Compound flame retardant powder for wood adhesives, flame retardant wood adhesives using it, and flame-retardant plywood.

Abstract

This invention discloses a compound flame-retardant powder for wood adhesives, a flame-retardant wood adhesive using the same, and flame-retardant plywood. The compound flame-retardant powder is composed of flake-like hexagonal magnesium hydroxide crystals and cluster-like long-fiber basic magnesium sulfate crystals, both synthesized using a dynamic hydrothermal method. The flame-retardant wood adhesive obtained by mixing the above-mentioned compound flame-retardant powder with a wood adhesive is roller-coated onto veneer. After assembly, aging, cold pressing, core cutting, hot pressing, repair, sanding, and veneer application, flame-retardant plywood is obtained. The compound flame-retardant powder for wood adhesives prepared by this invention has the characteristics of good flame-retardant effect, wide availability of raw materials, low cost, and environmental friendliness and non-toxicity. Furthermore, it has minimal impact on wood adhesives, and the bonding performance of flame-retardant plywood made using this powder is effectively improved.

Description

Technical Field

[0001] This invention relates to compound flame retardant powder for wood adhesives, flame retardant wood adhesives using the same powder, and flame-retardant plywood, belonging to the field of flame retardant preparation technology. Background Technology

[0002] Currently, flame retardants for wood adhesives can be classified into additive flame retardants and reactive flame retardants according to their application methods. Additive flame retardants are mechanically mixed into wood adhesives to impart flame-retardant properties. Common additive flame retardants include organic nitrogen compounds, organic phosphorus compounds, organic bromine compounds, and inorganic compounds such as silicon dioxide, antimony trioxide, aluminum hydroxide, and magnesium hydroxide. Reactive flame retardants involve introducing monomers that react with wood adhesives to impart flame-retardant properties. However, reactive flame retardants are more expensive and require more sophisticated synthesis methods. Additive flame retardants also suffer from drawbacks, such as the high cost and substandard smoke toxicity of organic compounds, and the poor flame-retardant effect of inorganic compounds, which can negatively impact the bonding performance of adhesives.

[0003] Therefore, developing a flame retardant for wood adhesives that is flame-retardant, inexpensive, non-toxic, and harmless is of great significance to the development of the wood industry. Magnesium-based flame retardants have advantages such as smoke suppression, non-toxicity, harmlessness, good thermal stability, and excellent flame-retardant effect, showing promising prospects. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a compound flame-retardant powder for wood adhesives, flame-retardant wood adhesives using the powder, and flame-retardant plywood. The compound flame-retardant powder provided by this invention is composed of flake-like hexagonal magnesium hydroxide (Mg(OH)2) and cluster-like long-fiber basic magnesium sulfate (5Mg(OH)2·MgSO4·3H2O). Upon heating, this flame-retardant powder decomposes into water vapor and magnesium oxide. The water vapor is non-toxic and harmless, absorbing heat while diluting the concentration of combustibles. The magnesium oxide coats the wood surface, isolating it from air and preventing the spread of flames. Furthermore, both crystals in the compound flame-retardant powder are synthesized using a dynamic hydrothermal method, resulting in small crystal sizes that are easily and evenly dispersed with wood adhesives. In addition, the raw materials for the compound flame-retardant powder are widely available and inexpensive, facilitating large-scale promotion.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] A compound flame retardant powder for wood adhesives is composed of flaky hexagonal magnesium hydroxide (Mg(OH)2) and clustered long fibrous basic magnesium sulfate (5Mg(OH)2·MgSO4·3H2O) in a mass ratio of 0 to 1:1 to 0, with a preferred ratio of 7 to 9:3 to 1, and both crystals are synthesized by dynamic hydrothermal method.

[0007] The hexagonal magnesium hydroxide in the form of plates is prepared by the hydrothermal reaction of magnesium oxide, and its size is between 100 nm and 500 nm.

[0008] The basic magnesium sulfate with clustered long fibrous crystals is prepared by hydrothermal reaction of magnesium oxide and magnesium sulfate, and its size is between 30 μm and 80 μm.

[0009] Furthermore, the magnesium oxide used in the preparation of magnesium hydroxide and basic magnesium sulfate in this invention is independently selected as lightly calcined magnesium oxide, with a magnesium oxide mass fraction of not less than 80% and an activity of not less than 35%, preferably not less than 60%.

[0010] Furthermore, the hydrothermal reaction conditions for the hexagonal magnesium hydroxide crystals of the present invention are as follows: reaction temperature of 120℃~180℃, reaction time of 1h~6h, stirring speed of 200rpm~1000rpm, and the mass ratio of water to solid reaction compound is not less than 8.

[0011] Furthermore, the hydrothermal reaction conditions for the basic magnesium sulfate with clustered long fiber crystals described in this invention are as follows: reaction temperature is 180℃~220℃, reaction time is 1~6h, the molar ratio of magnesium oxide to magnesium sulfate in lightly calcined magnesium oxide is 5:1~9:1, stirring speed is 200rpm~1500rpm, and the mass ratio of water to solid reaction compound is not less than 10.

[0012] The present invention also provides a flame-retardant wood adhesive using the above-mentioned compound flame-retardant powder, wherein the flame-retardant wood adhesive is obtained by mixing the above-mentioned compound flame-retardant powder with the wood adhesive, and the mass of the compound flame-retardant powder is 5% to 30% of the mass of the wood adhesive.

[0013] Furthermore, the wood adhesive of the present invention is selected from any one or more of urea-formaldehyde resin, phenolic resin, melamine-formaldehyde resin, soybean protein adhesive, lignin adhesive, and starch adhesive.

[0014] The present invention also provides a flame-retardant plywood using the above-mentioned flame-retardant wood adhesive, wherein the flame-retardant plywood uses the above-mentioned flame-retardant wood adhesive to roll-coate the veneer, with an adhesive application rate of 200-350 g / m². 2 After the blanks are assembled, they are aged for 0.5h to 48h, cold-pressed for 0.5h to 4h, then cored and repaired, and then hot-pressed for 0.1h to 0.5h. The unit pressure of hot pressing is 1 to 1.5MPa, and the hot pressing temperature is 90℃ to 190℃. Finally, putty is applied, sanded, and the surface is veneered to obtain fire-retardant plywood.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] (1) The magnesium hydroxide prepared in this invention is a plate-like hexagonal crystal with a size between 100 nm and 500 nm. Its crystal lattice is intact, its dispersibility is good, and it is easy to mix evenly with adhesives. It can fill the voids inside the wood adhesive, thereby improving the water resistance and tensile strength of the adhesive layer. The prepared basic magnesium sulfate is 5Mg(OH)2·MgSO4·3H2O, which has a cluster-like long fiber crystal form with a size between 30 μm and 80 μm. It has advantages such as high modulus, high strength, non-toxicity, and low smoke emission. When filled into wood adhesives, it can effectively improve the tear strength and crack resistance of the adhesive layer. When heated, the magnesium hydroxide crystals can release water vapor, diluting the concentration of combustibles and oxidizers in the combustion zone. The decomposition product MgO will cover the wood surface, preventing the spread of flames, thus playing a role in flame retardancy and smoke suppression. The basic magnesium sulfate crystals can also decompose upon heating to release water vapor and MgO, playing a similar role.

[0017] (2) This invention uses a one-step reaction method to prepare plate-like hexagonal crystals of magnesium hydroxide and basic magnesium sulfate, namely, magnesium hydroxide is synthesized by lightly calcined magnesium oxide and water under dynamic hydrothermal conditions, and basic magnesium sulfate is synthesized by magnesium sulfate, lightly calcined magnesium oxide and water under dynamic hydrothermal conditions; the two reactions have high atom utilization rate and conform to the principles of green chemistry.

[0018] (3) Compared with single-component flame retardant powder, compound flame retardant powder, through the combination of two particle sizes, can maintain a high addition amount in wood adhesives, while giving full play to the filling effect of nano-sized magnesium hydroxide and the toughening effect of micron-sized basic magnesium sulfate, thereby weakening the adverse effects of flame retardant powder on adhesive performance. Attached Figure Description

[0019] Figure 1 This is the SEM image of the plate-like hexagonal crystal obtained in Example 1 of the present invention.

[0020] Figure 2 The image shows the XRD pattern of the plate-like hexagonal crystal obtained in Example 1 of this invention.

[0021] Figure 3 This is a SEM image of the clustered long fiber crystals obtained in Example 1 of the present invention.

[0022] Figure 4 The image shows the XRD pattern of the clustered long fiber crystals obtained in Example 1 of this invention.

[0023] Figure 5 This is the SEM image of magnesium hydroxide prepared in Comparative Example 1 of this invention.

[0024] Figure 6 This is a SEM image of the basic magnesium sulfate crystals prepared in Comparative Example 2 of this invention.

[0025] Figure 7This is the SEM image of ordinary magnesium hydroxide in Comparative Example 4 of this invention. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] A method for preparing a flame-retardant plywood is as follows:

[0029] (1) Weigh 100g of lightly calcined magnesium oxide (MgO mass fraction 85%, activity 40%) and 1000g of water, add them to a hydrothermal reactor, and react for 4 hours at 140℃ and a stirring rate of 400rpm. After washing, filtering, and drying, the product is obtained as plate-like hexagonal crystals, such as... Figure 1 As shown. After XRD characterization ( Figure 2 It was found that the diffraction peaks of the crystal matched those of magnesium hydroxide in the PDF card;

[0030] (2) Weigh 100g of lightly calcined magnesium oxide (MgO mass fraction 85%, activity 65%), 36g of magnesium sulfate, and 2040g of water, add them to a hydrothermal reactor, and react for 4 hours at 200℃ and a stirring rate of 600rpm. After washing, filtering, and drying, the product yields clustered long fiber crystals, such as... Figure 3 As shown; after XRD characterization ( Figure 4 It was found that the diffraction peaks of the crystal basically matched the basic magnesium sulfate 513 phase crystal form (5Mg(OH)2·MgSO4·3H2O) in the PDF card;

[0031] (3) The crystals prepared above are prepared in a mass ratio of magnesium hydroxide to basic magnesium sulfate of 7:3, and then added to the phenolic adhesive at an addition amount of 15%; the phenolic adhesive is applied manually at an application rate of 200 g / m³. 2 After aging for 0.5 hours, cold pressing for 2 hours, core cutting and repair, and then hot pressing for 0.2 hours at a temperature of 160℃ and a pressure of 1.5MPa, putty is applied, sanded, and veneered to produce fire-retardant plywood.

[0032] Example 2

[0033] A method for preparing a flame-retardant plywood is as follows:

[0034] (1) Weigh 107g of lightly calcined magnesium oxide (MgO mass fraction of 80%, activity of 35%) and 1000g of water, add them to a hydrothermal reactor, and react for 3h at 180℃ and stirring rate of 200rpm. The product after reaction is washed, filtered, and dried to obtain magnesium hydroxide crystals.

[0035] (2) Weigh 95g of lightly calcined magnesium oxide (MgO mass fraction of 90%, activity of 50%), 36g of magnesium sulfate, and 2040g of water, add them to a hydrothermal reactor, and react for 3h at 220℃ and a stirring rate of 600rpm. The product after reaction is washed, filtered and dried to obtain basic magnesium sulfate crystals.

[0036] (3) The crystals prepared above are prepared in a mass ratio of magnesium hydroxide to basic magnesium sulfate of 9:1, and then added to urea-formaldehyde adhesive at a dosage of 20%. The adhesive is applied manually at a dosage of 280 g / m³. 2 After aging for 2 hours and cold pressing for 1 hour, the core is cut and repaired, then hot-pressed for 0.5 hours at a temperature of 90℃ and a pressure of 1.1MPa. After hot pressing, putty is applied, sanded, and the surface is veneered to produce fire-retardant plywood.

[0037] Example 3

[0038] A method for preparing a flame-retardant plywood is as follows:

[0039] (1) Weigh 100g of lightly calcined magnesium oxide (MgO mass fraction of 85%, activity of 40%) and 1000g of water, add them to a hydrothermal reactor, and react for 6h at 120℃ and stirring rate of 600rpm. The product after reaction is washed, filtered, and dried to obtain magnesium hydroxide crystals.

[0040] (2) Weigh 100g of lightly calcined magnesium oxide (MgO mass fraction of 85%, activity of 60%), 66g of magnesium sulfate, and 1890g of water, add them to a hydrothermal reactor, and react for 6h at 180℃ and a stirring rate of 1200rpm. The product after reaction is washed, filtered and dried to obtain basic magnesium sulfate crystals.

[0041] (3) The crystals prepared above are mixed in a mass ratio of magnesium hydroxide to basic magnesium sulfate = 8:2, and then added to the soybean protein adhesive at a dosage of 10%. The adhesive is applied manually at a dosage of 300 g / m³. 2 After aging for 0.5 hours and cold pressing for 4 hours, the core is cut and repaired, then hot-pressed for 0.3 hours at a temperature of 160℃ and a pressure of 1MPa. Finally, putty is applied, sanded, and the surface is veneered to produce fire-retardant plywood.

[0042] Comparative Example 1

[0043] A method for preparing a flame-retardant plywood is as follows:

[0044] (1) Weigh 100g of lightly calcined magnesium oxide (activity 40%) and 1000g of water, add them to a hydrothermal reactor, and react for 6 hours at 100℃ and a stirring rate of 400rpm. The product after reaction is washed, filtered, and dried to obtain magnesium hydroxide crystals, such as... Figure 5 As shown.

[0045] (2) Weigh 100g of lightly calcined magnesium oxide (activity 60%), 36g of magnesium sulfate, and 2040g of water, add them to a hydrothermal reactor, and react for 4h at 200℃ and a stirring rate of 600rpm. The product after the reaction is washed, filtered, and dried to obtain clustered long fiber crystals.

[0046] (3) The crystals prepared above are prepared in a mass ratio of magnesium hydroxide to basic magnesium sulfate of 7:3, and then added to the phenolic adhesive at an addition amount of 15%; the phenolic adhesive is applied manually at an application rate of 200 g / m³. 2 After aging for 0.5 hours, cold pressing for 2 hours, core cutting and repair, and then hot pressing for 0.2 hours at a temperature of 160℃ and a pressure of 1.5MPa, putty is applied, sanded, and veneered to produce fire-retardant plywood.

[0047] Comparative Example 2

[0048] A method for preparing a flame-retardant plywood is as follows:

[0049] (1) Weigh 100g of lightly calcined magnesium oxide (activity 40%) and 1000g of water, add them to a hydrothermal reactor, and react for 4 hours at 140℃ and a stirring rate of 400rpm. The product after reaction is washed, filtered, and dried to obtain plate-like hexagonal crystals;

[0050] (2) Weigh 100g of lightly calcined magnesium oxide (activity 60%), 36g of magnesium sulfate, and 2040g of water, add them to a hydrothermal reactor, and react for 4 hours at 160℃ and a stirring rate of 600rpm. The crystals obtained after washing, filtering, and drying the product are as follows: Figure 6 As shown;

[0051] (3) The crystals prepared above are prepared in a mass ratio of magnesium hydroxide to basic magnesium sulfate of 7:3, and then added to the phenolic adhesive at an addition amount of 15%; the phenolic adhesive is applied manually at an application rate of 200 g / m³. 2 After aging for 0.5 hours, cold pressing for 2 hours, core cutting and repair, and then hot pressing for 0.2 hours at a temperature of 160℃ and a pressure of 1.5MPa, putty is applied, sanded, and veneered to produce fire-retardant plywood.

[0052] Comparative Example 3

[0053] A method for preparing a flame-retardant plywood is as follows:

[0054] (1) Weigh 100g of lightly calcined magnesium oxide (MgO mass fraction of 85%, activity of 40%) and 1000g of water, add them to a hydrothermal reactor, and react for 4h at 100℃ and stirring rate of 400rpm. The product after reaction is washed, filtered, and dried to obtain magnesium hydroxide.

[0055] (2) Weigh 100g of lightly calcined magnesium oxide (MgO mass fraction of 85%, activity of 65%), 36g of magnesium sulfate, and 2040g of water, add them to a hydrothermal reactor, and react for 4h at 160℃ and a stirring rate of 600rpm. The product after reaction is washed, filtered and dried to obtain basic magnesium sulfate.

[0056] (3) The crystals prepared above were mixed in a mass ratio of magnesium hydroxide to basic magnesium sulfate of 7:3 and then added to urea-formaldehyde adhesive at a concentration of 15%. The adhesive viscosity increased and the stickiness decreased, making it impossible to roll the adhesive.

[0057] Comparative Example 4

[0058] A method for preparing a flame-retardant plywood is as follows:

[0059] (1) Choose ordinary magnesium hydroxide, such as Figure 7 As shown;

[0060] (2) Directly add magnesium sulfate and magnesium oxide;

[0061] (3) After preparing the mixture according to the mass ratio of magnesium hydroxide:(magnesium sulfate and magnesium oxide) = 7:3, add it to the phenolic adhesive at a dosage of 15%; apply the phenolic adhesive manually at a dosage of 200g / m². 2 After aging for 0.5 hours, cold pressing for 2 hours, core cutting and repair, followed by hot pressing for 0.2 hours at a temperature of 160℃ and a pressure of 1.5MPa, the plywood delaminated.

[0062] Table 1 shows the test results of the physical and chemical properties of the flame-retardant plywood prepared in Examples 1-3 and Comparative Examples 1-2. In Comparative Example 3, the adhesive could not be rolled, and in Comparative Example 4, the plywood delaminated directly. The physical and chemical properties were tested according to the requirements of GB / T 18101-2013 "Flame-retardant Plywood"; XRD characterization was performed using a Rigaku Ultima VI model; and morphology testing was performed using a Zeiss Sigma 300.

[0063] Table 1. Test results of the physical and chemical properties of the flame-retardant plywood prepared in each embodiment and comparative example.

[0064] project Class II adhesive strength / MPa <![CDATA[THR 600s / MJ]]> <![CDATA[SMOGRA(m 2 / s 2 )]]> <![CDATA[TSP 600s / m 2 ]]> Example 1 0.96 12.8 25.6 36.1 Example 2 0.76 11.2 23.3 38.7 Example 3 1.02 13.6 26.4 40.9 Comparative Example 1 0.56 15.1 37.2 50.5 Comparative Example 2 0.62 14.6 35.1 52.8

[0065] According to GB / T 18101-2013 "Flame-Retardant Plywood", Class II plywood must pass a hot water immersion test at 63±3℃ with a bond strength ≥0.7MPa (poplar) and a total heat release (THR) of 600s. 600s ≤15MJ (requirements for flame-retardant B1-C class); Smoke generation rate index (SMOGRA) ≤30m 2 / s 2 Total flue gas generated (TSP) over 600 seconds 600s ≤50m 2 As can be seen from the test data in the table above, Examples 1-4 of the present invention all meet the B1-C grade requirements for flame-retardant plywood used under humid conditions.

[0066] As can be seen from Examples 1-3, when magnesium hydroxide flake hexagonal crystals and basic magnesium sulfate cluster long fiber crystals are added in appropriate proportions, the resulting plywood exhibits good bonding performance and flame retardant properties.

[0067] As can be seen from Example 1 and Comparative Example 1, when the hydrothermal reaction temperature of magnesium oxide is too low, the resulting magnesium hydroxide has a prismatic structure with large particle size and poor dispersibility, making it difficult to mix evenly with phenolic adhesive, thus affecting the bonding performance of the board.

[0068] As can be seen from Example 1 and Comparative Example 2, when the reaction temperature of magnesium oxide and magnesium sulfate is too low, the resulting basic magnesium sulfate crystals are plate-shaped spheres with a large specific surface area. They have a certain degree of hygroscopicity and are prone to clumping in phenolic adhesives, which leads to a decrease in the bonding performance of the boards.

[0069] As can be seen from Example 1 and Comparative Example 3, when the hydrothermal temperature is too low, the magnesium hydroxide crystals formed are prone to agglomeration, indicating high surface energy and easy water absorption. Furthermore, basic magnesium sulfate crystals have more pores, improving water retention. When these two are mixed with the adhesive, they absorb water from the adhesive, leading to increased adhesive consistency, decreased viscosity, and inability to roll the adhesive.

[0070] As can be seen from Example 1 and Comparative Example 4, ordinary magnesium hydroxide is prone to agglomeration, has high surface energy, and is not easily dispersed evenly with adhesive. Furthermore, the direct addition of magnesium sulfate and magnesium oxide during high-temperature pressing intensifies the hydration reaction of magnesium oxide, forming magnesium hydroxide, which expands significantly in volume, leading to delamination of the board after hot pressing.

Claims

1. A compounded fire-retardant powder for wood adhesives, characterized by, The magnesium hydroxide of the flaky hexagonal crystal and the basic magnesium sulfate of the cluster long fiber crystal are compounded according to the mass ratio of 7-9:3-1, and both of the crystals are synthesized by a dynamic hydrothermal method; The magnesium hydroxide of the flaky hexagonal crystal is prepared by hydrothermal reaction of light-burned magnesium oxide, and the size is between 100nm and 500nm; The basic magnesium sulfate of the cluster long fiber crystal is prepared by hydrothermal reaction of light-burned magnesium oxide and magnesium sulfate, and the size is between 30μm and 80μm; The reaction conditions for preparing the magnesium hydroxide by hydrothermal reaction of light-burned magnesium oxide are 120℃-180℃, reaction for 1h-6h, stirring rate of 200rpm-1000rpm, and the mass ratio of water to solid reaction compound is not less than 8; The reaction conditions for preparing the basic magnesium sulfate by hydrothermal reaction of light-burned magnesium oxide and magnesium sulfate are 180℃-220℃, reaction for 1-6h, the molar ratio of magnesium oxide in light-burned magnesium oxide to magnesium sulfate is 5:1-9:1, stirring rate of 200rpm-1500rpm, and the mass ratio of water to solid reaction compound is not less than 10; The mass fraction of magnesium oxide in the light-burned magnesium oxide is not less than 80%, and the activity is not less than 35%.

2. The compounded fire-retardant powder according to claim 1, characterized in that, The activity of the magnesium oxide is not less than 60%.

3. A fire-retardant wood adhesive using the compound fire-retardant powder for wood adhesive according to claim 1 or 2, characterized by, The fire-retardant wood adhesive is obtained by stirring and uniformly mixing the above compounded fire-retardant powder and wood adhesive, and the mass of the compounded fire-retardant powder is 5%-30% of the mass of the wood adhesive.

4. The fire-retardant wood adhesive according to claim 3, wherein the fire-retardant wood adhesive is characterized by, The wood adhesive is selected from any one or more than one of urea-formaldehyde resin, phenol-formaldehyde resin, melamine-formaldehyde resin, soybean protein adhesive, lignin adhesive, and starch adhesive.

5. A fire resistant plywood using the fire resistant wood adhesive according to claim 3 or 4, characterized in that, The fire-retardant plywood is prepared by using the fire-retardant wood adhesive roll-coated veneer, the glue application amount is 200~350 g / m 2 After the assembly, the aging is performed for 0.5 h~48 h, the cold pressing is performed for 0.5 h~4 h, the core is cut and repaired, the hot pressing is performed for 0.1~0.5 h, the hot pressing unit pressure is 1~1.5 MPa, the hot pressing temperature is 90℃~190℃, and then the putty is scraped, sanded, and faced to obtain the fire-retardant plywood.

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