Transparent packaging paper and production process thereof

Abstract

The invention relates to the technical field of transparent packaging paper production, in particular to transparent packaging paper and a production process thereof. Selecting 100% bleached sulfate softwood pulp for repulping, and entering a pulping process after the repulping is completed; after pulping is finished, a chemical process is carried out, and a transparent agent, a defoaming agent, a sterilizing agent and aluminum sulfate are added into pulp; meanwhile, a surface sizing agent is prepared, stearic acid, paraffin, borax and a stearic acid emulsifier are prepared, and the raw materials are added into a surface sizing agent cooking pot according to the mass ratio to be treated for standby application; and after related operations of a chemical process are completed, entering a paper machine process, and producing by using a 1880mm long-wire multi-cylinder paper machine, so as to finally produce the transparent packaging paper. According to the invention, special pulp boards are selected, a special pulping process is adopted, a transparent agent is used in pulp, and a special process is adopted for surface glue, so that the transparency of paper sheets is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of transparent packaging paper production, in particular to transparent packaging paper and a production process thereof. Background Art

[0002] Paper packaging is considered an important solution due to its reproducibility and recyclability, but ordinary paper is difficult to meet the requirements of high-end gift packaging in terms of transparency, moisture resistance, mechanical strength, etc. For example, traditional transparent paper mostly relies on lamination or plastic coating processes, which can improve performance but make recycling more difficult, which runs counter to the concept of 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: reduce the fiber diameter through physical or chemical methods to improve the transparency of the finished paper. For example, Huitong Co., Ltd. uses high temperature and high pressure treatment to break the cellulose hydrogen bonds and refine the fibers to the micron level, but there are problems such as high energy consumption and complex process. Environmentally friendly coating technology: Minfeng Special Paper improves moisture resistance through a double-layer degradable waterproof coating (modified starch, chitosan, etc.), but the coating uniformity and transparency stability are still insufficient. Intelligent structural design: For example, the breathable carton of Guosheng Packaging in Biyang County adjusts the air permeability efficiency through a movable mesh plate, but its base material still relies on traditional pulp, making it difficult to take into account both high permeability and high strength.

[0004] Although the above technologies have their own breakthroughs, they generally have the following problems: the process is not environmentally friendly enough; the performance is not balanced: it is difficult to improve transparency, mechanical strength and moisture resistance in a coordinated manner; there is a contradiction between cost and scale: for example, the high cost of nanocellulose reinforcement technology limits its industrial application. Summary of the invention

[0005] In view of the above deficiencies in the prior art, the purpose of the present invention is to provide a production process for transparent packaging paper, which greatly improves the transparency of paper sheets by selecting special types of pulp boards, special pulping processes, using transparent agents in the pulp, and using special processes for surface glue.

[0006] Another object of the present invention is to provide a transparent packaging paper with high transparency, excellent performance and industrial production capability.

[0007] The present invention is achieved by adopting the following technical solutions: The production process of the transparent packaging paper comprises the following steps: (1) 100% bleached kraft softwood pulp was selected for pulping. After pulping, the pulping process was started. Six DD720 disc refiners were used for pulping in series. No. 1 to No. 3 were equipped with cutting-off type refiners, and No. 4 to No. 6 were equipped with decomposing type refiners. After setting the parameters, the pulping process was carried out to obtain the finished pulp. (2) After pulping is completed, chemicals are added. First, a transparent agent, a defoaming agent, a 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 glue cooking tank according to the mass ratio for processing and standby; (3) The papermaking equipment is a 1880 mm long-net multi-cylinder paper machine, which produces transparent packaging paper based on the settings of the basis weight, machine speed, lip opening, shaking, pulp-to-web speed ratio, dryness control at each stage, drying cylinder temperature, sizing machine and calender parameters.

[0008] The polypentose content of the bleached kraft softwood pulp is 7-8%, and the α-cellulose content is greater than 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 180-190m 3 / h, the valve opening is 45-50%.

[0010] The slurry has a beating degree of 90-93°SR, a wet weight of 1.0-1.5 g, a temperature of 73-75°C, and a pH value of 5.5-6.0.

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

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

[0013] The surface sizing agent preparation process comprises the following steps: adding 50-55 kg of stearic acid, 16-18 kg of paraffin, 3-3.5 kg of borax, 3-3.5 kg of stearic acid emulsifier and 500-550 kg of clean water into a surface glue cooking tank, starting a stirrer, opening a steam valve, heating the temperature to 95-98 DEG C, controlling the time to be 25-30 minutes, and keeping the temperature for 15-20 minutes; then transferring the solution to a dilution tank, adding water at 80-90 DEG C, diluting the solution to a concentration of 4.8-5.2%, and 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.

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

[0015] The drying cylinder temperature of the fourdrinier multi-cylinder paper machine is as follows: pre-drying: 46±1°C, 48±1°C, 50±1°C, 55±1°C, 58±1°C, 60±1°C, 65±1°C, 70±1°C, 75±1°C, 80±1°C, 80±1°C, 85±1°C, 88±1°C, 90±1°C; post-drying: 70±1°C, 75±1°C, 78±1°C, 82±1°C, 85±1°C, 88±1°C, 90±1°C, 95±1°C; the sizing machine adopts an immersion sizing machine, the dryness entering the sizing machine is 93-95%, the dryness exiting the sizing machine is 63-65%, the line pressure of the sizing machine is 80-100kN / m; the temperature of the hard roller of the calender is 120-150°C; the pressure is 100-120kN / m; the paper dryness is 94-96%.

[0016] The transparent packaging paper is made by the production process of the transparent packaging paper described above.

[0017] Raw material selection and process optimization: 100% bleached kraft softwood pulp (Swedish Blue Forest brand) is used, with an α-cellulose content of >86% and a polypentose content of 7-8%, which makes it easier to separate into fibers during pulping and reduces the amount of chemical additives used; Physical-chemical synergistic modification: Through the series disc grinding and beating (combination of cutting and decomposition) and surface sizing process (stearic acid-paraffin composite coating), the optimal balance between fiber fineness and hydrogen bond reorganization is achieved, avoiding the recycling problem of traditional coating process; Balance between energy consumption and performance: The 1880mm fourdrinier multi-cylinder paper machine is equipped with a gradient drying temperature (front drying 46-90℃, rear drying 70-95℃), which reduces steam energy consumption while ensuring transparency.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) Swedish Blue Forest brand bleached kraft softwood pulp is used, which has appropriate content of polypentose and α-cellulose. It is easy to separate and cut during pulping, laying the foundation for high transparency. The unique pulping process, 6 DD720 disc refiners in series, with specific grinding plates and parameters, optimize the fiber structure, add transparent agents to the pulp, improve the bonding between fibers, and increase light transmittance. These measures work together to make the transparency of the finished paper ≥75%, which is much higher than that of ordinary packaging paper, and can clearly display the packaging contents and enhance the product appeal.

[0019] (2) Coniferous wood pulp fibers are inherently high in strength. Combined with a reasonable pulping process, the beating degree, wet weight and other indicators are controlled to ensure effective bonding between fibers, enhance the connection between fibers, and improve the overall strength of the paper. The product tear strength is ≥300Nm and the tear length is ≥7.5km. It can withstand large external forces during the packaging process and is not easily damaged, thus effectively protecting the product.

[0020] (3) Accurately control the paper machine process parameters, such as machine speed, lip opening, shaking, etc., to ensure that the paper quantity is uniform and the thickness is consistent. The temperature and pressure of the calender hard roller are reasonably set to make the paper smoothness on both sides ≥120s, smooth to the touch, good printing adaptability, and improve the packaging aesthetics.

[0021] (4) Reasonable pulp board selection and pulping and sizing process make the paper structure compact and the fibers arranged in an orderly manner. The low shrinkage rate is ≤0.8%, the size is stable under different environmental humidity and it is not easy to deform; the water absorption value is ≤20g / m², which can effectively prevent moisture and extend the shelf life of the packaged product.

[0022] (5) The transparent packaging paper produced can replace traditional plastic packaging products, which meets the national circular economy development requirements. Paper products can be recycled, reducing plastic pollution and having great significance for environmental protection. DETAILED DESCRIPTION

[0023] In order to make the purpose and technical solution of the present invention more clear, the present invention is further described in detail.

[0024] The following are the sources of the raw materials used in the embodiments and comparative examples: Bleached sulphate softwood pulp: Swedish Blue Forest brand bleached sulphate softwood pulp; Transparent agent: Guangzhou Chenghe Technology Co., Ltd. Defoaming agent: 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: 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 kraft softwood pulp is selected for pulping. After pulping, the pulping process is started. Six DD720 disc refiners are used for pulping in series. 1-3# are equipped with cutting-off type refiners, and 4-6# are equipped with decomposing type refiners. After setting the parameters, the pulping is performed to obtain the finished pulp. (2) After the pulping is completed, the chemical process is carried out, and a transparent agent, a defoaming agent, a bactericide and aluminum sulfate are first added to the pulp; at the same time, the surface sizing agent is prepared, and stearic acid, paraffin, borax and stearic acid emulsifier are prepared. The above raw materials are added to the surface glue cooking tank according to the mass ratio for processing and standby; (3) After completing the chemical process-related operations, the paper machine process is entered. Using a 1880 mm long-net multi-cylinder paper machine, production is carried out based on the settings of the quantitative, machine speed, lip opening, shaking, pulp-to-web speed ratio, dryness control at each stage, drying cylinder temperature, sizing machine and calender parameters, and finally transparent packaging paper is produced.

[0026] Pulp ratio: 100% Swedish Blue Forest brand bleached kraft softwood pulp, with a polypentose content of 7% and an alpha cellulose content of 87%.

[0027] Beating process: 6 DD720 disc mills in series, 1-3# cutting type grinding discs, 4-6# debonding type grinding discs, grinding power 500kw+500kw+500kw+400kw+400kw+400kw, beating concentration 3.0%, flow rate 180m 3 / h, valve opening 45%, pulp quality: beating degree 90°SR, wet weight 1.5g, temperature 73℃, pH value 5.5; Chemical Process: 1) In pulp: Transparent agent: 5kg / ton of paper, solid content 40%, pH 3, viscosity 80mPa·s; Defoamer: 150g / ton of paper, polyether, solid content 28%; Fungicide: 100g / ton of paper, organic bromine fungicide, solid content 30%; Aluminum sulfate: 15kg / ton of paper, Al2O3 content 16%; 2) Surface sizing agent: stearic acid: 10kg / ton of paper, purity 99%; Paraffin: 3kg / ton of paper, purity 99%; Stearic acid emulsifier: 3kg / ton of paper, solid content is 20%; Borax: 1kg / ton of paper, purity 99.5%; 3) Preparation process of surface sizing agent: (1) Raw materials: stearic acid, paraffin, borax, stearic acid emulsifier; (2) Preparation process: Add 50kg of stearic acid, 16kg of paraffin, 3kg of borax, 3kg of stearic acid emulsifier, and 500kg of clean water into the surface glue cooking tank, start the agitator, open the steam valve, slowly raise the temperature to 95℃, control the time to 25min, and keep warm for 15min; then transfer the solution to the dilution tank, add 80℃ hot water, dilute to a concentration of 4.8%, and set aside; Quality of surface sizing agent solution: concentration 4.8%, viscosity 15mPa·s, pH 7, temperature 80℃; Paper machine technology: 1880mm fourdrinier multi-cylinder paper machine production; a. Basis weight 49g / m; b. Vehicle speed: 150m / min; c. Lip opening: 10mm; d. Shaking: amplitude 10mm, vibration frequency 180 times / min; e. Pulp-to-net speed ratio 0.95; f. Dryness after the couch roll is 15%, after the first press is 34%, after the second press is 38%, after the third press is 41%; g. Drying cylinder temperature: Pre-baking: 45℃, 47℃, 49℃, 54℃, 57℃, 59℃, 64℃, 69℃, 74℃, 79℃, 79℃, 84℃, 87℃, 89℃; Post-baking: 69℃, 74℃, 77℃, 81℃, 84℃, 87℃, 89℃, 94℃; h. Glue applicator: immersion type glue applicator, dryness in glue applicator: 93%, dryness out of glue applicator: 63%, line pressure of glue applicator: 80kN / m; i. The temperature of the calender hard roll 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 kraft softwood pulp is selected for pulping. After pulping, the pulping process is started. Six DD720 disc refiners are used for pulping in series. 1-3# are equipped with cutting-off type refiners, and 4-6# are equipped with decomposing type refiners. After setting the parameters, the pulping is performed to obtain the finished pulp. (2) After the pulping is completed, the chemical process is carried out, and a transparent agent, a defoaming agent, a bactericide and aluminum sulfate are first added to the pulp; at the same time, the surface sizing agent is prepared, and stearic acid, paraffin, borax and stearic acid emulsifier are prepared. The above raw materials are added to the surface glue cooking tank according to the mass ratio for processing and standby; (3) After completing the chemical process-related operations, the paper machine process is entered. Using a 1880 mm long-net multi-cylinder paper machine, production is carried out based on the settings of the quantitative, machine speed, lip opening, shaking, pulp-to-web 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 kraft softwood pulp, 7% polypentose content, 87% α-cellulose content. It is easy to separate and cut during pulping, and the finished paper has high transparency.

[0030] Pulping process: 6 DD720 disc refiners in series, 1-3# cutting-off type refiners, 4-6# decomposition type refiners, pulping power 500kw+500kw+500kw+400kw+400kw+400kw, pulping concentration 3.5%, flow rate 190m3 / h, valve opening 50%, pulp quality: beating degree 93°SR, wet weight 1.0g, temperature 75℃, pH value 6.0.

[0031] Chemical Process: 1) In pulp: Transparent agent: 8kg / ton of paper, solid content 40%, pH 3, viscosity 80mPa·s; Defoamer: 200g / ton of paper, polyether, solid content 28%; Fungicide: 200g / ton of paper, organic bromine fungicide, solid content 30%; Aluminum sulfate: 20kg / ton of paper, Al2O3 content 16%; 2) Surface sizing agent: stearic acid: 15kg / ton of paper, purity 99%; Paraffin: 5kg / ton of paper, purity 99%; Stearic acid emulsifier: 3.5kg / ton of paper, purity 99.5%; Borax: 3kg / ton of paper; 3) Preparation process of surface sizing agent: (1) Raw materials: stearic acid, paraffin, borax, stearic acid emulsifier; (2) Preparation process: Add 55kg of stearic acid, 18kg of paraffin, 3.5kg of borax, 3.5kg of stearic acid emulsifier, and 550kg of clean water into the surface glue cooking tank, start the agitator, open the steam valve, slowly raise the temperature to 98℃, control the time to 30min, and keep warm for 20min; then transfer the solution to the dilution tank, add 90℃ hot water, dilute to a concentration of 5.2%, and set aside; Quality of surface sizing agent solution: concentration 5.2%; viscosity 25mPa·s; pH 7.5; temperature 90℃; Paper machine technology: 1880mm fourdrinier multi-cylinder paper machine production; a. Basis weight 51g / m b. Speed: 180m / min c. Lip opening: 12mm d. Shaking: amplitude 20mm, vibration frequency 230 times / min e. Pulp-to-net speed ratio 0.97; f. Dryness of the roller is 17%, dryness of the first press is 36%, dryness of the second press is 40%, 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-baking: 71℃, 76℃, 79℃, 83℃, 86℃, 89℃, 91℃, 96℃; h. Glue applicator: immersion type glue applicator, inlet dryness: 95%, outlet dryness: 65%, glue applicator line pressure: 100kN / m; i. Calender hard roll temperature 150℃, pressure 120kN / m; j. Paper dryness: 96%.

[0032] Example 3 The production process of transparent packaging paper includes the following steps: (1) 100% bleached kraft softwood pulp is selected for pulping. After pulping, the pulping process is started. Six DD720 disc refiners are used for pulping in series. 1-3# are equipped with cutting-off type refiners, and 4-6# are equipped with decomposing type refiners. After setting the parameters, the pulping is performed to obtain the finished pulp. (2) After the pulping is completed, the chemical process is carried out, and a transparent agent, a defoaming agent, a bactericide and aluminum sulfate are first added to the pulp; at the same time, the surface sizing agent is prepared, and stearic acid, paraffin, borax and stearic acid emulsifier are prepared. The above raw materials are added to the surface glue cooking tank according to the mass ratio for processing and standby; (3) After completing the chemical process-related operations, the paper machine process is entered. Using a 1880 mm long-net multi-cylinder paper machine, production is carried out based on the settings of the quantitative, machine speed, lip opening, shaking, pulp-to-web 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 kraft softwood pulp, 7% polypentose content, 87% α-cellulose content. It is easy to separate and cut during pulping, and the finished paper has high transparency.

[0034] 3. Beating process: 6 DD720 disc refiners are connected in series for pulping, 1-3# cutting-off type refiners, 4-6# decomposition type refiners, pulping power 500kw+500kw+500kw+400kw+400kw+400kw, pulping concentration 3.3%, flow rate 185m3 / h, valve opening 48%, pulp quality: beating degree 92°SR, wet weight 1.2g, temperature 74℃, pH value 5.8.

[0035] 3. Chemical Process: 1) In pulp: Transparent agent: 7kg / ton of paper, solid content 40%, pH 3, viscosity 80mPa·s; Defoamer: 180g / ton of paper, polyether, solid content 28%; Fungicide: 150g / ton of paper, organic bromine fungicide, solid content 30%; Aluminum sulfate: 18kg / ton of paper, Al2O3 content 16%; 2) Surface sizing agent: stearic acid: 13kg / ton of paper, purity 99%; Paraffin: 4kg / ton of paper, purity 99%; Stearic acid emulsifier: 3.3 kg / ton of paper, solid content is 20%; Borax: 2kg / ton of paper, purity 99.5%; 3) Preparation process of surface sizing agent: (1) Raw materials: stearic acid, paraffin, borax, stearic acid emulsifier; (2) Preparation process: Add 53kg of stearic acid, 17kg of paraffin, 3.2kg of borax, 3.2kg of stearic acid emulsifier, and 525kg of clean water into the surface glue cooking tank, start the agitator, open the steam valve, slowly raise the temperature to 97℃, control the time to 28min, and keep warm for 18min; then transfer the solution to the dilution tank, add 85℃ hot water, dilute to a concentration of 5.0%, and set aside; Quality standard of surface sizing agent solution: concentration 5%, viscosity 20mPa·s, pH 7.3, temperature 85℃; 4. Paper machine technology: 1880mm long-wire multi-cylinder paper machine production; a. Basis weight 50g / m; b. Vehicle speed: 165m / min; c. Lip opening: 11mm; d. Shaking: amplitude 15mm, vibration frequency 200 times / min; e. Pulp-to-net speed ratio 0.96; f. Dryness after the couch roll is 16%, after the first press is 35%, after the second press is 39%, after the third press 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 type glue applicator, inlet dryness: 94%, outlet dryness: 64%, glue applicator line pressure: 90kN / m; i. Calender hard roll temperature 135℃, pressure 110kN / m; j. Paper dryness: 95%.

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

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

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

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

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

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

[0042] It can be seen from the above data that the present invention shows a high degree of stability in terms of quantitative, expansion rate and moisture. From the test data, the quantitative of all embodiments and comparative examples are within the range of 50±2g / m², the expansion rate is ≤0.8%, and the moisture is between 4-6%. This is because in the production process, the precise control of the quantitative by the paper machine process and the stable shaping of the paper structure by the overall process system make the product not significantly affected by the changes in raw materials and processes in these basic properties. Stable basic performance is the key to ensuring the reliability of packaging paper during subsequent processing and use, ensuring the consistency of product quality. The transparency of Examples 1-3 in the present invention reaches 78.2%, 78.6%, and 79.1%, respectively, all ≥75%, which is significantly better than the comparative example. The principle is that the selected Swedish Blue Forest brand bleached kraft coniferous pulp has a polypentose content of 7-8% and an α-cellulose content of >86%. This pulp board is easy to separate and cut during pulping, and can form a uniform and tight fiber network structure, providing good conditions for light transmission. 5-8kg of transparent agent is added to the pulp, which can fill the gaps between fibers, reduce light scattering, and further improve transparency. Comparative Example 1 uses Brazilian moon eucalyptus pulp board as a substitute, and the transparency is reduced to 72.6%; Comparative Example 3 reduces the amount of transparent agent in the pulp to 3kg, and the transparency is 73.5%, which fully proves the key role of raw materials and additives in the present invention in improving transparency. High transparency can make the packaging contents clearly presented and enhance the product attractiveness. The tear length of the embodiment is excellent. For example, Examples 1-3 are 8.2km, 8.4km, and 7.9km, respectively, all ≥7.5km, while in Comparative Example 2, after the pulp quality beating degree is reduced from 90-93°SR to 60-63°SR, the tear length is greatly reduced to 6.2km. This is because of the reasonable pulping process, through 6 DD720 disc refiners in series, with 1-3# cutting type refiners and 4-6# decomposition refiners, the pulping power, concentration and other parameters are accurately controlled, so that the fibers are fully divided and properly cut, forming a good interwoven structure, thereby improving the longitudinal strength of the paper. The higher tear strength (Examples 1-3 and most comparative examples are ≥300Nm) is also due to this fiber structure and the components such as stearic acid and paraffin in the surface sizing agent that enhance the connection between fibers, ensuring that the paper can withstand large external forces during the packaging process and is not easily damaged. The average smoothness of Examples 1-3 on the front and back sides is 135s, 145s, and 142s, respectively, all ≥120s, which is significantly better than Comparative Example 2 (110s) and Comparative Example 4 (102s). During the pulping process, the appropriate grinding disc combination and process parameters make the fibers refined and evenly distributed, laying the foundation for the flatness of the paper surface. The special formula and preparation process of the surface sizing agent form a uniform film on the surface of the paper, further improving the smoothness. Good smoothness not only makes the paper feel comfortable, but more importantly, it is conducive to printing, making the printed pattern clearer and more exquisite, and improving the overall aesthetics of the packaging.The water absorption values ​​of Examples 1-3 are 17.6 g / m², 18.3 g / m², and 16.6 g / m², respectively, all ≤ 20 g / m². Chemicals such as aluminum sulfate added to the pulp react with the fibers to form a protective film on the fiber surface, reducing the water absorption of the paper. Ingredients such as stearic acid and paraffin in the surface sizing agent also act as a waterproof barrier. After reducing the amount of transparent agent in the pulp in Comparative Example 3, the water absorption value increased to 19.2 g / m², close to the upper limit, indicating that the rational use of chemicals in the present invention is crucial to controlling water absorption, and 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: The following steps are involved: (1) 100% bleached kraft softwood pulp was selected for pulping. After pulping, the pulping process was started. Six DD720 disc refiners were used for pulping in series. No. 1 to No. 3 were equipped with cutting-off type refiners, and No. 4 to No. 6 were equipped with decomposing type refiners. After setting the parameters, the pulping process was carried out to obtain the finished pulp. (2) After pulping is completed, chemicals are added. First, a transparent agent, a defoaming agent, a 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 glue cooking tank according to the mass ratio for processing and standby; (3) The papermaking equipment is a 1880 mm long-net multi-cylinder paper machine, which produces transparent packaging paper based on the settings of the basis weight, machine speed, lip opening, shaking, pulp-to-web speed ratio, dryness control at each stage, drying cylinder temperature, sizing machine and calender parameters.

2. The production process of transparent packaging paper according to claim 1, characterized in that: The polypentose content of the bleached kraft softwood pulp is 7-8%, and the α-cellulose content is greater than 86%.

3. The production process of transparent packaging paper according to claim 1, characterized in that: 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 180-190m 3 / h, the valve opening is 45-50%.

4. The production process of transparent packaging paper according to claim 1, characterized in that: The pulp has a beating degree of 90-93°SR, a wet weight of 1.0-1.5 g, a temperature of 73-75°C, and a pH value of 5.5-6.

0.

5. The production process of transparent packaging paper according to claim 1, characterized in that: The amount of the transparent agent added is 5-8kg / ton of paper, the solid content is ≥40%, the pH is 2-4, and the viscosity is 50-100mPa·s; the amount of the defoamer added is 150-200g / ton of paper, the defoamer is a polyether, and the solid content is ≥8%; the amount of the fungicide added is 100-200g / ton of paper, it is an organic bromine fungicide, and the solid content is ≥20%; the amount of aluminum sulfate added is 15-20kg / ton of paper, and the Al2O3 content is ≥15.6%.

6. The production process of transparent packaging paper according to claim 1, characterized in that: The added amount of stearic acid is 10-15kg / ton of paper, with a purity of ≥99%; the added amount of paraffin is 3-5kg / ton of paper, with a purity of ≥99%; the added amount of borax is 1-3kg / ton of paper, with a purity of ≥99.5%; and the added amount of stearic acid emulsifier is 3-3.5kg / ton of paper, with a solid content of ≥20%.

7. The production process of transparent packaging paper according to claim 1, characterized in that: The surface sizing agent preparation process comprises the following steps: adding 50-55 kg of stearic acid, 16-18 kg of paraffin, 3-3.5 kg of borax, 3-3.5 kg of stearic acid emulsifier and 500-550 kg of clean water into a surface glue cooking tank, starting a stirrer, opening a steam valve, heating the temperature to 95-98 DEG C, controlling the time to be 25-30 minutes, and keeping the temperature for 15-20 minutes; then transferring the solution to a dilution tank, adding water at 80-90 DEG C, diluting the solution to a concentration of 4.8-5.2%, and 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.

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

9. The production process of transparent packaging paper according to claim 1, characterized in that: The drying cylinder temperature of the fourdrinier multi-cylinder paper machine is as follows: pre-drying: 46±1°C, 48±1°C, 50±1°C, 55±1°C, 58±1°C, 60±1°C, 65±1°C, 70±1°C, 75±1°C, 80±1°C, 80±1°C, 85±1°C, 88±1°C, 90±1°C; post-drying: 70±1°C, 75±1°C, 78±1°C, 82±1°C, 85±1°C, 88±1°C, 90±1°C, 95±1°C; the sizing machine adopts an immersion sizing machine, the dryness entering the sizing machine is 93-95%, the dryness exiting the sizing machine is 63-65%, the line pressure of the sizing machine is 80-100kN / m; the temperature of the hard roller of the calender is 120-150°C; the pressure is 100-120kN / m; the paper dryness is 94-96%.

10. A transparent packaging paper, characterized in that: The transparent packaging paper is prepared by the production process of any one of claims 1 to 9.

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