Melamine urea-formaldehyde resin composite borate one-time impregnation of solid wood preservative solution, impregnated wood and irradiation strengthening process of impregnated wood

Abstract

The present application relates to a kind of melamine urea-formaldehyde resin composite boron salt one-time impregnation solid wood preservative liquid, impregnated wood and the irradiation strengthening process of impregnated wood, first, select boron, calcium (or copper) compound aqueous solution as impregnation liquid, or can contain boron, calcium ion (or copper ion) and melamine urea-formaldehyde resin simultaneously according to specific process preparation mixed solid wood impregnation liquid;Then wood is treated by vacuum pressurized impregnation, impregnated wood can be irradiated according to the need of specific dose with electron beam or other radiation source in humid state;Finally, impregnated wood is dried and treated to obtain finished product;According to the need of selection calcium-boron formula, then colorless preservative liquid of one-time impregnation can be achieved, copper-boron formula then achieves the one-time impregnation preservative liquid of better preservative effect but color.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wood preservation, in particular to a melamine urea-formaldehyde resin composite borate one-time impregnation solid wood preservative solution, impregnated wood and an irradiation strengthening process for the impregnated wood. BACKGROUND

[0002] Currently, wood preservation mainly includes oil-based preservation, water-based preservation, gas preservation and oil-carrying preservation. Among them, the water-based preservation scheme is the most widely used due to its low cost, easy use and environmental protection. The formula containing high-toxicity components such as chromium and arsenic in the water-based preservation scheme has been gradually restricted or prohibited in various countries. The common alternative formula is a low-toxicity copper or boron-containing compound for mammals. Boron-based preservatives are widely used due to their advantages of not affecting the original color of wood, strong penetration and low price. However, the main problem of the water-based preservation scheme is that the effective components generally have poor anti-washing performance.

[0003] For the problem of easy washing of water-based preservatives, the current general method is to add multifunctional chelating agents or corresponding compounds that can induce precipitation, such as protein, ethylene glycol, metal salt, quaternary ammonium salt and other chemical additives combined with borate. Essentially, it is to promote the formation of chelates or precipitates of preservative components such as copper or boron that are difficult to dissolve in water by chemical means to inhibit the diffusion of preservative components and improve their anti-washing performance. However, the metal ion-borate scheme often cannot be treated by one-time impregnation, otherwise, in order to ensure dissolution, the borate concentration is too dilute, or the metal ion and borate will form a difficult-to-dissolve precipitate before impregnation, which cannot be impregnated. Therefore, the metal ion-borate anti-washing scheme usually needs to separate the preservative components and the precipitate components, and use two-time or multiple-time impregnation treatment, which leads to an increase in cost. The scheme of adding small-molecule organic chelating agents often has poor anti-washing effect due to the problem of ineffective activation of grafting sites.

[0004] In addition, a wood impregnation treatment scheme using water-soluble resin (such as phenol formaldehyde resin) to complex borate has also been proposed, that is, the three-dimensional cross-linked network formed by impregnating resin thermal curing blocks the pores of wood, and locks the boron inside the wood. The mechanism is mainly to prevent external water from penetrating into the wood and causing the migration of active components by physical isolation. However, it is found in actual experiments that even if the impregnated wood is treated by hot drying at a temperature of 100°C, the internal resin cannot be completely cured due to the influence of wood being a poor thermal conductor, which will cause part of the preservative solution to be lost to the external water body with the uncured resin. If the temperature is increased on the basis of the original, it is easy to cause the wood to crack. Therefore, the solid wood impregnation system needs a more solution condensation formula. SUMMARY

[0005] To solve the above problems, the application provides a melamine urea-formaldehyde resin composite borate one-time impregnation solid wood preservative solution, impregnated wood and an irradiation strengthening process of the impregnated wood, mainly utilizes the chelation and steric hindrance of melamine urea-formaldehyde resin, and the characteristics that electron beam irradiation increases active chelation sites and uniformly penetrates the resin, so that the above problems of water-based preservatives can be effectively solved or slowed down. In addition, the process has low radiation dose, simple operation, high efficiency and environmental protection, and can provide colorless or colored one-time impregnated preservative wood products according to needs.

[0006] In order to achieve the above technical purposes, the technical scheme adopted by the application is:

[0007] A melamine urea-formaldehyde resin composite borate one-time impregnation solid wood preservative solution, by weight, comprising 1-10 parts of a borate composite preservative solution and 1-20 parts of melamine urea-formaldehyde resin.

[0008] The preparation method of the melamine urea-formaldehyde resin composite borate one-time impregnation solid wood preservative solution comprises the following steps:

[0009] Mixing the borate composite preservative solution and the melamine urea-formaldehyde resin, stirring for 1-30 minutes, to obtain the melamine urea-formaldehyde resin composite borate one-time impregnation solid wood preservative solution.

[0010] As a possible implementation, further, the preparation method of the borate composite preservative solution comprises the following steps:

[0011] A. Selecting borate and water, mixing and stirring for 1-30 minutes to prepare a solution;

[0012] B. Adding calcium salt to the above solution, stirring for 1-30 minutes, to obtain a borate and calcium salt composite preservative solution.

[0013] As a possible implementation, further, the borate includes borax and boric acid, wherein the borax and boric acid are compounded in a mass ratio of 1:1-100.

[0014] The calcium salt is one or more of (anhydrous) calcium chloride, (anhydrous) calcium nitrate, (anhydrous) calcium sulfate or other soluble calcium salts.

[0015] As a more preferred implementation, preferably, the mass ratio of borate, calcium salt and water in the borate composite preservative solution is (0.1-3):(0.1-3):(5-100).

[0016] As a possible implementation, further, the calcium salt is replaced by a water-soluble copper salt, and the water-soluble copper salt is selected from one or more of copper sulfate, copper nitrate, copper chloride, commercially available quaternary amine copper stock solution and other water-soluble copper salts.

[0017] As a possible implementation, further, the preparation method of the melamine urea-formaldehyde resin comprises the following steps:

[0018] a. The pH value of the industrial formaldehyde solution (30-41%) is adjusted to 7-9, and 10-100% of the total urea is added to the above solution, and the temperature is raised to 40-65°C, and the pH value is maintained at 7-9 during the temperature rising process;

[0019] b. When the temperature reaches 60-65°C, melamine is added to the above mixture, and the temperature is raised to 60-85°C, and after the temperature reaches, the stabilizer and the remaining urea are added;

[0020] c. After 10-60 minutes of heat preservation, the heating is turned off, ammonia water is added, and the discharge is waited for 1-30 minutes.

[0021] As a possible implementation, further, the stabilizer is selected from any one of malt dextrin, modified starch, low molecular weight polyvinyl alcohol, and polyethylene glycol;

[0022] The mass ratio of the formaldehyde solution, urea, melamine, stabilizer, and ammonia water is (0.5-2.5):(0-1.0):(0-1.0):(0-0.3):(0-0.3).

[0023] The application also provides a preparation method of melamine urea-formaldehyde resin composite borate impregnated wood, comprising the following steps:

[0024] 1. The raw wood is cut according to the required size and placed in a gradient temperature or constant temperature drying treatment at 30-120°C, and the gradient or constant temperature drying time is maintained for 1-120 hours, and then a conventional curing treatment is performed, thereby obtaining a treated wood; wherein the raw wood is one or more of poplar, scots pine, paulownia, and radiata pine or other suitable impregnated wood.

[0025] 2. The treated wood is placed in an impregnation pressurization instrument, the vacuum degree in the instrument is maintained at -0.1 to -0.05 MPa for 1-100 minutes, the valve of the instrument is opened to suck the above-mentioned melamine urea-formaldehyde resin composite borate one-time impregnation solid wood preservative solution into the instrument, and the booster pump is opened, the pressure value is 0-10 MPa, the impregnation time is maintained for 5-120 minutes, and the melamine urea-formaldehyde resin composite borate impregnated wood is obtained after pressure relief.

[0026] The application further provides an irradiation strengthening process of melamine urea-formaldehyde resin composite borate impregnated wood, comprising the following steps:

[0027] I. The melamine urea-formaldehyde resin composite borate impregnated wood prepared by the above preparation method is subjected to irradiation treatment, and the radiation dose is set to 0-50 KGy.

[0028] II) after irradiation, the impregnated wood is subjected to gradient temperature drying, first placed at 40-80 DEG C for 1-120 hours, then the temperature is increased to 80-130 DEG C and maintained for 1-120 hours, and finally 0-120 hours of natural cooling to near room temperature to obtain the impregnated wood product.

[0029] As a preferred embodiment, preferably, the radiation source used in the irradiation in step I) is selected from electron beam radiation source or isotope radiation source; and the impregnated wood product obtained in step II) is further subjected to health preservation and stress release.

[0030] Compared with the prior art, the application has the beneficial effects that:

[0031] 1) In the application, the water-based preservative liquid system of boron salt composite resin can be stably present in the presence of calcium (precipitant) or copper ion (preservative and precipitant), and is ensured to be clear and transparent within a certain storage period, so that the process can adopt one-step impregnation method. The composite impregnation liquid can ensure that the preservative components (especially the boron content) in each cubic meter of impregnated wood reach or exceed the national standard of C2 type preservative wood.

[0032] 2) In the application, the thermal curing temperature of melamine urea-formaldehyde resin is lower and easier to condense, which can prevent the cracking or deformation of solid wood caused by high temperature curing, and the resin cost is low. The colorless calcium-boron formula does not affect the original color of the wood; the colored copper-boron formula has better preservative effect.

[0033] 3) Because the melamine component is more sensitive to radiation, the formula in the application can significantly improve the final curing effect of the resin at a low dose (10-20 kGy) of electron beam or isotope source irradiation, and provide more active sites to strengthen the fixation of preservative components.

[0034] 4) The irradiation process in the application has penetration ability, can process a certain thickness of plate, and is more uniform than microwave or ultrasonic or strong light, and is also more convenient to implement industrially. If the electron beam scheme is adopted, the irradiation link has super-high efficiency.

[0035] 5) The preservative liquid provided by the application can maintain long stability (long storage time) and can be stored for 2-10 weeks. DETAILED DESCRIPTION

[0036] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0037] The present application provides a process for irradiation strengthening of melamine urea formaldehyde resin composite borate impregnated wood, comprising the following steps:

[0038] I) irradiating the melamine urea formaldehyde resin composite borate impregnated wood using an electron beam radiation source or an isotope radiation source, with a radiation dose of 0-50 KGy;

[0039] II) gradient temperature drying the irradiated impregnated wood, first at 40-80℃ for 1-120 hours, then increasing the temperature to 80-130℃ for 1-120 hours, and finally naturally cooling to room temperature for 0-120 hours to obtain the impregnated wood product, which can be further subjected to stress relief.

[0040] In the present application, electron beam or isotope radiation technology can be used as needed to enhance the uniform curing degree of melamine urea formaldehyde resin through various mechanisms, and to better chelate the preservative components with the wood body through the principle of increasing a large number of active sites by radiation, thereby improving the anti-leaching performance.

[0041] The preparation method of the melamine urea formaldehyde resin composite borate impregnated wood comprises the following steps:

[0042] 1) cutting the logs to the required size and gradient temperature or constant temperature drying at 30-120℃ for 1-120 hours, and then performing conventional stress relief treatment to obtain the treated wood; wherein,

[0043] 2) Put the processing material into the impregnation pressurized instrument, and maintain the vacuum degree in the instrument at -0.1 to -0.05 Mpa, keep the vacuum degree for 1 to 100 minutes, open the valve of the instrument to suck the melamine urea-formaldehyde resin composite borate one-time impregnation solid wood preservative solution into the instrument, at the same time, open the pressure pump, the pressure value is 0 to 10 MPa, maintain the impregnation time for 5 to 120 minutes, and the melamine urea-formaldehyde resin composite borate impregnated wood is obtained after pressure relief.

[0044] In the above preparation method, the raw wood can be one or more of poplar, scots pine, paulownia and radiata pine or other suitable impregnated wood.

[0045] The preparation method of the above-mentioned melamine urea-formaldehyde resin composite borate one-time impregnation solid wood preservative solution comprises the following steps:

[0046] Mix 1 to 10 parts of the borate composite preservative solution with 1 to 20 parts of melamine urea-formaldehyde resin, stir for 1 to 30 minutes, and the melamine urea-formaldehyde resin composite borate one-time impregnation solid wood preservative solution is obtained.

[0047] The preparation method of the above-mentioned melamine urea-formaldehyde resin composite borate one-time impregnation solid wood preservative solution comprises the following steps:

[0048] A. Select borate and water to mix and stir for 1 to 30 minutes to form a solution;

[0049] B. Add calcium salt to the above-mentioned solution, stir for 1 to 30 minutes, and the borate and calcium salt composite preservative solution is obtained. The colorless calcium-borate salt composite preservative solution does not affect the original color of the wood.

[0050] The above-mentioned borate includes borax and boric acid, wherein the borax and boric acid are compounded in a mass ratio of 1:1 to 100; the calcium salt is one or more of anhydrous calcium chloride, anhydrous calcium nitrate, anhydrous calcium sulfate or other soluble calcium salts; the mass ratio of borate, calcium salt and water in the borate composite preservative solution is (0.1-3):(0.1-3):(5-100).

[0051] In the above preparation method, the calcium salt can be replaced by water-soluble copper salt, such as one or more of copper sulfate, copper nitrate, copper chloride, commercially available quaternary amine copper stock solution, etc. The obtained preservative solution shows the blue color of copper salt, and the impregnated wood product shows the blue-black color of copper salt, but has better preservative performance.

[0052] In the above preparation method, the calcium or copper salt can be separately configured as an aqueous solution for standby, which is more convenient for adjusting the concentration of the formula during the industrial implementation process.

[0053] The preparation method of the above-mentioned melamine urea-formaldehyde resin comprises the following steps:

[0054] a. Adjust the pH value of industrial formaldehyde solution (volume ratio 30-41%) to 7-9, add urea accounting for 10-100% of the total urea amount to the above solution, and raise the temperature to 40-65°C, maintaining pH 7-9 during the temperature rising process;

[0055] b. When the temperature reaches 60-65°C, add melamine to the above mixture, and raise the temperature to 60-85°C again. After the temperature reaches, add stabilizer (malt dextrin, or modified starch, or low molecular weight polyvinyl alcohol or polyethylene glycol, etc.) and the remaining urea;

[0056] c. After maintaining for 10-60 minutes, turn off the heating and add ammonia water. Wait for 1-30 minutes to discharge.

[0057] In the formula, the mass ratio of formaldehyde solution, urea, melamine, stabilizer, and ammonia water is (0.5-2.5):(0-1.0):(0-1.0):(0-0.3):(0-0.3).

[0058] Example 1:

[0059] Adjust the pH value of 400 parts of formaldehyde solution to 8.0, add 150 parts (60% of the total amount) of urea to the above solution, and raise the temperature to 60°C, maintaining about pH 8.0 during the process. After the temperature reaches 60°C, add 30 parts of melamine, and raise the temperature to 85°C again. During the temperature rising process, wait for about 15 minutes, and add the remaining 100 parts of urea and 20 parts of malt dextrin. Maintain 85°C constant temperature for 25 minutes after stirring, turn off the heating, add 12 parts of concentrated ammonia water, and wait for 30 minutes to discharge. After cooling to room temperature, the melamine urea-formaldehyde resin is obtained. Mix 2.5 parts of borax, 2.5 parts of boric acid, 3.5 parts of anhydrous calcium chloride, and 50 parts of water to obtain a boron and calcium salt preservative solution. Mix the prepared boron salt preservative solution with the melamine urea-formaldehyde resin at a mass ratio of 0.6:1, and stir for 30 minutes to obtain a colorless formula of melamine urea-formaldehyde resin composite boron salt. Cut the radiata pine into appropriate size and dry at 50-70°C for 10-24 hours to obtain dried raw wood. Place the dried raw wood in an impregnation and pressurization instrument, maintain the vacuum degree in the instrument at -0.1 Mpa for 20 minutes, open the valve of the instrument to suck the colorless formula of melamine urea-formaldehyde resin composite boron salt into the instrument, and open the booster pump at the same time. The pressure value is 0.1-0.2 MPa, and the impregnation time is maintained for 20 minutes. After pressure relief, the excess glue solution of the impregnated wood is extracted or the wood is taken out and drained for half an hour. Use an electron beam radiation source to irradiate the above-mentioned wet impregnated wood at 20 KGy. Place the irradiated sample in 50-70°C for 24 hours of drying treatment, then increase the temperature to 100°C and maintain for 24-48 hours of drying time. After drying, naturally cool for 24 hours to obtain the finished product. The subsequent curing can continue.

[0060] In this embodiment, the effective component boron compound (calculated as boron trioxide) in the finished preservative-treated wood product was measured to be approximately 6.2 kg per cubic meter, and the compressive strength along the grain was approximately 80 MPa.

[0061] Comparative Example 1:

[0062] Compared with Example 1, Comparative Example 1 was prepared in the same way as Example 1, except that melamine urea-formaldehyde resin was replaced with water in an equal mass ratio.

[0063] The comparative example shows that the effective boron compound (calculated as boron trioxide) content in the preservative-treated wood is approximately 1.5 kg per cubic meter, and the compressive strength along the grain is approximately 40 MPa.

[0064] Comparative Example 2:

[0065] Compared with Example 1, Comparative Example 2 was prepared in the same way as Example 1, except that the colorless impregnated wood with melamine urea-formaldehyde resin composite boron and calcium salt was not subjected to electron beam irradiation.

[0066] The comparative example shows that the effective boron compound (calculated as boron trioxide) loading in the preservative-treated wood is approximately 6.2 kg per cubic meter, and the compressive strength along the grain is approximately 75 MPa.

[0067] Comparative Example 3:

[0068] Compared with Example 1, Comparative Example 3 was prepared in the same way except that the electron beam radiation dose was set to 50 KGy.

[0069] The comparative example shows that the effective boron compound (calculated as boron trioxide) content in the preservative-treated wood is approximately 6.2 kg per cubic meter, and the compressive strength along the grain is approximately 74 MPa.

[0070] Test results show that the effective component loading of the preservative-treated wood in Examples 1, 1, and 3 is significantly better than that in Comparative Example 1. Example 1 exhibits the best performance in parallel-grain compressive strength. It overcomes the limitations of traditional boron-calcium salt composites, which require a two-stage impregnation method, by meeting or exceeding the national standard for Class C2 preservative-treated wood while also improving its mechanical strength. Excessive radiation doses can negatively impact mechanical properties and increase costs. In the above test environments, the optimal radiation dose is approximately 10–30 kGy. Different wood species and variations in the treatment process may result in different numerical values, but these do not affect the conclusion that appropriate radiation dose treatment can enhance the mechanical properties of impregnated wood.

[0071] If the color of the finished product is not a concern, water-soluble copper salts can be used instead of calcium salts, as copper salts are both a corrosion inhibitor and a boron precipitant, which can further improve the corrosion resistance.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. An irradiation strengthening process for melamine-urea-formaldehyde resin composite boron salt impregnated wood, characterized in that, Includes the following steps: I) Irradiate wood impregnated with melamine urea-formaldehyde resin composite boron salt, with the radiation dose set to 0~50KGy; II) The irradiated impregnated wood is dried by gradient heating. First, it is placed at 40~80℃ for 1~120 hours for drying. Then, the temperature is increased to 80~130℃ and maintained for 1~120 hours for drying. Finally, it is naturally cooled to near room temperature for 0~120 hours to obtain the finished impregnated wood. The preparation method of the melamine-urea-formaldehyde resin composite boron salt impregnated wood includes the following steps: 1) Cut the logs into the required size and place them in a temperature range of 30~120℃ for gradient heating or constant temperature drying. Each gradient or constant temperature drying time is maintained at 1~120 hours. After that, perform conventional curing treatment to obtain the treated wood. 2) Place the treated material in an impregnation and pressurization instrument, and maintain the vacuum degree inside the instrument at -0.1~-0.05Mpa for 1~100 minutes. Open the instrument valve to draw the melamine urea-formaldehyde resin composite boron salt impregnation solid wood preservative liquid into the instrument. At the same time, turn on the booster pump with a pressure value of 0~10MPa and maintain the impregnation time for 5~120 minutes. After depressurization, the melamine urea-formaldehyde resin composite boron salt impregnated wood is obtained. The melamine urea-formaldehyde resin composite boron salt one-time impregnation solid wood preservative liquid, by weight, includes 1 to 10 parts of boron salt composite preservative liquid and 1 to 20 parts of melamine urea-formaldehyde resin. The preparation method of the melamine-urea-formaldehyde resin composite boron salt single-impregnation solid wood preservative liquid includes the following steps: The boron salt composite preservative solution is mixed with melamine urea-formaldehyde resin and stirred for 1 to 30 minutes to obtain the melamine urea-formaldehyde resin composite boron salt one-time impregnation solid wood preservative solution. The preparation method of the boron salt composite anticorrosive liquid includes the following steps: A. Prepare a solution by mixing boron salt with water and stirring for 1-30 minutes; B. Add calcium salt to the above solution and stir for 1-30 minutes to obtain a boron and calcium salt composite preservative solution. The boron salt includes borax and boric acid, wherein borax and boric acid are compounded in a mass ratio of 1:1 to 100; the calcium salt is one or more of anhydrous calcium chloride, anhydrous calcium nitrate, anhydrous calcium sulfate, or other soluble calcium salts; the mass ratio of boron salt, calcium salt, and water in the boron salt composite anticorrosive liquid is (0.1-3):(0.1-3):(5-100).

2. The irradiation strengthening process for melamine-urea-formaldehyde resin composite boron salt impregnated wood according to claim 1, characterized in that, The calcium salt is replaced with a water-soluble copper salt, wherein the water-soluble copper salt is selected from one or more of copper sulfate, copper nitrate, copper chloride, and commercially available quaternary ammonium copper stock solution.

3. The irradiation strengthening process for melamine-urea-formaldehyde resin composite boron salt impregnated wood according to claim 1, characterized in that, The preparation method of the melamine-urea-formaldehyde resin includes the following steps: a. Adjust the pH of an industrial formaldehyde solution with a volume ratio of 30-41% to 7-9, add urea accounting for 10-100% of the total urea to the above solution, and raise the temperature to 40-65℃, maintaining the pH at 7-9 during the heating process. b. When the temperature reaches 60~65℃, add melamine to the mixture and raise the temperature to 60~85℃. After the temperature is reached, add stabilizer and the remaining urea. c. After keeping warm for 10-60 minutes, turn off the heating, add ammonia water, and wait 1-30 minutes before discharging.

4. The irradiation strengthening process for melamine-urea-formaldehyde resin composite boron salt impregnated wood according to claim 3, characterized in that, The stabilizer is selected from any one of maltodextrin, modified starch, low molecular weight polyvinyl alcohol, and polyethylene glycol. The mass ratio of formaldehyde solution, urea, melamine, stabilizer, and ammonia is (0.5-2.5):(0-1.0):(0-1.0):(0-0.3):(0-0.3).

5. The irradiation strengthening process for melamine-urea-formaldehyde resin composite boron salt impregnated wood according to claim 1, characterized in that, In step I), the radiation source used for irradiation is either an electron beam radiation source or an isotope radiation source; in step II), the impregnated wood product is further cured to release stress.