, a light white line will be left at the crease, and at the corner, because it needs to be folded in two directions, there will be an obvious white spot at the overlapping part, which affects the appearance of the product. Of course, if this bag or box is used for the inner layer, there will be no effect, but if it is used for the outer layer, it will greatly affect the grade of the product. SUMMARY

[0006] To solve the above technical problems, the purpose of the present application is to provide a coating for the surface coating of high-transparency drawing paper. By applying the coating of the present application to the surface of drawing paper, the white crease phenomenon of high-transparency drawing paper is improved, meeting the combined requirements of transparency, flexibility and environmental protection of high-transparency drawing paper in the high-end packaging field.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A coating for high-transparency tracing paper surface coating, the coating is composed of the following components in percentage by mass:

[0009] Polyvinyl alcohol: 10-20%

[0010] Nano-silica: 2.0-8.0%

[0011] Glycerol: 1.0-5.0%

[0012] Polyurethane particles: 1.0-3.0%

[0013] Natural resin: 0.5-3.0%

[0014] Water: balance to 100%.

[0015] Preferably, the coating is composed of the following components in percentage by mass:

[0016] Polyvinyl alcohol: 12-18%

[0017] Nano-silica: 3.0-5.0%

[0018] Glycerol: 2.0-4.0%

[0019] Polyurethane particles: 1.5-2.5%

[0020] Natural resin: 1.0-2.0%

[0021] Water: balance to 100%.

[0022] Preferably, the natural resin uses one or more of rosin, oil pine resin, and gelatin.

[0023] Preferably, the polyurethane particles are between 1 micrometer and 10 micrometers. The particle size of the polyurethane particles is between 1 micrometer and 10 micrometers. Smaller particles (close to or below 1 micrometer) are more conducive to maintaining the transparency of the coating and the final paper; larger particles (more than 10 micrometers) can cause visible opaque points in the coating, affecting the overall transparency of the paper. Moderate particle size helps to improve the mechanical strength and elasticity of the coating.

[0024] Further, the present application also provides a preparation method of the coating, which comprises the following steps:

[0025] 1) Pretreatment

[0026] The nano-silica and polyurethane particles are pre-dispersed using a ball mill, and the ball milling time is about 1-2 hours to ensure uniform particle size and uniform dispersion;

[0027] 2) Dissolve PVA

[0028] Heat water to 50°C, slowly add PVA powder to preheated water, while using a high-speed stirrer, 300-500 rpm stirring until completely dissolved;

[0029] 3) Add nano-SiO2 and polyurethane particles

[0030] Method: Slowly add pre-treated nano-SiO2 and polyurethane particles to the PVA solution, continue to stir at 500-800 rpm for 10-20 minutes to ensure thorough mixing;

[0031] 4) Introduce glycerol and natural resin

[0032] First add glycerol, continue stirring for 5 minutes, then slowly add rosin, stir until completely dissolved, maintain the temperature at 50°C to facilitate dissolution;

[0033] 6) Homogenization treatment

[0034] Use a high-shear homogenizer to treat the mixture, set the speed to 8000-10000 rpm, duration 5-10 minutes;

[0035] 7) Cooling and adjustment

[0036] Let the mixture cool to room temperature naturally, adjust the final viscosity to adapt to different coating methods.

[0037] Further, the present application also provides the use of the coating in the preparation of high-transparency tracing paper with improved crease whitening.

[0038] Further, the present application also provides a high-transparency tracing paper, the surface of the high-transparency tracing paper is coated with the coating.

[0039] Preferably, the pulp of the base paper of the high-transparency tracing paper is 60-80% bleached cotton pulp and 20-40% bleached bamboo pulp by mass percentage, and 2-4% nano-silicon dioxide and 5-10% polyvinyl alcohol are added to the total pulp weight to prepare the base paper.

[0040] Further, the present application also provides a preparation method of the high-transparency tracing paper, which comprises the following steps:

[0041] 1) Bleaching cotton pulp / bamboo pulp:

[0042] Use environmentally friendly bleaching agents such as hydrogen peroxide for bleaching treatment to ensure that the whiteness of the pulp reaches more than 90%;

[0043] 2) Refining:

[0044] Cotton / bamboo pulp is ground to 850SR using a refiner to ensure high fiber refinement and paper transparency;

[0045] 3) Filler and reinforcing agent addition:

[0046] Disperse nano-silica and polyvinyl alcohol evenly in the slurry, mix for 30 minutes using a high-speed mixer to ensure thorough integration;

[0047] 4) Papermaking process

[0048] Paper machine type selection: Fourdrinier machine; forming wire speed: 80-100 m / min; net vacuum: -0.3 to -0.5 bar; two press sections are used, with the first press pressure being 100-200 kN / m and the second press pressure being 200-300 kN / m; drying temperature: 100-120°C, gradual drying through multiple drying cylinders, with the final dryness reaching more than 95%;

[0049] 5) Post-processing

[0050] Use a coater to evenly apply the coating to the surface of the tracing paper; control the coating amount to be 5-10 g / m² to not affect the transparency and sensory properties of the paper.

[0051] Further, the application also provides the use of the high-transparency tracing paper in the preparation of high-end packaging paper.

[0052] The application has the following technical effects due to the adoption of the above technical solutions:

[0053] 1. Enhanced mechanical properties

[0054] Elasticity and folding resistance: the addition of polyurethane particles provides additional elasticity to the tracing paper, making it more capable of recovering when folded and bent, reducing the formation of creases and thus prolonging the service life of the paper;

[0055] Wear resistance: the addition of nano-silica enhances the wear resistance of the paper surface, making it more resistant to wear during daily use and maintaining the integrity and aesthetics of the paper surface;

[0056] 2. Improved surface properties

[0057] Transparency and gloss: polyvinyl alcohol (PVA) provides excellent film-forming properties, forming a transparent and glossy film that improves the visual effect of the tracing paper and makes the display of graphics and text clearer;

[0058] Matte effect: the specific particle size distribution of nano-silica not only enhances wear resistance but also gives the paper surface a unique matte texture, improving the feel of writing and drawing;

[0059] 3. Improved chemical and physical stability

[0060] Water resistance: The addition of natural resin (such as rosin) increases the adhesion of the coating, improves the water resistance of the paper, makes it more stable in a humid environment, and reduces the damage of moisture to the paper;

[0061] Flexibility: Glycerol as a plasticizer not only improves the flexibility of the coating, but also enhances the overall folding resistance of the paper, so that the paper can maintain good physical properties even after repeated use or folding. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0063] Embodiment 1

[0064] A high-transparency tracing paper surface coating, which is composed of the following components by mass percentage:

[0065] Polyvinyl alcohol (PVA): 15%

[0066] Nano-silicon dioxide (SiO2): 4%

[0067] Glycerol: 3%

[0068] Polyurethane particles: 2%

[0069] Rosin: 1.5%

[0070] Water: the balance to 100%.

[0071] Preparation steps:

[0072] Pre-treatment: use a ball mill to pre-disperse nano-silicon dioxide and polyurethane particles, ball mill for 1.5 hours, after ball milling, the polyurethane particles are 1-10 microns, to ensure uniform dispersion of particles;

[0073] Dissolve PVA: heat the water to 50°C, slowly add PVA powder to the preheated water, and stir at a speed of 500 rpm until completely dissolved.

[0074] Add nano-SiO2 and polyurethane particles: slowly add the pre-treated nano-SiO2 and polyurethane particles to the PVA solution, and stir at a high speed of 600 rpm for 15 minutes.

[0075] Addition of Glycerol and Rosin: Add glycerol first and continue stirring for 5 minutes, then slowly add rosin and continue stirring until completely dissolved.

[0076] Homogenization: Use a high-shear homogenizer to process the mixture at 10,000 rpm for 5 minutes.

[0077] Cooling and Adjustment: Allow the mixture to cool naturally to room temperature, and adjust the viscosity to meet the coating requirements.

[0078] The preparation method of high-transparency tracing paper is as follows:

[0079] Fibrils: 70% pure cotton pulp and 30% bamboo pulp (both need to be bleached);

[0080] Filler: Nano-silicon dioxide, accounting for 2% of the total pulp weight;

[0081] Reinforcing agent: Polyvinyl alcohol (PVA), accounting for 5% of the total pulp weight.

[0082] 1) Bleaching of cotton pulp / bamboo pulp:

[0083] Use environmentally friendly bleaching agents such as hydrogen peroxide for bleaching to ensure that the whiteness of the pulp reaches more than 90%;

[0084] 2) Refining:

[0085] Use a refiner to refine the cotton / bamboo pulp to 850SR to ensure high fiber fineness and paper transparency;

[0086] 3) Filler and reinforcing agent addition:

[0087] Disperse nano-silicon dioxide and polyvinyl alcohol evenly in the pulp, mix for 30 minutes using a high-speed stirrer to ensure complete integration;

[0088] 4) Papermaking process

[0089] Paper machine type selection: long net paper machine; forming net speed: 80-100 m / min; net vacuum degree: -0.3 to -0.5 bar; use two presses, the first press pressure is 100-200 kN / m, the second press pressure is 200-300 kN / m; drying temperature: 100-120°C, gradually dried through multiple drying cylinders, the final dryness reaches more than 95%;

[0090] 5) Post-processing

[0091] Use a coating machine to evenly coat the coating on the surface of the tracing paper; control the coating amount to be 5-10 g / m² to not affect the transparency and sensory properties of the paper.

[0092] Example 2

[0093] A coating for a high-transparency tracing paper surface coating, the coating comprising the following components by weight percentage:

[0094] Polyvinyl alcohol (PVA): 12%

[0095] Nano-silica (SiO2): 3%

[0096] Glycerin: 4%

[0097] Polyurethane particles: 1.5%

[0098] Rosin: 2.0%

[0099] Water: Bring the balance to 100%.

[0100] The preparation methods of the coating and the high-transparency tracing paper described above are as shown in Example 1.

[0101] Example 3

[0102] A coating for a high-transparency tracing paper surface coating, the coating comprising the following components by weight percentage:

[0103] Polyvinyl alcohol (PVA): 18%

[0104] Nano-silica (SiO2): 5%

[0105] Glycerin: 2.0%

[0106] Polyurethane particles: 2.5%

[0107] Rosin: 2.0%

[0108] Water: Bring the balance to 100%.

[0109] The preparation methods of the coating and the high-transparency tracing paper described above are as shown in Example 1.

[0110] Example 4

[0111] A coating for a high-transparency tracing paper surface coating, the coating comprising the following components by weight percentage:

[0112] Polyvinyl alcohol (PVA): 15%

[0113] Nano-silica (SiO2): 4%

[0114] Glycerin: 3%

[0115] Polyurethane particles: 2%

[0116] Rosin: 1.5%

[0117] Water: Bring the balance to 100%.

[0118] Market purchase of high transparency tracing paper produced by a company in Zhejiang Province, using a coating machine to evenly coat the paint on the surface of the tracing paper; control the coating amount is 5-10 g / m², to not affect the transparency and sensory properties of the paper.

[0119] Comparative Example 1

[0120] A paint consisting of the following components by mass percentage:

[0121] Polyvinyl alcohol (PVA): 15%

[0122] Nano-silicon dioxide (SiO2): 4%

[0123] Glycerol: 3%

[0124] Rosin: 1.5%

[0125] Water: the balance to 100%.

[0126] The preparation method of the above paint and the preparation method of high transparency tracing paper are shown in Example 1.

[0127] Comparative Example 2

[0128] A paint consisting of the following components by mass percentage:

[0129] Polyvinyl alcohol (PVA): 15%

[0130] Nano-silicon dioxide (SiO2): 4%

[0131] Polyurethane particles: 2%

[0132] Rosin: 1.5%

[0133] Water: the balance to 100%.

[0134] The preparation method of the above paint and the preparation method of high transparency tracing paper are shown in Example 1.

[0135] Comparative Example 3

[0136] A paint consisting of the following components by mass percentage:

[0137] Polyvinyl alcohol (PVA): 15%

[0138] Glycerol: 3%

[0139] Polyurethane particles: 2%

[0140] Rosin: 1.5%

[0141] Water: the balance to 100%.

[0142] The preparation method of the coating and the preparation method of the high-transparency tracing paper are as shown in Example 1.

[0143] Comparative Example 4

[0144] The high-transparency tracing paper produced by a company in Zhejiang Province was purchased from the market, and the same as Example 4.

[0145] Test Design

[0146] 1. Fold Whitening Test

[0147] Objective: To verify the effect of the coating on reducing fold whitening.

[0148] Method: Fold the tracing paper of the examples and comparative examples 100 times, respectively, and record the number of times of obvious fold whitening.

[0149] 2. Transparency Test

[0150] Objective: To measure the effect of the coating on the transparency of the paper.

[0151] Method: Use the transparency measuring instrument to measure the transparency of the tracing paper of the examples and comparative examples.

[0152] 3. Flexibility Test

[0153] Objective: To evaluate the improvement effect of the coating on the flexibility of the paper.

[0154] Sample Preparation: Prepare standard size samples from the coated tracing paper of the examples and comparative examples, the recommended size is 200mm x 50mm. Ensure the consistency of each sample, including the drying and curing of the coating.

[0155] Test Equipment: Use the flexibility tester, if there is no special instrument, use simple equipment such as clamps and angle measuring tools.

[0156] Clamp the sample: Fix the paper sample at one end on the clamp, ensure clamping and fixation, and the other end is freely hanging.

[0157] Load application: Attach a 50g weight to the free end of the paper to simulate the stress condition.

[0158] Measure the bending angle: After applying the load, measure the maximum bending angle of the paper. Use an angle meter or corresponding measuring tool to measure, ensure the accuracy of the measurement.

[0159] 4. Abrasion Resistance Test

[0160] Objective: To evaluate the effect of the coating on enhancing the abrasion resistance of the tracing paper.

[0161] Test sample preparation: Prepare drawing paper samples of the same size and conditions from the examples and comparative examples, ensuring consistency in the state of each sample. The recommended sample size is 100mm x 100mm.

[0162] Test instrument selection: Choose the Taber Abraser, which is a standard instrument for evaluating material wear resistance.

[0163] Test parameter setting: Select CS-10 grinding wheels and a load of 250g, which is a common test parameter setting suitable for evaluating the wear resistance of paper materials.

[0164] Sample installation: Fix the drawing paper sample on the sample tray of the Taber Abraser, ensuring that the sample is flat and secure.

[0165] Test start: Start the Taber Abraser and record the time and cycle number when the device starts to wear.

[0166] Monitoring and recording: Monitor the wear state of the sample during the test and record the cycle number required to reach the predetermined wear degree (based on the cycle number of Comparative Example 4).

[0167] The experimental data is shown in the following table:

[0168] Experimental index Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Number of crease whitening (after 100 times folding) 5 10 7 15 50 45 25 80 Transparency (%) 95 93 94 92 96 95 96 94 Flexibility (bending angle) 120° 115° 118° 105° 90° 100° 95° 84° Wear resistance (cycle number) 2557 2487 2647 2168 1854 1975 873 200

[0169] Fold whitening frequency: refers to the number of times the paper appears obvious fold whitening after 100 folding operations. The fewer the number, the better the performance.

[0170] Transparency: expressed in percentage, the higher the value, the better the transparency.

[0171] Flexibility (bending angle): the maximum bending angle of the paper under the action of a certain force. The larger the angle, the better the flexibility of the paper.

[0172] Wear resistance (cycle number): the number of wear cycles required for the paper surface to reach the same degree of wear. The more the number, the better the wear resistance.

[0173] The above is a description of the embodiments of the present application. Through the above description of the disclosed embodiments, those skilled in the art can implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-transparency tracing paper, characterized in that, The base paper for high-transparency tracing paper is made from pulp consisting of 60-80% bleached pure cotton pulp and 20-40% bleached bamboo pulp by weight, with the addition of 2-4% nano-silica and 5-10% polyvinyl alcohol by weight. The surface of the high-transparency tracing paper is coated with a paint; this paint consists of the following components by weight percentage: Polyvinyl alcohol: 10-20% Nano-silica: 2.0-8.0% Glycerin: 1.0-5.0% Polyurethane particles: 1.0-3.0% Natural resin: 0.5-3.0% Water level should be increased to 100%. The natural resin is one or more of rosin, pine resin, and gelatin.

2. The high-transparency tracing paper according to claim 1, characterized in that, The coating consists of the following components by weight percentage: Polyvinyl alcohol: 12-18% Nano-silica: 3.0-5.0% Glycerin: 2.0-4.0% Polyurethane particles: 1.5-2.5% Natural resin: 1.0-2.0% Water level should be 100%.

3. The high-transparency tracing paper according to claim 1, characterized in that, The particle size of polyurethane particles ranges from 1 micrometer to 10 micrometers.

4. The high-transparency tracing paper according to claim 1, characterized in that, The preparation method of the coating includes the following steps: 1) Preprocessing The nano-silica and polyurethane particles were pre-dispersed using a ball mill for 1-2 hours to ensure uniform particle size and dispersion. 2) Dissolving PVA Heat the water to 50°C, then slowly add the PVA powder to the preheated water while stirring at 300-500 rpm with a high-speed stirrer until completely dissolved. 3) Add nano-SiO2 and polyurethane particles Method: The pretreated nano-SiO2 and polyurethane particles were slowly added to the PVA solution, and the mixture was stirred at high speed of 500-800 rpm for 10-20 minutes to ensure thorough mixing. 4) Introducing glycerin and natural resins First add glycerin and continue stirring for 5 minutes. Then slowly add rosin and stir until completely dissolved, keeping the temperature at 50°C to promote dissolution. 6) Homogenization treatment The mixture was treated using a high-shear homogenizer at a speed of 8000-10000 rpm for 5-10 minutes. 7) Cooling and Adjustment Allow the mixture to cool naturally to room temperature, and adjust the final viscosity to suit different coating methods.

5. A method for preparing a high-transparency tracing paper according to any one of claims 1-4, characterized in that, The method includes the following steps: 1) Bleached cotton pulp / bamboo pulp: Use environmentally friendly bleaching agents for bleaching treatment to ensure that the whiteness of the pulp reaches more than 90%. 2) Grinding: Use a refiner to refine the cotton / bamboo pulp to 85°SR to ensure high fiber fineness and paper transparency; 3) Addition of fillers and reinforcing agents: Disperse nano-silica and polyvinyl alcohol evenly in the slurry and mix for 30 minutes using a high-speed mixer to ensure full integration; 4) Papermaking process Paper machine selection: long-wire paper machine; forming wire speed: 80-100 m / min; wire vacuum: -0.3 to -0.5 bar; two-stage pressing, first pressing pressure 100-200 kN / m, second pressing pressure 200-300 kN / m; drying temperature: 100-120°C, gradual drying through multiple drying cylinders, final dryness reaching over 95%; 5) Post-processing The coating is evenly applied to the surface of the tracing paper using a coating machine; the coating amount is controlled to be 5-10 g / m² so as not to affect the transparency and sensory properties of the paper.

6. The application of the high-transparency tracing paper according to any one of claims 1-4 in the preparation of high-end packaging paper.