Archive paper and manufacturing method thereof

Abstract

The invention discloses archive paper and a manufacturing method thereof, and belongs to the technical field of papermaking. The method comprises the following steps: taking bleached chemical wood pulp as a fiber raw material, wherein the fiber raw material comprises 50-70wt% of bleached softwood pulp and 30-50wt% of bleached hardwood pulp; the fiber raw materials are subjected to auxiliary pulping through cellulase, and the freeness of pulp is controlled to be 280-350 mL; then mixing to obtain mixed slurry; adding auxiliary materials into the mixed slurry, wherein the auxiliary materials comprise cationic starch, a reinforcing agent, a filler, a retention aid and a neutral sizing agent; and carrying out papermaking molding through a net in a neutral range, and carrying out neutral sizing to obtain the archive paper. According to the preparation method, the pulp with relatively good strength is mainly selected, and the processes of neutral sizing and the like are adopted, so that the prepared paper is alkaline innate, and the aging problem caused by paper acidification is reduced to the greatest extent.

Description

Technical Field

[0001] The present invention relates to the technical field of papermaking, and particularly relates to an archival paper and a manufacturing method thereof. Background Art

[0002] Archives are different from general books and materials. They are the true records and vouchers of history. Generally speaking, archives need to be stored for a long time, and some archives need to be stored permanently. Therefore, it is necessary to study various factors that affect the lifespan of archives. Even in the current era when electronic archives and paper archives coexist, paper archives still have irreplaceable functions due to their unique originality, legality, evidentiary nature, and integrity.

[0003] As the main carrier of archives, the quality and durability of paper directly affect the lifespan of archives. During the storage process, irreversible changes gradually occur in the appearance structure and properties of archival paper, namely the phenomenon of "aging"; specifically manifested in aspects such as discoloration, strength decline, and chemical property changes. The reasons for paper aging are complex and often the result of the combined action of certain factors within the paper itself and various external natural factors, such as the durability of the fiber components in the archival paper itself, the acidic hydrolysis of cellulose in the external environment, the photo-aging, thermal-aging of the archival paper, and the aging effect of metal substances on the archival paper. Therefore, it is necessary to improve the papermaking process to enhance the durability of current archival paper. Summary of the Invention

[0004] To solve the existing problems of aging such as yellowing, embrittlement, strength reduction, and chemical property changes of paper within a short time under the influence of the environment, the present invention provides an archival paper and a manufacturing method thereof. The paper product has high strength, good durability, can be used as an archival carrier, etc., and has a relatively low production cost.

[0005] The present invention provides a manufacturing method of archival paper, including the following steps:

[0006] The bleached softwood pulp and the bleached hardwood pulp are respectively subjected to cellulose enzyme-assisted beating, and the freeness of the pulp is respectively controlled at 280 - 350 mL; then they are mixed in proportion to obtain a mixed pulp; the ratio of the bleached softwood pulp to the bleached hardwood pulp is 50 - 70 wt%: 30 - 50 wt%;

[0007] Auxiliary materials are added to the mixed pulp, and the auxiliary materials include cationic starch, strengthening agent, filler, retention aid, and neutral sizing agent; it is formed by wire drawing and sizing within the neutral range to obtain archival paper.

[0008] Preferably, the beating is all carried out by conical refiner grinding, and 0.02 - 0.06 kg / ton of paper of the cellulose enzyme is added before grinding; after grinding, lignin enzyme is also added, and then they are mixed to obtain a mixed pulp.

[0009] Preferably, the filler is calcium carbonate; the retention aid is one or more of bentonite, cationic polyacrylamide and microparticles; the neutral sizing agent is alkenyl succinic anhydride.

[0010] Preferably, 0.1 - 0.2 kg of drainage enzyme per ton of paper is also added before pulping; and / or, the auxiliary materials further include drainage synergist.

[0011] Preferably, the addition amount of the neutral sizing agent is 1 - 2 kg per ton of paper.

[0012] Preferably, the auxiliary materials further include dyes and / or brighteners.

[0013] Preferably, the materials used for neutral sizing include native starch and neutral surface sizing agent.

[0014] Preferably, the dosage of the neutral surface sizing agent is 2 - 5 kg per ton of paper; the neutral surface sizing agent is a mixture of styrene - acrylic polymer sizing agent and water - resistant alkyl ketene dimer sizing agent.

[0015] The present invention provides an archival paper obtained by using the manufacturing method described above, and the pH value of the finished product is 8 - 8.5.

[0016] Preferably, the basis weight of the archival paper is 70 - 100 g / m 2 , and the antioxidant kappa number is 0.6 - 0.9.

[0017] Good - quality paper can resist chemical reactions caused by its own impurities or adverse atmospheric conditions such as light, heat, harmful gases, etc., delay the degree of natural aging, and extend the preservation period. The quality of paper mainly depends on the quality of the plant fiber raw materials used and the papermaking process.

[0018] Compared with the prior art, the technology of the present invention selects bleached chemical wood pulp as the papermaking stock, among which 50 - 70 wt% of bleached softwood pulp is selected and matched with 30 - 50 wt% of bleached hardwood pulp for papermaking; and respectively, the addition of beating enzyme (cellulase) is used to assist beating, and the freeness of the stock is controlled to be 280 - 350 mL respectively. After the stock is ground, a fiber treatment agent (ligninase) can also be added to further remove the residual lignin in the pulp, and then the paper is formed by wire - drawing in the neutral range and an archival paper is obtained through neutral sizing. The present invention mainly selects a stock with better strength and adopts processes such as neutral sizing, so that the paper obtained can be inherently alkaline, and the aging problem caused by paper acidification is reduced to the greatest extent; in some embodiments, the pH value of the archival paper can be 8.2, the alkali reserve is 2.4 mol / kg, and the antioxidant (kappa number) effect reaches 0.7. Brief Description of the Drawings

[0019] Figure 1 Process flow chart of the method for some embodiments of the present invention. Detailed implementation manners

[0020] In order to more clearly understand the technical features, objectives, and effects of the present invention, the technical solutions of the present invention will be described in detail below with reference to specific embodiments. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0021] The present invention provides a method for manufacturing archival paper, comprising the following steps:

[0022] The bleached softwood pulp and the bleached hardwood pulp are respectively subjected to cellulose enzyme-assisted beating, and the freeness of the pulp is respectively controlled at 280 - 350 mL; then they are mixed in proportion to obtain a mixed pulp; the ratio of the bleached softwood pulp to the bleached hardwood pulp is 50 - 70 wt%: 30 - 50 wt%;

[0023] Auxiliary materials are added to the mixed pulp, and the auxiliary materials include cationic starch, strengthening agent, filler, retention aid, and neutral sizing agent; it is formed by wire drawing and papermaking in the neutral range, and archival paper is obtained through neutral sizing.

[0024] The paper product obtained by the method of the present invention has high strength, good durability, low production cost, and can be used as an archival carrier, etc.

[0025] See Figure 1 , Figure 1 is the process flow chart of some embodiments of the present invention. After the softwood pulp fibers and hardwood pulp fibers are respectively ground, they are mixed evenly according to the mass ratio of 50% - 70% of the softwood pulp fibers and 30% - 50% of the hardwood pulp fibers. Cationic starch, strengthening agent, dye, brightening agent, calcium carbonate filler, ASA sizing agent, retention and drainage aid, etc. can be added, and a mixed pulp that can be sent to the paper machine is obtained. The pulp is sent to the wire section of the paper machine through a headbox, dehydrated, pressed in the press section, pre-dried, surface-sized, post-dried, calendered and wound up to obtain the finished paper product.

[0026] Paper acidification is the most important reason for the aging and shortened lifespan of paper archives. During the acidification process of paper, the length of cellulose changes, and at the same time, oxidative degradation occurs, and the paper gradually turns yellow and brittle. Therefore, to prevent the paper from turning yellow and brittle, reduce the aging speed, and extend the lifespan of the archives, acidification must be prevented first.

[0027] The acid in the paper mainly comes from the acidic additives retained during the papermaking process and the acidic substances in the environment. The present invention adopts a papermaking process in the neutral range (neutral to slightly alkaline), with neutral sizing, and the pH value of the finished product can reach 8 - 8.5, and the paper is inherently alkaline.

[0028] The main component in paper is cellulose, which is a linear high-molecular compound. The longer the fiber, the easier the cellulose molecules are intertwined, showing high physical properties of the paper. On the contrary, the strength of the paper will also decrease, and the appearance is brittle. After the paper is acidified, the internal structure changes and the fiber length becomes shorter. The cellulose in paper is usually very stable. The main reason for the reduction in its length is that the cellulose undergoes a hydrolysis reaction under the action of an acid catalyst, resulting in a decrease in length. When the fiber length becomes shorter, the interweaving force between the fibers decreases. Observed on the surface, the strength of the paper decreases and it becomes significantly brittle.

[0029] In the embodiments of the present invention, long-fiber softwood pulp and hardwood pulp are used as raw materials for preparing archival paper. The raw materials have good quality, and the paper made by them has high strength, which is beneficial for long-term preservation.

[0030] Specifically, for the selection of fiber raw materials:

[0031] In the national standard 24422 "Requirements for the Durability and Endurance of Information and Document Archival Paper", it is required that archival paper should be made by sizing a certain amount of cotton fiber, cotton linters, hemp fiber, bast fiber or their mixtures with fully bleached chemical wood pulp. Since cotton fiber is an essential material for people's lives and is mainly used in the textile industry, using it as a raw material for papermaking has a high cost. And the production capacity of hemp and bast fibers in the market is relatively low, which is not enough to meet mass production. Therefore, in the embodiments of the present invention, the commonly used fully bleached chemical wood pulp in the current market is selected as the pulp for archival paper, which not only meets the actual production but also meets the strength requirements of archival paper and reduces the production cost.

[0032] Comparing the fiber raw materials of papermaking wood, the fiber length of softwood (2 - 5 mm) is longer than that of hardwood (0.7 - 2 mm), and the strength is better; the fiber length of pine softwood is longer than that of fir softwood. Therefore, pine softwood is preferably selected as one of the raw materials for archival paper and is used in combination with hardwood pulp for papermaking. In this application, the fiber raw material selects long-fiber softwood pulp and is used in combination with hardwood pulp for papermaking. The longer the fiber length, the higher the folding endurance of the paper, which is helpful for the back-and-forth folding of the paper.

[0033] In the pulp preparation step of the embodiments of the present invention, the softwood pulp can be commercially available dry pulp boards. After being pulped, it is mixed and stirred evenly with hardwood pulp according to the pulp ratio to make a mixed pulp. The hardwood pulp can be self-produced hardwood bleached chemical pulp. After the hardwood raw material wood chips are prepared, cooked by the alkaline sulfate method, washed, screened and purified, oxygen delignified, and chlorine dioxide bleached, they are transported to the paper machine through pipelines and mixed and stirred evenly with softwood pulp according to the pulp ratio to make a mixed pulp. The present invention has no special restrictions on the bleach brightness of softwood pulp and hardwood pulp, etc., and it can be above 85% ISO. Specifically, the ISO brightness of softwood pulp is 89 - 90%, and the ISO brightness of hardwood pulp is 88 - 89%.

[0034] The beating treatment of the raw material pulp fibers in the embodiments of the present invention may include: after the softwood pulp is broken, it is desanded by a high-concentration desander, sent to the pre-grinding tank, preferably ground by a conical refiner, and then sent to the post-grinding (pulp) tank. Since it is difficult to beat softwood pulp, after the above dry pulp board is broken, beating enzyme is added to the pre-grinding (pulp) tank. The beating enzyme is cellulase (the preferred addition amount can be 0.02 - 0.06 kg / ton of paper). It can "react" with cellulose and hemicellulose in the cell wall, promote the relaxation and softening of the cell wall structure, increase permeability, promote swelling, reduce the cohesion of fibers, make the fibers softer, and through the mechanical force of beating, the fiber cell wall is stratified and collapsed, accelerating the destruction of the cell wall and fibrillation, reducing the beating energy consumption, enabling more bonding points between fibers, and improving the strength.

[0035] After that, the embodiments of the present invention can be ground by a three-stage conical refiner. After grinding, it enters the post-grinding pulp tank, where a fiber treatment agent is added. The fiber treatment agent is ligninase, and the preferred addition amount is 0.5 - 1 kg / ton of paper. It can decompose and treat the residual lignin in the softwood pulp and increase the α-cellulose content.

[0036] For the beating treatment of hardwood bleached chemical pulp, its process is basically the same as that of softwood pulp; first, cellulase is added to assist in beating (grinding by a conical refiner), and after grinding, a fiber treatment agent (ligninase) is added to further remove the residual lignin in the pulp and control the freeness of the pulp to be 280 - 350 mL.

[0037] To ensure the various strengths of the archival paper and the dehydration of the pulp, the freeness of the pulp is controlled within 280 - 350 ml. Since the fibers are relatively long, to ensure dehydration and operation during the production of archival paper, a water-filtering enzyme that helps with dehydration is preferably added to the pre-grinding tank (the addition amount can be 0.1 - 0.2 kg / ton of paper). The water-filtering enzyme is a special chemical for improving water filtration in the papermaking process when the pulp dehydration is difficult. The water-filtering enzyme can enhance the dehydration of the pulp. It is a mixed enzyme, and its components are a mixture of cellulase, hemicellulase, pectinase, and lipase. Among them, the beating enzyme, water-filtering enzyme, etc. used are all commercially available corresponding products.

[0038] The hardwood pulp described in the embodiments of the present invention is transported to the pre-washing pulp tower through a pipeline. After being squeezed by a double-roll press, it can be diluted with white water and sent to the post-washing pulp tower, and then transported to the pre-grinding tank, preferably ground by a conical refiner, and then sent to the post-grinding pulp tank. The fiber treatment agent described above is added to the post-grinding pulp tank. The fiber treatment agent can wrap and react with non-fiber substances in the pulp, reduce the lignin content, reduce the yellowing of the paper, and further improve the strength of the pulp.

[0039] In some embodiments of the present invention, the mixed pulp entering the mixed pulp tank is as follows: by weight percentage, softwood pulp fibers are 50%-70%, and hardwood pulp fibers are 30%-50%. For example, the weight percentage of softwood pulp to hardwood pulp can be 50%:50%, 60%:40%, 70%:30%. The softwood pulp and hardwood pulp are preferably beaten by a three-stage conical refiner respectively, and the freeness is controlled at 280-350 ml. The present invention preferably uses a ligninase fiber modifier to treat the chemical pulp, further wrapping and reacting the residual lignin in the pulp, which can reduce the yellowing and aging phenomenon of the paper caused by the chromophore groups in the lignin.

[0040] In the specific embodiments of the present invention, the slurries are ground respectively and then mixed evenly in proportion, enter the paper machine pulp tank, and then successively add fillers, cationic starch, strengthening agents, dyes, brighteners, drainage aids, retention and drainage aids, ASA sizing agents to obtain a mixed pulp that can be used on the paper machine; the pulp is formed on the wire through a headbox, dehydrated, pressed, pre-dried, surface-sized, post-dried, calendered and wound to obtain the finished product.

[0041] Among the auxiliary materials added in the embodiments of the present invention, the main function of the cationic starch is to assist in retention and drainage and improve the internal bonding strength of the formed paper. Specifically, the degree of substitution of the cationic starch is ≥0.032, the fineness is ≥99.0% (325 mesh, wet sieve), the pH (33% slurry, 25°C) is 5-8, and the ISO whiteness is ≥85%. The main function of the strengthening agent is to improve the tensile and tear strength of the paper. The strengthening agent is preferably amphoteric polyacrylamide. For example, its solid content is 20±1%, and the room temperature viscosity can be 5000-12000 mPa·s, further 8000-12000 mPa·s; the added filler is preferably calcium carbonate, which can improve the opacity and whiteness of the paper, reduce the printing through phenomenon of the paper, improve the smoothness and evenness of the paper, save fiber usage, and reduce production costs. Specifically, the filler is ground calcium carbonate, the whiteness is ≥93%, 60±1% of the particle size is ≤2μm, the 45μm sieve residue is ≤10 ppm, the 20μm sieve residue is ≤300 ppm, the solid content is 28±0.5%, the room temperature viscosity is ≤200 cps, and the PH is 8.5-10.5. Specifically, relative to each ton of paper, the dosage ratio of calcium carbonate filler is 5%-10%, the cationic starch can be 4-8 kg, and the strengthening agent can be 5-8 kg.

[0042] After passing through a Lobe mixer, conventional dyes such as blue dye and purple dye can be added in the embodiments of the present invention, and optionally a brightener can be added for color adjustment. The brightener is preferably sodium diphenylstyryl biphenyl disulfonate; in some embodiments, the dosage per ton of paper is: 30-60 g of blue dye and purple dye, and 4-8 kg of brightener.

[0043] Due to the low ash content and high proportion of long fibers, it is not easy to dehydrate during the papermaking process. As an option, a drainage enzyme is added to dissolve the soluble colloidal substances in the pulp and open the drainage channels; a drainage enhancer is added to connect cellulose molecules to form a three-dimensional network structure, further accelerating dehydration and improving the bonding strength between fibers, thereby enhancing the strength of the archival paper. Among them, in the embodiments of the present invention, after passing through the desander and pressure screen, it is preferred to add the drainage enhancer at the inlet of the first stage pulp pump (the addition amount is 1-3 kg / ton of paper); since the raw materials for preparing archival paper are fibers with relatively long lengths, the pulp dehydration is relatively difficult. Adding the drainage enhancer here can improve the drainage performance and the strength of the paper. The drainage enhancer is an amphoteric polymer network polymer, and its components are organic composite aldehydes, polyacrylamide, chitosan, and polycarboxylic acid. The drainage enhancer can directly form an electrostatic bridging effect with fibers and other organic polymers, forming a network structure with them, increasing the drainage channels in the pulp system, and enhancing the dehydration rate of the pulp; through the formation of ionic bonds between cations and anions on the fibers, it can be adsorbed onto the pulp fibers, and the amide groups combine with the hydroxyl groups on the fibers to form hydrogen bonds, enhancing the bonding strength between the fibers.

[0044] Before the headbox, in the preferred embodiments of the present invention, a ternary retention and drainage aid can be added, which includes bentonite, microparticles, and cationic polyacrylamide (CPAM), facilitating the retention of chemicals and the drainage of the pulp; the ternary retention and drainage aid (CPAM / microparticles / bentonite) is added according to actual conditions. Additionally, it is preferred to add an alkenyl succinic anhydride (ASA) internal sizing agent (a neutral sizing agent), and its addition amount is preferably 1-2 kg / ton of paper, improving the liquid repellency of the formed paper and ensuring that the printed paper does not show traces or bleeding of ink.

[0045] In the embodiments of the present invention, gravity and vacuum dehydration, pressing, pre-drying, sizing, post-drying, calendering, and coiling are carried out in the forming section. Among them, dehydration, pressing, and drying are all conventional processes; the materials used in the sizing stage include native starch, neutral surface sizing agent, surface salt, and surface brightening agent. The neutral surface sizing agent is a mixture of styrene-acrylic polymer sizing agent (SAE sizing agent, improving surface strength) and water-resistant alkyl ketene dimer sizing agent (neutral AKD sizing agent, improving surface water resistance); the surface salt is calcium chloride salt that can improve the vividness of printing colors. The addition amount of the sizing materials is 1 g / m 2 / side, where the addition amount of the original starch is 20 - 30 kg / t of paper, and the addition amount of the neutral surface sizing agent is 2 - 5 kg / ton of paper, so that the archival paper has both liquid repellency and no ink bleeding during printing, and also ensures the surface strength and no linting and powdering during printing. The surface is sized with calcium chloride salt to improve the ink printing density and the color vividness after printing. The presence of calcium chloride can reduce the electrostatic attraction between fibers, prevent the generation of static electricity during the drying process of the paper and when passing through an inkjet printer, and the addition amount is 2 - 3 kg / t of paper / side. To ensure the whiteness and brightness of the finished paper, a surface brightening agent is added during the sizing stage. The surface brightening agent is sodium diphenylstyryl biphenyl hexasulfonate, and the addition amount is 2 - 4 kg / t of paper.

[0046] The entire papermaking process of the embodiment of the present invention is neutral papermaking, which avoids the entry of acidic substances into the system and prevents the acidification and aging of archival paper.

[0047] Correspondingly, the present invention provides an archival paper obtained by the manufacturing method described above, and the pH value of the finished product is 8 - 8.5. The basis weight of the archival paper can be 70 - 100 g / m 2 , further 80 g / m 2 , 100 g / m 2 etc., and its antioxidant Kappa number can be 0.6 - 0.9.

[0048] In a specific embodiment, the basis weight of the archival paper prepared by the present invention is 80 g / m 2 , the moisture content is 4.2%, the CIE whiteness is 163%, the tearing strength is 531 mN longitudinally and 542 mN transversely, the pH value is 8.2, the alkali retention is 2.4 mol / kg, and the antioxidant (Kappa number) is 0.7.

[0049] To further understand the present invention, the present invention will be described in detail below in conjunction with embodiments. The protection scope of the present invention is not limited by the following embodiments. In the embodiments, all the original reagents and materials can be obtained commercially, and the experimental methods without specific experimental conditions are the conventional methods and conditions well-known in the art.

[0050] The whiteness of the used pulp is 88 - 90% ISO; the strengthening agent is amphoteric polyacrylamide, with a solid content of 20 ± 1% and a viscosity of 10000 - 12000 mPa·s; the degree of substitution of cationic starch is 0.032, the fineness is ≥99.0% (325 mesh, wet sieve), the pH (33% slurry, 25 °C) is 5 - 8, and the ISO whiteness is 85%; the brightening agent is sodium diphenylstyryl biphenyl disulfonate; the drainage aid is an amphoteric polymer network polymer, and its components are organic compound aldehydes and polyacrylamide, chitosan, and polycarboxylic acid, which are water-soluble substances, the pH is 6 - 8, and the appearance is a colorless to amber liquid.

[0051] Example 1

[0052] 1. Pulping step: The softwood fiber pulp board (purchased externally) is disintegrated in a pulper; the disintegrated softwood pulp enters the pulp pond before the softwood pulp grinder, where 70 ml / min of beating enzyme is added. After the beating enzyme (cellulase) fully reacts with the fibers, it enters the grinder. The freeness of the softwood pulp is controlled at 330 ± 20 ml to reduce the cutting of softwood fibers and maintain the advantage of fiber length. After passing through the grinder, it enters the pulp pond after grinding, where 1 kg / t of pulp fiber treatment agent (ligninase) is added to decompose the residual lignin in the pulp;

[0053] The hardwood pulp is transported by pipeline from the pulp line to the pulp tower before paper machine washing. After passing through the double-roll press, it is diluted with white water and sent to the pulp tower after washing, and then transported to the pulp pond before grinding. Here, 50 ml / min of beating enzyme is added. After the beating enzyme fully reacts with the fibers, it enters the grinder. The freeness of the hardwood pulp is controlled at 300 ± 20 ml to fluff the surface of the hardwood pulp fibers, fibrillation, increase the hydrogen bond binding between fibers, and improve fiber binding force. After passing through the grinder, it enters the pulp pond after grinding, where 1 kg / t of pulp fiber treatment agent is added to decompose the residual lignin in the pulp.

[0054] 2. Pulp blending step: The ground pulp is mixed evenly with 50% softwood pulp and 50% hardwood pulp by weight percentage to obtain a mixed pulp;

[0055] 3. Chemical addition step: 10% calcium carbonate filler, 4 kg of cationic starch, 5 kg of strengthening agent, 40 g of blue dye, 60 g of purple dye, and 6 kg of brightening agent are added to the mixed pulp. It enters the desander and pressure screen. 1 kg / t of paper of filter water efficiency enhancer is added at the inlet of the first-stage pulp pump. Before the headbox, a ternary retention and drainage aid (3 kg / t of paper of bentonite, 0.3 kg / t of paper of microparticles, 0.3 kg / t of paper of CPAM) and 1.2 kg / t of paper of ASA internal sizing agent are added using the Chuangjie system.

[0056] 4. Forming and papermaking: The paper stock is sent to the headbox, and the forming consistency is 1.0%. To ensure the transverse strength, the pulp-to-wire speed ratio is 1.045. After sizing, it undergoes dewatering and forming in the wire section, dewatering in the press section, and pre-drying before entering the sizing section.

[0057] 5. Sizing: The sizing agents are native starch, a mixed surface sizing agent of AKD water-resistant type + SAE strengthening type, and surface brightening agent. 25 kg / t of paper of native starch, 3 kg / t of paper per side of surface sizing agent, and 3 kg / t of paper per side of surface brightening agent.

[0058] 6. After sizing, it enters post-drying, calendering by a calender, coiling, and rewinding, and then goes to the finishing section to be cut into the sizes required by customers.

[0059] According to the above embodiments, the prepared archival paper has a basis weight of 80 g / m 2, moisture content 4.2%, CIE whiteness 163%, tearing strength 382 mN longitudinally and 424 mN transversely, folding endurance 95 times longitudinally and 101 times transversely, pH value of the water extract of the paper 8.2, alkali retention 2.5 mol / kg, antioxidant Kappa number 0.8.

[0060] Example 2:

[0061] 1. Pulping step: The softwood fiber pulp board is disintegrated in a pulper; the disintegrated softwood pulp enters the pulp chest before the softwood pulp grinder, where 70 ml / min of beating enzyme is added. After the beating enzyme fully reacts with the fibers, it enters the grinder. The freeness of the softwood pulp is controlled at 330 ± 20 ml to reduce the cutting of softwood fibers and maintain the advantage of fiber length. After passing through the grinder, it enters the pulp chest after grinding, where 2 kg / t of pulp fiber treatment agent is added to decompose the residual lignin in the pulp;

[0062] The hardwood pulp is transported to the pulp tower before washing of the paper machine through a pipeline by the pulp line. After passing through a double-roll press, it is diluted with white water and sent to the pulp tower after washing, and then transported to the pulp chest before grinding. Here, 50 ml / min of beating enzyme is added. After the beating enzyme fully reacts with the fibers, it enters the grinder. The freeness of the hardwood pulp is controlled at 300 ± 20 ml to make the surface of the hardwood pulp fibers fuzz, fibrillate, increase the hydrogen bond binding between fibers, and improve fiber binding force. After passing through the grinder, it enters the pulp chest after grinding, where 1 kg / t of pulp fiber treatment agent is added to decompose the residual lignin in the pulp.

[0063] 2. Pulp blending step: The ground pulp is mixed evenly with 60% softwood pulp and 40% hardwood pulp by weight percentage to obtain a mixed pulp;

[0064] 3. Chemical addition step: 8% calcium carbonate filler, 4 kg of cationic starch, 6 kg of strengthening agent, 40 g of blue dye, 60 g of purple dye, and 6 kg of brightening agent are added to the mixed pulp. It enters a desander and a pressure screen. 1.5 kg / t of paper of a filter water efficiency enhancer is added at the inlet of the first-stage pulp pump. Before the headbox, a ternary retention and drainage aid (3 kg / t of paper of bentonite, 0.3 kg / t of paper of microparticles, 0.3 kg / t of paper of CPAM) and 1.2 kg / t of paper of ASA internal sizing agent are added using a Chuangjie system.

[0065] 4. Forming and papermaking: The stock is sent to the headbox, and the forming consistency is 1.0%. To ensure the transverse strength, the pulp-to-wire speed ratio is 1.045. After sizing, it undergoes dewatering and forming in the wire section, dewatering in the press section, and enters the sizing section after pre-drying

[0066] 5. Sizing: The sizing agents are native starch, a mixed surface sizing agent of AKD water-repellent type + SAE strengthening type, and a surface brightening agent. 25 kg / t of paper of native starch, 3 kg / t of paper per side of the surface sizing agent, and 3 kg / t of paper per side of the surface brightening agent.

[0067] 6. After sizing, it enters the post-drying process, is calendered by a calender, curled, and rewound, and then cut into the sizes required by customers at the finishing section.

[0068] According to the above embodiments, the prepared archival paper has a basis weight of 80 g / m 2 , a moisture content of 4.2%, a CIE whiteness of 163%, a tear strength of 401 mN longitudinally and 462 mN transversely, a folding endurance of 101 times longitudinally and 123 times transversely, a pH value of 8.3 for the water extract of the paper, an alkali reserve of 2.8 mol / kg, and an antioxidant Kappa number of 0.6.

[0069] Example 3:

[0070] 1. Pulping step: The softwood fiber pulp board is disintegrated in a pulper; the disintegrated softwood pulp enters the softwood pulp pond before grinding. Here, 70 ml / min of beating enzyme is added. After the beating enzyme reacts fully with the fibers, it enters the refiner. The freeness of the softwood pulp is controlled at 330 ± 20 ml to reduce the cutting of softwood fibers and maintain the advantage of fiber length. After passing through the refiner, it enters the pulp pond after grinding. Here, 1 kg / t of pulp fiber treatment agent is added to decompose the residual lignin in the pulp;

[0071] The hardwood pulp is transported to the pulp tower before washing of the paper machine through a pipeline by the pulp line. After passing through a double-roll press, it is diluted with white water and sent to the pulp tower after washing, and then transported to the pond before grinding. Here, 50 ml / min of beating enzyme is added. After the beating enzyme reacts fully with the fibers, it enters the refiner. The freeness of the hardwood pulp is controlled at 300 ± 20 ml to make the surface of the hardwood pulp fibers fuzz, fibrillate, increase the hydrogen bond binding between fibers, and improve the fiber bonding strength. After passing through the refiner, it enters the pulp pond after grinding. Here, 1 kg / t of pulp fiber treatment agent is added to decompose the residual lignin in the pulp.

[0072] 2. Pulp blending step: The ground pulp is mixed evenly with 70% softwood pulp and 30% hardwood pulp by weight percentage to obtain a mixed pulp;

[0073] 3. Chemical addition step: 8% calcium carbonate filler, 4 kg of cationic starch, 6 kg of strengthening agent, 40 g of blue dye, 60 g of purple dye, and 6 kg of brightening agent are added to the mixed pulp. It enters the desander and pressure screen. 1.5 kg / t of paper of a filter water efficiency enhancer is added at the inlet of the first-stage pulp pump. Before the headbox, a ternary retention and drainage aid (3 kg / t of paper of bentonite, 0.3 kg / t of paper of microparticles, 0.3 kg / t of paper of CPAM) and 1.2 kg / t of paper of ASA internal sizing agent are added using the Chuangjie system.

[0074] 4. Forming and papermaking: The stock is sent to the headbox, and the forming consistency is 1.0%. To ensure the transverse strength, the pulp-to-wire speed ratio is 1.045. After sizing, it is dehydrated and formed by the wire section, dehydrated by the press section, and then enters the sizing section after pre-drying

[0075] 5. Sizing: The sizing agents are native starch, AKD water - resistant + SAE strengthening mixed surface sizing agent, and surface brightening agent. The dosage of native starch is 25 kg / t of paper, the surface sizing agent is 3 kg / t of paper per side, and the surface brightening agent is 3 kg / t of paper per side.

[0076] 6. After sizing, it enters post - drying, calendaring by a calender, coiling, and rewinding, and then is cut into the sizes required by customers in the finishing section.

[0077] According to the above - mentioned examples, the prepared archival paper has a basis weight of 80 g / m 2 , a moisture content of 4.2%, a CIE whiteness of 163%, a tearing strength of 411 mN longitudinally and 471 mN transversely, a folding endurance of 109 times longitudinally and 140 times transversely, a pH value of 8.4 for the water - extractable liquid of the paper, an alkali retention of 2.6 mol / kg, and an antioxidant kappa number of 0.7.

[0078] Comparative example:

[0079] An archival paper is formed by paper machine molding, pressing, drying, and calendering finishing from mixed pulp and auxiliary materials. Among them, the composition of the mixed pulp by mass percentage is: 85% of alkaline bleached softwood pulp fibers, 10% of cotton pulp fibers, and 5% of aramid fibers. The alkaline bleached softwood pulp fibers are softwood pulp fibers after alkaline treatment.

[0080] The composition of the auxiliary materials (by mass percentage of each auxiliary material component to the absolutely dry mixed pulp) is: 15% of filler, which is calcium carbonate; 0.2% of sizing agent, which is AKD; 0.03% of brightening agent, which is diphenylstyrylbiphenyl disulfonate; and the dosage of the retention aid is 0.02%, which is polyacrylamide.

[0081] The above - mentioned archival paper is prepared according to the following steps:

[0082] 1) Treatment of alkaline bleached softwood pulp fibers: Add 2000 kg of softwood pulp and water into a 5 m 3 stainless - steel storage tank to form a suspension with a mass concentration of 2.0%. Add 30 L of NaOH solution with a concentration of 200 g / L, react and treat at 30 ± 2 °C for 450 min, centrifuge and separate at 2500 rpm for 20 min to obtain softwood pulp fibers, then add water to dilute and form a softwood pulp fiber suspension with a mass concentration of 2.0%. Add sulfuric acid to adjust the pH = 3 and treat for 30 min at 35 ± 2 °C, then centrifuge and wash to separate and obtain alkaline bleached softwood pulp fibers.

[0083] 2) Weigh the raw materials: Weigh each raw material according to the above - mentioned ratio.

[0084] 3) Pulp the alkaline bleached softwood pulp fibers and cotton pulp fibers separately to obtain alkaline bleached softwood pulp slurry and cotton pulp slurry. Then, prepare 9000 kg of mixed slurry by mixing the alkaline bleached softwood pulp slurry, cotton pulp slurry and un-pulped aramid fibers. The beating degree of the alkaline bleached softwood pulp slurry is 38.5°SR; the beating degree of the cotton pulp slurry is 40.5°SR. Use a high-frequency refiner to refine the mixed slurry.

[0085] 4) Paper stock preparation: Add 1350 kg of calcium carbonate filler to the refined mixed slurry, then add 18 kg of AKD sizing agent, 2.7 kg of brightening agent diphenylstyryl biphenyl disulfonate and 1.8 kg of retention aid polyacrylamide in sequence to prepare the paper stock.

[0086] 5) Forming and papermaking: Feed the paper stock into the headbox, then control the consistency of the paper stock on the wire to be 0.5%, the pH of the paper stock on the wire to be 7.5, and the pulp-to-wire speed ratio to be 0.97. The paper stock is dewatered by a long wire, pressed, dried, calendered, wound and re-wound to obtain archival paper.

[0087] The prepared archival paper has a basis weight of 100 g / m 2 ; the moisture content is 5.2%; the Kappa number of the formed paper is 1.35.

[0088] As can be seen from the above examples, the embodiments of the present invention mainly select slurries with better strength and adopt processes such as neutral sizing, so that the prepared paper is inherently alkaline, antioxidant (the antioxidant Kappa number of the formed paper is relatively low), has good durability, and is conducive to being used as archival paper.

[0089] The above examples are only used to illustrate the technical features and implementation process of the present invention, rather than limiting the technical solutions of the present invention. It should be noted that for those of ordinary skill in the art, the present invention can still be modified or equivalently replaced, and any modification or replacement that does not depart from the principle of the present invention is covered by the protection of the present invention.

Claims

1. A method for manufacturing archival paper, characterized in that: The following steps are involved: The bleached conifer pulp and the bleached hardwood pulp are respectively beaten with cellulase, and the pulp freeness is controlled at 280-350 mL; then mixed according to proportion to obtain a mixed pulp; the ratio of the bleached conifer pulp to the bleached hardwood pulp is 50-70wt%:30-50wt%; Auxiliary materials are added to the mixed slurry, wherein the auxiliary materials include cationic starch, reinforcing agent, filler, retention aid and neutral sizing agent; the mixed slurry is shaped by forming on the net in a neutral range and neutral sizing is performed to obtain archival paper.

2. The manufacturing method according to claim 1, characterized in that: The pulping is performed by cone milling, and the cellulase is added at 0.02-0.06 kg / ton of paper before pulping; ligninase is also added after pulping, and then mixed to obtain a mixed pulp.

3. The manufacturing method according to claim 1, characterized in that: The filler is calcium carbonate; the retention aid is one or more of bentonite, cationic polyacrylamide and microparticles; and the neutral sizing agent is alkenyl succinic anhydride.

4. The manufacturing method according to claim 2, characterized in that: Before the pulping, 0.1-0.2 kg / ton of paper water-draining enzyme is added; and / or the auxiliary materials also include a water-draining synergist.

5. The manufacturing method according to claim 4, characterized in that: The amount of the neutral sizing agent added is 1-2 kg / ton of paper.

6. The manufacturing method according to any one of claims 1 to 5, characterized in that: The auxiliary materials also include dyes and / or whitening agents.

7. The manufacturing method according to any one of claims 1 to 5, characterized in that: The materials used for the neutral sizing include native starch and a neutral surface sizing agent.

8. The manufacturing method according to claim 8, characterized in that: The dosage of the neutral surface sizing agent is 2-5 kg / ton of paper; the neutral surface sizing agent is a mixture of a styrene-acrylic acid polymer sizing agent and a water-resistant alkyl ketene dimer sizing agent.

9. An archival paper obtained by the manufacturing method according to any one of claims 1 to 8, wherein the pH value of the finished product is 8 to 8.

5.

10. The archival paper according to claim 9, characterized in that: The archival paper has a basis weight of 70-100 g / m 2 , the antioxidant Kappa value is 0.6-0.9.

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