CN117484631A

CN117484631A - A glue-free straw fiber board and its preparation method

Info

Publication number: CN117484631A
Application number: CN202311380075.2A
Authority: CN
Inventors: 张永超; 徐卿瑕; 傅英娟; 秦梦华
Original assignee: Qilu University of Technology
Current assignee: Qilu University of Technology
Priority date: 2023-10-24
Filing date: 2023-10-24
Publication date: 2024-02-02
Anticipated expiration: 2043-10-24
Also published as: CN117484631B

Abstract

The invention discloses a glue-free straw fiber board and a preparation method thereof, and belongs to the field of fiber board production. The preparation method of the glue-free straw fiber board comprises the following steps: 1) The method comprises the steps of carrying out component separation on straw raw materials through an organic solvent containing a small molecule auxiliary agent, and carrying out in-situ activation on dissolved lignin and hemicellulose through the small molecule auxiliary agent while carrying out component separation; 2) Evaporating, concentrating and drying the separated and activated mixture, gradually separating out lignin and hemicellulose activated products in the organic solvent on the surface of cellulose fiber solid, and re-assembling with the cellulose solid to obtain the cellulose fiber solid material coated by the activated products in a self-assembly way; 3) And hot-press molding the dried solid material. Compared with the prior art, the production process of the glue-free straw fiber board adopts a one-pot method, and the fiber board with higher tensile strength can be obtained without adding any external adhesive, so that the process is simple, environment-friendly and pollution-free.

Description

Non-glue straw fiber board and preparation method thereof

Technical Field

The invention relates to the field of production of straw fiber boards, and particularly provides a glue-free straw fiber board and a preparation method thereof.

Background

Straw is a general term for the stem and leaf (ear) parts of mature crops, and is usually the rest of wheat, rice, corn, potatoes, oil, cotton, sugarcane and other crops after harvesting seeds, so that the straw is a renewable biological resource with low cost and multiple purposes. The main chemical component content (cellulose, hemicellulose and lignin) of the crop straw is similar to that of wood, and can be completely used for replacing wood to manufacture artificial boards. The crop straw is used for the artificial board industry, is an effective way for solving the contradiction between the insufficient wood supply and the large board demand, and can change waste into valuables, avoid the waste of straw resources and the environmental pollution caused by burning the straw, and increase the income of farmers.

In the conventional wood processing method, synthetic resins such as phenol resin and urea resin are mostly used as adhesives to manufacture various artificial boards. However, the conventional synthetic resin adhesive contains a large amount of free formaldehyde, which not only causes air pollution, but also has great harm to the health of people. The glue-free plywood adopts the composite additive to replace the traditional chemical products such as synthetic resin adhesive and the like, realizes the bonding effect by the crosslinking effect among the components of the raw materials of the composite filler in the hot pressing process, does not contain harmful substances such as formaldehyde and the like, and is a green product which has no pollution to the environment and no public hazard to human bodies.

The invention discloses a production process of a non-glue and non-aldehyde fiberboard for straw co-production of fulvic acid, which takes non-wood fiber as a raw material and carries out full-element purification, activation, saccharification treatment and separation through digestion and fluffing to obtain primarily activated lignin, purified and activated fiber, hemicellulose, non-wood fiber monosaccharide and fulvic acid; and (3) carrying out deep activation treatment on the activated lignin. Fully activated lignin and low molecular monosaccharide are used as curing agent and binder to produce the glue-free and aldehyde-free fiber board. Through the full activation of lignin, the comprehensive utilization of straw fiber resources is realized, and the special requirements of the glue-free aldehyde-free fiber board on high-quality fiber raw materials and high-activity lignin are effectively met; the distilled water obtained by directly extracting and concentrating the boiled thin black liquor is recycled by concentrating the boiled thin black liquor to obtain fulvic acid.

The patent document with publication number CN201410011629.6 discloses a method for manufacturing a bamboo fiber glue-free board, which sequentially comprises the processes of thermal fiber grinding, drying, paving, prepressing, sawing, hot-press forming, cooling and edge cutting, wherein the hot-press temperature is 160-230 ℃ and the hot-press pressure is 30kg/cm during hot-press ² ～85kg/cm ² And (3) carrying out hot pressing for 5-30 min to obtain the bamboo fiber glue-free board, degrading chemical component substances in the bamboo fibers at high temperature and high pressure to generate substances with low molecular weight and natural adhesive properties, and then bonding the undegraded bamboo fibers together under the action of temperature and pressure to form the glue-free environment-friendly board with higher mechanical properties. The bamboo fibers are formed into the plate through degradation and combination, and the adhesive is not needed to be provided in the process, so that the use of the adhesive is effectively reduced, and the production cost and pollution are reduced.

The above patent relates to a process for producing a plate without an adhesive, which avoids the problem that formaldehyde is released in the plate to harm health, and is beneficial to promoting the high-value utilization of non-wood biomass raw materials. However, the above process involves a relatively complex production flow, and multiple lignin activation and thermal defibration processes can generate a large amount of energy consumption, thereby greatly increasing the production cost.

The patent document with publication number CN101234504A discloses a method for manufacturing a flash evaporation defibration glue-free light crop straw fiber composite material, which comprises the steps of crushing straw raw materials into units with the length of 20-30 mm and the water content of 50-60%, putting the straw units into a steam explosion processor, introducing high-temperature high-pressure saturated steam for boiling, and then instantly and suddenly opening a valve to release pressure for discharging, wherein a two-stage steam explosion treatment process is adopted: pretreating the straw unit for 5-8 min under lower steam pressure, treating for 2-5 min under higher steam pressure, and suddenly opening a valve to release pressure for discharging to obtain dissociated fibers; forming a plate blank; adopting a closed steam-spraying hot-pressing process, wherein the steam pressure is 0.6-1.0 MPa, the steam-spraying time is 10-30 s, the periphery of the plate blank is closed after the steam-spraying, the hot-pressing temperature is 180-190 ℃, and the hot-pressing time is 4-15 min. The advantages are that: no environmental pollution exists in the production and use processes of the product; the sizing process is omitted, and the production cost is reduced; and (5) preparing light boards with different thicknesses.

The patent document with publication number of CN110253708A discloses a production process of a high-strength straw non-glue board and a board, and the production process of the straw non-glue board comprises the following steps: 1) Extracting fibers: extracting plant fibers from straw, steam-blasting the plant fibers, and mixing the plant fibers with alkali solution for activation; 2) Short rod steam explosion: preparing short rods from the straw, steam-blasting the short rods, and mixing the short rods with alkali solution for activation; 3) Steam explosion of powder: preparing straw into powder, steam-blasting the powder, and mixing the powder with alkali solution for activation; 4) Pressing a plate: mixing and pressing the materials obtained in the steps 1) to 3) into a plate.

The above patent adopts the process of carrying out steam explosion on agricultural straws, and the steam explosion mainly carries out physical decomposition on fiber raw materials, and a large amount of lignin and hemicellulose are difficult to dissolve out from the raw materials in a degradation mode, so that the lignin and the hemicellulose are difficult to play a good role in bonding performance, thereby affecting the mechanical properties of formed plates and leading to lower strength of the plates.

Patent document with publication number of CN202210039932.1 discloses a raw material of a non-glue fiberboard, a preparation method thereof and the non-glue fiberboard, belonging to the technical field of fiberboards. The invention treats wood chips by carbonized wastewater: firstly, carrying out rotary distillation on carbonized wastewater to obtain distillate and residue, wherein the distillate contains various acidic substances, so that the acid decomposition effect on wood chips can be realized, lignin and hemicellulose in the wood chips are degraded into guaiacol and phenol substances in the high-temperature and high-pressure treatment process, and the adhesive effect can be realized in the process of preparing boards; and then adding the residual part of carbonized wastewater, wherein the residual part is mainly lignin carbonized degradation product, which can further play a role of gluing, thereby improving the mechanical property of the board.

The patent document with publication number of CN202110487853.2 proposes a preparation method of a glue-free wheat straw board, wherein wheat straw is processed into wheat straw particles by using a physical crushing means, active sites embedded in the particles are released by alkali treatment, the straws are modified by chloroacetic acid and acryloyl chloride, and green and environment-friendly hydrogen peroxide is used as a crosslinking polymerization initiator, so that the board with super-strong mechanical property is prepared.

The process adopts a chemical method to carry out acidolysis or alkali treatment on biomass raw materials, and promotes the bonding performance of lignin and hemicellulose to fibers through chemical reaction, however, a large amount of inorganic chemicals are used in the process, and residual acid or residual alkali after reaction can be remained in the plate, so that the recovery and the reuse are difficult. Secondly, the process can generate a large amount of wastewater in the production process, and the environmental load in the production process is high.

In summary, the preparation of the non-glue fiberboard generally adopts a relatively complex production process, and the existing process technology has the problems of high energy consumption, difficult recovery of chemicals, large environmental load and the like, so that the production cost of the fiberboard is greatly increased.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a preparation method of a glue-free straw fiber board with simple process and environmental protection.

The technical scheme adopted for solving the technical problems is as follows: a preparation method of a glue-free straw fiber board comprises the following steps:

(1) The method comprises the steps of carrying out component separation on a straw raw material by an organic solvent containing a small molecule auxiliary agent, and carrying out in-situ activation on dissolved lignin and hemicellulose by the small molecule auxiliary agent while carrying out component separation, wherein the small molecule auxiliary agent is glycol or small molecule phenolic compound;

(2) Separating and activating the mixture, evaporating, concentrating, drying and recovering the organic solvent, wherein lignin and hemicellulose in the organic solvent are gradually separated out on the surface of cellulose fiber solid in the evaporating, concentrating and drying processes, and are reassembled with the cellulose solid to obtain the cellulose fiber solid material coated by the self-assembly of the activation product;

(3) And carrying out hot press molding on the dried solid material to obtain the glue-free straw fiber board.

Preferably, the straw raw material is segment-shaped straw with the length of 2-3cm, and the straw can be straw, corn stalk, wheat stalk, giant fungus grass, arundo donax, bamboo, furniture board waste leftovers and the like.

Preferably, the mass ratio of the small molecule auxiliary agent to the organic solvent is 1 (5-15), particularly preferably 1 (8-12).

Preferably, the small molecule auxiliary agent is one or a mixture of more than two of ethylene glycol, 1, 3-propylene glycol, 2, 3-butanediol, phenol, catechol, phloroglucinol and resorcinol.

Preferably, the organic solvent is one or a mixture of more than two of formic acid, acetic acid, lactic acid, oxalic acid, methanol and ethanol.

Preferably, the feed liquid ratio (mass ratio) of the straw raw material to the organic solvent is 1 (5-15), and particularly preferably 1 (8-12).

Preferably, the isolation activation temperature in step (1) is from 50 to 180 ℃, particularly preferably from 90 to 150 ℃, most preferably from 120 to 140 ℃; the separation activation time is 0.5 to 5 hours, particularly preferably 2 to 4 hours, and most preferably 2 to 3 hours.

Preferably, step (2) is performed by vacuum evaporation concentration drying of the mixture at 70-90℃and 0.01-0.05 MPa. The drying temperature is particularly preferably from 80 to 90℃and the pressure is particularly preferably from 0.01 to 0.02MPa.

Preferably, the solids content of the dried material of step (2) is from 50 to 90%, particularly preferably from 60 to 70%.

Preferably, in step (3), the hot pressing temperature is 120 to 220 ℃, particularly preferably 130 to 180 ℃; the hot-pressing pressure is 5-40MPa, particularly preferably 10-20MPa; the hot pressing time is 5 to 15min, particularly preferably 5 to 10min.

The glue-free straw fiber board prepared by the preparation method provided by the invention has smooth appearance surface, the tensile strength can reach 7-10MPa, the fiber boards with different specifications can be obtained by simple mechanical cutting, and the performance requirements of building materials and furniture boards can be met.

According to the invention, the components of the straw raw material are separated by the organic solvent containing the micromolecular auxiliary agent, lignin is modified in situ in the separation process, so that the chemical reactivity of lignin is improved, extracted lignin and hemicellulose degradation products are reassembled with cellulose fibers to form hemicellulose and lignin degradation modified products coated cellulose fiber solids, and the glue-free straw fiber board is obtained by further hot pressing, and compared with the prior art, the glue-free straw fiber board has the following outstanding beneficial effects:

the whole technological process adopts a one-pot method, plays roles of bonding hemicellulose and lignin and rigid supporting of cellulose fibers, and can obtain a fiber board with higher tensile strength under the condition of no need of adding any external adhesive;

the reaction is finished without further separation and purification, the operation flow is simple, the energy consumption is low, chemicals are easy to recycle, and the method is environment-friendly;

the lignin is activated synchronously in the separation process, so that the process flow is shortened;

fourth, the wet hot press molding and the anhydrous process are not needed;

and (V) the full component is utilized, and a new feasible technical scheme is provided for the full utilization of the straw.

Detailed Description

The invention will now be further illustrated with reference to specific examples, which are not intended to limit the scope of the invention.

The contents of the respective components used below are mass percent unless otherwise specified.

Example 1:

weighing 100g of corn straw, adding 1000g of 85% formic acid (mass fraction) into 100g of ethylene glycol, fully mixing, fully reacting for 2 hours at 120 ℃, and after the reaction is finished, carrying out vacuum evaporation concentration and drying on a mixture system of all products and cooking liquor at 80 ℃ and 0.01Mpa, wherein the recovered cooking reagent is used for repeated use. And (3) carrying out hot press molding on the dried solid (solid content is 65%) to obtain the glue-free fiber board. The hot pressing pressure is 15MPa, the hot pressing temperature is 140 ℃, and the hot pressing time is 10min. According to the GB/T17657-2022 standard requirement, the non-glue fiber board is cut into a standard test piece, and the tensile strength of the test piece is measured to be 8.8MPa.

Example 2:

weighing 100g of corn straw, adding 1000g of 85% ethanol (mass fraction) into 100g of glycol, fully mixing, fully reacting for 2 hours at 170 ℃, and after the reaction is finished, carrying out vacuum evaporation, concentration and drying on a mixture system of all products and cooking liquor at 80 ℃ and 0.01Mpa, wherein the recovered cooking reagent is reused. And (3) carrying out hot press molding on the dried solid (solid content is 65%) to obtain the glue-free fiber board. The hot pressing pressure is 15MPa, the hot pressing temperature is 140 ℃, and the hot pressing time is 10min. According to the GB/T17657-2022 standard requirement, the glue-free fiber board is cut into a standard test piece, and the tensile strength of the test piece is measured to be 7.4MPa.

Example 3:

weighing 100g of arundo donax, adding 1000g of 85% formic acid (mass fraction) into 100g of ethylene glycol, fully mixing, fully reacting for 2 hours at 140 ℃, and after the reaction is finished, carrying out vacuum evaporation, concentration and drying on a mixture system of all products and cooking liquor at 80 ℃ and 0.01Mpa, wherein the recovered cooking reagent is reused. And (3) carrying out hot press molding on the dried solid (solid content is 65%) to obtain the glue-free fiber board. The hot pressing pressure is 15MPa, the hot pressing temperature is 140 ℃, and the hot pressing time is 10min. According to the GB/T17657-2022 standard requirement, the non-glue fiber board is cut into a standard test piece, and the tensile strength of the test piece is measured to be 9.2MPa.

Example 4:

100g of furniture waste leftovers are weighed, 1000g of 85% formic acid (mass fraction) is added into 100g of ethylene glycol for full mixing, the mixture is fully reacted for 2 hours at 140 ℃, and after the reaction is finished, the mixture system of all products and cooking liquor is subjected to vacuum evaporation, concentration and drying at 80 ℃ and 0.01Mpa, and the recovered cooking reagent is reused. And (3) carrying out hot press molding on the dried solid (solid content is 65%) to obtain the glue-free fiber board. The hot pressing pressure is 15MPa, the hot pressing temperature is 140 ℃, and the hot pressing time is 10min. According to the GB/T17657-2022 standard requirement, the non-glue fiber board is cut into a standard test piece, and the tensile strength of the test piece is measured to be 9.1MPa.

Example 5:

weighing 100g of corn straw, adding 1000g of 85% formic acid (mass fraction) into 100g of phenol, fully mixing, fully reacting for 2 hours at 120 ℃, after the reaction is finished, carrying out vacuum evaporation, concentration and drying on a mixture system of all products and cooking liquor at 80 ℃ and 0.01Mpa, recycling the recovered cooking reagent, and carrying out hot press molding on dried solid (solid content of 65%) to obtain the glue-free fiber board. The hot pressing pressure is 15MPa, the hot pressing temperature is 150 ℃, and the hot pressing time is 8min. According to the GB/T17657-2022 standard requirement, the non-glue fiber board is cut into a standard test piece, and the tensile strength of the test piece is measured to be 9.0MPa.

Example 6:

weighing 100g of wheat, adding 1000g of 85% formic acid (mass fraction) into 100g of ethylene glycol, fully mixing, fully reacting for 2 hours at 120 ℃, and after the reaction is finished, carrying out vacuum evaporation, concentration and drying on a mixture system of all products and cooking liquor at 80 ℃ and 0.01Mpa, wherein the recovered cooking reagent is reused. And (3) carrying out hot press molding on the dried solid (solid content is 65%) to obtain the glue-free fiber board. The hot pressing pressure is 15MPa, the hot pressing temperature is 160 ℃, and the hot pressing time is 5min. According to the GB/T17657-2022 standard requirement, the non-glue fiber board is cut into a standard test piece, and the tensile strength of the test piece is measured to be 8.4MPa.

Example 7:

100g of corn straw is weighed, 1000g of 85% formic acid (mass fraction) is added into 80g of ethylene glycol for full mixing, the mixture is fully reacted for 2 hours at 120 ℃, after the reaction is finished, the mixture system of all products and cooking liquor is evaporated, concentrated and dried in vacuum at 80 ℃ and 0.01Mpa, and the recovered cooking reagent is used for repeated use. And (3) carrying out hot press molding on the dried solid (solid content is 65%) to obtain the glue-free fiber board. The hot pressing pressure is 15MPa, the hot pressing temperature is 140 ℃, and the hot pressing time is 10min. According to the GB/T17657-2022 standard requirement, the glue-free fiber board is cut into a standard test piece, and the tensile strength of the test piece is measured to be 7.8MPa.

Example 8:

weighing 100g of corn straw, adding 1000g of 85% formic acid (mass fraction) into 100g of resorcinol, fully mixing, fully reacting for 2 hours at 120 ℃, and after the reaction is finished, carrying out vacuum evaporation concentration and drying on a mixture system of all products and cooking liquor at 80 ℃ and 0.01Mpa, wherein the recovered cooking reagent is used for repeated use. And (3) carrying out hot press molding on the dried solid (solid content is 65%) to obtain the glue-free fiber board. The hot pressing pressure is 15MPa, the hot pressing temperature is 140 ℃, and the hot pressing time is 10min. According to the GB/T17657-2022 standard requirement, the non-glue fiber board is cut into a standard test piece, and the tensile strength of the test piece is measured to be 9.0MPa.

Example 9:

weighing 100g of corn straw, adding 1000g of 85% formic acid (mass fraction) into 100g of pyrogallol, fully mixing, fully reacting for 2 hours at 120 ℃, after the reaction is finished, carrying out vacuum evaporation concentration and drying on a mixture system of all products and cooking liquor at 80 ℃ and 0.01Mpa, and recycling the cooking reagent for reuse. And (3) carrying out hot press molding on the dried solid (solid content is 65%) to obtain the glue-free fiber board. The hot pressing pressure is 15MPa, the hot pressing temperature is 140 ℃, and the hot pressing time is 10min. According to the GB/T17657-2022 standard requirement, the non-glue fiber board is cut into a standard test piece, and the tensile strength of the test piece is measured to be 9.1MPa.

Example 10:

100g of corn straw is weighed, 1000g of 85% formic acid (mass fraction) is added into 100g of 1, 3-propanediol for full mixing, the mixture is fully reacted for 2 hours at 120 ℃, after the reaction is finished, the mixture system of all products and cooking liquor is subjected to vacuum evaporation concentration and drying at 80 ℃ and 0.01Mpa, and the recovered cooking reagent is used for repeated use. And (3) carrying out hot press molding on the dried solid (solid content is 65%) to obtain the glue-free fiber board. The hot pressing pressure is 15MPa, the hot pressing temperature is 140 ℃, and the hot pressing time is 10min. According to the GB/T17657-2022 standard requirement, the non-glue fiber board is cut into a standard test piece, and the tensile strength of the test piece is measured to be 8.3MPa.

Example 11:

100g of corn straw is weighed, 1000g of 85% formic acid (mass fraction) is added into 100g of 2, 3-butanediol to be fully mixed, the mixture is fully reacted for 2 hours at 120 ℃, after the reaction is finished, the mixture system of all products and cooking liquor is subjected to vacuum evaporation concentration and drying at 80 ℃ and 0.01Mpa, and the recovered cooking reagent is used for repeated use. And (3) carrying out hot press molding on the dried solid (solid content is 65%) to obtain the glue-free fiber board. The hot pressing pressure is 15MPa, the hot pressing temperature is 140 ℃, and the hot pressing time is 10min. According to the GB/T17657-2022 standard requirements, the non-glue fiber board is cut into a standard test piece, and the tensile strength of the test piece is measured to be 8.1MPa.

Example 12:

weighing 100g of corn straw, adding 1000g of 85% formic acid (mass fraction) into 100g of ethylene glycol, fully mixing, fully reacting for 2 hours at 120 ℃, and after the reaction is finished, carrying out vacuum evaporation concentration and drying on a mixture system of all products and cooking liquor at 80 ℃ and 0.01Mpa, wherein the recovered cooking reagent is used for repeated use. And (3) carrying out hot press molding on the dried solid (solid content is 60%) to obtain the glue-free fiber board. The hot pressing pressure is 15MPa, the hot pressing temperature is 140 ℃, and the hot pressing time is 10min. According to the GB/T17657-2022 standard requirement, the non-glue fiber board is cut into a standard test piece, and the tensile strength of the test piece is measured to be 8.2MPa.

Example 13:

weighing 100g of corn straw, adding 1000g of 85% formic acid (mass fraction) into 100g of ethylene glycol, fully mixing, fully reacting for 2 hours at 120 ℃, and after the reaction is finished, carrying out vacuum evaporation concentration and drying on a mixture system of all products and cooking liquor at 80 ℃ and 0.01Mpa, wherein the recovered cooking reagent is used for repeated use. And (3) carrying out hot press molding on the dried solid (with the solid content of 70%) to obtain the glue-free fiber board. The hot pressing pressure is 15MPa, the hot pressing temperature is 140 ℃, and the hot pressing time is 10min. According to the GB/T17657-2022 standard requirement, the non-glue fiber board is cut into a standard test piece, and the tensile strength of the test piece is measured to be 8.3MPa.

Example 14:

weighing 100g of corn straw, adding 1000g of 85% formic acid (mass fraction) into 100g of ethylene glycol, fully mixing, fully reacting for 2 hours at 120 ℃, and after the reaction is finished, carrying out vacuum evaporation, concentration and drying on a mixture system of all products and cooking liquor at 90 ℃ and 0.02Mpa, wherein the recovered cooking reagent is used for repeated use. And (3) carrying out hot press molding on the dried solid (solid content is 65%) to obtain the glue-free fiber board. The hot pressing pressure is 15MPa, the hot pressing temperature is 140 ℃, and the hot pressing time is 10min. According to the GB/T17657-2022 standard requirement, the glue-free fiber board is cut into a standard test piece, and the tensile strength of the test piece is measured to be 7.4MPa.

Claims

1. A method for preparing glue-free straw fiber sheets, which is characterized by comprising:

(1) Use organic solvents containing small molecule additives to separate the components of the straw raw material. While the components are separated, the small molecule additives activate the dissolved lignin and hemicellulose in situ. The small molecule additives It is a glycol or small molecule phenolic compound;

(2) The separated and activated mixture is evaporated, concentrated and dried to recover the organic solvent. The activation products of lignin and hemicellulose in the organic solvent gradually precipitate on the surface of the cellulose fiber solid during the evaporation, concentration and drying process, and interact with the cellulose solid. Reassemble to obtain a cellulose fiber solid material self-assembled and coated by the activation product;

(3) The dried solid material is hot-pressed to obtain glue-free straw fiber sheets.

2. The preparation method of glue-free straw fiber board according to claim 1, characterized in that: the mass ratio of small molecule additives and organic solvents in step (1) is 1: (5-15).

3. The preparation method of glue-free straw fiber board according to claim 1 or 2, characterized in that:

The small molecule additive is one or more of two or more substances selected from the group consisting of ethylene glycol, 1,3-propanediol, 2,3-butanediol, phenol, catechol, phloroglucinol and resorcinol. mixture.

The organic solvent is one or a mixture of two or more substances among formic acid, acetic acid, lactic acid, oxalic acid, methanol and ethanol.

4. The preparation method of glue-free straw fiber board according to claim 3, characterized in that: the material-liquid ratio of straw raw material and organic solvent is 1: (5-15).

5. The preparation method of glue-free straw fiber board according to claim 4, characterized in that: in step (1), the separation activation temperature is 50-180°C, and the separation activation time is 0.5-5h.

6. The preparation method of glue-free straw fiber board according to claim 5, characterized in that: step (2) carries out vacuum evaporation, concentration and drying of the mixture at 70-90°C and 0.01-0.05Mpa, and the solid content of the material after drying is Content is 50-90%.

7. The method for preparing glue-free straw fiber sheets according to claim 6, characterized in that in step (3), the hot pressing temperature is 120-220°C and the hot pressing pressure is 5-40 MPa.

8. The glue-free straw fiber board obtained by the preparation method according to any one of claims 1-7.