Process for the preparation of dyed base paper and dyed base paper

Abstract

The application discloses a preparation method of dyed base paper and the dyed base paper, and the preparation method comprises the following steps: obtaining mixed pulp; wherein the mixed pulp comprises first wood pulp and second wood pulp, the weight part of the first wood pulp is 17-20, the freeness of the first wood pulp is 290-310 mL, and the freeness of the second wood pulp is 210-230 mL; wherein the first wood pulp is bleached long fiber wood pulp, and the second wood pulp is bleached mechanical pulp; papermaking is performed on the mixed pulp to obtain base paper; sizing is performed on the base paper; and the sized base paper is dyed to obtain dyed base paper. The application can make the fibers of different pulp better interweave, the fiber distribution is more uniform, thereby improving the evenness of the base paper obtained through papermaking, and then improving the dyeing uniformity of the base paper.

Description

Technical Field

[0001] This application relates to the papermaking field, and in particular to a method for preparing dyed base paper and dyed base paper. Background Technology

[0002] With the rapid development of the household paper industry and the increasing demand from consumers for high-end household paper, ordinary household paper can no longer meet consumer needs. As a result, various functional household paper products have emerged on the market, one of which is dyed base paper (paper with color, also known as colored paper), which can be used in printing, arts and crafts, product packaging and other fields.

[0003] Dyed base paper is typically prepared using a wet process. Before papermaking, a large amount of water needs to be added to the wood pulp to create a uniform fiber suspension. During the papermaking process, a significant amount of water needs to be removed. If organic pigments or dyes are added to the pulp, some of these pigments are often lost during dehydration, leading to pigment waste and environmental pollution. In existing technologies, dyeing the sized base paper using a dye padding solution prepared with dyeing agents can reduce pigment waste and pollution. The uniformity of padding dyeing is related to the uniformity of the resulting paper.

[0004] However, base paper is generally made using mixed pulp, and different fibers have different affinity for dyes. If the different pulp fibers are not mixed evenly during the papermaking process, the uniformity of the paper produced will be poor, and uneven dyeing will occur during the dyeing process. Summary of the Invention

[0005] The main technical problem addressed by this application is to provide a method for preparing dyeing base paper and the dyeing base paper itself, which can solve the problem of uneven dyeing existing in current dyeing methods.

[0006] To solve the above-mentioned technical problems, the first technical solution adopted in this application is to provide a method for preparing dyed base paper, comprising: obtaining a mixed pulp; wherein the mixed pulp includes a first wood pulp and a second wood pulp, the first wood pulp having a weight part of 17-20 and a freeness of 290-310 mL, and the second wood pulp having a freeness of 210-230 mL; wherein the first wood pulp is bleached long-fiber wood pulp, and the second wood pulp is bleached mechanical pulp; forming the mixed pulp to obtain base paper; sizing the base paper; and dyeing the sized base paper to obtain dyed base paper.

[0007] The mixed pulp also includes a third wood pulp. The steps for obtaining the mixed pulp include: preparing the following raw materials in preset weight parts: 17-20 parts of first wood pulp; 3-9 parts of second wood pulp; and 71-80 parts of third wood pulp; refining the first wood pulp, second wood pulp, and third wood pulp respectively, so that the freeness of the first wood pulp is 290-310 mL, the freeness of the second wood pulp is 210-230 mL, and the freeness of the third wood pulp is 300-320 mL; and mixing the refined first wood pulp, second wood pulp, and third wood pulp evenly to obtain the mixed pulp.

[0008] The third type of wood pulp is bleached short fiber wood pulp.

[0009] The step of sizing the base paper includes: sizing the base paper with a surface sizing agent; wherein the surface sizing agent includes water, rosin sizing agent and styrene-acrylic emulsion sizing agent.

[0010] The step of sizing the base paper using a surface sizing agent includes: preparing rosin sizing agent, styrene-acrylic emulsion sizing agent, and water; adding the rosin sizing agent and styrene-acrylic emulsion sizing agent into the water, stirring evenly to obtain the surface sizing agent; wherein the total mass fraction of the rosin sizing agent and the styrene-acrylic emulsion sizing agent is 4-6%; and sizing the base paper using the surface sizing agent.

[0011] The steps of preparing rosin sizing agent, styrene-acrylic emulsion sizing agent and water include: preparing rosin sizing agent, styrene-acrylic emulsion sizing agent and water according to a preset weight ratio; wherein the weight ratio of rosin sizing agent and styrene-acrylic emulsion sizing agent is equal.

[0012] Among them, rosin sizing agents include cationic dispersed rosin gum.

[0013] The step of forming the mixed pulp to obtain base paper includes: adding filler, starch and retention aid to the mixed pulp; and forming the mixed pulp with added filler, starch and retention aid to obtain base paper.

[0014] The step of dyeing the sized base paper to obtain dyed base paper includes: coating the sized base paper with a dye padding solution to obtain dyed base paper.

[0015] To solve the above-mentioned technical problems, the second technical solution adopted in this application is to provide a dyeing base paper, which is prepared by the above-mentioned method for preparing dyeing base paper.

[0016] The beneficial effects of this application are as follows: Unlike existing technologies, this application provides a method for preparing dyed base paper. By limiting the weight of the first wood pulp in the mixed pulp to 17-20 parts, the content of long fibers in the mixed pulp can be reduced, avoiding uneven fiber distribution caused by excessive long fiber content. At the same time, by limiting the freeness of the first wood pulp to 290-310 mL and the freeness of the second wood pulp to 210-230 mL, the fibrillation of long fibers and the softening of lignin in the bleached mechanical pulp can be enhanced, allowing the fibers of different pulps to interweave better and the fiber distribution to be more uniform, thereby improving the uniformity of the base paper obtained by papermaking, and consequently improving the dyeing uniformity of the base paper. Attached Figure Description

[0017] 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.

[0018] Figure 1 This is a flowchart illustrating the first embodiment of the method for preparing the dyed base paper of this application;

[0019] Figure 2 This is a flowchart illustrating the second embodiment of the method for preparing the dyed base paper of this application;

[0020] Figure 3 yes Figure 2 A flowchart illustrating a specific implementation method in S23;

[0021] Figure 4a and Figure 4b These are SEM images of the dyed base paper in Example 5 and Control Group 3 of this application, respectively. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the application. The singular forms “a,” “said,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless otherwise clearly indicated above. “Multiple” generally includes at least two, but does not exclude the inclusion of at least one.

[0024] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0025] It should be understood that the terms "comprising," "including," or any other variations used herein are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0026] In existing technologies, dyeing the sized and formed base paper using a dye padding solution made from dyeing agents can reduce dye waste and pollution. The uniformity of padding dyeing is related to the uniformity of the resulting paper. However, base paper is generally made using mixed pulp, and different fibers have different affinities for dyeing agents. If the different pulp fibers are not mixed evenly during the papermaking process, the uniformity of the resulting paper will be poor, leading to uneven dyeing during the dyeing process.

[0027] Based on the above, this application provides a method for preparing dyeing base paper and dyeing base paper, which can solve the problem of uneven dyeing in existing dyeing methods.

[0028] Please see Figure 1 , Figure 1 This is a schematic flowchart of the first embodiment of the method for preparing the dyed base paper of this application. Figure 1 As shown, in this embodiment, the preparation method includes:

[0029] S11: Obtain a mixed pulp; wherein the mixed pulp includes a first wood pulp and a second wood pulp, the first wood pulp has a weight of 17-20 parts, the freeness of the first wood pulp is 290-310 mL, and the freeness of the second wood pulp is 210-230 mL; wherein the first wood pulp is bleached long-fiber wood pulp, and the second wood pulp is bleached mechanical pulp.

[0030] In this embodiment, the bleached long-fiber wood pulp is bleached sulfate softwood pulp (NBKP), and the bleached mechanical pulp is alkaline peroxide mechanical pulp (APMP).

[0031] Among them, the fiber length in bleached long-fiber wood pulp that has not undergone pulping treatment can generally reach 2-3.5 mm, and the freeness can be maintained between 600-700 ml.

[0032] Among them, alkaline peroxide mechanical pulp is a high-yield wood pulp with high bulk.

[0033] In this embodiment, the mixed pulp also includes a third wood pulp, which is bleached short-fiber wood pulp. Specifically, the bleached short-fiber wood pulp is bleached sulfate hardwood pulp (LBKP).

[0034] Bleached short-fiber wood pulp has the characteristics of moderate fiber fineness and low ash content. The short fibers fill the gaps in the fiber layer, such as filling the pores formed by long fibers in bleached long-fiber wood pulp, which can increase the smoothness of the fiber layer. At the same time, the addition of short fibers can prevent the base paper from being too tough, which is beneficial for subsequent processing operations such as die-cutting, cutting and folding, and reduces the wear of paper cutter blades.

[0035] In this embodiment, the total weight of the various pulps in the mixed pulp is 100 parts.

[0036] In this embodiment, the step of obtaining the mixed pulp includes: preparing the following raw materials in preset weight parts: 17-20 parts of first wood pulp; 3-9 parts of second wood pulp; and 71-80 parts of third wood pulp. The first, second, and third wood pulps are then refined to achieve a freeness of 290-310 mL for the first wood pulp, 210-230 mL for the second wood pulp, and 300-320 mL for the third wood pulp. The refined first, second, and third wood pulps are then mixed thoroughly to obtain the mixed pulp.

[0037] In a specific implementation scenario, the first wood pulp consists of 17 parts, the second wood pulp consists of 3 parts, and the third wood pulp consists of 80 parts. The freeness of the first wood pulp is 290 mL, the freeness of the second wood pulp is 210 mL, and the freeness of the third wood pulp is 320 mL.

[0038] In another specific implementation scenario, the first wood pulp consists of 18 parts, the second wood pulp consists of 5 parts, and the third wood pulp consists of 77 parts. The freeness of the first wood pulp is 300 mL, the freeness of the second wood pulp is 220 mL, and the freeness of the third wood pulp is 310 mL.

[0039] In another specific implementation scenario, the first wood pulp consists of 20 parts, the second wood pulp consists of 9 parts, and the third wood pulp consists of 71 parts. The freeness of the first wood pulp is 310 mL, the freeness of the second wood pulp is 230 mL, and the freeness of the third wood pulp is 310 mL. This application does not limit this.

[0040] In other embodiments, depending on the different paper requirements, the type of mixed pulp can be wood pulp, straw pulp, hemp pulp, reed pulp, sugarcane pulp, bamboo pulp, rag pulp, and other papermaking raw materials commonly used in the art. This application does not limit this type of pulp.

[0041] In other embodiments, the mixed pulp may be made of other materials, the proportions of the materials may be other ratios, or the mixed pulp may be obtained by other means, which is not limited in this application.

[0042] In existing technologies, the weight percentage of bleached sulfate softwood pulp in the base paper is typically not less than 22 parts, and the freeness is usually 380–400 mL. However, within this freeness range, long fibers still have a relatively large length, and their distribution easily forms large clumps, leading to uneven fiber distribution.

[0043] Unlike existing technologies, this embodiment limits the weight of the first wood pulp to 17-20 parts, thereby reducing the content of bleached long-fiber wood pulp in the mixed pulp and avoiding uneven fiber distribution caused by excessive long fiber content. Furthermore, by controlling the freeness of the bleached long-fiber wood pulp between 290-310 mL, it promotes the fibrillation of long fibers, reduces the fiber length of the bleached long-fiber wood pulp, and forms more hydrogen bonds between fibers, promoting interweaving. Since the bleached long-fiber wood pulp still retains a certain length after refining, it can interweave not only with the other fibers in the pulp but also through its own length.

[0044] In existing technologies, the freeness of alkaline peroxide mechanical pulp after refining is typically 250–380 mL. However, due to the high lignin content in mechanical pulp, a higher freeness makes it difficult for fibers to swell, hydrate, and fiberize during pulping, and the fibers are relatively coarse and stiff, making it difficult for them to adhere tightly together during paper drying.

[0045] Unlike existing technologies, this embodiment controls the freeness of alkaline peroxide mechanical pulp to 210-230 mL, which can better soften the lignin in the alkaline peroxide mechanical pulp, making it easier for it to interweave with the long and short fibers in the mixed pulp.

[0046] Understandably, by adjusting the ratio of bleached long-fiber wood pulp in the mixed pulp and the degree of freeness of bleached long-fiber wood pulp and alkaline peroxide mechanical pulp, the interweaving properties between different fibers can be improved, thereby enhancing the uniformity of the base paper obtained in subsequent papermaking.

[0047] S12: The mixed pulp is processed to obtain the base paper.

[0048] S13: Apply sizing to the base paper.

[0049] In this embodiment, a surface sizing agent is applied to both sides of the base paper, and after drying, the paper is removed to obtain the sizing base paper.

[0050] The purpose of sizing is to give the paper a certain ability to resist liquid penetration, which can improve the paper's resistance to water, oil, and printing ink, while also improving the paper's mechanical properties and surface strength.

[0051] S14: Dye the sized base paper to obtain dyed base paper.

[0052] Understandably, because the different pulp fibers in the mixed pulp are mixed more evenly, the uniformity of the base paper produced is also higher. This allows the dye to be distributed as evenly as possible on the base paper during the dyeing process, thereby improving the uniformity of dyeing and thus meeting the quality requirements of the dyed base paper.

[0053] Unlike existing technologies, this embodiment limits the weight of the first wood pulp in the mixed pulp to 17-20 parts, thereby reducing the content of long fibers in the mixed pulp and avoiding uneven fiber distribution caused by excessive long fiber content. Simultaneously, by limiting the freeness of the first wood pulp to 290-310 mL and the freeness of the second wood pulp to 210-230 mL, it enhances the fibrillation of long fibers and softens the lignin in the bleached mechanical pulp, allowing the fibers of different pulps to interweave better and the fiber distribution to be more uniform. This improves the uniformity of the resulting base paper, and consequently, the dyeing uniformity of the base paper.

[0054] Please see Figure 2 , Figure 2 This is a schematic flowchart of the second embodiment of the method for preparing the dyed base paper of this application. Figure 2 As shown, in this embodiment, the preparation method includes:

[0055] S21: Obtain a mixed pulp; wherein the mixed pulp includes a first wood pulp and a second wood pulp, the first wood pulp has a weight part of 17-20, the freeness of the first wood pulp is 290-310 mL, and the freeness of the second wood pulp is 210-230 mL; wherein the first wood pulp is bleached long-fiber wood pulp, and the second wood pulp is bleached mechanical pulp.

[0056] For details on the acquisition process, please refer to the description in S11, which will not be repeated here.

[0057] S22: Add filler, starch and retention aid to mixed pulp; form paper from the mixed pulp containing filler, starch and retention aid to obtain base paper.

[0058] In this embodiment, fillers, starch, and retention aids are added to the mixed pulp, and the mixed pulp containing fillers, starch, and retention aids is then processed to obtain base paper.

[0059] The purpose of adding fillers during the papermaking process is to improve the printing performance of the paper and reduce costs.

[0060] The addition of starch is to utilize starch coating technology to uniformly mix starch, fillers, and pulp together and appropriately flocculate them, so as to prevent the pulp and filler particles from being lost during dehydration, thereby reducing the amount of pulp used and thus reducing the preparation cost of the base paper.

[0061] Since the decrease in freeness will slow down the filtration rate, retention aid powder is added to the mixed pulp to compensate for the loss of filtration.

[0062] Among them, retention aids include cationic polyacrylamides (CPAM).

[0063] S23: Applying sizing to the base paper using a surface sizing agent; wherein, the surface sizing agent includes water, rosin sizing agent, and styrene-acrylic emulsion sizing agent.

[0064] Among them, rosin sizing agents include cationic dispersed rosin gum.

[0065] Among them, styrene-acrylic emulsion sizing agents (SAE type sizing agents) are polymer surface sizing agents synthesized mainly from petroleum by-products such as styrene, acrylic acid, and acrylates. Styrene and acrylates, in particular, exhibit good adhesion to inks.

[0066] Specifically, please refer to Figure 3 , Figure 3 yes Figure 2 A flowchart illustrating a specific embodiment of S23. In this embodiment, the step of applying a surface sizing agent to the base paper includes:

[0067] S231: Prepare rosin sizing agent, styrene-acrylic emulsion sizing agent, and water.

[0068] In this embodiment, rosin sizing agent, styrene-acrylic emulsion sizing agent, and water are prepared according to preset weight parts.

[0069] The rosin sizing agent and the styrene-acrylic emulsion sizing agent are in equal weight proportions.

[0070] S232: Add rosin sizing agent and styrene-acrylic emulsion sizing agent to water, stir evenly to obtain surface sizing agent; wherein, the total mass fraction of rosin sizing agent and styrene-acrylic emulsion sizing agent is 4-6%.

[0071] In this embodiment, before adding rosin sizing agent and styrene-acrylic emulsion sizing agent, the temperature of the water is adjusted to 40-50 degrees Celsius to make the rosin sizing agent and styrene-acrylic emulsion sizing agent mix more evenly.

[0072] S233: Applying sizing agents to the base paper.

[0073] In this embodiment, the amount of sizing agent applied can be adjusted according to the weight that the surface of the base paper can absorb. For example, if the surface of the base paper can absorb a large amount of weight, the amount of sizing agent can be increased appropriately.

[0074] The weight that the base paper surface can absorb is related to the absorption performance of the base paper surface.

[0075] The absorbency of the base paper surface is measured by the Cobb (water absorption capacity of paper and paperboard) value and sizing degree. A higher Cobb value indicates lower resistance to liquids on the base paper surface, meaning the liquid will penetrate as much as possible into the paper, resulting in less liquid absorption by the surface fibers. A lower Cobb value indicates higher resistance to liquids on the base paper surface, meaning the liquid cannot wet the surface fibers. Sizing degree, also known as water resistance, indicates higher resistance to liquids on the base paper surface, meaning the liquid cannot wet the surface fibers. A lower sizing degree indicates lower resistance to liquids on the base paper surface, meaning the liquid will penetrate as much as possible into the paper, resulting in less liquid absorption by the surface fibers.

[0076] If no sizing agent is added before papermaking, the resulting base paper will have a high Cobb value and low sizing degree. If the base paper is not sizing, the dye will penetrate into the interior of the base paper as much as possible during subsequent dyeing. The surface of the base paper absorbs less dye, requiring more dye to completely dye the surface. Furthermore, because the base paper absorbs a lot of dye, it will also affect subsequent lamination.

[0077] Therefore, it is necessary to improve the surface absorption properties of unsized base paper by surface sizing, so that the sized base paper has a suitable Cobb value and sizing degree. At this time, the paper surface has both a certain degree of permeability and a certain degree of water resistance, which is conducive to subsequent dyeing.

[0078] In this embodiment, after surface sizing of the base paper that has not been sized in pulp using a surface sizing agent including water, rosin sizing agent and styrene-acrylic emulsion sizing agent, the Cobb value of the base paper surface can be appropriately reduced and the sizing degree can be increased.

[0079] Understandably, by improving the Cobb value and sizing degree of the base paper, the absorption performance of the paper surface for dyes can be enhanced. In the subsequent dyeing process, the paper surface can absorb dyes more evenly, so that the dyes can completely penetrate the paper surface, thereby further improving the dyeing uniformity of the base paper.

[0080] In existing technology, sizing agents are added to the mixed pulp before papermaking for in-pulp sizing, and starch gelatinized liquid is used as a surface sizing agent to sizing the base paper after papermaking. However, after adding a small amount of sizing agent to the pulp, the Cobb value of the resulting base paper is significantly lower than that of paper without added sizing agent, and the sizing degree is significantly increased. If starch gelatinized liquid is then used to coat the surface of the base paper, the Cobb value will be further reduced and the sizing degree will be increased. However, if the Cobb value of the base paper is too low, the surface of the base paper will be more resistant to dyes, and the dyes will not be able to wet the surface fibers. It is necessary to add impregnating agents such as ethylene propanol. However, such impregnating agents increase the volatile organic compounds (VOCs) of the paper, and their addition should be avoided as much as possible.

[0081] Furthermore, because starch gelatinized liquid has strong sealing properties, using starch gelatinized liquid for surface coating will form a film with strong sealing properties on the surface of the base paper. The starch film has low affinity with the fiber and cannot improve the absorption performance of the base paper surface for dyes, which will cause the dyed base paper to become mottled and the paper surface to turn white.

[0082] Unlike existing technologies, the SAE-type surface sizing agent used in this embodiment contains multiple functional active groups (styrene, acrylate, etc.) in its molecular structure. Its affinity for fibers is much higher than that of starch. Using a surface sizing agent including the SAE-type surface sizing agent to sizing paper can impart more and better properties to the paper surface, giving it better water resistance and ink absorption, enabling it to hold various inks.

[0083] S24: Coating the sized base paper with dye padding solution to obtain dyed base paper.

[0084] Understandably, because the different pulp fibers in the mixed pulp are mixed more evenly, the uniformity of the base paper produced is also higher. Furthermore, the base paper after sizing has better water resistance and ink absorption. Therefore, the resulting dyed base paper has uniform and saturated color, is not easy to fade, and is easy to sizing and bonding.

[0085] Unlike existing technologies, this embodiment limits the weight of the first wood pulp in the mixed pulp to 17-20 parts, thereby reducing the content of long fibers in the mixed pulp and avoiding uneven fiber distribution caused by excessive long fiber content. Simultaneously, by limiting the freeness of the first wood pulp to 290-310 mL and the freeness of the second wood pulp to 210-230 mL, it enhances the fibrillation of long fibers and softens the lignin in the bleached mechanical pulp, allowing for better interweaving of fibers from different pulps and a more uniform fiber distribution. This improves the uniformity of the resulting base paper and consequently, the dyeing uniformity of the base paper. Furthermore, by using a surface sizing agent comprising water, rosin, and styrene-acrylic emulsion sizing agents to sizing the base paper, the sized base paper achieves a suitable Cobb value and sizing degree, resulting in better water resistance and ink absorption on the paper surface, further improving the dyeing uniformity of the base paper.

[0086] Correspondingly, this application provides a dyeing base paper.

[0087] Unlike existing technologies, the dyeing base paper provided in this embodiment has uniform and saturated color, is not easy to fade, and is easy to apply glue and bond, making it suitable for applications with high quality requirements.

[0088] To facilitate understanding of the embodiments of this application, the following non-limiting embodiments are provided to further illustrate the application in detail.

[0089] Example 1

[0090] A mixed pulp was obtained, comprising a first wood pulp, a second wood pulp, and a third wood pulp. The first wood pulp consisted of 20 parts, the second wood pulp of 3 parts, and the third wood pulp of 77 parts. The freeness of the first wood pulp was 300 mL, the second wood pulp of 220 mL, and the third wood pulp of 310 mL. The first wood pulp was NBKP, the second wood pulp was APMP, and the third wood pulp was LBKP. Fillers, starch, and retention aids were added to the mixed pulp, and the mixed pulp containing fillers, starch, and retention aids was then formed to obtain base paper.

[0091] Example 2

[0092] A mixed pulp was obtained, comprising a first wood pulp, a second wood pulp, and a third wood pulp. The first wood pulp consisted of 17 parts, the second wood pulp of 3 parts, and the third wood pulp of 80 parts. The freeness of the first wood pulp was 290 mL, the second wood pulp of 210 mL, and the third wood pulp of 320 mL. The first wood pulp was NBKP, the second wood pulp was APMP, and the third wood pulp was LBKP. Fillers, starch, and retention aids were added to the mixed pulp, and the mixed pulp containing fillers, starch, and retention aids was then formed to obtain base paper.

[0093] Example 3

[0094] A mixed pulp was obtained, comprising a first wood pulp, a second wood pulp, and a third wood pulp. The first wood pulp consisted of 18 parts, the second wood pulp of 5 parts, and the third wood pulp of 77 parts. The freeness of the first wood pulp was 300 mL, the second wood pulp of 220 mL, and the third wood pulp of 310 mL. The first wood pulp was NBKP, the second wood pulp was APMP, and the third wood pulp was LBKP. Fillers, starch, and retention aids were added to the mixed pulp, and the mixed pulp containing fillers, starch, and retention aids was then formed to obtain base paper.

[0095] Example 4

[0096] A mixed pulp was obtained, comprising a first wood pulp, a second wood pulp, and a third wood pulp, with 20 parts of the first wood pulp, 9 parts of the second wood pulp, and 71 parts of the third wood pulp. The freeness of the first wood pulp was 310 mL, the freeness of the second wood pulp was 230 mL, and the freeness of the third wood pulp was 310 mL. The first wood pulp was NBKP, the second wood pulp was APMP, and the third wood pulp was LBKP. Fillers, starch, and retention aids were added to the mixed pulp, and the mixed pulp containing fillers, starch, and retention aids was then formed to obtain base paper.

[0097] Control group 1

[0098] A mixed pulp was obtained, comprising a first wood pulp, a second wood pulp, and a third wood pulp. The first wood pulp consisted of 22 parts, the second wood pulp of 3 parts, and the third wood pulp of 75 parts. The freeness of the first wood pulp was 330 mL, the second wood pulp of 250 mL, and the third wood pulp of 310 mL. The first wood pulp was NBKP, the second wood pulp was APMP, and the third wood pulp was LBKP. Fillers, starch, sizing agents, and retention aids were added to the mixed pulp. The mixed pulp containing fillers, starch, sizing agents, and retention aids was then formed to obtain base paper. The amount of sizing agent added was 4 kg.

[0099] Control group 2

[0100] A mixed pulp was obtained, comprising a first wood pulp, a second wood pulp, and a third wood pulp. The first wood pulp consisted of 20 parts, the second wood pulp of 3 parts, and the third wood pulp of 77 parts. The freeness of the first wood pulp was 330 mL, the second wood pulp of 250 mL, and the third wood pulp of 310 mL. The first wood pulp was NBKP, the second wood pulp was APMP, and the third wood pulp was LBKP. Fillers, starch, sizing agents, and retention aids were added to the mixed pulp. The mixed pulp containing fillers, starch, sizing agents, and retention aids was then formed to obtain base paper. The amount of sizing agent added was 5 kg.

[0101] For the base papers produced in Examples 1, 2, 3, and 4 and Control Groups 1 and 2, the following parameters were tested: basis weight, thickness, bulk, tensile index, bursting index, cohesion, folding endurance, interlacing, Cobb value, and sizing degree. The test results are shown in Table 1.

[0102] Table 1

[0103]

[0104]

[0105] Among them, Beta Formation is an instrument for measuring fiber interlacing. The smaller the value measured by Beta Formation, the better the fiber interlacing and the better the uniformity of the base paper.

[0106] As shown in the table above, keeping the pulp freeness constant and only changing the NBKP dosage (from 22 parts to 20 parts), the Beta Formation of Control Group 2 and Control Group 1 were similar, indicating that the uniformity of the base paper was not improved. While changing the NBKP dosage, simultaneously adjusting the freeness of NBKP and APMP (NBKP freeness decreased from 330 mL to 290-310 mL, and APMP freeness decreased from 250 mL to 210-230 mL), the Beta Formation in Examples 1, 2, 3, and 4 all decreased, indicating that the uniformity of the base paper was improved, which is beneficial for improving the uniformity of subsequent dyeing. In Control Groups 1 and 2, after adding a small amount of sizing agent, the resulting base paper had suitable Cobb values ​​and sizing degrees. However, in Examples 1, 2, 3, and 4, due to the lack of in-pulp sizing, the resulting base paper had higher Cobb values ​​and lower sizing degrees.

[0107] Example 5

[0108] The base paper obtained in Example 1 was sized using a surface sizing agent, which included water, rosin sizing agent, and styrene-acrylic emulsion sizing agent. The total mass fraction of rosin sizing agent and styrene-acrylic emulsion sizing agent was 4-6%, and the weight fractions of rosin sizing agent and styrene-acrylic emulsion sizing agent were equal. The sized base paper was then dyed to obtain dyed base paper.

[0109] Example 6

[0110] The base paper obtained in Example 2 was sized using a surface sizing agent, which included water, rosin sizing agent, and styrene-acrylic emulsion sizing agent. The total mass fraction of rosin sizing agent and styrene-acrylic emulsion sizing agent was 4-6%, and the weight fractions of rosin sizing agent and styrene-acrylic emulsion sizing agent were equal. The sized base paper was then dyed to obtain dyed base paper.

[0111] Example 7

[0112] The base paper obtained in Example 3 was sized using a surface sizing agent, which included water, rosin sizing agent, and styrene-acrylic emulsion sizing agent. The total mass fraction of rosin sizing agent and styrene-acrylic emulsion sizing agent was 4-6%, and the weight fractions of rosin sizing agent and styrene-acrylic emulsion sizing agent were equal. The sized base paper was then dyed to obtain dyed base paper.

[0113] Example 8

[0114] The base paper obtained in Example 4 was sized using a surface sizing agent, which included water, rosin sizing agent, and styrene-acrylic emulsion sizing agent. The total mass fraction of rosin sizing agent and styrene-acrylic emulsion sizing agent was 4-6%, and the weight fractions of rosin sizing agent and styrene-acrylic emulsion sizing agent were equal. The sized base paper was then dyed to obtain dyed base paper.

[0115] Control group 3

[0116] The paper obtained from control group 1 was sized using a starch gelatinized solution. The sized paper was then dyed to obtain dyed paper.

[0117] Control group 4

[0118] The paper obtained from control group 2 was sized using a starch gelatinized solution. The sized paper was then dyed to obtain dyed paper.

[0119] The Cobb value and sizing degree of the dyed base paper produced in Examples 5, 6, 7, and 8 and Control Groups 3 and 4 were tested, and the test results are shown in Table 2.

[0120] Table 2

[0121]

[0122] As shown in the table above, coating the surface of internally sized paper with starch gelatinized liquid further reduces the Cobb value and increases the sizing degree. However, if the Cobb value of the paper is too low, the surface of the paper will have a higher resistance to dye, which may make subsequent dyeing difficult. Surface sizing of unsized paper using surface sizing agents, including water, rosin, and styrene-acrylic emulsion sizing agents, can appropriately reduce the Cobb value and increase the sizing degree of the paper surface. This results in a suitable Cobb value and sizing degree for the sized paper, allowing for more uniform dye absorption during subsequent dyeing, ensuring complete dye penetration and further improving the dyeing uniformity of the paper.

[0123] The microstructure of the dyed base paper in Example 5 and Control Group 3 was observed using scanning electron microscopy (SEM). For details, please refer to [link to relevant documentation]. Figure 4a and Figure 4b , Figure 4a and Figure 4b These are SEM images of the dyed base paper in Example 5 and Control Group 3 of this application, respectively.

[0124] Depend on Figure 4a and Figure 4b It can be seen that the dyed base paper in Example 5 exhibits a uniform and saturated color, indicating that after sizing the base paper with good uniformity using a surface sizing agent comprising water, rosin sizing agent, and styrene-acrylic emulsion sizing agent, the resulting base paper surface has good dye absorption performance and good dyeing uniformity. In contrast, the dyed base paper in Control Group 3 has a whitish color with inconsistent shades, indicating that after sizing the base paper with average uniformity using starch gelatinization solution, the resulting base paper surface has poor dye absorption performance and is difficult to dye.

[0125] Unlike existing technologies, this application reduces the content of long fibers in the mixed pulp by limiting the weight of the first wood pulp to 17-20 parts, thus avoiding uneven fiber distribution caused by excessive long fiber content. Simultaneously, by limiting the freeness of the first wood pulp to 290-310 mL and the freeness of the second wood pulp to 210-230 mL, it enhances the fibrillation of long fibers and softens the lignin in the bleached mechanical pulp, allowing for better interweaving of fibers from different pulps and a more uniform fiber distribution. This improves the uniformity of the resulting base paper and consequently, the dyeing uniformity of the base paper. Furthermore, by using a surface sizing agent comprising water, rosin, and styrene-acrylic emulsion sizing agents, the sized base paper achieves a suitable Cobb value and sizing degree, resulting in better water resistance and ink absorption on the paper surface, further improving the dyeing uniformity of the base paper.

[0126] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for preparing dyed base paper, characterized in that, include: A mixed pulp is obtained; wherein the mixed pulp comprises a first wood pulp and a second wood pulp, the first wood pulp having a weight part of 17-20 and a freeness of 290-310 mL, and the second wood pulp having a freeness of 210-230 mL; wherein the first wood pulp is bleached long-fiber wood pulp, and the second wood pulp is bleached mechanical pulp; The mixed pulp also includes a third wood pulp; the third wood pulp is bleached short fiber wood pulp. The step of obtaining the mixed pulp includes: Prepare the following raw materials according to the preset weight parts: first wood pulp, 17-20 parts; second wood pulp, 3-9 parts; third wood pulp, 71-80 parts; The first wood pulp, the second wood pulp, and the third wood pulp are respectively subjected to pulping treatment so that the freeness of the first wood pulp is 290-310 mL, the freeness of the second wood pulp is 210-230 mL, and the freeness of the third wood pulp is 300-320 mL. The first wood pulp, the second wood pulp, and the third wood pulp after refining are mixed evenly to obtain the mixed pulp; The mixed pulp is processed into paper to obtain base paper; The base paper is sizing; The sized base paper is dyed to obtain the dyed base paper.

2. The preparation method according to claim 1, characterized in that, The step of applying sizing to the base paper includes: The base paper is sized using a surface sizing agent; wherein the surface sizing agent includes water, rosin sizing agent, and styrene-acrylic emulsion sizing agent.

3. The preparation method according to claim 2, characterized in that, The step of applying a surface sizing agent to the base paper includes: Prepare the rosin sizing agent, the styrene-acrylic emulsion sizing agent, and the water; The rosin sizing agent and the styrene-acrylic emulsion sizing agent are added to the water and stirred evenly to obtain the surface sizing agent; wherein the total mass fraction of the rosin sizing agent and the styrene-acrylic emulsion sizing agent is 4-6%; The base paper is sizing using the surface sizing agent.

4. The preparation method according to claim 3, characterized in that, The steps of preparing the rosin sizing agent, the styrene-acrylic emulsion sizing agent, and the water include: Prepare the rosin sizing agent, the styrene-acrylic emulsion sizing agent, and the water according to the preset weight parts; wherein the weight parts of the rosin sizing agent and the styrene-acrylic emulsion sizing agent are equal.

5. The preparation method according to claim 4, characterized in that, The rosin sizing agent includes cationic dispersed rosin gum.

6. The preparation method according to claim 1, characterized in that, The step of forming the mixed pulp to obtain base paper includes: Fillers, starch, and retention aids are added to the mixed pulp; The mixed pulp containing the filler, the starch, and the retention aid is processed to obtain the base paper.

7. The preparation method according to claim 1, characterized in that, The step of dyeing the sized base paper to obtain the dyed base paper includes: The sized base paper is coated with a dye padding solution to obtain the dyed base paper.

8. A dyeing base paper, characterized in that, The dyeing base paper is prepared by the method for preparing dyeing base paper according to any one of claims 1 to 7.

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