Preparation method of high-hardness fire-retardant ultra-thin fiberboard

Abstract

The application discloses a preparation method of high-hardness flame-retardant ultra-thin fiberboard and belongs to the technical field of fiberboard production, which comprises the following steps: step one, biomass fiber preparation; step two, inorganic mineral powder is modified by a coupling agent to obtain modified reinforcing powder, or the obtained modified reinforcing powder is further added into an aqueous solution containing metal ions to prepare a composite additive; step three, fiber sizing: an adhesive and the modified reinforcing powder, or the adhesive and the composite additive, or the adhesive, a synergistic flame retardant and the composite additive are added to the surface of the biomass fiber; step four, drying of the obtained biomass fiber; and step five, the dried fiber is subjected to paving, pre-pressing and hot pressing to prepare the high-hardness flame-retardant ultra-thin fiberboard. The application can enhance the flame-retardant performance of the ultra-thin fiberboard and improve the surface hardness and other physical and mechanical properties of the fiberboard.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of artificial board production, in particular to the technical field of fiberboard production, and especially to a preparation method of high-hardness and flame-retardant ultra-thin fiberboard. BACKGROUND

[0002] The ultra-thin fiberboard is widely used in the field of decoration of artificial boards such as particle board and plywood. In this field of decoration, precious tree species thin veneer, melamine impregnated decorative paper, resin film and other materials are mainly used for veneer processing. With the development of the artificial board industry, the existing technology has developed ultra-thin fiberboard with a thickness of less than 1.5 mm, which has the advantages of smooth surface and can be cut to the required width, and can replace large-format natural wood veneer, technical wood veneer and other veneer substrates, and has been well developed in the field of particle board and plywood veneer, greatly expanding the new uses and new fields of fiberboard. However, with the increasing demand and application scenarios of ultra-thin fiberboard, such as application in electronic circuit printing pad and packaging, some problems have been gradually found. The thickness standards of ultra-thin fiberboard for electronic circuit printing pad include 0.4 mm, 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm, etc. However, the hardness of the ultra-thin fiberboard is low, and the flame-retardant effect is poor, thereby limiting its application field. Therefore, improving the hardness and flame-retardant performance of the ultra-thin fiberboard has great significance for expanding its application field, and is also one of the important ways for the development of high-value and differentiated products of the fiberboard industry.

[0003] Through retrieval, there are few patent technologies related to improving the hardness and flame-retardant performance of ultra-thin fiberboard. High-hardness and flame-retardant ultra-thin fiberboard for electronic circuit printing pad and packaging field is rare, so it is necessary to design a high-hardness and flame-retardant ultra-thin fiberboard which is easy to mass-produce and its industrial production process. SUMMARY

[0004] In view of the above problems, one object of the present application is to provide a preparation method of high-hardness and flame-retardant ultra-thin fiberboard with high surface hardness and good flame-retardant performance.

[0005] In order to achieve the object and other advantages of the present application, the preparation method of high-hardness and flame-retardant ultra-thin fiberboard provided by the present application comprises the following steps:

[0006] Step one, biomass fiber preparation:

[0007] In one embodiment, small-diameter timber, branch timber, bamboo timber and wood processing residues are selected as biomass fiber raw materials, and after peeling, slicing, washing, cooking and hot grinding, biomass fiber slurry is prepared;

[0008] Step two, preparation of composite additives:

[0009] In one embodiment, the inorganic mineral powder is modified by a coupling agent to obtain a modified reinforcing powder, which is then added to an aqueous solution containing metal ions, and after being uniformly stirred, a composite additive is prepared;

[0010] Step three, fiber sizing:

[0011] In one embodiment, after obtaining the biomass fiber slurry by cooking and hot grinding, the fiber slurry is fed into a sizing pipeline or a sizing device, and then a metering pump is used to atomize and spray the adhesive, the synergistic flame retardant and the composite additive through a nozzle provided on the pipeline, and uniformly spray them onto the surface of the fibers.

[0012] Step four, fiber drying:

[0013] In one embodiment, the fibers are dried by a hot air pipeline.

[0014] Step five, preparation of high-hardness flame-retardant ultra-thin fiberboard:

[0015] In one embodiment, the obtained dried fibers are subjected to paving, pre-pressing, surface humidification, hot pressing, edge cutting, heat dissipation and aging, and sanding to prepare the high-hardness flame-retardant ultra-thin fiberboard.

[0016] Preferably, the present application provides four adding methods of the composite additive. The first method is that the composite additive is uniformly mixed with the adhesive in step three, and then is applied multiple times in the sizing pipeline or the sizing device; the second method is that the composite additive and the adhesive are alternately applied multiple times in the sizing pipeline or the sizing device, respectively; the third method is that the modified reinforcing powder or the modified reinforcing powder and the flame retardant are uniformly stirred and applied in the powder stirring device under the cyclone separator after the fibers are dried; the fourth method is that the water suspension of the composite additive is used to spray the upper and lower surfaces of the board blank by high-pressure spraying in the surface humidification process after pre-pressing.

[0017] Further, the biomass fibers in step one of the present application are fibers of biomass materials such as eucalyptus, poplar, Chinese fir, miscellaneous wood, bamboo, wheat straw, cotton straw or bagasse. Preferably, the fibers are of eucalyptus, poplar, Chinese fir or miscellaneous wood, and the bark content is not more than 5% of the total fiber content.

[0018] Further, a waterproofing agent is added in the hot grinding stage of step one or the sizing stage of step three of the present application to improve the moisture resistance of the product. The waterproofing agent is a 50% high-solid paraffin emulsion, and the addition amount is 1-3% of the mass of the absolutely dry fibers.

[0019] Further, the inorganic mineral powder in step two of the present application includes light calcium carbonate, heavy calcium carbonate, quartz powder (silicon dioxide), aluminum oxide, montmorillonite, bentonite, kaolin, attapulgite or aluminum silicate powder and the like. The particle size of the inorganic mineral powder is 100-800 mesh; if the mesh number is too large, the cost is high, and if the particle size is too small, it is not easy to disperse, and after paving, it is easy to deposit on the lower surface of the slab, and the glue consumption is large, and powder aggregation and glue spot defects are easy to occur, thereby reducing the mechanical properties of the slab; if the mesh number of the inorganic powder is too small, the particle size is too large, and due to the action of gravity, it is easy to precipitate in the aqueous dispersion, resulting in uneven application of the reinforcing powder, and due to the large particle size, it is not conducive to the construction of a uniform and continuous glue network structure of the fibers and adhesives in the slab after paving. At the same time, the large particle size of the powder may cause wear to the paving belt and hot pressing equipment. Preferably, the particle size of the inorganic mineral powder is 325-400 mesh.

[0020] Further, the coupling agent in step two of the present application includes any one or more of silane coupling agents KH-550, KH-560, KH-570 and titanium coupling agents 110, 201, 401. Preferably, silane coupling agent KH-560 is used.

[0021] Further, the method for treating the inorganic mineral powder with the coupling agent in step two of the present application includes normal temperature aqueous phase stirring treatment; or 60-90°C heating and stirring treatment; or diluting the coupling agent 5 times with 95% ethanol solution, and then adding it dropwise into the inorganic mineral powder in a high-speed mixer for high-speed mixing and stirring treatment, with the temperature controlled at 90-120°C. Preferably, 60-90°C heating and stirring treatment is used. The amount of coupling agent used is 0.5-5% of the total weight of the inorganic mineral material powder.

[0022] Further, the metal ion in step two of the present application is a metal ion that can form a metal complex; it is obtained by an aqueous solution of metal chloride, which includes any one or more of ferric chloride, aluminum chloride, zinc chloride, titanium tetrachloride, copper chloride, ferrous chloride, manganese dichloride, nickel chloride and calcium chloride. Among them, aluminum chloride is preferably used because it is low in cost and safe and environmentally friendly. The amount of metal chloride added is 0.5-1.5% of the mass of the absolutely dry fibers.

[0023] Further, the main components of the synergistic flame retardant in step three of the present application are 3.5 zinc borate, melamine and phytic acid; or 3.5 zinc borate, ammonium polyphosphate and phytic acid; or 3.5 zinc borate, ammonium polyphosphate, melamine and phytic acid. Phytic acid has strong chelating effect and can form coordination with metal ions, so it can fix metal ions and improve their adhesion to the adhesive, which is beneficial to improve the easy loss problem of inorganic flame retardant and help the synergistic flame retardation of metal chloride and flame retardant. The synergistic flame retardant is prepared from the following raw materials in parts by weight: 3.5 zinc borate 3-10 parts, melamine 3-10 parts, phytic acid 1-5 parts; or 3.5 zinc borate 3-8 parts, ammonium polyphosphate 5-8 parts, phytic acid 1-3 parts; or 3.5 zinc borate 3-8 parts, ammonium polyphosphate 3-5 parts, melamine 1-3 parts, phytic acid 1-3 parts; preferably 3.5 zinc borate 5-8 parts, melamine 3-5 parts, phytic acid 1-3 parts. The addition amount of the synergistic flame retardant is 5-30% of the mass of the absolutely dry fiber.

[0024] Further, the adhesive in step three of the present application includes urea-formaldehyde resin adhesive (UF), melamine urea-formaldehyde resin adhesive (MUF), isocyanate adhesive (MDI) and soybean protein adhesive. Among them, the preferred are melamine urea-formaldehyde resin adhesive and isocyanate adhesive. Metal ions can form coordination bonds with amide groups (—CO—NH—) in MUF, hydroxyl groups (—OH) in biomass fibers, etc., improve the dispersibility of modified reinforcing powder and the cross-linking degree of adhesive, and further improve the surface hardness of the super-thin fiber board.

[0025] Further, the addition amount of the composite aid in step three of the present application is 3-20% of the mass of the absolutely dry fiber, and more preferably the addition amount is 5-12%; if MUF adhesive is used, the addition amount is 8-16% of the total mass of the absolutely dry fiber and inorganic mineral powder, and more preferably the addition amount is 10-14%; if MDI adhesive is used, the addition amount is 3-5% of the total mass of the absolutely dry fiber and inorganic mineral powder, and more preferably the addition amount is 3-4%. If the sizing amount is too low, the adhesive cannot be uniformly distributed on the surface of the fiber and powder, resulting in insufficient mechanical properties of the board and large thickness rebound after hot pressing of the board; too high amount of adhesive will also increase the production cost and glue spot defects on the board surface.

[0026] Further, the fiber sizing method in step three of the present application is that the composite aid and the adhesive are mixed uniformly and then applied in multiple times in the sizing pipe or glue mixing device; or the composite aid and the adhesive are alternately applied in multiple times in the sizing pipe or glue mixing device, respectively.

[0027] Further, the hot air pipeline in step four of the present application is used for drying, the drying medium temperature in the drying pipeline is 110-250℃, and preferably 130-150℃, and finally the moisture content of the fiber is controlled at 9-12%.

[0028] Further, the paving method of step five of the present application comprises one of mechanical forming, air flow forming or mechanical-air flow forming.

[0029] Further, the hot pressing temperature of step five of the present application is 180-210 DEG C, and a four-stage hot pressing method is adopted: the first stage is a contact zone, the hot pressing unit pressure is 0.03-0.1 MPa, and it is mainly used for the smooth entry of the slab into the hot press; the second stage, the hot pressing unit pressure is 4.0-6.0 MPa, and it is mainly used for the thickness determination of the slab; the third stage, the hot pressing unit pressure is 0.8-1.2 MPa, and it is mainly used for the removal of the water vapor evaporated in the hot pressing process to prevent defects such as bubbling and board explosion; the fourth stage, the hot pressing unit pressure is 1.0-3.5 MPa, and it is mainly used for the complete curing and crosslinking of the adhesive to improve the strength of the slab.

[0030] Further, the sanding of step five is double-sided sanding with a remaining amount of 0.05-0.15 mm, and it is used for removing the pre-cured layer on the surface of the slab.

[0031] Further, the adding method of the composite adjuvant of the present application is optimal, and the composite adjuvant and the adhesive are added in the glue applying pipeline or the glue mixing device respectively and multiple times.

[0032] Further, the biomass fibers are glued with the adhesive in the present application, and the fibers to which only the adhesive is applied without the composite adjuvant and the synergistic flame retardant are obtained, the fibers to which only the adhesive is applied without the composite adjuvant and the synergistic flame retardant after drying are used as the core layer, the dried fibers prepared in step four are used as the two surface layers, and the fibers to which only the adhesive is applied without the composite adjuvant and the synergistic flame retardant and the dried fibers prepared in step four are layered and paved, and the mass ratio of the fibers to which only the adhesive is applied without the composite adjuvant and the synergistic flame retardant to the dried fibers prepared in step four is 1:1; or all the dried fibers prepared in step four are used for paving.

[0033] The present application at least includes the following beneficial effects:

[0034] 1. The present application forms coordination crosslinking with metal ions, biomass fibers, adhesive and inorganic mineral powder modified by coupling agent, is used for dispersing inorganic mineral powder and improving the interface compatibility of inorganic mineral powder and biomass fibers, and uses inorganic mineral powder as reinforcing material to improve the surface hardness of the slab, and prepares high-hardness ultra-thin fiber board.

[0035] 2. The inorganic mineral powder used in the present application belongs to one kind of covering type flame retardant, and through the preparation of synergistic flame retardant and the use of inorganic mineral powder and metal chloride by multiple flame retardant mechanisms, the fiber board surface is rapidly dehydrated and carbonized to form a carbonized layer, the smoldering phenomenon of the slab is avoided, and the emission of toxic gas is reduced. The high-hardness flame-retardant ultra-thin fiber board prepared in the present application can realize the effect of self-extinguishing in the air.

[0036] 3, The metal chloride and zinc borate used in the application have certain insect prevention and corrosion prevention effects, so that the prepared ultra-thin fiber board has certain insect prevention and corrosion prevention effects.

[0037] 4, The high-hardness flame-retardant ultra-thin fiber board prepared by the preparation method has a thickness of 0.8-1.4mm, a density of 900-1100 kg / m 3 , a moisture content of 5-12%, and the related physical and mechanical properties meet the requirements of T / CNFPIA 3007-2019 "Ultra-thin high-density fiber board" group standard.

[0038] Other advantages, objects and features of the application will be embodied in part by the following description, and part will be understood by those skilled in the art through research and practice of the application. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 The mechanism diagram of the preparation of the high-hardness flame-retardant ultra-thin fiber board by the metal ion coordination enhancement of the application.

[0040] Figure 2 The micro-morphology and element analysis diagram of the sized fiber of Comparative Example 1 and Example 2; wherein (a) and (b) are micro-morphology diagrams of the sized fiber of Comparative Example 1 and Example 2, respectively, (c) (d) (e) (f) are element analysis diagrams of C, O, Si and Al based on diagram (b).

[0041] Figure 3 The surface diagram of the ultra-thin fiber board of Comparative Example 3; wherein (a) is the upper surface, and (b) is the lower surface. DETAILED DESCRIPTION

[0042] The application will be further described in detail below with reference to the examples, so that those skilled in the art can implement the application according to the description.

[0043] Example 1

[0044] A preparation method of a high-hardness flame-retardant ultra-thin fiber board, comprising:

[0045] S1: Selecting eucalyptus wood as a biomass fiber raw material, and preparing fiber slurry after peeling, slicing, washing, cooking and hot grinding.

[0046] S2: First, the silane coupling agent KH-560 is prepared into a water solution with a mass fraction of 10%, and heated and stirred at 70℃ for 30min. Then SiO2 powder is added and heated and stirred for 1h, and finally the modified reinforcing powder is obtained by filtration and drying. The addition amount of the silane coupling agent KH-560 is 5% of the mass of the SiO2 powder. The modified reinforcing powder has a mesh size of 325 mesh.

[0047] S3: The modified reinforcing powder and melamine modified urea-formaldehyde resin adhesive are uniformly and alternately applied to the fiber slurry through the sizing device. The amount of modified reinforcing powder is 10% of the mass of the dry fiber; the amount of MUF adhesive is 12% of the total mass of the dry fiber and modified reinforcing powder.

[0048] S4: The sized fiber slurry is dried through a hot air pipeline, with the drying medium temperature in the pipeline being 130-150°C, so that the final moisture content is 8%-12%.

[0049] S5: The obtained dried fiber is subjected to assembly, pre-pressing, hot pressing, edge cutting, heat dissipation and aging, and sanding to produce the high-hardness ultra-thin fiberboard. The hot pressing temperature is 180-210°C, and a four-stage hot pressing method is adopted: the first stage is a contact zone, the hot pressing unit pressure is 0.03-0.1 MPa, and it is mainly used for the smooth entry of the board into the hot press; the second stage, the hot pressing unit pressure is 4.0-6.0 MPa, and it is mainly used for the thickness setting of the board; the third stage, the hot pressing unit pressure is 0.8-1.2 MPa, and it is mainly used for the removal of water vapor evaporated during hot pressing to prevent defects such as bubbling and board explosion; the fourth stage, the hot pressing unit pressure is 1.0-3.5 MPa, and it is mainly used for the complete curing and crosslinking of the adhesive to improve the strength of the board. The hot pressing speed of the continuous hot press is 1400-1600 mm / s. The sanding is double-sided sanding with a surplus of 0.05-0.15 mm.

[0050] Example 2

[0051] (Difference from Example 1: the modified reinforcing powder is compounded with metal ion AlCl3 as a composite additive.)

[0052] A method for preparing a high-hardness flame-retardant ultra-thin fiberboard, comprising:

[0053] S1: Eucalyptus wood is selected as the biomass fiber raw material, and after peeling, slicing, washing, cooking and hot grinding, a fiber slurry is prepared.

[0054] S2: First, the silane coupling agent KH-560 is prepared into a 10% mass fraction aqueous solution, heated and stirred at 70°C for 30 min. Then SiO2 powder is added and heated and stirred for 1 h, and finally the modified reinforcing powder is obtained by filtration and drying. The addition amount of the silane coupling agent KH-560 is 5% of the mass of the SiO2 powder. The modified reinforcing powder has a mesh size of 325 mesh.

[0055] S3: AlCl3 particles are prepared into a 5% mass fraction aqueous solution. The above modified reinforcing powder is added to the AlCl3 solution to prepare a composite additive suspension.

[0056] S4: The composite adjuvant and melamine modified urea-formaldehyde resin adhesive are uniformly and alternately applied to the fiber slurry through the glue application device. The modified reinforcing powder is 10% of the mass of the dry fiber; the AlCl3 is 1% of the mass of the dry fiber; and the MUF adhesive is 12% of the total mass of the dry fiber and the modified reinforcing powder.

[0057] S5: The glued fiber slurry is dried through a hot air pipeline, the drying medium temperature in the pipeline is 130-150℃, and the final moisture content is 8%-12%.

[0058] S6: The obtained dried fiber is subjected to assembly, pre-pressing, hot pressing, edge cutting, heat dissipation and aging, and sanding to produce the high-hardness ultra-thin fiberboard. The hot pressing temperature is 180-210℃, and a four-stage hot pressing method is adopted: the first stage is a contact zone, the hot pressing unit pressure is 0.03-0.1MPa, and it is mainly used for the smooth entry of the board into the hot press; the second stage, the hot pressing unit pressure is 4.0-6.0MPa, and it is mainly used for the thickness of the board; the third stage, the hot pressing unit pressure is 0.8-1.2MPa, and it is mainly used for removing the water vapor evaporated during hot pressing to prevent defects such as bubbling and board explosion; the fourth stage, the hot pressing unit pressure is 1.0-3.5MPa, and it is mainly used for the complete curing and crosslinking of the adhesive to improve the strength of the board. The hot pressing speed of the continuous hot press is 1400-1600mm / s. The sanding is double-sided sanding with a surplus of 0.05-0.15mm.

[0059] Example 3

[0060] (Difference from Example 2: the inorganic mineral powder is Al2O3.)

[0061] A method for preparing a high-hardness flame-retardant ultra-thin fiberboard, comprising:

[0062] S1: Eucalyptus wood is selected as the biomass fiber raw material, and after peeling, slicing, washing, cooking and hot grinding, a fiber slurry is prepared.

[0063] S2: First, the silane coupling agent KH-560 is prepared into a 10% mass fraction aqueous solution, heated and stirred at 70℃ for 30min. Then Al2O3 powder is added and heated and stirred for 1h, and finally the modified reinforcing powder is obtained by filtration and drying. The addition amount of the silane coupling agent KH-560 is 5% of the mass of the Al2O3 powder. The modified reinforcing powder has a mesh number of 325.

[0064] S3: AlCl3 particles are prepared into a 5% mass fraction aqueous solution. The modified reinforcing powder is added to the AlCl3 solution to prepare a composite adjuvant suspension.

[0065] S4: The waterproof agent, the composite adjuvant and the melamine modified urea-formaldehyde resin adhesive are uniformly and alternately applied to the fiber slurry through the sizing device. The modified reinforcing powder is 10% of the mass of the dry fiber; the AlCl3 is 1% of the mass of the dry fiber; the MUF adhesive is 12% of the total mass of the dry fiber and the modified reinforcing powder.

[0066] S5: The sized fiber slurry is dried through a hot air pipeline, the drying medium temperature in the pipeline is 130-150℃, and the final moisture content is 8%-12%.

[0067] S6: The obtained dried fiber is subjected to assembly, pre-pressing, hot pressing, edge cutting, heat dissipation and aging and sanding to produce the high-hardness ultra-thin fiberboard. The hot pressing temperature is 180-210℃, and a four-stage hot pressing method is adopted: the first stage is a contact zone, the hot pressing unit pressure is 0.03-0.1MPa, and it is mainly used for the smooth entry of the board into the hot press; the second stage, the hot pressing unit pressure is 4.0-6.0MPa, and it is mainly used for the thickness setting of the board; the third stage, the hot pressing unit pressure is 0.8-1.2MPa, and it is mainly used for the removal of the water vapor evaporated during the hot pressing process to prevent defects such as bubbling and board explosion; the fourth stage, the hot pressing unit pressure is 1.0-3.5MPa, and it is mainly used for the complete curing and crosslinking of the adhesive to improve the strength of the board. The hot pressing speed of the continuous hot press is 1400-1600mm / s. The sanding is double-sided sanding with a surplus of 0.05-0.15mm.

[0068] Example 4

[0069] (Difference from Example 2: a synergistic flame retardant is used.)

[0070] A method for preparing a high-hardness flame-retardant ultra-thin fiberboard, comprising:

[0071] S1: Eucalyptus is selected as the biomass fiber raw material, and after peeling, slicing, washing, cooking and hot grinding, a fiber slurry is prepared.

[0072] S2: First, the silane coupling agent KH-560 is prepared into a 10% mass fraction aqueous solution, heated and stirred at 70℃ for 30min. Then SiO2 powder is added and heated and stirred for 1h, and finally the modified reinforcing powder is obtained by filtration and drying and crushing. The addition amount of the silane coupling agent KH-560 is 5% of the mass of the SiO2 powder. The modified reinforcing powder has a mesh number of 325.

[0073] S3: AlCl3 particles are prepared into a 5% mass fraction aqueous solution. The modified reinforcing powder is added to the AlCl3 solution to prepare a composite adjuvant suspension.

[0074] S4: The waterproof agent, synergistic flame retardant, composite adjuvant and melamine modified urea-formaldehyde resin adhesive are alternately and uniformly applied to the fiber slurry through the sizing device. The amount of synergistic flame retardant is 8% of the mass of the absolute dry fiber; the amount of modified reinforcing powder is 10% of the mass of the absolute dry fiber; the amount of AlCl3 is 1% of the mass of the absolute dry fiber; the amount of MUF adhesive is 12% of the total mass of the absolute dry fiber and modified reinforcing powder. The synergistic flame retardant is prepared from the following raw materials by weight: 3.5 zinc borate 5-8 parts, melamine 3-5 parts, phytic acid 1-3 parts.

[0075] S5: The sized fiber slurry is dried through a hot air pipeline, and the drying medium temperature in the pipeline is 130-150℃, so that the final moisture content is 8%-12%.

[0076] S6: The obtained dried fiber is subjected to assembly, pre-pressing, hot pressing, edge cutting, heat dissipation and aging, and sanding to produce the high-hardness ultra-thin fiberboard. The hot pressing temperature is 180-210℃, and a four-stage hot pressing method is adopted: the first stage is a contact zone, the hot pressing unit pressure is 0.03-0.1 MPa, and it is mainly used for the smooth entry of the board into the hot press; the second stage, the hot pressing unit pressure is 4.0-6.0 MPa, mainly for thickness setting of the board; the third stage, the hot pressing unit pressure is 0.8-1.2 MPa, mainly for removing the water vapor evaporated during hot pressing to prevent defects such as bubbling and board explosion; the fourth stage, the hot pressing unit pressure is 1.0-3.5 MPa, mainly to allow the adhesive to completely cure and crosslink to improve the strength of the board. The hot pressing speed of the continuous hot press is 1400-1600 mm / s. The sanding is double-sided sanding with a remaining amount of 0.05-0.15 mm.

[0077] Example 5

[0078] (Difference from Example 4: fibers to which only the sizing agent is applied without the composite adjuvant and synergistic flame retardant are also prepared, and the fibers to which only the sizing agent is applied without the composite adjuvant and synergistic flame retardant after drying are used as the core layer, and the modified fibers are used as the two surface layers for layered lamination.)

[0079] A method for preparing a high-hardness flame-retardant ultra-thin fiberboard, comprising:

[0080] S1: Eucalyptus is selected as the biomass fiber raw material, and after peeling, slicing, washing, cooking and hot grinding, a fiber slurry is prepared.

[0081] S2: First, silane coupling agent KH-560 was prepared into a 10% mass fraction aqueous solution, heated and stirred at 70°C for 30 min. Then SiO2 powder was added and heated and stirred for 1 h. Finally, the modified reinforcing powder was obtained by filtration and drying. The amount of silane coupling agent KH-560 added was 5% of the mass of SiO2 powder. The modified reinforcing powder had a mesh size of 325 mesh.

[0082] S3: AlCl3 particles were prepared into a 5% mass fraction aqueous solution. The modified reinforcing powder was added to the AlCl3 solution to form a composite additive suspension.

[0083] S4: The waterproofing agent, synergistic flame retardant, composite additive, and melamine modified urea-formaldehyde resin adhesive were applied alternately and uniformly to the fiber slurry through a sizing device to obtain a modified fiber slurry. The amount of synergistic flame retardant was 8% of the mass of the dry fiber; the amount of modified reinforcing powder was 10% of the mass of the dry fiber; the amount of AlCl3 was 1% of the mass of the dry fiber; and the amount of MUF adhesive was 12% of the total mass of the dry fiber and modified reinforcing powder. The synergistic flame retardant was prepared from the following raw materials: 3.5 parts of zinc borate, 5-8 parts of melamine, and 1-3 parts of phytic acid.

[0084] The melamine modified urea-formaldehyde resin adhesive was applied uniformly to the fiber slurry through a sizing device to obtain a fiber slurry without the application of composite additives and synergistic flame retardants. The amount of MUF adhesive was 12% of the mass of the dry fiber.

[0085] S5: The modified fiber slurry after sizing and the fiber slurry without the application of composite additives and synergistic flame retardants were dried separately through a hot air pipeline. The drying medium temperature in the pipeline was 130-150°C, and the final moisture content was 8-12%. The modified dry fiber and the dry fiber without the application of composite additives and synergistic flame retardants were obtained.

[0086] S6: The dry fiber only sized without composite aid and synergistic flame retardant is taken as a core layer, and the modified dry fiber is taken as a surface layer to perform layered paving, and the mass ratio of the modified dry fiber to the dry fiber only sized without composite aid and synergistic flame retardant after drying is 1:1, and then after being subjected to assembly, pre-pressing, hot pressing, edge cutting, heat dissipation and aging and sanding, the high-hardness flame-retardant ultra-thin fiber board is prepared. The hot pressing temperature is 180-210℃, and a four-stage hot pressing method is adopted: the first stage is a contact zone, the hot pressing unit pressure is 0.03-0.1MPa, and it is mainly used for the board assembly to smoothly enter the hot press; the second stage, the hot pressing unit pressure is 4.0-6.0MPa, and it is mainly used for the thickness of the board; the third stage, the hot pressing unit pressure is 0.8-1.2MPa, and it is mainly used for removing the water vapor evaporated in the hot pressing process to prevent defects such as bubbling and board explosion; the fourth stage, the hot pressing unit pressure is 1.0-3.5MPa, and it is mainly used for the adhesive to be completely cured and crosslinked to improve the strength of the board. The hot pressing speed of the continuous hot press is 1400-1600mm / s. The sanding is double-sided sanding, and the allowance is 0.05-0.15mm.

[0087] Comparative Example 1

[0088] (Difference from Example 1: the reinforcing powder is not modified)

[0089] A preparation method of a high-hardness ultra-thin fiber board, comprising:

[0090] S1: Eucalyptus is selected as a biomass fiber raw material, and after being subjected to peeling, slicing, washing, cooking and hot grinding, a fiber slurry is prepared.

[0091] S2: The reinforcing powder (SiO2) and the melamine modified urea-formaldehyde resin adhesive are alternately and uniformly applied to the fiber slurry through a sizing device. The amount of the reinforcing powder is 10% of the mass of the absolutely dry fiber; and the amount of the MUF adhesive is 12% of the total mass of the absolutely dry fiber and the reinforcing powder.

[0092] S3: The sized biomass fiber is dried through a hot air pipeline to obtain a dry fiber, and the drying medium temperature in the drying pipeline is 130-150℃, so that the final moisture content is 8%-12%.

[0093] S4: The obtained dry fibers are subjected to assembly, pre-pressing, hot pressing, edge cutting, heat dissipation and aging, and sanding to produce the high-hardness ultra-thin fiberboard. The hot pressing temperature is 180-210°C, and a four-stage hot pressing method is adopted: the first stage is a contact zone, the hot pressing unit pressure is 0.03-0.1 MPa, and it is mainly used for the smooth entry of the board into the hot press; the second stage, the hot pressing unit pressure is 4.0-6.0 MPa, and it is mainly used for the thickness of the board; the third stage, the hot pressing unit pressure is 0.8-1.2 MPa, and it is mainly used to remove the water vapor evaporated during hot pressing to prevent defects such as bubbling and board explosion; the fourth stage, the hot pressing unit pressure is 1.0-3.5 MPa, and it is mainly to make the adhesive completely crosslinking and improve the strength of the board. The hot pressing speed of the continuous hot press is 1400-1600 mm / s. The sanding is double-sided sanding with a surplus of 0.05-0.15 mm.

[0094] Comparative Example 2

[0095] Different from Example 4, the modified reinforcing powder has a mesh size of 100 mesh, and the other steps are the same to produce the high-hardness flame-retardant ultra-thin fiberboard.

[0096] Comparative Example 3

[0097] Different from Example 4, the modified reinforcing powder has a mesh size of 800 mesh, and the other steps are the same to produce the high-hardness flame-retardant ultra-thin fiberboard.

[0098] Comparative Example 4

[0099] Different from Example 4, the adding method of the composite additive is replaced by: the composite additive is mixed uniformly with the adhesive, and then is applied in multiple times in the glue application pipeline or glue mixing device.

[0100] Comparative Example 5

[0101] Different from Example 4, the adding method of the composite additive is replaced by: after pre-pressing, the upper and lower surfaces of the board are treated by high-pressure spraying with the water suspension of the composite additive in the surface wetting process.

[0102] Data Analysis

[0103] Table 1 is the physical and mechanical properties of the ultra-thin fiberboard produced in the examples and comparative examples. It can be found from the surface Shore hardness test that the addition of inorganic mineral powder can significantly improve the hardness of the ultra-thin fiberboard. The performance of Example 1 is significantly improved compared with Comparative Example 1, which proves that the addition of coupling agent is beneficial to improve the interfacial compatibility of fibers and mineral powder. The internal bonding strength of Example 2 is improved, and the water absorption thickness expansion rate is decreased compared with Example 1, which proves that the metal ions improve the crosslinking degree of the adhesive through coordination, making the board more dense, thereby improving the performance of the ultra-thin board. According to the formula of the composite additive, the content of the metal ions is 0.5-1.5%, and the content of the coupling agent is 0.5-1.5%. The content of the metal ions is too low, and the content of the coupling agent is too high, which will affect the performance of the ultra-thin fiberboard. Figure 2The analysis can show that the inorganic mineral powder is firmly adhered to the surface of the fiber and is uniformly dispersed, and the metal ions are distributed in the fiber through coordination. Example 4 can reach an limiting oxygen index value of 31% by adding a small amount of synergistic flame retardant under the condition of similar other physical and mechanical properties, which is increased by 48% compared with Comparative Example 1 and is significantly higher than other examples, indicating that the prepared ultra-thin fiber board has good flame retardance. Example 5 has excellent physical and mechanical properties while maintaining high surface hardness and good flame retardance by means of layered paving. Comparative Example 3 has most of the inorganic mineral powder deposited on the lower surface of the ultra-thin fiber board because the mesh size of the inorganic mineral powder is too large, and the hardness (HD) of the upper surface is 71 and the hardness of the lower surface is 80, which shows that the difference between the upper and lower surfaces is too large, Figure 3 Figure 1 is a surface diagram of the ultra-thin fiber board of Comparative Example 3; wherein (a) is the upper surface and (b) is the lower surface. In Comparative Example 4, the composite additive is mixed uniformly with the adhesive, the viscosity of the adhesive increases, and the curing time is shortened. The ultra-thin fiber board of Comparative Example 5 is prone to bubbling defects, and the steel belt of the press is worn more.

[0104] Table 1 Physical and mechanical properties of the ultra-thin fiber board prepared in the examples and comparative examples

[0105]

[0106] Although the embodiments of the present application have been disclosed as above, it is not limited to the use listed in the specification and embodiments. It can be fully applied to various fields suitable for the present application. Additional modifications can be easily realized by those skilled in the art.

Claims

1. A method for preparing a high-hardness flame-retardant ultra-thin fiberboard, characterized in that: include: Step 1: preparing biomass fibers; Step 2: The inorganic mineral powder is modified by a coupling agent to obtain a modified and reinforced powder, and the obtained modified and reinforced powder is further added to an aqueous solution containing metal ions to prepare a composite additive; Step 3, fiber sizing: adding adhesive, synergistic flame retardant and composite additives to the surface of the biomass fiber; Step 4: drying the obtained biomass fibers; Step 5: The obtained dried fibers are paved, pre-pressed and hot-pressed to form the high-hardness flame-retardant ultra-thin fiberboard; The inorganic mineral powder includes any one or more of light calcium carbonate, heavy calcium carbonate, silicon dioxide, aluminum oxide, montmorillonite, bentonite, kaolin, attapulgite and aluminum silicate powder; the particle size of the inorganic mineral powder is 100-800 mesh; The metal ions are metal ions capable of forming metal complexes; the metal ions are obtained by using an aqueous solution of metal chloride, the metal chloride including any one or more of ferric chloride, aluminum chloride, zinc chloride, titanium tetrachloride, copper chloride, ferrous chloride, manganese dichloride, nickel chloride and calcium chloride; the amount of metal chloride added is 0.5-1.5% of the mass of the absolute dry fiber; The synergistic flame retardant is prepared from the following raw materials in parts by weight: 5-8 parts of 3.5-hydrated zinc borate, 3-5 parts of melamine, and 1-3 parts of phytic acid; or 5-8 parts of 3.5-hydrated zinc borate, 3-5 parts of ammonium polyphosphate, and 1-3 parts of phytic acid; or 3-8 parts of 3.5-hydrated zinc borate, 3-5 parts of ammonium polyphosphate, 1-3 parts of melamine, and 1-3 parts of phytic acid; the added amount of the synergistic flame retardant is 5-30% of the absolute dry fiber mass.

2. The method for preparing a high-hardness flame-retardant ultra-thin fiberboard according to claim 1, wherein: The adding method of the composite additive includes any one of the following: 1) after the composite additive and the adhesive are evenly mixed, they are applied in multiple times in the gluing pipe or the glue mixing device; 2) the composite additive and the adhesive are applied alternately in the gluing pipe or the glue mixing device respectively for multiple times; 3) the modified reinforced powder or the modified reinforced powder and the flame retardant are stirred and evenly applied at the flame retardant adding equipment below the cyclone separator in the paving molding process; 4) after pre-pressing, the upper and lower surfaces of the slab are subjected to high-pressure spray treatment using a water suspension of the composite additive in the surface wetting process.

3. The method for preparing a high-hardness flame-retardant ultra-thin fiberboard according to claim 1, wherein: The coupling agent is any one or more of silane coupling agents KH-550, KH-560, KH-570 and titanate coupling agents 110, 201, and 401.

4. The method for preparing a high-hardness flame-retardant ultra-thin fiberboard according to claim 3, wherein: The method for treating the inorganic mineral powder with the coupling agent is heating and stirring at 60-90° C.; the amount of the coupling agent used is 0.5-5% of the total weight of the inorganic mineral powder.

5. The method for preparing a high-hardness flame-retardant ultra-thin fiberboard according to claim 1, wherein: In step three, the fiber sizing method is to mix the composite additive and the adhesive evenly and then apply them multiple times in the sizing pipe or the glue mixing device; or to apply the composite additive and the adhesive alternately multiple times in the sizing pipe or the glue mixing device.

6. The method for preparing a high-hardness flame-retardant ultra-thin fiberboard according to claim 1, wherein: At the same time, an adhesive is used to apply glue to the biomass fiber to obtain a fiber that is only applied with glue but not applied with a composite additive and a synergistic flame retardant. After drying, the fiber that is only applied with glue but not applied with a composite additive and a synergistic flame retardant is used as a core layer; the dry fiber obtained according to claim 1 is used as two surface layers, and layered laying is performed. The mass ratio of the fiber that is only applied with glue but not applied with a composite additive and a synergistic flame retardant to the dry fiber obtained according to claim 1 is 1:1; Or all the dry fibers obtained according to claim 1 are used for paving.

Images