Reverse UV paper and preparation method thereof

Abstract

The invention relates to reverse UV paper and a preparation method thereof. The preparation method comprises the following steps: pulping, preparing pulp, dehydrating and forming a net part, squeezing by a squeezing part, drying by a front drying part, sizing, drying by a rear drying part, calendering by a calender, coiling, packaging and warehousing. Wherein in the sizing step, gelatinized starch with the solid content of 10-12% is adopted as a sizing material, the viscosity of the sizing material is 10-20 cps, the sizing temperature is 70-78 DEG C, and the sizing amount is 3.5 g / m < 2 >-4.5 g / m < 2 >. Different from the prior art, according to the technical scheme, in the sizing step, a large amount of sizing agent adheres to the paper surface by increasing the sizing temperature and reducing the viscosity and the solid content, so that the capillary action of the paper surface is reduced, short-chain starch in the sizing agent is linked with fibers, the fibers are endowed with hydrophobic groups, the hydrophobicity of the paper surface is increased, and the paper surface hydrophobicity is improved. And the UV ink forms a floating layer on the paper surface and is rapidly cured, so that the effect of embossment three-dimensional texture is achieved.

Description

Technical Field

[0001] This application relates to the field of papermaking, and in particular to a reverse UV paper and its preparation method. Background Technology

[0002] The core of reverse UV technology is to utilize the mutual repulsion effect of varnish and UV ink to create an embossed three-dimensional texture on the same sheet of paper, as well as a strong contrast between gloss and matte, thereby enhancing the quality and visual depth of the print. It is often used in high-end packaging, cultural and creative industries, and other similar applications.

[0003] When existing white cardboard is reverse-cured using UV printing, it can also absorb UV ink, resulting in insufficient UV ink remaining on the paper surface. As a result, the three-dimensional effect is lost during the rapid curing process of the ink. Summary of the Invention

[0004] In view of the above problems, this application provides a reverse UV paper suitable for reverse UV printing and a method for preparing the same. This method reduces the absorption of UV ink by the paper, allowing the UV ink to form a floating layer on the paper surface and cure rapidly, achieving an embossed three-dimensional texture effect.

[0005] The first aspect of this application provides a method for preparing reverse UV paper, the method comprising the following steps:

[0006] Pulping, pulp preparation, dewatering and forming at the screen section, pressing at the press section, drying at the pre-drying section, applying sizing with a sizing machine, drying at the post-drying section, calendering with a calendering machine, winding, packaging and warehousing;

[0007] In the pulp preparation step, the surface and bottom layers of pulp are chemical softwood pulp and chemical hardwood pulp, and the core layer pulp is chemimechanical pulp, waste pulp, and multi-recycled fiber.

[0008] The sizing step of the sizing machine uses gelatinized starch with a solid content of 10-12%, a viscosity of 10-20 cps, a sizing temperature of 70℃-78℃, and a sizing rate of 3.5 g / m³. 2 -4.5g / m 2 .

[0009] Applying the adhesive at a temperature above 70℃ is necessary to prevent aging of the adhesive, ensure its fluidity, and improve its penetration performance.

[0010] Unlike existing technologies, the above-mentioned technical solution provides a method in the sizing step that increases the sizing temperature, reduces viscosity and solid content, so that a large amount of sizing agent adheres to the paper surface, thereby reducing capillary action on the paper surface. The short-chain starch in the sizing agent links with the fibers, giving the fibers hydrophobic groups, which increases the hydrophobicity of the paper surface and reduces the absorption of UV ink by the paper. The UV ink forms a floating layer on the paper surface and cures rapidly, achieving an embossed three-dimensional texture effect.

[0011] Furthermore, the method for preparing the gelatinized starch includes the following steps:

[0012] Add water to corn starch and / or tapioca starch and mix well to obtain a starch slurry with a solid content of 28-30%.

[0013] Add 200 ppm of amylase to the starch slurry to obtain the first slurry;

[0014] The first slurry is heated to 80-83℃ by steam to carry out an enzymatic reaction, thereby obtaining the second slurry;

[0015] When the enzymatic digestion reaction reaches a viscosity of 50-80 cps for the second slurry, the second slurry is heated to 130°C for a gelatinization reaction to obtain the third slurry.

[0016] The third slurry is cooled and diluted to a solid content of 10-12% to obtain the adhesive.

[0017] Furthermore, while keeping the total amount of adhesive applied constant, the viscosity of the adhesive can be reduced by increasing the flow rate at the top beam.

[0018] Furthermore, during the application of the sizing agent, the pressure of the sizing roller is 25-30kN.

[0019] Furthermore, in the pulp preparation step, the surface and bottom layers consist of 30% chemically synthesized softwood pulp and 70% chemically synthesized hardwood pulp. Increasing the proportion of long fibers in the surface and bottom layers can improve the tensile index of the surface and bottom layers.

[0020] Furthermore, in the pre-drying and post-drying steps, the temperature difference between each group of drying cylinders is controlled to be ≤10℃. The drying curve is optimized, and the temperature difference between each group of drying cylinders is controlled to not exceed 10 degrees, thereby controlling paper web shrinkage, reducing internal stress in the paper, lowering the moisture content of the finished paper, and preventing fiber embrittlement during the reverse UV rapid drying process.

[0021] By combining long fiber reinforcement and drying processes, the problem of stress concentration caused by rapid curing of UV inks during printing is solved, which leads to easy cracking when creased and folded.

[0022] Furthermore, in the dehydration and forming step of the mesh section, the mesh concentration of the surface layer is 0.25%-0.35%, the mesh concentration of the core layer is 1.1%-1.4%, and the mesh concentration of the bottom layer is 0.25%-0.35%.

[0023] After the pulp is adjusted in concentration and impurities and internal air are removed by the flow system, it is fed to the wire from the headbox. The top layer has a headbox concentration of 0.25%-0.35% and is sprayed from the top layer headbox to the forming wire to form the wet web of the top layer base paper. The core layer has a headbox concentration of 1.1%-1.4% and is sprayed from the core layer headbox to the forming wire to form the wet web of the core layer base paper. The top wire then forms the core layer base paper to improve uniformity. The bottom layer has a headbox concentration of 0.25%-0.35% and is sprayed from the bottom layer headbox to the forming wire to form the wet web of the bottom layer base paper. The bottom layer wet web and the core layer wet web are laminated at a dryness of about 10%-12% and pressed into one sheet. Then, the bottom layer wet web is laminated with the top layer wet web. The three layers of wet web are pressed into a composite wet web.

[0024] Furthermore, when the dryness of the composite wet paper web is 18%-22%, it enters the press section, where it is dehydrated by two stages of shoe press and smoothed by one stage of shoe press; the dryness is 50%-52% when it exits the third press.

[0025] Furthermore, in the pre-drying step, the paper surface dryness after drying is 93%-94%.

[0026] The composite wet paper web is pre-dried to a dryness of 93%-94% by a combination of 4 single-row drying cylinders and 8 double-row drying cylinders, and then sizing is applied. After sizing, the dryness is about 75%, and it is then post-dried to a dryness of 90%-93% by a combination of 1 single-row drying cylinder and 2 double-row drying cylinders.

[0027] Furthermore, in the pulping step, the beating concentration of the chemimechanical pulp is >5%. Using high-concentration viscous pulping to increase the beating concentration to over 5.0% reduces fiber cutting by the grinding disc, enhances fiber separation, and can effectively improve the strength of the fiber after molding.

[0028] Furthermore, the chemical hardwood pulp is made from imported Eucalyptus chemical hardwood pulp, with a pulp bulk thickness > 3.1.

[0029] It uses imported eucalyptus chemical hardwood pulp with a bulk of >3.1, which reduces the pressure of the core layer on the bottom layer during the paper creasing and folding process, and prevents the paper surface from cracking due to the pressure of the core layer fibers.

[0030] The second aspect of this application also provides a reverse UV paper, which is prepared using the preparation method described in the first aspect of this application.

[0031] Furthermore, the reverse UV paper has a surface roughness Ra≤1.0μm, a paper moisture content≦7%, and a tensile index of the top and bottom layers>110N·m / g.

[0032] The paper surface roughness Ra≤1.0μm meets the requirements for high-quality UV reverse printing; the paper moisture content is controlled to be below 7% to avoid fiber embrittlement during the rapid UV reverse drying process.

[0033] Furthermore, the reverse UV paper does not shed powder or bubble when tested ≥2 times with RI, making it suitable for high-intensity printing requirements.

[0034] Furthermore, the reverse UV paper has a longitudinal folding endurance of ≥35 times and a transverse folding endurance of ≥15 times; when an A4-sized paper sample is folded and subjected to a burst test, no bursting occurs on the front side, and the bursting length on the back side is ≤5mm. (According to ISO 5626 standard).

[0035] The above description of the invention is merely an overview of the technical solution of this application. In order to enable those skilled in the art to better understand the technical solution of this application and to implement it based on the textual description, and to make the above-mentioned objectives and other objectives, features and advantages of this application easier to understand, the following description is based on the specific embodiments of this application. Detailed Implementation

[0036] To explain in detail the technical content, structural features, objectives, and effects of the technical solution, the following detailed description is provided in conjunction with specific embodiments.

[0037] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description is provided in conjunction with the specific embodiments listed. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended only as examples, not as limiting the scope of protection of this application.

[0038] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0039] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0040] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" logical relationship.

[0041] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order relationship between these entities or operations.

[0042] Unless otherwise specified, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0043] As understood in the Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments in this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.

[0044] The first aspect of this application provides a method for preparing reverse UV paper, the method comprising the following steps:

[0045] Pulping, pulp preparation, dewatering and forming at the screen section, pressing at the press section, drying at the pre-drying section, applying sizing with a sizing machine, drying at the post-drying section, calendering with a calendering machine, winding, packaging and warehousing;

[0046] In the pulp preparation step, the surface and bottom layers of pulp are chemical softwood pulp and chemical hardwood pulp, and the core layer pulp is chemimechanical pulp, waste pulp, and multi-recycled fiber.

[0047] The sizing step of the sizing machine uses gelatinized starch with a solid content of 10-12%, a viscosity of 10-20 cps, a sizing temperature of 70℃-78℃, and a sizing rate of 3.5 g / m³. 2 -4.5g / m 2 .

[0048] Applying the adhesive at a temperature above 70℃ is necessary to prevent aging of the adhesive, ensure its fluidity, and improve its penetration performance.

[0049] Unlike existing technologies, the above-mentioned technical solution provides a method in the sizing step that increases the sizing temperature, reduces viscosity and solid content, so that a large amount of sizing agent adheres to the paper surface, thereby reducing capillary action on the paper surface. The short-chain starch in the sizing agent links with the fibers, giving the fibers hydrophobic groups, which increases the hydrophobicity of the paper surface and reduces the absorption of UV ink by the paper. The UV ink forms a floating layer on the paper surface and cures rapidly, achieving an embossed three-dimensional texture effect.

[0050] Furthermore, the method for preparing the gelatinized starch includes the following steps:

[0051] Add water to corn starch and / or tapioca starch and mix well to obtain a starch slurry with a solid content of 28-30%.

[0052] Add 200 ppm of amylase to the starch slurry to obtain the first slurry;

[0053] The first slurry is heated to 80-83℃ by steam to carry out an enzymatic reaction, thereby obtaining the second slurry;

[0054] When the enzymatic digestion reaction reaches a viscosity of 50-80 cps for the second slurry, the second slurry is heated to 130°C for a gelatinization reaction to obtain the third slurry.

[0055] The third slurry is cooled and diluted to a solid content of 10-12% to obtain the adhesive.

[0056] Furthermore, while keeping the total amount of adhesive applied constant, the viscosity of the adhesive can be reduced by increasing the flow rate at the top beam.

[0057] Furthermore, during the application of the sizing agent, the pressure of the sizing roller is 25-30kN.

[0058] Furthermore, in the pulp preparation step, the surface and bottom layers consist of 30% chemically synthesized softwood pulp and 70% chemically synthesized hardwood pulp. Increasing the proportion of long fibers in the surface and bottom layers can improve the tensile index of the surface and bottom layers.

[0059] Furthermore, in the pre-drying and post-drying steps, the temperature difference between each group of drying cylinders is controlled to be ≤10℃. The drying curve is optimized, and the temperature difference between each group of drying cylinders is controlled to not exceed 10 degrees, thereby controlling paper web shrinkage, reducing internal stress in the paper, lowering the moisture content of the finished paper, and preventing fiber embrittlement during the reverse UV rapid drying process.

[0060] By combining long fiber reinforcement and drying processes, the problem of stress concentration caused by rapid curing of UV inks during printing is solved, which leads to easy cracking when creased and folded.

[0061] Furthermore, in the dehydration and forming step of the mesh section, the mesh concentration of the surface layer is 0.25%-0.35%, the mesh concentration of the core layer is 1.1%-1.4%, and the mesh concentration of the bottom layer is 0.25%-0.35%.

[0062] After the pulp is adjusted in concentration and impurities and internal air are removed by the flow system, it is flowed from the headbox to the wire. The top layer has a headbox concentration of 0.25%-0.35% and is sprayed from the top layer headbox to the forming wire to form the wet web of the top layer base paper. The core layer has a headbox concentration of 1.1%-1.4% and is sprayed from the core layer headbox to the forming wire to form the wet web of the core layer base paper. The top wire then forms the core layer base paper to improve uniformity. The bottom layer has a headbox concentration of 0.25%-0.35% and is sprayed from the bottom layer headbox to the forming wire to form the wet web of the bottom layer base paper. The bottom layer wet web and the core layer wet web are laminated at a dryness of about 10%-12% and pressed into one sheet. Then, they are laminated with the top layer wet web to obtain a laminated wet web.

[0063] Furthermore, when the dryness of the composite wet paper web is 18%-22%, it enters the press section, where it is dehydrated by two stages of shoe press and smoothed by one stage of shoe press. When it exits the third press, the dryness is 50%-52%.

[0064] Furthermore, in the pre-drying step, the paper surface dryness after drying is 93%-94%.

[0065] The composite wet paper web is pre-dried to a dryness of 93%-94% by a combination of 4 single-row drying cylinders and 8 double-row drying cylinders, and then sizing is applied. After sizing, the dryness is about 75%, and it is then post-dried to a dryness of 90%-93% by a combination of 1 single-row drying cylinder and 2 double-row drying cylinders.

[0066] Furthermore, in the pulping step, the beating concentration of the chemimechanical pulp is >5%. Using high-concentration viscous pulping to increase the beating concentration to over 5.0% reduces fiber cutting by the grinding disc, enhances fiber separation, and can effectively improve the strength of the fiber after molding.

[0067] Furthermore, the chemical hardwood pulp is made from imported Eucalyptus chemical hardwood pulp, with a pulp bulk thickness > 3.1.

[0068] It uses imported eucalyptus chemical hardwood pulp with a bulk of >3.1, which reduces the pressure of the core layer on the bottom layer during the paper creasing and folding process, and prevents the paper surface from cracking due to the pressure of the core layer fibers.

[0069] The second aspect of this application also provides a reverse UV paper, which is prepared using the preparation method described in the first aspect of this application.

[0070] Furthermore, the reverse UV paper has a surface roughness Ra≤1.0μm, a paper moisture content≦7%, and a tensile index of the top and bottom layers>110N·m / g.

[0071] The paper surface roughness Ra≤1.0μm meets the requirements for high-quality UV reverse printing; the paper moisture content is controlled to be below 7% to avoid fiber embrittlement during the rapid UV reverse drying process.

[0072] Furthermore, the reverse UV paper does not shed powder or bubble when tested ≥2 times with RI, making it suitable for high-intensity printing requirements.

[0073] Furthermore, the reverse UV paper has a longitudinal folding endurance of ≥35 times and a transverse folding endurance of ≥15 times; when an A4-sized paper sample is folded and subjected to a burst test, no bursting occurs on the front side, and the bursting length on the back side is ≤5mm. (According to ISO 5626 standard).

[0074] In this embodiment, the web-on point is adjusted to approximately 0.8 cm in front of the forming plate, causing the pulp to be in a slight skipping state, enhancing turbulence. The angle of the ceramic plate in the hydrofoil vacuum box is adjusted to <5° to slow down the initial settling speed of the fibers. Process control and system cleaning are strengthened, with the pressure of the high-pressure water jet for felt cleaning maintained above 15 bar, ensuring the surface of the triple-press felt is always clean and smooth, and the surface of the drying cylinder is free of foreign matter, so that the paper web surface is clean during dehydration and drying. The ratio of calcium carbonate (75% solid content): water-retaining agent: thickener: rheology modifier is controlled at 100:1.25:1.25:0.6, adjusting the rheological properties of the coating so that the coefficient of the topcoat coating is maintained at 25±5 at a high shear rate of 500,000. Combined with real-time thickness data from the scanning frame, the horizontal pressure between the two rolls is adjusted using the adjustable-distance medium-high roll of the hard calender, with a sigma value ≤5, so that the horizontal thickness of the paper web is consistent and the longitudinal thickness is stable, ensuring uniform coating thickness. Soft calendering is used to finish the paper surface, further improving the gloss and smoothness of the finished paper.

[0075] In this embodiment, the method for preparing gelatinized starch includes the following steps:

[0076] Corn starch is mixed with water to obtain a starch slurry with a solid content of 28%. 200 ppm of amylase is added to the starch slurry to obtain a first slurry. The first slurry is heated to 80-83°C with 5 bar steam to carry out an enzymatic reaction, obtaining a second slurry. The enzymatic reaction is carried out for 20 minutes until the viscosity of the second slurry reaches 50-80 cps. Then, the second slurry is heated to 130°C to carry out a gelatinization reaction, obtaining a third slurry. The third slurry is cooled and diluted to 78°C with a solid content of 10-12%, obtaining the gelling agent.

[0077] Examples 1-4: A Reverse UV Paper

[0078] Pulping, pulp preparation, dewatering and forming at the screen section, pressing at the press section, drying at the pre-drying section, applying sizing with a sizing machine, drying at the post-drying section, calendering with a calendering machine, winding, packaging and warehousing;

[0079] Pulping steps: Short fiber pulp uses imported blue gum chemical hardwood pulp with a bulk >3.1; long fiber pulp uses chemical softwood pulp; the beating concentration of the chemimechanical pulp is >5%.

[0080] The pulping process involves the top and bottom layers consisting of 30% chemical softwood pulp and 70% chemical hardwood pulp, while the core layer consists of 80-90% chemimechanical pulp, 10-20% waste pulp, and 3-5% recycled fiber.

[0081] After the pulp is adjusted in concentration and impurities and internal air are removed by the flow system, it is flowed from the headbox to the wire. The top layer has a headbox concentration of 0.25%-0.35% and is sprayed from the top layer headbox to the forming wire to form the wet web of the top layer base paper. The core layer has a headbox concentration of 1.1%-1.4% and is sprayed from the core layer headbox to the forming wire to form the wet web of the core layer base paper. The top wire then forms the core layer base paper to improve uniformity. The bottom layer has a headbox concentration of 0.25%-0.35% and is sprayed from the bottom layer headbox to the forming wire to form the wet web of the bottom layer base paper. The bottom layer wet web and the core layer wet web are then laminated at a dryness of approximately 10%-12% and pressed together. One sheet is then laminated with the surface wet paper web, and the three layers of wet paper webs are pressed into a composite wet paper web. When the composite wet paper web has a dewatering dryness of 18%-22%, it enters the press section, where it is dewatered by two shoe presses and leveled by one shoe press. The dryness of the paper web is 50%-52% when it exits the third press. The composite paper web is then pre-dried to a dryness of 93%-94% by a pre-drying system consisting of 4 single-row drying cylinders and 8 double-row drying cylinders. The sizing is then applied. The sizing agent used is gelatinized starch with a solid content of 10-12%, a viscosity of 10-20 cps, a sizing temperature of 70℃-78℃, and a sizing amount of 3.5 g / m³. 2 -4.5g / m 2 The pressure of the sizing roller is 25-30kN; the dryness after sizing is about 75%, and it is dried to 90%-93% after passing through a set of single-row drying cylinders and two sets of double-row drying cylinders; the temperature difference between each set of drying cylinders is controlled to be ≤10℃ during the drying steps of the pre-drying section and the post-drying section; after the paper is pressed to uniform thickness by hard calendering, it is pre-coated, intermediate coated, back coated and top coated, and then the paper is finished by soft calendering; it is then wound to complete the papermaking process.

[0082] Performance testing:

[0083] 1. The anti-burst properties of the reverse UV paper prepared in Examples 1-4 were tested according to ISO 5626 standard, and the results are shown in Table 1:

[0084] Table 1. Detection results of reverse UV paper in Examples 1-4

[0085]

[0086] The paper should withstand ≥35 folds longitudinally and ≥15 folds transversely. A folding test was conducted on an A4-sized paper sample; no cracking occurred on the front side, and the crack length on the back side was ≤5mm. It should not easily crack during the creasing and folding box manufacturing process.

[0087] 2. Paper strength test:

[0088] Using an IGT instrument for RI testing, the reverse UV paper prepared in Examples 1-4 showed no powder shedding or bubbling when the RI test was performed ≥2 times, making it suitable for high-intensity printing requirements.

[0089] 3. Surface roughness test

[0090] The reverse UV paper prepared in Examples 1-4 has a surface roughness of ≤1.0μm, making it suitable for high-precision printing.

[0091] 4. Practicality Test:

[0092] The reverse UV paper prepared in Examples 1-4 was subjected to reverse UV printing. After printing, the absorption of UV ink by the paper was reduced, and the UV ink formed a floating layer on the paper surface and cured quickly to achieve an embossed three-dimensional texture effect.

[0093] Finally, it should be noted that although the above embodiments have been described in the description of this application, this should not limit the scope of patent protection of this application. Any technical solutions that are based on the essential concept of this application, utilize the content described in this application's description to make equivalent structural or procedural substitutions or modifications, or directly or indirectly implement the technical solutions of the above embodiments in other related technical fields, are all included within the scope of patent protection of this application.

Claims

1. A method for preparing a reverse UV paper, characterized by, The preparation method comprises the following steps: pulping, pulp mixing, wire section dewatering forming, press section pressing, pre-drying section drying, sizing machine sizing, post-drying section drying, calendering, winding, packaging and warehousing; The pulp mixing step is characterized in that the surface layer and the bottom layer pulp are chemical coniferous pulp and chemical broadleaf pulp, and the core layer pulp is chemi-mechanical pulp, broke pulp and multi-disc recycled fiber. The sizing machine applies sizing step, the sizing material is paste starch with solid content of 10-12%, the sizing material viscosity is 10-20cps, the sizing temperature is 70-78℃, and the sizing amount is 3.5g / m 2 -4.5g / m 2 .

2. A method of preparing a reverse UV paper according to claim 1, characterized in that, The preparation method of the gelatinized starch comprises the following steps: corn starch or / and cassava starch is added with water and uniformly mixed to obtain a starch slurry with a solid content of 28-30%; 200ppm of amylase is added into the starch slurry to obtain a first slurry; The first slurry is heated to 80-83℃ by steam to perform enzyme cutting reaction to obtain a second slurry; When the viscosity of the second slurry reaches 50-80cps, the second slurry is heated to 130℃ to perform gelatinization reaction to obtain a third slurry; The third slurry is cooled and diluted to a solid content of 10-12% to obtain the sizing material.

3. A method of preparing a reverse UV paper according to claim 1, characterized in that, The pulp mixing step is characterized in that the surface layer and the bottom layer pulp are 30% chemical coniferous pulp and 70% chemical broadleaf pulp.

4. The method for preparing reverse UV paper according to claim 1, characterized in that, The pre-drying section drying and post-drying section drying steps are characterized in that the temperature difference between each group of drying cylinders is controlled to be ≦10℃.

5. The method for preparing reverse UV paper according to claim 1, characterized in that, The wire section dewatering forming step is characterized in that the wire concentration of the surface layer is 0.25-0.35%, the wire concentration of the core layer is 1.1-1.4%, and the wire concentration of the bottom layer is 0.25-0.35%.

6. The method for preparing reverse UV paper according to claim 1, characterized in that, The pre-drying section drying step is characterized in that the paper dryness after drying is 93-94%.

7. The method for preparing reverse UV paper according to claim 1, characterized in that, The pulping step is characterized in that the beating consistency of the chemi-mechanical pulp is >5%.

8. The method for preparing reverse UV paper according to claim 1, characterized in that, The chemical broadleaf pulp is imported blue eucalyptus chemical broadleaf pulp, and the bulk of the pulp is >3.

1.

9. A reverse UV paper characterized in that, The reverse UV paper is prepared by the preparation method of any one of claims 1-8.

10. The reverse UV paper according to claim 9, characterized in that, The roughness Ra of the surface of the reverse UV paper is ≤1.0μm, the moisture content of the paper is ≦7%, and the tensile index of the surface and the bottom layer is >110N·m / g.

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