A method for preparing medium-density fiberboard based on discarded mushroom sticks

Abstract

The present invention provides a method for preparing medium-density fiberboard based on waste mushroom sticks, which relates to the field of biomass utilization and comprises the following steps: (1) crushing the waste mushroom sticks with a machine to crack the mushroom sticks; (2) spraying the crushed waste mushroom sticks with a borax solution to fully swell the crushed waste mushroom sticks; (3) steam-exploding the swollen waste mushroom sticks; (4) grinding the exploded mushroom sticks to disperse the fibers in the mushroom sticks, and adding an appropriate amount of water to cool and dilute the fibers after the grinding; (5) drying the dispersed mushroom stick fibers; (6) dissolving a phenolic adhesive in ethanol and mixing the mixture with the dried mushroom stick fibers to obtain a mixture; (7) volatilizing the ethanol in the mixture; and (8) placing the volatilized raw material in a hot press and hot-pressing to prepare a mushroom stick-based medium-density fiberboard. The present invention can reduce environmental pollution caused by waste mushroom sticks and simultaneously produce a medium-density fiberboard with good antibacterial and mechanical properties, thereby having good economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of biomass utilization, and in particular to a method for preparing a medium-density fiberboard based on discarded mushroom sticks. Background Art

[0002] In 2021, China's mushroom production reached 41.3 million tons, accounting for 70% of the global mushroom production. As a result, this prolific industry produces about 200 million tons of mushroom substrate (MS), also called mushroom sticks, each year. A mushroom stick is a cylindrical bag used to inoculate various types of edible fungi, including morels, button mushrooms, and straw mushrooms. Typically, mushroom sticks consist of a mixture of materials such as cottonseed hulls, sawdust, corn cobs, various agricultural by-products and residues, which are carefully combined in proportion. As edible fungi grow on the substrate, the cellulose and hemicellulose components gradually decompose. Therefore, the main chemical component of discarded mushroom sticks is lignin, which shows significant resistance to decomposition.

[0003] Until now, waste mushroom sticks have been significantly underutilized. Typically, waste mushroom sticks are disposed of by discarding, incinerating, or landfilling, all of which carry the risk of soil and water contamination. Alternatively, it is used as animal feed or fertilizer. However, another issue in waste mushroom stick management is the unpleasant odor it emits during handling, stacking, and transportation. To address these key challenges and contribute to promoting the environmentally responsible treatment of waste mushroom sticks, our main goal was to investigate their potential for use in the production of wood composites. This work aims to provide large-scale, value-added applications for waste mushroom sticks.

[0004] Medium-density fiberboard (MDF) is a widely used building material renowned for its versatility and strength. Typically, MDF is produced by mechanically or chemically pulverizing wood or other plant materials into a fiber powder. This fiber powder is then formed into MDF sheets through hot pressing at high temperatures and high pressures. However, the bond strength and mechanical properties of MDF cannot rely solely on hydrogen bonds between fibers. Therefore, the MDF manufacturing process requires the use of adhesives and water-repellents.

[0005] Edible mushrooms have fully digested the carbohydrate components of their logs, and the waste MS has a higher lignin content. Lignin, a polymer composed of phenylpropane units, encapsulates cellulose and hemicellulose within the plant, acting as an adhesive and imparting mechanical elasticity to the fibers. Lignin is a thermosetting polymer that softens at high temperatures. When subjected to high temperatures, lignin has the potential to act as a natural adhesive. Summary of the Invention

[0006] The present invention provides a method for producing medium-density fiberboard (MDF) from discarded mushroom sticks. This method aims to provide a new approach for reusing discarded mushroom sticks, reducing the ecological pollution caused by the indiscriminate disposal of discarded mushroom sticks. Furthermore, using discarded mushroom sticks to produce MDF reduces the cost of raw materials for fiberboard production. Furthermore, due to the unique properties of discarded mushroom sticks, they can serve as both a bioadhesive and a waterproofing agent, reducing the amount of adhesive and waterproofing agent used in the fiberboard manufacturing process, resulting in better economic benefits.

[0007] In order to solve the above problems, the technical solution adopted by the present invention is:

[0008] A method for preparing medium-density fiberboard based on discarded mushroom sticks comprises the following steps:

[0009] (1) The discarded mushroom sticks are crushed by a machine to crack the mushroom sticks and facilitate water penetration;

[0010] (2) preparing a 0.5-1% w / v borax solution;

[0011] (3) spraying the solution prepared in step (2) onto the discarded mushroom sticks after rolling in step (1) at a ratio of 50 to 200% of the dry weight of the mushroom sticks, and stirring appropriately to ensure that the mushroom sticks are evenly and fully moistened;

[0012] (4) steam explosion treatment of the discarded mushroom sticks after being fully swollen in step (3);

[0013] (5) grinding the mushroom sticks after steam explosion in step (4) to disperse the fibers in the mushroom sticks, and adding an appropriate amount of water to cool and dilute the fibers after grinding;

[0014] (6) drying the dispersed mushroom stick fibers in air or with hot air;

[0015] (7) dissolving a phenolic adhesive in ethanol and then mixing the mixture with the dried mushroom stick fibers to obtain a mixture, wherein the amount of the phenolic adhesive is 0 to 5% of the mass of the dried mushroom sticks;

[0016] (8) exposing the mixture of step (7) to air to allow some of the ethanol to evaporate;

[0017] (9) Then, the raw materials of step (8) are placed in a hot press, the pressure is controlled at 20 MPa, the temperature is controlled at 150-190° C., and the hot pressing time is 10-30 minutes to prepare a mushroom stick-based medium density fiberboard.

[0018] Preferably, the waste mushroom sticks are allowed to swell for at least 8 hours, and the steam explosion treatment effect is better.

[0019] Preferably, the optimal conditions for steam explosion treatment of discarded mushroom sticks are: steam pressure 1 MPa, pressure holding time 300 s.

[0020] Preferably, the gap of the disc grinding is adjusted to 0.2 mm during fiber dispersion, and the fiber concentration after dilution is controlled to be 15-25%.

[0021] Preferably, the moisture content of the dried mushroom stick fibers is 15-30%.

[0022] The present invention utilizes steam explosion pretreatment technology to disperse mushroom stick fibers, and at the same time, redisperses and activates lignin. Finally, the fiberized mushroom stick raw materials are mixed with a sizing agent and hot-pressed. By utilizing the characteristics of high lignin content in the mushroom sticks, the activation function of edible fungi and steam explosion on lignin, the dispersion effect of steam explosion, and the condensation effect of hot pressing on lignin, a mushroom stick composite that meets the quality requirements of high-quality medium-density fiberboard is obtained, and the mushroom stick composite is then used to prepare medium-density fiberboard with high mechanical strength and excellent water stability.

[0023] Beneficial effects of the present invention:

[0024] (1) The present invention provides a large-scale application method for the utilization of waste mushroom sticks, making full use of the rich lignin contained in the waste mushroom sticks, making them serve as both a bioadhesive and a waterproofing agent, thereby reducing the amount of adhesive and waterproofing agent used in the manufacturing process of medium-density fiberboard. At the same time, it can prevent the waste mushroom sticks from being discarded arbitrarily and causing pollution to the ecological environment.

[0025] (2) The present invention utilizes steam explosion technology to disperse the fibers while also uniformly dispersing the lignin. In particular, the lignin aggregates formed by steam explosion have an activation effect on the lignin, which is beneficial for the subsequent condensation and formation of the lignin during hot pressing, thereby producing a medium-density fiberboard with high mechanical strength and excellent water stability.

[0026] (3) Using waste mushroom sticks to prepare medium-density fiberboard can save raw material costs and recycle waste, which can produce better economic benefits.

[0027] (4) Adding borax during the swelling of the mushroom logs not only makes the final product have antiseptic properties, but we also found that the addition of appropriate borax can promote the swelling of water in the fiber cell wall, thereby making the steam explosion effect better. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Figures showing the fiber morphology of the mushroom sticks after steam explosion treatment in Example 3. (a) Fiber morphology of the mushroom sticks under a 4x microscope; (b) Fiber morphology of the mushroom sticks under a 10x microscope.

[0029] Figure 2 The thermal reaction performance changes before and after the mushroom stick treatment in Example 3. (a) TG curve of mushroom stick and medium density board of mushroom stick; (b) DTG curve of mushroom stick and medium density board of mushroom stick;

[0030] Figure 3 The following are microscopic images of the surface of the medium density board obtained in each example. (a) Microscopic image of the surface of the medium density board obtained in Example 1; (b) Microscopic image of the surface of the medium density board obtained in Example 2; (c) Microscopic image of the surface of the medium density board obtained in Example 3; (d) Microscopic image of the surface of the medium density board obtained in Example 4; (e) Microscopic image of the surface of the medium density board obtained in Example 5. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0032] Example 1

[0033] A method for preparing medium-density fiberboard based on discarded mushroom sticks comprises the following steps:

[0034] (1) The discarded mushroom sticks are crushed by a machine to crack the mushroom sticks and facilitate water penetration;

[0035] (2) spraying the discarded mushroom sticks after rolling in step (1) with 0.5% w / v borax solution, the spraying amount being 50% of the dry weight of the mushroom sticks, and allowing to swell for 4 hours;

[0036] (3) steam explosion treatment of the discarded mushroom sticks after being fully swollen in step (2) at a steam pressure of 1 MPa for 300 seconds;

[0037] (4) grinding the mushroom sticks after steam explosion in step (3) using a 0.2 mm disc grinder to disperse the fibers in the mushroom sticks, and adding an appropriate amount of water to cool and dilute the fibers after grinding to control the fiber concentration to 15-25%;

[0038] (5) drying the dispersed mushroom stick fibers in air or hot air so that the moisture content of the dried mushroom stick fibers is 15 to 30%;

[0039] (6) dissolving the phenolic adhesive in ethanol and then mixing it with the dried mushroom stick fibers at a solid-liquid ratio of 1:2.5, with the amount of phenolic adhesive being 2.5% of the mass of the dried mushroom sticks;

[0040] (7) exposing the mixture from step (6) to air to allow some of the ethanol to evaporate;

[0041] (8) Then, the raw materials of step (7) were placed in a hot press, the pressure was controlled at 20 MPa, the temperature was controlled at 150° C., and the hot pressing time was 20 minutes to prepare a mushroom stick-based medium density fiberboard.

[0042] Example 2

[0043] A method for preparing medium-density fiberboard based on discarded mushroom sticks comprises the following steps:

[0044] (1) The discarded mushroom sticks are crushed by a machine to crack the mushroom sticks and facilitate water penetration;

[0045] (2) spraying the discarded mushroom sticks after rolling in step (1) with a 1% w / v borax solution, the spraying amount being 100% of the dry weight of the mushroom sticks, and allowing them to swell for 8 hours;

[0046] (3) The discarded mushroom sticks after being fully swollen in step (2) were subjected to steam explosion treatment at a steam pressure of 1 MPa and a holding time of 300 s;

[0047] (4) grinding the mushroom sticks after steam explosion in step (3) using a 0.2 mm disc grinder to disperse the fibers in the mushroom sticks, and adding an appropriate amount of water to cool and dilute the fibers after grinding to control the fiber concentration to 15-25%;

[0048] (5) drying the dispersed mushroom stick fibers in air or hot air so that the moisture content of the dried mushroom stick fibers is 15 to 30%;

[0049] (6) dissolving the phenolic adhesive in ethanol and then mixing it with the dried mushroom stick fibers at a solid-liquid ratio of 1:2.5, with the amount of phenolic adhesive being 2.5% of the mass of the dried mushroom sticks;

[0050] (7) exposing the mixture from step (6) to air to allow some of the ethanol to evaporate;

[0051] (8) Then, the raw materials of step (7) were placed in a hot press, the pressure was controlled at 20 MPa, the temperature was controlled at 170° C., and the hot pressing time was 10 minutes to prepare a mushroom stick-based medium density fiberboard.

[0052] Example 3

[0053] A method for preparing medium-density fiberboard based on discarded mushroom sticks comprises the following steps:

[0054] (1) The discarded mushroom sticks are crushed by a machine to crack the mushroom sticks and facilitate water penetration;

[0055] (2) spraying the discarded mushroom sticks after rolling in step (1) with a 1% w / v borax solution at a spraying amount of 150% of the dry weight of the mushroom sticks and allowing them to swell for 12 hours;

[0056] (3) The discarded mushroom sticks after being fully swollen in step (2) were subjected to steam explosion treatment at a steam pressure of 1 MPa and a holding time of 300 s;

[0057] (4) grinding the mushroom sticks after steam explosion in step (3) using a 0.2 mm disc grinder to disperse the fibers in the mushroom sticks, and adding an appropriate amount of water to cool and dilute the fibers after grinding to control the fiber concentration to 15-25%;

[0058] (5) drying the dispersed mushroom stick fibers in air or hot air so that the moisture content of the dried mushroom stick fibers is 15 to 30%;

[0059] (6) dissolving the phenolic adhesive in ethanol and then mixing it with the dried mushroom stick fibers at a solid-liquid ratio of 1:2.5. The amount of phenolic adhesive used is 5% of the mass of the dried mushroom sticks.

[0060] (7) exposing the mixture from step (6) to air to allow some of the ethanol to evaporate;

[0061] (8) Then, the raw materials of step (7) were placed in a hot press, the pressure was controlled at 20 MPa, the temperature was controlled at 170° C., and the hot pressing time was 20 minutes to prepare a mushroom stick-based medium density fiberboard.

[0062] Example 4

[0063] A method for preparing medium-density fiberboard based on discarded mushroom sticks comprises the following steps:

[0064] (1) The discarded mushroom sticks are crushed by a machine to crack the mushroom sticks and facilitate water penetration;

[0065] (2) spraying the discarded mushroom sticks after rolling in step (1) with a 1% w / v borax solution at a spraying amount of 200% of the dry weight of the mushroom sticks and allowing them to swell for 8 hours;

[0066] (3) The discarded mushroom sticks after being fully swollen in step (2) were subjected to steam explosion treatment at a steam pressure of 1 MPa and a holding time of 300 s;

[0067] (4) grinding the mushroom sticks after steam explosion in step (3) using a 0.2 mm disc grinder to disperse the fibers in the mushroom sticks, and adding an appropriate amount of water to cool and dilute the fibers after grinding to control the fiber concentration to 15-25%;

[0068] (5) drying the dispersed mushroom stick fibers in air or hot air so that the moisture content of the dried mushroom stick fibers is 15 to 30%;

[0069] (6) dissolving the phenolic adhesive in ethanol and then mixing it with the dried mushroom stick fibers at a solid-liquid ratio of 1:2.5. The amount of phenolic adhesive used is 5% of the mass of the dried mushroom sticks.

[0070] (7) exposing the mixture from step (6) to air to allow some of the ethanol to evaporate;

[0071] (8) Then, the raw materials of step (7) were placed in a hot press, the pressure was controlled at 20 MPa, the temperature was controlled at 190° C., and the hot pressing time was 10 minutes to prepare a mushroom stick-based medium density fiberboard.

[0072] Example 5

[0073] A method for preparing medium-density fiberboard based on discarded mushroom sticks comprises the following steps:

[0074] (1) The discarded mushroom sticks are crushed by a machine to crack the mushroom sticks and facilitate water penetration;

[0075] (2) spraying the discarded mushroom sticks after rolling in step (1) with a 0.5% w / v borax solution at a spraying amount of 150% of the dry weight of the mushroom sticks and allowing them to swell for 8 hours;

[0076] (3) The discarded mushroom sticks after being fully swollen in step (2) were subjected to steam explosion treatment at a steam pressure of 1 MPa and a holding time of 300 s;

[0077] (4) grinding the mushroom sticks after steam explosion in step (3) using a 0.2 mm disc grinder to disperse the fibers in the mushroom sticks, and adding an appropriate amount of water to cool and dilute the fibers after grinding to control the fiber concentration to 15-25%;

[0078] (5) drying the dispersed mushroom stick fibers in air or hot air so that the moisture content of the dried mushroom stick fibers is 15 to 30%;

[0079] (6) Without using an adhesive, the raw materials of step (5) were directly placed in a hot press, the pressure was controlled at 20 MPa, the temperature was controlled at 190, and the hot pressing time was 30 minutes to prepare a mushroom stick-based medium density fiberboard.

[0080] Control Example

[0081] A method for preparing medium-density fiberboard based on discarded mushroom sticks comprises the following steps:

[0082] (1) The discarded mushroom sticks are crushed by a machine to crack the mushroom sticks and facilitate water penetration;

[0083] (2) Spraying the discarded mushroom sticks after rolling in step (1) with 200% clean water and letting them swell for 8 hours;

[0084] (3) The discarded mushroom sticks after being fully swollen in step (2) were subjected to steam explosion treatment at a steam pressure of 1 MPa and a holding time of 300 s;

[0085] (4) grinding the mushroom sticks after steam explosion in step (3) using a 0.2 mm disc grinder to disperse the fibers in the mushroom sticks, and adding an appropriate amount of water to cool and dilute the fibers after grinding to control the fiber concentration to 15-25%;

[0086] (5) drying the dispersed mushroom stick fibers in air or hot air so that the moisture content of the dried mushroom stick fibers is 15 to 30%;

[0087] (6) Without using an adhesive, the raw materials of step (5) were directly placed in a hot press, the pressure was controlled at 20 MPa, the temperature was controlled at 190° C., and the hot pressing time was 30 minutes to prepare a mushroom stick-based medium density fiberboard.

[0088] The mechanical properties and water resistance of the mushroom stick-based fiber composite board prepared by the present invention were tested, and the test results are as follows:

[0089] The internal bond strength (IBS) and static bending strength (SBS) of the mushroom stick-based medium density fiberboard were evaluated according to the criteria specified in the GB / T17657-2013 standard. The mushroom stick-based medium density fiberboard prepared in the example was tested using a Shimadzu universal tensile tester (Shimadzu AGS-X, Shimadzu, Japan).

[0090] The thickness expansion of MDF was determined according to GB / T 17657-2013 standard, and the water absorption rate TS of the sample within 24 hours was determined.

[0091]

[0092] Embodiment 5 and reference examples all do not add phenolic resin, can find out from test result, two samples all possess certain mechanical property under dry condition, but 24H thickness expansion ratio is higher, and the sample of reference examples is easy to be smashed in 24h thickness expansion ratio test, and its intensity on the surface is very poor under wet condition.Wherein the internal bonding strength (2.27MPa) of embodiment 5 can reach or even exceed the sample that part adds adhesive under dry condition, proves that the bonding force of mushroom stick lignin self can be by fiber adhesion.Among embodiment 3, the consumption of phenolic adhesive is 5%, and the internal bonding strength of the medium density board prepared reaches 5.15MPa.

[0093] Li Jian et al. (Li, J., Li, S. Pyrolysis of medium density fiberboard impregnated with phenol-formaldehyde resin [J]. Journal of Wood Science, 2006, 52 (4): 331-336.) added 40% by mass of phenol-formaldehyde resin to medium density fiberboard, and Park et al. (Park BD, Riedl B, Hsu EW, et al. Effects of weight average molecular mass of phenol-formaldehyde adhesives on medium density fiberboard performance [J]. Holz als Roh- und Werkstoff, 1998, 56 (3): 155-161.) added 35% by mass of phenol-formaldehyde resin to prepare medium density fiberboard, and the internal bonding strength was between 0.15-0.36 MPa, and the static bending strength was between 9.8-48.3 MPa. The present invention can achieve the mechanical properties of the superior product specified in GB / T 11718-1999 for medium density boards by using phenolic resin with a lower mass fraction.

[0094] In addition, it is stated that the specific implementation manner is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above with a preferred embodiment, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical content disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing medium density fiberboard based on discarded mushroom sticks, characterized in that: The steps include: (1) The discarded mushroom sticks are crushed by a machine to crack the mushroom sticks and facilitate water penetration; (2) preparing a 0.5-1% w / v borax solution; (3) spraying the solution prepared in step (2) onto the discarded mushroom sticks after rolling in step (1) at a ratio of 50 to 200% of the dry weight of the mushroom sticks, and stirring appropriately to ensure that the mushroom sticks are evenly and fully moistened; (4) steam explosion treatment of the discarded mushroom sticks after being fully swollen in step (3); (5) grinding the mushroom sticks after steam explosion in step (4) to disperse the fibers in the mushroom sticks, and adding an appropriate amount of water to cool and dilute the fibers after grinding; (6) drying the dispersed mushroom stick fibers in air or with hot air; (7) dissolving a phenolic adhesive in ethanol and then mixing it with the dried mushroom stick fibers to obtain a mixture, wherein the amount of the phenolic adhesive is 0 to 5% of the mass of the dried mushroom sticks; (8) exposing the mixture of step (7) to air to allow some of the ethanol to evaporate; (9) Then, the raw materials of step (8) are placed in a hot press, the pressure is controlled at 20 MPa, the temperature is controlled at 150-190° C., and the hot pressing time is 10-30 minutes to prepare a mushroom stick-based medium density fiberboard.

2. The method for preparing medium density fiberboard based on discarded mushroom sticks according to claim 1, characterized in that: In step 3, the time for soaking the discarded mushroom sticks in water is greater than or equal to 8 hours.

3. The method for preparing medium density fiberboard based on discarded mushroom sticks according to claim 1, characterized in that: In step 4, the steam pressure for steam explosion treatment of discarded mushroom sticks is 1 MPa, and the pressure holding time is 300 s.

4. The method for preparing medium density fiberboard based on discarded mushroom sticks according to claim 1, characterized in that: The gap of the disc grinding in step 5 is 0.2 mm.

5. The method for preparing medium density fiberboard based on discarded mushroom sticks according to claim 1, characterized in that: In the step 5, the fiber concentration after dilution is controlled at 15-25%.

6. The method for preparing medium density fiberboard based on discarded mushroom sticks according to claim 1, characterized in that: The moisture content of the mushroom stick fibers after drying in step 6 is 15-30%.

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