CN115476411B - Method for producing aldehyde-free plywood - Google Patents
Method for producing aldehyde-free plywood Download PDFInfo
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- CN115476411B CN115476411B CN202110598976.3A CN202110598976A CN115476411B CN 115476411 B CN115476411 B CN 115476411B CN 202110598976 A CN202110598976 A CN 202110598976A CN 115476411 B CN115476411 B CN 115476411B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27D—WORKING VENEER OR PLYWOOD
- B27D1/00—Joining wood veneer with any material; Forming articles thereby; Preparatory processing of surfaces to be joined, e.g. scoring
- B27D1/04—Joining wood veneer with any material; Forming articles thereby; Preparatory processing of surfaces to be joined, e.g. scoring to produce plywood or articles made therefrom; Plywood sheets
- B27D1/08—Manufacture of shaped articles; Presses specially designed therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27D—WORKING VENEER OR PLYWOOD
- B27D1/00—Joining wood veneer with any material; Forming articles thereby; Preparatory processing of surfaces to be joined, e.g. scoring
- B27D1/04—Joining wood veneer with any material; Forming articles thereby; Preparatory processing of surfaces to be joined, e.g. scoring to produce plywood or articles made therefrom; Plywood sheets
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J175/00—Adhesives based on polyureas or polyurethanes; Adhesives based on derivatives of such polymers
- C09J175/04—Polyurethanes
Abstract
The invention provides a method for producing aldehyde-free plywood, which takes wooden veneers as raw materials, sprays isocyanate adhesives in an air or air-free way, then paves composite accelerator of a frame structure, and makes veneers after the adhesives and the accelerator are applied into the veneers to obtain the aldehyde-free plywood after assembly and hot pressing. The method for producing the aldehyde-free plywood is simple and easy in process, high in hot pressing production efficiency, excellent in mechanical property of the board and high in dimensional stability of the product.
Description
Technical Field
The invention belongs to the field of artificial boards, and particularly relates to a method for producing aldehyde-free plywood.
Background
In recent years, with the improvement of environmental protection consciousness of people, the development of the formaldehyde-free artificial board is rapid, various custom-made household enterprises develop formaldehyde-free household products, and the formaldehyde-free artificial board is deep. The adhesives used for the formaldehyde-free artificial board at present mainly comprise isocyanate adhesives, biomass adhesives and the like, wherein the isocyanate adhesives have the highest market share. The isocyanate does not contain free formaldehyde, does not release VOCs, has no obvious smell, is green and environment-friendly, and the solidified product polyurea has high strength, good chemical stability and difficult degradation, and the prepared plate has good mechanical properties.
The isocyanate adhesives currently used in artificial boards are mainly PMDI (polymethylene polyphenyl polyisocyanates). Because PMDI is expensive, it is common to apply glue by spraying for cost reasons to save on glue usage. CN101524857B discloses a method for preparing aldehyde-free plywood, which adopts air or non-air atomized spray PMDI to carry out sizing, then assembling and hot-pressing to obtain aldehyde-free plywood, wherein the hot-pressing factor is 0.5-1.2min/mm. CN 105856343A, CN 105773742A, CN 105818225A and CN 105856345a are all glued by ultrasonic and air-rotating co-atomizing PMDI, only the gluing mode is optimized, the hot pressing factor is at least 40s/mm, and the hot pressing efficiency is still slow.
In polyurethane chemistry, the reaction rate is generally increased by adding an accelerator to the polyol, but since the accelerator is directly mixed with isocyanate, the isocyanate accelerates self-polymerization to deteriorate, and a better adhesive effect cannot be obtained. Therefore, a suitable accelerator adding mode is required to be sought for producing the aldehyde-free artificial board with higher hot pressing efficiency.
Disclosure of Invention
The invention aims to provide a method for producing aldehyde-free plywood, which improves the hot-pressing efficiency of a plate by adding a composite accelerator with a frame structure, thereby improving the production efficiency of the plate.
In order to achieve the aim of the invention, the following technical scheme is adopted:
a method of producing an aldehyde-free plywood comprising the steps of:
(1) Spraying isocyanate adhesive on the surface of the wood veneer;
(2) The wood veneer surface paving modification accelerator is obtained in the step (1);
(3) Assembling veneers;
(4) And (5) hot-press molding the plate.
Preferably, the wood veneer is one or more of common tree species such as poplar, eucalyptus, pine, birch, basswood, crabapple, lotus, maple, elm, fir, oak or rubber wood, and the water content is 10-25 wt%, preferably 13-17 wt%.
Isocyanates of the type commonly known as aromatic polyisocyanates, aliphatic polyisocyanates (including cycloaliphatic polyisocyanates) can be used in the present invention, depending on the structural characteristics of the isocyanate groups attached to the carbon atoms. Among them, aromatic polyisocyanates such as Toluene Diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymeric diphenylmethane diisocyanate (also known as polymeric MDI or PMDI) and the like are relatively inexpensive, and therefore, in a preferred embodiment, the isocyanate is preferably an aromatic polyisocyanate, and further preferably one or more of toluene diisocyanate, diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate. Modified products based on isocyanates, preferably PMDI or TDI or MDI or combinations thereof, can also be used in the present invention as isocyanate adhesives in the present invention. The modified isocyanate includes, but is not limited to polyether modification or polyester modification, preferably, the isocyanate adhesive has an-NCO content of 20 to 34wt%. The isocyanate adhesive sizing mode can be airflow spraying sizing or airless spraying sizing.
The isocyanate structure contains isocyanate (-NCO) groups with extremely high chemical reactivity, and the accelerator cannot be directly contacted with the isocyanate, otherwise, severe reaction can be initiated, so that the isocyanate is pre-cured before hot pressing, and effective adhesion cannot be formed on the wood veneer.
In the present invention, the modifying accelerator is a composite accelerator having a framework structure, and the composite accelerator comprises a framework material and an accelerator, wherein the framework material is a porous material or a layered material, preferably activated carbon, mesoporous molecular sieve or layered MXene, the particle size of the framework material is preferably 0.5-150 μm, the accelerator is a common accelerator used for improving the isocyanate reaction rate in the field of isocyanate curing agents, and the accelerator is selected from water-soluble amine catalysts (such as tertiary amine catalysts) and/or organometallic catalysts, such as water-soluble alcohol amine, N-alkyl morpholine, tetramethyl alkylene polyamine, pentamethylene polyamine, water-soluble metal tin catalysts and other water-soluble accelerators commonly used in the field, and the accelerator comprises but is not limited to monoethanolamine, diethanolamine, triethanolamine, dimethylethanolamine, bis (dimethylaminoethyl) ether, pentamethyl dialkyltriamine, tetramethyl alkylene diamine, 2,4, 6-tris (dimethylaminomethyl) phenol, tris (dimethylaminopropyl) hexahydrotriazine, dimethylaminoethoxyethanol, trimethylhydroxyethyl ethylenediamine, dimethylhydroxyethyl ethylenediamine, dimethylisopropyl amine, diethylenetriamine, N-diethyl morpholine, N- (dimethyl) dihydroethyl) amine, N-butyl) dimethyl morpholine, N- (N-dimethyl) propane, N-dimethyl) propane.
Further, the accelerator is preferably alcohol amine and/or potassium carboxylate.
The active carbon is prepared by heating organic raw materials (fruit shell, coal, wood, etc.) under air-isolated condition to reduce non-carbon components (this process is called carbonization), then reacting with gas, and eroding the surface to produce a structure with developed micropores, the diameter of which is mostly between 2-50 nm. The mesoporous molecular sieve generally refers to an inorganic porous material which is synthesized by using a surfactant as a template agent and utilizing chemical processes such as sol-gel, emulsification or microemulsification and the like and through the interfacial effect between an organic substance and an inorganic substance, has a pore diameter of 2-50nm and has a regular pore structure. The MXene two-dimensional crystal is a novel two-dimensional layered transition metal carbide or carbonitride nanomaterial with a graphene-like structure, and is generally obtained by etching an element A in precursor MAX phase ceramic (M is an excessive metal element, A is an IIIA or IVA group element, and X is carbon or nitrogen element) through a chemical liquid phase method. Typically, the interlayer spacing of the MXene two-dimensional crystal is 2.0-2.5nm.
The mesoporous molecular sieve is selected from mesoporous silica molecular sieves;
the layered MXene is preferably: ti (Ti) 3 C 2 ，Nb 4 C 3 ，Ta 2 C，Mo 3 C 2 ，Ta 4 C 3 ，Nb 4 C 3 ，Cr 2 C，V 2 C，Nb 2 C, one or more of C.
The preparation method of the modification accelerator comprises the following steps:
(a) Dissolving the accelerator with a solvent, wherein the mass ratio of the accelerator to the solvent is 1:1-10;
(b) Adding a certain amount of frame material into the accelerator solution, wherein the mass ratio of the frame material to the accelerator is 10:2-5, and penetrating the accelerator into the frame material by adopting a mechanical stirring or ultrasonic auxiliary mode. Preferably, the penetration of the accelerator into the frame material is accelerated by ultrasonic treatment equipment with the frequency of 28-100KHz, and the ultrasonic treatment time is 30-90min;
(c) Filtering and drying the mixed solution obtained in the step (2) to obtain the modified accelerator, wherein the drying temperature is preferably 30-40 ℃ and the drying time is 2-4h.
The solvent is a polar solvent including but not limited to ethanol, acetone, glycerol, propylene glycol, water, etc., preferably ethanol and or water.
The accelerator can effectively improve the isocyanate curing reaction rate. After the accelerator permeates micropores or layers of the frame material to form a frame composite structure, the frame material can separate the accelerator from isocyanate, and the isocyanate can not be pre-cured before hot pressing, so that glue loss can be avoided, and the quality of the plate can be ensured.
In some preferred embodiments of the present invention, the isocyanate adhesive in step (1) is sprayed in an amount of 30 to 60g/m 2 ；
The paving mode of the modifying accelerator in the step (2) is one of airflow or diamond roller machinery or vibrating screen paving, and the paving amount is 8-15g/m 2 ；
In the step (3), the veneers obtained in the step (2) are assembled according to the odd-layer principle and the fiber directions of the adjacent veneers are mutually perpendicular;
in the step (4), the slab obtained in the step (3) is hot-pressed at the hot-pressing temperature of 140-160 ℃ under the hot-pressing pressure of 0.3-0.8MPa and the hot-pressing factor of 0.3-0.35min/mm, so that the aldehyde-free plywood is obtained.
If the modification accelerator is mixed with isocyanate for atomization sizing, the atomization effect and sizing uniformity of the isocyanate are affected. Therefore, the two are applied separately. Those skilled in the art understand that in the step (4), the hot pressing is performed in a hot press: the slab is heated and pressurized, mass transfer and heat transfer are carried out in the slab by steam convection, high-temperature and high-pressure steam enters micropores of the frame material or between layers, and the accelerator is dissolved and brought into full contact with isocyanate for rapid catalytic reaction, so that hot press solidification forming is accelerated, and hot press efficiency is remarkably improved. Meanwhile, the isocyanate cured product has high rigidity and low toughness, and the residual frame material in the adhesive layer is beneficial to releasing the internal stress of the adhesive layer and improving the dimensional stability of the plate.
The invention has the beneficial effects that:
(1) The modified accelerator is a composite accelerator with a frame structure, the preparation method is simple, convenient and easy, the porous material or the layered material is used as the frame material, the accelerator is penetrated by ultrasonic assistance, the isolation effect of the frame material before hot pressing can not lead to pre-solidification of isocyanate, and the glue solution loss is avoided; and the accelerator is released during hot pressing, so that the curing of isocyanate is effectively promoted, and the hot pressing production efficiency is improved.
(2) Because the adhesive layer contains porous materials or lamellar materials, the internal stress of the adhesive layer can be effectively released, and the dimensional stability of the plate is improved.
(3) The process route scheme for producing the aldehyde-free plywood provided by the invention has less equipment change and strong feasibility.
The specific embodiment is as follows:
embodiments of the invention are further described below in connection with the examples, but the invention is not limited to the examples set forth and is intended to include any other well known modifications within the scope of the claimed invention.
Polymethylene polyphenyl Polyisocyanates (PMDI): functionality about 2.7, viscosity at 25℃of 180-250cP, -NCO content 30.5-32%, wanhua chemical group Co., ltd;
toluene Diisocyanate (TDI): 2, 4-body content 67+ -2%, 4-body content 33+ -2%, solidifying point 6-8deg.C, viscosity at 25deg.C 3cP, wanhua chemical group Co., ltd;
activated carbon ZZ-300 with particle size of 80 μm and Li Yang Jiangnan activated carbon factory;
Ti 3 C 2 MXnes material with particle size of 75 μm, beijing North New Material science and technology Co., ltd;
Nb 4 C 3 MXnes material with particle size of 150 μm, beijing North Korea New Material science and technology Co., ltd;
mesoporous silica with a particle size of 0.5 μm, jiangsu Xianfeng nano materials science and technology Co., ltd
Triethanolamine, purity > 99%, nanjing kernel chemostat company;
tetramethyl dipropylene triamine, polycat 15, air chemical products Inc.;
tris (dimethylaminopropyl) hexahydrotriazine, polycat 41, air chemical products Inc.;
the purity of the potassium acetate is more than or equal to 98 percent, and the potassium acetate is manufactured by chemical industry Co., ltd in rainy days in Li-yang of Jiangsu province;
n-methylmorpholine, Y-9, chemical industry Co., ltd. In rainy days of Jiangsu province;
dibutyl tin dithiol, dabco T131, american air chemical products company;
the eucalyptus veneer has 15 percent of water content and the thickness of 1.7mm.
Example 1
Preparation of a composite accelerator with a frame structure:
500g of triethanolamine was dissolved in 500g of ethanol; 2500g of Ti was added to the triethanolamine solution 3 C 2 MXnes material, ultrasonic treatment is adopted to promote triethanolamine to Ti 3 C 2 Interlayer infiltration, ultrasonic frequency of 28KHz, and ultrasonic time of 90min; the powder in the mixture was filtered off and dried for 4h at 30 ℃.
Preparation of aldehyde-free plywood:
PMDI was sprayed onto eucalyptus veneer surface by gas atomization at a rate of 60g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The composite accelerator is applied to the surface of a veneer by adopting airflow paving equipment, and the paving amount is 8g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the Assembling the veneers according to the odd-number layer principle and the fiber directions of the adjacent veneers to be mutually perpendicular, wherein the number of the layers of the veneers is 9; and (3) feeding the plate blank into a hot press, wherein the hot pressing temperature is 160 ℃, the hot pressing pressure is 0.8MPa in a high-pressure section, the hot pressing pressure is 0.3MPa in a low-pressure section, the hot pressing factor is 0.3min/mm, and the hot pressing time ratio of the hot pressing pressure high-pressure section to the hot pressing time of the low-pressure section is 3:2, so that the formaldehyde-free plywood is obtained.
And (3) performing I-type plywood performance measurement on the obtained board according to LYT 1738-2020 plywood for solid wood composite floor. The results are shown in Table 1.
Example 2
Preparation of a composite accelerator with a frame structure:
dissolving 50g of N-methylmorpholine in500g of ethanol; 100g of Nb was added to the N-methylmorpholine solution 4 C 3 MXees material, ultrasonic treatment is adopted to promote N-methylmorpholine to Nb 4 C 3 Interlayer infiltration, ultrasonic frequency of 100KHz, and ultrasonic time of 30min; the powder in the mixture was filtered off and dried for 2h at 35 ℃.
Preparation of aldehyde-free plywood:
spraying PMDI and TDI on the surface of eucalyptus veneer by adopting an air atomization mode, wherein the PMDI spraying amount is 30g/m 2 The TDI spraying amount is 10g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The composite accelerator is applied to the surface of a veneer by adopting airflow paving equipment, and the paving amount is 15g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the Assembling the veneers according to the odd-number layer principle and the fiber directions of the adjacent veneers to be mutually perpendicular, wherein the number of the layers of the veneers is 9; and (3) feeding the plate blank into a hot press, wherein the hot pressing temperature is 150 ℃, the hot pressing pressure is 0.8MPa in a high-pressure section, the hot pressing pressure is 0.3MPa in a low-pressure section, the hot pressing factor is 0.32min/mm, and the hot pressing time ratio of the hot pressing pressure high-pressure section to the hot pressing time of the low-pressure section is 3:2, so that the formaldehyde-free plywood is obtained.
The plate performance test method is the same as in example 1. The results are shown in Table 1.
Example 3
Preparation of a composite accelerator with a frame structure:
100g of triethanolamine are dissolved in 500g of ethanol; adding 300g of active carbon ZZ-300 into the triethanolamine solution, and promoting the penetration of the triethanolamine into the micropores of the active carbon by adopting ultrasonic treatment, wherein the ultrasonic frequency is 50KHz, and the ultrasonic time is 60min; the powder in the mixture was filtered off and dried for 3h at 35 ℃. Preparation of aldehyde-free plywood:
PMDI was sprayed onto eucalyptus veneer surface by gas atomization at a rate of 40g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The composite accelerator is applied to the surface of a veneer by adopting diamond roller mechanical paving equipment, and the paving amount is 12g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the Assembling the veneers according to the odd-number layer principle and the fiber directions of the adjacent veneers to be mutually perpendicular, wherein the number of the layers of the veneers is 9; the plate blank is sent into a hot press, the hot pressing temperature is 140 ℃, the hot pressing pressure high-pressure section is 0.8MPa, the hot pressing pressure low-pressure section is 0.3MPa, the hot pressing factor is 0.35min/mm, and the hot pressing time ratio of the hot pressing pressure high-pressure section to the hot pressing time of the hot pressing pressure low-pressure section is 3:2Obtaining the aldehyde-free plywood.
The plate performance test method is the same as in example 1. The results are shown in Table 1.
Example 4
Preparation of a composite accelerator with a frame structure:
100g of potassium acetate are dissolved in 500g of water; adding 300g of mesoporous silica into the potassium acetate solution, and adopting mechanical stirring to promote the potassium acetate to permeate into micropores of the mesoporous silica, wherein the stirring time is 90min; the powder in the mixture was filtered off and dried for 2h at 40 ℃.
Preparation of aldehyde-free plywood:
PMDI was sprayed onto eucalyptus veneer surface by gas atomization at a rate of 40g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The composite accelerator is applied to the surface of a veneer by adopting air flow equipment, and the paving amount is 15g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the Assembling the veneers according to the odd-number layer principle and the fiber directions of the adjacent veneers to be mutually perpendicular, wherein the number of the layers of the veneers is 9; and (3) feeding the plate blank into a hot press, wherein the hot pressing temperature is 140 ℃, the hot pressing pressure is 0.8MPa in a high-pressure section, the hot pressing pressure is 0.3MPa in a low-pressure section, the hot pressing factor is 0.35min/mm, and the hot pressing time ratio of the hot pressing pressure in the high-pressure section to the hot pressing time in the low-pressure section is 3:2, so that the formaldehyde-free plywood is obtained.
The plate performance test method is the same as in example 1. The results are shown in Table 1.
Example 5
Preparation of a composite accelerator with a frame structure:
100g of tris (dimethylaminopropyl) hexahydrotriazine was dissolved in 500g of water; adding 300g of active carbon ZZ-300 into the tris (dimethylaminopropyl) hexahydrotriazine solution, and adopting mechanical stirring to promote the tris (dimethylaminopropyl) hexahydrotriazine to permeate into the micropores of the active carbon, wherein the stirring time is 80min; the powder in the mixture was filtered off and dried for 2h at 40 ℃.
Preparation of aldehyde-free plywood:
PMDI was sprayed onto eucalyptus veneer surface by gas atomization at 50g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The composite accelerator is applied to the surface of a veneer by adopting vibrating screen paving equipment, and the paving amount is 15g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The single board is arranged according to the odd layer principle and adjacent single board fiberThe directions are mutually perpendicular to carry out veneer assembly, and the number of the slab layers is 9; and (3) feeding the plate blank into a hot press, wherein the hot pressing temperature is 140 ℃, the hot pressing pressure is 0.8MPa in a high-pressure section, the hot pressing pressure is 0.3MPa in a low-pressure section, the hot pressing factor is 0.35min/mm, and the hot pressing time ratio of the hot pressing pressure in the high-pressure section to the hot pressing time in the low-pressure section is 3:2, so that the formaldehyde-free plywood is obtained.
The plate performance test method is the same as in example 1. The results are shown in Table 1.
Example 6
Preparation of a composite accelerator with a frame structure:
100g of tetramethyldipropylene triamine were dissolved in 700g of acetone; 400g of active carbon ZZ-300 is added into the tetramethyl dipropylenetriamine solution, mechanical stirring is adopted to promote the penetration of the tetramethyl dipropylenetriamine into the micropores of the active carbon, and the stirring time is 80min; the powder in the mixture was filtered off and dried for 2h at 40 ℃.
Preparation of aldehyde-free plywood:
PMDI was sprayed onto eucalyptus veneer surface by gas atomization at 50g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The composite accelerator is applied to the surface of a veneer by adopting vibrating screen paving equipment, and the paving amount is 13g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the Assembling the veneers according to the odd-number layer principle and the fiber directions of the adjacent veneers to be mutually perpendicular, wherein the number of the layers of the veneers is 9; and (3) feeding the plate blank into a hot press, wherein the hot pressing temperature is 140 ℃, the hot pressing pressure is 0.8MPa in a high-pressure section, the hot pressing pressure is 0.3MPa in a low-pressure section, the hot pressing factor is 0.35min/mm, and the hot pressing time ratio of the hot pressing pressure in the high-pressure section to the hot pressing time in the low-pressure section is 3:2, so that the formaldehyde-free plywood is obtained.
The plate performance test method is the same as in example 1. The results are shown in Table 1.
Example 7
Preparation of a composite accelerator with a frame structure:
100g of dibutyltin dithiol are dissolved in 400g of water; 250g of active carbon ZZ-300 is added into the dibutyltin dithiol solution, mechanical stirring is adopted to promote dibutyltin dithiol to permeate into the micropores of the active carbon, and the stirring time is 80min; the powder in the mixture was filtered off and dried for 2h at 40 ℃.
Preparation of aldehyde-free plywood:
PMDI was sprayed onto eucalyptus veneer surface by gas atomization at 50g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The composite accelerator is applied to the surface of a veneer by adopting vibrating screen paving equipment, and the paving amount is 15g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the Assembling the veneers according to the odd-number layer principle and the fiber directions of the adjacent veneers to be mutually perpendicular, wherein the number of the layers of the veneers is 9; and (3) feeding the plate blank into a hot press, wherein the hot pressing temperature is 140 ℃, the hot pressing pressure is 0.8MPa in a high-pressure section, the hot pressing pressure is 0.3MPa in a low-pressure section, the hot pressing factor is 0.35min/mm, and the hot pressing time ratio of the hot pressing pressure in the high-pressure section to the hot pressing time in the low-pressure section is 3:2, so that the formaldehyde-free plywood is obtained.
The plate performance test method is the same as in example 1. The results are shown in Table 1.
Comparative example 1
PMDI was sprayed only on eucalyptus veneer surface at a rate of 60g/m 2 After assembly, the materials are sent into a hot press, and the hot pressing process is the same as that of example 1.
Board performance test method example 1 is presented. The results are shown in Table 1.
Comparative example 2
PMDI was sprayed only on eucalyptus veneer surface at a rate of 60g/m 2 After assembly, the materials are sent into a hot press, the hot pressing factor is prolonged to 0.5min/mm, and other hot pressing process parameters are the same as those of the embodiment 1.
The plate performance test method is the same as in example 1. The results are shown in Table 1.
Comparative example 3
PMDI was sprayed onto eucalyptus veneer surface at a rate of 60g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the Spraying triethanolamine on the surface of eucalyptus veneer with the spraying amount of 5g/m 2 After assembly, the materials are sent into a hot press, and the parameters of the hot pressing process are the same as those of the embodiment 1.
The plate performance test method is the same as in example 1. The results are shown in Table 1.
Comparative example 4
PMDI was sprayed onto eucalyptus veneer surface at 40g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the After assembly, the blank is sent into a hot press, the hot pressing factor is prolonged to 0.6min/mm, and other hot pressing process parameters are the same as those of the embodiment 3.
Table 1 summary of plywood Performance test results
From the data in the table above, the hot pressing production efficiency of the plywood is remarkably improved by adding the accelerator of the frame structure. The results of example 1 and comparative example 1 show that the promoter hot-pressing factor of PMDI + framework structure can be as low as 0.30min/mm, but that a PMDI-only coated slab cannot be formed at this hot-pressing factor. The results of example 1 and comparative example 2 show that only the PMDI-sprayed slab can be cured and formed only when the hot pressing factor is increased to 0.5min/mm, and that the hot pressing efficiency of example 1 is increased by 40%. The results of example 1 and comparative example 3 show that if triethanolamine as an accelerator is directly paved on the surface of a veneer, the accelerator and isocyanate react in advance before hot pressing, so that the boards cannot be effectively bonded. As can be seen from the comparison of examples 1 and 3 with comparative examples 2 and 4, the dimensional stability of the product after the addition of the framing material is high.
Finally, it should be noted that the above embodiments are only described as preferred embodiments of the present invention, and not limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that various modifications and improvements made to the technical solution of the present invention or equivalent substitutions should be made, all fall within the scope of the present invention as defined in the claims.
Claims (22)
1. A method of producing an aldehyde-free plywood, comprising the steps of:
(1) Spraying isocyanate adhesive on the surface of the wood veneer;
(2) Paving a modification accelerator on the surface of the wood veneer obtained in the step (1);
(3) Assembling veneers;
(4) Hot-press molding of the plate;
the modified accelerator is a composite accelerator with a framework structure and comprises a framework material and an accelerator, wherein the framework material is a porous material or a layered material, and the accelerator is selected from a water-soluble amine catalyst and/or an organic metal catalyst.
2. The method of claim 1, wherein the wood veneer is one or more of poplar, eucalyptus, pine, birch, basswood, begonia, lotus, maple, elm, fir, oak or rubber wood having a moisture content of 10wt% to 25wt%.
3. The method of claim 2, wherein the wood veneer has a moisture content of 13wt% to 17wt%.
4. The method according to claim 1, wherein the isocyanate is an aromatic polyisocyanate, an aliphatic polyisocyanate or a modified isocyanate thereof.
5. The method of claim 4, wherein the isocyanate is an aromatic polyisocyanate.
6. The method of claim 5, wherein the isocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, and polymethylene polyphenyl polyisocyanates.
7. The method of claim 4, wherein the isocyanate is a modified isocyanate including, but not limited to, polyether modified or polyester modified.
8. The method of claim 1 wherein the isocyanate is the isocyanate adhesive having an NCO content of 20 to 34wt%.
9. The method of claim 1, wherein the framework material is activated carbon, mesoporous molecular sieve, or layered MXene.
10. The method of claim 1, wherein the framing material has a particle size of 0.5 to 150 μm.
11. The method of claim 1, wherein the accelerator comprises, but is not limited to, monoethanolamine, diethanolamine, triethanolamine, dimethylethanolamine, bis (dimethylaminoethyl) ether, pentamethyldialkylenetriamine, tetramethylalkylenediamine, 2,4, 6-tris (dimethylaminomethyl) phenol, tris (dimethylaminopropyl) hexahydrotriazine, dimethylaminoethoxyethanol, trimethylhydroxyethyl propylenediamine, trimethylhydroxyethyl ethylenediamine, dimethylaminopropylamine diisopropylalcohol, tetramethyldipropylenetriamine, N-methylmorpholine, N-ethylmorpholine, dimorpholine diethyl ether, dimorpholine triethyl ether, N- (dimethylaminoethyl) morpholine, diazabicyclo, potassium carboxylate, dibutyltin dithiol.
12. The method of claim 11, wherein the promoter is an alcohol amine and/or potassium carboxylate.
13. The method of claim 9, wherein the mesoporous molecular sieve is selected from the group consisting of mesoporous silica molecular sieves;
the layered MXene is as follows: ti (Ti) 3 C 2 ，Nb 4 C 3 ，Ta 2 C，Mo 3 C 2 ，Ta 4 C 3 ，Nb 4 C 3 ，Cr 2 C，V 2 C，Nb 2 C, one or more of C.
14. The method according to claim 1, wherein the preparation method of the modification promoter comprises the following steps:
(a) Dissolving the accelerator with a solvent, wherein the mass ratio of the accelerator to the solvent is 1:1-10;
(b) Adding a certain amount of frame material into the accelerator solution, wherein the mass ratio of the frame material to the accelerator is 10:2-5, and penetrating the accelerator into the frame material by adopting a mechanical stirring or ultrasonic auxiliary mode;
(c) And (3) filtering and drying the mixed solution obtained in the step (b) to obtain the modified accelerator.
15. The method of claim 14, wherein the solvent is a polar solvent including, but not limited to, ethanol, acetone, glycerol, propylene glycol, water.
16. The method of claim 14, wherein the solvent is ethanol and or water.
17. The method of claim 14, wherein in step (b), the penetration of the accelerator into the framing material is accelerated using a sonication device having a frequency of 28-100KHz for 30-90 minutes.
18. The method of claim 14, wherein in step (c), the drying temperature is 30-40 ℃ and the drying time is 2-4 hours.
19. The method according to claim 1, wherein the isocyanate adhesive in step (1) is sprayed in an amount of 30 to 60g/m 2 。
20. The method according to claim 1, wherein the modifying accelerator in the step (2) is applied by one of air flow, diamond roller machine or vibrating screen, and the application amount is 8-15g/m 2 。
21. The method according to any one of claims 1 to 14, wherein in the step (3), the veneers obtained in the step (2) are assembled according to an odd-numbered layer principle and the fiber directions of adjacent veneers are perpendicular to each other.
22. The method according to any one of claims 1 to 14, wherein in the step (4), the slab obtained in the step (3) is hot-pressed at a hot-pressing temperature of 140 to 160 ℃, a hot-pressing pressure of 0.3 to 0.8MPa, and a hot-pressing factor of 0.3 to 0.35min/mm.
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