A method for producing a folding-endurance base paper and folding-endurance base paper

Abstract

The application discloses a production method of a folding-resistant base paper and the folding-resistant base paper, and relates to the field of paper production. The production method comprises the following steps: mixing wood pulp, calcium carbonate fillers, cationic starch after cooking and a sizing agent to obtain mixed pulp; purifying and removing residues from the mixed pulp to obtain front pulp; adding uncooked cationic starch, hydrophobically modified starch and dry strength agent into the front pulp to obtain raw pulp; performing screening treatment on the raw pulp; performing wire-feeding treatment after the screening treatment; and performing drying after the wire-feeding treatment. In the foregoing manner, the uncooked cationic starch and the hydrophobically modified starch are added before drying, the uncooked cationic starch is gelatinized by using the subsequent drying process, and then the uncooked cationic starch forms a network structure with the hydrophobically modified starch, so that the strength and cohesion of the base paper are improved, and the folding resistance of the base paper is improved.

Description

Technical Field

[0001] This application relates to the field of papermaking technology, and in particular to a method for producing fold-resistant base paper and the fold-resistant base paper thereof. Background Technology

[0002] With the development of the paper industry, the requirements for base paper have also increased. Especially in some industries, the strength and folding endurance of base paper are required to be higher than in other industries, such as playing card paper in the entertainment industry. In existing technologies, methods to improve the strength and folding endurance of base paper generally include reducing ash content, increasing the amount of long fibers, reducing pulping freeness, increasing auxiliary pulping chemicals, and increasing the amount of cationic starch added. Alternatively, reinforcement can be achieved by utilizing the stiffness and strength of the composite adhesive itself during subsequent lamination to improve the paper's cohesiveness.

[0003] However, the improvement in the quality and scope of the raw paper produced by the above methods is limited. Excessive adjustment can also lead to dehydration difficulties, resulting in serious problems such as paper breakage and machine failure. The finished product is also difficult to meet the requirements of high folding endurance and high strength for raw paper such as playing cards. Summary of the Invention

[0004] The embodiments of this application provide a method for producing fold-resistant base paper and the fold-resistant base paper itself, which can improve the cohesiveness of the paper by utilizing the papermaking method of this application, thereby improving its strength and folding endurance.

[0005] In a first aspect, embodiments of this application provide a method for producing fold-resistant base paper, comprising:

[0006] A mixed pulp is prepared by mixing wood pulp, calcium carbonate filler, cooked cationic starch and sizing agent;

[0007] The mixed pulp is purified and slag removed to obtain the pre-pulp;

[0008] Uncooked cationic starch, hydrophobically modified starch, and dry strength agent are added to the pre-slurry to obtain the original slurry;

[0009] The pulp is screened, then screened, and then dried.

[0010] In some embodiments, the amount of uncooked cationic starch used is 40-50 kg / t paper, the amount of hydrophobic modified starch used is 5-8 kg / t paper, and the amount of dry strength agent used is 5-20 kg / t paper.

[0011] In some embodiments, the step of adding uncooked cationic starch, hydrophobically modified starch and dry strength agent to the pre-slurry to obtain the original slurry includes: first mixing the uncooked cationic starch with the hydrophobically modified starch, then adding water to disperse the mixture to obtain a starch slurry, and then adding the starch slurry and the dry strength agent to the pre-slurry.

[0012] In some embodiments, in the step of first mixing the uncooked cationic starch with the hydrophobic modified starch, and then adding water to disperse the mixture, the dispersion ratio of the uncooked cationic starch to the hydrophobic modified starch is in the range of [7.5-9.5]:[0.5-2], and the solid content of the starch slurry is 25-35%, and the oven-dry weight of the starch slurry is 40-52 kg.

[0013] In some embodiments, after the drying step following the on-grid treatment, the method further includes the steps of: performing surface sizing treatment, performing secondary drying after the surface sizing treatment to obtain semi-base paper, and applying off-machine coating to the semi-base paper to obtain finished base paper.

[0014] The steps of the external coating process include: applying a primer, a top coat, and applying adhesive to the back side.

[0015] In some embodiments, the coating amount of the primer is 8-12 g / m². 2 The coating amount of the topcoat is 10-12 g / m². 2 The amount of adhesive applied to the back side is 1-3 g / m. 2 The solid content of the coatings used in the primer and the topcoat is 66-68%.

[0016] In some embodiments, the wood pulp includes softwood pulp and hardwood pulp.

[0017] In some embodiments, the mass percentage of softwood pulp is 20-30%, the mass percentage of hardwood pulp is 70-80%, the mass percentage of calcium carbonate filler is 6-10%, the amount of cooked cationic starch is 9-11 kg / t paper, and the amount of sizing agent is 8.5-11.5 kg / t paper.

[0018] In some embodiments, the internet access processing includes: adjusting internet traffic and controlling the basis weight of the scanned paper at 120-123 g / m³. 2 between.

[0019] Secondly, embodiments of this application provide a fold-resistant base paper, which is prepared using the production method described above.

[0020] The beneficial effects of this application are: by adding uncooked cationic starch and hydrophobic modified starch before drying, the ungelatinized cationic starch is gelatinized during the subsequent drying process, thereby forming a network structure with the hydrophobic modified starch, which can improve the strength and cohesion of the base paper, and thus increase the number of folds the base paper can withstand. Attached Figure Description

[0021] 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.

[0022] Figure 1 This is a flowchart of one embodiment of the method for producing fold-resistant base paper according to this application;

[0023] Figure 2 This is a flowchart of another embodiment of the method for producing fold-resistant base paper according to this application;

[0024] Figure 3 This is a flowchart of another embodiment of the method for producing fold-resistant base paper according to this application;

[0025] Figure 4 This is a flowchart of another embodiment of the method for producing fold-resistant base paper according to this application;

[0026] Figure 5 This is a simplified structural diagram of one embodiment of the production system for fold-resistant base paper of this application. Detailed Implementation

[0027] 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 a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0028] This embodiment provides the following: Figure 1 The method for producing a fold-resistant base paper shown includes:

[0029] Step S100: Select wood pulp, calcium carbonate filler, cooked cationic starch and sizing agent and mix them to obtain a mixed pulp;

[0030] Step S200: The mixed pulp is purified and slag removed to obtain the pre-pulp;

[0031] Step S300: Add uncooked cationic starch, hydrophobic modified starch and dry strength agent to the pre-slurry and mix to obtain the original slurry;

[0032] Step S400: The raw pulp is screened, then wire-fed, and finally dried.

[0033] First, the steps in the above production method will be introduced:

[0034] In step S100 of this embodiment, wood pulp, as one of the main raw materials for papermaking, generally includes long-fiber wood pulp and short-fiber wood pulp, aiming to provide a fibrous base for paper. Calcium carbonate filler is used to improve the optical and physical properties of paper, such as increasing opacity and whiteness, as well as increasing softness and density. Cationic starch after cooking is an essential factor in paper forming and can improve paper strength. Specifically, the positive charge of cationic starch can adsorb onto the negatively charged fiber surface, promoting a tight bond between fibers, thereby enhancing paper strength. Furthermore, the cationic starch particles can fill the gaps and pores in the paper, making the paper structure denser and reducing lint and dust shedding. Sizing agents are used to improve the physical properties of paper, such as strength, surface smoothness, surface evenness, and water resistance, and can shorten paper forming time.

[0035] In step S200 of this embodiment, the mixed pulp is purified and deslag is removed to obtain the pre-pulp. The main purpose is to remove slag and impurities from the mixed pulp and improve the smoothness and fineness of the subsequent formed paper.

[0036] In step S300 of this embodiment, the purpose of adding uncooked cationic starch, hydrophobically modified starch, and dry strength agent is to improve the quality of the base paper to a higher strength while ensuring paper formation, thereby further increasing the paper's folding endurance. This step is a key step in this application. Uncooked cationic starch differs from cooked cationic starch. Cooked cationic starch is already in a gelatinized state and is added in step S100 to ensure paper formation. However, the uncooked cationic starch added in step S300, since it has not been cooked, is added to the pre-slurry in powder form. Through the drying step in the subsequent papermaking process, it undergoes spontaneous gelatinization, which allows it to mix with the relatively large-particle hydrophobically modified starch to form a network structure, thereby improving strength. The addition of the dry strength agent is to enhance dehydration and increase the drying speed and strength of the paper.

[0037] In step S400 of this embodiment, the pulp still needs to be screened to ensure that any residue or impurities generated after the two additions of raw materials are removed, thereby ensuring that the subsequent paper forming process achieves high flatness and density. The web forming process is the initial stage of converting the pulp into paper. The pulp is evenly sprayed or spread onto the forming wire of the paper machine to form a thin wet sheet, which then enters the drying step to form the paper.

[0038] In one example of this embodiment, as shown in the appendix Figure 2 As shown, the wood pulp in step S100 includes softwood pulp and hardwood pulp. Softwood pulp is a long-fiber wood pulp, and hardwood pulp is a short-fiber wood pulp. The two are mixed to complete the pulping of the fiber raw materials in the paper.

[0039] In one example of this embodiment, further as shown in the appendix Figure 2 As shown, before step S100, the procedure further includes:

[0040] Step S01 involves processing the long-fiber and short-fiber wood pulps separately through processes such as crushing, screening, dispersion, bleaching, and refining to obtain long-fiber and short-fiber pulps, respectively. The freeness (CsF) of the long-fiber pulp can be controlled between 320-380 ml, and the freeness (CsF) of the short-fiber pulp between 330-400 ml. CsF refers to the Canadian Standard Freeness. Further, the freeness of the long-fiber pulp can be controlled at 320 ml, 350 ml, 360 ml, or 380 ml, and the freeness of the short-fiber pulp can be controlled at 330 ml, 350 ml, 360 ml, or 400 ml.

[0041] In one example of this embodiment, step S100 is optimized by setting the mass percentage of softwood pulp to 20-30%, the mass percentage of hardwood pulp to 70-80%, the mass percentage of calcium carbonate filler to 6-10%, and the amount of cationic starch after cooking to 9-11 kg / t paper; the amount of sizing agent is 8.5-11.5 kg / t paper. Further, the sizing agent in this application can be an alkyl ketene dimer (AKD Alkyl Ketene Dimer). The mass percentage of softwood pulp can be set to 20%, 25%, or 30%. The mass percentage of hardwood pulp can be set to 70%, 75%, or 80%. The mass percentage of calcium carbonate filler can be set to 6%, 8%, or 10%. The amount of cationic starch after cooking can be set to 9 g / t paper, 10 g / t paper, or 11 g / t paper. The amount of sizing agent can be set to 8.5 kg / t paper, 10 kg / t paper, or 11.5 kg / t paper. Furthermore, the ash content of the calcium carbonate filler can be controlled to be around 7-8%, which can be 7%, 8% or 9%, and in a specific implementation scheme it can be 8%.

[0042] In one example of this embodiment, the purification and slag removal method in step S200 is set as follows: purification and slag removal are achieved through a cone-shaped purifier.

[0043] In one example of this embodiment, step S300 is optimized by setting the amount of uncooked cationic starch to 40-50 kg / t of paper, the amount of hydrophobically modified starch to 5-8 kg / t of paper, and the amount of dry strength agent to 5-20 kg / t of paper. Specifically, the amount of uncooked cationic starch can be set to 40 kg / t of paper, 45 kg / t of paper, or 50 kg / t of paper. The amount of hydrophobically modified starch can be set to 5 kg / t of paper, 6 kg / t of paper, 7 kg / t of paper, or 8 kg / t of paper. The amount of dry strength agent can be set to 5 kg / t of paper, 15 kg / t of paper, or 20 kg / t of paper.

[0044] In one example of this embodiment, as shown in the appendix Figure 3 As shown, step S300 is optimized as follows: the step of adding uncooked cationic starch, hydrophobically modified starch, and dry strength agent to the pre-slurry to obtain the original slurry includes:

[0045] Step S301 involves first mixing the uncooked cationic starch with the hydrophobic modified starch, then adding water to disperse the mixture to obtain a starch slurry. The starch slurry and a dry strength agent are then added to the initial slurry. The purpose of this step is to ensure that the uncooked cationic starch can be initially mixed with the hydrophobic modified starch, ensuring sufficient contact and the formation of a network structure during subsequent drying.

[0046] In one example of this embodiment, step S301 is optimized. In the step of first mixing uncooked cationic starch and hydrophobic modified starch, and then dispersing the mixture with water, the dispersion ratio of uncooked cationic starch to hydrophobic modified starch is set to a range of [7.5-9.5]:[0.5-2], and the solid content of the starch slurry is 25-35%. The dispersion ratio range can be 7.5:0.5, 8:1, or 9.5:2. In a specific implementation, it can be 8:1, i.e., 8 parts of uncooked cationic starch and 1 part of hydrophobic modified starch. The solid content of the starch slurry can be set to 25%, 30%, or 35%. Furthermore, the oven-dry weight of the starch slurry (usually referring to the oven-dry content of paper, which is a relative concept used to describe the proportion of dry matter in paper after moisture removal) can be set between 40-52 kg, for example, 40 kg, 45 kg or 52 kg. The specific ratio of uncooked cationic starch to hydrophobic modified starch contained therein can be set with reference to the dispersion ratio range mentioned above.

[0047] Furthermore, the dry strength agent of this application may be cationic GPAM (glyoxalated polyacrylamide).

[0048] In one embodiment, the screening process in step S400 is performed by using a pressure sieve.

[0049] In one embodiment, the internet access processing in step S400 includes: adjusting the internet bandwidth and controlling the basis weight of the scanned paper at 120-123 g / m³. 2 Between these steps, a paper basis weight determination process is required before subsequent sizing (step S500) to prepare for subsequent basis weight production. The paper basis weight can be set to 120 g / m³. 2 122g / m 2 Or 123g / m 2 .

[0050] In one embodiment, the Internet access process in step S400 is performed by accessing the Internet via a headbox.

[0051] In one example of this embodiment, as shown in the appendix Figure 4 As shown, after step S400, that is, after the drying step following the wire mesh processing, the following steps are also included:

[0052] S500 undergoes surface sizing treatment, followed by secondary drying to obtain semi-base paper. The semi-base paper is then coated externally to obtain the finished base paper.

[0053] The steps of external coating include: applying a primer, a top coat, and applying adhesive to the back side.

[0054] In one example of this embodiment, step S500 is optimized by setting the coating amount of the primer to 8-12 g / m². 2 The coating amount of the topcoat is 10-12 g / m². 2 The amount of adhesive applied to the back side is 1-3 g / m². 2 The application rate of the primer can be selected as 8 g / m². 2 10g / m 2 Or 12g / m 2 The application rate of the topcoat can be selected as 10g / m². 2 11g / m 2 Or 12g / m 2 The application rate can be selected as 1g / m³. 2 2g / m 2 or 3g / m 2 Furthermore, the total coating weight of the primer and topcoat can be controlled to be between 18-24 g / m². 2 For example, it can be controlled between 18g / m 2 23g / m 2 Or 24g / m 2 Additionally, the solid content of the coating can be controlled between 66-68%, for example, at 66%, 67%, or 68%.

[0055] In one example of this embodiment, step S500 is further optimized by setting the coating material for the topcoat or basecoat to include ultrafine calcium carbonate, ultrafine kaolin, SBL latex (styrene-butadiene latex, a stable emulsion formed by low-temperature polymerization of butadiene and styrene), and WEB latex. WEB latex is a special latex for rotary coated paper, and by using this latex, the porosity of the coating is improved after film formation.

[0056] The ultrafine kaolin can be an ultrafine kaolin with a diameter of 2 μm and a particle content of over 98%. Further, in one example, the composition is set as follows: 79-82 parts ultrafine calcium carbonate, 18-24 parts ultrafine kaolin, 9-12 parts SBL latex, and 1-3 parts WEB latex. In a specific embodiment, the ultrafine calcium carbonate can be set to 79, 80, or 82 parts, specifically 80 parts. The ultrafine kaolin can be set to 18, 20, or 24 parts, specifically 20 parts in a specific embodiment. The SBL latex can be set to 9, 10, or 12 parts, specifically 10 parts in a specific embodiment. The WEB latex can be set to 1, 2, or 3 parts, specifically 2 parts in a specific embodiment.

[0057] In one example, the basis weight (weight of paper per unit area) of the finished base paper produced using the above method is 125-155 g / m². 2 The thickness is between 150-162 μm.

[0058] In one embodiment of this application, a fold-resistant base paper is also provided, which is prepared by a production method combining any one or more of the above embodiments.

[0059] Secondly, the following provides some descriptions and examples of the application of the technology of this application in the production and manufacturing of playing cards, so that those skilled in the art can understand it. It should be noted that the folding-resistant base paper of this application is not limited to the application in playing cards. For example, the technical solution of this application can also be used in categories that have high requirements for paper strength and folding resistance, such as paper for book printing, packaging paper, map making paper, and journal paper.

[0060] First, let's introduce the existing playing card paper. The quality requirements for playing cards mainly include folding endurance, opacity, interlayer bonding strength, and stiffness. The purpose is to increase the number of uses, prevent light transmission for cheating, and improve the feel of the card. Ordinary playing cards typically have a folding endurance of around 500 times, and an interlayer bonding strength of approximately 300 J / m². 2 Approximately 5 grams of glue are applied during the final stage of playing card production to increase strength. Taking the production method of black-core playing cards as an example, the amount of glue applied is approximately 5 grams. This small amount of glue does not significantly affect the folding endurance or interlayer bonding strength of the playing card paper; the base paper still provides the necessary strength. Generally speaking, the interlayer bonding strength of a 150-gram single-sided coated paper is 250-300 J / m². 2 about.

[0061] The following specific embodiments are provided for further explanation:

[0062] In one embodiment of this application, the provided production method includes the following steps:

[0063] Step S01 involves processing the long-fiber wood pulp and short-fiber wood pulp separately through processes such as crushing, screening, dispersion, bleaching, and refining to obtain long-fiber pulp and short-fiber pulp respectively. The long-fiber wood pulp is made from softwood pulp, and the short-fiber wood pulp is made from hardwood pulp, with a ratio of softwood pulp to hardwood pulp of 20:80. The freeness of the long-fiber pulp is controlled at 360 ml, and the freeness of the short-fiber pulp is controlled at 350 ml.

[0064] In step S100, wood pulp, calcium carbonate filler, cooked cationic starch, and sizing agent are mixed to obtain a mixed pulp; wherein, the ash content of the filler is controlled at 8%. Additionally, for the papermaking requirements of playing card paper, retention aids can be added according to actual needs. It should be noted that in any embodiment of this application, the addition of retention aids can be selected according to actual papermaking needs, or retention aids can be omitted.

[0065] Step S200: The mixed slurry is purified and deslag removed to obtain the pre-slurry.

[0066] Step S301: First, mix the uncooked cationic starch with the hydrophobic modified starch, then add water to disperse the mixture to obtain a starch slurry. Add the starch slurry and a dry strength agent to the pre-slurry to obtain the original slurry. The solid content of the starch slurry is controlled at 30%, the oven-dry weight of the starch slurry is set at 45 kg, and the dispersion ratio is 8:1, that is, eight parts of uncooked cationic starch and one part of hydrophobic modified starch. The amount of dry strength agent added is 15 kg / t of paper.

[0067] Step S400: The raw pulp is screened, then wire-fed, and finally dried.

[0068] S500 undergoes surface sizing treatment, followed by secondary drying to obtain semi-base paper. The semi-base paper is then coated externally to obtain the finished base paper.

[0069] The external coating process includes applying a primer, a top coat, and a backing adhesive. Specifically, the total coating weight of the primer and top coat is controlled at 23 g / m². 2 The coating comprises 80 parts ultrafine calcium carbonate, 20 parts ultrafine kaolin with a 2μm particle content of over 98%, 10 parts SBL latex, and 2 parts WEB latex, with a solid content of 66-68%. The application rate for backside sizing is 1.5-2.0 g / m². 2 .

[0070] Furthermore, the finished base paper obtained by following the above steps has a basis weight of 120 g / m². 2 The thickness is 150-155 μm. After subsequent supercalendering and finishing, its basis weight is controlled to be 145 g / m³. 2 It has a thickness of 148-152μm, a gloss of 40-50%, and an interlayer bonding strength of 530-600J / m. 2 This allows us to obtain playing card paper with high interlayer bonding strength and high folding resistance.

[0071] In yet another embodiment of this application, the provided production method includes the following steps:

[0072] Step S01 involves processing the long-fiber wood pulp and short-fiber wood pulp separately through processes such as crushing, screening, dispersion, bleaching, and refining to obtain long-fiber pulp and short-fiber pulp respectively. The long-fiber wood pulp is made from softwood pulp, and the short-fiber wood pulp is made from hardwood pulp, with a ratio of softwood pulp to hardwood pulp of 25:75. The freeness of the long-fiber pulp is controlled at 350 ml, and the freeness of the short-fiber pulp is controlled at 360 ml.

[0073] In step S100, wood pulp, calcium carbonate filler, cooked cationic starch, and sizing agent are mixed to obtain a mixed pulp; wherein, the ash content of the filler is controlled at 8%. Additionally, for the papermaking requirements of playing card paper, retention aids can be added according to actual needs. It should be noted that in any embodiment of this application, the addition of retention aids can be selected according to actual papermaking needs, or retention aids can be omitted.

[0074] Step S200: The mixed slurry is purified and deslag removed to obtain the pre-slurry.

[0075] Step S301: First, mix the uncooked cationic starch with the hydrophobic modified starch, then add water to disperse the mixture to obtain a starch slurry. Add the starch slurry and a dry strength agent to the pre-slurry to obtain the original slurry. The solid content of the starch slurry is controlled at 30%, the oven-dry weight of the starch slurry is set at 52 kg, and the dispersion ratio is 8:1, that is, eight parts of uncooked cationic starch and one part of hydrophobic modified starch. The amount of dry strength agent added is 15 kg / t of paper.

[0076] Step S400: The raw pulp is screened, then wire-fed, and finally dried.

[0077] S500 undergoes surface sizing treatment, followed by secondary drying to obtain semi-base paper. The semi-base paper is then coated externally to obtain the finished base paper.

[0078] The external coating process includes applying a primer, a top coat, and a backing adhesive. Specifically, the total coating weight of the primer and top coat is controlled at 23 g / m². 2 The coating comprises 80 parts ultrafine calcium carbonate, 20 parts ultrafine kaolin with a 2μm particle content of over 98%, 10 parts SBL latex, and 2 parts WEB latex, with a solid content of 66-68%. The application rate for backside sizing is 1.5-2.0 g / m². 2 .

[0079] Furthermore, the finished base paper obtained by following the above steps has a basis weight of 125 g / m². 2 The thickness is 150-160 μm. After subsequent supercalendering and finishing, its basis weight is controlled to be 150 g / m³. 2It has a thickness of 150-155μm, a gloss of 40-50%, and an interlayer bonding strength of 530-600J / m. 2 This allows us to obtain playing card paper with high interlayer bonding strength and high folding resistance.

[0080] In another embodiment of this application, the provided production method includes the following steps:

[0081] Step S01 involves processing the long-fiber wood pulp and short-fiber wood pulp in the pulp with processes such as crushing, screening, dispersion, bleaching, and refining to obtain long-fiber pulp and short-fiber pulp respectively; wherein, the long-fiber wood pulp is selected from softwood pulp and the short-fiber wood pulp is selected from hardwood pulp, and the ratio of softwood pulp to hardwood pulp is 30:70; the freeness of the long-fiber pulp is controlled at 350ml and the freeness of the short-fiber pulp is controlled at 360ml.

[0082] In step S100, wood pulp, calcium carbonate filler, cooked cationic starch, and sizing agent are mixed to obtain a mixed pulp; wherein the ash content of the filler is controlled at 10%. Additionally, for the papermaking requirements of playing card paper, retention aids can be added according to actual needs. It should be noted that in any embodiment of this application, the addition of retention aids can be selected according to actual papermaking needs, or retention aids can be omitted.

[0083] Step S200: The mixed slurry is purified and deslag removed to obtain the pre-slurry.

[0084] Step S301: First, mix the uncooked cationic starch with the hydrophobic modified starch, then add water to disperse the mixture to obtain a starch slurry. Add the starch slurry and a dry strength agent to the pre-slurry to obtain the original slurry. The solid content of the starch slurry is controlled at 30%, the oven-dry weight of the starch slurry is set at 50.6 kg, and the dispersion ratio is 8:1, that is, eight parts of uncooked cationic starch and one part of hydrophobic modified starch. The amount of dry strength agent added is 20 kg / t of paper.

[0085] Step S400: The raw pulp is screened, then wire-fed, and finally dried.

[0086] S500 undergoes surface sizing treatment, followed by secondary drying to obtain semi-base paper. The semi-base paper is then coated externally to obtain the finished base paper.

[0087] The external coating process includes applying a primer, a top coat, and a backing adhesive. Specifically, the total coating weight of the primer and top coat is controlled at 25 g / m². 2The coating comprises 80 parts ultrafine calcium carbonate, 20 parts ultrafine kaolin with a 2μm particle content of over 98%, 10 parts SBL latex, and 2 parts WEB latex, with a solid content of 66-68%. The application rate for backside sizing is 1.5-2.0 g / m². 2 .

[0088] Furthermore, the finished base paper obtained by following the above steps has a basis weight of 132 g / m². 2 The thickness is 157-162 μm. After subsequent supercalendering and finishing, its basis weight is controlled to be 160 g / m³. 2 It has a thickness of 155-160μm, a gloss of 40-50%, and an interlayer bonding strength of 530-600J / m. 2 This allows us to obtain playing card paper with high interlayer bonding strength and high folding resistance.

[0089] In another embodiment of this example, a production system applying the above-described production method is provided, as shown in the attached figure. Figure 5 As shown, it includes the following connected sequentially:

[0090] Mixing tank 10: Connected to the output ends of long-fiber wood pulp (LBKP) and short-fiber wood pulp (NBKP) respectively, used to mix long-fiber wood pulp and short-fiber wood pulp, and to add calcium carbonate filler;

[0091] Mechanical box 20: Connected to a mechanism for cooking cationic starch, used to receive the slurry output from the mixing box 10 and add the cooked cationic starch inside;

[0092] First flushing pump 30: It is located between the machine box 20 and the white water tank 40, and a sizing agent (AKD) addition end can be added between the machine box 20 and the first flushing pump 30 for adding sizing agent; the purpose of this setting is to accelerate the mixing degree of the aforementioned additives by oscillating the pulp through the pumping process of the flushing pump itself, so that the added cooked cationic starch and sizing agent can be fully mixed and act, thereby accelerating the forming of pulp.

[0093] White water tank 40: Used to buffer the aforementioned slurry, allow it to settle, and buffer the slurry's speed before it is transported to other production stages.

[0094] The second slurry pump 50 is used to pump the slurry in the white water tank 40 to the subsequent purification and slag removal process, and further accelerates the mixing degree of the aforementioned additives by agitating the slurry through the pumping process of the slurry pump itself.

[0095] Conical purifier 60: Connected to a control mechanism 601, used to purify and remove slag from the slurry pumped by the second slurry pump 50;

[0096] The third slurry pump 70 is located between the cone-shaped purifier 60 and an addition end for a starch slurry containing a mixture of uncooked cationic starch and hydrophobically modified starch, as well as an addition end for a dry strength agent GPAM. After mixing the starch slurry and the dry strength agent, the slurry is further agitated by the pumping process of the third slurry pump itself to improve the mixing degree of the aforementioned additives, so that it can be uniformly gelatinized later.

[0097] Pressure screen 80: Used to screen the slurry pumped by the aforementioned third slurry pump 70, making the slurry more uniform and fine.

[0098] Headbox 90: Used for the web forming of pulp, i.e., the final forming and drying work. The drying cylinder in the latter part can dry the pulp layer after web forming, and at the same time gelatinize the uncooked cationic starch, so that it forms a network structure with the larger hydrophobic modified starch particles, thereby improving the strength of the base paper after forming.

[0099] In addition, in this embodiment, a fourth slurry pump 100 can be added between the slurry mixing tank 10 and the mechanical tank 20. Its effect is to help the slurry to be mixed more quickly through its own pumping process.

[0100] This application prepared three sets of finished playing cards using the above-described preparation method as examples, and provides the comparison results of the quality of the examples and the control group as shown in the table below:

[0101] Table 1: Comparison of quality between the example and the control group.

[0102]

[0103] As shown in the table above, this application provides three sets of embodiments, including Embodiment 1, Embodiment 2 and Embodiment 3, and provides a control group. Specifically, playing cards are made by coating and sizing one side of white kraft paper and then further laminating it (using a laminating machine to laminate two, three or more layers). White kraft paper is a commonly used product in the traditional manufacture of playing cards.

[0104] The comparison results clearly show that, compared to playing cards obtained through traditional methods, the quality of the paper (i.e., the finished base paper) in this application—namely, the cohesion, interlayer bonding strength, and folding endurance—is significantly higher than the control group. Furthermore, the playing cards obtained from further processing of this paper also exhibit significantly higher cohesion, interlayer bonding strength, and folding endurance than the control group. Therefore, the technology of this application can effectively improve the cohesion and interlayer bonding strength of the base paper, thereby enhancing its strength and folding endurance.

[0105] 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 producing a folding-resistant base paper, characterized by, The application relates to a production method of a folding-resistant base paper. The method comprises the following steps: The wood pulp, calcium carbonate filler, cooked cationic starch and sizing agent are mixed to obtain mixed pulp; The mixed pulp is purified to remove residues to obtain front pulp; Uncooked cationic starch, hydrophobically modified starch and dry strength agent are added into the front pulp to obtain original pulp; The original pulp is screened, and then is subjected to webbing treatment and drying; The uncooked cationic starch and the hydrophobically modified starch are added before drying, and the uncooked cationic starch is gelatinized by the subsequent drying process, so as to form a network structure with the hydrophobically modified starch; The amount of the uncooked cationic starch is 40-50 kg / t paper, the amount of the hydrophobically modified starch is 5-8 kg / t paper, and the amount of the dry strength agent is 5-20 kg / t paper; The step of adding the uncooked cationic starch, the hydrophobically modified starch and the dry strength agent into the front pulp to obtain the original pulp comprises the following steps: the uncooked cationic starch is mixed with the hydrophobically modified starch, water is added for dispersion after mixing to obtain starch slurry, and the starch slurry and the dry strength agent are added into the front pulp; After the step of drying after the webbing treatment, the following steps are further included: surface sizing treatment is performed, secondary drying is performed after the surface sizing treatment to obtain semi-base paper, and the semi-base paper is subjected to off-machine coating to obtain finished base paper; the step of off-machine coating comprises the following steps: base coating, top coating and back sizing treatment; The wood pulp comprises coniferous wood pulp and broad-leaved wood pulp; 2. The method for producing a folding-resistant base paper according to claim 1, characterized by, The mass percentage of the coniferous wood pulp is 20-30%, the mass percentage of the broad-leaved wood pulp is 70-80%, the mass percentage of the calcium carbonate filler is 6-10%, the amount of the cooked cationic starch is 9-11 kg / t paper, and the amount of the sizing agent is 8.5-11.5 kg / t paper.

3. The method of producing a folding-resistant base paper according to claim 1, characterized by, The coating amount of the base coat is 8-12 g / m 2 The coating amount of the top coat is 10-12 g / m 2 The sizing amount of the back sizing treatment is 1-3 g / m 2 The solid content of the coating used for the base coat and the top coat is 66-68%.

4. The method of producing a folding-resistant base paper according to claim 1, characterized by, The online processing includes: adjusting online flow, controlling paper page ration between 120-123g / m 2 .

5. A buckling-resistant base paper, characterized in that In the step of mixing the uncooked cationic starch with the hydrophobically modified starch, the dispersion ratio range of the uncooked cationic starch to the hydrophobically modified starch is 7.5-9.5:0.5-2, the solid content of the starch slurry is 25-35%, and the absolute dry weight of the starch slurry is 40-52 kg. The folding-resistant base paper is prepared by the production method in any one of the above claims 1-4.

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