Flame-retardant thermoplastic resin plywood base material and manufacturing method thereof

Abstract

The invention relates to a flame-retardant thermoplastic resin plywood base material and a manufacturing method thereof, and belongs to the technical field of thermoplastic resin plywood manufacturing. The plywood base material is composed of flame-retardant wood veneers and thermoplastic resin film layers or composed of flame-retardant wood veneers, wood veneers and thermoplastic resin film layers, the number of the flame-retardant wood veneers and the number of the wood veneers are an odd number of more than three, at least two layers of the outermost sides of the upper surface and the lower surface are the flame-retardant wood veneers, the middle layer is the flame-retardant wood veneer and / or the wood veneer, and the thermoplastic resin film layers are arranged between the flame-retardant wood veneers and the wood veneers. The wood texture directions of two adjacent layers of veneers are perpendicular to each other, and a thermoplastic resin film layer is laid between the two adjacent layers of veneers; the flame-retardant wood veneer is subjected to dipping treatment by adopting a flame retardant solution composed of a flame retardant and a smoke suppression synergist. The invention further discloses a production and manufacturing process. The prepared product is free of formaldehyde addition and has excellent flame retardant and smoke suppression performance, and the application scene requirements of thermoplastic resin plywood in narrow and closed spaces such as high-speed rail carriages, ship cabins and indoor public places are met.

Description

Technical Field

[0001] The present invention relates to a flame retardant formaldehyde-free plywood production technology, specifically to a flame retardant thermoplastic resin plywood substrate production process scheme, especially to a flame retardant thermoplastic resin plywood substrate and a production method thereof, belonging to the thermoplastic resin plywood production technology field. Background Art

[0002] Plywood is a wood composite material with excellent comprehensive performance. It is easy to process, functionalized, and has high specific strength. It is widely used in interior decoration, furniture manufacturing, building formwork, packaging materials and other fields. Traditional plywood adhesives are mainly formaldehyde-containing adhesives, and the products are easy to release free formaldehyde, which is harmful to human health. Especially in special small and closed spaces such as high-speed rail carriages, ship cabins, and indoor public places, comprehensive requirements are put forward for the formaldehyde and other TVOC release limits and fire safety of plywood products.

[0003] At present, the thermoplastic resin without formaldehyde addition, polyethylene (PE) film, can replace the traditional formaldehyde-containing adhesive as the adhesive layer of plywood. Through the melt flow of PE on the surface of the veneer during the hot pressing process, it forms a glue nail effect between the wood veneer, so that through reasonable assembly and hot pressing process design, the formaldehyde-free thermoplastic resin plywood substrate with excellent physical and mechanical properties can be successfully prepared, solving the problem of TVOC and free formaldehyde release of plywood products from the root. The feasibility of preparing a new type of thermoplastic resin plywood without formaldehyde addition using PE as the adhesive layer has been verified by systematic experiments. However, the interface compatibility between PE and wood is poor, especially after the wood veneer is flame-retardant treated, the bonding performance between the flame-retardant veneer and PE will be further reduced. Therefore, designing a flame-retardant and smoke-suppressing formula suitable for the thermoplastic resin plywood bonding system and combining it with a suitable thermoplastic resin plywood production process is the technical key to preparing flame-retardant thermoplastic resin plywood with excellent performance.

[0004] Most of the conventional flame-retardant plywood products on the market cannot meet the use requirements and relevant standards of small and enclosed public spaces in terms of both flame retardancy and environmental protection performance. Based on this, on the basis of thermoplastic resin plywood products without formaldehyde addition, through the formulation design of flame retardants and smoke suppression synergists for wood veneer impregnation, and the optimization of flame retardant treatment process, thermoplastic resin plywood products with excellent flame retardancy and smoke suppression performance are prepared, which can enable thermoplastic resin plywood to be used in shipping ships, rail transit, indoor public places and other spaces with high environmental requirements, effectively expanding the application scenarios of plywood products. Summary of the invention

[0005] The present invention provides a manufacturing process scheme for a flame-retardant thermoplastic resin plywood substrate without formaldehyde addition, which can effectively improve the flame retardancy and smoke suppression performance of the thermoplastic resin plywood substrate, and form a supporting production and manufacturing technology for flame-retardant thermoplastic resin plywood products with excellent flame retardancy, environmental protection and mechanical properties.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A flame-retardant thermoplastic resin plywood substrate is composed of flame-retardant wood veneers and a thermoplastic resin film layer, or composed of flame-retardant wood veneers, wood veneers and a thermoplastic resin film layer. The sum of the number of the flame-retardant wood veneers and the wood veneers is an odd number of 3 layers or more. At least two outermost layers on the upper and lower surfaces of the substrate are flame-retardant wood veneers, and the middle layer is flame-retardant wood veneers and / or wood veneers. The wood grain directions of two adjacent veneers are perpendicular to each other, and a thermoplastic resin film layer is laid between two adjacent veneers; the flame-retardant wood veneer is a wood veneer impregnated and treated with a two-component smoke suppression synergistic flame retardant solution; the two-component smoke suppression synergistic flame retardant is composed of a flame retardant and a smoke suppression synergist.

[0008] In the two-component smoke suppression synergistic flame retardant, the mass ratio of the smoke suppression synergist to the flame retardant is 1:2 - 1:10; the flame retardant is ammonium polyphosphate (APP); the smoke suppression synergist is any one of sodium molybdate (MN), sodium tetraborate decahydrate (St) and sodium ethylene diamine tetra (methylene phosphonate) pentasodium (S2).

[0009] In the two-component smoke suppression synergistic flame retardant solution, the concentration of the flame retardant is 5wt.% - 20wt.%.

[0010] All of the flame-retardant wood veneers are impregnated and treated with the two-component smoke suppression synergistic flame retardant; the moisture content level of the flame-retardant wood veneer is 8% - 16% (wt.%).

[0011] The tree species of the wood veneer is any one of poplar, eucalyptus, birch, fir and pine; the thickness of the wood veneer is 0.2 - 5mm; the moisture content level of the wood veneer is 8% - 16% (wt.); the material of the thermoplastic resin film is maleic anhydride grafted polyethylene (MAH-g-PE); the thickness of the thermoplastic resin film is 0.02 - 0.20mm. After the flame-retardant wood veneers and the thermoplastic resin film layer are assembled into a blank, they are formed by hot pressing and cold pressing.

[0012] A manufacturing method for a flame-retardant thermoplastic resin plywood substrate is a production and manufacturing method for a flame-retardant thermoplastic resin plywood substrate without formaldehyde addition, and includes the following steps:

[0013] (1) Weigh the flame retardant and the smoke suppression synergist, add an appropriate amount of water, stir to completely dissolve the flame retardant and the smoke suppression synergist in water, and let it stand to prepare a two-component smoke suppression synergistic flame retardant solution.

[0014] (2) Immerse the wood veneer dried to an appropriate moisture content level into the two-component smoke suppression synergistic flame retardant solution prepared in step (1) for impregnation treatment.

[0015] (3) Take out the wood veneer that has completed the impregnation treatment in step (2), drain it, and control it to reach an appropriate moisture content level to obtain a flame retardant wood veneer for plywood manufacturing.

[0016] (4) Assemble the wood veneer modified in step (3) and the thermoplastic resin film, hot press the board blank, and cold press it into shape to obtain a formaldehyde-free flame retardant thermoplastic resin plywood substrate.

[0017] In step (1), the flame retardant is ammonium polyphosphate (APP), the smoke suppression synergist is any one of sodium molybdate (MN), sodium tetraborate decahydrate (St), and sodium ethylene diamine tetra (methylene phosphonic acid) pentasodium (S2). In the flame retardant solution, the concentration of the flame retardant is 5wt.% - 30wt.%, and the mass ratio of the addition amount of the smoke suppression synergist to the addition amount of the flame retardant is 1:2 - 1:10.

[0018] In step (2), the tree species of the wood veneer is any one of poplar, eucalyptus, birch, fir, and pine; the thickness of the wood veneer is 0.2 - 5mm; the moisture content level of the wood veneer is 8% - 16% (wt.%). The impregnation treatment is any one of vacuum pressure impregnation or normal temperature and pressure impregnation; for the impregnation treatment, the veneer needs to be completely immersed 20mm below the liquid level; the vacuum pressure impregnation pressure is 0.5 - 1.0MPa, and the impregnation duration is 30min - 2h; the normal temperature and pressure impregnation duration is 5 - 12h.

[0019] In step (3), the moisture content level of the flame retardant wood veneer is 8% - 16% (wt.%).

[0020] In step (4), the material of the thermoplastic resin film is maleic anhydride grafted polyethylene (MAH-g-PE); the thickness of the thermoplastic resin film is 0.02 - 0.20mm.

[0021] In step (4), the assembly method is: stack the flame retardant wood veneer modified in step (3) and the thermoplastic resin film layer by layer, with the grain directions of adjacent flame retardant wood veneers perpendicular to each other, and a thermoplastic resin film layer is laid between adjacent two veneers. The number of veneer layers is an odd number of 3 layers or more.

[0022] In step (4), the process for preparing the thermoplastic resin plywood substrate from the slab is as follows: the hot pressing temperature is 140°C - 180°C, the hot pressing pressure is 0.6 - 2.2 MPa, preferably 0.8 - 1.2 MPa, and the hot pressing time is 40 - 120 s / mm; the cold pressing pressure is 0.3 - 1.8 MPa, preferably 0.5 - 1.0 MPa, and the cold pressing time is 20 - 80 s / mm.

[0023] According to the production and manufacturing technology of the formaldehyde - free flame - retardant thermoplastic resin plywood substrate of the present invention, the following beneficial effects can be achieved through experimental verification:

[0024] The two - component synergistic smoke - suppressing and flame - retardant agent introduced by impregnation into the wood veneer can effectively improve the flame - retardant performance of the thermoplastic resin plywood, inhibit the release of toxic gases and fumes, and has excellent flame - retardant and smoke - suppressing effects on both the wood veneer and the thermoplastic resin bonding layer. It can form a flame - retardant protective carbon layer on the surface of the thermoplastic resin plywood and release flame - suppressing gases to play a purging role. The flame - retardant performance of the prepared plywood substrate is tested, and the best can reach: the oxygen index is 35.8%, the combustion rating is Class A, the 45° combustion rating is difficult - to - burn, and the D s1.5 、D s4 smoke densities are 5 and 8 respectively. The amount of smoke generated by the combustion of the plywood product is small, showing excellent flame - retardant and smoke - suppressing performance.

[0025] In addition, through the coordination and optimization of the flame - retardant veneer and the formaldehyde - free thermoplastic resin bonding layer, while achieving excellent flame - retardant and smoke - suppressing effects of the plywood, it can ensure the high - strength bonding between the flame - retardant veneer and the thermoplastic resin, ensuring excellent bonding strength of the board. The Class I bonding strength of the flame - retardant thermoplastic resin plywood prepared with eucalyptus veneer can reach a maximum of 1.81 MPa, and the average wood failure rate is 98%. The introduction of the flame - retardant does not have an adverse effect on the bonding performance of the board. In the detection of toxic gases in the board, the CO and CO2 releases are 73 mg / m 3 、5797 mg / m 3 ; the formaldehyde release amount detected by a 1 m 3 climate chamber is 0.02 mg / m 3 , reaching the E NF grade in the national standard (GB / T39600 - 2021), showing excellent environmental performance. Specific implementation examples

[0026] A flame-retardant thermoplastic resin plywood substrate of the present invention is composed of flame-retardant wood veneers and a thermoplastic resin film layer. The number of flame-retardant wood veneers is an odd number of 3 layers or more, and the grain directions of adjacent flame-retardant wood veneers are perpendicular to each other. A thermoplastic resin film layer is laid between adjacent two veneers; the flame-retardant wood veneer is a wood veneer impregnated and treated with a two-component smoke-suppressing synergistic flame retardant solution; the two-component smoke-suppressing synergistic flame retardant is composed of a flame retardant and a smoke-suppressing synergist.

[0027] Another flame-retardant thermoplastic resin plywood substrate of the present invention is composed of flame-retardant wood veneers, wood veneers and a thermoplastic resin film layer. The sum of the number of flame-retardant wood veneers and wood veneers is an odd number of 3 layers, 5 layers or more. At least two outermost layers on the upper and lower surfaces of the substrate are flame-retardant wood veneers, and at least one layer or all of the middle layers are wood veneers. The wood grain directions of adjacent two veneers are perpendicular to each other. A thermoplastic resin film layer is laid between adjacent two veneers; the flame-retardant wood veneer is a wood veneer impregnated and treated with a two-component smoke-suppressing synergistic flame retardant solution; the two-component smoke-suppressing synergistic flame retardant is composed of a flame retardant and a smoke-suppressing synergist.

[0028] The manufacturing method of the flame-retardant thermoplastic resin plywood substrate of the present invention includes the following steps:

[0029] (1) Flame retardant preparation: Weigh a certain amount of flame retardant and smoke-suppressing synergist. The mass ratio of the flame retardant to the synergist is 2:1 - 10:1. Using water as the solvent, stir evenly until completely dissolved to prepare a two-component flame retardant solution with a flame retardant concentration of 5wt.% - 20wt.%.

[0030] The flame retardant is ammonium polyphosphate (APP), and the smoke-suppressing synergist is any one of sodium molybdate (MN), sodium tetraborate decahydrate (St) or sodium ethylene diamine tetra (methylene phosphonic acid) pentasodium (S2). In the flame retardant solution, the concentration of APP is 5wt.% - 20wt.%, and the mass ratio of the addition amount of the smoke-suppressing synergist to the addition amount of APP is 1:2 - 1:10.

[0031] (2) Flame retardant treatment of wood veneers: The impregnation treatment is any one of vacuum pressure impregnation or normal temperature and pressure impregnation; dry the wood veneer with a thickness of 0.2 - 5mm to a moisture content level of 8% - 16%. Immerse all the veneers into the two-component flame retardant solution, and immerse them 20mm below the liquid surface. Place the impregnation tank into a vacuum pressure impregnation tank, and under a pressure of 0.5 - 1MPa, carry out vacuum pressure impregnation for 30min - 2h; or place the impregnation tank in a normal temperature and pressure environment and impregnate for 5 - 12h. Take out the impregnated wood veneers, drain, and dry to a moisture content level of 8% - 16% to obtain flame-retardant wood veneers for plywood manufacturing.

[0032] The tree species of the wood veneer include any one of poplar, eucalyptus, birch, Chinese fir and pine; the thickness of the wood veneer is 0.2 - 5 mm; the moisture content level is 8% - 16%; the material of the thermoplastic resin film is maleic anhydride grafted polyethylene (MAH-g-PE); the thickness of the thermoplastic resin film is 0.02 - 0.20 mm.

[0033] (3) Preparation of flame-retardant thermoplastic resin plywood substrate: Assemble the flame-retardant wood veneer and the thermoplastic resin film; when assembling, the thermoplastic resin film is laid between two veneers. The process for preparing the thermoplastic resin plywood substrate is as follows: when assembling, the number of flame-retardant wood veneers is an odd number of 3 layers or more, the wood grain directions of adjacent veneers are perpendicular to each other, and a thermoplastic resin film layer is laid between two adjacent veneers.

[0034] The formed board blank is sent into a flat hot press and hot-pressed under the conditions of a hot-pressing temperature of 140°C - 180°C, a hot-pressing pressure of 0.6 - 2.2 MPa, and a hot-pressing time of 40 - 120 s / mm; after hot-pressing, the board blank is immediately transferred to a cold press for cold-pressing and curing treatment, the cold-pressing pressure is 0.3 - 1.8 MPa, and the cold-pressing time is 20 - 80 s / mm; then the pressed board is trimmed and stored to obtain the flame-retardant thermoplastic resin plywood substrate.

[0035] The formaldehyde-free flame-retardant thermoplastic resin plywood substrate prepared by the above method includes at least 3 layers of overlapping and composite wood veneers, and MAH-g-PE adhesive layers for bonding located between adjacent veneers; the adhesive layers are thermoplastic resin films; all the wood veneers are impregnated with the two-component smoke suppression synergistic flame retardant at normal temperature and pressure or by vacuum pressure impregnation.

[0036] Example 1

[0037] A method for manufacturing a flame-retardant thermoplastic resin plywood substrate, the steps are as follows:

[0038] (1) Preparation of flame retardant: Weigh a certain amount of flame retardant ammonium polyphosphate APP and smoke suppression synergist sodium tetraborate decahydrate St, the mass ratio of the flame retardant to the synergist is 3:1, use water as the solvent, stir evenly until completely dissolved, and prepare a two-component flame retardant solution with a flame retardant concentration of 15 wt.%.

[0039] (2) Flame retardant treatment of wood veneer: Dry the eucalyptus veneer with a thickness of 1.7 mm to a moisture content level of 12 wt.%, immerse all the veneers in the two-component flame retardant solution, immerse them 20 mm below the liquid surface, then put the impregnation tank into a vacuum pressure impregnation tank, under a pressure of 1 MPa, carry out vacuum pressure impregnation for 2 h, drain, and dry to a moisture content level of 8 wt.% - 10 wt.% to obtain the flame-retardant wood veneer for plywood manufacturing.

[0040] (3) Preparation of flame-retardant thermoplastic resin plywood substrate: Assemble the flame-retardant wood veneer and the MAH-g-PE adhesive film with a thickness of 0.08 mm. Lay the two layers of veneer with perpendicular textures, and lay the thermoplastic resin adhesive film between the veneers to form a board blank with 7 layers of veneer; Feed the formed board blank into a flat hot press and perform hot pressing under the conditions of a hot pressing temperature of 160 °C, a hot pressing pressure of 1 MPa, and a hot pressing time of 60 s / mm; After the hot pressing is completed, immediately transfer the board blank to a cold press for cold pressing and curing treatment. The cold pressing pressure is 1 MPa, and the cold pressing time is 30 s / mm; Subsequently, trim and store the pressed board to obtain the flame-retardant thermoplastic resin plywood substrate.

[0041] Example 2

[0042] Others are the same as in Example 1, except that in step (1), the smoke suppression synergist in Example 1 is changed to sodium molybdate MN.

[0043] Example 3

[0044] Others are the same as in Example 1, except that in step (1), the smoke suppression synergist in Example 1 is changed to sodium ethylene diamine tetra methylene phosphonate S2.

[0045] Example 4

[0046] Others are the same as in Example 1, except that in step (2), the vacuum pressure impregnation in Example 1 is changed to normal temperature and pressure impregnation for 5 h.

[0047] Example 5

[0048] Others are the same as in Example 1, except that in step (1), the concentration of the flame retardant in Example 1 is changed to 5 wt.%, and the mass ratio of the flame retardant APP to the smoke suppression synergist St is still 3:1; In step (2), the vacuum pressure impregnation in Example 1 is changed to normal temperature and pressure impregnation for 5 h.

[0049] Example 6

[0050] Others are the same as in Example 1, except that in step (1), the concentration of the flame retardant in Example 1 is changed to 10 wt.%, and the mass ratio of the flame retardant APP to the smoke suppression synergist St is still 3:1. In step (2), the vacuum pressure impregnation in Example 1 is changed to normal temperature and pressure impregnation for 5 h.

[0051] Example 7

[0052] Others are the same as in Example 1, except that in step (1), the concentration of the flame retardant in Example 1 is changed to 20 wt.%, and the mass ratio of the flame retardant APP to the smoke suppression synergist St is still 3:1. In step (2), the vacuum pressure impregnation in Example 1 is changed to normal temperature and pressure impregnation for 5 h.

[0053] Comparative Example 1

[0054] Others are the same as in Example 1, except that: in step (1), no smoke suppression synergist component is added.

[0055] Comparative Example 2

[0056] Others are the same as in Example 1, except that: the veneer is not flame-retarded.

[0057] Comparative Example 3

[0058] Others are the same as in Example 1, except that: a PE film with the same thickness is used to replace MAH-g-PE.

[0059] Comparative Example 4

[0060] Others are the same as in Example 1, except that: a PE film with the same thickness is used to replace MAH-g-PE, and the veneer is not flame-retarded.

[0061] For the flame-retardant thermoplastic resin plywood substrates prepared in the above examples and comparative examples, their bonding strength was tested according to the following standards:

[0062] 1. GB / T 17657—2013. Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels [S]. Beijing: China Standards Press, 2013.

[0063] 2. GB / T 9846-2015. General Plywood [S]. Beijing: China Standards Press, 2015.

[0064] The test of the bonding strength was carried out according to the regulations for Class I bonding strength test: impregnated in boiling water for 4 h, then dried in a forced-air drying oven at (60 ± 3) °C for 16 h to 20 h, then impregnated in boiling water for 4 h, and then placed in cold water at a temperature below 30 °C for at least 1 h.

[0065] For the flame-retardant thermoplastic resin plywood substrates prepared in the above examples and comparative examples, their flame retardancy was tested according to the following standards:

[0066] Oxygen index test: The determination of the oxygen index was carried out in accordance with the national standard GB / T 2406.2-2009 "Test Method for Flammability of Plastics - Oxygen Index Method". The flame-retardant plywood was sawn into specimens of 100 mm × 10 mm × 3 mm and vertically fixed in the combustion cylinder, so that the oxygen-nitrogen mixed gas flow passed upward from the bottom, the top of the specimen was ignited, and at the same time the time was recorded and the combustion length of the specimen was observed, and compared with the specified criteria. A group of specimens was tested at different oxygen concentrations, and the lowest oxygen concentration at which the specimen just maintained stable combustion was measured, expressed as the volume percentage % of the oxygen content in the mixed gas. Each group of flame-retardant specimens had 10 replicates.

[0067] Smoke density test: The smoke density test is based on the standard GB / T 8323.2-2008 (equivalent to ISO

[0068] 5659-2:2006). The optical density of the smoke generated during the combustion of the material under a certain radiant ignition condition is measured. The specimen size is 75mm×75mm×≤25mm. The actual combustion surface of the sample is the fire-exposed surface, and the other surfaces are wrapped with aluminum foil with the dark side facing outwards and placed in a specific tooling box. The tooling box is placed horizontally on a bench with a platform scale. At 25mm above the sample surface is a horizontal radiation cone, and the heat flux is 25kW / m 2 , and the test generally lasts for 10 min or longer. The arithmetic mean value is taken from 3 tests. The performance data of the flame-retardant thermoplastic resin plywood substrate are listed in Table 1.

[0069] Table 1 Test results of various properties of the flame-retardant thermoplastic resin plywood substrate

[0070]

[0071] a The addition amount of the smoke suppression synergist is one-third of the addition amount of the flame retardant.

[0072] b The vacuum pressure impregnation pressure is 1 MPa, and the treatment time is 2 h; the normal temperature and pressure impregnation time is 5 h.

[0073] Through systematic experimental screening of the flame retardant and smoke suppression synergist formulations for wood veneer impregnation, the flame retardant treatment process, and the modification scheme of the thermoplastic resin adhesive film, the above representative and practical implementation cases were obtained, and their bonding strength, flame retardant, and smoke suppression properties were tested. The test results show that maleic anhydride graft modification has an obvious enhancing effect on the bonding performance between the thermoplastic resin PE film and the wood veneer, increasing the bonding strength of ordinary thermoplastic resin plywood and flame retardant thermoplastic resin plywood from 0.78 MPa (Comparative Example 4) and 0.67 MPa (Comparative Example 3) to 1.18 MPa (Example 4) and 1.87 MPa (Comparative Example 2), respectively. The types and ratios of the above preferred flame retardants and smoke suppression synergists do not have an adverse effect on the bonding strength of thermoplastic resin plywood, and the bonding strength of all flame retardant thermoplastic resin plywood is much greater than the national standard requirement of 0.7 MPa. In addition, the introduction of the two-component smoke suppression synergist flame retardant increases the limiting oxygen index of the thermoplastic resin plywood from 24.6% (Comparative Example 2) to a maximum of 56.8% (Example 1), and reduces the smoke density value from 83.0 (Comparative Example 2) to a minimum of 4.0 (Example 1), proving that the addition of the flame retardant has a very obvious effect on the flame retardant and smoke suppression of the board during combustion. When comparing the properties of flame retardant thermoplastic resin plywood treated by vacuum pressure impregnation and normal temperature and atmospheric pressure impregnation, it was found that due to the difference in the flame retardant loading, vacuum pressure impregnation treatment has obvious benefits for improving the flame retardant and smoke suppression properties of the board. However, the key data of the flame retardant and smoke suppression properties such as the oxygen index and smoke density of the board prepared by normal temperature and atmospheric pressure impregnation treatment have reached the industry standard (TB / T 3237) of the flame retardant technical conditions for interior materials of EMUs in the Chinese railway industry, with the oxygen index ≥ 30% and the smoke density of non-flaming combustion DS 1.5 ≤ 100, DS4 ≤ 200, meeting the application requirements and significantly reducing production costs and process technical difficulties. This standard has strict performance index requirements for the interior materials of the closed and narrow EMU train carriages, indicating that the flame retardant plywood substrate produced by the present invention has excellent flame retardant and smoke suppression characteristics and can be applied to special fields such as rail transit.

[0074] The toxicity gas, formaldehyde release amount and other indicators of the flame retardant thermoplastic resin plywood substrate finished product prepared in Example 4 were tested, and the test results are listed in Table 2 with reference to the requirements of the Chinese railway industry standard.

[0075] Table 2 Detection Results of Toxicity Gas and Formaldehyde Release Amount of Flame Retardant Thermoplastic Resin Plywood Substrate

[0076]

[0077]

[0078] Note: The above data comes from a third-party testing agency with CNAS qualification

[0079] The test results show that CO and CO2 are 73mg / m 3 5797mg / m 3 Far below the standard of 4000mg / m 3 、<90000mg / m 3 , HF, HBr, HCl, NO x The detection values of harmful gases such as SO2 and HCN are extremely small or not detected, indicating that the flame retardant selected by the present invention is safe, environmentally friendly, halogen-free, and has little harm to the human body. The formaldehyde emission detection value of the board is 0.02mg / m 3 , relative standard value 0.1mg / m 3 Reduced by 400%, reaching the optimal level E in the national standard (GB / T39600-2021) for the environmental protection grade of artificial boards NF The product can be used in public areas such as auditoriums, conference rooms, kindergartens, hospitals, nursing homes, etc., which have high requirements on flame retardancy and environmental protection level of materials, as well as confined spaces such as rail transit, cars, ships, etc., which can effectively improve the living environment and protect people's health.

[0080] The flame-retardant thermoplastic resin plywood manufacturing process of the present invention comprises the following steps: preparing a two-component synergistic flame retardant according to a certain ratio; impregnating the surface of a wood veneer with the two-component synergistic flame retardant, and drying at room temperature to form a flame-retardant veneer; assembling the flame-retardant veneer and the thermoplastic resin film, hot pressing the slabs, and cold pressing to obtain a flame-retardant thermoplastic resin plywood without formaldehyde addition. The present invention prepares a thermoplastic resin plywood product without formaldehyde addition and having excellent flame retardant and smoke suppression properties through a two-component synergistic flame retardant formula for impregnating wood veneers and a flame retardant treatment process design, which meets the application scenario requirements of thermoplastic resin plywood in small enclosed spaces such as high-speed rail carriages, ship cabins, and indoor public places.

[0081] The above descriptions are merely embodiments of the present invention and are not intended to limit the technical solutions of the present invention. Any modifications or equivalent substitutions made using the contents of the present invention specification, as well as direct or indirect application to the technical fields of other related products, are also covered by the patent protection scope of the present invention.

Claims

1. A flame-retardant thermoplastic resin plywood substrate, characterized in that: It is composed of a flame-retardant wood veneer and a thermoplastic resin film layer, or composed of a flame-retardant wood veneer, a wood veneer and a thermoplastic resin film layer. The sum of the number of the flame-retardant wood veneers and the wood veneers is an odd number of 3 layers or more. At least two outermost layers on the upper and lower surfaces of the substrate are flame-retardant wood veneers, and the middle layer is a flame-retardant wood veneer and / or a wood veneer. The wood grain directions of adjacent two veneers are perpendicular to each other, and a thermoplastic resin film layer is laid between adjacent two veneers; the flame-retardant wood veneer is a wood veneer impregnated and treated with a two-component smoke suppression synergistic flame retardant solution; the two-component smoke suppression synergistic flame retardant is composed of a flame retardant and a smoke suppression synergist.

2. The flame-retardant thermoplastic resin plywood substrate according to claim 1, characterized in that: The mass ratio of the smoke suppression synergist to the flame retardant is 1:2 - 1:10; the flame retardant is ammonium polyphosphate; the smoke suppression synergist is any one of sodium molybdate, sodium tetraborate decahydrate and sodium ethylene diamine tetra(methylene phosphonate).

3. The flame-retardant thermoplastic resin plywood substrate according to claim 1, wherein: All of the flame-retardant wood veneers are impregnated and treated with the two-component smoke suppression synergistic flame retardant; the moisture content of the flame-retardant wood veneer is 8wt.% - 16wt.%.

4. The flame-retardant thermoplastic resin plywood substrate according to claim 1, characterized in that: The wood veneer is any one of poplar, eucalyptus, birch, Chinese fir and pine; the thickness of the wood veneer is 0.2 - 5mm; the moisture content of the wood veneer is 8wt.% - 16wt.%.

5. The flame-retardant thermoplastic resin plywood substrate according to claim 1, wherein: The material of the thermoplastic resin film is maleic anhydride grafted modified polyethylene; the thickness of the thermoplastic resin film is 0.02 - 0.20mm.

6. The manufacturing method of the flame-retardant thermoplastic resin plywood substrate according to any one of claims 1 - 5, comprising the following steps: (1) Weigh the flame retardant and the smoke suppression synergist, add an appropriate amount of water, stir, and let the flame retardant and the smoke suppression synergist completely dissolve in water and stand still to prepare a two-component smoke suppression synergistic flame retardant solution; (2) Immerse the wood veneer dried to an appropriate moisture content level into the two-component smoke suppression synergistic flame retardant solution prepared in step (1) for impregnation treatment; (3) Take out the wood veneer that has completed the impregnation treatment in step (2), drain it, and control to reach an appropriate moisture content level to obtain a flame-retardant wood veneer for plywood manufacturing; (4) Group the wood veneer modified in step (3) and the thermoplastic resin film, and perform hot pressing and cold pressing molding on the board blank to obtain a formaldehyde-free flame-retardant thermoplastic resin plywood substrate.

7. The manufacturing method of the flame-retardant thermoplastic resin plywood substrate according to claim 6, characterized in that: In the two-component smoke suppression synergistic flame retardant solution, the concentration of the flame retardant is 5wt.% - 30wt.%.

8. The manufacturing method of the flame-retardant thermoplastic resin plywood substrate according to claim 6, characterized in that: The impregnation treatment is vacuum pressure impregnation or normal temperature and pressure impregnation; in the impregnation treatment, the veneer is completely immersed 20mm below the liquid level; the vacuum pressure impregnation pressure is 0.5 - 1.0MPa, and the impregnation duration is 30min - 2h; the normal temperature and pressure impregnation duration is 5 - 12h.

9. The manufacturing method of the flame-retardant thermoplastic resin plywood substrate according to claim 6, characterized in that: The grouping method is: stack the flame-retardant wood veneers and the thermoplastic resin film layers layer by layer. The grain directions of adjacent flame-retardant wood veneers are perpendicular to each other, and a thermoplastic resin film layer is laid between adjacent two veneers. The number of veneer layers is an odd number of 3 layers or more.

10. The manufacturing method of the flame-retardant thermoplastic resin plywood substrate according to claim 6, characterized in that: The process for preparing a thermoplastic resin plywood substrate from a slab is as follows: the hot pressing temperature is 140°C - 180°C, the hot pressing pressure is 0.6 - 2.2 MPa, and the hot pressing time is 40 - 120 s / mm; the cold pressing pressure is 0.3 - 1.8 MPa, and the cold pressing time is 20 - 80 s / mm.

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