Preparation technology of formaldehyde-free particleboard by mechanical activation and microwave synergistic method

Abstract

The present invention discloses a process for preparing formaldehyde-free particleboard by mechanical activation and microwave synergistic method, comprising the following steps: (1) mixing particleboard powder by mechanical activation method to obtain particleboard powder raw material; (2) spraying antibacterial liquid evenly on the particleboard powder raw material to obtain antibacterial pretreated particleboard powder raw material; (3) mixing formaldehyde-free adhesive and water evenly to obtain diluted formaldehyde-free adhesive; (4) spraying the diluted formaldehyde-free adhesive on the antibacterial pretreated particleboard powder raw material to obtain adhesive-mixed particleboard; (5) paving the adhesive-mixed particleboard to obtain a slab; (6) feeding the slab into the cavity of a microwave device and heating it by microwave preheating to obtain a preheated slab; (7) pressing the preheated slab into a plate to obtain formaldehyde-free particleboard. The particleboard product prepared by the present invention has excellent mechanical properties and water absorption properties, and its formaldehyde emission reaches the new national standard ENF level, indicating that the particleboard product of the present invention has extremely high environmental performance.

Description

Technical field

[0001] The invention belongs to the technical field of particleboard preparation, and particularly relates to a process for preparing formaldehyde-free particleboard by a mechanical activation and microwave synergistic method. [Background Technology]

[0002] At present, urea-formaldehyde resin glue is the most widely used adhesive in particleboard production. This type of adhesive uses formaldehyde as a synthetic raw material. During the use of the finished product, there is a certain amount of formaldehyde released, which is harmful to people's health. Formaldehyde-free particleboard is made by chipping and shaving wood and other raw materials into particles of a certain specification. During the gluing process of the particles, formaldehyde-free glue is used for hot pressing. However, the wood itself contains extremely small amounts of naturally inherent free formaldehyde, which will release extremely small amounts of formaldehyde. The formaldehyde emission standard for formaldehyde-free particleboard is ≤0.5mg / 100g according to the perforation extraction method and ≤0.03mg / m 3 The new national standard GB / T 39600-2021 "Classification of formaldehyde emission of wood-based panels and their products" to be implemented on October 1, 2021, divides the formaldehyde emission limit into E1 level (≤0.124mg / m 3 ), E0 level (≤0.050mg / m 3 ), ENF level (≤0.025mg / m 3 ), formaldehyde-free particleboard belongs to ENF grade. Therefore, the research and development of formaldehyde-free particleboard is an inevitable trend of market demand.

[0003] The primary adhesives used in formaldehyde-free particleboard production in my country are isocyanate and biomass adhesives, with isocyanate adhesives being the most common. While using formaldehyde-free adhesives to produce particleboard completely eliminates the formaldehyde emission issue compared to traditional urea-formaldehyde resins, their widespread adoption still requires addressing two key issues: high production costs and significant price fluctuations, particularly with isocyanates, which are significantly more expensive than urea-formaldehyde resins. Second, the production process is immature. For example, using only isocyanates to produce particleboard can lead to issues such as sticking to steel strips, poor initial adhesion, poor mat formation, slab clogging, and low production capacity. The largest components of particleboard costs are wood raw material and adhesive costs. Reducing wood raw material costs primarily involves expanding raw material utilization and lowering raw material quality requirements, but lowering raw material quality can significantly impact product quality.

[0004] Therefore, how to develop a new formaldehyde-free particleboard production process that can reduce production costs while ensuring product performance and environmental protection requirements is a major challenge facing the particleboard industry.

[0005] (1) Use mechanical activation instead of traditional mixing method

[0006] Mechanical activation is an emerging cutting-edge technology. It involves the process of modifying the crystal structure and physicochemical properties of solid materials under mechanical forces such as friction, collision, impact, and shear, converting some of the mechanical energy into internal energy, thereby increasing the chemical activity of the solid. It falls within the realm of mechanochemistry. In recent years, mechanochemistry has achieved significant development and is widely used in the preparation of ultrafine and nanopowders, nanocomposites, dispersion-strengthened alloy structures, metal refining, mineral and waste treatment, and polymer synthesis.

[0007] The introduction of mechanical activation technology into the production of formaldehyde-free particleboard has not yet been reported. Using a mechanical ball mill to mix the particleboard raw materials effectively addresses issues such as uneven particle size, uneven mixing, and partial agglomeration. Furthermore, the mixed materials are continuously subjected to the high-energy impact of zirconium dioxide balls, resulting in a ball-powder-ball-ball-ball-powder-tank wall collision, which repeatedly causes fractures and cold welding, ultimately forming fine, uniformly mixed powder particles. The resulting particleboard product exhibits excellent mechanical properties and deformation resistance.

[0008] (2) Develop new formaldehyde-free adhesives

[0009] Currently, the industrial production of formaldehyde-free particleboard in China generally uses two main adhesive types: isocyanate (PMDI) and modified biomass adhesives. PMDI, as a particleboard adhesive, possesses strong bonding properties, capable of bonding wood particles with high moisture content, without releasing harmful gases such as formaldehyde. However, PMDI also has drawbacks in production and application. For example, its high reactivity makes it susceptible to reactions with metals, resulting in "sticking to steel strips." PMDI also has little initial tack, requiring the use of tackifiers and release agents, significantly increasing costs and operational complexity. Subsequent processing of PMDI-produced particleboard can also lead to edge chipping and tool waste. More importantly, if the press is not properly isolated and protected, the toxic volatile substances released by PMDI during the hot pressing process pose a health risk to frontline workers far greater than formaldehyde. Modified biomass adhesives that have entered the industrialization stage include lignin, soy protein-based adhesives, and starch-based adhesives. While they have achieved some success in laboratory and industrial applications, large-scale industrial application requires further improvement due to their high cost and performance limitations.

[0010] (3) Using microwave heating instead of traditional heating methods

[0011] During the hot pressing process of particleboard, large-scale microwave heating equipment is used to replace the traditional heating method. This method has not been reported in the production of formaldehyde-free particleboard.

[0012] Microwaves are a type of electromagnetic wave with a wavelength of 1m-0.1cm and a frequency of 300MHz to 300GHz, falling between radio waves and infrared in the electromagnetic spectrum. Microwave heating differs from traditional heating methods such as thermal radiation and conduction; it involves microwave interaction at the molecular level. Microwave heating is characterized by instant on / off, overall heating, penetrating heating, and rapid heating rates. Microwave heating is closely related to the material's inherent electrical conductivity, dielectric constant, and magnetic permeability. Microwave applications primarily utilize a microwave generator to convert electrical energy into electromagnetic energy. Under certain conditions, electromagnetic energy acts on an absorbing medium and is converted into heat, a phenomenon known as the microwave heating effect. The primary mechanism is the interaction and absorption of microwaves with molecules, generating heat. Compared with infrared heating, high-frequency heating and other conductive heating methods, the application characteristics of microwaves are as follows: First, it can penetrate deep into the interior of objects, is endogenous heat, does not rely on heat conduction, can heat instantly, is fast and energy-saving, and has high heat conversion efficiency due to its short wavelength; second, it is easy to concentrate and protect, which can achieve cleanliness and hygiene without polluting the environment; third, it is easy to combine with other technologies, which can release effects greater than the superposition, giving rise to many "microwave + N" coupling technologies, and thus generating interdisciplinary disciplines related to microwaves.

[0013] The conventional heating method commonly used in the hot-pressing process for particleboard production suffers from slow heat conduction, which affects pressure transmission during the hot-pressing process. This results in low density in the center of the formed particleboard, high density at the edges, and uneven density overall. However, microwave heating uses microwaves emitted by a microwave head to rapidly heat the moisture within the slab, thereby raising the slab temperature. The binder and wood chips added to particleboard have a certain ability to absorb microwaves, allowing them to penetrate and heat the entire board, preventing ineffective heating of the intermediate layers. Combining microwave heating with pressing produces homogeneous particleboard. [Summary of the invention]

[0014] The present invention provides a process for preparing formaldehyde-free particleboard by using a mechanical activation and microwave synergistic method, so as to solve the technical problem of how to prepare high-performance particleboard.

[0015] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0016] A process for preparing formaldehyde-free particleboard by mechanical activation and microwave synergy comprises the following steps:

[0017] (1) The wood shavings powder is mixed by a mechanical activation method, and the wood shavings powder is continuously subjected to high-energy impact of zirconium dioxide balls, resulting in collisions between zirconium ball-powder-zirconium ball-zirconium ball-powder-tank wall, thereby obtaining a wood shavings powder raw material that is evenly mixed and well dispersed;

[0018] (2) spraying the antibacterial liquid evenly on the wood shavings powder raw material obtained in step (1) to obtain the antibacterial pretreated wood shavings powder raw material;

[0019] (3) uniformly mixing the formaldehyde-free adhesive and water to prepare a diluted formaldehyde-free adhesive;

[0020] (4) spraying the diluted formaldehyde-free adhesive obtained in step (3) onto the antibacterial pretreated wood shavings powder raw material obtained in step (2) using an atomizing glue sprayer and mixing the mixture evenly to obtain glue-mixed wood shavings;

[0021] (5) paving the rubber-mixed wood shavings obtained in step (4) to obtain a slab;

[0022] (6) transporting the slab obtained in step (5) into the cavity of a microwave device by means of a conveyor belt, heating the slab by microwave preheating, and obtaining a preheated slab;

[0023] (7) The preheated slab obtained in step (6) is pressed into a plate to obtain a formaldehyde-free particleboard.

[0024] The present invention uses mechanical activation, an emerging cross-ball milling technology, to mix particleboard raw materials. The powder mixture is continuously subjected to high-energy impacts of zirconium dioxide balls, resulting in collisions of zirconium ball-powder-zirconium ball-zirconium ball-powder-tank wall, ultimately forming fine, evenly mixed, and well-dispersed raw materials. The prepared particleboard products have excellent mechanical properties and deformation resistance. Microwave heating is used in the hot pressing section to replace traditional heating methods. Microwaves are used for penetrating overall heating to avoid ineffective heating of the middle layer. Combining microwave heating and pressing can produce homogeneous particleboard. By independently developing a new type of formaldehyde-free adhesive, the formaldehyde emission of the produced particleboard meets the new national standard ENF level that will soon be implemented. No industrial "three wastes" are generated during the entire production and reaction process, achieving a win-win situation in economic benefits and environmental protection.

[0025] Furthermore, the method for preparing the antibacterial liquid in step (2) comprises the following steps:

[0026] a. In parts by mass, 42 parts of carbonamide, 6 parts of primary oleic acid, 10 parts of ethyl vanillin, 3 parts of silane coupling agent KH570, 1 part of hydrochloric acid, and 0.6 parts of diisopropyl peroxydicarbonate were mixed, and the mixture was heated and stirred in a microwave to prepare a first mixture;

[0027] b. Add 5 parts of diatomaceous earth powder to the first mixture prepared in step a, and treat under stirring to prepare a second mixture;

[0028] c. Add 1.6 parts of triethanolamine and 300 parts of water to the second mixture prepared in step b, heat and stir, and prepare an antibacterial solution.

[0029] Furthermore, in step a, the mixture was stirred for 2 h at a microwave power of 300 W, a temperature of 56° C., and a rotation speed of 200 r / min to obtain a first mixture.

[0030] Furthermore, in step b, the mixture is stirred at a rotation speed of 300 r / min for 1 hour to obtain a second mixture.

[0031] Furthermore, in step c, the mixture is heated to 82° C. and stirred at a rotation speed of 400 r / min for 0.8 h to prepare an antibacterial liquid.

[0032] Furthermore, the formaldehyde-free adhesive in step (3) is evenly mixed with water in a weight ratio of 1:1.6-2.3.

[0033] Furthermore, the adhesive in step (4) is 7%-8% by weight of the total wood shavings powder in step (1).

[0034] Furthermore, the slab thickness in step (5) is 18 mm and the slab size is 300 mm×300 mm.

[0035] Furthermore, in step (6), microwave heating is performed with a heating power density of 12-16 W / g·m 3 .

[0036] Furthermore, in step (6), the conveyor belt speed is controlled to be 0.25-0.32 m / s.

[0037] The present invention has the following beneficial effects:

[0038] (1) The mildew time of the formaldehyde-free particleboard product prepared by the present invention is ≥42h, and the mildew index (grade) is 0, which shows that the particleboard product has excellent antibacterial and mildew-proof properties. This is because: in the preparation of the antibacterial liquid by the present invention, carbonamide, primary oleic acid, and ethyl vanillin are mixed, and under the joint action of silane coupling agent KH570, hydrochloric acid, and diisopropyl peroxydicarbonate, and stirred at a certain microwave power, temperature, and speed, an organic combination is achieved to prepare a first mixture; then, diatomaceous earth powder with strong adsorption performance is added to the first mixture prepared above, and the mixture is stirred for a certain time to prepare a second mixture; then, triethanolamine is added to the second mixture prepared, which further promotes the antibacterial and mildew-proof properties of the particleboard product, prolongs the mildew time, and improves the mildew index.

[0039] (2) The product indicators of the formaldehyde-free particleboard prepared by the present invention are: static bending strength ≥29.8MPa, internal bonding strength ≥0.85MPa, bending elastic modulus ≥4549MPa, 24h water absorption thickness expansion rate ≤7.11%, formaldehyde release <0.025mg / m 3, indicating that the particleboard product prepared by the present invention has excellent mechanical properties and water absorption properties, and the formaldehyde emission reaches the ENF level of the new national standard GB / T39600-2021 "Classification of Formaldehyde Emission of Artificial Boards and Their Products", indicating that the particleboard product of the present invention has extremely high environmental performance. [Specific implementation method]

[0040] In order to facilitate a better understanding of the present invention, the following examples are provided for illustration. These examples belong to the protection scope of the present invention, but do not limit the protection scope of the present invention.

[0041] In an embodiment, the process for preparing formaldehyde-free particleboard by the mechanical activation and microwave synergistic method comprises the following steps:

[0042] (1) The wood shavings powder is mixed by mechanical activation, and the wood shavings powder is continuously subjected to high-energy impact of zirconium dioxide balls, resulting in collisions between zirconium ball-powder-zirconium ball-zirconium ball-powder-tank wall, ultimately forming a fine, evenly mixed, and well-dispersed wood shavings powder raw material;

[0043] (2) spraying the antibacterial liquid evenly on the wood shavings powder raw material obtained in step (1) to obtain the antibacterial pretreated wood shavings powder raw material;

[0044] The preparation method of the antibacterial liquid comprises the following steps:

[0045] a. In parts by mass, 42 parts of carbonamide, 6 parts of primary oleic acid, 10 parts of ethyl vanillin, 3 parts of silane coupling agent KH570, 1 part of hydrochloric acid, and 0.6 parts of diisopropyl peroxydicarbonate were mixed, and the mixture was stirred at a microwave power of 300 W, a temperature of 56° C., and a speed of 200 r / min for 2 h to obtain a first mixture;

[0046] b. Add 5 parts of diatomaceous earth powder to the first mixture prepared in step a, and stir at a speed of 300 r / min for 1 hour to prepare a second mixture;

[0047] c. Add 1.6 parts of triethanolamine and 300 parts of water to the second mixture prepared in step b, heat to 82° C., and stir at a speed of 400 r / min for 0.8 h to prepare an antibacterial solution;

[0048] (3) uniformly mixing the formaldehyde-free adhesive and water in a weight ratio of 1:1.6-2.3 to prepare a diluted formaldehyde-free adhesive;

[0049] The preparation method of the formaldehyde-free adhesive comprises the following steps:

[0050] Step 1: preparing modified talc, comprising the following steps:

[0051] 1) Grind clean talc and sieve to obtain talc powder with a mesh size of 1600;

[0052] 2) adding sodium N-(2-aminoethyl) aminoethane sulfonate and polyethylene glycol fatty acid ester to the talc prepared in step 1), stirring and modifying the mixture at a microwave power of 350 W, a temperature of 67 ° C., and a speed of 300 r / min for 2.6 h to obtain a mixture a, wherein the weight ratio of the talc, sodium N-(2-aminoethyl) aminoethane sulfonate, and polyethylene glycol fatty acid ester is 100:3:1.4;

[0053] 3) adding amino polydimethylsiloxane and polymaleic acid-chitosan to the mixture a prepared in step 2), and stirring for 3.6 hours at a microwave power of 260 W, a temperature of 85° C., and a speed of 400 r / min to prepare a mixture b, wherein the weight ratio of the talc, amino polydimethylsiloxane, and polymaleic acid-chitosan is 85:1.8:1;

[0054] 4) drying the mixture b obtained in step 3) at 68° C. to a moisture content of 1%, then grinding and sieving to obtain a modified talc powder of 1600 mesh;

[0055] Step 2: In parts by mass, 50 parts of the modified talc prepared in step 4), 112 parts of polymerized methylene diphenyl diisocyanate, 5 parts of a wetting agent, 1.6 parts of a penetrant, and 0.9 parts of a surfactant were mixed, the temperature was adjusted to 48° C., and the mixture was stirred at a speed of 400 r / min for 5 minutes to obtain a mixture c, wherein the wetting agent is composed of a polyol, ethyl valerate, and water in a mass ratio of 5:1.6:7, and the polyol is pentaerythritol;

[0056] The penetrant is composed of sodium α-olefin sulfonate and sodium secondary alkyl sulfate in a mass ratio of 3:5;

[0057] The surfactant is composed of fatty alcohol polyoxyethylene ether ammonium sulfate and sodium lauryl sulfate in a mass ratio of 3.5:1.6;

[0058] Step 3: Add 2.5 parts of release agent to the mixture c prepared in step 2, adjust the temperature to 56°C, and mix under the condition of ultrasonic power of 3W / cm 2 , stirring at a speed of 250 r / min for 4 minutes to prepare a formaldehyde-free adhesive, wherein the release agent is composed of polyethylene wax and methyl silicone oil in a mass ratio of 2:3;

[0059] (4) spraying the diluted formaldehyde-free adhesive prepared in step (3) onto the antibacterial pretreated wood shavings powder prepared in step (2) using an atomizing glue sprayer and mixing the mixture evenly to prepare glue-mixed wood shavings, wherein the adhesive is 7% to 8% by weight of the total wood shavings powder in step (1);

[0060] (5) paving the rubber-mixed wood shavings obtained in step (4) to obtain a slab, wherein the slab has a thickness of 18 mm and a surface size of 300 mm × 300 mm;

[0061] (6) The slab prepared in step (5) is transported into the cavity of a microwave device by a conveyor belt and heated by microwaves at a heating power density of 12-16 W / g·m 3 , controlling the conveyor belt speed to be 0.25-0.32 m / s, and obtaining the preheated slab through microwave preheating;

[0062] (7) The preheated slab obtained in step (6) is pressed into a plate to obtain a formaldehyde-free particleboard.

[0063] The following is explained with more specific examples.

[0064] Example 1

[0065] A process for preparing formaldehyde-free particleboard by mechanical activation and microwave synergy comprises the following steps:

[0066] (1) The wood shavings powder is mixed by mechanical activation, and the wood shavings powder is continuously subjected to high-energy impact of zirconium dioxide balls, resulting in collisions between zirconium ball-powder-zirconium ball-zirconium ball-powder-tank wall, ultimately forming a fine, evenly mixed, and well-dispersed wood shavings powder raw material;

[0067] (2) spraying the antibacterial liquid evenly on the wood shavings powder raw material obtained in step (1) to obtain the antibacterial pretreated wood shavings powder raw material;

[0068] The preparation method of the antibacterial liquid comprises the following steps:

[0069] a. In parts by mass, 42 parts of carbonamide, 6 parts of primary oleic acid, 10 parts of ethyl vanillin, 3 parts of silane coupling agent KH570, 1 part of hydrochloric acid, and 0.6 parts of diisopropyl peroxydicarbonate were mixed, and the mixture was stirred at a microwave power of 300 W, a temperature of 56° C., and a speed of 200 r / min for 2 h to obtain a first mixture;

[0070] b. Add 5 parts of diatomaceous earth powder to the first mixture prepared in step a, and stir at a speed of 300 r / min for 1 hour to prepare a second mixture;

[0071] c. Add 1.6 parts of triethanolamine and 300 parts of water to the second mixture prepared in step b, heat to 82° C., and stir at a speed of 400 r / min for 0.8 h to prepare an antibacterial solution;

[0072] (3) uniformly mixing the formaldehyde-free adhesive and water in a weight ratio of 1:1.6 to prepare a diluted formaldehyde-free adhesive;

[0073] The preparation method of the formaldehyde-free adhesive comprises the following steps:

[0074] Step 1: preparing modified talc, comprising the following steps:

[0075] 1) Grind clean talc and sieve to obtain talc powder with a mesh size of 1600;

[0076] 2) adding sodium N-(2-aminoethyl) aminoethane sulfonate and polyethylene glycol fatty acid ester to the talc prepared in step 1), stirring and modifying the mixture at a microwave power of 350 W, a temperature of 67 ° C., and a speed of 300 r / min for 2.6 h to obtain a mixture a, wherein the weight ratio of the talc, sodium N-(2-aminoethyl) aminoethane sulfonate, and polyethylene glycol fatty acid ester is 100:3:1.4;

[0077] 3) adding amino polydimethylsiloxane and polymaleic acid-chitosan to the mixture a prepared in step 2), and stirring for 3.6 hours at a microwave power of 260 W, a temperature of 85° C., and a speed of 400 r / min to prepare a mixture b, wherein the weight ratio of the talc, amino polydimethylsiloxane, and polymaleic acid-chitosan is 85:1.8:1;

[0078] 4) drying the mixture b obtained in step 3) at 68° C. to a moisture content of 1%, then grinding and sieving to obtain a modified talc powder of 1600 mesh;

[0079] Step 2: In parts by mass, 50 parts of the modified talc prepared in step 4), 112 parts of polymerized methylene diphenyl diisocyanate, 5 parts of a wetting agent, 1.6 parts of a penetrant, and 0.9 parts of a surfactant were mixed, the temperature was adjusted to 48° C., and the mixture was stirred at a speed of 400 r / min for 5 minutes to obtain a mixture c, wherein the wetting agent is composed of a polyol, ethyl valerate, and water in a mass ratio of 5:1.6:7, and the polyol is pentaerythritol;

[0080] The penetrant is composed of sodium α-olefin sulfonate and sodium secondary alkyl sulfate in a mass ratio of 3:5;

[0081] The surfactant is composed of fatty alcohol polyoxyethylene ether ammonium sulfate and sodium lauryl sulfate in a mass ratio of 3.5:1.6;

[0082] Step 3: Add 2.5 parts of release agent to the mixture c prepared in step 2, adjust the temperature to 56°C, and mix under the condition of ultrasonic power of 3W / cm 2 , stirring at a speed of 250 r / min for 4 minutes to prepare a formaldehyde-free adhesive, wherein the release agent is composed of polyethylene wax and methyl silicone oil in a mass ratio of 2:3;

[0083] (4) spraying the diluted formaldehyde-free adhesive prepared in step (3) onto the antibacterial pretreated wood shavings powder prepared in step (2) using an atomizing glue sprayer and mixing the mixture evenly to prepare mixed wood shavings, wherein the adhesive is 7.1% by weight of the total wood shavings powder in step (1);

[0084] (5) paving the rubber-mixed wood shavings obtained in step (4) to obtain a slab, wherein the slab has a thickness of 18 mm and a surface size of 300 mm × 300 mm;

[0085] (6) The slab prepared in step (5) is transported into the cavity of a microwave device by a conveyor belt and heated by microwaves at a heating power density of 13 W / g·m 3 , controlling the conveyor belt speed to 0.26 m / s, and preparing the preheated slab through microwave preheating;

[0086] (7) The preheated slab obtained in step (6) is pressed into a plate to obtain a formaldehyde-free particleboard.

[0087] Example 2

[0088] A process for preparing formaldehyde-free particleboard by mechanical activation and microwave synergy comprises the following steps:

[0089] (1) The wood shavings powder is mixed by mechanical activation, and the wood shavings powder is continuously subjected to high-energy impact of zirconium dioxide balls, resulting in collisions between zirconium ball-powder-zirconium ball-zirconium ball-powder-tank wall, ultimately forming a fine, evenly mixed, and well-dispersed wood shavings powder raw material;

[0090] (2) spraying the antibacterial liquid evenly on the wood shavings powder raw material obtained in step (1) to obtain the antibacterial pretreated wood shavings powder raw material;

[0091] The preparation method of the antibacterial liquid comprises the following steps:

[0092] a. In parts by mass, 42 parts of carbonamide, 6 parts of primary oleic acid, 10 parts of ethyl vanillin, 3 parts of silane coupling agent KH570, 1 part of hydrochloric acid, and 0.6 parts of diisopropyl peroxydicarbonate were mixed, and the mixture was stirred at a microwave power of 300 W, a temperature of 56° C., and a speed of 200 r / min for 2 h to obtain a first mixture;

[0093] b. Add 5 parts of diatomaceous earth powder to the first mixture prepared in step a, and stir at a speed of 300 r / min for 1 hour to prepare a second mixture;

[0094] c. Add 1.6 parts of triethanolamine and 300 parts of water to the second mixture prepared in step b, heat to 82° C., and stir at a speed of 400 r / min for 0.8 h to prepare an antibacterial solution;

[0095] (3) uniformly mixing the formaldehyde-free adhesive and water in a weight ratio of 1:2.1 to prepare a diluted formaldehyde-free adhesive;

[0096] The preparation method of the formaldehyde-free adhesive comprises the following steps:

[0097] Step 1: preparing modified talc, comprising the following steps:

[0098] 1) Grind clean talc and sieve to obtain 1600 mesh talc powder;

[0099] 2) adding sodium N-(2-aminoethyl) aminoethane sulfonate and polyethylene glycol fatty acid ester to the talc prepared in step 1), stirring and modifying the mixture at a microwave power of 350 W, a temperature of 67 ° C., and a speed of 300 r / min for 2.6 h to obtain a mixture a, wherein the weight ratio of the talc, sodium N-(2-aminoethyl) aminoethane sulfonate, and polyethylene glycol fatty acid ester is 100:3:1.4;

[0100] 3) adding amino polydimethylsiloxane and polymaleic acid-chitosan to the mixture a prepared in step 2), and stirring for 3.6 hours at a microwave power of 260 W, a temperature of 85° C., and a speed of 400 r / min to prepare a mixture b, wherein the weight ratio of the talc, amino polydimethylsiloxane, and polymaleic acid-chitosan is 85:1.8:1;

[0101] 4) drying the mixture b obtained in step 3) at 68° C. to a moisture content of 1%, then grinding and sieving to obtain a modified talc powder of 1600 mesh;

[0102] Step 2: In parts by mass, 50 parts of the modified talc prepared in step 4), 112 parts of polymerized methylene diphenyl diisocyanate, 5 parts of a wetting agent, 1.6 parts of a penetrant, and 0.9 parts of a surfactant were mixed, the temperature was adjusted to 48° C., and the mixture was stirred at a speed of 400 r / min for 5 minutes to obtain a mixture c, wherein the wetting agent is composed of a polyol, ethyl valerate, and water in a mass ratio of 5:1.6:7, and the polyol is pentaerythritol;

[0103] The penetrant is composed of sodium α-olefin sulfonate and sodium secondary alkyl sulfate in a mass ratio of 3:5;

[0104] The surfactant is composed of fatty alcohol polyoxyethylene ether ammonium sulfate and sodium lauryl sulfate in a mass ratio of 3.5:1.6;

[0105] Step 3: Add 2.5 parts of release agent to the mixture c prepared in step 2, adjust the temperature to 56°C, and mix under the condition of ultrasonic power of 3W / cm 2, stirring at a speed of 250 r / min for 4 minutes to prepare a formaldehyde-free adhesive, wherein the release agent is composed of polyethylene wax and methyl silicone oil in a mass ratio of 2:3;

[0106] (4) spraying the diluted formaldehyde-free adhesive prepared in step (3) onto the antibacterial pretreated wood shavings powder prepared in step (2) using an atomizing glue sprayer and mixing the mixture evenly to prepare glue-mixed wood shavings, wherein the adhesive accounts for 7.6% by weight of the total wood shavings powder in step (1);

[0107] (5) paving the rubber-mixed wood shavings obtained in step (4) to obtain a slab, wherein the slab has a thickness of 18 mm and a surface size of 300 mm × 300 mm;

[0108] (6) The slab prepared in step (5) is transported into the cavity of a microwave device by a conveyor belt and heated by microwaves at a heating power density of 15 W / g·m 3 , controlling the conveyor belt speed to 0.28 m / s, and preparing the preheated slab through microwave preheating;

[0109] (7) The preheated slab obtained in step (6) is pressed into a plate to obtain a formaldehyde-free particleboard.

[0110] Example 3

[0111] A process for preparing formaldehyde-free particleboard by mechanical activation and microwave synergy comprises the following steps:

[0112] (1) The wood shavings powder is mixed by mechanical activation, and the wood shavings powder is continuously subjected to high-energy impact of zirconium dioxide balls, resulting in collisions between zirconium ball-powder-zirconium ball-zirconium ball-powder-tank wall, ultimately forming a fine, evenly mixed, and well-dispersed wood shavings powder raw material;

[0113] (2) spraying the antibacterial liquid evenly on the wood shavings powder raw material obtained in step (1) to obtain the antibacterial pretreated wood shavings powder raw material;

[0114] The preparation method of the antibacterial liquid comprises the following steps:

[0115] a. In parts by mass, 42 parts of carbonamide, 6 parts of primary oleic acid, 10 parts of ethyl vanillin, 3 parts of silane coupling agent KH570, 1 part of hydrochloric acid, and 0.6 parts of diisopropyl peroxydicarbonate were mixed, and the mixture was stirred at a microwave power of 300 W, a temperature of 56° C., and a speed of 200 r / min for 2 h to obtain a first mixture;

[0116] b. Add 5 parts of diatomaceous earth powder to the first mixture prepared in step a, and stir at a speed of 300 r / min for 1 hour to prepare a second mixture;

[0117] c. Add 1.6 parts of triethanolamine and 300 parts of water to the second mixture prepared in step b, heat to 82° C., and stir at a speed of 400 r / min for 0.8 h to prepare an antibacterial solution;

[0118] (3) uniformly mixing the formaldehyde-free adhesive and water in a weight ratio of 1:2.3 to prepare a diluted formaldehyde-free adhesive;

[0119] The preparation method of the formaldehyde-free adhesive comprises the following steps:

[0120] Step 1: preparing modified talc, comprising the following steps:

[0121] 1) Grind clean talc and sieve to obtain 1600 mesh talc powder;

[0122] 2) adding sodium N-(2-aminoethyl) aminoethane sulfonate and polyethylene glycol fatty acid ester to the talc prepared in step 1), stirring and modifying the mixture at a microwave power of 350 W, a temperature of 67 ° C., and a speed of 300 r / min for 2.6 h to obtain a mixture a, wherein the weight ratio of the talc, sodium N-(2-aminoethyl) aminoethane sulfonate, and polyethylene glycol fatty acid ester is 100:3:1.4;

[0123] 3) adding amino polydimethylsiloxane and polymaleic acid-chitosan to the mixture a prepared in step 2), and stirring for 3.6 hours at a microwave power of 260 W, a temperature of 85° C., and a speed of 400 r / min to prepare a mixture b, wherein the weight ratio of the talc, amino polydimethylsiloxane, and polymaleic acid-chitosan is 85:1.8:1;

[0124] 4) drying the mixture b obtained in step 3) at 68° C. to a moisture content of 1%, then grinding and sieving to obtain a modified talc powder of 1600 mesh;

[0125] Step 2: In parts by mass, 50 parts of the modified talc prepared in step 4), 112 parts of polymerized methylene diphenyl diisocyanate, 5 parts of a wetting agent, 1.6 parts of a penetrant, and 0.9 parts of a surfactant were mixed, the temperature was adjusted to 48° C., and the mixture was stirred at a speed of 400 r / min for 5 minutes to obtain a mixture c, wherein the wetting agent is composed of a polyol, ethyl valerate, and water in a mass ratio of 5:1.6:7, and the polyol is pentaerythritol;

[0126] The penetrant is composed of sodium α-olefin sulfonate and sodium secondary alkyl sulfate in a mass ratio of 3:5;

[0127] The surfactant is composed of fatty alcohol polyoxyethylene ether ammonium sulfate and sodium lauryl sulfate in a mass ratio of 3.5:1.6;

[0128] Step 3: Add 2.5 parts of release agent to the mixture c prepared in step 2, adjust the temperature to 56°C, and mix under the condition of ultrasonic power of 3W / cm 2 , stirring at a speed of 250 r / min for 4 minutes to prepare a formaldehyde-free adhesive, wherein the release agent is composed of polyethylene wax and methyl silicone oil in a mass ratio of 2:3;

[0129] (4) using an atomizing glue sprayer to spray the diluted formaldehyde-free adhesive prepared in step (3) onto the antibacterial pretreated wood shavings powder raw material prepared in step (2) and mix them evenly to prepare glue-mixed wood shavings, wherein the adhesive is 8% by weight of the total wood shavings powder in step (1);

[0130] (5) paving the rubber-mixed wood shavings obtained in step (4) to obtain a slab, wherein the slab has a thickness of 18 mm and a surface size of 300 mm × 300 mm;

[0131] (6) The slab prepared in step (5) is transported into the cavity of a microwave device by a conveyor belt and heated by microwaves at a heating power density of 16 W / g·m 3 , controlling the conveyor belt speed to 0.31 m / s, and preparing the preheated slab through microwave preheating;

[0132] (7) The preheated slab obtained in step (6) is pressed into a plate to obtain a formaldehyde-free particleboard.

[0133] Experimental example:

[0134] (1) Adhesive performance testing

[0135] The viscosity and free formaldehyde of the formaldehyde-free adhesive prepared in Example 1 were tested, and the test results are shown in the following table.

[0136] experimental group Viscosity (Pa·S) Free formaldehyde (g / kg) Example 3 78.0 0

[0137] The adhesive viscosity test is carried out according to the rotational viscometer method in the national standard GB / T2794-1995, and the test temperature is 25°C.

[0138] It can be seen from the above table that: (1) the viscosity of the formaldehyde-free adhesive prepared in Example 1 reaches 78.0 Pa·S, which can meet the requirements for preparing particleboard. In the preparation process, sodium N-(2-aminoethyl) aminoethane sulfonate and polyethylene glycol fatty acid ester play a synergistic role in the preparation of the adhesive, and synergistically improve the viscosity of the adhesive. This is because: since sodium N-(2-aminoethyl) aminoethane sulfonate and polyethylene glycol fatty acid ester contain amino groups, sulfonic acid groups, long carbon chain fatty acids and other groups, amino groups, sulfonic acid groups, long carbon chain fatty acids and other groups can be introduced on the surface of the modified talc powder, so that after the surface modification of the talc powder, it changes from hydrophilic to lipophilic, thereby improving the dispersibility of the modified talc powder, facilitating the combination with other components of the adhesive preparation, and improving the viscosity of the adhesive.

[0139] (2) The free formaldehyde content of the adhesive prepared in Example 1 is 0 g / kg, indicating that the adhesive of the present invention is formaldehyde-free. The particleboard products prepared using the adhesive are more environmentally friendly and can reduce harm to the human body.

[0140] (2) Performance testing of formaldehyde-free particleboard

[0141] The particleboards prepared in Examples 1-3 were tested for static bending strength, internal bonding strength, elastic modulus, and water absorption thickness expansion rate according to GB / T 17657-2013. The formaldehyde emission was tested according to the provisions of 4.60 in GB / T 17657-2013, and the grades were evaluated according to GB / T 39600-2021 "Classification of Formaldehyde Emission of Artificial Boards and Their Products". The relevant results are shown in the following table.

[0142]

[0143] As can be seen from the table above: From the data of Examples 1-3, it can be seen that the formaldehyde-free particleboard product indicators prepared by the present invention are: static bending strength ≥ 29.8MPa, internal bonding strength ≥ 0.85MPa, bending elastic modulus ≥ 4549MPa, 24h water absorption thickness expansion rate ≤ 7.11%, formaldehyde emission < 0.025mg / m 3 , indicating that the particleboard product prepared by the present invention has excellent mechanical properties and water absorption properties, and the formaldehyde emission reaches the ENF level of the new national standard GB / T 39600-2021 "Classification of Formaldehyde Emission of Artificial Boards and Their Products", indicating that the particleboard product of the present invention has extremely high environmental performance.

[0144] The particleboards prepared in Examples 1-3 were placed in an environment with an air temperature of 15° C. and a relative humidity of 85% or higher, and their mildew time and mildew index were recorded. The results are shown in the following table.

[0145] experimental group Mildew time (h) Mildew index (level) Example 1 42 0 Example 2 59 0 Example 3 51 0

[0146] It can be seen from the above table that the particleboard products prepared in Examples 1-3 of the present invention have a mildew time of ≥42 h and a mildew index (grade) of 0, indicating that the particleboard products have excellent antibacterial and mildew-proof properties. This is because: in the preparation of the antibacterial liquid of the present invention, carbonamide, primary oleic acid, and ethyl vanillin are mixed, and under the joint action of a silane coupling agent KH570, hydrochloric acid, and diisopropyl peroxydicarbonate, and stirred at a certain microwave power, temperature, and speed, an organic combination is achieved to prepare a first mixture; then, diatomaceous earth powder with strong adsorption properties is added to the first mixture prepared above, and the mixture is stirred for a certain time to prepare a second mixture; and then, triethanolamine is added to the second mixture prepared, which further promotes the antibacterial and mildew-proof properties of the particleboard product, prolongs the mildew time, and improves the mildew index.

[0147] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A process for preparing formaldehyde-free particleboard by mechanical activation and microwave synergy, characterized in that: The following steps are involved: (1) The wood shavings powder is mixed by mechanical activation method. The wood shavings powder is continuously subjected to high-energy impact of zirconium dioxide balls, and collisions of zirconium ball-powder-zirconium ball-zirconium ball-powder-tank wall occur, thereby obtaining a wood shavings powder raw material with uniform mixing and good dispersion; (2) spraying the antibacterial liquid evenly on the wood shavings powder raw material obtained in step (1) to obtain the antibacterial pretreated wood shavings powder raw material; (3) Evenly mix the formaldehyde-free adhesive and water to prepare a diluted formaldehyde-free adhesive; (4) spraying the diluted formaldehyde-free adhesive prepared in step (3) onto the antibacterial pretreated wood shavings powder raw material prepared in step (2) using an atomizing glue sprayer and mixing the mixture evenly to prepare glue-mixed wood shavings; (5) paving the rubber-mixed wood shavings obtained in step (4) to obtain a slab; (6) The slab prepared in step (5) is transported into the cavity of a microwave device by a conveyor belt, and is heated by microwaves. After microwave preheating, a preheated slab is obtained; (7) Pressing the preheated slab obtained in step (6) into a sheet to obtain a formaldehyde-free particleboard; The method for preparing the antibacterial liquid in step (2) comprises the following steps: a. In parts by mass, 42 parts of carbonamide, 6 parts of primary oleic acid, 10 parts of ethyl vanillin, 3 parts of silane coupling agent KH570, 1 part of hydrochloric acid, and 0.6 parts of diisopropyl peroxydicarbonate were mixed, and the mixture was heated and stirred in a microwave to prepare a first mixture; b. Add 5 parts of diatomaceous earth powder to the first mixture prepared in step a, and treat under stirring to prepare a second mixture; c. Add 1.6 parts of triethanolamine and 300 parts of water to the second mixture prepared in step b, heat and stir, and prepare an antibacterial solution.

2. The process for preparing formaldehyde-free particleboard by mechanical activation and microwave synergistic method according to claim 1, characterized in that: In step a, the mixture was stirred at a microwave power of 300 W, a temperature of 56° C., and a rotation speed of 200 r / min for 2 h to obtain a first mixture.

3. The process for preparing formaldehyde-free particleboard by mechanical activation and microwave synergistic method according to claim 1, characterized in that: In step b, the mixture was stirred at a rotation speed of 300 r / min for 1 h to obtain a second mixture.

4. The process for preparing formaldehyde-free particleboard by mechanical activation and microwave synergistic method according to claim 1, characterized in that: In step c, the mixture is heated to 82° C. and stirred at a rotation speed of 400 r / min for 0.8 h to obtain an antibacterial liquid.

5. The process for preparing formaldehyde-free particleboard by mechanical activation and microwave synergistic method according to claim 1, characterized in that: The formaldehyde-free adhesive in step (3) is mixed evenly with water in a weight ratio of 1:1.6-2.

3.

6. The process for preparing formaldehyde-free particleboard by mechanical activation and microwave synergistic method according to claim 1, characterized in that: The adhesive in step (4) is 7%-8% of the weight of the total wood shavings powder in step (1).

7. The process for preparing formaldehyde-free particleboard by mechanical activation and microwave synergistic method according to claim 1, characterized in that: The slab thickness in step (5) is 18 mm and the slab size is 300 mm × 300 mm.

8. The process for preparing formaldehyde-free particleboard by mechanical activation and microwave synergistic method according to claim 1, characterized in that: In step (6), the conveyor belt speed is controlled to be 0.25-0.32 m / s.

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