CN115488989B

CN115488989B - Fiberboard and preparation method thereof

Info

Publication number: CN115488989B
Application number: CN202211182788.3A
Authority: CN
Inventors: 王军锋; 汤正捷; 黄腾华; 宋恋环; 雷福娟; 田珩; 彭晋达
Original assignee: Guangxi Zhuang Autonomous Region Forestry Research Institute
Current assignee: Guangxi Zhuang Autonomous Region Forestry Research Institute
Priority date: 2022-09-27
Filing date: 2022-09-27
Publication date: 2023-12-22
Anticipated expiration: 2042-09-27
Also published as: CN115488989A

Abstract

The embodiment of the application discloses a fiberboard and a preparation method thereof, the fiberboard comprises a heat conduction functional layer, the heat conduction functional layer comprises wood fiber and graphite components which are mixed with each other and bonded by an adhesive, the fiber length of the wood fiber is 5 mm-10 mm, and the graphite components are graphite particles with the particle size of 0.3 mm-5 mm or small graphite sheets with the length of 0.3 mm-5 mm. The fiber board has relatively good heat conduction effect, relatively good bonding strength, high bonding strength of graphite components and wood fibers, and fine mechanical strength and materials, and is beneficial to mechanical processing.

Description

Fiberboard and preparation method thereof

Technical Field

The utility model relates to the technical field of wood board product structures, in particular to a fiberboard, and also relates to a preparation method of the fiberboard.

Background

The artificial board made of wood fiber is called as fiber board (or density board) and is widely used in the fields of home decoration, building material, transportation, backing board of printed circuit board, etc. In some applications, it is desirable that the fiberboard has relatively high conductive (heat-dissipating) properties, such as geothermal floors, mats for printed circuit boards, and the like. However, the main raw materials of the fiber board are wood fiber and adhesive, the wood fiber has good heat insulation performance, and the adhesive has certain heat insulation performance, so that the heat conduction (radiation) performance of the fiber board is relatively poor, and the application or use effect of the fiber board in the field is affected.

To solve this technical problem, a fiber board with high heat conduction (radiation) performance is provided, and two solutions are generally described in the prior art. The first solution is to compound the graphite component with the fiber board in the form of a coating, a structural layer. For example, the utility model patent with publication number of CN207560369U in Chinese patent database and name of "graphene heating chip" discloses a method comprising sequentially stacking together from bottom to top: the fiber board comprises a first fiber board, a second fiber board, a graphene carbon fiber board, a copper foil heating layer and a third fiber board. For another example, the Chinese patent application with publication number of CN114074369A and name of "production process of graphene fiber plate" discloses a graphene fiber plate which sequentially comprises a nano graphene layer, a flame-retardant fiber layer, a graphene anti-corrosion layer and a fiber plate blank from top to bottom, wherein the nano graphene layer is a single-layer nano graphene layer, the graphene anti-corrosion layer is formed by coating graphene composite paint, and a graphene-based additive is added in an adhesive used by the fiber plate blank. The fiber board compounded with graphene provided by the scheme has relatively high heat conduction (radiation) performance, corrosion resistance, fire resistance and flame retardance. It has the following problems: firstly, the nano graphene layer, the flame-retardant fiber layer and the graphene anti-corrosion layer are respectively bonded through an adhesive, but graphene and wood fiber cannot form cross-linking, so that the bonding strength between the three structural layers is simply dependent on the bonding performance of the adhesive, and the adhesive performance is relatively poor; secondly, the high price of graphene makes the graphene fiberboard of the scheme very high in production cost.

The second option is to add the graphite component in dispersed form to the adhesive. For example, the Chinese patent application with publication number of CN111621253A in Chinese patent database is named as a graphite-based high-strength heat-conducting epoxy resin adhesive and a preparation method thereof, and discloses a technical scheme for improving the heat-conducting property of the adhesive by adding components such as modified graphite, composite glass fiber and the like into a bisphenol A type epoxy resin adhesive. For another example, the Chinese patent application with publication number of CN113650127A, named as "preparation process of fiber board containing graphene", discloses a preparation method of wood peeling, chipping, screening, washing, steaming, fiber separation, sizing agent adjustment, fiber drying, paving and forming, prepressing, hot pressing, cooling, sanding, inspection and sorting, packaging and warehousing, wherein the sizing agent adjustment step is to apply resin containing graphene into the fiber. However, in the first comparative document, the so-called modified graphite is the graphene obtained by extraction, and the extraction process is relatively complex and has relatively high cost. And the second comparison file is directly added with graphene. The inventor's comparative experiments show that the graphite component of the adhesive is not only not bonded with wood fibers but also can prevent the bonding between wood fibers by adopting the adhesive (regardless of the adhesive) added with modified graphite or graphene, so that the bonding strength of the fiber board prepared by the adhesive is relatively poor, and the physical and chemical properties such as water resistance, mechanical strength and the like of the fiber board can be expected to be greatly influenced.

In view of the above, there is a lack of a product or method of manufacture in the prior art that can improve the heat conducting (dissipating) properties of a fiberboard while at the same time guaranteeing its bonding strength.

Disclosure of Invention

A first technical object of the present utility model is to overcome at least one of the above-mentioned technical problems, thereby providing a fiberboard; a second technical aim of the utility model is to provide a method for preparing such a fiberboard.

To achieve the above object, one embodiment of the present utility model provides a fiber sheet comprising a heat conductive functional layer comprising wood fibers and graphite components mixed with each other and bonded by an adhesive, characterized in that the fiber length of the wood fibers is 5mm to 10mm, and the graphite components are graphite particles having a particle diameter of 0.3mm to 5mm, or small graphite sheets having a length of 0.3mm to 5 mm.

Preferably, the amount of the graphite component added is 4.5 to 40% by mass of the total mass of the mixture of wood fiber, adhesive and graphite component.

Preferably, the graphite particles are flaky graphite particles, and the thickness of the graphite particles is 0.05mm to 0.1mm; the fiber diameter of the wood fiber is 0.05 mm-0.08 mm.

Preferably, the thickness of the heat conductive functional layer is 0.2mm to 2mm.

Preferably, the surface and/or the bottom surface of the heat conducting functional layer is/are provided with a fiber layer, the fiber layer comprises short fibers bonded by an adhesive, and the fiber length of the short fibers is 0.5 mm-3 mm.

Preferably, the heat conductive functional layer and the fiber layer use the same kind of adhesive.

In order to achieve the above objective, another embodiment of the present utility model provides a method for preparing the above fiber board, which is prepared by a step of hot press molding, and sequentially comprises a step of mixing wood fiber with glue, a step of mixing graphite components, a step of assembling the mixture, a step of preforming, and a step of cooling and drying to prepare a pre-cured heat conductive functional layer;

the step of mixing the wood fiber, wherein the water content of the wood fiber after mixing is 30-35%;

and the step of cooling and drying reduces the moisture content of the pre-cured heat conduction functional layer obtained in the step of preforming to 16% -20%.

Preferably, in the preforming step, the adhesive is pre-cured by non-pressure thermal contact to obtain the pre-cured heat conductive functional layer, and the thermal contact temperature is 120 ℃ to 140 ℃.

Preferably, preparing a lower fiber blank layer through a short fiber glue mixing step and a short fiber assembly step in sequence, and placing the pre-cured heat conduction functional layer on the lower fiber blank layer; and/or

Preparing an upper fiber blank layer on the pre-cured heat conducting functional layer sequentially through a step of short fiber glue mixing and a step of short fiber blank assembling;

finally, the fiberboard is manufactured through a hot press molding step.

Preferably, the adhesive used in the step of mixing the wood fiber and the step of mixing the short fiber is a resin adhesive modified by taking lignin as a part of phenol as a substitute raw material.

In summary, compared with the prior art, the utility model has the following beneficial effects:

1. through the improvement of the structure and the composition of the product, the graphite component doped in the wood fiber enables the heat conduction functional layer to have relatively good heat conduction effect; the existence of wood fibers with relatively longer fiber length can improve the uniformity of the bonding strength of the body structure of the heat conduction functional layer, and improve the interweaving property and interweaving degree of fibers in the fiber board forming process so as to bind graphite components in the space formed by weaving the mesh bag-shaped structure, thereby improving the bonding strength of the graphite components and the wood fibers and avoiding influencing the bonding performance of the artificial (fiber) board due to the existence of the graphite components; the existence of wood fiber with relatively short fiber length can fill the pores between the graphite component and the space formed by weaving the mesh bag-shaped structure, so that the mechanical strength is improved, and the material is finer and is beneficial to mechanical processing.

2. Through further improvement of product structure and ingredient composition, the fibrous layer comprises the short fiber, therefore has better mechanical processing properties such as sculpture, marking off, fluting, and the processing of being convenient for makes the fibreboard of this application technical scheme can adapt to the processing demand of various building materials.

3. Through further improvement of the structure and the composition of the product, lignin is utilized to replace part of the raw material modified phenolic resin adhesive, so that the crosslinking of long fibers can be promoted, and the formed mesh bag-shaped structure is firmer.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive faculty for a person skilled in the art.

Fig. 1 is a schematic structural diagram of a heat conductive functional layer in embodiment 1 of the present application.

Fig. 2 is a graph showing comparison of drilling temperatures of the heat conductive functional layers 1a,1b,1c,1d,1e,1f in example 1 of the present application.

Fig. 3 is a schematic structural view of a fiberboard of embodiment 4 of the present application.

Fig. 4 is a schematic structural view of a fiberboard of example 5 of the present application.

In the figure: 1. a heat conduction functional layer, 2, a fiber layer.

Detailed Description

In order to better understand the technical solutions in the present application, the following description will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, shall fall within the scope of the present application.

Example 1

Referring to a fiberboard shown in fig. 1, it is constituted by only a heat conductive functional layer 1 having a thickness of 0.5mm, and the heat conductive functional layer 1 includes wood fibers and graphite components mixed with each other and bonded by an adhesive. The wood fiber is long fiber with the fiber length of 5 mm-10 mm, wherein the ratio of the wood fiber A with the fiber length of 7 mm-10 mm is 70% -75%, and the rest 25% -30% is wood fiber B with the fiber length of 5 mm-7 mm. The graphite component is graphite particles (spheroidal particles) having a particle diameter of 0.4 to 0.5 mm.

Through the product structure and the component composition, firstly, the mutually-bonded wood fibers form the body structure of the heat conduction functional layer 1 (namely the fiber board in the embodiment), and the graphite component doped in the wood fibers enables the heat conduction functional layer 1 to have relatively good heat conduction effect. Secondly, in the step of mixing the wood fiber, the long fiber is used as a raw material, and the wood fiber A with the fiber length of 7-10 mm exists and occupies a relatively main mass proportion, so that the adhesive can be uniformly dispersed on the surface of the wood fiber, and the bonding strength of the body structure of the heat conduction functional layer 1 is uniform and consistent; further, through friction between the wood fiber and the graphite component, the adhesive is uniformly dispersed on the surface of the graphite component, so that the bonding strength of the graphite component and the wood fiber can be improved, and the influence on the gluing performance of the fiber board due to the existence of the graphite component is avoided. Again, the presence of wood fibres a having a fibre length of 7mm to 10mm also increases the interweaving properties and interweaving degree of the fibres during the formation of the fibre board, i.e. cross-linking between fibres by hydrogen bonding, intermolecular forces, affinity between hemicellulose. The longer the fiber length is, the stronger the wood fiber can be interwoven into a net bag-shaped structure in the hot pressing process, and the graphite component is bound in the space formed by weaving the net bag-shaped structure, so that the bonding strength of the graphite component and the wood fiber is further improved, and the influence on the gluing performance of the fiber board due to the existence of the graphite component is avoided. Finally, the existence of the wood fiber B with the fiber length of 5-7 mm can fill the pores between the graphite component and the space formed by weaving the mesh bag-shaped structure, so that the mechanical strength of the fiber board is improved, and the material is finer and more favorable for mechanical processing.

It should be noted that the fiber board must be formed by high-temperature hot-pressing treatment, and the mesh bag-shaped structure formed by crosslinking the wood fiber A provides space for thermal expansion and cold contraction of the graphite component possibly occurring in the process of heating and cooling. Although the coefficient of thermal expansion of the graphite component is very small, it is a trend in dimensional change as opposed to wet expansion and dry shrinkage of wood fibers. Compared with the prior art, the method has the advantages that compared with the scheme that the wood fibers are bonded with the graphite component only through the adhesive, the method can eliminate the risk of degumming to a certain extent, which is caused by thermal expansion and shrinkage and wet expansion and shrinkage of the wood fibers possibly occurring in the process of heating and cooling the graphite component.

As a preferred embodiment, the fiberboard is prepared by the following process steps:

a step of glue mixing of wood fibers, in which a pipeline gluing method or other methods in the prior art are used, glue mixing is firstly carried out on wood fibers A with the fiber length of 7-10 mm, so that the surface of the wood fibers A is uniformly adhered with an adhesive; and then adding wood fiber B with the fiber length of 5-7 mm in proportion, and transferring part of adhesive on the surface of the wood fiber A to the surface of the wood fiber B by continuous turning and mutual friction to realize the mixing of the wood fiber A and the wood fiber B and the adhesive mixing of the wood fiber B. The adhesive is phenolic resin adhesive. The water content of the wood fibers after glue mixing is controlled to be 32+/-2% by controlling the primary water content (for example, 14% -18%) and the sizing amount (for example, 10% -12%) of the wood fibers A and the wood fibers B. For example, the primary water content of the wood fiber A and the wood fiber B is 14-18%, and the sizing amount is 10-12%. It should be noted that the amount of the adhesive to be added should be calculated based on the total mass of the mixture of the wood fiber a, the wood fiber B and the graphite component, although the adhesive is directly added to the wood fiber a. Preferably, the primary water content of wood fiber A is 17+ -1%, and the primary water content of wood fiber B is 15+ -1%. The relatively high primary moisture content of wood fiber A can facilitate the transfer of the adhesive between the surfaces of wood fiber A, and the primary moisture content of wood fiber B is about 2% lower than the primary moisture content of wood fiber A can facilitate the transfer of the adhesive from the surfaces of wood fiber A to the surfaces of wood fiber B.

Mixing the graphite component, in which step the glued wood fibers are mixed with the graphite component using a roller mixer or other equipment of the prior art. By adjusting the amount of the graphite component added, a fiberboard having different heat conduction (radiation) properties can be obtained. In this embodiment, the processes of adding graphite particles in an amount of 5%, 15%, 25%, 30%, 35%, 40% of the total mass of the mixture can be used to prepare the heat conductive functional layer 1A, the heat conductive functional layer 1B, the heat conductive functional layer 1C, the heat conductive functional layer 1D, the heat conductive functional layer 1E, and the heat conductive functional layer 1F, respectively.

Drying the mixture, in which the water content of the mixture is reduced to 18.+ -. 2% using a mesh belt dryer or other equipment of the prior art.

A step of assembling the mixture, in which a mixture composed of wood fiber, adhesive and graphite components is put on a continuous conveyor belt by using a fiber spreading machine or other devices in the prior art, and spread to form a continuous mixture assembling layer.

And a step of hot press molding, in which a flat plate hot press or a hot press roller is used to press and mold the mixture assembly layers at a hot press temperature of 180+/-2 ℃ and a hot press pressure of 2MPa to obtain the heat conduction functional layers 1A,1B,1C,1D,1E and 1F.

By adopting the process method, the graphite component and the wood fiber are jointly turned and rubbed with each other after glue mixing, so that the adhesive is adhered on the surface of the graphite component uniformly, and compared with the process of mixing the wood fiber and the graphite component first and then glue mixing in the prior art, the bonding strength of the graphite component and the wood fiber can be improved, and the influence on the gluing performance of the fiber board due to the existence of the graphite component is avoided.

The comparative table of the performances of the respective heat conductive functional layers 1a,1b,1c,1d,1e,1f, as the base plate for PCB drilling, is shown in table 1 and the comparative table of drilling temperatures is shown in fig. 2. In tables 1 and 2, a control group 1 is a 0.5mm thick high-density fiberboard, a control group 2 is a 0.5mm thick fiberboard prepared in the prior art (graphite is added in an adhesive and graphene is mixed with wood fibers by glue mixing), a control group 3 is a 0.5mm thick fiberboard prepared in the prior art (the mass addition of graphene is 25 percent after the graphite and wood fibers are mixed and then glue mixing, drying, assembly and hot pressing are sequentially carried out). The density of each heat-conducting functional layer is detected according to 4.2 in GB/T17657-2013, the warping degree is detected according to annex C in SJ/T11641-2016, the internal bonding strength is detected according to 4.11 in GB/T17657-2013, and the drilling temperature is measured by an infrared thermometer to obtain the temperature at the moment of drill tip hole outlet when the drill is retracted.

TABLE 1 comparison of the Performance of thermally conductive functional layers 1A,1B,1C,1D,1E,1F

As can be seen from the data in table 1, the respective heat conductive functional layers 1a,1b,1c,1d,1e,1f in this example overcome the influence of graphite components on the bonding strength by the selection of raw materials and the improvement of the process; the graphite of the control group 2 is added through the adhesive, so the addition amount is relatively small, but the adhesiveness of the adhesive is still negatively affected; the graphite addition amount of the control group 3 is the same as that of the heat conduction functional layer 1C, and obviously, the larger graphite addition amount seriously affects the bonding strength of the fiber board.

Example 2

Example 2 is different from example 1 in that in the step of mixing the graphite components, the addition amount of the graphite components accounts for 25% of the total mass of the mixture, while the step of assembling the mixture is directly performed without going through the step of drying the mixture after the step of mixing the graphite components, and the step of preforming and the step of cool-down drying are provided between the step of assembling the mixture and the step of hot press molding, thereby producing the heat conductive functional layer 1C'.

In the preforming step, a flat plate hot press or a hot press roller is used, and the adhesive is in thermal contact with the hot press roller for 10-12 s at the hot press temperature of 125+/-2 ℃ under no pressure, so that the pre-cured heat conduction functional layer is obtained. The hot pressing temperature of the preform should be determined taking into consideration the combined effect of the addition amount of the graphite component and the thickness of the heat conductive functional layer. For example, in the case where the thickness of the heat conductive functional layer is 3mm, 130.+ -. 2 ℃ is preferably selected when the addition amount of the graphite component is 30% in the total mass of the mixture, and 135.+ -. 2 ℃ is preferably selected when the addition amount of the graphite component is reduced to 5% in the total mass of the mixture.

In the step of cooling and drying, the moisture content is reduced to 16% -20% (namely 18% and internal moisture content deviation of +/-2%) in the natural cooling process by time-adjusting treatment of the pre-cured heat conducting functional layer for a period of time.

Not only is the bonding strength of the graphite component and the wood fibers poor, but also the presence of the graphite component can influence the cross-linking of the wood fibers except for bonding, thereby influencing the bonding strength of the wood fibers, and the manufactured fiber board is not resistant to blisters. This may be due to the plasticity and sliminess of the graphite component. The inventor creatively found in practice that the direct preforming of the mixture in a state of high water content (mainly wood fibers A and B) can facilitate the formation of cross links between the wood fibers A, so that the weaving forms a relatively stable mesh bag-like structure. The principle is unknown, but the inventor finds that when the water content of the wood fiber after glue mixing is 32+/-2%, the pressed fiber board can obtain the optimal bonding strength and water-proof performance. The performance comparison table of the heat conductive functional layer 1C' is shown with reference to table 2.

TABLE 2 comparison of the Performance of thermally conductive functional layer 1C

It can be seen from table 2 that the pre-curing treatment in a high moisture content state can effectively overcome the influence of graphite components on the bonding performance of wood fibers by matching with the mesh bag-shaped structure formed by crosslinking long fibers, so that the internal bonding strength of the prepared fiber board is close to that of a common high-density fiber board.

Example 3

Example 3 is different from example 2 in that the graphite component is a small graphite sheet (scaly) having a length of 1.0mm to 1.5mm and a thickness of 0.07mm to 0.09mm, and at the same time, the fiber diameter of the wood fibers (wood fiber a, wood fiber B) is 0.05mm to 0.08mm, thereby producing the heat conductive functional layer 1C).

Obviously, the use of graphite components of relatively large size can improve the heat transfer effect, reduce the manufacturing cost of the raw materials, in other words, the cost required to make bulk graphite into graphite components of relatively large size is lower than that required for graphite particles of smaller size. However, as the specification of the graphite component increases, the influence of the inherent surface properties on the bonding properties and crosslinking properties of the wood fiber increases exponentially. In the embodiment, the fiber diameter of the wood fiber is limited to 0.05-0.08 mm, so that the wood fiber can be crosslinked to form a compact and tough mesh bag-shaped structure in the pre-curing process. Further, the graphite component is limited to a sheet form, and the graphite component can be more easily packed and bound by the mesh-bag structure. Even if the length of the small-sized graphite sheet is increased to 3.0mm to 3.3mm, the internal bonding strength of the heat conductive functional layer 1C' "is made within an acceptable range. The performance comparison table of the heat conductive functional layers 1C ", 1C'" is shown with reference to table 3.

TABLE 3 comparison of the Performance of thermally conductive functional layer 1C

Example 4

Example 4 differs from example 3 in that, referring to fig. 3, the fiber board is composed of a heat conductive functional layer 1 and a fiber layer 2. Specifically, the thickness of the heat conductive functional layer 1 is 1.0mm, and the fibrous layer 2 having a thickness of 3.0mm is bonded to the bottom surface of the heat conductive functional layer 1. The fiber layer 2 is a high-density fiber board formed by pressing short fibers bonded by an adhesive, wherein the fiber length of the short fibers is 0.8 mm-1.6 mm. In other words, the fiber layer 2 is a high-density fiberboard made of short fibers in the related art.

The fiber board of the embodiment can be used for wallboard, furniture board, floor and other purposes with heat conduction requirement, such as geothermal floor, desk board of office desk with heating structure, or wallboard with wall heating structure.

By means of the structure, the fiber layer 2 is made of short fibers, so that the fiber layer has better mechanical processing performances such as engraving, scribing and grooving, is convenient to process, and enables the fiber plate to adapt to processing requirements of various building materials.

and (3) mixing the wood fiber to obtain mixed wood fiber A and wood fiber B, wherein the adhesive is a phenolic resin adhesive.

And mixing the graphite components, namely mixing the glue-mixed wood fiber A and wood fiber B with a small-sized graphite sheet, wherein the adding amount of the small-sized graphite sheet accounts for 25% of the total mass of the mixture.

And step of mixture assembly, namely laying a mixture formed by wood fiber A, wood fiber B, an adhesive and small graphite sheets to form a continuous mixture assembly layer.

Preforming step, the process of which is the same as that of example 3.

And cooling and drying, namely reducing the water content to 16% -20% (namely 18% and allowing internal water content deviation of +/-2%) in the natural cooling process by carrying out time-adjusting treatment on the pre-cured heat-conducting functional layer for a period of time.

And (3) mixing the short fibers with glue to obtain mixed short fibers, wherein the glue is phenolic resin glue.

And (3) short fiber assembly, namely putting the glue-mixed short fibers on a continuous conveying belt by using a fiber spreading machine or other equipment in the prior art to be tiled to form a continuous lower fiber blank layer, and then covering the lower fiber blank layer with a pre-cured heat conducting functional layer to form a composite assembly layer.

And a step of hot press molding, in which a composite mat was laminated and molded at a hot press temperature of 180.+ -. 2 ℃ and a hot press pressure of 2.5MPa using a flat plate hot press or a hot press roll to obtain a fiberboard, which was designated as example 4-1.

Of course, the above process method can be adjusted as follows, so that the process method is more suitable for the wiring requirement of factory building equipment. In the step of short fiber assembly, a fiber spreading machine or other equipment in the prior art is used for spreading glue-mixed short fibers on a continuous conveying belt so as to form a continuous upper fiber blank layer on the pre-cured heat conducting functional layer in a tiling manner, and a composite assembly layer is obtained. The fiber sheet was obtained by pressing through a hot press molding step, and was designated as example 4-2. The method can effectively shorten the length of the production line and is convenient for wiring and layout of equipment.

In another aspect, the pre-cured heat conducting functional layer is laminated and compounded with the short fiber assembly layer in a pre-cured state, so that relatively high bonding strength can be formed between the heat conducting functional layer 1 and the fiber layer 2 of the fiber plate after compression molding.

Example 5

Example 5 differs from example 4 in that, referring to fig. 4, the fiber board is composed of a heat conductive functional layer 1 and a fiber layer 2. Specifically, the thickness of the heat conductive functional layer 1 is 1.0mm, and fiber layers 2',2 "having thicknesses of 1.0mm and 2.0mm are respectively adhered to the surface and the bottom of the heat conductive functional layer 1.

The fiberboard of example 5 also differs slightly in manufacturing method from example 4 due to slight difference in structure.

In the staple fiber assembly step, a fiber paver or other device of the prior art is used to deliver the rubberized staple fibers onto a continuous conveyor belt to lay flat to form a continuous lower fiber blank layer. Subsequently, a pre-cured thermally conductive functional layer is overlaid on top of the staple fiber assembly layer. And finally, repeating the step of short fiber assembly, and flatly paving the same or another fiber spreading machine on the pre-cured heat conducting functional layer to form a continuous upper fiber blank layer, so as to form a composite assembly layer consisting of the upper fiber blank layer, the pre-cured heat conducting functional layer and the lower fiber blank layer. And then pressing to obtain the fiber board through a hot press molding step.

The product properties of the fiberboard produced by the process of example 4 and example 5 are shown in Table 4.

TABLE 4 product Properties of the fiberboard prepared by the process of example 4 and example 5

As can be seen from the data in table 5, in the case where the thicknesses of the heat conductive functional layers 1 and the thicknesses (total thicknesses) of the fiber layers 2 are the same in the fiber boards of example 4 and example 5, a structure in which the heat conductive functional layer 1 is disposed between the two fiber layers 2 can obtain relatively high heat conductive performance, but the increase is not large.

Example 6

Example 6 differs from example 1 in that the adhesives used in the step of wood fiber glue blending are all resin adhesives modified with lignin as a partial phenol substitute raw material, for example, phenolic resin adhesives modified with lignin as a partial phenol substitute raw material, and the heat conductive functional layer 1G is obtained by pressing.

The lignin is utilized to replace part of phenolic resin adhesive modified by phenol raw materials, so that the crosslinking of long fibers (wood fibers A) can be promoted, and the formed mesh bag-shaped structure is firmer. The product properties of the heat conductive functional layer 1 of example 6 are shown in table 5.

TABLE 5 Table of product Properties of Heat conducting functional layer 1 of example 6

Group of	Density (g/m) ³ )	Internal bond Strength (MPa)
			Heat conduction functional layer 1C	0.96	1.9
Heat conduction functional layer 1G	0.94	2.1

The foregoing description is for purposes of illustration and is not intended to be limiting. Many embodiments and many applications other than the examples provided will be apparent to those of skill in the art upon reading the above description. The scope of the present teachings should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are incorporated herein by reference for the purpose of completeness. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended to forego such subject matter, nor should the applicant be deemed to have such subject matter not considered to be part of the subject matter of the disclosed application.

Claims

1. A fiber board comprising a heat-conducting functional layer, wherein the heat-conducting functional layer comprises wood fibers and graphite components which are mixed with each other and bonded by an adhesive, and is characterized in that the wood fibers comprise wood fibers A with the fiber length of 7-10 mm and wood fibers B with the fiber length of 5-7 mm, and the fiber diameter of the wood fibers is 0.05-0.08 mm; the graphite component is graphite particles with the particle size of 0.4-0.5 mm or small graphite sheets with the length of 1.0-3.3 mm and the thickness of 0.07-0.09 mm, and the addition amount of the graphite component accounts for 25-40% of the total mass of the mixture formed by wood fiber, adhesive and graphite component;

the preparation method of the fiberboard comprises the steps of hot-press molding, namely sequentially carrying out a step of wood fiber glue mixing, a step of graphite component mixing, a step of mixture assembly, a step of preforming and a step of cooling and drying to prepare a pre-cured heat conduction functional layer;

in the step of mixing the wood fiber, firstly mixing the wood fiber A, then adding the wood fiber B according to a proportion, and transferring part of adhesive on the surface of the wood fiber A to the surface of the wood fiber B by continuous turning and mutual friction to realize the mixing of the wood fiber A and the wood fiber B and the mixing of the wood fiber B, wherein the initial water content of the wood fiber A is 17+/-1%, the initial water content of the wood fiber B is 15+/-1%, the water content of the wood fiber after the mixing is 30-35%, and the step of directly implementing the step of assembling the mixture without the step of drying the mixture after the step of mixing the graphite components;

in the preforming step, the adhesive is pre-cured through non-pressure thermal contact to obtain the pre-cured heat conducting functional layer, wherein the thermal contact temperature is 120-140 ℃;

in the cooling and drying step, the moisture content of the pre-cured heat conducting functional layer obtained in the preforming step is reduced to 16% -20%.

2. The fiberboard according to claim 1, characterized in that the thickness of the heat conductive functional layer is 0.2 mm-2 mm.

3. The fiber board according to claim 2, characterized in that the surface and/or bottom surface of the heat conducting functional layer is provided with a fiber layer comprising short fibers bonded by an adhesive, the fiber length of the short fibers being 0.5 mm-3 mm.

4. A fiberboard according to claim 3, characterized in that the heat-conducting functional layer and the fibrous layer use the same kind of adhesive.

5. The fiber board according to claim 1, wherein a lower fiber blank layer is prepared by the steps of short fiber glue mixing and short fiber blank assembling in sequence, and the pre-cured heat conduction functional layer is arranged on the lower fiber blank layer; and/or

finally, the fiberboard is manufactured through a hot press molding step.

6. The fiber board according to claim 5, wherein the adhesive used in the step of mixing wood fiber and the step of mixing short fiber is a resin adhesive modified by using lignin as a partial substitute raw material.