Preparation method of high-strength super-water-resistant formaldehyde-free veneer artificial board

Abstract

The invention provides a preparation method of a formaldehyde-free veneer artificial board, which comprises the following steps: (1) an adhesive is applied to the surface of a veneer, the adhesive is composed of a part A and a part B. The part A is one or more of isocyanate or modified isocyanate, or a mixture of the isocyanate and one or more of dimorpholinyl diethyl ether and sulfolane, or a mixture of the isocyanate and the modified isocyanate, or a mixture of the isocyanate and the modified isocyanate, or a mixture of the isocyanate and the modified isocyanate and one or more of dimorpholinyl diethyl ether and sulfolane, or a mixture of the isocyanate and the modified isocyanate; the part B is a hydroxyl-terminated compound or a mixture of the hydroxyl-terminated compound, a catalyst and one or more of sulfolane, preferably, the glue applying amount of the part B in different layers of veneers is different, and the applying amount is gradually increased from the surface layer veneer to the core layer veneer; (2) forming a plate blank by the veneers according to a certain rule; and (3) feeding the plate blank into a hot press to prepare the formaldehyde-free added veneer type artificial board. The method for producing the formaldehyde-free veneer type artificial board is simple and easy in process, high in hot-pressing production efficiency, excellent in mechanical property, good in flatness and low in warping degree, and can resist boiling in boiling water for 72 hours.

Description

Technical Field

[0001] The present invention belongs to the field of wood-based panels, and particularly relates to a preparation method of a high-strength, super water-resistant and formaldehyde-free added veneer-based wood-based panel. Background Art

[0002] In recent years, with the improvement of people's environmental protection awareness, the development of formaldehyde-free wood-based panels has been rapid. Major customized home furnishing enterprises have successively launched formaldehyde-free home products, and the formaldehyde-freeization of wood-based panels has gained popularity. Currently, the adhesives used in formaldehyde-free wood-based panels mainly include isocyanate adhesives, biomass adhesives, etc., among which isocyanate adhesives account for the highest market share. Isocyanate itself does not contain free formaldehyde, has no VOCs release, no obvious odor, is green and environmentally friendly, and its cured product, polyurea, has high strength, good chemical stability and is not easily degraded. The prepared wood-based panels have good mechanical properties.

[0003] Currently, the isocyanate adhesive applied in wood-based panels mainly refers to PMDI (polymethylene polyphenyl polyisocyanate). CN101524857B discloses a method for preparing a formaldehyde-free added veneer-based wood-based panel, which uses pneumatic or non-pneumatic atomized spraying of PMDI for sizing, and then forms a blank and hot presses to obtain a formaldehyde-free added veneer-based wood-based panel. Its hot pressing factor is 30 - 72 s / mm. However, the hot pressing production rate is low, and the hot pressing time is long when producing thicker wood-based panels. For example, when producing a 15-mm-thick veneer-based wood-based panel, it takes at least 7.5 minutes at the fastest. CN 105856343A, CN 105773742A, CN 105818225A, and CN 105856345A all use the method of ultrasonic and cyclone synergistic atomization of PMDI for sizing, only optimizing the sizing method. The lowest hot pressing factor is 30 s / mm, and the hot pressing efficiency is still low. CN 114800727B discloses a technical solution for efficiently producing veneer-based wood-based panels with a polyether as a promoter and in combination with a microwave preheating process. The lowest hot pressing factor can reach 5 s / mm, but it requires that the promoter must be applied first and then the isocyanate. Adjusting the sizing order will significantly reduce the performance of the wood-based panels, and the requirements for the production process flow and equipment are relatively strict.

[0004] Therefore, it is necessary to seek a preparation method of a high-strength, super water-resistant and formaldehyde-free added veneer-based wood-based panel with high process tolerance, high production efficiency and reduced costs. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of a high-strength, super water-resistant and formaldehyde-free added veneer-based wood-based panel. By applying two parts of adhesives, A and B, the production efficiency of the wood-based panels can be improved, and the different layers of veneers in part B are added in a gradient manner, which can reduce the production cost and improve the performance of the wood-based panels.

[0006] To achieve the purpose of the invention, the following technical solutions are adopted in the present invention:

[0007] A preparation method of a high-strength, super water-resistant and formaldehyde-free veneer-based artificial board comprises the following steps:

[0008] (1) Apply an adhesive on the surface of the veneer;

[0009] (2) Compose the veneers treated in step (1) into a board blank;

[0010] (3) Feed the board blank into a hot press to make the board blank hot-pressed into shape.

[0011] In the present invention, the veneer can be a wood veneer or a non-wood veneer, including but not limited to eucalyptus veneer, pine veneer, poplar veneer, birch veneer, bamboo veneer, etc. Preferably, the moisture content of the veneer is controlled to be 5%-25%.

[0012] In the present invention, the adhesive comprises two parts, A and B, which are applied separately (it can be understood that in the present invention, single-sided gluing is adopted). Among them, part A is one or more of isocyanate or modified isocyanate, or a mixture of one or more of them and bis(morpholinyl)diethyl ether or sulfolane; part B is a terminal hydroxyl compound, or a mixture of a terminal hydroxyl compound and one or more of a catalyst and sulfolane, or an aqueous solution of the mixture;

[0013] As a preferred scheme, in part A of the adhesive, the mass ratio of isocyanate or modified isocyanate to bis(morpholinyl)diethyl ether is 100:(0-0.2), such as 100:0.01, 100:0.05, 100:0.1, 100:0.15, 100:0.2, etc.; the mass ratio of isocyanate or modified isocyanate to sulfolane is 100:(0-100), such as 100:1, 100:10, 100:20, 100:30, 100:50, 100:70, 100:80, 100:90, etc.; preferably, the dosage of at least one of bis(morpholinyl)diethyl ether and sulfolane is not 0, and more preferably, the dosages of both bis(morpholinyl)diethyl ether and sulfolane are not 0;

[0014] Preferably, the application amount of part A is 10-80 g / m 2 , preferably 20-70 g / m 2 , more preferably 30-60 g / m 2 ;

[0015] Isocyanate adhesives are classified into aromatic polyisocyanates and their modified isocyanate products, aliphatic polyisocyanates (including cycloaliphatic polyisocyanates) and their modified isocyanate products according to the structural characteristics of the connection between the isocyanate group and the carbon atom. Common types of isocyanates can be applied in the present invention. Among them, aromatic polyisocyanates, including toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI) and polymeric diphenylmethane diisocyanate (also known as polymeric MDI or PMDI), etc., have relatively high reactivity. Therefore, in a preferred embodiment of the present invention, the isocyanate is preferably an aromatic polyisocyanate, more preferably one or more of toluene diisocyanate, diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate. At the same time, modified isocyanate products based on PMDI or TDI or MDI or their compositions can also be used as isocyanate adhesives in the present invention. Further, the modified isocyanate products include, but are not limited to, polyether modification or polyester modification;

[0016] In the present invention, the -NCO content of the isocyanate or modified isocyanate is 20 - 34 wt%;

[0017] By compounding the isocyanate with components such as bis(morpholino)diethyl ether and sulfolane, the reaction activity of the system can be improved, the curing can be accelerated, and the production efficiency can be increased.

[0018] In the present invention, as a preferred scheme, in part B of the adhesive, the mass ratio of the hydroxyl-terminated compound to the catalyst is 100:(0 - 2), preferably 100:(0 - 1), such as 100:0.01, 100:0.05, 100:0.08, 100:0.1, 100:0.5, 100:1.5, etc.; the mass ratio of the hydroxyl-terminated compound to sulfolane is 100:(0 - 250), such as 100:1, 100:10, 100:20, 100:40, 100:50, 100:80, 100:100, 100:120, 100:140, 100:150, 100:200, 100:230, etc.; preferably, the dosage of at least one of the catalyst and sulfolane is not 0, and more preferably, the dosages of both the catalyst and sulfolane are not 0;

[0019] Preferably, the application amount of part B is 0 - 50 g / m 2 (It can be understood that 0 here means that the dosage of part B in a certain layer is 0, not that part B is not added to the whole artificial board). More preferably, part B is formulated into an aqueous solution for application, and the addition amount of water does not exceed 70% (such as 60%, 50%, etc.).

[0020] In the B part of the adhesive, the hydroxyl-terminated compounds include at least one of polyether polyols, polyester polyols, small molecule polyols, etc. Preferably, the polyether polyol has a functionality of 2-4 and a molecular weight of 500-6000 (such as 1000, 2000, 3000, 4000, 5000, etc.); the polyester polyol has a functionality of 2-3 and a molecular weight of 500-3000 (such as 1000, 2000, 3000, etc.); the small molecule polyols include but are not limited to triethanolamine, glycerol, pentaerythritol, trimethylolpropane, trimethylolethane, etc. The hydroxyl-terminated compounds can react with isocyanates, or can improve the compatibility of water and isocyanates, or promote the reaction of water and isocyanates, so that the adhesive cures;

[0021] The catalyst helps to increase the reaction rate of isocyanates with water or hydroxyl-terminated compounds. Preferably, the catalyst in the B part is a tertiary amine catalyst, and the tertiary amine catalysts include but are not limited to triethanolamine, pentamethyldiethylenetriamine, pentamethyldipropylenetriamine, tetramethylethylenediamine, tetramethylpropylenediamine, tetramethylhexamethylenediamine, tris(dimethylaminopropyl)amine, dimethylethanolamine, trimethylhydroxyethylpropylenediamine, N-(dimethylaminopropyl)diisopropanolamine, N-methyl-N'-hydroxyethylpiperazine, dimethylaminoethoxyethanol, trimethylhydroxyethylethylenediamine, 1,4-dimethylpiperazine, N-ethylmorpholine, bis(morpholinyl)diethyl ether, triethylamine, triethylenediamine, bis[2-(N,N-dimethylaminoethyl)]ether, N,N,N'-trimethyl-N'-hydroxyethylbisaminoethyl ether, one or more combinations of thermosensitive catalysts or their derivatives, preferably thermosensitive catalysts, and more preferably the thermosensitive mutation temperature point is 35-90 °C;

[0022] A thermosensitive catalyst refers to a type of catalyst whose catalytic activity is low when the temperature is lower than the thermosensitive point of the catalyst, and whose catalytic activity increases significantly when the temperature reaches or exceeds the thermosensitive point. According to the factory production conditions, a catalyst with a thermosensitive point higher than room temperature is generally selected. In this way, even if the slab after sizing does not enter the hot press in time, the adhesive will not be over-precured. After entering the hot press, the temperature of the slab gradually rises to the thermosensitive point of the catalyst, and the adhesive cures rapidly, thus effectively improving production efficiency;

[0023] Preferably, the mass of part B applied to the veneer surfaces of different layers of the slab is different, following the principle of "less near the surface layer, more near the core layer, and centrosymmetric". During actual production, usually, the upper and lower surfaces of the slab are heated and pressed to cure the adhesive, and the veneers are bonded into a board. From the above description, it can be known that the main function of part B of the adhesive is to promote the rapid curing of the isocyanate in part A. During the hot pressing process, heat is gradually transferred from the surface of the slab to the core of the board, that is, there is a temperature difference when looking at the thickness profile of the board, with the surface board having a higher temperature and the core board having a lower temperature. Therefore, the application amount of part B of the veneer near the surface can be less, and the application amount near the core can be more. Taking the production of an n-layer board as an example, the veneers used from the lower surface to the upper surface of the board are defined as veneer layer 1 to veneer layer n. The application amount of part B on the surfaces of veneer layer 1 to veneer layer (n - 1) / 2 increases in sequence, and the application amounts of the corresponding veneer layers on both sides of the central symmetry plane of the board are the same (for example, when producing a 5-layer board, the mass of part B applied to the surfaces of the first layer and the fourth layer is the same, and the mass of part B applied to the surfaces of the second and third layers is the same; when n is 3, the mass of part B of the first and second layers is the same). Preferably, the difference in the amount of part B between adjacent layers is 3 - 35 g / m 2 . This sizing method saves costs on the one hand, and on the other hand, the adhesives of each layer are cured synchronously, the internal stress of the board is small, and the physical properties of the board are better.

[0024] In the present invention, step (2) is specifically: forming a plywood slab by arranging the veneers treated in step (1) according to the odd-layer principle;

[0025] In the present invention, before feeding the slab into the hot press in step (3), the slab is optionally preheated, and the preheating methods include but are not limited to microwave preheating, steam preheating, and flue gas preheating; preferably, in step (3), the hot pressing temperature is 100 - 250 °C, the surface pressure of hot pressing is 0 - 5 MPa (preferably 0.1 - 4.5 MPa), and the hot pressing factor is controlled to be 2 - 15 s / mm according to the thickness of the board.

[0026] The method of the present invention can be applied to the preparation of veneer-based wood-based panels, etc., and is particularly suitable for the preparation of wood-based panels with a veneer thickness of more than 1 mm.

[0027] The beneficial effects of the present invention are as follows:

[0028] (1) The present invention provides a method for preparing a high-strength, super water-resistant, formaldehyde-free veneer-based wood-based panel: by using a two-component adhesive system of isocyanate and hydroxyl-terminated compound, and respectively compounding a catalyst and / or sulfolane, the curing rate of the adhesive is increased, the hot pressing production efficiency of the veneer-based wood-based panel is effectively improved, and there is a significant improvement compared with the prior art.

[0029] (2) In the present invention, the system of terminal hydroxy compounds is applied in a gradient manner on different layers of veneers, reducing the cost of adhesives, improving the physical properties of the board, with excellent mechanical properties of the board, being resistant to boiling water for 72 hours, having good flatness and low warpage.

[0030] (3) The solution provided by the present invention for improving the hot pressing production efficiency of veneer-based wood-based panels is simple and easy to implement, with extremely high practical operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of a wood-based panel of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] For the convenience of understanding the present invention, the present invention will be further described below in conjunction with embodiments. It should be understood that the following embodiments are only for better understanding of the present invention and do not mean that the present invention is limited only to the following embodiments.

[0033] Sources of main raw materials

[0034] Polymethylene polyphenyl polyisocyanate (PMDI): WANNATE CW20, -NCO content 30.5 - 32%;

[0035] Modified isocyanate: WANNATE PM-300E, -NCO content 30.5 - 30.6%;

[0036] Polyether polyol A: WANALYST KC362, molecular weight 1000, functionality 3;

[0037] Polyether polyol B: WANALYST KC373, molecular weight 4000, functionality 3;

[0038] Polyester polyol A: obtained by polycondensation of glycerol, ethylene glycol and adipic acid, molecular weight 1500, functionality 3;

[0039] Glycerol, Nanjing Yingguan New Material Technology Co., Ltd.;

[0040] Triethanolamine, Henan Jun Nuo Chemical Products Co., Ltd.;

[0041] Sulfolane, Shandong Ran Xi Chemical Industry;

[0042] Dimorpholinodiethyl ether, Jiangdu Dajiang Chemical Industry Co., Ltd., Jiangsu Province;

[0043] Di[2-(N,N-dimethylaminoethyl)] ether, Yutian Chemical Industry Co., Ltd., Liyang City, Jiangsu Province;

[0044] N,N,N'-trimethyl-N'-hydroxyethyl bis(aminoethyl) ether, Huntsman Corporation, USA;

[0045] Thermosensitive catalyst A: The thermosensitive point is around 70°C, commercially available;

[0046] Thermosensitive catalyst B: The thermosensitive point is around 40°C, commercially available;

[0047] Thermosensitive catalyst C: The thermosensitive point is 60 - 80°C, commercially available;

[0048] Eucalyptus veneer, with a moisture content of 25% and a thickness of 2.2 mm;

[0049] Eucalyptus veneer, with a moisture content of 10% and a thickness of 2.2 mm;

[0050] Eucalyptus veneer, with a moisture content of 5% and a thickness of 2.2 mm.

[0051] Main test methods

[0052] The I - type bonding strength of the board is carried out according to the provisions of 4.17.4.2.c) in GB / T 17657 - 2022;

[0053] The 72 - hour boiling water test of the board is carried out according to the provisions of 4.17.4.2.d) in GB / T 17657 - 2022;

[0054] The formaldehyde release of the board is carried out according to the provisions of the formaldehyde release determination in GB 18580;

[0055] The elastic modulus of the board is carried out according to the provisions of 4.7 in GB / T 17657 - 2013;

[0056] The warp of the board is carried out according to the provisions of 8.5 in GB / T 19367 - 2009.

[0057] Example 1

[0058] The mass ratios of the various materials in the adhesive are as follows:

[0059] Part A, CW20: Dimorpholinodiethylether: Sulfolane = 100:0.02:20

[0060] Part B, Polyether polyol A: Dimorpholinodiethylether: Sulfolane = 100:0.1:200.

[0061] The process of making a 9 - layer board is as follows:

[0062] Using eucalyptus veneer with a moisture content of 10% as the base material; First, apply Part A to the surface of the above - mentioned veneer, and the application amount is 50 g / m 2; The B part is not applied to the first layer and the eighth layer, the application amount of the B part for the second layer and the seventh layer is 5 g / m2, the application amount of the B part for the third layer and the sixth layer is 10 g / m2, and the application amount of the B part for the fourth layer and the fifth layer is 20 g / m2; Then, the sized veneers are composed into a 9-layer plywood blank according to the odd-layer principle with the fiber directions of adjacent veneers perpendicular to each other; The blank is fed into a hot press, the hot pressing temperature is 200 °C, the high-pressure section of the hot pressing pressure is 3 MPa, the low-pressure section of the hot pressing pressure is 0.5 MPa, and the hot pressing factor is 4 s / mm, obtaining a formaldehyde-free plywood.

[0063] The test results of the board properties are shown in Table 1.

[0064] Example 2

[0065] The mass ratios of the various materials in the adhesive are as follows:

[0066] Part A, CW20

[0067] Part B, polyether polyol B: thermosensitive catalyst A: water = 100:1:125

[0068] The process for manufacturing a 3-layer board is as follows:

[0069] Using eucalyptus veneer with a moisture content of 10% as the base material; First, apply Part A to the surface of the above-mentioned veneer, and the application amount is 80 g / m 2 ; The application amount of Part B is 40 g / m 2 ; Then, the treated veneers are composed into a 3-layer plywood blank according to the odd-layer principle with the fiber directions of adjacent veneers perpendicular to each other; Preheat the blank using microwave, and the central temperature of the blank after preheating is 60 °C; Feed the blank into a hot press, the hot pressing temperature is 250 °C, the hot pressing pressure is 1 MPa, and the hot pressing factor is 2 s / mm, obtaining a formaldehyde-free plywood.

[0070] The test results of the board properties are shown in Table 1.

[0071] Example 3

[0072] The mass ratios of the various materials in the adhesive are as follows:

[0073] Part A, CW20: bis(morpholino)diethyl ether: sulfolane = 100:0.2:80

[0074] Part B, polyester polyol A: thermosensitive catalyst B: sulfolane = 100:0.5:50

[0075] The process for manufacturing a 5-layer board is as follows:

[0076] Using eucalyptus veneer with a moisture content of 25% as the base material; First, apply Part B to the surface of the veneer, and the application amount for the first layer and the fourth layer is 10 g / m 2, the second and third layers are 25 g / m2; then the component A is applied to the surface of the above veneer, and the application amount is 60 g / m 2 ; then the treated veneers are composed into a 5-layer plywood blank according to the odd-layer principle and the fiber directions of adjacent veneers are perpendicular to each other; the blank is sent into a hot press, the hot pressing temperature is 100 °C, the high-pressure section of the hot pressing pressure is 2 MPa, the low-pressure section of the hot pressing pressure is 0.1 MPa, and the hot pressing factor is 15 s / mm, obtaining formaldehyde-free plywood.

[0077] The test results of the board properties are shown in Table 1.

[0078] Example 4

[0079] The mass ratios of the various materials in the adhesive are as follows:

[0080] Part A, PM300E: bis(morpholinyl)diethyl ether: sulfolane = 100:0.1:100

[0081] Part B, glycerol: bis[2-(N,N-dimethylaminoethyl)]ether: sulfolane = 100:2:50

[0082] The process for manufacturing a 9-layer board is as follows:

[0083] Using eucalyptus veneer with a moisture content of 10% as the base material; first, part A is applied to the surface of the veneer, and the application amount is 65 g / m 2 ; then part B is applied, the application amount for the first and eighth layers is 5 g / m 2 , the application amount for the second and seventh layers is 15 g / m 2 , the application amount for the third and sixth layers is 18 g / m 2 , the application amount for the fourth and fifth layers is 25 g / m 2 . Then the treated veneers are composed into a 9-layer plywood blank according to the odd-layer principle and the fiber directions of adjacent veneers are perpendicular to each other; the blank is sent into a hot press, the hot pressing temperature is 180 °C, the high-pressure section of the hot pressing pressure is 1.5 MPa, the low-pressure section of the hot pressing pressure is 0.3 MPa, and the hot pressing factor is 5 s / mm, obtaining formaldehyde-free plywood.

[0084] The test results of the board properties are shown in Table 1.

[0085] Example 5

[0086] The mass ratios of the various materials in the adhesive are as follows:

[0087] Part A, PM300E: bis(morpholinyl)diethyl ether: sulfolane = 100:0.01:10

[0088] Part B, glycerol: triethanolamine: heat-sensitive catalyst C = 100:0.2:0.5

[0089] The manufacturing process of the 7-layer board is as follows: Use eucalyptus veneer with a moisture content of 10% as the base material; first apply part B to the surface of the veneer, with an application amount of 8 g / m for the first and sixth layers 2 , 13 g / m for the second and fifth layers 2 , and 20 g / m for the third and fourth layers 2 ; then apply part A to the surface of the above-mentioned veneer by spraying, with an application amount of 40 g / m 2 ; then stack the treated veneers according to the odd-layer principle with the fiber directions of adjacent veneers perpendicular to each other to form a 7-layer plywood blank; send the blank into a hot press, with a hot pressing temperature of 180 °C, a high-pressure section of the hot pressing pressure of 1.5 MPa, a low-pressure section of the hot pressing pressure of 0.3 MPa, and a hot pressing factor of 4 s / mm, to obtain formaldehyde-free plywood.

[0090] The test results of the board properties are shown in Table 1.

[0091] Example 6

[0092] The mass ratios of the various materials in the adhesive are as follows:

[0093] For part A, PM300E: bis(morpholinodiethyl)ether: sulfolane = 100:0:10

[0094] For part B, polyether polyol B: sulfolane = 100:30

[0095] The manufacturing process of the 5-layer board is as follows:

[0096] Use eucalyptus veneer with a moisture content of 5% as the base material; first apply part A to the surface of the veneer, with an application amount of 10 g / m 2 ; then apply part B to the surface of the above-mentioned veneer, with an application amount of 15 g / m for the first and fourth layers 2 , and 50 g / m for the second and third layers 2 ; then stack the treated veneers according to the odd-layer principle with the fiber directions of adjacent veneers perpendicular to each other to form a 5-layer plywood blank; send the blank into a hot press, with a hot pressing temperature of 140 °C, a high-pressure section of the hot pressing pressure of 1.8 MPa, a low-pressure section of the hot pressing pressure of 0.4 MPa, and a hot pressing factor of 9 s / mm, to obtain formaldehyde-free plywood.

[0097] The test results of the board properties are shown in Table 1.

[0098] Example 7

[0099] The mass ratios of the various materials in the adhesive are as follows:

[0100] For part A, CW20

[0101] For part B, polyether polyol B: sulfolane = 100:125

[0102] The manufacturing process of the 9-layer board is as follows:

[0103] Use eucalyptus veneer with a moisture content of 10% as the base material; first apply part A to the surface of the veneer, with an application amount of 40 g / m 2 ; then apply part B to the surface of the above veneer. The application amount for the first and eighth layers is 10 g / m 2 , the application amount for the second and seventh layers is 15 g / m 2 , the application amount for the third and sixth layers is 18 g / m 2 , the application amount for the fourth and fifth layers is 24 g / m 2 ; then stack the treated veneers according to the odd-layer principle with the fiber directions of adjacent veneers perpendicular to each other to form a 9-layer plywood blank; send the blank into a hot press, with a hot pressing temperature of 190 °C, a high-pressure section of the hot pressing pressure of 1.8 MPa, a low-pressure section of the hot pressing pressure of 0.4 MPa, and a hot pressing factor of 6 s / mm to obtain a formaldehyde-free plywood.

[0104] The test results of the board properties are shown in Table 1.

[0105] Example 8

[0106] Compared with Example 7, sulfolane is not added to part B, and other conditions remain unchanged. The test results of the board properties are shown in Table 1.

[0107] Example 9

[0108] Compared with Example 2, thermal-sensitive catalyst A is not added to part B, and other conditions remain unchanged. The test results of the board properties are shown in Table 1.

[0109] Example 10

[0110] Compared with Example 7, the application amount of part B for each layer of veneer is 24 g / m2, and other conditions remain unchanged. The test results of the board properties are shown in Table 1.

[0111] Comparative Example 1

[0112] Compared with Example 7, only CW20 is applied, and no other components are applied. Other conditions remain unchanged. The test results of the board properties are shown in Table 1.

[0113] Comparative Example 2

[0114] The veneer used was tested for formaldehyde emission by the climate chamber method, with the same method as in Example 1. The results are shown in Table 1.

[0115] Table 1 Summary of Test Results of Veneer-based Wood-based Panels

[0116]

[0117] The test results of the sheet materials in Examples 1-10 show that high-strength, super water-resistant and environmentally friendly excellent sheet materials can be prepared by using the two-component adhesive system of A and B. The comparison of the formaldehyde release amount of the wood veneer in Comparative Example 2 shows that the formaldehyde release amount of the sheet materials obtained by the technical solution provided by the present invention is equivalent to that of the raw veneer.

[0118] The comparison results between Example 8 and Example 7, and between Example 9 and Example 2 show that the use of sulfolane and thermal-sensitive catalyst in the system plays an important role in further improving the sheet material properties.

[0119] Compared with Example 7, in Comparative Example 1, without using the hydroxyl-terminated compound, catalyst and sulfolane, the curing rate of the adhesive is slow, and the bonding strength and water resistance are poor. Using part B is the premise to ensure a high sheet material production efficiency.

[0120] Compared with Example 7, in Example 10, the application amount of part B of each layer of veneer is the same, without gradient addition, and the warpage degree is significantly increased.

[0121] It is easy to understand that the above examples are only for illustration and do not mean that the present invention is limited thereto. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the embodiments here. The obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing a formaldehyde-free veneer-type artificial board, characterized in that: The following steps are included: (1) Apply adhesive on the surface of the veneer; (2) forming a slab from the veneer processed in step (1); (3) feeding the slab into a hot press to form the slab by hot pressing; Wherein, the adhesive comprises two parts, A and B, which are applied separately; Wherein, part A is one or more of isocyanate or modified isocyanate, or a mixture thereof with one or more of bismorpholinyl diethyl ether and sulfolane; preferably, the mass ratio of isocyanate or modified isocyanate to bismorpholinyl diethyl ether is 100:(0-0.2), and the mass ratio of isocyanate or modified isocyanate to sulfolane is 100:(0-100), preferably, at least one of bismorpholinyl diethyl ether and sulfolane is not 0, more preferably, the amount of both bismorpholinyl diethyl ether and sulfolane is not 0; Part B is a terminal hydroxyl compound, or a mixture of a terminal hydroxyl compound and one or more of a catalyst and sulfolane, or an aqueous solution of the mixture; preferably, the mass ratio of the terminal hydroxyl compound to the catalyst is 100:(0-2), and the mass ratio of the terminal hydroxyl compound to sulfolane is 100:(0-250), preferably, at least one of the amount of the catalyst and the sulfolane is not 0, more preferably, the amount of the catalyst and the sulfolane is not 0; preferably, the aqueous solution of the mixture contains no more than 70% water.

2. The preparation method according to claim 1, characterized in that: The isocyanate or modified isocyanate includes one or more of aromatic polyisocyanate and modified isocyanate products thereof, aliphatic polyisocyanate and modified isocyanate products thereof, preferably one or more of toluene diisocyanate and modified isocyanate products thereof, diphenylmethane diisocyanate and modified isocyanate products thereof, polymethylene polyphenyl polyisocyanate and modified isocyanate products thereof, preferably, the modified isocyanate product is polyether modified or polyester modified; Preferably, the -NCO content of the isocyanate or modified isocyanate is 20-34 wt %.

3. The preparation method according to claim 1 or 2, characterized in that: The application amount of the A part is 10-80g / m 2 , preferably 20-70g / m 2 , more preferably 30-60g / m 2 .

4. The preparation method according to claim 1, characterized in that: The terminal hydroxyl compound in part B of the adhesive includes at least one of polyether polyol, polyester polyol and small molecule polyol; Preferably, the polyether polyol has a functionality of 2-4 and a molecular weight of 500-6000. Preferably, the polyester polyol has a functionality of 2-3 and a molecular weight of 500-3000. Preferably, the small molecule polyol includes at least one of triethanolamine, glycerol, pentaerythritol, trimethylolpropane and trimethylolethane.

5. The preparation method according to claim 1 or 4, characterized in that: The catalyst in part B includes triethanolamine, pentamethyldiethylenetriamine, pentamethyldipropylenetriamine, tetramethylethylenediamine, tetramethylpropylenediamine, tetramethylhexanediamine, tri(dimethylaminopropyl)amine, dimethylethanolamine, trimethylhydroxyethylpropylenediamine, N-(dimethylaminopropyl)diisopropanolamine, N-methyl-N'-hydroxyethylpiperazine, dimethylaminoethoxyethanol, trimethylhydroxyethylethylenediamine, 1,4-dimethylpiperazine, N-ethylmorpholine, bismorpholinodiethyl ether, triethylamine, triethylenediamine, di[2-(N,N-dimethylaminoethyl)]ether, N,N,N'-trimethyl-N'-hydroxyethylbisaminoethyl ether, and a combination of one or more of a heat-sensitive catalyst, preferably a heat-sensitive catalyst, and more preferably a heat-sensitive mutation temperature point of 35-90°C.

6. The preparation method according to claim 1, 4 or 5, characterized in that: The amount of part B applied is 0-50g / m2. The mass of part B applied to the veneer surface of different layers of the slab is different, following the principle of "the closer to the surface layer, the less, the closer to the core layer, the higher, and the center is symmetrical". Preferably, the amount of part B applied to adjacent layers differs by 3-35g / m 2 .

7. The preparation method according to claim 1, characterized in that: The veneer is a wood or non-wood veneer, including a eucalyptus veneer, a pine veneer, a poplar veneer, a birch veneer or a bamboo veneer, and the moisture content of the veneer is preferably 5%-25%.

8. The preparation method according to any one of claims 1 to 7, characterized in that: Step (2) specifically comprises: forming a slab by forming the single plate processed in step (1) according to the odd number layer principle.

9. The preparation method according to any one of claims 1 to 5, characterized in that: In step (3), the hot pressing temperature is 100-250° C., the hot pressing plate surface pressure is 0-5 MPa (preferably 0.1-4.5 MPa), and the hot pressing factor is 2-15 s / mm.

10. The preparation method according to claim 9, characterized in that: In step (3), before the slab is fed into the hot press, the slab is optionally preheated, and the preheating method includes at least one of microwave preheating, steam preheating, and flue gas preheating.

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