CN115847567A - Flexible formaldehyde-free fiberboard and manufacturing method thereof - Google Patents

Abstract

The invention relates to a flexible formaldehyde-free fiberboard and a manufacturing method thereof, belonging to the field of manufacturing of functional composite materials and the field of processing of artificial boards. The flexible formaldehyde-free fiberboard is composed of special fibers and a flexible adhesive system, wherein the special fibers comprise wood, bamboo, straws and/or straw fibers, and the flexible adhesive system comprises an isocyanic acid radical compound, polyol with the number average molecular weight of 500-5000 and micromolecular polyol, polyamine or polybasic acid anhydride with the molecular weight of 30-500; applying an adhesive system on the surface of the special fiber by adopting a high-pressure vapor deposition technology, paving the adhesive-containing special fiber into a three-dimensional network fiber net layer by a pneumatic-poking rod process, and performing hot pressing to prepare the flexible formaldehyde-free fiber board. The flexible sponge-like porous structure is arranged among the fibers of the flexible ultrathin fiber board. The method is simple and easy to implement, low in production cost, green and environment-friendly, and is beneficial to application of the fiberboard on the large-radian curved surface and improvement of the additional value of the fiberboard.

Description

A flexible formaldehyde-free fiberboard and its manufacturing method

technical field

The invention relates to a novel flexible formaldehyde-free fiberboard and a manufacturing method thereof, in particular to a wood fiber-reinforced resin-based environmentally friendly formaldehyde-free composite material and a preparation method thereof, belonging to the field of functional composite material manufacturing and wood-based panel processing.

Background technique

Fiberboard products are widely used in all walks of life in my country. In the past, research and development mainly focused on medium-density fiberboard. The products are mainly used in traditional fields such as furniture, cabinets, and wooden floors. There are phenomena such as product homogeneity and homogeneity. Therefore, it is urgent to develop new high-performance products, broaden the application field of fiberboard, and solve the problem of homogeneity.

At present, the decoration of wood-based panels mainly uses decorative paper, resin film, veneer and other materials to veneer. With the development of wood-based panel technology, my country has developed a thin high-density fiberboard with a thickness of less than 1.5mm, which has the characteristics of thin thickness, smooth surface, and can be cut according to needs, and can replace large-format natural wood veneers and paper-based decorative materials. , has good application prospects in the fields of plywood veneer, etc., and greatly expands the new uses and new fields of fiberboard. However, due to the use of rigid adhesives such as urea-formaldehyde resin and phenolic resin for ultra-thin boards, after curing, the boards are more rigid ("Ultra-thin high-density fiberboard" group standard (T/CNFPIA3007-2019) requires elastic modulus of boards) It is ≥3800MPa), and the flexibility is relatively poor. It can be applied to veneers in some fields with small bending arcs, but for fields with large bending arcs, this ultra-thin plate cannot be effectively used because the ultra-thin plate is not flexible enough.

Patent (CN 201580036706.6) discloses a flexible fiberboard, which is prepared from wheat straw fiber, corn straw fiber, rice straw fiber, oat straw fiber, barley straw fiber and rye straw fiber and thermoplastic elastomer resin. The manufacturing method is that the straw fiber and the thermoplastic resin powder are mixed, extruded and granulated through an extruder, and then the granules are hot-pressed to form a board. This manufacturing method adopts the extrusion granulation and compression molding process of the plastics industry. The manufacturing method has slow efficiency and low output. It does not match the large-scale development of my country's wood-based panel industry and cannot be applied in the actual industry. In addition, the patent does not disclose the bending radius of the fiberboard, and its flexibility cannot be effectively evaluated. Therefore, it is necessary to develop a product with good flexibility, high-efficiency manufacturing process, and its manufacturing technology that matches the scale of my country's wood-based panels, so as to promote the transformation and upgrading of my country's wood-based panel industry, broaden the application field, and solve the problem of product homogeneity.

Contents of the invention

In order to solve the application of fiberboard in the field of veneer, and in order to be able to be applied on large-curved surfaces, to increase the added value of fiberboard for the application of wood-based panels in the field of veneer, the present invention provides a new type of flexible formaldehyde-free fiberboard and its manufacturing method .

To achieve the above object, the present invention takes the following technical solutions:

A flexible formaldehyde-free fiberboard, consisting of special fibers and a flexible adhesive system, wherein the special fibers include wood, bamboo, straw and/or rice straw and other biomass material fibers, and the flexible adhesive system includes Isocyanate compounds, polyols with a number average molecular weight between 500-5000 and small molecular polyols or polyamines or polyanhydrides with a molecular weight between 30-500; the adhesive system is applied to the On the surface of the special fiber, the rubber-containing special fiber is paved into a three-dimensional network fiber net layer through the pneumatic-push stick process, and the flexible formaldehyde-free fiber board is prepared by hot pressing.

Further, the mass fraction of the special fiber accounting for the fiberboard is 50% to 95%, and the mass fraction of the flexible adhesive system accounting for the fiberboard is 50% to 5%; the preferred flexible adhesive system mass fraction is 5-20%, the more preferred mass fraction is 5-15%.

Further, the special fiber is composed of biomass material fibers such as wood, bamboo, straw and/or rice straw, and the ratio is not limited. The special fibers are biomass material fibers such as fir, poplar, eucalyptus, moso bamboo, green bamboo, hemp bamboo, corn straw, wheat straw, rice and/or upland rice straw, and the type is not particularly limited.

Further, in the special fibers, more than 80% of the fibers have a length of 0.5-7mm, and more than 80% of the fibers have a diameter of 0.05-0.3mm; preferably, more than 80% of the fibers have a length of 1-4.5mm, and 80% The diameter of the above fibers is 0.08-0.2mm.

Further, in the flexible adhesive system, calculated in parts by weight, the isocyanate compound is 5-30 parts, preferably 5-20 parts, more preferably 10-20 parts; the number average molecular weight is 500 The polyhydric alcohol between -5000 is 60-85 parts, is preferably 60-80 parts, more preferably is 70-80 parts; 10 parts, preferably 1-8 parts, more preferably 3-5 parts.

Further, the isocyanate compounds include: toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate One or more of isocyanate (IPDI), TDI or MDI or HDI or IPDI modified epoxy resin, and TDI or MDI or HDI or IPDI reacted prepolymer with polyether.

Further, the polyols with number average molecular weight between 500-5000 include: one or more of diols or polyol polymers such as polytetrahydrofuran ether glycol, polyethylene glycol and polypropylene glycol, preferably The number average molecular weight is 500-3000, and the more preferred number average molecular weight is 1000-2000.

Further, the polyols or polyamines or polyanhydrides with a molecular weight between 30-500 include: 1,4-butanediol, 1,3-butanediol, ethylene glycol, ethylenediamine, 3, One or more of 3'-dichloro-4,4-diamino-diphenylmethane, pyromellitic anhydride, phthalic anhydride, phthalic anhydride and trimellitic anhydride glyceride, etc. .

Further, the flexible adhesive system also includes a foaming agent and/or a toughening agent; the foaming agent includes inorganic foaming agents (carbonates such as calcium carbonate, magnesium carbonate, sodium bicarbonate) and organic foaming agents. Foaming agent (azo compound, sulfonyl hydrazide compound, nitroso compound, n-hexane, n-heptane, methylene chloride, trichloromethane and other organic solvents; the amount added is 1-10% of the mass of the entire adhesive system Tougheners include liquid polysulfide rubber, liquid acrylate rubber, liquid polybutadiene rubber, nitrile rubber, ethylene propylene rubber and styrene-butadiene rubber and other rubbers and polyurethanes, styrenes, polyolefins, polyesters Products such as syndiotactic 1,2-polybutadiene and polyamides, including low-molecular-weight polyamides and low-molecular inactive tougheners, such as phthalates; the amount added is the entire adhesive 1-10% of the system mass.

Further, the flexible adhesive system can be used in a solvent-free state or in a solvent-dissolved and diluted state, that is, the flexible adhesive system can also contain a solvent, and the solvent can be tetrahydrofuran, acetone, ethyl acetate Esters, ethanol, methanol, N,N'-dimethylformamide, N,N'-dimethylacetamide, dimethyl sulfoxide, monochloromethane, dichloromethane, chloroform and tetrachloromethane, etc. one or more of. The added amount of the solvent is 10%-95% of the mass of the whole flexible adhesive system.

Further, the thickness of the flexible formaldehyde-free fiberboard is less than or equal to 10mm, and the bending radius is less than or equal to 10mm. Preferably, the thickness of the flexible formaldehyde-free fiberboard is 0.1-10mm, and the bending radius is 0.1-10mm. More preferably, the thickness of the flexible formaldehyde-free fiberboard is 0.5-3mm, and the bending radius is 2-8mm.

The manufacturing method of above-mentioned flexible formaldehyde-free fiberboard, comprises the following steps:

(1) Preparation of special fibers: put biomass materials such as wood, bamboo, straw and/or rice straw into a digester for cooking, and after the biomass material becomes soft, put it into a refiner containing alkaline solution , ground into fine fibers, the size requirements of fine fibers are: the length of 0.5-7mm accounts for more than 80%, and the diameter of 0.05-0.3mm accounts for more than 80%;

(2) Preparation of flexible adhesive system: the flexible adhesive system contains isocyanate compounds, polyols with a number average molecular weight between 500-5000 and small molecule polyols or polyamines with a molecular weight between 30-500 or polybasic acid anhydride, etc.; the adhesive system is composed of one or more mixtures of the above-mentioned polymers after chemical reactions of the mixtures;

(3) Preparation of formaldehyde-free fiberboard: the adhesive system is applied to the surface of the special fiber by high-pressure vapor deposition technology, and then the special fiber containing the glue is paved into a three-dimensional network fiber network layer by a pneumatic-push stick process, and hot-pressed A flexible formaldehyde-free fiberboard is prepared.

In step (1), the size requirements of the thin fibers are preferably as follows: the length of the thin fibers is between 1-4.5 mm, accounting for more than 80%, and the diameter of the thin fibers is between 0.08-0.2 mm, accounting for more than 80%.

In step (1), the alkaline solution is a solution composed of one or more mixtures of NaOH, KOH, Ca(OH) ₂ , Na ₂ SO ₃ and Na ₂ S, and the mass fraction of the solute in the solution is It is 0.5%-50%, and the ratio of the mixture is not limited in any way.

In step (2), the flexible adhesive system further includes a solvent, the solvent is tetrahydrofuran, acetone, ethyl acetate, ethanol, methanol, N,N'-dimethylformamide, N,N'-dimethylformamide Acetamide, dimethyl sulfoxide, monochloromethane, dichloromethane, chloroform and/or tetrachloromethane, etc. The added amount of the solvent is 10-95% of the mass of the whole flexible adhesive system.

Described flexible adhesive system also comprises foaming agent and/or toughening agent; Foaming agent comprises inorganic foaming agent (carbonates such as calcium carbonate, magnesium carbonate, sodium bicarbonate) and organic foaming agent ( Azo compounds, sulfonyl hydrazide compounds, nitroso compounds, n-hexane, n-heptane and other organic solvents, the addition amount is 1-10% of the mass of the entire adhesive system; toughening agents include liquid polysulfide rubber, liquid Acrylic rubber, liquid polybutadiene rubber, nitrile rubber, ethylene propylene rubber and styrene-butadiene rubber and other rubbers and polyurethanes, styrenes, polyolefins, polyesters, syndiotactic 1,2-polybutadiene Vinyl and polyamide products, including low-molecular-weight polyamides and low-molecular inactive tougheners, such as phthalates, are added in an amount of 1-10% of the mass of the entire adhesive system.

In step (3), the mass fraction of the special fiber accounting for the fiberboard is 50% to 90%, and the mass fraction of the adhesive system accounting for the fiberboard is 50% to 10%; the preferred mass fraction of the adhesive system is It is 5-20%, more preferably the mass fraction is 5-15%.

The high-pressure vapor deposition technology described above adopts a high-pressure gas-assisted deposition process, bombards the adhesive system with air of a certain energy and flow intensity, and disperses the adhesive into micro-nano-sized colloidal particles. Combined collision effect, increase the migration ability of deposited colloidal particles, and improve the adhesion of colloidal particles on the fiber surface.

The pneumatic-pushing stick process adopts slow wedge angle exhaust and one-time heavy preloading method, optimizes the parameters of drum diameter and exhaust angle, and solves the problem of uniform paving of wood fiber boards through a large-diameter steel belt preloading system. .

The three-dimensional network fiber layer adopts a pneumatic-push stick process, and the glue-containing fibers are interspersed in the three directions of XYZ to form a three-dimensional fluffy interpenetrating network fiber mat.

In the hot pressing, the hot pressing temperature is 50-200°C, and the hot pressing pressure is 0.5-5 MPa, so that the hydroxyl groups on the fiber surface react with functional groups such as isocyanate and acid anhydride to form chemical bonds such as carbamate functional groups and carboxyl groups. , improve the bonding force between the adhesive and the fiber, and improve the mechanical properties of the sheet.

During the hot pressing process of the board, due to the action of the foaming agent and (or) the reaction between isocyanate and moisture and (or) isocyanate and anhydride, a large amount of gas is released, and the gas expands at high temperature, making the interior of the adhesive to be cured A large number of pores are formed, and because the adhesive itself is flexible, a sponge-like flexible porous network structure is formed, giving the board flexibility. The obtained flexible fiber board has an internal void ratio of ≥ 25%, and a sponge-like porous flexible network structure exists between the fibers.

Beneficial effects of the present invention:

(1) The present invention discloses a method for manufacturing a flexible fiberboard, which uses a flexible adhesive system to prepare the fiberboard, which breaks through the rigidity of the traditional fiberboard and is beneficial to the application of the fiberboard in the field of curved surfaces.

(2) The invention discloses a method for preparing an ultra-thin flexible fiberboard, which is beneficial to the application of the fiberboard in the field of expanding the curvature, and breaks through the added value of the fiberboard.

(3) The invention discloses a method for preparing a flexible ultra-thin fiberboard. The board is isotropic and has flexibility, which is conducive to applying the fiberboard to the surface decoration of plywood, breaking through the problem of anisotropy of plywood veneer, and inhibiting the production of plywood. The surface veneer cracks during use.

(4) The fibers of the flexible ultra-thin fiberboard of the present invention have a flexible sponge-like porous structure, which is conducive to the stretchability of the fiberboard when it is subjected to external force, and prevents the fiberboard from breaking.

Description of drawings

Fig. 1 is the length distribution of fiber;

Fig. 2 is the diameter distribution of fiber;

Figure 3 is a schematic diagram of a traditional ultra-thin fiberboard with a thickness of 1mm and its bending performance test;

Figure 4 is a schematic diagram of a flexible ultra-thin fiberboard and its bending performance test in Example 1 of the present invention;

Fig. 5 is the spongy foam between flexible ultra-thin fiberboard fibers in Example 1 of the present invention;

Figure 6 is a schematic diagram of the flexible ultra-thin fiberboard and its bending performance test in Example 2 of the present invention;

Figure 7 is a schematic diagram and bending performance test of the flexible ultra-thin fiberboard in Example 4 of the present invention;

Fig. 8 is a schematic diagram and bending performance test of the flexible ultra-thin fiberboard in Example 6 of the present invention;

Fig. 9 is a schematic diagram of a traditional ultra-thin fiberboard with a thickness of 3 mm and its bending performance test.

Detailed ways

The principles and specific steps of the present invention will be described in detail and completely below in conjunction with the embodiments of the present invention. However, the described embodiments are part of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, under the guidance of the embodiments, all other embodiments obtained by those skilled in the art through simple repetition without making creative efforts belong to the protection scope of the present invention.

The preparation method of the flexible formaldehyde-free fiberboard of the present invention comprises the following steps:

(1) For the preparation of special fibers, put wood, bamboo, straw, rice straw and other biomass materials into a digester and cook them. After the biomass materials become soft, put them into a refiner containing an alkaline solution and grind them. Thin fibers, the size requirements of fine fibers are: as shown in Figure 1, it is the length distribution of fibers (abscissa unit mm), and the length accounts for more than 80% between 0.5-7mm, as shown in Figure 2, it is the length distribution of fibers. Diameter distribution (abscissa unit mm), the diameter between 0.05-0.3mm accounts for more than 80%, wherein the length between 1-4.5mm is preferred, and the diameter between 0.08-0.2mm is preferred.

Biomass materials such as wood, bamboo, straw, and rice straw refer to biomass materials such as fir, poplar, eucalyptus, moso bamboo, green bamboo, hemp bamboo, corn straw, wheat straw, rice, and upland rice. special limited.

Alkaline solution refers to a solution consisting of one or more mixtures of NaOH, KOH, Ca(OH) ₂ , Na ₂ SO ₃ , Na ₂ S, and the mass fraction of solute in the solution is 0.5%-50%. The ratio of the mixture is not limited in any way.

(2) Preparation of a flexible adhesive system, the flexible adhesive system contains isocyanate compounds, polyols with a number average molecular weight between 500-5000, small molecule polyols or polyhydric alcohols with a molecular weight between 30-500 Amine or polybasic acid anhydride, foaming agent, toughening agent, etc. The adhesive system is composed of a mixture of one or more of the above or a polymer after a chemical reaction of the mixture.

Isocyanate compounds, characterized by including toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI ), TDI or MDI or HDI or IPDI modified epoxy resin, TDI or MDI or HDI or IPDI and polyether reaction prepolymer.

The polyhydric alcohol with number average molecular weight between 500-5000 is characterized in that polytetrahydrofuran ether glycol, polyethylene glycol, polypropylene glycol and other dibasic alcohols or polyol polymers, preferred number average molecular weight 500-3000, more The preferred number average molecular weight is 1000-2000.

Polyols or polyamines or polyanhydrides with a molecular weight between 30-500, characterized by 1,4-butanediol, 1,3-butanediol, ethylene glycol, ethylenediamine, 3,3'-di Chloro-4,4-diamino-diphenylmethane, pyromellitic anhydride, phthalic anhydride, phthalic anhydride, trimellitic anhydride glyceride, etc.

The adhesive system is that the adhesive can be dissolved and diluted in a solvent-free state or a solvent. The solvent refers to tetrahydrofuran, acetone, ethyl acetate, ethanol, methanol, N,N'-dimethylformamide, N , N'-dimethylacetamide, dimethyl sulfoxide, monochloromethane, dichloromethane, chloroform, tetrachloromethane, etc.

(3) Preparation of formaldehyde-free fiberboard: the adhesive system is applied to the surface of the special fiber by high-pressure vapor deposition technology, and then the special fiber containing the glue is paved into a three-dimensional network fiber network layer by a pneumatic-push stick process, and hot-pressed A flexible formaldehyde-free fiberboard is prepared.

The mass fraction of the special fiber in the fiberboard is 50% to 90%, the mass fraction of the adhesive in the fiberboard is 50% to 10%, the preferred mass fraction of the adhesive is 5-20%, and the more preferred mass fraction is 5% -15%.

High-pressure vapor deposition technology, using high-pressure gas-assisted deposition technology, bombards the adhesive system with air with a certain energy and flow intensity to disperse the adhesive into micro-nano-sized colloidal particles. Through the cascade collision effect between air and deposited colloidal particles, Increase the migration ability of deposited colloidal particles and improve the adhesion of colloidal particles on the fiber surface. Pneumatic-pushing stick technology, characterized by slow wedge angle exhaust and one-time heavy preloading method, optimized drum diameter and exhaust angle parameters, and large diameter steel belt preloading system to solve the even paving of wood fiber boards. The three-dimensional network fiber layer is characterized by adopting the pneumatic-push stick process, and the glue-containing fibers are interspersed in the three directions of XYZ to form a three-dimensional fluffy interpenetrating network fiber mat.

The hot-pressing temperature is 50-200°C, and the hot-pressing pressure is 0.5-5MPa, so that the hydroxyl groups on the surface of the fiber react with functional groups such as isocyanate and anhydride to form chemical bonds such as carbamate functional groups and carboxyl groups, and improve the adhesive and fiber quality. The bonding force between them improves the mechanical properties of the sheet. During the hot pressing process of the board, due to the action of the foaming agent and (or) the reaction between isocyanate and moisture and (or) isocyanate and anhydride, a large amount of gas is released, and the gas expands at high temperature, making the interior of the adhesive to be cured A large number of pores are formed, and because the adhesive itself is flexible, a sponge-like flexible porous network structure is formed, giving the board flexibility.

The thickness of the flexible fiberboard is less than or equal to 10mm, and the bending radius is less than or equal to 10mm.

Flexible fiberboard, the internal porosity of the board is ≥25%, and there is a sponge-like porous flexible network structure between the fibers.

Example 1

Select poplar as a raw material, cook it first, and after the wood becomes soft, put it into a refiner containing NaOH solution (NaOH mass fraction is 5%) and grind it to obtain a fiber length between 0.5-4.5mm Accounting for 85%, the diameter is between 0.05-0.2mm accounting for 82%, the fiber is dried.

Use toluene diisocyanate, polytetrahydrofuran ether diol (number average molecular weight Mn=1000), and ethylene glycol to form an adhesive system. The mass ratio of each component of the adhesive system is 35:200:3.1. Stir evenly to form a glue. Adhesive system. The adhesive is applied to the surface of the fiber using high-pressure vapor deposition technology. After the application of the adhesive is completed, the fiber containing the adhesive is assembled and hot-pressed at 120°C for 2 hours, and cured to prepare a flexible ultra-thin fiber board. The thickness of the fiberboard is 1 mm, and the mass fraction of the adhesive is 20%.

Example 2

Select poplar as a raw material, cook it first, and after the wood becomes soft, put it into a refiner containing KOH solution (KOH mass fraction is 5%) and grind it to obtain a fiber length between 0.5-4.5mm Accounting for 85%, the diameter is between 0.05-0.2mm accounting for 82%, the fiber is dried.

The adhesive system is composed of 4,4'-diphenylmethane diisocyanate (MDI), polytetrahydrofuran ether glycol (number average molecular weight Mn=1000), and ethylene glycol. The mass ratio of each component of the adhesive system is 50:100:6.2, stir evenly to form an adhesive system. The adhesive is applied to the surface of the fiber using high-pressure vapor deposition technology. After the application of the adhesive is completed, the fiber containing the adhesive is assembled and hot-pressed at 120°C for 2 hours, and cured to prepare a flexible ultra-thin fiber board. The thickness of the fiberboard is 1 mm, and the mass fraction of the adhesive is 20%.

Example 3

Select poplar as a raw material, cook it first, and after the wood becomes soft, put it into a refiner containing NaOH solution (NaOH mass fraction is 10%) and grind it to obtain a fiber size of which the fiber length is 4.5- 90% is between 7.0mm and 85% is between 0.2-0.3mm in diameter, and the fibers are dried.

React 50g of 4,4'-diphenylmethane diisocyanate and 200g of polytetrahydrofuran ether diol at 80°C for 2 hours, then add 20g of pyromellitic anhydride and 50g of acetone, and further stir the reaction to form an adhesive Dosage system.

The adhesive is applied to the surface of the fiber using high-pressure vapor deposition technology. After the adhesive is applied, see the fiber assembly containing the adhesive. It is hot-pressed at 150°C for 3 hours and cured to prepare a flexible ultra-thin fiber board. The thickness of the fiberboard is 1 mm, and the mass fraction of the adhesive is 20%.

Example 4

Select bamboo as a raw material, remove the bamboo green of the bamboo, and then cook the bamboo yellow. After the bamboo yellow becomes soft, put it into a mixed solution containing NaOH and Na ₂ SO ₃ (the mass fraction of NaOH is 20%, Na ₂ SO ₃ mass fraction is 10%) grinding in the refiner, the obtained fiber length accounts for 85% between 0.5-4.5mm, and the diameter accounts for 82% between 0.05-0.2mm, and the fiber is dried.

The adhesive system is composed of 4,4'-diphenylmethane diisocyanate (MDI), polytetrahydrofuran ether glycol (number average molecular weight Mn=1000), and ethylene glycol. The mass ratio of each component of the adhesive system is 50:100:6.2, stir evenly to form an adhesive system. The adhesive is applied to the surface of the fiber using high-pressure vapor deposition technology. After the application of the adhesive is completed, the fiber containing the adhesive is assembled and hot-pressed at 120°C for 2 hours, and cured to prepare a flexible ultra-thin fiber board. The thickness of the fiberboard is 0.5mm, and the mass fraction of the adhesive is 30%.

Example 5

Select Chinese fir as raw material, cook it first, after the wood becomes soft, put it into a refiner containing NaOH solution (NaOH mass fraction is 5%) and grind to obtain fiber size of which fiber length is 4.5-7.0 90% is between mm, 85% is between 0.2-0.3 mm in diameter, and the fibers are dried.

50g of 4,4'-diphenylmethane diisocyanate and 50g of polytetrahydrofuran ether diol (number average molecular weight Mn=2000) were reacted at 80°C for 2 hours, and then put into 500g of epoxy resin (E51) Stir and react for 4 hours, and finally add 50 g of acetone and 200 g of ethylenediamine and stir evenly to form an adhesive system. The adhesive is applied to the surface of the fiber using high-pressure vapor deposition technology. After the adhesive is applied, see the fiber assembly containing the adhesive. It is hot-pressed at 120°C for 2 hours and cured to prepare a flexible ultra-thin fiber board. The thickness of the fiberboard is 0.5 mm, and the mass fraction of the adhesive is 20%.

Example 6

Select poplar as raw material, cook it first, and after the wood becomes soft, put it into a refiner containing a mixed solution of NaOH and Na ₂ S (the mass fraction of NaOH is 20%, and the mass fraction of Na2S is 5%) Grinding to obtain a fiber size in which 90% of the fiber length is between 4.5-7.0 mm, and 85% of the fiber diameter is between 0.2-0.3 mm, and the fiber is dried.

The adhesive system is composed of 4,4'-diphenylmethane diisocyanate (MDI), polypropylene glycol (number average molecular weight Mn=1000), and 1,4-butanediol. The mass ratio of each component of the adhesive system 50:100:4.5, stir evenly to form an adhesive system. The adhesive is applied to the surface of the fiber using high-pressure vapor deposition technology. After the application of the adhesive is completed, the fiber containing the adhesive is assembled and hot-pressed at 120°C for 2 hours, and cured to prepare a flexible ultra-thin fiber board. The thickness of the fiberboard is 3mm, and the mass fraction of the adhesive is 30%.

Example 7

Select eucalyptus as a raw material, first cook it, and after the wood becomes soft, put it into a refiner containing Ca(OH) ₂ solution (Ca(OH) ₂ mass fraction is 5%) and grind it to obtain fiber 90% of the length is between 0.5-4.5mm, and 85% of the diameter is between 0.05-0.2mm, and the fibers are dried.

The adhesive system is composed of 4,4'-diphenylmethane diisocyanate (MDI), polytetrahydrofuran ether diol (number average molecular weight Mn=1000), and 1,4-butanediol. The components of the adhesive system The mass ratio of the mixture is 50:100:4.5, and it is evenly stirred to form an adhesive system. The adhesive is applied to the surface of the fiber using high-pressure vapor deposition technology. After the application of the adhesive is completed, the fiber containing the adhesive is assembled and hot-pressed at 120°C for 2 hours, and cured to prepare a flexible ultra-thin fiber board. The thickness of the fiberboard is 3mm, and the mass fraction of the adhesive is 40%.

The flexible ultra-thin fiberboard obtained in the above-mentioned embodiments is tested for properties such as bending radius, sheet thickness, and sheet porosity. The bending radius test is tested as follows: the fiberboard is crimped, and when the fiberboard is about to crack, the corresponding arc The radius of is the bending radius. The porosity of the plates was tested using a high-pressure mercury porosimeter. As shown in Figures 4, 6, 7, and 8, the flexible ultra-thin fiberboards in Examples 1, 2, 4, and 6 of the present invention were tested for bending performance; Sponge-like foam between thin fiberboard fibers; as shown in Figures 3 and 9, the bending performance test was carried out on traditional 1mm and 3mm thick ultra-thin fiberboards. The test results are shown in Table 1. It can be seen that the product of the present invention has an extremely low bending radius, reflecting that the board has good flexibility and endows the fiberboard with high added value.

Ultra-thin fiberboard and traditional ultra-thin fiberboard bending radius, thickness, porosity in table 1 embodiment of the present invention

In the present invention, the biomass material is ground into a fiber material with a special size and shape, and a flexible adhesive system is applied to the surface of the fiber with a special shape by using a high-pressure vapor deposition technology, and then the special fiber containing the glue is paved into a The three-dimensional network fiber net layer is prepared by hot pressing to obtain a flexible formaldehyde-free fiber board. The fibers of the flexible ultra-thin fiberboard have a flexible sponge-like porous structure, which is conducive to the flexibility of the fiberboard when it is subjected to external force, and prevents the fiberboard from breaking. The method of the invention is simple, easy to implement, low in production cost, and environmentally friendly, and the obtained product breaks through the rigidity problem of the traditional fiberboard, facilitates the application of the fiberboard on large-curved surfaces, and increases the added value of the fiberboard.

Claims (10)

1. A flexible formaldehyde-free fiberboard, characterized in that: it is made up of special fiber and flexible adhesive system, and described special fiber comprises wood, bamboo, straw and/or rice straw fiber, and described flexible adhesive system comprises Isocyanate compounds, polyols with a number average molecular weight between 500-5000 and small molecule polyols, polyamines or polyanhydrides with a molecular weight between 30-500; the adhesive system is applied to special On the surface of the fiber, the adhesive-containing special fiber is paved into a three-dimensional network fiber net layer through the pneumatic-push stick process, and the flexible formaldehyde-free fiber board is prepared by hot pressing. 2. The flexible formaldehyde-free fiberboard according to claim 1, characterized in that: the mass fraction of the special fiber in the fiberboard is 50% to 95%, and the mass fraction of the flexible adhesive system in the fiberboard is 50% % to 5%; the special fiber is fir, poplar, eucalyptus, moso bamboo, green bamboo, hemp bamboo, corn straw, wheat straw, rice and/or upland rice straw fiber. 3. The flexible formaldehyde-free fiberboard according to claim 2, characterized in that: among the special fibers, more than 80% of the fibers have a length of 0.5-7mm, and more than 80% of the fibers have a diameter of 0.05-0.3mm. 4. The flexible formaldehyde-free fiberboard according to claim 2, characterized in that: in the flexible adhesive system, calculated according to parts by weight, the compound of isocyanate is 5-30 parts, and the number average molecular weight is 500-30 parts. 60-85 parts of polyols between 5000 and 1-10 parts of small molecule polyols, polyamines or polybasic anhydrides with molecular weights between 30-500. 5. The flexible formaldehyde-free fiberboard according to claim 4, characterized in that: said isocyanate compounds include toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), hexa Methylene diisocyanate (HDI), isophorone diisocyanate (IPDI), TDI or MDI or HDI or IPDI modified epoxy resins, and/or TDI or MDI or HDI or IPDI reacted prepolymers with polyethers ; The polyhydric alcohol with the number average molecular weight between 500-5000 includes polytetrahydrofuran ether glycol, polyethylene glycol and/or polypropylene glycol; Anhydrides include 1,4-butanediol, 1,3-butanediol, ethylene glycol, ethylenediamine, 3,3'-dichloro-4,4-diamino-diphenylmethane, pyromellitene Anhydride, Phthalic Anhydride, Phthalic Anhydride and/or Glycerides of Trimellitic Anhydride. 6. The flexible formaldehyde-free fiberboard according to claim 1, characterized in that: the flexible adhesive system also includes a solvent, and the solvent is tetrahydrofuran, acetone, ethyl acetate, ethanol, methanol, N,N '-Dimethylformamide, N,N'-dimethylacetamide, dimethyl sulfoxide, monochloromethane, dichloromethane, chloroform and/or tetrachloromethane, the amount of solvent added is the entire flexible 10-95% of the quality of the adhesive system; the flexible adhesive system also includes a foaming agent and/or a toughening agent, and the foaming agent includes an inorganic foaming agent and an organic foaming agent, and the addition amount is the entire glue 1-10% of the mass of the adhesive system; tougheners include rubber, polyurethane, polyolefin and polyester products, and the amount added is 1-10% of the mass of the entire adhesive system. 7. The flexible formaldehyde-free fiberboard according to claim 1, characterized in that: the thickness of the flexible formaldehyde-free fiberboard is less than or equal to 10mm, and the bending radius is 0.1-10mm. 8. The manufacturing method of the flexible formaldehyde-free fiberboard according to any one of claims 1-7, comprising the following steps: (1) Preparation of special fibers: put biomass materials such as wood, bamboo, straw and/or rice straw into a digester for cooking, and after the biomass material becomes soft, put it into a refiner containing alkaline solution , ground into fine fibers, the size requirements of fine fibers are: the length of 0.5-7mm accounts for more than 80%, and the diameter of 0.05-0.3mm accounts for more than 80%; (2) Preparation of flexible adhesive system: the flexible adhesive system contains isocyanate compounds, polyols with a number average molecular weight between 500-5000, small molecule polyols or polyhydric alcohols with a molecular weight between 30-500 Amines or polybasic acid anhydrides, foaming agents and/or toughening agents, etc.; the adhesive system is composed of a mixture of one or more of the above or a polymer after a chemical reaction of multiple mixtures; (3) Preparation of formaldehyde-free fiberboard: the adhesive system is applied to the surface of the special fiber by high-pressure vapor deposition technology, and then the special fiber containing the glue is paved into a three-dimensional network fiber network layer by a pneumatic-push stick process, and hot-pressed A flexible formaldehyde-free fiberboard is prepared. 9. The manufacturing method of flexible formaldehyde-free fiberboard according to claim 8, characterized in that: the alkaline solution is one of NaOH, KOH, Ca(OH) ₂ , Na ₂ SO ₃ and Na ₂ S Or several kinds of solutions, the mass fraction of the solute in the solution is 0.5%-50%. 10. The manufacturing method of flexible formaldehyde-free fiberboard according to claim 8, characterized in that: the temperature of the hot pressing is 50-200°C, and the hot pressing pressure is 0.5-5MPa; the obtained flexible fiberboard has a gap inside the board Rate ≥ 25%, and there is a sponge-like porous flexible network structure between the fibers.

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