Preparation method of printable packaging composite board formed based on coal gangue and calcium carbonate

Abstract

The invention relates to a preparation method of a printable packaging composite board formed on the basis of coal gangue and calcium carbonate, which comprises the following steps: S1, activating the coal gangue, and placing the coal gangue in a nitrogen protective atmosphere with the flow rate of 2-5L / min; step S2, preparing a porous lightweight aggregate; s3, preparing mixed slurry; s4, gradient foaming and forming; and S5, curing and shaping. The preparation method has the beneficial effects that the coal gangue activated by microwave irradiation is combined with the porous lightweight aggregate formed by radio frequency plasma treatment, and a unique formula and a preparation process are matched, so that the prepared composite board has various excellent properties such as light weight, high strength, heat insulation, sound absorption and good printability; the density of the board is reduced due to the introduction of the porous lightweight aggregate, the strength and hardness of the material are improved due to the addition of the activated coal gangue, and meanwhile, the board is endowed with good heat insulation and sound absorption effects due to the special microstructure design.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of packaging materials, in particular to a preparation method of a printable packaging composite board formed based on coal gangue and calcium carbonate. BACKGROUND

[0002] With the development of economy and the continuous expansion of the consumer market, the packaging industry has an increasing demand for various packaging materials. Traditional packaging materials mainly include wood, plastic, paper, and some composite materials, etc. However, these materials have many problems in practical application.

[0003] After searching, a coal gangue ecological composite board and its preparation process are disclosed in Chinese patent No. CN116283195B, which belongs to the technical field of building materials. The coal gangue ecological composite board includes the following components: P.O52.5 grade cement, composite ultra-fine mineral admixture, solid waste-based aggregate with a particle size of 0.15-2.36 mm, industrial by-product gypsum, composite alkali metal activator, ecological steel fiber, coupling agent, organic waterproof agent, high-performance water reducing agent, and water. The solid waste-based aggregate with a particle size of 0.15-2.36 mm includes red gangue, black gangue, and steel slag. The present application utilizes a large amount of coal gangue and other solid waste resources to produce building materials, has high environmental benefits, excellent performance, and can be used for indoor and outdoor decoration. It has a broad application prospect in the decoration market of industrial and civil engineering, and has considerable economic, ecological, and social benefits.

[0004] In the technical solution of the above patent, coal gangue and calcium carbonate are only physically anchored. Under long-term wet and hot cycles, the interface micro-cracks expand, leading to a decrease in the flatness of the board surface and a significant deterioration of the printing dot reproduction. At the same time, calcium carbonate is prone to local carbonization shrinkage and "frosting" in an alkaline environment, which further leads to uneven coal gangue coarse particle grading, resulting in a decrease in ink adhesion and a strip-shaped difference in color density, making it difficult to meet the requirements of high-quality printable packaging. Based on this, the present application designs a preparation method of a printable packaging composite board formed based on coal gangue and calcium carbonate to solve the above problems. SUMMARY

[0005] (I) Technical problems to be solved In view of the above shortcomings and deficiencies of the prior art, the present application provides a preparation method of a printable packaging composite board formed based on coal gangue and calcium carbonate, which solves the technical problems of a decrease in the flatness of the board surface and uneven coal gangue coarse particle grading.

[0006] (II) Technical solutions In order to achieve the above purpose, the main technical solutions adopted by the present application include: The preparation method of the printable packaging composite board formed based on coal gangue and calcium carbonate includes: Step S1, activation treatment of coal gangue, the coal gangue is placed in a nitrogen protective atmosphere with a flow rate of 2-5 L / min, and subjected to microwave irradiation treatment with a power of 15-25 kW for 10-30 min to achieve activation; then the activated coal gangue is ground to a particle size of less than 75 μm; Step S2, preparation of porous lightweight aggregate: calcium carbonate powder and silica aerogel powder are mixed in a mass ratio of 5:1, and subjected to treatment under the action of radio frequency plasma with a power of 50-100 W for 20-40 min, so that the silica aerogel is in-situ coated on the surface of the calcium carbonate particles to form a porous lightweight aggregate; Step S3, preparation of mixed slurry, 35-45 parts of the activated coal gangue powder obtained in step S1, 25-35 parts of the porous lightweight aggregate obtained in step S2, 18-23 parts of waterborne polyurethane resin, 3.0-4.5 parts of reactive isocyanate foaming agent, 0.5-2.0 parts of plant fiber short cut, and 0.1-0.3 parts of amphiphilic block copolymer dispersant are blended, and water is added to adjust the solid content to 45-55% to form a uniform slurry; Step S4, gradient foaming and molding, the slurry obtained in step S3 is injected into a mold with a partitioned independent temperature control function; the surface layer region temperature is set to 100-110℃, the middle layer region temperature is set to 70-80℃, and the inner layer region temperature is set to 90-100℃; heating is carried out in this partitioned gradient temperature field to make the slurry undergo a micro-foaming reaction and component self-assembly simultaneously, forming a three-layer composite structure with a density gradient; Step S5, curing and shaping, the three-layer composite structure obtained in step S4 is subjected to LED-UV light irradiation curing with a wavelength of 365-405 nm and an irradiation energy of 300-500 mJ / cm 2 , and then wound up.

[0007] Preferably, step S1 specifically comprises: Step S1.1, crushing the lump coal gangue to a particle size of less than 5 cm; Step S1.2, placing the crushed coal gangue in a microwave reactor and replacing the air with nitrogen; Step S1.3, starting the microwave generator and irradiating for 10-30 min at a power of 15-25 kW; Step S1.4, after the treatment is completed, cooling to room temperature under nitrogen protection; Step S1.5, grinding the cooled activated coal gangue to ≤75 μm.

[0008] Preferably, step S2 specifically comprises: Step S2.1, pre-mixing calcium carbonate powder and silica aerogel powder in a high-speed mixer at a mass ratio of 5:1 for 5-10 min; Step S2.2, feeding the pre-mixed material into a radio frequency plasma reaction chamber; Step S2.3, introducing argon as working gas to maintain the chamber pressure at 50-200 Pa; Step S2.4, turning on the radio frequency power source and processing for 20-40 min at a power of 50-100 W to make the aerogel depolymerize under plasma excitation and deposit on the surface of calcium carbonate particles; Step S2.5, after the processing is completed, collecting the obtained porous lightweight aggregate under an inert atmosphere.

[0009] Preferably, step S3 specifically includes: Step S3.1, adding water-based polyurethane resin, reactive isocyanate blowing agent, and amphiphilic block copolymer dispersant into a high-speed dispersion kettle, stirring at a speed of 500-1000 rpm for 5-10 min to form a pre-mixed solution; Step S3.2, under continuous stirring, sequentially and slowly adding activated coal gangue powder and porous lightweight aggregate; Step S3.3, adding plant fiber short-cut material, and slowly adding deionized water while stirring; Step S3.4, increasing the stirring speed to 1500-2000 rpm and continuously dispersing for 15-30 min to form a uniform and stable slurry without visible agglomerates.

[0010] Preferably, step S4 specifically includes: Step S4.1, preheating the mold to the target zoned temperature; Step S4.2, uniformly injecting the slurry obtained in step S3 into the mold cavity; Step S4.3, closing the mold and maintaining the zoned temperature for foaming and self-assembly for 5-15 min; Step S4.4, after the holding is completed, demolding to obtain a composite blank with a three-layer gradient density structure.

[0011] Preferably, step S5 specifically includes: Step S5.1, conveying the composite blank obtained in step (d) under an LED-UV curing device; Step S5.2, using a 395 nm LED array light source to irradiate and cure the surface of the plate; Step S5.3, cooling the cured plate with a cooling roller, and then online winding.

[0012] Preferably, the coal gangue used in step S1 is subjected to magnetic separation and iron removal treatment before crushing, so that the content of ferromagnetic impurities is reduced to ≤0.5 wt%; the calcium carbonate powder used in step S2 is precipitated calcium carbonate, and the average particle size D50 is 1-5 μm.

[0013] Preferably, before step S4.4, a pulsed magnetic field is applied to the mold during foaming to orient the plant fibers in the thickness direction of the plate.

[0014] Preferably, the mold in step S4.1 is provided with a micron-scale groove structure in the surface layer region of the cavity; after the slurry is injected, a micro-pressure of 0.1-0.5 MPa is applied in the groove direction before or at the initial stage of foaming to promote the oriented filling of the surface layer slurry into the grooves; In step S4.3, the pressure inside the mold is monitored in real time during foaming and self-assembly; when the pressure in the intermediate layer region reaches a peak value and starts to decrease, it is considered that the micro-foaming is basically completed.

[0015] Preferably, in step S5.1, the LED-UV curing process is divided into two stages: First stage: pre-curing with a 365-385 nm waveband light source to quickly shape the surface layer; Second stage: main curing with a 395-405 nm waveband light source to ensure sufficient cross-linking inside; In step S5.3, the printing surface of the plate is subjected to corona treatment before winding.

[0016] (Three) beneficial effects 1. The present application combines microwave irradiation activated coal gangue with porous lightweight aggregate formed by radio frequency plasma treatment, and uses a unique formula and preparation process, so that the prepared composite plate has multiple excellent properties such as lightweight, high strength, heat insulation, sound absorption and good printing suitability.

[0017] 2. The present application effectively solves the environmental pollution problem caused by the accumulation of coal gangue by activating the coal gangue and using it as the main raw material in the preparation of packaging composite board, and realizes the resource recycling of industrial solid waste.

[0018] 3. The present application uses a zoned gradient temperature field foaming molding technology and LED-UV light irradiation curing technology, which not only realizes the synchronous foaming and self-assembly molding of the composite plate, greatly shortens the production cycle, but also improves the production efficiency and the stability of product quality. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is the process flowchart of the present application; Figure 2 A coal gangue activation process flowchart of the present application; Figure 3 A porous lightweight aggregate preparation flowchart of the present application; Figure 4 An LED-UV curing system diagram of the present application. DETAILED DESCRIPTION

[0020] In order to better explain the present application, so as to be understood, the present application is described in detail below by specific embodiments, combined with the accompanying drawings. In which, the orientation of the "up", "down" and other orientation terms mentioned in this paper are referred to the orientation of the drawings. Figure 1

[0021] The technical problem of the plate surface flatness reduction and the uneven coal gangue coarse particle grading proposed in the embodiment of the present application is solved by combining the microwave irradiation activated coal gangue with the porous lightweight aggregate formed by the radio frequency plasma treatment, and then matching with a unique formula and preparation process, so that the prepared composite board has multiple excellent performances such as lightweight, high strength, heat insulation, sound absorption and good printing suitability.

[0022] In order to better understand the above technical solutions, the exemplary embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a clearer, more thorough understanding of the present application and to enable the scope of the present application to be fully conveyed to those skilled in the art.

[0023] Example 1; Please refer to Figures 1-4 In the embodiment of the present application, the printable packaging composite board preparation method based on coal gangue and calcium carbonate comprises: Step S1, activation treatment of coal gangue, the coal gangue is placed in a nitrogen protective atmosphere with a flow rate of 2-5L / min, and subjected to microwave irradiation treatment with a power of 15-25kW and a time of 10-30min to achieve activation; then the activated coal gangue is ground to a particle size of less than 75μm; Step S2, preparation of porous lightweight aggregate: calcium carbonate powder and silica aerogel powder are mixed in a mass ratio of 5:1, and subjected to treatment under the action of radio frequency plasma with a power of 50-100W and a time of 20-40min, so that the silica aerogel is in-situ coated on the surface of calcium carbonate particles to form a porous lightweight aggregate; ​Step S3, preparation of mixed slurry, 35-45 parts by mass of the activated coal gangue powder obtained in step S1, 25-35 parts by mass of the porous lightweight aggregate obtained in step S2, 18-23 parts by mass of the waterborne polyurethane resin, 3.0-4.5 parts by mass of the reactive isocyanate foaming agent, 0.5-2.0 parts by mass of the plant fiber short-cut material, and 0.1-0.3 parts by mass of the amphiphilic block copolymer dispersant are blended, water is added to adjust the solid content to 45-55%, and a uniform slurry is formed; Step S4, gradient foaming and molding, the slurry obtained in step S3 is injected into a mold with a function of independently controlling the temperature in different zones; the temperature in the surface layer zone is set to 100-110℃, the temperature in the middle layer zone is set to 70-80℃, and the temperature in the inner layer zone is set to 90-100℃; heating is performed in this zonal gradient temperature field to make the slurry undergo a micro-foaming reaction and component self-assembly simultaneously, and a three-layer composite structure with a density gradient is formed; Step S5, curing and shaping, the three-layer composite structure obtained in step S4 is subjected to LED-UV light irradiation curing with a wavelength of 365-405nm and an irradiation energy of 300-500mJ / cm 2 , and then is wound up.

[0024] Step S1 specifically includes: Step S1.1, crushing the blocky coal gangue to a particle size of less than 5cm; Step S1.2, placing the crushed coal gangue in a microwave reactor and replacing the air with nitrogen; Step S1.3, starting the microwave generator and irradiating and treating at a power of 15-25kW for 10-30min; Step S1.4, after the treatment is completed, cooling to room temperature under the protection of nitrogen; Step S1.5, grinding the cooled activated coal gangue to ≤75μm.

[0025] Step S2 specifically includes: Step S2.1, pre-mixing the calcium carbonate powder and the silica aerogel powder at a mass ratio of 5:1 in a high-speed mixer for 5-10min; Step S2.2, feeding the pre-mixed material into a radio frequency plasma reaction cavity; Step S2.3, introducing argon as a working gas to maintain the cavity pressure at 50-200Pa; Step S2.4, turning on the radio frequency power source and treating at a power of 50-100W for 20-40min to make the aerogel depolymerize and deposit and coat on the surface of the calcium carbonate particles under plasma excitation; Step S2.5, after the treatment is completed, collecting the obtained porous lightweight aggregate in an inert atmosphere.

[0026] Step S3 specifically includes: Step S3.1, the waterborne polyurethane resin, the reactive isocyanate blowing agent and the amphiphilic block copolymer dispersant are added into a high-speed dispersion kettle, and stirred at a speed of 500-1000 rpm for 5-10 min to form a premix; Step S3.2, under continuous stirring, the activated coal gangue powder and the porous lightweight aggregate are slowly added in sequence; Step S3.3, the plant fiber short-cut material is added, and deionized water is slowly added while stirring; Step S3.4, the speed is increased to 1500-2000 rpm, and the dispersion is continued for 15-30 min to form a uniform and stable slurry without visible agglomerates.

[0027] Step S4 specifically comprises: Step S4.1, preheat the mold to the target partition temperature; Step S4.2, the slurry obtained in step S3 is uniformly injected into the mold cavity; Step S4.3, close the mold, and keep foaming and self-assembly at the set partition temperature for 5-15 min; Step S4.4, after the holding time is over, the composite blank with a three-layer gradient density structure is taken out after demolding.

[0028] The working principle of the embodiment of the present application is as follows: first, in step S1, the coal gangue is activated; the coal gangue is placed in a nitrogen protective atmosphere and subjected to microwave irradiation, the microwave energy changes the internal structure of the coal gangue, increases the lattice defects, and significantly increases the number of active sites, thereby realizing activation and making it have higher chemical reaction activity and better dispersibility; at the same time, the activated coal gangue is ground to a particle size of less than 75 μm, which can effectively increase its specific surface area and is beneficial to subsequent full mixing and reaction with other components.

[0029] In step S2, when the porous lightweight aggregate is prepared, the calcium carbonate powder and the silica aerogel powder are mixed in a specific mass ratio, and then the high-energy action of the radio frequency plasma is used to make the silica aerogel depolymerize in the plasma environment and uniformly deposit and coat on the surface of the calcium carbonate particles. The porous structure and high specific surface area characteristics of the silica aerogel are retained, and are tightly combined with the calcium carbonate to form a porous lightweight aggregate with a unique microstructure, which not only reduces the density of the aggregate, but also enhances its sound absorption, heat insulation and adsorption properties, thereby providing an excellent physical property basis for the subsequent preparation of the composite board.

[0030] In step S3, the activated coal gangue powder, porous lightweight aggregate, water-based polyurethane resin, reactive isocyanate foaming agent, plant fiber short cut, and amphiphilic block copolymer dispersant are blended according to specific mass fractions. The water-based polyurethane resin serves as the matrix material, has good film-forming and bonding properties, and can effectively bond the components together to form a continuous phase. The reactive isocyanate foaming agent will react with water or other active hydrogen-containing substances in the system during the subsequent foaming process, producing carbon dioxide gas, which in turn drives the slurry to foam and form a microporous structure. The addition of plant fiber short cut plays a role in strengthening and toughening, and through physical entanglement and chemical bonding between the matrix and the plant fiber short cut, the mechanical properties and impact resistance of the composite material are improved. The amphiphilic block copolymer dispersant effectively improves the compatibility between the components, prevents particle agglomeration, and ensures the uniformity and stability of the slurry.

[0031] In step S4, the mixed slurry is injected into a mold with a partitioned independent temperature control function, and the temperatures of the surface layer region, the middle layer region, and the inner layer region of the mold are set to 100-110℃, 70-80℃, and 90-100℃, respectively. Under the action of the partitioned gradient temperature field, the reactive isocyanate foaming agent inside the slurry begins to react and produce gas, initiating the micro-foaming process. Due to the temperature differences in different regions of the mold, the foaming rate and component self-assembly behavior of the slurry show a gradient change; in the high-temperature surface layer region, the foaming rate is faster, forming a relatively dense surface layer structure that improves the surface strength and printing suitability of the board; the middle layer has a lower temperature and a moderate foaming degree, forming a middle layer with good cushioning performance; the inner layer has a temperature between the surface layer and the middle layer, and the micro-porous structure formed by foaming further reduces the density of the board while ensuring certain mechanical properties, thereby realizing the synchronous forming of a three-layer composite structure with a density gradient.

[0032] Finally, in step S5, the three-layer composite structure after forming is subjected to LED-UV light irradiation curing. The specific wavelength (365-405nm) light emitted by the LED-UV light source can excite the photoinitiator in the water-based polyurethane resin, causing it to decompose and produce free radicals, which can initiate crosslinking polymerization of the unsaturated double bonds in the resin, allowing the board to be quickly cured and shaped from the inside out.

[0033] Example 2; Please refer to Figures 1-4 In the embodiments of the present application, step S5 specifically includes: Step S5.1, conveying the composite blank obtained in step (d) to below the LED-UV curing equipment; Step S5.2, using a 395nm LED array light source to irradiate and cure the surface of the board; Step S5.3, the solidified plate is cooled by a cooling roller, and then is wound on line.

[0034] The coal gangue used in step S1 is subjected to iron removal treatment by magnetic separation before crushing, so that the content of ferromagnetic impurities is reduced to <=0.5 wt%; the calcium carbonate powder used in step S2 is precipitated calcium carbonate, and the average particle size D50 is 1-5 um.

[0035] Before step S4.4, a pulsed magnetic field is applied to the mold during foaming, so that the plant fibers are oriented and arranged along the thickness direction of the plate.

[0036] The mold of step S4.1 is provided with a micron-level groove structure in the surface layer area of the cavity; after the slurry is injected, a micro-pressure of 0.1-0.5 MPa is applied in the groove direction before or at the initial stage of foaming, so as to promote the oriented filling of the surface layer slurry in the groove; In step S4.3, the internal pressure of the mold is monitored in real time during foaming and self-assembly; when it is monitored that the pressure of the middle layer area reaches the peak value and starts to decrease, it is considered that the micro-foaming is basically completed.

[0037] In step S5.1, the LED-UV curing process is divided into two stages: First stage: pre-curing is carried out by using a 365-385 nm waveband light source to make the surface layer quickly shape; Second stage: main curing is carried out by using a 395-405 nm waveband light source to ensure sufficient cross-linking inside; In step S5.3, the printed surface of the plate is subjected to corona treatment before winding.

[0038] The working principle of the embodiment of the application is that: in the curing and shaping stage of step S5, the composite blank obtained in step S4 is first conveyed to below the LED-UV curing equipment. A 395 nm LED array light source is used to irradiate and cure the surface of the plate. The light of this wavelength can be efficiently matched with the photosensitive components on the surface of the plate, so as to promote the rapid curing of the surface, form a smooth and high-hardness protective layer, and improve the wear resistance and printing suitability of the plate.

[0039] In step S1, the coal gangue is subjected to magnetic separation and iron removal treatment before crushing, so that the content of ferromagnetic impurities is reduced to ≤0.5wt%, which effectively removes the iron impurities in the coal gangue and prevents the possible adverse chemical reactions caused by iron ions in the subsequent microwave irradiation and plasma treatment, such as local overheating, generation of harmful gases or influence on the electrical properties of the slurry, etc., ensuring the quality of the activated coal gangue and the stability of the subsequent process. At the same time, the precipitated calcium carbonate powder used in step S2 has an average particle size D50 of 1-5μm. This particle size range of calcium carbonate powder can achieve more uniform coating effect with the silica aerogel powder under the action of radio frequency plasma, and the formed porous lightweight aggregate has more ideal microstructure and performance, further improving the lightweight and high-strength characteristics of the composite board.

[0040] During the foaming process before step S4.4, a pulsed magnetic field is applied to the mold, which drives the directional arrangement of plant fibers in the thickness direction of the board, overcoming the random distribution of plant fibers in the slurry and achieving ordered arrangement in a specific direction. This directional arrangement of plant fibers can significantly improve the mechanical properties of the composite board in the thickness direction, such as bending strength and impact resistance, and also helps to improve the thermal stability and dimensional stability of the board.

[0041] In addition, the surface layer region of the mold cavity of step S4.1 is provided with a micron-level groove structure, and after the slurry is injected, a micro-pressure of 0.1-0.5MPa is applied in the groove direction. This micro-pressure promotes the surface layer slurry to preferentially fill in the groove direction, achieving directional flow and filling of the surface layer slurry, and forming a surface with unique texture and microstructure on the surface layer of the board, which not only enhances the aesthetics and slip resistance of the board, but also further improves the density and wear resistance of the surface layer. In the foaming and self-assembly process of step S4.3, the pressure inside the mold is monitored in real time. When the pressure in the middle layer region reaches a peak value and starts to decrease, it indicates that the micro-foaming reaction has been basically completed, and the generation rate and escape rate of the foaming gas have reached a dynamic balance at this time. Through this monitoring index, the foaming time can be accurately controlled to ensure the uniformity of the foaming quality of the composite board.

[0042] It is worth noting that the LED-UV curing process in step S5.1 is divided into two stages, the first stage uses 365-385nm waveband light source for pre-curing, this waveband light can quickly excite the shallow layer of light initiator in the surface layer of the photosensitive component of the board, so that a layer of preliminary cured film is quickly formed on the surface layer, effectively preventing defects such as pinholes, surface tackiness and other problems caused by solvent evaporation or reaction heat accumulation on the surface of the board during the subsequent main curing process. The second stage uses 395-405nm waveband light source for main curing, this waveband light has stronger penetration ability, which can penetrate into the interior of the board, ensuring that the photosensitive components inside are fully cross-linked and cured, thereby realizing uniform and sufficient curing of the board from the surface to the interior, further improving the overall performance and quality stability of the board. Finally, in step S5.3, the printed surface of the board is subjected to corona treatment before winding, which changes the molecular structure of the surface of the board through the action of high-frequency electric field.

[0043] Example 3; Please refer to Figures 1-4 , specific examples are provided, and the lump coal gangue is broken to a particle size of less than 5 cm. The broken coal gangue is placed in a microwave reactor, and nitrogen is introduced to replace air at a flow rate of 3 L / min. Start the microwave generator and irradiate for 20 min at a power of 20 kW. After the treatment is completed, cool to room temperature under nitrogen protection. Grind the activated coal gangue after cooling to a particle size of less than 75 μm.

[0044] The precipitated calcium carbonate powder (average particle size D50 of 3 μm) and the silica aerogel powder are pre-mixed in a high-speed mixer at a mass ratio of 5:1 for 8 min. The pre-mixed material is fed into a radio frequency plasma reaction chamber. Argon gas is introduced as working gas, and the chamber pressure is maintained at 120 Pa. Turn on the radio frequency power and process for 30 min at a power of 80 W to make the aerogel depolymerize and deposit on the surface of the calcium carbonate particles under plasma excitation. After the treatment is completed, the obtained porous lightweight aggregate is collected in an inert atmosphere.

[0045] 20 parts of waterborne polyurethane resin, 3.6 parts of reactive isocyanate blowing agent and 0.2 parts of amphiphilic block copolymer dispersant are added into a high-speed dispersion kettle, and stirred at a speed of 800 rpm for 8 min to form a premix. Under continuous stirring, 40 parts of activated coal gangue powder and 30 parts of porous lightweight aggregate are slowly added in turn. 1.5 parts of plant fiber chopped material is added, and deionized water is slowly added while stirring. The speed is increased to 1800 rpm, and the slurry is continuously dispersed for 20 min to form a uniform and stable slurry without visible agglomerates, and water is added to adjust the solid content to 50%.

[0046] Preheat the mold to the target zoned temperature, the surface layer region temperature is 105℃, the middle layer region temperature is 75℃, and the inner layer region temperature is 95℃. The slurry is injected into the mold cavity at a uniform speed. Close the mold and keep it at the set zoned temperature for 10 minutes for foaming and self-assembly. After the holding period, the composite blank with a three-layer gradient density structure is removed from the mold. During the foaming process, a pulsed magnetic field is applied to the mold to orient the plant fibers along the thickness direction of the board. The surface layer region of the mold cavity is provided with a micron-scale groove structure. After the slurry is injected, a micro-pressure of 0.3 MPa is applied in the groove direction during the initial foaming stage to promote the oriented filling of the slurry into the grooves. During the foaming and self-assembly process, the internal pressure of the mold is monitored in real time. When the middle layer region pressure reaches the peak value and starts to drop, it is considered that the micro-foaming is basically completed.

[0047] The composite blank is conveyed under the LED-UV curing equipment. The surface of the board is irradiated and cured using a 395 nm LED array light source, and the irradiation energy is 400 mJ / cm 2 . The cured board is cooled by a cooling roller, and then wound online. The LED-UV curing process is divided into two stages: the first stage uses a 375 nm waveband light source for pre-curing to quickly shape the surface layer; the second stage uses a 395 nm waveband light source for main curing to ensure sufficient internal crosslinking. The printed surface of the board is subjected to corona treatment before winding to enhance the adhesion of the ink.

[0048] In the description of the present application, it should be understood that the terms "first", "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0049] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0050] In the present application, unless otherwise explicitly specified and limited, a first feature is "on" or "under" a second feature can mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature is "over", "above" and "on top of" a second feature can mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. A first feature is "under", "below" and "underneath" a second feature can mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is horizontally lower than the second feature.

[0051] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an embodiment", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are contained 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 appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples, without contradiction.

[0052] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and the person skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A method for preparing a printable packaging composite board based on coal gangue and calcium carbonate, characterized in that, Comprise: Step S1, the activation treatment of coal gangue, the coal gangue is placed in the nitrogen protection atmosphere with the flow rate of 2-5L / min, and microwave irradiation treatment with the power of 15-25kW and the time of 10-30min is carried out to realize the activation, then the activated coal gangue is ground to the particle size less than 75μm; Step S2, the preparation of porous lightweight aggregate: calcium carbonate powder and silica aerogel powder are mixed in the mass ratio of 5:1, and the pre-mixed material is sent into the radio frequency plasma reaction cavity under the action of radio frequency plasma with the power of 50-100W and the time of 20-40min, so that the silica aerogel is in-situ coated on the surface of calcium carbonate particles to form the porous lightweight aggregate; Step S3, the preparation of mixed slurry, 35-45 parts of the activated coal gangue powder obtained in step S1, 25-35 parts of the porous lightweight aggregate obtained in step S2, 18-23 parts of water-based polyurethane resin, 3.0-4.5 parts of reactive isocyanate foaming agent, 0.5-2.0 parts of plant fiber short cut and 0.1-0.3 parts of amphiphilic block copolymer dispersant are blended, and water is added to adjust the solid content to 45-55% to form a uniform slurry; Step S4, gradient foaming and molding, the slurry obtained in step S3 is injected into a mold with a partitioned independent temperature control function; the surface layer region temperature of the mold is set to 100-110℃, the middle layer region temperature is set to 70-80℃, and the inner layer region temperature is set to 90-100℃; heating is carried out in this partitioned gradient temperature field to make the slurry undergo micro-foaming reaction and component self-assembly simultaneously to form a three-layer composite structure with a density gradient; Step S5, curing and shaping, the three-layer composite structure obtained in step S4 is irradiated with LED-UV light with a wavelength of 365-405 nm and an irradiation energy of 300-500 mJ / cm 2 , and then wound up.

2. The method of claim 1, wherein the method is characterized by, The step S1 specifically comprises: Step S1.1, crushing the blocky coal gangue to a particle size less than 5cm; Step S1.2, placing the crushed coal gangue in a microwave reactor and replacing the air with nitrogen; Step S1.3, starting the microwave generator and irradiating for 10-30min under the power of 15-25kW; Step S1.4, after the treatment, cooling to room temperature under the protection of nitrogen; Step S1.5, grinding the cooled activated coal gangue to ≤75μm.

3. The method of claim 1, wherein the method is characterized by, The step S2 specifically comprises: Step S2.1, pre-mixing calcium carbonate powder and silica aerogel powder in a high-speed mixer in a mass ratio of 5:1 for 5-10min; Step S2.2, feeding the pre-mixed material into a radio frequency plasma reaction cavity; Step S2.3, introducing argon as working gas to maintain the cavity pressure at 50-200Pa; Step S2.4, turning on the radio frequency power and treating for 20-40min under the power of 50-100W to make the aerogel depolymerize and deposit on the surface of calcium carbonate particles under the excitation of plasma; Step S2.5, after the treatment, collecting the obtained porous lightweight aggregate in an inert atmosphere.

4. The method of claim 1, wherein the method is characterized by, The step S3 specifically comprises: Step S3.1, adding water-based polyurethane resin, reactive isocyanate foaming agent and amphiphilic block copolymer dispersant into a high-speed dispersion kettle, stirring at a speed of 500-1000rpm for 5-10min to form a pre-mixed liquid; Step S3.2, under continuous stirring, sequentially and slowly adding activated coal gangue powder and porous lightweight aggregate; Step S3.3, plant fiber short-cutting material is added, and deionized water is slowly added while stirring; Step S3.4, the rotation speed is increased to 1500-2000 rpm, and the dispersion is continuously performed for 15-30 min until a uniform and stable slurry without visible agglomerates is formed.

5. The method of claim 1, wherein the method is characterized by: Step S4 specifically comprises: Step S4.1, preheat the mold to the target partition temperature; Step S4.2, the slurry obtained in step S3 is uniformly injected into the mold cavity; Step S4.3, close the mold, and keep foaming and self-assembly at the set partition temperature for 5-15 min; Step S4.4, after the holding time ends, the mold is opened, and the composite blank with a three-layer gradient density structure is taken out.

6. The method of claim 1, wherein the method is characterized by: The step S5 specifically comprises: Step S5.1, the composite blank obtained in step (d) is conveyed below the LED-UV curing equipment; Step S5.2, a 395 nm LED array light source is used to irradiate and cure the surface of the plate; Step S5.3, the cured plate is cooled by a cooling roller, and then wound online.

7. The method of claim 1, wherein the method is characterized by: The coal gangue used in the step S1 is subjected to magnetic separation and iron removal before crushing, so that the content of ferromagnetic impurities is reduced to ≤0.5 wt%; the calcium carbonate powder used in the step S2 is precipitated calcium carbonate, and the average particle size D50 is 1-5 μm.

8. The method of claim 5, wherein the method further comprises the step of: Before the step S4.4, a pulse magnetic field is applied to the mold during foaming, so that the plant fibers are oriented and arranged along the thickness direction of the plate. ​ 9. The method of claim 5, wherein the method further comprises: The mold in the step S4.1 is provided with a micron-level groove structure in the surface layer area of the cavity; after the slurry is injected, a micro-pressure of 0.1-0.5 MPa is applied in the groove direction before or at the initial stage of foaming, so as to promote the directional filling of the surface layer slurry in the groove; ​ In the step S4.3, the internal pressure of the mold is monitored in real time during the foaming and self-assembly process; when the pressure in the middle layer area reaches the peak value and starts to decrease, it is considered that the micro-foaming is basically completed.

10. The method of claim 6, wherein the method is characterized by: In the step S5.1, the LED-UV curing process is divided into two stages: First stage: pre-curing is performed using a 365-385 nm waveband light source to quickly shape the surface layer; Second stage: main curing is performed using a 395-405 nm waveband light source to ensure sufficient crosslinking in the interior; In the step S5.3, the printed surface of the plate is subjected to corona treatment before winding.

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