Glassine paper and preparation process thereof

Abstract

The invention relates to the technical field of papermaking, and particularly provides glassine paper and a preparation process thereof.The preparation process of the glassine paper comprises the steps that S100, larch pulp, eucalyptus pulp, glass fibers and polyester staple fibers are mixed, TEMPO-oxidized nanocellulose is added, pulp is prepared, after the pH is adjusted to 4.5-5.2, a composite bio-enzyme system is added for stirring treatment, and after stirring treatment is conducted, the glassine paper is obtained; adding a polycarboxylic acid cross-linking agent and a catalyst for cross-linking reaction to obtain cross-linked modified slurry; s200, carrying out wet-process papermaking molding, dehydration and drying on the cross-linked modified pulp to obtain a paper blank; s300, immersing the paper blank into a Tris buffer solution of dopamine hydrochloride, coating with a sizing agent, drying and curing, and carrying out calendering treatment to obtain a paper surface; and S400, carrying out corona treatment on the paper surface, and coating a release agent to obtain the glassine paper. The glassine paper prepared by the invention has excellent heat resistance, oil resistance, tear resistance and good release performance, and is suitable for food packaging and industrial release materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of papermaking, and particularly relates to a glassine paper and a preparation process thereof. BACKGROUND

[0002] The glassine paper is widely used in the fields of food packaging, baking paper, medical isolation film and industrial release material, and has high requirements for light transmission, oil resistance, heat resistance and mechanical strength. At present, the production mainly depends on high-quantity beating, fine calendaring and surface coating process to improve the barrier and release performance, but there is a trade-off between light weight, surface densification and environmentally friendly coating.

[0003] Under the condition of light weight, the paper strength is insufficient, and the oil resistance and heat resistance are limited; the traditional fluorine-containing or organic solvent type coating has poor environmental protection and is difficult to recycle and process; in addition, the surface functionalization and release layer are not firmly combined, and the batch stability and consistency of industrial scale production are also difficult to meet the requirements.

[0004] Therefore, there is an urgent need for a glassine paper with high strength, excellent oil resistance, heat resistance and stable release performance and a preparation process thereof. SUMMARY

[0005] The present application aims to solve at least one of the above problems.

[0006] The present application provides a preparation process of a glassine paper, which comprises the following steps: S100, mixing larch pulp, eucalyptus pulp, glass fiber and polyester staple fiber, and adding TEMPO-oxidized nanocellulose to prepare pulp and adjust the pH to 4.5-5.2, then adding a composite enzyme system for stirring treatment, and then adding a polycarboxylic acid crosslinking agent and a catalyst for crosslinking reaction to obtain crosslinked modified pulp; S200, wet laying the crosslinked modified pulp to form a paper blank, dehydrating and drying to obtain a paper blank; S300, immersing the paper blank in a dopamine hydrochloride Tris buffer solution, then coating with a sizing agent, drying and solidifying, and calendering to obtain a paper surface; S400, performing corona treatment on the paper surface, and coating a release agent to obtain a glassine paper.

[0007] In any of the above technical solutions, S100 further comprises: S001, pretreating the larch pulp and the eucalyptus pulp respectively; wherein the larch pulp pretreatment comprises pre-soaking in a 10-15% NaOH solution for 40-50 min and beating to 28-36°SR; and the eucalyptus pulp pretreatment comprises pre-soaking in an 8-12% NaOH solution for 25-35 min and beating to 35-40°SR.

[0008] In any of the technical solutions above, in S100, the mass ratio of the larch pulp to the eucalyptus pulp, the glass fiber, the polyester staple fiber, and the TEMPO-oxidized nanocellulose is 1:(0.31-0.64):(0.05-0.18):(0.03-0.15), the mass fraction of the TEMPO-oxidized nanocellulose is 0.2-2.0 wt% based on the total mass of the dry fibers, the polycarboxylic acid crosslinking agent includes 1,2,3,4-butanetetracarboxylic acid, the mass fraction of the polycarboxylic acid crosslinking agent is 1.0-6.0 wt% based on the total mass of the dry fibers, the catalyst includes at least one of p-toluenesulfonic acid, sulfosuccinic acid, sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium bisulfite, and ascorbic acid, and the mass fraction of the catalyst is 0.5-3.0 wt% based on the total mass of the dry fibers, and the complex enzyme system includes cellulase and xylanase, and the mass ratio of the cellulase to the xylanase is (2-4):1.

[0009] In any of the technical solutions above, in S100, the TEMPO-oxidized nanocellulose is pre-dispersed before being added, the pre-dispersion is performed by at least one of high-shear dispersion, ultrasonic, and high-pressure homogenization, the stirring treatment is performed at a temperature of 45-55℃ for 3-5h, and the crosslinking reaction is performed at a temperature of 50-70℃ for 0.5-1.5h.

[0010] In any of the technical solutions above, in S100 and S200, further comprising: S111, adding a cationic micro-flocculating agent to the crosslinked modified pulp and stirring to form micro-flocs; and S112, adding a main flocculating polymer after the micro-flocs are formed.

[0011] In any of the technical solutions above, the cationic micro-flocculating agent is at least one of cationic starch, polyethyleneimine, and polydiallyldimethylammonium chloride, and the main flocculating polymer includes cationic polyacrylamide.

[0012] In any of the technical solutions above, in S300, the sizing agent is a fluorine-containing polyester sizing agent, the solid content is 10-15%, and the coating amount is 1.5-2.5 g / m 2 ; the calendering treatment is gradient calendering treatment, including: one-stage calendering and two-stage calendering, the one-stage calendering is performed at 100-150℃ and 220-250 kN / m, and the two-stage calendering is performed at 150-200℃ and 280-320 kN / m.

[0013] In any of the technical solutions above, between the one-stage calendering and the two-stage calendering, or after the two-stage calendering, further comprising: spraying and humidifying treatment with 65-85℃ hot water.

[0014] In any of the technical solutions above, in S400, the corona power is 24-28 W / m 2 ; the release agent includes 20-25% methyl silicone oil and 5-8% nano-SiO2 in terms of mass percentage.

[0015] The application also provides a glassine paper prepared by the preparation process of any one of the above technical solutions.

[0016] The technical effects achieved by the technical solution of the application are as follows: 1. By synergizing long and short fibers of larch and eucalyptus, reinforcing glass fibers and polyester short fibers, constructing a nanometer network adhesive phase by TEMPO-oxidized nanocellulose, and in-situ cross-linking by enzyme and polycarboxylic acid, high dry tensile and tear resistance and excellent wet strength retention can be achieved at low basis weight; 2. After interface modification by polydopamine, sizing with fluorine-containing polyester, segmented calendering and corona activation, and coating with methyl silicone oil / nano-silicon dioxide release layer, a dense and low surface energy functional film layer can be formed, showing high oil resistance grade, low thermal shrinkage rate and consistent and controllable release force; 3. By taking nanometer / enzyme method and in-situ cross-linking in water phase as the core, combining micro-flocculation-main flocculation retention strategy and controllable partition drying, energy consumption and nanometer component loss are reduced, batch consistency is improved, and it is convenient to be compatible with existing wet paper production line and conducive to large-scale production and process stability. DETAILED DESCRIPTION

[0017] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the present application will be further described in detail below with specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0018] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, however, the present application can also be implemented in other ways different from those described herein, therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0019] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below.

[0020] Glassine paper is widely used in food packaging, baking paper, medical isolation film and industrial release material, etc. fields, and has high requirements on light transmission, oil resistance, heat resistance and mechanical strength. At present, the production mainly depends on high basis weight beating, fine calendering and surface coating process to improve the barrier and release performance, but there is a trade-off between light weight, surface densification and environmentally friendly coating. Under the condition of light weight, the paper strength is insufficient, the oil and heat resistance is limited; traditional fluorine-containing or organic solvent type coating has poor environmental protection and is difficult to recycle and process; in addition, the combination of surface functionalization and release layer is not firm enough, and the batch stability and consistency of industrial scale production are also difficult to meet the demand.

[0021] Therefore, the embodiment provides a glassine paper and a preparation process thereof, which can significantly improve the mechanical strength, tear resistance and dimensional stability of the paper while maintaining low basis weight and lightweight. The key is to combine TEMPO-oxidized nanocellulose with composite enzyme pretreatment to construct a nanofiber network reinforcement framework and promote fiber micro-fining, thereby forming a tighter physical lock between fibers; adding glass fibers and polyester staple fibers to reinforce the large-scale mechanical properties, balancing stiffness and fracture toughness. In-situ chemical crosslinking is performed in the slurry stage using a polycarboxylic acid crosslinking agent, which can improve wet strength and chemical corrosion resistance, and the crosslinking process is controllable under weak acidic conditions, which is conducive to industrial scaling and batch stability. The paper blank is immersed in a dopamine hydrochloride Tris buffer solution, and a polydopamine coating is initiated in the Tris buffer to form a biomimetic adhesion layer, which significantly enhances the interfacial bonding force of the sizing agent and the release agent, solving the problem of poor adhesion and layer peeling of traditional coatings. Subsequent sizing, drying, calendering and corona treatment processes simultaneously achieve surface densification and surface energy matching, resulting in a uniform and continuous functional film layer of the release agent, which exhibits excellent oil resistance, heat resistance and controllable release performance. The overall process avoids the use of fluorine-containing or large amounts of organic solvent coating systems, balancing environmental protection and recyclability; at the same time, the enzymatic and aqueous crosslinking pathways reduce energy consumption and process mildness, facilitating compatibility with existing wet paper production lines and having good potential for scaled production. Therefore, the present application not only has significant technical features in material synergy and interface engineering, but also is superior to existing technologies in performance, environmental protection and industrial adaptability, and is suitable for applications such as baking paper, food packaging, medical isolation film and industrial release materials.

[0022] Specifically, the embodiment provides a preparation process of a glassine paper, which comprises the following steps: S100, mixing the larch pulp, eucalyptus pulp, glass fiber and polyester staple fiber, adding TEMPO-oxidized nanocellulose, preparing a slurry, adjusting the pH to 4.5-5.2, then adding a composite enzyme system for stirring treatment, and then adding a polycarboxylic acid crosslinking agent and a catalyst for crosslinking reaction to obtain a crosslinked modified slurry; S200, wet-forming, dewatering and drying the crosslinked modified slurry to obtain a paper blank; S300, immersing the paper blank in a Tris buffer solution of dopamine hydrochloride, then coating with a sizing agent, drying and solidifying, and calendering to obtain a paper surface; S400, corona treating the paper surface and coating a release agent to obtain a glassine paper.

[0023] Preferably, in step S100, the larch pulp is mixed with eucalyptus pulp, glass fiber, and polyester short fiber in a mass ratio of 1: (0.31-0.64): (0.05-0.18): (0.03-0.15) based on the dry fiber. The larch pulp can provide tensile strength and structural continuity of the paper web, the eucalyptus pulp fills the inter-fiber gaps and improves surface smoothness and formability; the glass fiber and the polyester short fiber serve as inorganic / synthetic reinforcing phases, significantly improving dry-state stiffness, tear resistance, and thermal stability, while suppressing the strength decline under low basis weight conditions. The fiber network formed by long and short fibers shares stress at different length scales, and the short fibers and nanocellulose / gel components tightly fill the pores, and the composite short and long fibers and the rigid reinforcing phase together form a multi-scale load-bearing architecture, thereby maintaining a low basis weight while achieving higher breaking strength and dimensional stability.

[0024] Further, TEMPO-oxidized nanocellulose (TO-NFC) as a nanoscale reinforcing and bonding phase, its high specific surface area and surface carboxyl density can significantly improve the inter-fiber hydrogen bonding and electrostatic interaction, thereby enhancing the cohesion and interfacial adhesion. Pre-dispersion uses at least one of high-shear dispersion, ultrasonic, and high-pressure homogenization, which can avoid nanofiber agglomeration, ensure uniform distribution in the slurry and maintain high surface area exposure, which is beneficial to the formation of a continuous nanonetwork with the fiber surface. Moreover, the carboxyl groups of TO-NFC not only provide strong hydrogen bonding / electrostatic adsorption sites, but also form micellar-like coatings on the surface of large fibers through physical entanglement, increasing the contact area and friction between fibers, improving the density and barrier properties of the formed paper base, and providing better interface anchoring for the surface post-treatment layer.

[0025] Preferably, the composite enzyme system includes cellulase and xylanase, and the mass ratio of cellulase to xylanase is (2-4): 1. The synergistic pretreatment of cellulase and xylanase realizes selective partial dissolution and surface activation under mild conditions. Cellulase mainly acts on the amorphous region of the fiber, promoting microfibrillation on the fiber surface and increasing the number of accessible hydroxyl groups / terminal groups; xylanase degrades hemicellulose, increasing the surface roughness of the fiber and the openness of the pore channels. The overall effect is to reduce the mechanical beating energy consumption and improve the interfacial bonding efficiency of nanocellulose and fibers, and to avoid excessive weakening of fiber strength through mild and controllable enzymatic modification. Enzymatic cleavage exposes the ends of microfibers and more hydroxyl sites, enhancing the formation of subsequent cross-linking and hydrogen bonding networks, thereby improving dry and wet strength and uniformity.

[0026] Preferably, the polycarboxylic acid crosslinking agent comprises 1,2,3,4-butanetetracarboxylic acid, and the addition amount of the polycarboxylic acid crosslinking agent is 1.0-6.0 wt% based on the total mass of dry fibers; the polycarboxylic acid can be esterified and crosslinked with the hydroxyl groups of the fibers under the conditions of heating and catalysis to form chemical crosslinking points to improve the wet strength and chemical resistance. The catalyst comprises at least one of p-toluenesulfonic acid, sulfosuccinic acid, sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium bisulfite, and ascorbic acid, and the addition amount of the catalyst is 0.5-3.0 wt% based on the total mass of dry fibers; by promoting the dehydration of carboxyl groups to generate intermediate active anhydride or reducing the reaction activation energy, the crosslinking rate and efficiency are significantly improved. The crosslinking establishes covalent anchor points between the fibers that can resist hydrolysis, reduces the interface instability caused by water swelling, and thus significantly improves the wet strength and thermal stability; appropriate crosslinking can also improve the chemical and heat resistance of the paper base without significantly increasing the brittleness, which is beneficial to the stability of the subsequent high-temperature sizing and drying processes.

[0027] Overall, the TO-NFC is pre-dispersed, enzymatically mildly modified, and in-situ polycarboxylic acid crosslinked in sequence, and the weak acidity is conducive to the regulation of enzyme activity and avoids the rapid inactivation of TEMPO products; the enzymatic pre-activity can increase the number of reactive sites, and subsequent moderate heating can promote efficient crosslinking. This sequential synergistic process can maximize the complementarity of nano / microstructure: the nano network and enzymatic microfibrillation first construct a high-surface-area substrate that can be physically / chemically combined, and then a three-dimensional network is locked through chemical crosslinking, thereby achieving high dry / wet strength, good surface density, and batch stability under light-weight conditions, and facilitating large-scale production in existing wet papermaking lines.

[0028] Further, S100 and S200 also include: S111, adding a cationic micro-flocculating agent to the crosslinking and modification slurry and stirring to form micro-flocs; S112, after the micro-flocs are formed, adding a main flocculating polymer. First, the cationic micro-flocculating agent undergoes primary adsorption with the negatively charged fiber surface, TEMPO-oxidized nanocellulose, and small filler particles through rapid charge neutralization / pasting to generate small and stable micro-flocs, which lock the nano and sub-micron components as core flocs in the white water, significantly reducing their loss with the water flow. Then, the main flocculating agent is added to further aggregate the micro-flocs into filterable medium-scale flocs through the bridging action of the macromolecular chains, thereby improving the retention rate and solid recovery, improving the screen efficiency, and accelerating the drainage rate. The micro-flocculating agent controls the primary charge balance and microstructure, and the main flocculating agent provides a mechanically stable bridging network, so that the flocs are more resistant to shear and less likely to be redispersed during the screen and press processes. This reduces the white water turbidity and solid loss, improves the retention rate of nanocellulose and short fiber / glass fiber, enhances the uniformity of forming, reduces the drying energy consumption and chemical dosage, and provides a more uniform and controllable microstructure for subsequent pressing, drying, and surface functionalization, which is beneficial to industrial scaling and batch stability.

[0029] Preferably, in step S300, after the paper blank is immersed in the Tris buffer solution of dopamine hydrochloride, dopamine self-polymerizes into a polydopamine film under suitable oxidation / alkalization conditions and forms a uniform biomimetic adhesion layer on the fiber surface. The chemical activity sites and interfacial bonding force of the paper surface can be significantly improved, the adhesion between the subsequent organic coating and the fiber matrix is enhanced, and the coating spreadability and continuity are improved. Polydopamine contains functional groups such as catechol / quinone and amine, which can interact with the fiber surface and also covalently bond or coordinate with the coating polymer to form an interfacial bonding layer. At the same time, the thin film structure can fill the micro-pores and improve the surface uniformity, thereby providing a firm interfacial anchoring for the sizing and release layer.

[0030] Further, by using a fluorine-containing polyester sizing agent with a solid content of 10-15% and a coating amount of 1.5-2.5 g / m 2 A functional film with low surface energy and good film-forming properties can be formed on the paper surface, which gives the paper excellent oil resistance, heat resistance, and release properties. Low coating amount can cover the surface and achieve stable release force, balancing economy and performance; the polyester main chain provides good film-forming properties and thermal stability, and the fluorine substitution segment significantly reduces the surface energy, improves oil and water repellency, and improves the ease of demolding. During the drying / solidification process, the polymer chain melts and flows to form a continuous film; with a polydopamine bottom layer, the polyester segment can have stronger interfacial interaction and mechanical embedding with the polar sites on the surface of polydopamine, reducing the risk of peeling, cracking, and delamination of the coating, thereby improving the durability and batch stability of the coating.

[0031] In addition, the first calendering mainly completes the initial curing and surface compaction of the coating. At this temperature / pressure, the polyester sizing agent begins to soften and flow, residual solvents and bound water are expelled, and initial bonding and spreading between the coating and the substrate occurs. It can improve the surface smoothness and form a continuous film without causing excessive fiber collapse; the inclusion of thermotropic viscous flow causes polymer chains to entangle with each other, and pressure promotes the coating to fill micro-pores and enhance the contact area with the fibers, thereby laying a uniform foundation for the second stage of high-temperature and high-pressure densification. The second calendering realizes deep densification and final film formation at higher temperature and pressure, and the polyester sizing agent further flows, fuses with each other, and forms a more firm interfacial bond with the polydopamine layer and the fiber matrix at a higher temperature, the porosity is significantly reduced, and the surface flatness, gloss, and release uniformity are significantly improved. The oil / heat resistance limit is improved, the oil penetration and bubble defects caused by micro-pores are reduced, and the release performance consistency is higher; thermal flow and pressure-driven chain rearrangement, chain entanglement, and possible end reactions, thereby melting the coating and the substrate into a stable composite interface at the microscale.

[0032] Finally, hot water spraying and humidification at 65-85°C are carried out between the two calendering processes or after the second calendering process. The short-time spraying of hot water makes the fibers moderately expand, the surface plasticize, and a certain moisture content is brought in, which reduces the surface brittleness and the residual stress in the coating, thereby reducing micro-cracks and peeling during the subsequent high-temperature and high-pressure processing or cooling process. Thus, the ductility and conformability of the coating are improved, the flow effect during the second calendering process is improved, and the defect rate is reduced; the penetration and plasticization of water molecules between the fiber and the polydopamine interface improve the movement ability of the molecular chain, making the polyester more easily flow during the second calendering process and achieving good embedding with the fiber / substrate, and the hot water can also clean the surface loose particles and solvent residues, enhancing the coating integrity and release uniformity. It should be noted to control the spraying temperature and the amount of water applied to avoid excessive wetting, which may cause moisture regain or prolong the drying cycle.

[0033] Preferably, in step S400, the paper surface is subjected to corona treatment, the power is 24-28 W / m 2 The surface energy and surface active sites can be significantly improved without damaging the mechanical properties of the substrate, and the uniformity of the subsequent release agent spreading and adhesion is improved. The active oxygen / free radicals generated by high-voltage discharge slightly oxidize the paper surface, open or introduce polar functional groups such as hydroxyl, carboxyl, and carbonyl groups, and produce micron / submicron surface roughening, thereby enhancing the wettability and interface chemical / physical anchoring ability. The release agent used contains 20-25% methyl silicone oil as the main low surface energy component. Methyl silicone oil has good heat resistance, chemical inertness, and low surface energy characteristics, and can form a continuous and thin silicone oil enrichment layer on the paper surface, giving the glassine paper excellent release, oil-repellent, and high-temperature release properties. The methyl-substituted silicone main chain arranges towards the surface through low-energy methyl end groups, forming a low surface energy interface, reducing the interfacial adhesion, and thus achieving controllable and stable release / release performance; 5-8% nano-silicon dioxide is added to the release agent, mainly for improving the microstructure, rheological properties, and durability of the coating: nano-silicon dioxide as a filler / thickening and interface adjusting phase can inhibit the migration of silicone oil in the substrate, improve the wear resistance and temperature stability of the coating, and fine-tune the release force by constructing micro-roughness.

[0034] Further, the polar sites introduced by corona treatment on the paper surface and the micro-roughening, together with the polydopamine adhesion layer formed in step S300, provide chemical and mechanical double anchoring for the release agent, and the polydopamine provides abundant polar groups and mechanical embedding sites, and the corona improves the surface activity, both of which enable the methyl silicone / nano-silicon dioxide coating to form a low-energy layer with a surface rich in silicone oil after drying and to be stably captured with the bottom layer through nano-particles, avoiding peeling, migration, or falling off of the coating under high temperature / mechanical friction. This synergy ensures the consistency of the release force, the durability of the coating, and the batch stability of the product.

[0035] Example 1 The embodiment provides a glassine paper and a preparation process thereof, and the preparation process of the glassine paper comprises the following steps. S001, respectively pretreat the larch pulp and the eucalyptus pulp, the pretreatment of the larch pulp comprises: pre-impregnation in a 10% NaOH solution for 50 min and beating to 28°SR; the pretreatment of the eucalyptus pulp comprises: pre-impregnation in an 8% NaOH solution for 35 min and beating to 35°SR; S100, the mass ratio of the larch pulp, the eucalyptus pulp, the glass fiber and the polyester staple fiber is 1:0.31:0.05:0.03, and 0.2wt% TEMPO-oxidized nanocellulose is added, the pulp is prepared and the pH is adjusted to 4.5, then a composite enzyme system is added for stirring treatment at 45°C for 5h, and then 1.0wt% 1, 2, 3, 4-butanetetracarboxylic acid and 0.5wt% p-toluenesulfonic acid are added for crosslinking reaction at 50°C for 1.5h, to obtain a crosslinking modified pulp, wherein the composite enzyme system comprises cellulase and xylanase, and the mass ratio of the cellulase to the xylanase is 2:1; the TEMPO-oxidized nanocellulose is pre-dispersed before being added; S111, cationic starch is added to the crosslinking modified pulp and stirred to form microflocs; S112, after the microflocs are formed, cationic polyacrylamide is added; S200, the crosslinking modified pulp is subjected to wet laying forming, dehydration and drying to obtain a paper blank; S300, after the paper blank is immersed in a dopamine hydrochloride Tris buffer solution, a fluorine-containing polyester sizing agent with a solid content of 10% is coated on the paper blank at a coating amount of 1.5g / m 2 , drying, curing and calendering treatment to obtain a paper surface, wherein the calendering treatment is gradient calendering treatment, which comprises one-stage calendering and two-stage calendering; the one-stage calendering is performed at 100°C and 220kN / m, the two-stage calendering is performed at 150°C and 280kN / m, and spraying humidification treatment with hot water at 65°C is performed between the one-stage calendering and the two-stage calendering; S400, the paper surface is subjected to 24W / m 2 corona treatment, and a release agent is coated to obtain the glassine paper; wherein the release agent comprises 20% methyl silicone oil and 5% nano-SiO2 in mass percentage.

[0036] Embodiment 2 The embodiment provides a glassine paper and a preparation process thereof, and the preparation process of the glassine paper comprises the following steps. S001, respectively pretreat the larch pulp and the eucalyptus pulp, the pretreatment of the larch pulp comprises: pre-impregnation in a 10% NaOH solution for 50 min and beating to 28°SR; the pretreatment of the eucalyptus pulp comprises: pre-impregnation in an 8% NaOH solution for 35 min and beating to 35°SR; S100, mixing larch pulp, eucalyptus pulp, glass fiber, polyester staple fiber in a mass ratio of 1:0.45:0.1:0.09 by dry fiber, and adding 1.0wt% TEMPO-oxidized nanocellulose, preparing the slurry and adjusting the pH to 5.0, then adding a composite enzyme system for 50℃ stirring treatment for 4h, then adding 4wt% 1,2,3,4-butanetetracarboxylic acid, 2.0wt% potassium dihydrogen phosphate for 60℃ crosslinking reaction for 1h, to obtain a crosslinked modified slurry, wherein the composite enzyme system comprises cellulase and xylanase, and the mass ratio of cellulase to xylanase is 3:1; ultrasonic pre-dispersion is performed before adding TEMPO-oxidized nanocellulose; S111, adding polyethyleneimine to the crosslinked modified slurry and stirring to form microflocs; S112, after the microflocs are formed, adding cationic polyacrylamide; S200, wet laying the crosslinked modified slurry to form a paper blank; S300, after the paper blank is immersed in a dopamine hydrochloride Tris buffer solution, a fluorine-containing polyester sizing agent with a solid content of 13% is coated at 2.0g / m 2 , drying and curing, calendering treatment to obtain a paper surface, wherein the calendering treatment is gradient calendering treatment, including: one-stage calendering and two-stage calendering: the one-stage calendering is at 130℃, 230kN / m, and the two-stage calendering is at 180℃, 300kN / m, and a spraying humidification treatment with 70℃ hot water is performed between the one-stage calendering and the two-stage calendering; S400, corona treatment of the paper surface at 26W / m 2 , coating a release agent to obtain a Graassin paper; wherein the release agent comprises 26wt% methyl silicone oil and 6wt% nano-SiO2.

[0037] Example 3 The present embodiment provides a Graassin paper and a preparation process thereof, the preparation process of the Graassin paper comprising the following steps: S001, pretreating larch pulp and eucalyptus pulp separately, the larch pulp pretreatment comprising: pre-soaking in 15% NaOH solution for 40min and beating to 36°SR; the eucalyptus pulp pretreatment comprising: pre-soaking in 12% NaOH solution for 25min and beating to 40°SR; S100, mixing larch pulp, eucalyptus pulp, glass fiber, and polyester staple fiber in a mass ratio of 1:0.64:0.18:0.15 on a dry fiber basis, adding 2wt% TEMPO-oxidized nanocellulose, preparing a pulp, adjusting the pH to 5.2, then adding a composite enzyme system for stirring treatment at 55°C for 3h, then adding 6.0wt% 1,2,3,4-butanetetracarboxylic acid and 3.0wt% ascorbic acid for crosslinking reaction at 70°C for 0.5h to obtain a crosslinked modified pulp, wherein the composite enzyme system comprises cellulase and xylanase, and the mass ratio of cellulase to xylanase is 4:1; before adding TEMPO-oxidized nanocellulose, high-pressure homogenization pre-dispersion is performed; S111, adding polydiallyldimethylammonium chloride to the crosslinked modified pulp and stirring to form microflocs; S112, after the microflocs are formed, adding cationic polyacrylamide; S200, wet laying the crosslinked modified pulp to form a paper blank; S300, after the paper blank is immersed in a dopamine hydrochloride Tris buffer solution, a fluorine-containing polyester sizing agent with a solid content of 15% is coated on the paper blank at a coating amount of 2.5g / m 2 , drying and curing, and calendering to obtain a paper surface, wherein the calendering is gradient calendering, including one-stage calendering and two-stage calendering: the one-stage calendering is performed at 150°C and 250kN / m, and the two-stage calendering is performed at 200°C and 320kN / m, and after the two-stage calendering, a spraying humidification treatment is performed using hot water at 85°C; S400, corona treatment is performed on the paper surface at a power of 28W / m 2 , a release agent is coated to obtain a Graassin paper; wherein the release agent comprises 28wt% methyl silicone oil and 8wt% nano-SiO2.

[0038] Comparative Example 1 This comparative example provides a Graassin paper, which is obtained by purchase.

[0039] Performance Test The Graassin papers of Examples 1-3 and Comparative Example 1 are subjected to the following performance tests: Dry tensile strength test: the dry tensile strength of the Graassin papers of Examples 1-3 and Comparative Example 1 is tested according to GB / T 12914-2018; Wet strength retention rate test: the wet strength improvement effect of the polycarboxylic acid crosslinking agent of the Graassin papers of Examples 1-3 and Comparative Example 1 is tested according to ISO 3781:2011; Tear resistance test: the tear resistance of the Graassin papers of Examples 1-3 and Comparative Example 1 is tested according to GB / T 455-2020; Release force: measure the release force of silicone oil coating from the tape according to FINAT FTM 10 Test Example 1-3 and Comparative Example 1 release paper; Heat shrinkage: measure the dimensional change rate of Example 1-3 and Comparative Example 1 release paper after 200℃ oven treatment for 10 min; Oil resistance: measure the penetration and strength loss of Example 1-3 and Comparative Example 1 release paper after 120℃ edible oil immersion for 2h according to GB / T 5406-2002; The test results are shown in Table 1.

[0040] Table 1 From Table 1, the dry tensile strength and tear strength of Example 1-3 are improved, which verifies the multi-scale reinforcement of fibers and the synergistic effect of enzyme-crosslinking. The heat shrinkage at 200℃ is much lower than that of Comparative Example 1, and the oil resistance reaches the highest level of 12, which proves the barrier effect of crosslinking network and fluorine-containing polyester sizing agent on heat / oil. The excellent release force performance reflects the synergistic optimization of release uniformity of corona treatment and nano-silicon dioxide.

[0041] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "a specific embodiment", and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0042] Although the present application is disclosed as above, the present application is not limited thereto. Any person skilled in the art, without departing from the spirit and scope of the present application, can make various changes and modifications, therefore the protection scope of the present application should be limited by the scope defined in the claims.

Claims

1. A process for the preparation of a glassine paper, characterized in that, The preparation process of the glassine paper comprises the following steps: S100, mixing the larch pulp, eucalyptus pulp, glass fiber and polyester staple fiber, adding TEMPO-oxidized nanocellulose, adjusting the pH of the slurry to 4.5-5.2, then adding a composite enzyme system for stirring treatment, and then adding a polycarboxylic acid crosslinking agent and a catalyst for crosslinking reaction to obtain a crosslinking modified slurry; S200, wet-forming, dewatering and drying the crosslinking modified slurry to obtain a paper blank; S300, after the paper blank is immersed in a dopamine hydrochloride Tris buffer solution, a sizing agent is coated, dried and solidified, and calendered to obtain a paper surface; S400, the paper surface is subjected to corona treatment and coated with a release agent to obtain the glassine paper.

2. The manufacturing process according to claim 1, characterized in that, The S100 further comprises the following steps: S001, pretreating the larch pulp and the eucalyptus pulp separately; The pretreatment of the larch pulp comprises pre-soaking in a 10-15% NaOH solution for 40-50 min and beating to 28-36°SR; and the pretreatment of the eucalyptus pulp comprises pre-soaking in an 8-12% NaOH solution for 25-35 min and beating to 35-40°SR.

3. The manufacturing process of claim 1, wherein, In the S100, The mass ratio of the larch pulp, the eucalyptus pulp, the glass fiber and the polyester staple fiber is 1:(0.31-0.64):(0.05-0.18):(0.03-0.15) based on the dry fiber; The TEMPO-oxidized nanocellulose accounts for 0.2-2.0wt% of the total dry fiber; The polycarboxylic acid crosslinking agent comprises 1,2,3,4-butanetetracarboxylic acid, and the addition amount of the polycarboxylic acid crosslinking agent accounts for 1.0-6.0wt% of the total dry fiber; The catalyst comprises at least one of p-toluenesulfonic acid, sulfosuccinic acid, sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium bisulfite and ascorbic acid, and the addition amount of the catalyst accounts for 0.5-3.0wt% of the total dry fiber; The composite enzyme system comprises cellulase and xylanase, and the mass ratio of the cellulase to the xylanase is (2-4):

1.

4. The manufacturing process of claim 1, wherein, In the step S100: The TEMPO-oxidized nanocellulose is pre-dispersed before being added, and the pre-dispersion is performed by at least one of high-shear dispersion, ultrasonic and high-pressure homogenization; The stirring treatment is performed at a temperature of 45-55℃ for 3-5h; The crosslinking reaction is performed at a temperature of 50-70℃ for 0.5-1.5h.

5. The manufacturing process of claim 1, wherein, The S100 and the S200 further comprise the following steps: S111, adding a cationic micro-flocculating agent to the crosslinking modified slurry and stirring to form micro-flocs; S112, after the micro-flocs are formed, a main flocculating polymer is added.

6. The preparation process according to claim 5, wherein The cationic micro-flocculating agent is selected from at least one of cationic starch, polyethyleneimine and polydiallyldimethylammonium chloride; The main flocculating polymer comprises cationic polyacrylamide.

7. The manufacturing process of claim 1, wherein, In the S300, The sizing agent is a fluorine-containing polyester sizing agent, solid content is 10-15%, coating amount is 1.5-2.5g / m 2 ; The calendering treatment is gradient calendering treatment, which comprises one-stage calendering and two-stage calendering: The first calendering is at 100-150℃, 220-250kN / m, The second calendering is at 150-200℃, 280-320kN / m.

8. The manufacturing process of claim 7, wherein, Between the first calendering and the second calendering, or after the second calendering, further comprising: spraying and humidifying treatment with 65-85℃ hot water.

9. The manufacturing process of claim 6, wherein, In the S400, The corona power is 24-28 W / m 2 ; The release agent comprises 20-25% of methyl silicone oil and 5-8% of nano-SiO by mass percentage 2。 10. A glassine paper characterized by, The Glaucin paper is prepared by the preparation process according to any one of claims 1-9.

Images