Two-side offset paper and preparation method thereof

Abstract

The invention provides two-side offset paper and a preparation method thereof.The preparation method comprises the steps that raw paper is manufactured, the raw paper comprises at least three fiber layers, fiber paper pulp of a core fiber layer comprises 20%-80% of BCTMP, 0%-10% of NBKP and 20%-60% of LBKP, the whiteness of BCTMP is larger than or equal to 75%, and the bulk of BCTMP is larger than or equal to 2.5; respectively carrying out surface sizing on two sides of the raw paper; and carrying out calendaring treatment on the body paper subjected to surface sizing. According to the preparation method of the two-side offset paper provided by the embodiment of the invention, the stiffness of the two-side offset paper made by adopting the multi-layer net is superior to that of conventional two-side offset paper with the same bulk under the condition that the ash content is equivalent; according to the present invention, the two-side offset paper prepared by using the multi-layer net is superior to the single-layer structure two-side offset paper of the conventional scheme in the aspects of smoothness, opaqueness, PPS and two-side difference, and in addition, the two-side difference of the two-side offset paper prepared by using the multi-layer net is more flexible to control in the preparation method of the two-side offset paper provided by the embodiment of the present invention.

Description

Technical Field

[0001] This application relates to the technical field of papermaking, specifically to a double-sided offset paper and its preparation method. Background Technology

[0002] Double-sided offset paper, also known as "double-sided offset printing paper," is a type of cultural and commercial printing paper made from plant fibers through multiple processes including pulping, sizing, papermaking, and calendering, with both sides treated with sizing. Its core characteristics are high smoothness on both sides and uniform sizing, meeting the requirements of offset printing (lithographic printing) regarding ink absorption and water resistance, thus avoiding problems such as bleed-through and ink bleeding during printing. It is one of the most widely used basic paper types in the printing industry.

[0003] Currently, most offset paper on the market is single-layered. With the trend towards lightweighting, the limitations of single-layered structures in terms of bulk are becoming increasingly apparent, and with the reduction in grammage, there is a risk of bleed-through. Summary of the Invention

[0004] The first aspect of this application provides a method for preparing double-sided coated paper, the method comprising: The paper is used for making base paper, which includes at least three fiber layers, wherein the core fiber layer contains BCTMP with a ratio of 20-80%, NBKP with a ratio of 0-10%, and LBKP with a ratio of 20-60%, and the BCTMP has a whiteness of ≥75% and a bulk of ≥2.5. Apply sizing to both sides of the base paper; Calendering is performed on the base paper after surface sizing.

[0005] In some optional embodiments, the fiber pulp of the base paper other than the core layer includes 10-30% NBKP and 70-90% LBKP, wherein the freeness of NBKP is 300-500ml, the freeness of LBKP is 350-450ml, and the whiteness is ≥88%.

[0006] In some optional embodiments, the filler content in the pulp of the core fiber layer is 0-300 kg per ton of oven-dry fiber pulp, and the filler content in the pulp of the other fiber layers besides the core fiber layer is 50-100 kg per ton of oven-dry fiber pulp.

[0007] In some optional embodiments, an in-pulp sizing agent is added to the pulp of each fiber layer of the base paper.

[0008] In some alternative embodiments, during the papermaking process, starch is sprayed between adjacent fiber layers to increase strength.

[0009] In some optional embodiments, one or more of fluorescent whitening agents and dyes are added to the pulp of each fiber layer of the base paper. The amount of fluorescent whitening agent is 0-20000ppm, and the amount of dye is 50-500ppm. The type of dye is pigment dye.

[0010] In some optional embodiments, in the step of applying surface sizing to both sides of the base paper, the sizing amount on the front and back sides is 2.5-5.5 g / m², respectively. 2 The amount of surface sizing agent added to the sizing solution is 4-10% of the oven-dry weight of the starch.

[0011] In some optional embodiments, the surface sizing agent is of the type SAE or a mixture of SAE and AKD.

[0012] In some optional embodiments, the step of calendering the base paper after surface sizing is carried out by a combination of hard calendering and soft calendering. The hard calendering is controlled with a pressing force of 30-70 N / mm and a temperature of 120℃-180℃, while the soft calendering is controlled with a pressing force of 10-40 N / mm on the front side and 40-100 N / mm on the back side, at a temperature of 100℃-160℃.

[0013] Secondly, embodiments of this application provide a double-sided coated paper, which is prepared using the preparation method described in the above embodiments.

[0014] The method for preparing double-sided coated paper provided in this application embodiment uses a multi-layer wire mesh fabrication method. Under the condition of similar ash content, the double-sided coated paper has better stiffness than conventional double-sided coated paper of the same bulk thickness. In terms of smoothness, opacity, PPS, and two-sided difference, it is better than the conventional single-layer structure double-sided coated paper. In addition, the double-sided coated paper preparation method in this application embodiment uses a multi-layer wire mesh fabrication method, which has greater flexibility in controlling the two-sided difference. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic flowchart of an embodiment of the method for preparing double-sided offset paper according to this application; Figure 2 This is a schematic diagram of the laminated structure of one embodiment of the original paper of this application; Figure 3 This is a schematic diagram of the laminated structure of another embodiment of the original paper of this application; Figure 4This is a schematic diagram of the stacked structure of another embodiment of the original paper of this application; Figure 5 This is a schematic diagram of the stacked structure of another embodiment of the original paper of this application; Figure 6 This is a schematic diagram of the laminated structure of an embodiment of the double-sided adhesive paper of this application. Detailed Implementation

[0017] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the application. Similarly, the following embodiments are only some, not all, embodiments of the present application, and all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present application.

[0018] The terms "first," "second," and "third" used in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationships and movement of components in a specific posture (as shown in the figures). If the specific posture changes, the directional indication will also change accordingly. The terms "comprising" and "having," and any variations thereof, in the embodiments of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or components inherent to these processes, methods, products, or devices.

[0019] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0020] First, this application provides a method for preparing double-sided adhesive paper. Please refer to [link to relevant documentation]. Figure 1 , Figure 1 This is a schematic flowchart of an embodiment of the preparation method of the double-sided offset paper of this application; the preparation method includes, but is not limited to, the following steps.

[0021] Step S100: Making the original paper.

[0022] In this step, the base paper comprises at least three fiber layers. Please refer to [link / reference needed]. Figures 2 to 5 , Figure 2 This is a schematic diagram of the laminated structure of one embodiment of the original paper of this application. Figure 3 This is a schematic diagram of the laminated structure of another embodiment of the original paper of this application. Figure 4 This is a schematic diagram of the laminated structure of another embodiment of the original paper of this application. Figure 5 This is a schematic diagram of the stacked structure of another embodiment of the original paper of this application.

[0023] Among them, the three-layer base paper (such as Figure 2 (As shown) can be a four-layer base paper consisting of a surface fiber layer 110, a core fiber layer 120, and a bottom fiber layer stacked sequentially. Figure 3 (As shown) can be a combination of a surface fiber layer 110, a core fiber layer 120, a backing fiber layer 140, and a bottom fiber layer 130 stacked sequentially, or (as shown) Figure 4 (As shown) includes a face fiber layer 110, a face liner fiber layer 150, a core fiber layer 120, and a bottom fiber layer 130 stacked sequentially. The five-layer base paper (such as...) Figure 5 (As shown) can include a surface fiber layer 110, a surface lining fiber layer 150, a core fiber layer 120, a bottom lining fiber layer 140, and a bottom fiber layer 130 arranged in sequence.

[0024] Optionally, the basis weight of the double-sided coated paper prepared in the embodiments of this application is 150 g / m². 2 -350g / m 2 Among them, the basis weight of the face fiber layer 110, face lining fiber layer 150, bottom lining fiber layer 140 and bottom fiber layer 130 is 13-30 gsm, and the rest is the basis weight of the core fiber layer 120 (paper basis weight - sizing amount - other fiber layers).

[0025] The core fiber layer 120 consists of fiber pulp with a BCTMP ratio of 20-80%, an NBKP ratio of 0-10%, and an LBKP ratio of 20-60%. The BCTMP has a brightness of ≥75% and a bulk of ≥2.5 (the final paper bulk requirement is 1.10-1.40cm). 3 / g); Looseness requirement ≥2.8 (finished paper bulkness requirement 1.50-1.90cm) 3 / g). The thickness of the double-sided coated paper prepared by the method in this embodiment ranges from 1.10 to 1.90 cm. 3 / g. The proportion of the core fiber layer 120 is adjusted appropriately within the aforementioned range according to the required bulk density.

[0026] Optionally, the fiber pulp of the face fiber layer 110, face liner fiber layer 150, under liner fiber layer 140 and under fiber layer 130 includes 10-30% NBKP and 70-90% LBKP, wherein the freeness of NBKP is 300-500ml, the freeness of LBKP is 350-450ml, and the whiteness is ≥88%.

[0027] Optionally, in some other embodiments, starch is sprayed between adjacent fiber layers to increase strength. The starch can be one or a mixture of tapioca starch, corn starch, and wheat starch; the strength of each fiber layer can also be ensured by adding cationic starch, dry strength agents, or other reinforcing agents.

[0028] In addition, fillers can be added to the pulp of each fiber layer. Specifically, the filler content in the pulp of the core fiber layer 120 is 0-300 kg per ton of oven-dry pulp. The filler content in the pulp of other fiber layers (including the face fiber layer 110, face liner fiber layer 150, bottom liner fiber layer 140, and bottom fiber layer 130) is 50-100 kg per ton of oven-dry pulp. The filler's function is to improve PPS (polystyrene) and smoothness on both sides, improve ink absorption and uniformity, resulting in good printing effects. Adding too much filler will affect strength. The filler ratio is controlled according to the paper's bulk, strength, and dewatering requirements. Adding filler to the core fiber layer 120 is beneficial for cost reduction, improving dewatering, uniformity, and smoothness, especially at high basis weights, while also increasing opacity. The filler type can be GCC, PCC, kaolin, etc. Specific details of these fillers are beyond the understanding of those skilled in the art and will not be elaborated here.

[0029] Depending on the whiteness and color requirements of the finished paper, optical brighteners (OBA) and dyes can be added to each fiber layer. The dosage of optical brighteners is 0-20000 ppm, and the dosage of dyes is 50-500 ppm. The dyes are added after the pulp pump and before the pressure screen to facilitate rapid color adjustment. The concentration is 2%-10%. The dyes must be pigment-based. This ensures uniform dyeing of the produced paper without visible dyed fibers, and also results in less pollution to the system, higher white water purity, and minimal impact on the color of other paper types produced. The dye color can be one or more of blue, purple, red, black, yellow, etc., depending on the paper color requirements; no specific limitation is made here.

[0030] In addition, sizing agents are added to each fiber layer to ensure the COBB values ​​on both the front and back sides. Sizing methods can include ASA (alkenyl succinic anhydride) sizing, AKD (alkyl ketene dimer) sizing, rosin sizing, etc.

[0031] Please continue reading. Figure 1The preparation method of double-sided coated paper in this embodiment of the application further includes step S200, which involves applying adhesive to both sides of the base paper.

[0032] Please see Figure 6 , Figure 6 This is a schematic diagram of the laminated structure of an embodiment of the double-sided adhesive paper of this application. In this embodiment, the base paper includes a five-layer structure as an example for explanation. In the figure, reference numeral 210 represents the front adhesive layer and reference numeral 220 represents the back adhesive layer.

[0033] In step S200, the amount of adhesive applied to both the front and back sides and the amount of adhesive solution can be the same in this embodiment, wherein the amount of adhesive applied to the front and back sides is 2.5-5.5 g / m². 2 The amount of surface sizing agent added to the sizing solution is 4-10% of the oven-dry weight of the starch. The type of surface sizing agent is SAE (styrene-acrylate copolymer) or a mixture of SAE and AKD (alkyl ketene dimer). The COBB content of the core fiber layer 120 is 20-40 g / m². 2 (60s), COBB values ​​on both sides are 20-40g / m². 2 (60s); control the ink absorption of the paper surface to avoid printing smudging.

[0034] Please continue reading. Figure 1 The preparation method of double-sided coated paper in this embodiment further includes step S300, which involves calendering the base paper after surface sizing.

[0035] In this step, a combination of hard calendering and soft calendering is used. Hard calendering involves controlling the linear pressure at 30-70 N / mm and the temperature at 120℃-180℃, ensuring uniform thickness and improving paper surface smoothness. Soft calendering involves applying 10-40 N / mm to the front and 40-100 N / mm to the back, at a temperature of 100℃-160℃. Soft calendering improves surface micro-smoothness, and the difference in linear pressure between the front and back surfaces reduces surface differences.

[0036] Among them, the pulp-to-mesh speed ratio (J / W) of the bottom layer needs to be controlled between 1.000 and 1.040, which can improve the water ripples caused by dewatering on the back side.

[0037] The method for preparing double-sided coated paper provided in this application embodiment uses a multi-layer wire mesh fabrication method. Under the condition of similar ash content, the double-sided coated paper has better stiffness than conventional double-sided coated paper of the same bulk thickness. In terms of smoothness, opacity, PPS, and two-sided difference, it is better than the conventional single-layer structure double-sided coated paper. In addition, the double-sided coated paper preparation method in this application embodiment uses a multi-layer wire mesh fabrication method, which has greater flexibility in controlling the two-sided difference.

[0038] The parameters of the specific embodiments are shown in the table below: In the following embodiments, the double-sided offset paper is produced on a 5-layer long wire paper machine with a width of 8.1 meters and a machine speed of 850-950m / min.

[0039]

[0040] The following table compares the parameters of the three embodiments obtained using the parameters in the aforementioned table with those of conventional double-sided offset paper.

[0041]

[0042] The above comparison shows that the double-sided coated paper prepared using the method described in this application has better stiffness than conventional double-sided coated paper of the same bulk, provided the ash content is similar. This invention uses a long-wire paper machine to produce multi-layered double-sided coated paper; by adjusting the process, the bulk can be adjusted to 1.10-1.90 cm. 3 The opacity is adjustable within a certain range, with a smoothness of ≥20s and PPS ≤5.0um. Furthermore, the difference in PPS and smoothness between the two sides can be controlled within 10%. In terms of smoothness, opacity, PPS, and difference between the two sides, it is superior to the conventional single-layer double-sided adhesive paper.

[0043] The above description is only a part of the embodiments of this application and does not limit the scope of protection of this application. Any equivalent device or equivalent process transformation made based on the content of this application specification and drawings, or direct or indirect application in other related technical fields, are similarly included in the patent protection scope of this application.

Claims

1. A method for preparing double-sided offset paper, characterized in that, The preparation method includes: The paper is used for making base paper, which includes at least three fiber layers, wherein the core fiber layer contains BCTMP with a ratio of 20-80%, NBKP with a ratio of 0-10%, and LBKP with a ratio of 20-60%, and the BCTMP has a whiteness of ≥75% and a bulk of ≥2.

5. Apply sizing to both sides of the base paper; Calendering is performed on the base paper after surface sizing.

2. The preparation method according to claim 1, characterized in that, The fiber pulp of the base paper, excluding the core layer, includes 10-30% NBKP and 70-90% LBKP, wherein the freeness of NBKP is 300-500ml, the freeness of LBKP is 350-450ml, and the whiteness is ≥88%.

3. The preparation method according to claim 2, characterized in that, The filler content in the pulp of the core fiber layer is 0-300 kg per ton of oven-dry pulp, and the filler content in the pulp of other fiber layers besides the core fiber layer is 50-100 kg per ton of oven-dry pulp.

4. The preparation method according to claim 3, characterized in that, The pulp of each fiber layer of the base paper contains an in-pulp sizing agent.

5. The preparation method according to claim 4, characterized in that, In the papermaking process, starch is sprayed between adjacent fiber layers to increase strength.

6. The preparation method according to claim 4, characterized in that, The pulp of each fiber layer of the base paper contains one or more of fluorescent whitening agents and dyes. The amount of fluorescent whitening agent is 0-20000ppm, and the amount of dye is 50-500ppm. The type of dye is pigment dye.

7. The preparation method according to claim 1, characterized in that, In the step of applying sizing to both sides of the base paper, the sizing amount for the front and back sides is 2.5-5.5 g / m², respectively. 2 The amount of surface sizing agent added to the sizing solution is 4-10% of the oven-dry weight of the starch.

8. The preparation method according to claim 7, characterized in that, The surface sizing agent is of the type SAE or a mixture of SAE and AKD.

9. The preparation method according to claim 1, characterized in that, In the step of calendering the base paper after surface sizing, a combination of hard calendering and soft calendering is used. The hard calendering line pressure is controlled at 30-70 N / mm and the temperature is 120℃-180℃. The soft calendering line pressure is 10-40 N / mm on the front side and 40-100 N / mm on the back side, and the temperature is 100℃-160℃.

10. A type of offset paper, characterized in that, The double-sided coated paper is prepared by the preparation method of any one of claims 1-9.

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