Waterproofing agent for medium density fiberboard, preparation and application

Abstract

The application discloses a waterproof agent for medium-density fiberboard, and preparation and application of the waterproof agent. The waterproof agent is prepared from the following raw materials in parts by mass: modified phenolic resin 100 parts, white oil 1-200 parts, paraffin wax 10-1000 parts, microcrystalline wax 1-100 parts, synthetic wax 1-100 parts, urotropine and / or paraformaldehyde 0.1-5 parts. The medium-density fiberboard prepared from the waterproof agent has a 24-hour water absorption thickness expansion rate of less than or equal to 7%, and the inner bonding strength is increased by more than 60%, and can be widely applied to the production of high-humidity environment reinforced wood floor base materials, medium-density fiberboard and high-density fiberboard.

Description

Technical Field

[0001] This invention belongs to the field of engineered wood product manufacturing technology. More specifically, it relates to a waterproofing agent for medium-density fiberboard (MDF), its preparation, and its application. Background Technology

[0002] The shrinkage and swelling due to moisture, including wood, fiberboard, particleboard, plywood, and wood flooring, are major technical challenges affecting their use. Dimensional stability is one of the key technical indicators for evaluating wood materials and products.

[0003] To reduce the water absorption thickness swelling rate and improve the dimensional stability of medium-density fiberboard (MDF), the traditional production process involves melting 58# or 62# paraffin wax and spraying it into a slurry pipe. The wax mixes with the wet fibers, adhering to the fiber surface. The hydrophobic properties of the wax slow down the penetration of water into the MDF. The amount of paraffin wax added is typically 0.5% to 1.5% of the dry fiber mass. Excessive addition of paraffin wax can affect the bonding between fibers and reduce the mechanical properties of the MDF. MDF or high-density fiberboard produced using urea-formaldehyde resin or melamine-modified urea-formaldehyde resin has a 24-hour ultimate water absorption thickness swelling rate of approximately 7%.

[0004] A waterproofing emulsion was prepared from paraffin using surfactants, resulting in a paraffin emulsion or suspension with a diameter of 200 nm to 30 μm. This improved the coverage of paraffin on the fiber surface and reduced the amount of paraffin waterproofing agent required. However, the surfactants significantly reduced the surface tension of water, increased the wettability of wood materials, and increased the water absorption rate and amount of medium-density fiberboard (MDF). The 24-hour ultimate water absorption thickness swelling rate was higher than that of molten paraffin.

[0005] Regardless of whether molten paraffin or paraffin emulsion is used as a waterproofing agent for medium-density fiberboard (MDF), the waterproofing performance of MDF deteriorates rapidly after secondary processing and hot pressing, with the 24-hour water absorption thickness expansion rate increasing by 50-200%. Studies have shown that during secondary processing, under the combined effects of temperature, pressure, and moisture in the MDF, the paraffin partially covering the fiber surface melts again or even vaporizes, penetrating into the fiber interior. This is one of the main reasons for the deterioration of the waterproofing performance of MDF.

[0006] Therefore, there is a need to develop a new type of waterproofing agent for medium-density fiberboard to overcome the problems existing in the prior art. Summary of the Invention

[0007] To address the aforementioned problems, the first objective of this invention is to provide a waterproofing agent for medium-density fiberboard.

[0008] A second objective of this invention is to provide a method for preparing the waterproofing agent for medium-density fiberboard as described above.

[0009] The third objective of this invention is to provide an application of a waterproofing agent for medium-density fiberboard in the preparation of engineered wood products.

[0010] To achieve the first objective mentioned above, the present invention adopts the following technical solution:

[0011] This invention discloses a waterproofing agent for medium-density fiberboard, characterized in that it is made from the following raw materials in parts by weight: 100 parts modified phenolic resin, 1-200 parts white oil, 10-1000 parts paraffin wax, 1-100 parts microcrystalline wax, 1-100 parts synthetic wax, and 0.1-5 parts hexamethylenetetramine and / or paraformaldehyde.

[0012] To address the technical bottleneck of high water absorption thickness expansion rate in medium-density fiberboard (MDF) produced using urea-formaldehyde resin or melamine-modified urea-formaldehyde resin, and the further deterioration of waterproof performance during secondary processing, this invention uses modified phenolic resin as a carrier and adds white oil, microcrystalline wax, and synthetic wax components to the commonly used MDF waterproofing agent 52#~62# paraffin wax to prepare a waterproofing agent for MDF. During the hot pressing process of fiberboard, the modified phenolic resin in this waterproofing agent reacts with hexamethylenetetramine and / or paraformaldehyde, as well as urea-formaldehyde resin coated on the fibers and its free formaldehyde, to generate a tough, mesh-like polymer material that covers the fiber surface, serving the dual functions of bonding the fibers and waterproofing, thus improving the strength and waterproofing performance of the engineered wood product. Simultaneously, the mesh-like polymer material formed by the modified phenolic resin, together with high-melting-point microcrystalline wax and synthetic wax, forms a tough protective film, reducing the amount of paraffin wax entering the wood cell cavities and pores during the hot pressing of medium-density fiberboard and during secondary hot pressing, thereby improving the waterproofing effect of the waterproofing agent. The oleic acid, ethanolamine, and dimethylacetamide in the modified phenolic resin disperse and emulsify paraffin wax, microcrystalline wax, and synthetic wax, reducing their particle size and effectively improving the uniformity of their distribution on the fibers. White oil has low viscosity and good permeability, allowing it to enter the cell cavities and pores of wood. During the hot pressing of medium-density fiberboard (MDF) and its secondary processing, it covers the surface of the cell cavities and pores, improving the waterproof performance of the wood material itself.

[0013] Furthermore, the waterproofing agent for medium-density fiberboard is made from the following raw materials in parts by weight: 100 parts modified phenolic resin, 5-50 parts white oil, 20-500 parts paraffin wax, 5-50 parts microcrystalline wax, 5-50 parts synthetic wax, and 0.3-3.0 parts hexamethylenetetramine and / or paraformaldehyde.

[0014] Furthermore, the modified phenolic resin is prepared according to the following process:

[0015] (1) Add a certain amount of phenol to the reaction vessel, heat to 50-60℃, add phosphoric acid, and maintain for 10-15 minutes;

[0016] (2) Add formaldehyde solution, heat to 98-100℃, and maintain for 60-120 minutes;

[0017] (3) Cool down to 75-80℃ and adjust the pH to 8.5-9.5 with sodium hydroxide;

[0018] (4) Slowly add paraformaldehyde and maintain at 90-95℃ for 30-120 minutes;

[0019] (5) Detect the viscosity of the resin. When the viscosity is 50-2000 cps, add oleic acid, ethanolamine and dimethylacetamide, and then cool down to obtain the final product.

[0020] Furthermore, in step 1, the molar ratio of phosphoric acid to phenol is 0.02-0.04:1; in step 2, the molar ratio of formaldehyde to phenol is 0.65-0.85:1; in step 4, the molar ratio of paraformaldehyde to phenol is 0.80-1.2:1, so that the molar ratio of (formaldehyde + paraformaldehyde) / phenol is 1.60-2.10.

[0021] Furthermore, in step 5, the mass ratio of oleic acid to phenol is 0.1-1:1, the mass ratio of ethanolamine to phenol is 0.02-0.1:1, and the mass ratio of dimethylacetamide to phenol is 0.005-0.05:1.

[0022] Furthermore, the white oil may be of one or more types, including but not limited to 5#, 7#, 10#, 15#, 22#, 26#, 32#, 46#, 86#, 100#, 220#, and 320#; preferably, using one or more of 10#, 15#, 22#, 26#, and 32# white oil will yield better results.

[0023] Furthermore, the paraffin wax grades include, but are not limited to, one or more of 50#, 52#, 54#, 58#, 60#, 62#, 64#, 68#, and 70#; preferably, using one or more of 56#, 58#, 60#, and 62# paraffin wax will yield better results.

[0024] Furthermore, the microcrystalline wax may be of one or more types, including but not limited to 70#, 75#, 80#, 85#, and 90#; preferably, a soft, high-viscosity microcrystalline wax will be more effective.

[0025] Furthermore, the synthetic wax includes, but is not limited to, one or more of polyethylene wax, oxidized polyethylene wax, Fischer-Topsy wax, hydrogenated sesame oil wax, S wax, OP wax, O wax, and E wax; preferably, polyethylene wax is preferred as the synthetic wax.

[0026] To achieve the second objective mentioned above, the present invention adopts the following technical solution:

[0027] This invention discloses a method for preparing a waterproofing agent for medium-density fiberboard as described above, comprising the following steps:

[0028] Weigh the modified phenolic resin prepared according to the above method, heat it to 50-90℃, add white oil, and stir at a speed of 60-2000 rpm for 15-20 minutes to obtain the first mixture. Then, raise the temperature to 90-120℃; add paraffin wax, microcrystalline wax, and synthetic wax to the first mixture, stir until completely dissolved, and stir at a speed of 60-2000 rpm for 15-20 minutes to obtain the second mixture; then add hexamethylenetetramine and / or paraformaldehyde to the second mixture, and stir at a speed of 60-2000 rpm for 30-120 minutes to obtain the final product.

[0029] To achieve the third objective mentioned above, the present invention adopts the following technical solution:

[0030] This invention discloses the application of the waterproofing agent for medium-density fiberboard described above in the preparation of medium-density fiberboard.

[0031] Furthermore, the specific steps for preparing medium-density fiberboard are as follows:

[0032] Urea-formaldehyde resin adhesive and medium-density fiberboard waterproofing agent are added to plant fibers in the spray pipe. After rapid drying, screening, separation, laying, and pre-pressing, a board blank is obtained. Then, the board blank is hot-pressed. After pressing, the board blank is trimmed, cooled, sized, and finely sanded to obtain medium-density fiberboard.

[0033] Furthermore, the hot-pressing temperature is 170-240℃, the hot-pressing time is 10-15 seconds / mm, and the maximum unit pressure is 3.0MPa.

[0034] The beneficial effects of this invention are as follows:

[0035] 1. The medium-density fiberboard (MDF) waterproofing agent of the present invention, when used in MDF produced with urea-formaldehyde resin or melamine-modified urea-formaldehyde resin, has a 24-hour water absorption thickness expansion rate of ≤7%, which is lower than the limit value of ≥7% for MDF produced with 58# or 62# paraffin waterproofing agent in the prior art.

[0036] 2. When using the waterproofing agent for medium-density fiberboard of the present invention, medium-density fiberboard produced with urea-formaldehyde resin or melamine-modified urea-formaldehyde resin has a 72-hour water absorption thickness expansion rate of ≤12%, and the thickness tends to stabilize as the impregnation time increases. In contrast, medium-density fiberboard produced with 58# or 62# paraffin waterproofing agent in the prior art has a 72-hour water absorption thickness expansion rate of ≥20%, and the thickness continues to increase as the impregnation time increases until the product is damaged.

[0037] 3. When using the waterproofing agent for medium-density fiberboard of the present invention, the water absorption thickness expansion rate of medium-density fiberboard produced by urea-formaldehyde resin or melamine-modified urea-formaldehyde resin after secondary processing and hot pressing is ≤7%; the water absorption thickness expansion rate of medium-density fiberboard produced by the prior art after secondary processing and hot pressing is ≥10%, which is close to the limit of the national standard.

[0038] 4. Medium-density fiberboard (MDF) produced using urea-formaldehyde resin or melamine-modified urea-formaldehyde resin, when using the waterproofing agent for MDF of the present invention, has an internal bond strength that is increased by more than 60%, and the internal bond strength increases with the increase of the amount of waterproofing agent. For MDF produced using waterproofing agents of the prior art, when the percentage of paraffin wax / ocean-dry fiber mass is greater than 1.5%, the internal bond strength of the product decreases significantly with the increase of the amount of paraffin wax.

[0039] 5. Using the waterproofing agent for medium-density fiberboard of the present invention, medium-density fiberboard produced with urea-formaldehyde resin or melamine-modified urea-formaldehyde resin can be used to produce medium-density fiberboard for use in high-humidity environments; in the prior art, medium-density fiberboard for use in high-humidity environments is usually produced using isocyanate resin. Detailed Implementation

[0040] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0041] In this invention, the self-made modified phenolic resins in Examples 1-3 and Comparative Examples 5-7 were prepared according to the following process:

[0042] (1) Add 1.0 mole of phenol to the reactor, start the stirring device, heat to 50-60°C, add 0.03 mole of 85% phosphoric acid by mass, and maintain for 10-15 minutes;

[0043] (2) Add 0.68 mol of formaldehyde solution with a mass percentage of 37.0%, heat to 98-100℃, and maintain for 120 minutes;

[0044] (3) Cool down to 78-80℃ and adjust the pH to 8.5-9.0 with caustic soda;

[0045] (4) Slowly add paraformaldehyde to make the molar ratio of (formaldehyde + paraformaldehyde) / phenol 1.68, and maintain the reaction at a temperature of 90-93°C;

[0046] (5) Detect the viscosity of the resin. When the viscosity is 150 cps, add oleic acid, ethanolamine and dimethylacetamide, with the addition amounts being 21.3%, 3.2% and 2.1% of the amount of phenol added, respectively. Keep it for 30 minutes and cool it down to below 50°C for later use.

[0047] The self-made modified phenolic resins in Examples 4-6 were prepared according to the following process:

[0048] (1) Add 1.0 mole of phenol to the reactor, start the stirring device, heat to 50-60°C, add 0.03 mole of 85% phosphoric acid by mass, and maintain for 10-15 minutes;

[0049] (2) Add 1 mole of formaldehyde solution with a mass percentage of 37.0%, heat to 98-100℃, and maintain for 120 minutes;

[0050] (3) Cool down to 78-80℃ and adjust the pH to 8.5-9.0 with caustic soda;

[0051] (4) Slowly add paraformaldehyde to make the molar ratio of (formaldehyde + paraformaldehyde) / phenol 1.80, and maintain the reaction at a temperature of 90-93°C;

[0052] (5) Detect the viscosity of the resin. When the viscosity is 300 cps, add oleic acid, ethanolamine and dimethylacetamide, with the addition amounts being 19.4%, 3.4% and 1.4% of the phenol addition amount, respectively. Keep it for 30 minutes and cool it down to below 50°C for later use.

[0053] The self-made modified phenolic resins in Examples 7-9 were prepared according to the following process:

[0054] (1) Add 1.0 mole of phenol to the reactor, start the stirring device, heat to 50-60°C, add 0.03 mole of 85% phosphoric acid by mass, and maintain for 10-15 minutes;

[0055] (2) Add 0.86 mol of formaldehyde solution with a mass percentage of 37.0%, heat to 98-100℃, and maintain for 120 minutes;

[0056] (3) Cool down to 78-80℃ and adjust the pH to 8.5-9.0 with caustic soda;

[0057] (4) Slowly add paraformaldehyde to make the molar ratio of (formaldehyde + paraformaldehyde) / phenol 2.03, and maintain the reaction at a temperature of 90-93°C;

[0058] (5) Detect the viscosity of the resin. When the viscosity is 350 cps, add oleic acid, ethanolamine and dimethylacetamide, with the addition amounts being 29.5%, 8.5% and 3% of the amount of phenol added, respectively. Keep it for 30 minutes and cool it down to below 50°C for later use.

[0059] Example 1

[0060] This embodiment relates to a waterproofing agent for medium-density fiberboard, the raw materials for which are prepared include:

[0061] 100 parts of self-made modified phenolic resin, 5 parts of 15# white oil, 500 parts of 58# paraffin wax, 50 parts of 85# microcrystalline wax, 50 parts of polyethylene wax, and 2 parts of hexamethylenetetramine.

[0062] Its preparation method includes the following steps:

[0063] 1) Add 100 parts by weight of modified phenolic resin to a reactor equipped with a heating jacket and a stirring device, and heat to 80°C;

[0064] 2) Start the mixer at 120 rpm, add 5 parts by weight of 15# white oil, and stir for 15 minutes to obtain the first mixture;

[0065] 3) Heat to 120℃, add 500 parts by weight of 58# paraffin wax, 50 parts by weight of 85# microcrystalline wax and 50 parts by weight of polyethylene wax, stir until completely dissolved, and keep for 20 minutes to obtain the second mixture;

[0066] 4) Add 2 parts by weight of hexamethylenetetramine and keep for 60 minutes to obtain a waterproofing agent for medium-density fiberboard.

[0067] Urea-formaldehyde resin adhesive and the aforementioned waterproofing agent were added to poplar wood fibers in a spraying pipe. After rapid drying, screening, separation, laying, and pre-pressing, a board blank was obtained. The board blank was then hot-pressed, and after edge trimming, cooling, thickness determination, and fine sanding, medium-density fiberboard (MDF) was produced. The hot-pressing temperature for 18mm thick MDF was 220℃, the hot-pressing time was 300 seconds, and the maximum unit pressure was 3.0MPa. Based on 100 parts by weight of oven-dry wood fiber, the specific composition is shown in Table 1, and the product's internal bond strength, water absorption, and thickness swelling rate are shown in Table 2.

[0068] Example 2

[0069] This embodiment relates to a waterproofing agent for medium-density fiberboard, the raw materials for which are prepared include:

[0070] 100 parts of self-made modified phenolic resin, 5 parts of 15# white oil, 485 parts of 58# paraffin wax, 5 parts of 85# microcrystalline wax, 5 parts of polyethylene wax, and 2 parts of hexamethylenetetramine.

[0071] The preparation method is the same as in Example 1.

[0072] Other process conditions are the same as in Example 1. Based on 100 parts by weight of oven-dried wood fiber, the specific composition is shown in Table 1, and the water absorption thickness swelling rate of the product is shown in Table 2.

[0073] Example 3

[0074] This embodiment relates to a waterproofing agent for medium-density fiberboard, the raw materials for which are prepared include:

[0075] The ingredients included 100 parts of self-made modified phenolic resin, 20 parts of 15# white oil, 360 parts of 58# paraffin wax, 10 parts of 85# microcrystalline wax, 10 parts of polyethylene wax, and 1 part of hexamethylenetetramine.

[0076] The preparation method is the same as in Example 1.

[0077] Other process conditions are the same as in Example 1. Based on 100 parts by weight of oven-dried wood fiber, the specific composition is shown in Table 1, and the water absorption thickness swelling rate of the product is shown in Table 2.

[0078] Example 4

[0079] This embodiment relates to a waterproofing agent for medium-density fiberboard, the raw materials for which are prepared include:

[0080] The ingredients included 100 parts of self-made modified phenolic resin, 50 parts of 20# white oil, 210 parts of 60# paraffin wax, 20 parts of 85# microcrystalline wax, 20 parts of polyethylene wax, and 1 part of hexamethylenetetramine.

[0081] The preparation method is the same as in Example 1.

[0082] Other process conditions are the same as in Example 1. Based on 100 parts by weight of oven-dried wood fiber, the specific composition is shown in Table 1, and the water absorption thickness swelling rate of the product is shown in Table 2.

[0083] Example 5

[0084] This embodiment relates to a waterproofing agent for medium-density fiberboard, the raw materials for which are prepared include:

[0085] The ingredients included 100 parts of self-made modified phenolic resin, 15 parts of 20# white oil, 170 parts of 62# paraffin wax, 10 parts of 80# microcrystalline wax, 5 parts of polyethylene wax, and 1 part of hexamethylenetetramine.

[0086] The preparation method is the same as in Example 1.

[0087] Other process conditions are the same as in Example 1. Based on 100 parts by weight of oven-dried wood fiber, the specific composition is shown in Table 1, and the water absorption thickness swelling rate of the product is shown in Table 2.

[0088] Example 6

[0089] This embodiment relates to a waterproofing agent for medium-density fiberboard, the raw materials for which are prepared include:

[0090] 100 parts of self-made modified phenolic resin, 10 parts of 15# white oil, 80 parts of 58# paraffin wax, 5 parts of 85# microcrystalline wax, 5 parts of polyethylene wax, and 2.0 parts of hexamethylenetetramine.

[0091] The preparation method is the same as in Example 1.

[0092] Other process conditions are the same as in Example 1. Based on 100 parts by weight of oven-dried wood fiber, the specific composition is shown in Table 1, and the water absorption thickness swelling rate of the product is shown in Table 2.

[0093] Example 7

[0094] This embodiment relates to a waterproofing agent for medium-density fiberboard, the raw materials for which are prepared include:

[0095] The ingredients are: 100 parts of self-made modified phenolic resin, 5 parts of 15# white oil, 45 parts of 58# paraffin wax, 20 parts of 85# microcrystalline wax, 5 parts of polyethylene wax, and 1.0 part of paraformaldehyde.

[0096] The preparation method is the same as in Example 1.

[0097] Other process conditions are the same as in Example 1. Based on 100 parts by weight of oven-dried wood fiber, the specific composition is shown in Table 1, and the water absorption thickness swelling rate of the product is shown in Table 2.

[0098] Example 8

[0099] This embodiment relates to a waterproofing agent for medium-density fiberboard, the raw materials for which are prepared include:

[0100] The ingredients are: 100 parts of self-made modified phenolic resin, 5 parts of 15# white oil, 40 parts of 58# paraffin wax, 5 parts of 85# microcrystalline wax, 5 parts of polyethylene wax, and 1.5 parts of paraformaldehyde.

[0101] The preparation method is the same as in Example 1.

[0102] Other process conditions are the same as in Example 1. Based on 100 parts by weight of oven-dried wood fiber, the specific composition is shown in Table 1, and the water absorption thickness swelling rate of the product is shown in Table 2.

[0103] Example 9

[0104] This embodiment relates to a waterproofing agent for medium-density fiberboard, the raw materials for which are prepared include:

[0105] The ingredients are: 100 parts of self-made modified phenolic resin, 5 parts of 15# white oil, 20 parts of 58# paraffin wax, 5 parts of 85# microcrystalline wax, 5 parts of polyethylene wax, and 0.5 parts of paraformaldehyde.

[0106] The preparation method is the same as in Example 1.

[0107] Other process conditions are the same as in Example 1. Based on 100 parts by weight of oven-dried wood fiber, the specific composition is shown in Table 1, and the water absorption thickness swelling rate of the product is shown in Table 2.

[0108] Comparative Example 1

[0109] Add 100 parts by weight of 58# paraffin wax to a reactor equipped with a heating jacket and a stirring device, heat to 90°C, and set aside after the paraffin wax has completely melted.

[0110] Other process conditions are the same as in Example 1. Based on 100 parts by weight of oven-dried wood fiber, the specific composition is shown in Table 1, and the water absorption thickness swelling rate of the product is shown in Table 2.

[0111] Comparative Example 2

[0112] Add 100 parts by weight of 58# paraffin wax and 50 parts by weight of 15# white oil to a reactor equipped with a heating jacket and a stirring device, heat to 90°C, and set aside after the paraffin wax has completely melted.

[0113] Other process conditions are the same as in Example 1. Based on 100 parts by weight of oven-dried wood fiber, the specific composition is shown in Table 1, and the water absorption thickness swelling rate of the product is shown in Table 2.

[0114] Comparative Example 3

[0115] Add 100 parts by weight of 58# paraffin wax and 50 parts by weight of 85# microcrystalline wax to a reactor equipped with a heating jacket and a stirring device, heat to 95°C, and set aside after the paraffin wax has completely melted.

[0116] Other process conditions are the same as in Example 1. Based on 100 parts by weight of oven-dried wood fiber, the specific composition is shown in Table 1, and the water absorption thickness swelling rate of the product is shown in Table 2.

[0117] Comparative Example 4

[0118] Add 100 parts by weight of 58# paraffin wax and 50 parts by weight of polyethylene wax to a reactor equipped with a heating jacket and a stirring device, heat to 95°C, and set aside after the paraffin wax has completely melted.

[0119] Other process conditions are the same as in Example 1. Based on 100 parts by weight of oven-dried wood fiber, the specific composition is shown in Table 1, and the water absorption thickness swelling rate of the product is shown in Table 2.

[0120] Comparative Example 5

[0121] 100 parts of homemade modified phenolic resin and 1 part of hexamethylenetetramine are heated to 95°C and stirred evenly for later use.

[0122] Other process conditions are the same as in Example 1. Based on 100 parts by weight of oven-dried wood fiber, the specific composition is shown in Table 1, and the water absorption thickness swelling rate of the product is shown in Table 2.

[0123] Comparative Example 6

[0124] The preparation of the modified phenolic resin is the same as in Example 1.

[0125] The ingredients included 100 parts of self-made modified phenolic resin, 50 parts of 15# white oil, 1100 parts of 58# paraffin wax, 20 parts of 85# microcrystalline wax, 20 parts of polyethylene wax, and 2 parts of hexamethylenetetramine.

[0126] Other process conditions are the same as in Example 1. Based on 100 parts by weight of oven-dried wood fiber, the specific composition is shown in Table 1, and the water absorption thickness swelling rate of the product is shown in Table 2.

[0127] Comparative Example 7

[0128] The preparation of the modified phenolic resin is the same as in Example 1.

[0129] The ingredients included 100 parts of self-made modified phenolic resin, 200 parts of 15# white oil, 600 parts of 58# paraffin wax, 20 parts of 85# microcrystalline wax, 20 parts of polyethylene wax, and 2 parts of hexamethylenetetramine.

[0130] Other process conditions are the same as in Example 1. Based on 100 parts by weight of oven-dried wood fiber, the specific composition is shown in Table 1, and the water absorption thickness swelling rate of the product is shown in Table 2.

[0131] Table 1. Raw material composition of the examples and comparative examples

[0132]

[0133]

[0134] Table 2. Internal Bond Strength, Water Absorption, Thickness, and Swelling Rate of Medium Density Fiberboard

[0135] Internal bond strength 24-hour water absorption thickness expansion rate (%) 72h water absorption thickness swelling rate (%) Example 1 1.07 6.5 11.3 Example 2 1.04 6.4 11.7 Example 3 1.05 6.8 11.5 Example 4 1.11 6.7 11.8 Example 5 1.08 5.5 10.8 Example 6 1.21 6.1 10.8 Example 7 1.23 5.6 9.9 Example 8 1.19 5.9 10.2 Example 9 1.27 5.7 9.8 Comparative Example 1 0.87 8.7 25.9 Comparative Example 2 0.92 9.8 27.5 Comparative Example 3 0.79 8.2 24.3 Comparative Example 4 0.91 8.6 23.9 Comparative Example 5 1.35 7.3 14.9 Comparative Example 6 0.57 9.2 21.3 Comparative Example 7 0.61 10.7 23.2

[0136] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A waterproofing agent for medium-density fiberboard, characterized in that, It is made from the following raw materials in parts by weight: 100 parts modified phenolic resin, 5-50 parts white oil, 20-500 parts paraffin wax, 5-50 parts microcrystalline wax, 5-50 parts synthetic wax, and 0.3-3.0 parts hexamethylenetetramine and / or paraformaldehyde. The modified phenolic resin is prepared according to the following process: (1) Add a certain amount of phenol to the reaction vessel, heat to 50-60℃, add phosphoric acid, and maintain for 10-15 minutes; (2) Add formaldehyde solution, heat to 98-100℃, and maintain for 60-120 minutes; (3) Cool down to 75-80℃ and adjust the pH to 8.5-9.5 with sodium hydroxide; (4) Add paraformaldehyde slowly and keep at 90-95℃ for 30-120 minutes; (5) Test the viscosity of the resin. When the viscosity is 50-2000 cps, add oleic acid, ethanolamine and dimethylacetamide, and then cool down to obtain the final product.

2. The waterproofing agent for medium-density fiberboard according to claim 1, characterized in that, In step 1, the molar ratio of phosphoric acid to phenol is 0.02-0.04:1; in step 2, the molar ratio of formaldehyde to phenol is 0.65-0.85:1; in step 4, the molar ratio of paraformaldehyde to phenol is 0.80-1.2:1, so that the molar ratio of (formaldehyde + paraformaldehyde) / phenol is 1.60-2.

10.

3. The waterproofing agent for medium-density fiberboard according to claim 1, characterized in that, In step 5, the mass ratio of oleic acid to phenol is 0.1-1:1, the mass ratio of ethanolamine to phenol is 0.02-0.1:1, and the mass ratio of dimethylacetamide to phenol is 0.005-0.05:

1.

4. The waterproofing agent for medium-density fiberboard according to claim 1, characterized in that, The white oil is of one or more types, including 5#, 7#, 10#, 15#, 22#, 26#, 32#, 46#, 86#, 100#, 220#, and 320#.

5. The waterproofing agent for medium-density fiberboard according to claim 4, characterized in that, The white oil may be one or more of the following grades: 10#, 15#, 22#, 26#, and 32#.

6. The waterproofing agent for medium-density fiberboard according to claim 1, characterized in that, The paraffin wax grades include one or more of 50#, 52#, 54#, 58#, 60#, 62#, 64#, 68#, and 70#.

7. The waterproofing agent for medium-density fiberboard according to claim 6, characterized in that, The paraffin wax grades include one or more of 56#, 58#, 60#, and 62#.

8. The waterproofing agent for medium-density fiberboard according to claim 1, characterized in that, The microcrystalline wax is available in one or more of the following grades: 70#, 75#, 80#, 85#, and 90#.

9. The waterproofing agent for medium-density fiberboard according to claim 1, characterized in that, The synthetic wax includes one or more of polyethylene wax, oxidized polyethylene wax, Fischer-Topsy wax, S wax, OP wax, O wax, and E wax.

10. The waterproofing agent for medium-density fiberboard according to claim 9, characterized in that, The synthetic wax is selected from polyethylene wax.

11. The method for preparing the waterproofing agent for medium-density fiberboard according to any one of claims 1-10, characterized in that, Includes the following steps: Weigh the modified phenolic resin, heat it to 50-90℃, add white oil, and stir at a speed of 60-2000 r / min for 15-20 minutes to obtain the first mixture. Then, raise the temperature to 90-120℃; add paraffin wax, microcrystalline wax, and synthetic wax to the first mixture, stir until completely dissolved, and stir at a speed of 60-2000 r / min for 15-20 minutes to obtain the second mixture; then add hexamethylenetetramine and / or paraformaldehyde to the second mixture, and stir at a speed of 60-2000 r / min for 30-120 minutes to obtain the final product.

12. The use of the waterproofing agent for medium-density fiberboard as described in any one of claims 1-10 in the preparation of medium-density fiberboard.

13. The application according to claim 12, characterized in that, The specific steps for preparing medium-density fiberboard are as follows: Urea-formaldehyde resin adhesive and medium-density fiberboard waterproofing agent are added to plant fibers in the spray pipe. After rapid drying, screening, separation, laying, and pre-pressing, a board blank is obtained. Then, the board blank is hot-pressed. After pressing, the board blank is trimmed, cooled, sized, and finely sanded to obtain medium-density fiberboard.

14. The application according to claim 13, characterized in that, The hot pressing temperature is 170-240℃, the hot pressing time is 10-15 seconds / mm, and the maximum unit pressure is 3.0MPa.

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