Transparent wrapping paper and process for its production

Abstract

The present application relates to the technical field of transparent wrapping paper production, in particular to transparent wrapping paper and its production process. 100% bleached kraft pulp is selected, and after the pulping is completed, the pulping process is entered. After the pulping is completed, the chemical process is carried out, and the transparent agent, defoaming agent, bactericide and aluminum sulfate are added in the pulp. At the same time, the surface sizing agent is prepared, and the stearic acid, paraffin, borax and stearic acid emulsifier are prepared, and the above raw materials are added into the surface glue cooking tank according to the mass ratio for standby. After the chemical process related operation is completed, the paper machine process is entered, and the 1880mm long net multi-cylinder paper machine is used for production, and finally the transparent wrapping paper is output. The present application greatly improves the transparency of the paper sheet by selecting special kind of pulp board, special pulping process, using transparent agent in the pulp and using special process in the surface glue.

Description

Technical Field

[0001] This invention relates to the field of transparent packaging paper production technology, specifically transparent packaging paper and its production process. Background Technology

[0002] Paper packaging is considered an important solution due to its renewability and recyclability; however, ordinary paper cannot meet the requirements of high-end gift packaging in terms of transparency, moisture resistance, and mechanical strength. For example, traditional transparent paper often relies on lamination or plastic coating processes, which improve performance but increase recycling difficulty, thus contradicting the concept of a circular economy.

[0003] In recent years, the industry's technological exploration in the field of high-transparency paper has mainly focused on the following directions: Fiber refinement technology: reducing fiber diameter through physical or chemical methods to improve paper transparency. For example, Huitong Paper uses high-temperature and high-pressure treatment to break cellulose hydrogen bonds, refining fibers to the micron level, but this approach suffers from high energy consumption and complex processes. Environmentally friendly coating technology: Minfeng Special Paper improves moisture resistance through a double-layer biodegradable waterproof coating (modified starch, chitosan, etc.), but the coating uniformity and transparency stability are still insufficient. Intelligent structural design: For example, Guosheng Packaging in Biyang County uses a movable mesh plate to adjust the air permeability of its breathable cartons, but its base material still relies on traditional pulp, making it difficult to balance high transparency and high strength.

[0004] While the aforementioned technologies have each made breakthroughs, they generally suffer from the following problems: insufficient environmental friendliness of the process; lack of performance balance: transparency, mechanical strength, and moisture resistance are difficult to improve in a coordinated manner; and contradiction between cost and scalability: for example, the high cost of nanocellulose reinforcement technology limits its industrial application. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a production process for transparent packaging paper. By selecting special types of pulp boards, special pulping processes, using transparent agents in the pulp, and using special processes for surface sizing, the transparency of the paper is greatly improved.

[0006] Another objective of this invention is to provide a transparent packaging paper that has high transparency, excellent performance, and can be industrially produced.

[0007] This invention is achieved using the following technical solution: The production process of the transparent packaging paper includes the following steps: (1) 100% bleached sulfate softwood pulp was selected for pulping. After pulping, the pulping process was carried out. Six DD720 disc mills were connected in series for pulping. Cutting-type mill discs were configured for #1-3 and disintegrating-type mill discs were configured for #4-6. After setting the parameters, pulping was carried out to obtain the pulp. (2) After pulping is completed, chemicals are added. First, a transparent agent, defoamer, bactericide and aluminum sulfate are added to the pulp. At the same time, the surface sizing agent is prepared. Stearic acid, paraffin, borax and stearic acid emulsifier are prepared. The above raw materials are added to the surface sizing digester according to the mass ratio for later use. (3) The papermaking equipment is an 1880mm long wire multi-cylinder paper machine. Production is carried out according to the setting of basis weight, machine speed, lip opening, shaking, pulp wire speed ratio, dryness control at each stage, drying cylinder temperature, sizing machine and calender parameters, and finally transparent packaging paper is produced.

[0008] The bleached sulfate softwood pulp has a pentosaccharide content of 7-8% and an α-cellulose content of >86%.

[0009] In the pulping process, the power of the disc mill is 500kW+500kW+500kW+400kW+400kW+400kW, the pulping concentration is 3.0-3.5%, and the flow rate is 180-190 m³ / h. 3 / h, valve opening is 45-50%.

[0010] The pulp has a freeness of 90-93°SR, a wet weight of 1.0-1.5g, a temperature of 73-75℃, and a pH of 5.5-6.0.

[0011] The amount of the transparent agent added is 5-8 kg / ton of paper, with a solid content ≥40%, a pH of 2-4, and a viscosity of 50-100 mPa·s; the amount of the defoamer added is 150-200 g / ton of paper, the defoamer is polyether-based, and the solid content is ≥8%; the amount of the bactericide added is 100-200 g / ton of paper, it is an organic bromine bactericide, and the solid content is ≥20%; the amount of aluminum sulfate added is 15-20 kg / ton of paper, and the Al2O3 content is ≥15.6%.

[0012] The amount of stearic acid added is 10-15 kg / ton of paper, with a purity ≥99%; the amount of paraffin added is 3-5 kg / ton of paper, with a purity ≥99%; the amount of borax added is 1-3 kg / ton of paper, with a purity ≥99.5%; and the amount of stearic acid emulsifier added is 3-3.5 kg / ton of paper, with a solid content ≥20%.

[0013] The preparation process of the surface sizing agent is as follows: Add 50-55 kg of stearic acid, 16-18 kg of paraffin wax, 3-3.5 kg of borax, 3-3.5 kg of stearic acid emulsifier, and 500-550 kg of water to a surface sizing tank. Start the stirrer, open the steam valve, heat to 95-98℃, control the time at 25-30 min, and keep warm for 15-20 min. Then transfer the solution to a dilution tank, add water at 80-90℃, and dilute to a concentration of 4.8-5.2% to obtain a surface sizing agent with a concentration of 4.8-5.2%, a viscosity of 15-25 mPa·s, and a pH of 7-7.5.

[0014] The basis weight of the aforementioned long-wire multi-cylinder paper machine is 50±1g / m; machine speed: 150-180m / min; lip opening: 10-12mm; vibration: amplitude 10-20mm, vibration frequency 180-230 times / min; pulp-wire speed ratio 0.95-0.97; dryness of the exit roll 15-17%, dryness of the first press 34-36%, dryness of the second press 38-40%, and dryness of the third press 41-43%.

[0015] The drying cylinder temperatures of the aforementioned long-wire multi-cylinder paper machine are as follows: Pre-drying: 46±1℃, 48±1℃, 50±1℃, 55±1℃, 58±1℃, 60±1℃, 65±1℃, 70±1℃, 75±1℃, 80±1℃, 80±1℃, 85±1℃, 88±1℃, 90±1℃; Post-drying: 70±1℃, 75±1℃, 78±1℃, 82±1℃, 85±1℃, 88±1℃, 90±1℃, 95±1℃; The sizing machine adopts an immersion sizing machine, with an infeed dryness of 93-95% and an outfeed dryness of 63-65%, and a sizing machine linear pressure of 80-100kN / m; The calender hard roll temperature is 120-150℃; the pressure is 100-120kN / m; and the finished paper dryness is 94-96%.

[0016] The transparent packaging paper is produced using the transparent packaging paper manufacturing process described above.

[0017] Raw material selection and process optimization: 100% bleached sulfate softwood pulp (Swedish Blue Forest brand) is used, with an α-cellulose content of >86% and a pentosan content of 7-8%, which makes it easier to break down into fibers during pulping and reduces the amount of chemical additives used; Physicochemical synergistic modification: Through series disc milling and pulping (combination of cutting and disintegration) and surface sizing process (stearic acid-paraffin composite coating), the best balance between fiber fineness and hydrogen bond recombination is achieved, avoiding the recycling problems of traditional coating process; Balance between energy consumption and performance: The 1880mm long wire multi-cylinder paper machine, combined with gradient drying temperature (pre-drying 46-90℃, post-drying 70-95℃), reduces steam energy consumption while ensuring transparency.

[0018] Compared with the prior art, the beneficial effects of the present invention are: (1) Swedish Blue Forest brand bleached sulfate softwood pulp is selected. The content of pentosaccharides and α-cellulose is appropriate. It is easy to defilament and cut during pulping, which lays the foundation for high transparency. The unique pulping process, with 6 DD720 disc mills connected in series and specific grinding discs and parameters, optimizes the fiber structure. A transparent agent is added to the pulp to improve the bonding between fibers and increase the light transmittance. These measures work together to make the paper transparent ≥75%, which is much higher than ordinary packaging paper. It can clearly display the contents of the packaging and enhance the product's attractiveness.

[0019] (2) Softwood pulp fiber itself has high strength. Combined with reasonable pulping process, control indicators such as beating degree and wet weight, ensure effective bonding between fibers, enhance the connection between fibers, improve the overall strength of paper, and the tear strength of the product is ≥300Nm and the breaking length is ≥7.5km. It can withstand greater external force during packaging, is not easy to break, and effectively protects the product.

[0020] (3) Precisely control the paper machine process parameters, such as machine speed, lip opening, and vibration, to ensure that the paper basis weight is uniform and the thickness is consistent. Reasonable setting of the temperature and pressure of the hard roll of the calender makes the paper smoothness average ≥120s on both sides, with a smooth touch, good printability, and improved packaging aesthetics.

[0021] (4) Reasonable selection of pulp board and pulping and sizing process make the paper structure compact and the fiber arrangement orderly. The low shrinkage rate ≤0.8% ensures dimensional stability under different environmental humidity and is not easily deformed; the water absorption value ≤20g / m² can effectively prevent moisture and extend the shelf life of packaged products.

[0022] (5) The transparent packaging paper produced can replace traditional plastic packaging products, which meets the requirements of the national circular economy development. Paper products are recyclable, reducing plastic pollution and are of great significance to environmental protection. Detailed Implementation

[0023] To make the objectives and technical solutions of this invention clearer, this invention will be further described in detail.

[0024] The following are the sources of the raw materials used in the examples and comparative examples: Bleached sulfate softwood pulp: Swedish Blue Forest brand bleached sulfate softwood pulp; Transparent agent: Guangzhou Chenghe Technology Co., Ltd.; Defoamer: Zhejiang Chuanhua Huayang Chemical Co., Ltd.; Fungicide: Zhejiang Chuanhua Huayang Chemical Co., Ltd.; Aluminum sulfate: Zibo Dazhong Chemical Co., Ltd.; Stearic acid: Shijiazhuang Lumen Chemical Technology Co., Ltd.; Paraffin wax: Shanghai Dongming Chemical Co., Ltd.; Stearic acid emulsifier: Qingdao Shengying Innovation Materials Co., Ltd.; Borax: Tianjin Jinhui Taiya Chemical Reagent Co., Ltd.

[0025] Example 1 The production process of transparent packaging paper includes the following steps: (1) 100% bleached sulfate softwood pulp is selected for pulping. After pulping, it enters the pulping process. Six DD720 disc mills are connected in series for pulping. No. 1-3 are equipped with cutting type mill discs, and No. 4-6 are equipped with disintegrating type mill discs. After setting the parameters, pulping is carried out, and then the pulp is obtained. (2) After pulping, chemical processing is carried out. First, a transparent agent, defoamer, bactericide and aluminum sulfate are added to the pulp. At the same time, the surface sizing agent is prepared. Stearic acid, paraffin, borax and stearic acid emulsifier are prepared. The above raw materials are added to the surface sizing digester according to the mass ratio for later use. (3) After completing the chemical process-related operations, the paper machine process is entered. Using an 1880mm long wire multi-cylinder paper machine, production is carried out according to the basis weight, machine speed, lip opening, shaking, pulp wire speed ratio, dryness control at each stage, drying cylinder temperature, sizing machine and calender parameters, and finally transparent packaging paper is produced.

[0026] Pulp board composition: 100% Swedish Blue Forest brand bleached sulfate softwood pulp, with a pentosaccharide content of 7% and an α-cellulose content of 87%.

[0027] Pulping process: Six DD720 disc mills are connected in series for pulping, with cutting-type mill discs #1-3 and dispersing-type mill discs #4-6. The pulping power is 500kW+500kW+500kW+400kW+400kW+400kW, the pulping concentration is 3.0%, and the flow rate is 180m³. 3 / h, valve opening 45%, pulp quality: freeness 90°SR, wet weight 1.5g, temperature 73℃, pH value 5.5; Chemical processes: 1) In the pulp: Transparent agent: 5 kg / ton of paper, solid content 40%, pH 3, viscosity 80 mPa·s; Defoamer: 150g / ton of paper, polyether, solid content 28%; Bactericide: 100g / ton of paper, organic bromine bactericide, solid content 30%; Aluminum sulfate: 15 kg / ton of paper, Al2O3 content 16%; 2) Surface sizing agent: stearic acid: 10kg / ton of paper, purity 99%; Paraffin wax: 3 kg / ton of paper, purity 99%; Stearic acid emulsifier: 3 kg / ton of paper, solid content 20%; Borax: 1 kg / ton of paper, purity 99.5%; 3) Surface sizing agent preparation process: (1) Raw materials: stearic acid, paraffin wax, borax, stearic acid emulsifier; (2) Preparation process: Add 50 kg of stearic acid, 16 kg of paraffin wax, 3 kg of borax, 3 kg of stearic acid emulsifier, and 500 kg of water to a surface adhesive cooking tank. Start the stirrer, open the steam valve, and slowly heat to 95°C for 25 minutes, then keep warm for 15 minutes. Then transfer the solution to a dilution tank, add 80°C hot water, and dilute to a concentration of 4.8% for later use. Surface sizing agent solution mass: concentration 4.8%, viscosity 15 mPa·s, pH 7, temperature 80℃; Paper machine process: Production using an 1880mm long-wire multi-cylinder paper machine; a. Quantitative value: 49 g / m³; b. Vehicle speed: 150m / min; c. Lip opening: 10mm; d. Shaking: Amplitude 10mm, frequency 180 times / min; e. Pulp-to-mesh speed ratio 0.95; f. Dryness of the first press roll is 15%, dryness of the second press roll is 34%, dryness of the third press roll is 38%, and dryness of the fourth press roll is 41%. g. Drying cylinder temperature: Pre-baking: 45℃, 47℃, 49℃, 54℃, 57℃, 59℃, 64℃, 69℃, 74℃, 79℃, 79℃, 84℃, 87℃, 89℃; Post-drying: 69℃, 74℃, 77℃, 81℃, 84℃, 87℃, 89℃, 94℃; h. Glue applicator: Immersion glue applicator, glue inlet dryness: 93%, glue outlet dryness: 63%, glue applicator linear pressure: 80kN / m; i. The temperature of the hard roll of the calender is 120℃ and the pressure is 100kN / m; j. Paper dryness: 94%.

[0028] Example 2 The production process of transparent packaging paper includes the following steps: (1) 100% bleached sulfate softwood pulp is selected for pulping. After pulping, it enters the pulping process. Six DD720 disc mills are connected in series for pulping. No. 1-3 are equipped with cutting type mill discs, and No. 4-6 are equipped with disintegrating type mill discs. After setting the parameters, pulping is carried out, and then the pulp is obtained. (2) After pulping, chemical processing is carried out. First, a transparent agent, defoamer, bactericide and aluminum sulfate are added to the pulp. At the same time, the surface sizing agent is prepared. Stearic acid, paraffin, borax and stearic acid emulsifier are prepared. The above raw materials are added to the surface sizing digester according to the mass ratio for later use. (3) After completing the chemical process-related operations, the paper machine process is entered. Using an 1880mm long wire multi-cylinder paper machine, production is carried out according to the basis weight, machine speed, lip opening, shaking, pulp wire speed ratio, dryness control at each stage, drying cylinder temperature, sizing machine and calender parameters, and finally transparent packaging paper is produced.

[0029] Pulping process: Pulp board ratio: 100% bleached sulfate softwood pulp, 7% pentosaccharide content, 87% α-cellulose content, easy to defilament and cut during pulping, resulting in high paper transparency.

[0030] Pulping process: 6 DD720 disc mills in series for pulping, with cutting-type mill discs 1-3 and dispersing-type mill discs 4-6. Pulping power: 500kw+500kw+500kw+400kw+400kw+400kw. Pulping concentration: 3.5%. Flow rate: 190m3 / h. Valve opening: 50%. Pulp quality: freeness 93°SR, wet weight 1.0g, temperature 75℃, pH value 6.0.

[0031] Chemical processes: 1) In the pulp: Transparent agent: 8 kg / ton of paper, solid content 40%, pH 3, viscosity 80 mPa·s; Defoamer: 200g / ton of paper, polyether, solid content 28%; Bactericide: 200g / ton of paper, organic bromine bactericide, solid content 30%; Aluminum sulfate: 20 kg / ton of paper, Al2O3 content 16%; 2) Surface sizing agent: stearic acid: 15 kg / ton of paper, purity 99%; Paraffin wax: 5 kg / ton of paper, purity 99%; Stearic acid emulsifier: 3.5 kg / ton of paper, purity 99.5%; Borax: 3 kg / ton of paper; 3) Surface sizing agent preparation process: (1) Raw materials: stearic acid, paraffin wax, borax, stearic acid emulsifier; (2) Preparation process: Add 55 kg of stearic acid, 18 kg of paraffin wax, 3.5 kg of borax, 3.5 kg of stearic acid emulsifier, and 550 kg of water to a surface adhesive cooking tank. Start the stirrer, open the steam valve, and slowly heat to 98°C for 30 minutes, then maintain the temperature for 20 minutes. Then transfer the solution to a dilution tank, add 90°C hot water, and dilute to a concentration of 5.2% for later use. Surface sizing agent solution mass: concentration 5.2%; viscosity 25 mPa·s; pH 7.5; temperature 90℃; Paper machine process: Production using an 1880mm long-wire multi-cylinder paper machine; a. Quantitative value 51g / m b. Vehicle speed: 180m / min c. Lip opening: 12mm d. Shaking: Amplitude 20mm, frequency 230 times / min e. Pulp-to-mesh speed ratio 0.97; f. Dryness of the roll exiting the first press is 17%, the dryness of the first press is 36%, the dryness of the second press is 40%, and the dryness of the third press is 43%. g. Drying cylinder temperature: Pre-baking: 47℃, 49℃, 51℃, 56℃, 59℃, 61℃, 66℃, 71℃, 76℃, 81℃, 81℃, 86℃, 89℃, 91℃; Post-drying: 71℃, 76℃, 79℃, 83℃, 86℃, 89℃, 91℃, 96℃; h. Glue applicator: Immersion glue applicator, glue inlet dryness: 95%, glue outlet dryness: 65%, glue applicator linear pressure: 100kN / m; i. The temperature of the hard roll of the calender is 150℃ and the pressure is 120kN / m; j. Paper dryness: 96%.

[0032] Example 3 The production process of transparent packaging paper includes the following steps: (1) 100% bleached sulfate softwood pulp is selected for pulping. After pulping, it enters the pulping process. Six DD720 disc mills are connected in series for pulping. No. 1-3 are equipped with cutting type mill discs, and No. 4-6 are equipped with disintegrating type mill discs. After setting the parameters, pulping is carried out, and then the pulp is obtained. (2) After pulping, chemical processing is carried out. First, a transparent agent, defoamer, bactericide and aluminum sulfate are added to the pulp. At the same time, the surface sizing agent is prepared. Stearic acid, paraffin, borax and stearic acid emulsifier are prepared. The above raw materials are added to the surface sizing digester according to the mass ratio for later use. (3) After completing the chemical process-related operations, the paper machine process is entered. Using an 1880mm long wire multi-cylinder paper machine, production is carried out according to the basis weight, machine speed, lip opening, shaking, pulp wire speed ratio, dryness control at each stage, drying cylinder temperature, sizing machine and calender parameters, and finally transparent packaging paper is produced.

[0033] 1. Pulping process: Pulp board ratio: 100% bleached sulfate softwood pulp, 7% pentosaccharide content, 87% α-cellulose content, easy to defilament and cut during pulping, resulting in high paper transparency.

[0034] 3. Pulping process: Six DD720 disc mills were connected in series for pulping, with cutting-type mill discs #1-3 and dispersing-type mill discs #4-6. The pulping power was 500kW+500kW+500kW+400kW+400kW+400kW, the pulping concentration was 3.3%, the flow rate was 185m³ / h, the valve opening was 48%, and the pulp quality was: freeness 92°SR, wet weight 1.2g, temperature 74℃, and pH value 5.8.

[0035] 3. Chemical Processes: 1) In the pulp: Transparent agent: 7kg / ton of paper, solid content 40%, pH 3, viscosity 80mPa·s; Defoamer: 180g / ton of paper, polyether, solid content 28%; Bactericide: 150g / ton of paper, organic bromine bactericide, solid content 30%; Aluminum sulfate: 18 kg / ton of paper, Al2O3 content 16%; 2) Surface sizing agent: stearic acid: 13 kg / ton of paper, purity 99%; Paraffin wax: 4 kg / ton of paper, purity 99%; Stearic acid emulsifier: 3.3 kg / ton of paper, with a solid content of 20%; Borax: 2 kg / ton of paper, purity 99.5%; 3) Surface sizing agent preparation process: (1) Raw materials: stearic acid, paraffin wax, borax, stearic acid emulsifier; (2) Preparation process: Add 53 kg of stearic acid, 17 kg of paraffin wax, 3.2 kg of borax, 3.2 kg of stearic acid emulsifier, and 525 kg of water to a surface adhesive cooking tank. Start the stirrer, open the steam valve, and slowly heat to 97°C for 28 minutes, then maintain the temperature for 18 minutes. Then transfer the solution to a dilution tank, add 85°C hot water, and dilute to a concentration of 5.0% for later use. Quality standards for surface sizing agent solution: concentration 5%, viscosity 20 mPa·s, pH 7.3, temperature 85℃; 4. Paper machine process: Production using a 1880mm long-wire multi-cylinder paper machine; a. Quantitative dose: 50 g / m³; b. Vehicle speed: 165m / min; c. Lip opening: 11mm; d. Shaking: Amplitude 15mm, frequency 200 times / min; e. Pulp-to-mesh speed ratio 0.96; f. Dryness of the first press roll is 16%, dryness of the second press roll is 35%, dryness of the third press roll is 39%, and dryness of the fourth press roll is 42%. g. Drying cylinder temperature: Pre-baking: 46℃, 48℃, 50℃, 55℃, 58℃, 60℃, 65℃, 70℃, 75℃, 80℃, 80℃, 85℃, 88℃, 90℃; Post-baking: 70℃, 75℃, 78℃, 82℃, 85℃, 88℃, 90℃, 95℃; h. Glue applicator: Immersion glue applicator, glue inlet dryness: 94%, glue outlet dryness: 64%, glue applicator linear pressure: 90kN / m; i. The temperature of the hard roll of the calender is 135℃ and the pressure is 110kN / m; j. Paper dryness: 95%.

[0036] Comparative Example 1: Other process conditions were the same as in Example 3, except that the Swedish Blue Forest brand bleached sulfate softwood pulp was replaced with conventional softwood pulp Brazilian eucalyptus pulp board.

[0037] Comparative Example 2: Other process conditions were the same as in Example 3, except that the pulp quality was changed from a freeness of 90-93°SR to 60-63°SR.

[0038] Comparative Example 3: Other process conditions were the same as in Example 3, except that the amount of transparent agent in the slurry was changed from 5-8 kg to 3 kg.

[0039] Comparative Example 4: Other process conditions were the same as in Example 3, and general oxidized starch was used for surface sizing.

[0040] The test data for Examples 1-3 and Comparative Examples 1-4 are shown in Table 1.

[0041] Table 1 Test data for Examples 1-3 and Comparative Examples 1-4

[0042] The data obtained above show that this invention exhibits high stability in terms of basis weight, stretch rate, and moisture content. Test data shows that the basis weight of all examples and comparative examples is within the range of 50±2 g / m², the stretch rate is ≤0.8%, and the moisture content is between 4-6%. This is because the precise control of basis weight by the paper machine process during production, and the stable shaping of the paper structure by the overall process system, ensure that the product's fundamental properties are not significantly affected by changes in raw materials and processes. Stable fundamental properties are key to ensuring the reliability of packaging paper in subsequent processing and use, ensuring consistent product quality. The transparency of Examples 1-3 in this invention reaches 78.2%, 78.6%, and 79.1% respectively, all ≥75%, significantly better than the comparative examples. The principle behind this is that the selected Swedish Blue Forest brand bleached sulfate softwood pulp has a pentosaccharide content of 7-8% and an α-cellulose content >86%. This type of pulp board is easily defilamentized and cut during pulping, forming a uniform and dense fiber network structure, providing excellent conditions for light transmission. Adding 5-8 kg of a clarifying agent to the pulp fills the gaps between fibers, reduces light scattering, and further improves transparency. Comparative Example 1 used Brazilian eucalyptus pulp board instead, resulting in a transparency of 72.6%; Comparative Example 3 reduced the amount of clarifying agent to 3 kg, achieving a transparency of 73.5%. This fully demonstrates the crucial role of raw materials and additives in improving transparency in this invention. High transparency allows the contents of the packaging to be clearly displayed, enhancing product appeal. The breaking lengths of the examples are excellent, with Examples 1-3 showing 8.2 km, 8.4 km, and 7.9 km respectively, all ≥7.5 km. In Comparative Example 2, after the pulp quality freeness was reduced from 90-93°SR to 60-63°SR, the breaking length decreased significantly to 6.2 km. This is because a reasonable pulping process, using six DD720 disc mills connected in series, combined with cutting discs #1-3 and dispersing discs #4-6, precisely controls parameters such as refining power and concentration, allowing the fibers to be fully split and appropriately cut, forming a good interwoven structure, thereby improving the longitudinal strength of the paper. The high tear strength (≥300 Nm in Examples 1-3 and most comparative examples) is also due to this fiber structure and the enhanced inter-fiber bonding of components such as stearic acid and paraffin in the surface sizing agent, ensuring that the paper can withstand greater external forces during packaging and is not easily damaged. The average smoothness of Examples 1-3 on both sides was 135s, 145s, and 142s, respectively, all ≥120s, significantly better than Comparative Example 2 (110s) and Comparative Example 4 (102s). During the pulping process, appropriate grinding disc combinations and process parameters refine and evenly distribute the fibers, laying the foundation for the smoothness of the paper surface. The special formulation and preparation process of the surface sizing agent form a uniform film on the paper surface, further improving smoothness. Good smoothness not only makes the paper feel comfortable to the touch, but more importantly, it is beneficial for printing, making the printed patterns clearer and more exquisite, and improving the overall aesthetics of the packaging.The water absorption values ​​of Examples 1-3 were 17.6 g / m², 18.3 g / m², and 16.6 g / m², respectively, all ≤20 g / m². The aluminum sulfate and other chemicals added to the pulp react with the fibers, forming a protective film on the fiber surface, reducing the paper's water absorption. The stearic acid and paraffin wax components in the surface sizing agent also act as a waterproof barrier. In Comparative Example 3, after reducing the amount of clarifying agent in the pulp, the water absorption value increased to 19.2 g / m², close to the upper limit, indicating that the rational use of chemicals in this invention is crucial for controlling water absorption; low water absorption can effectively prevent moisture and extend the shelf life of packaged products.

Claims

1. A production process for transparent packaging paper, characterized in that, Includes the following steps: (1) 100% bleached sulfate softwood pulp was selected for pulping. After pulping, the pulping process was carried out. Six DD720 disc mills were connected in series for pulping. Cutting-type mill discs were configured for #1-3 and disintegrating-type mill discs were configured for #4-6. After setting the parameters, pulping was carried out to obtain the pulp. (2) After pulping is completed, chemicals are added. First, a transparent agent, defoamer, bactericide and aluminum sulfate are added to the pulp. At the same time, the surface sizing agent is prepared. Stearic acid, paraffin, borax and stearic acid emulsifier are prepared. The above raw materials are added to the surface sizing digester according to the mass ratio for later use. (3) The papermaking equipment is an 1880mm long wire multi-cylinder paper machine. Production is carried out according to the setting of basis weight, machine speed, lip opening, shaking, pulp wire speed ratio, dryness control at each stage, drying cylinder temperature, sizing machine and calender parameters, and finally transparent packaging paper is produced. In the pulping process, the power of the disc mill is 500kW+500kW+500kW+400kW+400kW+400kW, the pulping concentration is 3.0-3.5%, and the flow rate is 180-190 m³ / h. 3 / h, valve opening degree is 45-50%; The pulp has a beating degree of 90-93°SR, a wet weight of 1.0-1.5g, a temperature of 73-75℃, and a pH value of 5.5-6.

0. The transparent agent is added at a rate of 5-8 kg / ton of paper, with a solid content ≥40%, a pH of 2-4, and a viscosity of 50-100 mPa·s; the defoamer is added at a rate of 150-200 g / ton of paper, and the defoamer is a polyether-based agent with a solid content ≥8%; the bactericide is added at a rate of 100-200 g / ton of paper, and is an organic bromine-based bactericide with a solid content ≥20%; the aluminum sulfate is added at a rate of 15-20 kg / ton of paper, with an Al2O3 content ≥15.6%. The amount of stearic acid added is 10-15 kg / ton of paper, with a purity ≥99%; the amount of paraffin added is 3-5 kg / ton of paper, with a purity ≥99%; the amount of borax added is 1-3 kg / ton of paper, with a purity ≥99.5%; and the amount of stearic acid emulsifier added is 3-3.5 kg / ton of paper, with a solid content ≥20%. The preparation process of the surface sizing agent is as follows: Add 50-55 kg of stearic acid, 16-18 kg of paraffin wax, 3-3.5 kg of borax, 3-3.5 kg of stearic acid emulsifier, and 500-550 kg of water to a surface sizing tank. Start the stirrer, open the steam valve, heat to 95-98℃, control the time at 25-30 min, and keep warm for 15-20 min. Then transfer the solution to a dilution tank, add water at 80-90℃, and dilute to a concentration of 4.8-5.2%, obtaining a surface sizing agent with a concentration of 4.8-5.2%, a viscosity of 15-25 mPa·s, and a pH of 7-7.

5. The drying cylinder temperatures of the aforementioned long-wire multi-cylinder paper machine are as follows: Pre-drying: 46±1℃, 48±1℃, 50±1℃, 55±1℃, 58±1℃, 60±1℃, 65±1℃, 70±1℃, 75±1℃, 80±1℃, 80±1℃, 85±1℃, 88±1℃, 90±1℃; Post-drying: 70±1℃, 75±1℃, 78±1℃, 82±1℃, 85±1℃, 88±1℃, 90±1℃, 95±1℃; The sizing machine adopts an immersion sizing machine, with an infeed dryness of 93-95% and an outfeed dryness of 63-65%, and a sizing machine linear pressure of 80-100kN / m; The calender hard roll temperature is 120-150℃; the pressure is 100-120kN / m; and the finished paper dryness is 94-96%.

2. The production process of transparent packaging paper according to claim 1, characterized in that, The bleached sulfate softwood pulp has a pentosaccharide content of 7-8% and an α-cellulose content of >86%.

3. The production process of transparent packaging paper according to claim 1, characterized in that, The basis weight of the aforementioned long-wire multi-cylinder paper machine is 50±1g / m; machine speed: 150-180m / min; lip opening: 10-12mm; vibration: amplitude 10-20mm, vibration frequency 180-230 times / min; pulp-wire speed ratio 0.95-0.97; dryness of the exit roll 15-17%, dryness of the first press 34-36%, dryness of the second press 38-40%, and dryness of the third press 41-43%.

4. A transparent packaging paper, characterized in that, It is produced by the manufacturing process of the transparent packaging paper according to any one of claims 1-3.

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