Re-pulpable paper box skylight paper and production process thereof

Abstract

The invention discloses skylight paper for a repulpable paper box and a production process of the skylight paper. The production process comprises the working procedures of raw material selection, repulping, pulp grinding, pulp mixing, chemical additive adding, screening and purifying, paper machine net feeding and forming, squeezing, first-stage drying, in-machine dip coating, second-stage drying and curling. The finally prepared paper box skylight paper has excellent physical strength, heat sealing performance and good hand feeling by adding regenerated fibers and synthetic fibers into the raw materials, using an inclined wire paper machine to make paper, adopting in-machine dip coating and selecting dip coating, can be re-pulped and recycled, can completely replace an existing plastic skylight product, and has a wide application prospect. The current green, environment-friendly and sustainable development concepts are met.

Description

Technical Field

[0001] The invention belongs to the field of papermaking, and in particular relates to a production process of repulpable paper box skylight paper. Background Art

[0002] Tissue paper is a fast-moving consumer product that is necessary for daily life. With the steady growth of China's economy, the diversification and high-end domestic consumer demand, the consumption of tissue paper in my country has been increasing year by year. In recent years, driven by environmental protection policies, tissue paper companies have turned to green packaging of their products to take the opportunity to improve their market competitiveness and increase customer recognition and favorability.

[0003] Boxed tissues are one of many paper products for daily use. Traditional tissue boxes are open-mouthed, making them susceptible to moisture. Dust, bacteria, etc. can easily fall into the box and contaminate the tissues. After about two-thirds of the tissues are used, they fall back into the box due to gravity, making it impossible to continuously draw paper, resulting in a poor user experience. Later, people solved this problem by coating the skylight of the box. Patent 2003101010089 mentioned that the window film used is polyethylene film, and patent 2016106167286 mentioned that the window film is PET film. These window films are all plastic products and cannot be directly re-pulped. When recycling the box, they must be separated before they can be re-pulped. The process is cumbersome. For convenience, the recycling personnel will landfill or incinerate the entire box as non-recyclable garbage, polluting the environment and wasting resources. Patent 2022101943943 proposes to use cellophane instead of plastic film. Cellophane is made from modified natural fiber raw materials. Although it is degradable in the natural environment, it is still not repulpable. Cellophane will generate small irregular flaky materials during the repulping process. These flaky materials are difficult to screen out from the system, thus affecting the repulping of the entire carton. In this context, it is urgent to develop a repulpable carton skylight paper to ensure that the entire carton can smoothly enter the repulping system for reuse.

[0004] The comprehensive index requirements of skylight paper are relatively high, and it must have the following properties at the same time: First, it must have a high tear resistance to prevent the tangent opening edge from cracking due to frequent pulling; second, it must have a good feel, that is, a lower softness (the lower the softness value, the softer the paper); third, it must have a high folding resistance to prevent the skylight paper from breaking due to frequent bending when drawing paper; fourth, it must have a high wet strength to prevent damage after being wetted by humans; fifth, it must have a high dry strength to ensure that it does not break during processing and use; sixth, it must have a high heat sealing performance to ensure that it is firmly bonded to the paper box and avoid the use of glue. On the basis of meeting the above requirements, skylight paper must also have repulpability to meet the standard requirements of "GB / T 43588-2023 Method for evaluating the recyclability of paper, paperboard and paper products". During the development of this patent, technicians collected a large number of existing paper products. Currently, there are many types of paper that can be recycled and repulped on the market, but their performance is far from meeting the use requirements of boxed paper towels. This is mainly manifested in the three indicators of higher physical strength, better feel and repulpability, which are contradictory to each other and cannot be achieved at the same time. Summary of the invention

[0005] The purpose of the present invention is to provide a production process for repulpable paper box skylight paper, by adding recycled fibers with long length and good hygroscopicity to plant fiber raw materials, the paper has excellent tearing strength and good hygroscopicity, and the paper with good hygroscopicity generally has a good feel; by using ultrafine fibers in synthetic fibers, the softness, folding resistance and wear resistance of base paper are improved; by using low-melting-point sheath-core fibers in synthetic fibers, the bonding strength of ultrafine fibers with plant fibers and recycled fibers is improved; by using an inclined-net paper machine, the base paper obtains a better uniformity; by using an immersion coating method and screening an aqueous bio-based polyurethane emulsion as a coating, the physical strength of the paper after impregnation is greatly improved, and it has repulpability and heat sealability. Finally, the skylight paper prepared by the present invention has excellent physical strength and excellent feel, and can be heat-sealed and repulped, which can meet the needs of actual scenarios.

[0006] The production process of the skylight paper is realized through the following technical scheme: 40-50% bleached coniferous wood pulp, 20-30% bleached hardwood wood pulp, 10-20% recycled fiber, and 10-20% synthetic fiber are used as raw materials, wherein the recycled fiber is one of tencel fiber, modal fiber, acetate fiber, and viscose fiber, and the length is 10-15mm. Since the fiber length of the recycled fiber is much longer than that of the wood pulp fiber, the tear strength of the paper can be greatly improved. On the other hand, it has strong hydrophilicity and good dispersibility in water, avoiding adverse effects on the uniformity of the paper. In addition, the recycled fiber has good hygroscopicity, so that the prepared paper has a good feel, but the fiber length and amount must be strictly controlled during use. If the fiber length is too short or the amount is too little, the tear strength cannot meet the requirements, and if the fiber length is too long or the amount is too much, it is very easy to form flocs.

[0007] Synthetic fibers are composed of 5-10% ultrafine fibers and 5-10% core-skin fibers. The ultrafine fibers are 6-8mm long and 1-5μm fine. They are one of polyethylene fibers, polypropylene fibers, and polyester fibers. Ultrafine fibers are long and thin, which can make the base paper have better softness, folding resistance, and wear resistance. However, they have poor hydrophilicity and are prone to produce bubbles during papermaking. At the same time, they cannot form hydrogen bonds with plant fibers, which will reduce the strength of the paper. Therefore, their dosage and length need to be strictly controlled. The melting point of the core-skin fiber cortex is 85-100℃, and the length is 4-6mm. The core-skin fiber cortex is a low-melting-point hot-melt fiber. After melting, it can increase the bonding between synthetic fibers and plant fibers and recycled fibers, thereby improving the strength of the base paper and reducing hair loss and powder loss.

[0008] During pulping, bleached coniferous wood pulp and bleached broadleaf wood pulp are mixed for pulping and pulping. To ensure the softness and comfort of the paper, the beating degree is minimized during pulping, and the beating degree is controlled to be 15-20°SR. Regenerated fibers and synthetic fibers are only mixed for pulping. To avoid entanglement of long fibers, the pulping concentration is controlled to be 0.1-0.5%. 0.5-0.8% of dispersant and 0.2-0.5% of defoaming agent are added during pulping.

[0009] The bleached conifer pulp and bleached broadleaf pulp after pulping are mixed with the recycled fiber and synthetic fiber pulp after crushing, and then chemical additives are added to the pulp, including 1-3% wet strength agent relative to the absolute dry raw material, the wet strength agent type is polyamide epichlorohydrin, 2-4% dry strength agent, the dry strength agent type is one or more of cationic starch, polyacrylamide, carboxymethyl cellulose, 1-3% sizing agent in the pulp, the sizing agent type is alkyl ketene dimer. Then the pulp is screened and purified and then formed on the inclined wire paper machine. In order to ensure good dispersion of the pulp, the concentration of the paper machine should be lower, which is 0.025-0.05%. Due to the low strength of the base paper, the speed of the paper machine should not be too high, and is controlled to be 100-120m / min. Then after pressing, it enters the first stage of drying. The first stage of drying uses a large cylinder drying, and the drying temperature is 100-120℃.

[0010] The dried base paper is dip-coated in the machine. The strength indexes of the coated paper are greatly improved. The coating material is a water-based bio-based polyurethane emulsion with repulpability and heat sealing properties. The coating concentration needs to be properly controlled. If the coating concentration is too high, the coating amount is large, resulting in the paper being unable to be broken up and repulped. If the coating concentration is too low, the coating amount is small, and the strength indexes cannot meet the requirements. The coating concentration should be controlled at 10-20%, and the coating amount should be controlled at 5-10g / m 2Then it enters the second drying stage, which adopts double-sided suspension drying and large-cylinder drying. Double-sided suspension drying can reduce the difference between the two sides of the paper and avoid the phenomenon of single-sided inward curling of the paper. Large-cylinder drying is a secondary processing and finishing of the paper to make it smoother. The temperature of double-sided suspension drying is 80-100℃, and the temperature of large-cylinder drying is 90-120℃. Finally, the paper enters the curling process.

[0011] The paper finally prepared has higher tear strength, dry and wet tensile strength, folding resistance, bursting resistance, heat sealing strength, better hand feel, and higher recyclability. DETAILED DESCRIPTION

[0012] The raw materials are 40-50% bleached conifer pulp, 20-30% bleached hardwood pulp, 10-20% recycled fiber, and 10-20% synthetic fiber, wherein the recycled fiber is one of tencel fiber, modal fiber, acetate fiber, and viscose fiber, and the length is 10-15mm, and the synthetic fiber is composed of 5-10% ultrafine fiber and 5-10% sheath-core fiber. The ultrafine fiber is 6-8mm long and 1-5μm fine, and the type is one of polyethylene fiber, polypropylene fiber, and polyester fiber. The melting point of the sheath-core fiber is 85-100℃, and the length is 4-6mm.

[0013] During pulping, bleached coniferous wood pulp and bleached broadleaf wood pulp are mixed for pulping and pulping, and the beating degree during pulping is controlled to be 15-20°SR. Regenerated fiber and synthetic fiber are only mixed for pulping, and the pulping concentration is controlled to be 0.1-0.5%. During pulping, 0.5-0.8% of dispersant and 0.2-0.5% of defoamer are added.

[0014] The bleached conifer pulp and bleached broadleaf pulp after pulping are mixed with the recycled fiber and synthetic fiber pulp after crushing, and chemical additives are added to the pulp, including 1-3% of wet strength agent relative to the absolute dry raw material, the wet strength agent type is polyamide epichlorohydrin, including 2-4% of dry strength agent, the dry strength agent type is one or more of cationic starch, cationic polyacrylamide, and carboxymethyl cellulose, including 1-3% of pulp sizing agent, the sizing agent type is alkyl ketene dimer. Then the pulp is screened and purified and then formed on the inclined wire paper machine, the concentration of the wire is 0.025-0.05%, the speed of the paper machine is 100-120m / min, and then the wet paper web is pressed and enters the first stage of drying, the first stage of drying uses a large cylinder drying, and the drying temperature is 100-120℃.

[0015] After drying, the base paper is obtained, and the base paper is dip-coated in the machine. The coating is a water-based bio-based polyurethane emulsion, the coating concentration is controlled to be 10-20%, and the coating amount is 5-10g / m 2Then it enters the second drying stage, which adopts the double-sided suspension drying and large cylinder drying methods. The double-sided suspension drying temperature is 80-100℃, and the large cylinder drying temperature is 90-120℃. Finally, the paper enters the curling process.

[0016] The final prepared paper has high strength, good hand feel, and high re-pulpability. The physical indicators of the re-pulpable box skylight paper are shown in Table 1.

[0017] Table 1 Physical indicators of repulpable carton skylight paper

[0018]

[0019] Example 1

[0020] The raw materials are 40% bleached conifer pulp, 30% bleached hardwood pulp, 20% recycled fiber and 10% synthetic fiber, of which the recycled fiber is tencel fiber with a length of 10mm, and the synthetic fiber is composed of 5% ultrafine fiber and 5% sheath-core fiber. The ultrafine fiber is 8mm long and 1μm fine, and is polyethylene fiber. The sheath-core fiber has a melting point of 85℃ and a length of 4mm.

[0021] During pulping, bleached coniferous wood pulp and bleached broadleaf wood pulp were mixed for pulping and pulping, and the beating degree during pulping was controlled to be 20°SR. Regenerated fiber and synthetic fiber were only mixed for pulping, and the pulping concentration was controlled to be 0.5%. 0.5% dispersant and 0.2% defoamer were added during pulping.

[0022] The pulped bleached coniferous wood pulp, bleached broadleaf wood pulp and the crushed recycled fiber and synthetic fiber pulp are mixed, and chemical additives are added to the pulp, including 1% of the wet strength agent polyamide epichlorohydrin, 2% of the dry strength agent cationic starch, and 1% of the pulp sizing agent alkyl ketene dimer relative to the absolute dry raw material. Then the pulp is screened and purified and formed on the inclined wire paper machine. The concentration of the wire is 0.025%, and the speed of the paper machine is 100m / min. Then the wet paper web is pressed and enters the first stage of drying. The first stage of drying uses a large cylinder drying at a drying temperature of 100℃.

[0023] After drying, the base paper is obtained, and the base paper is dip-coated in the machine. The coating is a water-based bio-based polyurethane emulsion, the coating concentration is controlled to be 10%, and the coating amount is 5g / m 2 Then it enters the second drying stage, which uses double-sided suspension drying and large-cylinder drying. The double-sided suspension drying temperature is 80°C and the large-cylinder drying temperature is 90°C. Finally, the paper enters the curling process.

[0024] Example 2

[0025] The raw materials are 42% bleached conifer pulp, 28% bleached hardwood pulp, 18% recycled fiber and 12% synthetic fiber, of which the recycled fiber is modal fiber with a length of 10mm, and the synthetic fiber is composed of 6% ultrafine fiber and 6% sheath-core fiber. The ultrafine fiber is 8mm long and 1μm fine, and is polyethylene fiber. The sheath-core fiber has a melting point of 85℃ and a length of 4mm.

[0026] During pulping, bleached coniferous wood pulp and bleached broadleaf wood pulp were mixed for pulping and pulping, and the beating degree during pulping was controlled to be 20°SR. Regenerated fiber and synthetic fiber were only mixed for pulping, and the pulping concentration was controlled to be 0.5%. 0.5% dispersant and 0.2% defoamer were added during pulping.

[0027] The bleached coniferous wood pulp and bleached broadleaf wood pulp after refining are mixed with the recycled fiber and synthetic fiber pulp after crushing, and chemical additives are added to the pulp, including 1% of the wet strength agent polyamide epichlorohydrin, 2% of the dry strength agent cationic starch, and 1% of the sizing agent alkyl ketene dimer in the pulp relative to the absolute dry raw material. Then the pulp is screened and purified and formed on the inclined wire paper machine. The concentration of the wire is 0.025%, and the speed of the paper machine is 100m / min. Then the wet paper web is pressed and enters the first stage of drying. The first stage of drying adopts a large cylinder drying, and the drying temperature is 100℃.

[0028] After drying, the base paper is obtained, and the base paper is dip-coated in the machine. The coating is a water-based bio-based polyurethane emulsion, the coating concentration is controlled to be 10%, and the coating amount is 5g / m 2 Then it enters the second drying stage, which uses double-sided suspension drying and large-cylinder drying. The double-sided suspension drying temperature is 80°C and the large-cylinder drying temperature is 90°C. Finally, the paper enters the curling process.

[0029] Example 3

[0030] The raw materials are 44% bleached conifer pulp, 26% bleached hardwood pulp, 16% recycled fiber and 14% synthetic fiber, of which the recycled fiber is acetate fiber with a length of 13mm, and the synthetic fiber is composed of 7% ultrafine fiber and 7% core-skin fiber. The ultrafine fiber is 7mm long and 3μm fine, and is polypropylene fiber. The melting point of the core-skin fiber is 90℃ and the length is 5mm.

[0031] During pulping, bleached coniferous wood pulp and bleached broadleaf wood pulp were mixed for pulping and pulping, and the beating degree during pulping was controlled to be 18°SR. Regenerated fiber and synthetic fiber were only mixed for pulping, and the pulping concentration was controlled to be 0.3%. During pulping, 0.7% of dispersant and 0.3% of defoaming agent were added.

[0032] The bleached conifer pulp and bleached broadleaf pulp after refining are mixed with the recycled fiber and synthetic fiber pulp after crushing, and chemical additives are added to the pulp, including 2% of the wet strength agent polyamide epichlorohydrin, 3% of the dry strength agent cationic polyacrylamide, and 2% of the sizing agent alkyl ketene dimer relative to the absolute dry raw material. Then the pulp is screened and purified and formed on the inclined wire paper machine. The concentration of the wire is 0.035%, and the speed of the paper machine is 110m / min. Then the wet paper web is pressed and enters the first stage of drying. The first stage of drying adopts a large cylinder drying, and the drying temperature is 110℃.

[0033] After drying, the base paper is obtained, and the base paper is dip-coated in the machine. The coating is a water-based bio-based polyurethane emulsion, the coating concentration is controlled to be 15%, and the coating amount is 8.5g / m 2 Then it enters the second drying stage, which uses double-sided suspension drying and large-cylinder drying. The double-sided suspension drying temperature is 90°C and the large-cylinder drying temperature is 100°C. Finally, the paper enters the curling process.

[0034] Example 4

[0035] The raw materials are 46% bleached conifer pulp, 24% bleached hardwood pulp, 14% recycled fiber and 16% synthetic fiber. The recycled fiber is viscose fiber with a length of 13mm. The synthetic fiber is composed of 8% ultrafine fiber and 8% core-skin fiber. The ultrafine fiber is 7mm long and 3μm fine. It is polypropylene fiber. The melting point of the core-skin fiber is 90℃ and the length is 5mm.

[0036] During pulping, bleached coniferous wood pulp and bleached broadleaf wood pulp were mixed for pulping and pulping, and the beating degree during pulping was controlled to be 18°SR. Regenerated fiber and synthetic fiber were only mixed for pulping, and the pulping concentration was controlled to be 0.3%. During pulping, 0.7% of dispersant and 0.3% of defoaming agent were added.

[0037] The pulped bleached coniferous wood pulp, bleached broadleaf wood pulp and the crushed recycled fiber and synthetic fiber pulp are mixed, and chemical additives are added to the pulp, including 2% of the wet strength agent polyamide epichlorohydrin, 3% of the dry strength agent cationic starch and cationic polyacrylamide, and 2% of the sizing agent alkyl ketene dimer relative to the absolute dry raw material. Then the pulp is screened and purified and formed on the inclined wire paper machine. The concentration of the wire is 0.035%, and the speed of the paper machine is 110m / min. Then the wet paper web is pressed and enters the first stage of drying. The first stage of drying uses a large cylinder drying at a drying temperature of 110℃.

[0038] After drying, the base paper is obtained, and the base paper is dip-coated in the machine. The coating is a water-based bio-based polyurethane emulsion, the coating concentration is controlled to be 15%, and the coating amount is 8.5g / m 2Then it enters the second drying stage, which uses double-sided suspension drying and large-cylinder drying. The double-sided suspension drying temperature is 90°C and the large-cylinder drying temperature is 100°C. Finally, the paper enters the curling process.

[0039] Example 5

[0040] The raw materials are 48% bleached conifer pulp, 22% bleached hardwood pulp, 12% recycled fiber and 18% synthetic fiber. The recycled fiber is Tencel fiber with a length of 12mm. The synthetic fiber is composed of 9% ultrafine fiber and 9% core-skin fiber. The ultrafine fiber is 6mm long and 5μm fine. It is polyester fiber. The melting point of the core-skin fiber is 100℃ and the length is 6mm.

[0041] During pulping, bleached coniferous wood pulp and bleached broadleaf wood pulp were mixed for pulping and pulping, and the beating degree during pulping was controlled to be 15°SR. Regenerated fiber and synthetic fiber were only mixed for pulping, and the pulping concentration was controlled to be 0.1%. 0.8% of dispersant and 0.5% of defoamer were added during pulping.

[0042] The bleached conifer pulp and bleached broadleaf pulp after refining are mixed with the recycled fiber and synthetic fiber pulp after crushing, and chemical additives are added to the pulp, including 3% of wet strength agent polyamide epichlorohydrin, 4% of dry strength agent carboxymethyl cellulose, and 3% of sizing agent alkyl ketene dimer relative to the absolute dry raw material. Then the pulp is screened and purified and formed on the inclined wire paper machine. The concentration of the wire is 0.05%, and the speed of the paper machine is 120m / min. Then the wet paper web is pressed and enters the first stage of drying. The first stage of drying adopts a large cylinder drying, and the drying temperature is 120℃.

[0043] After drying, the base paper is obtained, and the base paper is dip-coated in the machine. The coating is a water-based bio-based polyurethane emulsion, the coating concentration is controlled to be 20%, and the coating amount is 10g / m 2 Then it enters the second drying stage, which adopts the double-sided suspension drying and large cylinder drying method. The double-sided suspension drying temperature is 100℃ and the large cylinder drying temperature is 120℃. Finally, the paper enters the curling process.

[0044] Example 6

[0045] The raw materials are 50% bleached conifer pulp, 20% bleached hardwood pulp, 10% recycled fiber and 20% synthetic fiber. The recycled fiber is Tencel fiber with a length of 15mm. The synthetic fiber is composed of 10% ultrafine fiber and 10% core-skin fiber. The ultrafine fiber is 6mm long and 5μm fine. It is polyester fiber. The melting point of the core-skin fiber is 100℃ and the length is 6mm.

[0046] During pulping, bleached coniferous wood pulp and bleached broadleaf wood pulp were mixed for pulping and pulping, and the beating degree during pulping was controlled to be 15°SR. Regenerated fiber and synthetic fiber were only mixed for pulping, and the pulping concentration was controlled to be 0.1%. 0.8% of dispersant and 0.5% of defoamer were added during pulping.

[0047] The bleached conifer pulp and bleached broadleaf pulp after refining are mixed with the recycled fiber and synthetic fiber pulp after crushing, and chemical additives are added to the pulp, including 3% of the wet strength agent polyamide epichlorohydrin, 4% of the dry strength agent cationic polyacrylamide and carboxymethyl cellulose, and 3% of the sizing agent alkyl ketene dimer in the pulp relative to the absolute dry raw material. Then the pulp is screened and purified and formed on the inclined wire paper machine. The concentration of the wire is 0.05%, and the speed of the paper machine is 120m / min. Then the wet paper web is pressed and enters the first stage of drying. The first stage of drying adopts a large cylinder drying, and the drying temperature is 120℃.

[0048] After drying, the base paper is obtained, and the base paper is dip-coated in the machine. The coating is a water-based bio-based polyurethane emulsion, the coating concentration is controlled to be 20%, and the coating amount is 10g / m 2 Then it enters the second drying stage, which adopts the double-sided suspension drying and large cylinder drying method. The double-sided suspension drying temperature is 100℃ and the large cylinder drying temperature is 120℃. Finally, the paper enters the curling process.

[0049] The repulpable carton skylight paper prepared in the above Examples 1-6 was tested, and the test results are shown in Table 2.

[0050] Table 2 Physical properties of repulpable carton skylight paper prepared in Examples 1-6

[0051]

[0052] The data obtained in this study are obtained on the basis of a large number of experiments and are not common knowledge. The above examples are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above examples. All variations that can be directly derived or associated with the contents disclosed by ordinary technicians in this field should belong to the protection scope of the present invention.

Claims

1. A repulpable carton skylight paper and its production process, including raw material selection, crushing, refining, pulping, adding chemical additives, screening and purification, paper machine screen forming, pressing, first stage drying, machine impregnation coating, second stage drying, curling process, characterized in that: The raw materials include 40-50% bleached conifer pulp, 20-30% bleached hardwood pulp, 10-20% recycled fiber, and 10-20% synthetic fiber, wherein the recycled fiber is one of tencel fiber, modal fiber, acetate fiber, and viscose fiber, and has a length of 10-15 mm, and the synthetic fiber is composed of 5-10% ultrafine fiber and 5-10% sheath-core fiber, the ultrafine fiber is 6-8 mm long and 1-5 μm fine, and is one of polyethylene fiber, polypropylene fiber, or polyester fiber, and the sheath-core fiber has a melting point of 85-100° C. and a length of 4-6 mm; The crushing and refining are respectively crushed and refined, wherein the bleached coniferous wood pulp and the bleached hardwood wood pulp are mixed and crushed, and then refined, and the beating degree after refining is 15-20°SR, the regenerated fiber and the synthetic fiber are mixed and crushed, and the crushing concentration is 0.1-0.5%, and 0.5-0.8% of dispersant and 0.2-0.5% of defoaming agent are added during crushing; The chemical additives mentioned above refer to adding 1-3% of wet strength agent, 2-4% of dry strength agent and 1-3% of sizing agent in the slurry relative to the absolute dry raw materials; The paper machine is formed on the web, the paper machine is a slant web paper machine, the web concentration is 0.025-0.05%, and the machine speed is 100-120m / min; The first stage of drying is a large vat drying at a drying temperature of 100-120°C; For the in-machine dip coating, the coating material is a water-based bio-based polyurethane emulsion with re-slurryability and heat-sealing properties, the coating concentration is 10-20%, and the coating amount is 5-10g / m 2 ; The second stage of drying is a double-sided suspension oven drying and a large vat drying method, the double-sided suspension drying temperature is 80-100°C, and the large vat drying temperature is 90-120°C; The repulpable carton skylight paper has a quantitative index of 40-60g / m 2 , thickness 0.070-0.130mm, longitudinal tear strength is 1210-1610mN, transverse tear strength is 2354-2910mN, longitudinal wet tensile strength is 2.10-4.05kN / m, transverse wet tensile strength is 0.53-1.01kN / m, longitudinal dry tensile strength is 4.20-8.10kN / m, transverse dry tensile strength is 1.40-2.70kN / m, longitudinal folding endurance is 2815-3250 times, transverse folding endurance is 621-837 times, longitudinal softness is 104-158mN, transverse softness is 522-626mN, bursting strength is 128-409kPa, heat sealing strength is 0.13-0.50kN / m, and the recyclability evaluation score is 95-98 points.

2. According to claim 1, the wet strength agent is polyamide epichlorohydrin, the dry strength agent is one of cationic starch, cationic polyacrylamide, and carboxymethyl cellulose, and the internal sizing agent is alkyl ketene dimer.

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