Formaldehyde-free adhesive, preparation method and application thereof

Abstract

The application discloses a preparation method of a formaldehyde-free adhesive, and comprises the following steps: step one, preparing modified talcum powder; step two, mixing the modified talcum powder prepared in step one with polymeric methylene diphenyl diisocyanate, a wetting agent, a penetrating agent and a surfactant in a mass ratio of 42-60:105-121:4-6:1:0.6-1, adjusting the temperature to 45-50 DEG C, and stirring the mixture at a rotating speed of 300-400 r / min for 4-6 min to obtain a mixture c; and step three, adding a release agent to the mixture c obtained in step two in a mass ratio of 2-3, adjusting the temperature to 53-58 DEG C, and stirring the mixture at an ultrasonic power of 2-4 W / cm2 and a rotating speed of 200-300 r / min for 3-5 min to obtain the formaldehyde-free adhesive, wherein the adhesive has excellent performance, can meet the application in the preparation of artificial boards, and reduces the production cost.

Description

Technical Field

[0001] This invention belongs to the field of adhesive preparation technology, specifically relating to a formaldehyde-free adhesive, its preparation method, and its application. Background Technology

[0002] Currently, the industrial production of formaldehyde-free particleboard in China generally uses two main types of adhesives: isocyanate (PMDI) and modified biomass adhesives, with isocyanate adhesives being the most prevalent. Compared to traditional urea-formaldehyde resin, using formaldehyde-free adhesives to produce particleboard completely solves the formaldehyde emission problem, but its widespread application still needs to address two issues: firstly, the production cost is high and the price fluctuates greatly, especially since isocyanate is much more expensive than urea-formaldehyde resin; secondly, the production process is not mature enough. For example, when using isocyanate exclusively to prepare particleboard, problems such as sticking to steel strips, poor initial tack, incomplete board formation, easy clogging, and low production capacity arise. The largest components of particleboard cost are the cost of wood raw materials and the cost of adhesives. Reducing the cost of wood raw materials mainly involves expanding the scope of raw material utilization and lowering the quality requirements of raw materials, but lowering the quality of raw materials will seriously affect product quality.

[0003] PMDI, as an adhesive for particleboard, possesses strong bonding properties, capable of bonding particleboard with high moisture content, and does not release harmful gases such as formaldehyde. However, PMDI also has drawbacks in production applications. For example, its strong reactivity makes it prone to reacting with metals, causing a "steel strip sticking" phenomenon. PMDI has almost no initial tack, requiring the use of tackifiers and release agents, significantly increasing usage costs and operational complexity. Subsequent processing of PMDI-produced particleboard can also lead to edge chipping and tool wear. More importantly, without proper isolation and protection of the press, the toxic volatile substances released during the hot pressing process pose a far greater health hazard to frontline production workers than formaldehyde gas. Modified biomass adhesives that have entered the industrialization stage include lignin-based, soybean protein-based, and starch-based adhesives. Although they have achieved some success in laboratory and industrial batch applications, their high cost and some performance defects necessitate further improvements for large-scale industrial application. Summary of the Invention

[0004] This invention provides a formaldehyde-free adhesive, its preparation method, and its application, to solve the problems of poor initial tack and high cost of existing formaldehyde-free adhesives.

[0005] To solve the above technical problems, the present invention adopts the following technical solution:

[0006] A method for preparing a formaldehyde-free adhesive includes the following steps:

[0007] Step 1: Preparation of modified talc powder, including the following steps:

[0008] (1) Grind the clean talc and sieve it to obtain talc powder with a mesh size greater than 1500;

[0009] (2) Add sodium N-(2-aminoethyl)aminoethane sulfonate and polyethylene glycol fatty acid ester to the talc powder obtained in step (1), and stir and modify it for 2-3 hours at a microwave power of 300-400W, a temperature of 65-68℃ and a rotation speed of 200-400r / min to obtain mixture a.

[0010] (3) Add amino polydimethylsiloxane and polymaleic acid-chitosan to the mixture a obtained in step (2), and stir for 3-4 hours at a microwave power of 200-300W, a temperature of 82-90℃ and a rotation speed of 300-500r / min to obtain mixture b;

[0011] (4) The mixture b obtained in step (3) is dried at a temperature of 64-70℃ until the water content is ≤1%, then ground and sieved to obtain modified talc powder with a mesh size greater than 1500.

[0012] Step 2: Using parts by mass as the unit, mix 42-60 parts of modified talc powder obtained in step (4), 105-121 parts of polymeric methylene diphenyl diisocyanate, 4-6 parts of wetting agent, 1-2 parts of penetrant, and 0.6-1 parts of surfactant, adjust the temperature to 45-50℃, and stir at a speed of 300-400r / min for 4-6min to obtain mixture c;

[0013] Step 3: Add 2-3 parts by mass to the mixture c obtained in Step 2, adjust the temperature to 53-58℃, and stir for 3-5 minutes under ultrasonic power of 2-4W / cm² and rotation speed of 200-300r / min to obtain formaldehyde-free adhesive.

[0014] Further, in step (2), the weight ratio of talc, sodium N-(2-aminoethyl)aminoethane sulfonate, and polyethylene glycol fatty acid ester is (92-104):(2.6-3.5):(1-1.6).

[0015] Further, in step (3), the weight ratio of talc, aminopolydimethylsiloxane, and polymaleic acid-chitosan is (76-91):(1.3-2):(0.7-1.2).

[0016] Furthermore, the wetting agent mentioned in step two is composed of polyol, ethyl valerate, and water in a mass ratio of (3-6):(1-2):(5-8).

[0017] Furthermore, the polyol is pentaerythritol.

[0018] Furthermore, the penetrant mentioned in step two is composed of sodium α-alkenyl sulfonate and sodium secondary alkyl sulfate in a mass ratio of (2-4):(3-7).

[0019] Furthermore, the surfactant mentioned in step two is composed of fatty alcohol polyoxyethylene ether ammonium sulfate and sodium lauryl sulfate in a mass ratio of (3-4):(1-2).

[0020] Furthermore, the release agent mentioned in step three is composed of polyethylene wax and methyl silicone oil in a mass ratio of (1-3):(2-5).

[0021] The present invention has the following beneficial effects:

[0022] (1) The viscosity of the adhesive obtained by the present invention reaches 72.3 Pa·S or higher, which is significantly higher than the viscosity of the adhesive obtained by the prior art, by at least 14.4%. Furthermore, the process of the present invention can improve the initial tack of the adhesive, indicating that the technology of the present invention has significant progress compared with the prior art.

[0023] (2) The free formaldehyde content of the adhesive prepared by the present invention is 0 g / kg, indicating that the adhesive of the present invention is a formaldehyde-free adhesive. The particleboard products made with it are more environmentally friendly and can reduce the harm to the human body.

[0024] (3) Sodium N-(2-aminoethyl)aminoethane sulfonate and polyethylene glycol fatty acid ester play a synergistic role in the preparation of adhesives, and synergistically improve the viscosity of adhesives. This is because: Sodium N-(2-aminoethyl)aminoethane sulfonate and polyethylene glycol fatty acid ester contain amino, sulfonic acid, long carbon chain fatty acid and other groups, which can introduce amino, sulfonic acid, long carbon chain fatty acid and other groups on the surface of talc powder during modification. After surface modification, talc powder changes from hydrophilic to lipophilic, which improves the dispersibility of modified talc powder, facilitates its combination with other components in the preparation of adhesives, and improves the viscosity of adhesives.

[0025] (4) After talc powder is modified by sodium N-(2-aminoethyl)aminoethane sulfonate and polyethylene glycol fatty acid ester, it is further modified by amino polydimethylsiloxane and polymaleic acid-chitosan. Since amino polydimethylsiloxane and polymaleic acid-chitosan contain amino groups and silicon-oxygen bonds, the modified talc powder can improve the flame retardant and antibacterial properties of particleboard.

[0026] (5) After the surface modification of the modified talc powder of the present invention, it changes from hydrophilic to oleophilic, which improves the dispersibility of the modified talc powder. Compared with unmodified talc powder, the modified talc powder can fill more gaps between the wood chips. The cost of talc powder is low, and the relevant performance of the particleboard after filling with talc powder according to the formula of the present invention meets the national standard requirements. For the same production of one cubic meter of particleboard, the formaldehyde-free adhesive of the present invention can reduce the cost by 108 yuan compared with the formaldehyde-free adhesive of the prior art. Therefore, the formaldehyde-free adhesive of the present invention can greatly reduce the production cost of particleboard.

[0027] (6) The particleboard products produced using the formaldehyde-free adhesive obtained by the present invention have the following specifications: static bending strength ≥30.3 MPa, internal bond strength ≥0.81 MPa, flexural modulus of elasticity ≥4526 MPa, 24h water absorption thickness expansion rate ≤7.02%, and formaldehyde release <0.025 mg / m³. This indicates that the particleboard products obtained by the present invention have excellent mechanical properties and water absorption properties, and the formaldehyde release reaches the ENF level of the new national standard GB / T 39600-2021 "Classification of Formaldehyde Release of Wood-based Panels and Their Products", indicating that the particleboard products of the present invention have extremely high environmental performance. Detailed Implementation

[0028] To facilitate a better understanding of the present invention, the following examples are provided. These examples fall within the scope of protection of the present invention, but do not limit the scope of protection of the present invention.

[0029] In the embodiments, the method for preparing the formaldehyde-free adhesive includes the following steps:

[0030] Step 1: Preparation of modified talc powder, including the following steps:

[0031] (1) Grind the clean talc and sieve it to obtain talc powder with a mesh size greater than 1500;

[0032] (2) Add sodium N-(2-aminoethyl)aminoethanesulfonate and polyethylene glycol fatty acid ester to the talc powder obtained in step (1), and stir and modify it for 2-3 hours at a microwave power of 300-400W, a temperature of 65-68℃ and a rotation speed of 200-400r / min to obtain mixture a. The weight ratio of the talc powder, sodium N-(2-aminoethyl)aminoethanesulfonate and polyethylene glycol fatty acid ester is (92-104):(2.6-3.5):(1-1.6).

[0033] (3) Add aminopolydimethylsiloxane and polymaleic acid-chitosan to the mixture a obtained in step (2), and stir for 3-4 hours at a microwave power of 200-300W, a temperature of 82-90℃, and a rotation speed of 300-500r / min to obtain mixture b. The weight ratio of talc, aminopolydimethylsiloxane, and polymaleic acid-chitosan is (76-91):(1.3-2):(0.7-1.2).

[0034] (4) The mixture b obtained in step (3) is dried at a temperature of 64-70℃ until the water content is ≤1%, then ground and sieved to obtain modified talc powder with a mesh size greater than 1500.

[0035] Step 2: Using parts by mass as the unit, mix 42-60 parts of modified talc powder obtained in step (4), 105-121 parts of polymeric methylene diphenyl diisocyanate, 4-6 parts of wetting agent, 1-2 parts of penetrant, and 0.6-1 parts of surfactant, adjust the temperature to 45-50℃, and stir at a speed of 300-400r / min for 4-6min to obtain mixture c. The wetting agent is composed of polyol, ethyl valerate, and water in a mass ratio of (3-6):(1-2):(5-8), and the polyol is pentaerythritol.

[0036] The penetrant is composed of sodium α-alkenyl sulfonate and sodium secondary alkyl sulfate in a mass ratio of (2-4):(3-7);

[0037] The surfactant is composed of fatty alcohol polyoxyethylene ether ammonium sulfate and sodium lauryl sulfate in a mass ratio of (3-4):(1-2);

[0038] Step 3: Add 2-3 parts by mass to the mixture c obtained in Step 2, adjust the temperature to 53-58℃, and stir for 3-5 minutes under ultrasonic power of 2-4W / cm² and rotation speed of 200-300r / min to obtain formaldehyde-free adhesive. The release agent is composed of polyethylene wax and methyl silicone oil in a mass ratio of (1-3):(2-5).

[0039] The following describes the process through more specific embodiments.

[0040] Example 1

[0041] A method for preparing a formaldehyde-free adhesive includes the following steps:

[0042] Step 1: Preparation of modified talc powder, including the following steps:

[0043] (1) Grind the clean talc and sieve it to obtain 1600 mesh talc powder;

[0044] (2) Add sodium N-(2-aminoethyl)aminoethanesulfonate and polyethylene glycol fatty acid ester to the talc powder obtained in step (1), and stir and modify it for 3 hours at a microwave power of 300W, a temperature of 66℃ and a rotation speed of 200r / min to obtain mixture a. The weight ratio of the talc powder, sodium N-(2-aminoethyl)aminoethanesulfonate and polyethylene glycol fatty acid ester is 93:2.7:1.

[0045] (3) Add amino polydimethylsiloxane and polymaleic acid-chitosan to the mixture a obtained in step (2), and stir for 4 hours at a microwave power of 200W, a temperature of 82℃ and a rotation speed of 300r / min to obtain mixture b. The weight ratio of talc, amino polydimethylsiloxane and polymaleic acid-chitosan is 78:1.5:0.7.

[0046] (4) The mixture b obtained in step (3) is dried at 65°C until the water content is 1%, then ground and sieved to obtain 1600 mesh modified talc powder.

[0047] Step 2: Using parts by mass as the unit, mix 43 parts of modified talc powder obtained in step (4), 106 parts of polymeric methylene diphenyl diisocyanate, 4 parts of wetting agent, 1 part of penetrant, and 0.6 parts of surfactant, adjust the temperature to 46℃, and stir for 6 minutes at a speed of 300r / min to obtain mixture c. The wetting agent is composed of polyol, ethyl valerate, and water in a mass ratio of 3:1:6, and the polyol is pentaerythritol.

[0048] The penetrant is composed of sodium α-alkenyl sulfonate and sodium secondary alkyl sulfate in a mass ratio of 2:3;

[0049] The surfactant is composed of fatty alcohol polyoxyethylene ether ammonium sulfate and sodium lauryl sulfate in a mass ratio of 3:1.

[0050] Step 3: Add 2 parts by mass to the mixture c obtained in Step 2, adjust the temperature to 54℃, and stir for 5 minutes under ultrasonic power of 2W / cm² and rotation speed of 200r / min to obtain a formaldehyde-free adhesive. The release agent is composed of polyethylene wax and methyl silicone oil in a mass ratio of 1:2.

[0051] Example 2

[0052] A method for preparing a formaldehyde-free adhesive includes the following steps:

[0053] Step 1: Preparation of modified talc powder, including the following steps:

[0054] (1) Grind the clean talc and sieve it to obtain 1600 mesh talc powder;

[0055] (2) Add sodium N-(2-aminoethyl)aminoethanesulfonate and polyethylene glycol fatty acid ester to the talc powder obtained in step (1), and stir and modify it for 2.6 h at a microwave power of 300 W, a temperature of 67 °C and a rotation speed of 400 r / min to obtain mixture a. The weight ratio of the talc powder, sodium N-(2-aminoethyl)aminoethanesulfonate and polyethylene glycol fatty acid ester is 95:2.8:1.2.

[0056] (3) Add amino polydimethylsiloxane and polymaleic acid-chitosan to the mixture a obtained in step (2), and stir for 3.3 h at a microwave power of 200W, a temperature of 84℃ and a rotation speed of 400r / min to obtain mixture b. The weight ratio of talc, amino polydimethylsiloxane and polymaleic acid-chitosan is 80:1.5:0.8.

[0057] (4) The mixture b obtained in step (3) is dried at a temperature of 65°C until the water content is 0.9%, then ground and sieved to obtain 1600 mesh modified talc powder;

[0058] Step 2: Using parts by mass as the unit, mix 45 parts of modified talc powder obtained in step (4), 108 parts of polymeric methylene diphenyl diisocyanate, 4.6 parts of wetting agent, 1.2 parts of penetrant, and 0.7 parts of surfactant, adjust the temperature to 46℃, and stir for 6 minutes at a speed of 300 r / min to obtain mixture c. The wetting agent is composed of polyol, ethyl valerate, and water in a mass ratio of 4:1.2:6, and the polyol is pentaerythritol.

[0059] The penetrant is composed of sodium α-alkenyl sulfonate and sodium secondary alkyl sulfate in a mass ratio of 2.3:3.5;

[0060] The surfactant is composed of fatty alcohol polyoxyethylene ether ammonium sulfate and sodium lauryl sulfate in a mass ratio of 3.2:1.4;

[0061] Step 3: Add 2.3 parts by mass to the mixture c obtained in Step 2, adjust the temperature to 56℃, and stir for 4 minutes under ultrasonic power of 3W / cm² and rotation speed of 300r / min to obtain formaldehyde-free adhesive. The release agent is composed of polyethylene wax and methyl silicone oil in a mass ratio of 1.2:2.5.

[0062] Example 3

[0063] A method for preparing a formaldehyde-free adhesive includes the following steps:

[0064] Step 1: Preparation of modified talc powder, including the following steps:

[0065] (1) Grind the clean talc and sieve it to obtain 1600 mesh talc powder;

[0066] (2) Add sodium N-(2-aminoethyl)aminoethanesulfonate and polyethylene glycol fatty acid ester to the talc powder obtained in step (1), and stir and modify it for 2.6 h at a microwave power of 350W, a temperature of 67℃ and a rotation speed of 300r / min to obtain mixture a. The weight ratio of the talc powder, sodium N-(2-aminoethyl)aminoethanesulfonate and polyethylene glycol fatty acid ester is 100:3:1.4.

[0067] (3) Add amino polydimethylsiloxane and polymaleic acid-chitosan to the mixture a obtained in step (2), and stir for 3.6 hours at a microwave power of 260W, a temperature of 85℃ and a rotation speed of 400r / min to obtain mixture b. The weight ratio of talc, amino polydimethylsiloxane and polymaleic acid-chitosan is 85:1.8:1.

[0068] (4) The mixture b obtained in step (3) is dried at a temperature of 68°C until the water content is 1%, then ground and sieved to obtain 1600 mesh modified talc powder;

[0069] Step 2: Using parts by mass as the unit, mix 50 parts of modified talc powder obtained in step (4), 112 parts of polymeric methylene diphenyl diisocyanate, 5 parts of wetting agent, 1.6 parts of penetrant, and 0.9 parts of surfactant, adjust the temperature to 48℃, and stir for 5 minutes at a speed of 400 r / min to obtain mixture c. The wetting agent is composed of polyol, ethyl valerate, and water in a mass ratio of 5:1.6:7, and the polyol is pentaerythritol.

[0070] The penetrant is composed of sodium α-alkenyl sulfonate and sodium secondary alkyl sulfate in a mass ratio of 3:5;

[0071] The surfactant is composed of fatty alcohol polyoxyethylene ether ammonium sulfate and sodium lauryl sulfate in a mass ratio of 3.5:1.6;

[0072] Step 3: Add 2.5 parts by mass to the mixture c obtained in Step 2, adjust the temperature to 56℃, and stir for 4 minutes under ultrasonic power of 3W / cm² and rotation speed of 250r / min to obtain a formaldehyde-free adhesive. The release agent is composed of polyethylene wax and methyl silicone oil in a mass ratio of 2:3.

[0073] Example 4

[0074] A method for preparing a formaldehyde-free adhesive includes the following steps:

[0075] Step 1: Preparation of modified talc powder, including the following steps:

[0076] (1) Grind the clean talc and sieve it to obtain 1600 mesh talc powder;

[0077] (2) Add sodium N-(2-aminoethyl)aminoethanesulfonate and polyethylene glycol fatty acid ester to the talc powder obtained in step (1), and stir and modify it for 2.4 h at a microwave power of 400W, a temperature of 65℃ and a rotation speed of 400r / min to obtain mixture a. The weight ratio of the talc powder, sodium N-(2-aminoethyl)aminoethanesulfonate and polyethylene glycol fatty acid ester is 98:3:1.2.

[0078] (3) Add amino polydimethylsiloxane and polymaleic acid-chitosan to the mixture a obtained in step (2), and stir for 3.2 h at a microwave power of 200W, a temperature of 84℃ and a rotation speed of 400r / min to obtain mixture b. The weight ratio of talc, amino polydimethylsiloxane and polymaleic acid-chitosan is 83:1.7:1.

[0079] (4) The mixture b obtained in step (3) is dried at a temperature of 66°C until the water content is 1%, then ground and sieved to obtain 1600 mesh modified talc powder;

[0080] Step 2: Using parts by mass as the unit, mix 56 parts of modified talc powder, 115 parts of polymeric methylene diphenyl diisocyanate, 5.3 parts of wetting agent, 1.7 parts of penetrant, and 0.8 parts of surfactant obtained in step (4), adjust the temperature to 48℃, and stir for 5 minutes at a speed of 400 r / min to obtain mixture c. The wetting agent is composed of polyol, ethyl valerate, and water in a mass ratio of 5:1.7:7, and the polyol is pentaerythritol.

[0081] The penetrant is composed of sodium α-alkenyl sulfonate and sodium secondary alkyl sulfate in a mass ratio of 3:5;

[0082] The surfactant is composed of fatty alcohol polyoxyethylene ether ammonium sulfate and sodium lauryl sulfate in a mass ratio of 3.6:1.5;

[0083] Step 3: Add 2.8 parts by mass to the mixture c obtained in Step 2, adjust the temperature to 55℃, and stir for 4 minutes under ultrasonic power of 3W / cm² and rotation speed of 300r / min to obtain a formaldehyde-free adhesive. The release agent is composed of polyethylene wax and methyl silicone oil in a mass ratio of 2:5.

[0084] Example 5

[0085] A method for preparing a formaldehyde-free adhesive includes the following steps:

[0086] Step 1: Preparation of modified talc powder, including the following steps:

[0087] (1) Grind the clean talc and sieve it to obtain 1600 mesh talc powder;

[0088] (2) Add sodium N-(2-aminoethyl)aminoethanesulfonate and polyethylene glycol fatty acid ester to the talc powder obtained in step (1), and stir and modify it for 2 hours at a microwave power of 400W, a temperature of 68℃ and a rotation speed of 400r / min to obtain mixture a. The weight ratio of the talc powder, sodium N-(2-aminoethyl)aminoethanesulfonate and polyethylene glycol fatty acid ester is 103:3.5:1.5.

[0089] (3) Add amino polydimethylsiloxane and polymaleic acid-chitosan to the mixture a obtained in step (2), and stir for 3 hours at a microwave power of 300W, a temperature of 90℃ and a rotation speed of 500r / min to obtain mixture b. The weight ratio of talc, amino polydimethylsiloxane and polymaleic acid-chitosan is 90:2:1.1.

[0090] (4) The mixture b obtained in step (3) is dried at 70°C until the water content is 0.9%, then ground and sieved to obtain 1600 mesh modified talc powder;

[0091] Step 2: Using parts by mass as the unit, mix 60 parts of modified talc powder obtained in step (4), 120 parts of polymeric methylene diphenyl diisocyanate, 6 parts of wetting agent, 1.8 parts of penetrant, and 1 part of surfactant, adjust the temperature to 50℃, and stir at a speed of 400r / min for 4min to obtain mixture c. The wetting agent is composed of polyol, ethyl valerate, and water in a mass ratio of 6:2:7, and the polyol is pentaerythritol.

[0092] The penetrant is composed of sodium α-alkenyl sulfonate and sodium secondary alkyl sulfate in a mass ratio of 4:7;

[0093] The surfactant is composed of fatty alcohol polyoxyethylene ether ammonium sulfate and sodium lauryl sulfate in a mass ratio of 3:2.

[0094] Step 3: Add 3 parts by mass to the mixture c obtained in Step 2, adjust the temperature to 58℃, and stir for 3 minutes under ultrasonic power of 4W / cm² and rotation speed of 300r / min to obtain a formaldehyde-free adhesive. The release agent is composed of polyethylene wax and methyl silicone oil in a mass ratio of 3:5.

[0095] Comparative Example 1

[0096] The preparation process of the formaldehyde-free adhesive is basically the same as that of Example 3, except that sodium N-(2-aminoethyl)aminoethane sulfonate and polyethylene glycol fatty acid ester are not added in step (2).

[0097] Comparative Example 2

[0098] The preparation process of the formaldehyde-free adhesive is basically the same as that of Comparative Example 1, except that sodium N-(2-aminoethyl)aminoethanesulfonate is added in step (2).

[0099] Comparative Example 3

[0100] The preparation process of the formaldehyde-free adhesive is basically the same as that of Comparative Example 1, except that polyethylene glycol fatty acid ester is added in step (2).

[0101] Comparative Example 4

[0102] The formaldehyde-free adhesive was prepared using the process described in Example 3 of the Chinese patent document "A method for preparing a biomass-based modified formaldehyde-free environmentally friendly wood-based panel adhesive (Patent No.: ZL202210384329.7)".

[0103] Experimental example:

[0104] (a) Adhesive performance testing

[0105] The viscosity and free formaldehyde of the adhesives prepared in Examples 1-5 and Comparative Examples 1-4 were tested, and the test results are shown in the table below.

[0106]

[0107] The adhesive viscosity test was conducted according to the rotational viscometer method in the national standard GB / T2794-1995, at a test temperature of 25℃.

[0108] As can be seen from the table above: (1) As can be seen from the adhesive viscosity of Examples 1-5 and Comparative Example 4, the adhesive viscosity of the present invention is significantly higher than that of the adhesive obtained in Comparative Example 4, by at least 14.4%, indicating that the technology of the present invention has significant progress compared with the prior art.

[0109] (2) The free formaldehyde content of the adhesives prepared in Examples 1-5 is 0 g / kg, indicating that the adhesive of the present invention is a formaldehyde-free adhesive. The particleboard products made with it are more environmentally friendly and can reduce the harm to the human body.

[0110] (3) As can be seen from the viscosity of Example 3 and Comparative Examples 1-3, sodium N-(2-aminoethyl)aminoethane sulfonate and polyethylene glycol fatty acid ester play a synergistic role in the preparation of adhesives, and synergistically improve the viscosity of adhesives. This is because: sodium N-(2-aminoethyl)aminoethane sulfonate and polyethylene glycol fatty acid ester contain amino, sulfonic acid, long carbon chain fatty acid and other groups, which can introduce amino, sulfonic acid, long carbon chain fatty acid and other groups on the surface of talc powder during modification, so that after surface modification of talc powder, it changes from hydrophilic to lipophilic, improves the dispersibility of modified talc powder, and is conducive to combining with other components in the preparation of adhesives, thereby improving the viscosity of adhesives.

[0111] (ii) Preparation of particleboard using adhesives and performance testing

[0112] The preparation of particleboard using adhesives includes the following steps:

[0113] (1) The wood shavings are mixed by mechanical activation. The wood shavings are continuously subjected to high-energy impacts from zirconium balls, resulting in collisions between zirconium balls and powder, zirconium balls and powder, and finally forming fine, uniformly mixed, and well-dispersed wood shavings raw materials.

[0114] (3) The adhesives prepared in Examples 1-5 and Comparative Example 4 and the adhesives prepared in the control group (where the talc powder was not modified) were mixed with water at a weight ratio of 1:2 to obtain a diluted adhesive.

[0115] (4) Spray the diluted adhesive obtained in step (3) onto the antibacterial pretreated wood shavings obtained in step (2) using an atomizing spray gun and mix them evenly to obtain mixed wood shavings, wherein the adhesive accounts for 7.6% of the total weight of the wood shavings in step (1);

[0116] (5) The shavings obtained in step (4) are laid out to obtain a board blank, the board blank having a thickness of 18 mm and a surface size of 300 mm × 300 mm;

[0117] (6) The slab obtained in step (5) is conveyed into the cavity of the microwave equipment by a conveyor belt and heated by microwave with a heating power density of 15 W / g·m 3 The conveyor belt speed is controlled at 0.3 m / s, and the preheated slab is obtained after microwave preheating.

[0118] (7) Press the preheated slab obtained in step (6) to form a particleboard.

[0119] The particleboard prepared above was tested for static bending strength, internal bond strength, modulus of elasticity and water absorption thickness swelling rate according to GB / T 17657-2013. The formaldehyde emission was tested according to the provisions of 4.60 in GB / T 17657-2013. The evaluation grade was determined according to GB / T 39600-2021 "Classification of Formaldehyde Emission of Wood-based Panels and Their Products". The relevant results are shown in the table below.

[0120]

[0121] As can be seen from the table above: (1) As can be seen from the data of Examples 1-5, the particleboard product indicators obtained by the present invention are: static bending strength ≥30.3 MPa, internal bond strength ≥0.81 MPa, flexural modulus of elasticity ≥4526 MPa, 24h water absorption thickness expansion rate ≤7.02%, and formaldehyde release <0.025 mg / m³. This indicates that the particleboard product obtained by the present invention has excellent mechanical properties and water absorption properties, and the formaldehyde release reaches the ENF level of the new national standard GB / T 39600-2021 "Classification of Formaldehyde Release of Wood-based Panels and Their Products", indicating that the particleboard product of the present invention has extremely high environmental protection performance.

[0122] (2) The static bending strength, internal bond strength and flexural modulus of the particleboard products obtained in Examples 1-5 of the present invention are significantly better than those of the particleboard products obtained in Comparative Example 4, indicating that the technology of the present invention has made significant progress.

[0123] (3) The static bending strength, internal bond strength, flexural modulus of elasticity, and 24h water absorption thickness expansion rate of the particleboard products prepared in the control group were much worse than those of the particleboard products prepared in Examples 1-5. This may be because after the surface modification of talc powder, it changed from hydrophilic to oleophilic, which is conducive to its combination with other components in the preparation of formaldehyde-free adhesive, thereby improving the static bending strength, internal bond strength, and flexural modulus of elasticity of the final particleboard products and reducing the 24h water absorption thickness expansion rate.

[0124] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a formaldehyde-free adhesive, characterized in that, Includes the following steps: Step 1: Preparation of modified talc powder, including the following steps: (1) Grind the clean talc and sieve it to obtain talc powder with a mesh size greater than 1500; (2) Add sodium N-(2-aminoethyl)aminoethane sulfonate and polyethylene glycol fatty acid ester to the talc powder obtained in step (1), and stir and modify it for 2-3 hours at a microwave power of 300-400W, a temperature of 65-68℃ and a rotation speed of 200-400r / min to obtain mixture a. (3) Add amino polydimethylsiloxane and polymaleic acid-chitosan to the mixture a obtained in step (2), and stir for 3-4 hours at a microwave power of 200-300W, a temperature of 82-90℃ and a rotation speed of 300-500r / min to obtain mixture b; (4) The mixture b obtained in step (3) is dried at a temperature of 64-70℃ until the water content is ≤1%, then ground and sieved to obtain modified talc powder with a mesh size greater than 1500. Step 2: Using parts by mass as the unit, mix 42-60 parts of modified talc powder obtained in step (4), 105-121 parts of polymeric methylene diphenyl diisocyanate, 4-6 parts of wetting agent, 1-2 parts of penetrant, and 0.6-1 parts of surfactant, adjust the temperature to 45-50℃, and stir at a speed of 300-400r / min for 4-6min to obtain mixture c; Step 3: Add 2-3 parts by mass to the mixture c obtained in Step 2, adjust the temperature to 53-58℃, and stir for 3-5 minutes under ultrasonic power of 2-4W / cm² and rotation speed of 200-300r / min to obtain formaldehyde-free adhesive. The weight ratio of talc, sodium N-(2-aminoethyl)aminoethanesulfonate, and polyethylene glycol fatty acid ester in step (2) is (92-104):(2.6-3.5):(1-1.6). The weight ratio of talc, aminopolydimethylsiloxane, and polymaleic acid-chitosan in step (3) is (76-91):(1.3-2):(0.7-1.2). The wetting agent mentioned in step two is composed of polyol, ethyl valerate, and water in a mass ratio of (3-6):(1-2):(5-8); The penetrant mentioned in step two is composed of sodium α-alkenyl sulfonate and sodium secondary alkyl sulfate in a mass ratio of (2-4):(3-7); The surfactant mentioned in step two is composed of fatty alcohol polyoxyethylene ether ammonium sulfate and sodium lauryl sulfate in a mass ratio of (3-4):(1-2).

2. The method for preparing the formaldehyde-free adhesive according to claim 1, characterized in that, The polyol is pentaerythritol.

3. The method for preparing the formaldehyde-free adhesive according to claim 1, characterized in that, The release agent mentioned in step three is composed of polyethylene wax and methyl silicone oil in a mass ratio of (1-3):(2-5).

4. A formaldehyde-free adhesive prepared by the method according to any one of claims 1-3.

5. The application of the formaldehyde-free adhesive according to claim 4 in the preparation of engineered wood panels.

Images