Method for preserving bamboo and preserved bamboo

Abstract

The application discloses a bamboo material preservative treatment method and a preservative bamboo material. The method comprises the following steps: (1) soaking the bamboo material in hot water and then drying; (2) under light-proof conditions, treating the bamboo material treated in the step (1) by a vacuum impregnation method with a composite preservative, cleaning the surface of the bamboo material after the vacuum impregnation, and then treating the bamboo material under ultraviolet light; and (3) under natural light, preparing a polyvinyl alcohol-tannic acid film on the bamboo material treated under ultraviolet light in the step (2) by using a layer-by-layer self-assembly method. The composite preservative designed in the application can be solidified under ultraviolet light, and the loss of the preservative can be effectively prevented. Meanwhile, the polyvinyl alcohol-tannic acid film is introduced, and the gap caused by the volume shrinkage of the solidified composite preservative can be filled, so that the loss of the preservative is further reduced. Finally, the polyvinyl alcohol-tannic acid film used in the application also has a certain antibacterial effect, and is also beneficial to the bamboo material preservative.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bamboo preservation, and further relates to a bamboo preservation treatment method and preserved bamboo. BACKGROUND

[0002] Bamboo is an important forest resource, but in a humid and warm environment, untreated bamboo will be eroded by decay fungi due to its rich nutrients, and thus needs to be preserved.

[0003] Physical methods mainly include: (1) water immersion: fresh bamboo is soaked to remove part of the nutrients such as starch and sugar, and to fill the cells with free water to form a low-oxygen environment that is not conducive to the growth of mold, thereby inhibiting the growth and reproduction of mold. (2) Drying: through high-temperature drying, not only can the mold be killed by heating, but also the moisture in the bamboo can be reduced to lower the environmental humidity, thereby inhibiting the growth and reproduction of mold. (3) Steaming: heating and steaming to remove part of the nutrients such as starch and sugar to reduce the source of mold nutrition. The physical method for preventing mold on bamboo is mainly to change the internal environment of the bamboo to improve the mold prevention effect. The physical method is simple and low in cost, and the mold prevention effect is good in the short term, but it cannot guarantee that the bamboo will not be infected with mold again during production, storage and use in the future, and cannot maintain the effect for a long time. Therefore, in production practice, a method combining physical and chemical methods is mostly used.

[0004] Quaternary ammonium salt, copper and borate compounds have good preservation effect and are widely used all over the world. However, when the treated wood is wet or in contact with rainwater, the copper and boron in the wood will gradually be lost, resulting in a decrease in the preservation performance, and the lost preservatives are not easy to be degraded, which will cause harm to humans, animals and the ecological environment. How to enhance the fixation of preservatives in wood is a difficult problem to be solved in wood preservation research.

[0005] Therefore, it is necessary to develop a method for treating preserved bamboo to reduce the loss of chemical preservatives. SUMMARY

[0006] To solve the problems in the prior art, the present application provides a bamboo preservation treatment method and preserved bamboo. The composite preservative designed in the present application can be cured under ultraviolet light, thereby firmly locking the preservative and effectively preventing the loss of the preservative. Meanwhile, it is found that the composite preservative has a certain volume shrinkage when it is cured, and therefore a polyvinyl alcohol-tannin acid film is introduced to fill the gap caused by the volume shrinkage of the cured composite preservative, thereby further reducing the loss of the preservative. Finally, the polyvinyl alcohol-tannin acid film used in the present application also has a certain antibacterial effect, which is also beneficial to the preservation of bamboo.

[0007] The first aspect of the present application is to provide a bamboo preservative treatment method, the bamboo preservative treatment method comprising the following steps:

[0008] (1) After the bamboo is treated by hot water immersion, it is dried;

[0009] (2) Under light-free conditions, the composite preservative is treated with the bamboo treated in step (1) by vacuum infusion, after vacuum infusion, the surface of the bamboo is cleaned, and then it is placed under ultraviolet light for treatment;

[0010] (3) Under natural light, the bamboo treated under ultraviolet light in step (2) is used to prepare a polyvinyl alcohol-tannic acid film by layer-by-layer self-assembly method.

[0011] As a preferred embodiment, step (1),

[0012] The temperature of hot water immersion treatment is 70-90℃; and / or,

[0013] The time of hot water immersion treatment is 1-2h.

[0014] As a preferred embodiment, step (2),

[0015] The total weight of the composite preservative system is 100%, which comprises the following components:

[0016] The monomer is 40-55wt%; such as preferably 40, 50, 55wt%;

[0017] The photoinitiator is 2-5wt%; such as preferably 2, 3, 4, 5wt%;

[0018] The bisphenol A glycidyl ether dimethacrylate is 30-40wt%; such as preferably 30, 35, 40wt%;

[0019] The co-initiator is 1-5wt%; such as preferably 1, 2, 3, 4, 5wt%;

[0020] The solvent is 1-5wt%; such as preferably 1, 2, 3, 4, 5wt%;

[0021] The boric acid is 5-10wt%; such as preferably 5, 6, 7, 8, 9, 10wt%.

[0022] The present application is opened by the photoinitiator decomposition active free radical to open the double bond of polymerizable monomer, and is reacted by free radical polymerization mechanism. Before polymerization, the intermolecular force of monomer is Van der Waals force and hydrogen bond, and the intermolecular distance is 0.3-0.4nm; after polymerization, the double bond is opened to form covalent bond, and the distance is shortened to 0.154nm, thereby macroscopic volume shrinkage is generated, shrinkage stress is generated, the adhesive strength is affected, and Bis-GMA is newly introduced in the present application. Bis-GMA can form a three-dimensional spatial network structure when polymerized, so that the preservative can be better fixed and the loss of preservative can be reduced. Meanwhile, the rigid structure of the benzene ring on the Bis-GMA main chain can reduce the shrinkage of the preservative itself during curing, improve the contact strength with bamboo, and also help to reduce the loss of preservative.

[0023] As a preferred embodiment, the monomer is selected from at least one of methyl acrylate, methyl methacrylate, hydroxyethyl methacrylate (HEMA), hydroxyethyl acrylate, isobornyl methacrylate or isobornyl acrylate (IBOA); and / or,

[0024] The photoinitiator is selected from at least one of dibenzoyl peroxide, dilauryl peroxide, azobisisobutyronitrile, azobisisoheptyl nitrile, tert-butyl benzoyl peroxide or 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide.

[0025] As a preferred embodiment, the co-initiator is selected from at least one of N,N-dimethylamino methacrylate or p-dimethylamino benzoate; and / or,

[0026] The solvent is selected from at least one of alcohol solvents, preferably selected from at least one of ethanol or propanol.

[0027] In the technical scheme of the present application, boric acid is a preservative; the structural formula of Bis-GMA is:

[0028]

[0029] As a preferred embodiment, step (2),

[0030] When vacuum impregnation, the pressure is-0.08-0.1MPa, and the treatment time is 40-60min.

[0031] As a preferred embodiment, step (2),

[0032] The temperature of the treatment under ultraviolet light is not more than 20 degrees, and the treatment time is 30-60S. As a preferred embodiment, step (3),

[0033] The steps for preparing the polyvinyl alcohol-tannic acid film by using the layer-by-layer self-assembly method are as follows:

[0034] After the bamboo is soaked in the polyvinyl alcohol solution, it is cleaned and dried, and then is soaked in the tannic acid solution, cleaned and dried; the above steps are repeated for 2-4 times to obtain the polyvinyl alcohol-tannic acid film.

[0035] As a preferred embodiment, the concentration of the polyvinyl alcohol solution is 4-5 mg / mL.

[0036] The concentration of the tannic acid solution is 6-7 mg / mL.

[0037] The pH value of the polyvinyl alcohol solution and the tannic acid solution is independently adjusted to 2.5-3.

[0038] The second aspect of the present application is to provide a preserved bamboo treated by the method of the first aspect of the present application.

[0039] Compared with the prior art, the present application has the following advantages:

[0040] The composite preservative of the present application can be cured under ultraviolet light irradiation, thereby effectively preventing the loss of the preservative, and the method is simple and convenient to operate.

[0041] It is also found that the composite preservative has a certain volume shrinkage when it is cured, and therefore the polyvinyl alcohol-tannic acid film is introduced to fill the gap caused by the volume shrinkage of the cured composite preservative, thereby further reducing the loss of the preservative.

[0042] The polyvinyl alcohol-tannic acid film used in the present application also has a certain antibacterial effect, which is also beneficial to the preservation of bamboo. DETAILED DESCRIPTION

[0043] The present application will be specifically described below in combination with specific examples, and it is necessary to point out that the following examples are only used to further illustrate the present application and cannot be understood as limiting the protection scope of the present application. Some non-essential improvements and adjustments of the present application made by those skilled in the art according to the content of the present application still fall within the protection scope of the present application.

[0044] The bamboo used in the examples of the present application is all Phyllostachys pubescens.

[0045] Test method:

[0046] a. Loss: The bamboo sample is placed in a constant temperature and humidity chamber with a temperature of 20℃ and a relative humidity of 60% for 14 days, and then weighed, recorded as m1. The treated bamboo sample is weighed, recorded as m2. The calculation formula of the boron content in the treated sample is: λ=(m2-m1)×C×A (1)

[0047] wherein λ is the boron content in the treated sample (mg); m2 is the mass of the sample after vacuum infusion treatment (mg); m1 is the mass of the sample before vacuum infusion treatment (mg); C is the concentration of borate in the infusion solution (%); and A is the mass fraction of boron in the borate.

[0048] The samples were subjected to leaching test according to the American Wood Preservers Association Standard AWPA E11-06, and the water was changed after 6, 24, 48, 48, 48 h, respectively, for 14 days of continuous leaching, and 9 times of leaching water was collected for determining the boron leaching rate.

[0049] The boron leaching rate was calculated according to the following formula:

[0050] η = (B / λ) x 100% (2)

[0051] wherein η is the boron leaching rate (%); λ is the boron content in the untreated sample (mg); and B is the boron content in the leaching water (mg).

[0052] b. Shrinkage: determined according to the National Standard GB / T 1932-2009 "Wood Shrinkage Determination Method".

[0053] c. Corrosion resistance: 6 pieces of leached wood block samples were selected for each group for corrosion resistance test, and determined according to the Forestry Industry Standard LY / T 1283-2011 "Laboratory Test Method for Toxicity of Wood Preservatives to Corrosive Fungi".

[0054] Example 1

[0055] Preparation of the composite preservative:

[0056] A liquid composite preservative was prepared by mixing 50 parts of photopolymerizable monomer (containing 35 parts of isobornyl acrylate, 7 parts of hydroxyethyl methacrylate and 8 parts of isobornyl methacrylate), 3 parts of dibenzoyl peroxide, 35 parts of bisphenol A glycidyl ether dimethacrylate, 2 parts of co-initiator p-dimethylaminobenzoic acid ester, 3 parts of ethanol solvent, and 7 parts of boric acid under the conditions of vacuum degree -0.04 MPa, stirring speed 400 rpm, and light shielding for 1 hour until uniform, and the mixing temperature was 55°C.

[0057] Method for treating bamboo for preservation:

[0058] (1) The bamboo was soaked in hot water at 90°C for 1.2 h and then dried.

[0059] (2) Under the lightless condition, the composite preservative is used to treat the bamboo material treated in step (1) by vacuum impregnation, the vacuum impregnation condition is that the pressure is-0.08 MPa and the treatment time is 60 min; after the vacuum impregnation, the surface of the bamboo material is cleaned by a scraper, and then the bamboo material is placed under the ultraviolet light for treatment, the temperature for the treatment under the ultraviolet light is 20 degrees, and the treatment time is 30 seconds.

[0060] (3) Under the natural light, the bamboo material treated in step (2) is placed in a 5 mg / mL polyvinyl alcohol solution (the pH value is adjusted to 2.5 by hydrochloric acid) for immersion, then cleaned, dried, and then placed in a 7 mg / mL tannic acid solution (the pH value is adjusted to 2.5 by hydrochloric acid) for immersion, cleaned, and dried; the above sequence is repeated twice, and a polyvinyl alcohol-tannic acid film is prepared by using the layer-by-layer self-assembly method, and the bamboo material is treated.

[0061] Example 2

[0062] Preparation of the composite preservative:

[0063] 50 parts of photopolymerization monomers (containing 35 parts of isobornyl acrylate, 7 parts of hydroxyethyl methacrylate and 8 parts of isobornyl methacrylate), 3 parts of azobisisobutyronitrile, 32 parts of bisphenol A glycidyl ether dimethacrylate, 2 parts of assistant initiator p-dimethylaminobenzoic acid ester, 5 parts of ethanol solvent, and 8 parts of boric acid are mixed under the condition of-0.04 MPa vacuum degree, stirring at 400 rpm for 1 hour to uniformity, and the mixing temperature is 55℃, to obtain the liquid composite preservative.

[0064] Bamboo material treatment method:

[0065] (1) The bamboo material is soaked in hot water at 85℃ for 1.5 hours, and then dried.

[0066] (2) Under the lightless condition, the composite preservative is used to treat the bamboo material treated in step (1) by vacuum impregnation, the vacuum impregnation condition is that the pressure is-0.1 MPa and the treatment time is 50 min; after the vacuum impregnation, the surface of the bamboo material is cleaned by a scraper, and then the bamboo material is placed under the ultraviolet light for treatment, the temperature for the treatment under the ultraviolet light is 20 degrees, and the treatment time is 45 seconds.

[0067] (3) Under the natural light, the bamboo material treated in step (2) is placed in a 4 mg / mL polyvinyl alcohol solution (the pH value is adjusted to 2.5 by hydrochloric acid) for immersion, then cleaned, dried, and then placed in a 6 mg / mL tannic acid solution (the pH value is adjusted to 2.5 by hydrochloric acid) for immersion, cleaned, and dried; the above sequence is repeated four times, and a polyvinyl alcohol-tannic acid inner coating film is prepared by using the layer-by-layer self-assembly method, and the bamboo material is treated.

[0068] Example 3

[0069] Preparation of the composite preservative:

[0070] Using 45 parts of photopolymerization monomer (containing 32 parts of isobornyl acrylate, 6 parts of hydroxyethyl methacrylate and 7 parts of isobornyl methacrylate), 3 parts of azobisisobutyronitrile, 40 parts of bisphenol A glycidyl ether dimethacrylate, 2 parts of assistant initiator p-dimethylaminobenzoate, 5 parts of ethanol solvent; 5 parts of boric acid, mixed under vacuum degree-0.04 MPa, stirring at 400 rpm for 1 hour to uniformity, the mixing temperature is 55℃, to prepare the liquid composite preservative.

[0071] Bamboo preservative treatment method:

[0072] (1) Soak the bamboo in hot water at 90℃ for 1.5h, and then dry.

[0073] (2) Under the condition of light, the composite preservative is treated with the bamboo treated in step (1) by vacuum infusion, the vacuum infusion condition is-0.1 MPa, and the treatment time is 45 min; after vacuum infusion, the surface of the bamboo is cleaned by scraper, and then placed under ultraviolet light for treatment, the temperature of the ultraviolet light is 20 degrees, and the treatment time is 30S.

[0074] (3) After the bamboo treated in step (2) is placed in 5mg / mL polyvinyl alcohol solution (pH value is adjusted to 2.5 by hydrochloric acid) under natural light, it is soaked, washed, dried, and then placed in 6mg / mL tannic acid solution (pH value is adjusted to 2.5 by hydrochloric acid) for soaking, washing and drying; repeat the above sequence 3 times to prepare polyvinyl alcohol-tannic acid inner coating film by layer-by-layer self-assembly method, and complete the preservative treatment of the bamboo.

[0075] Example 4

[0076] Preparation of the composite preservative:

[0077] Using 45 parts of photopolymerization monomer (containing 32 parts of isobornyl acrylate, 6 parts of hydroxyethyl methacrylate and 7 parts of isobornyl methacrylate), 3 parts of azobisisobutyronitrile, 40 parts of bisphenol A glycidyl ether dimethacrylate, 2 parts of assistant initiator p-dimethylaminobenzoate, 5 parts of ethanol solvent; 5 parts of boric acid, mixed under vacuum degree-0.04 MPa, stirring at 400 rpm for 1 hour to uniformity, the mixing temperature is 55℃, to prepare the liquid composite preservative.

[0078] Bamboo preservative treatment method:

[0079] (1) Soak the bamboo in hot water at 90℃ for 1.5h, and then dry.

[0080] (2) Under the condition of avoiding light, the composite preservative is used to treat the bamboo material treated in step (1) by vacuum impregnation, the vacuum impregnation is carried out under the condition of-0.09 MPa for 50 min; after the vacuum impregnation, the surface of the bamboo material is cleaned by a scraper, and then the bamboo material is placed under ultraviolet light, the temperature of the ultraviolet light is 20 degrees, and the treatment time is 60 seconds.

[0081] (3) Under natural light, the bamboo material treated under ultraviolet light in step (2) is soaked in a 4.5 mg / mL polyvinyl alcohol solution (the pH value is adjusted to 2.5 by hydrochloric acid), cleaned, dried, and then soaked in a 6.5 mg / mL tannic acid solution (the pH value is adjusted to 2.5 by hydrochloric acid), cleaned, and dried; the above sequence is repeated three times, a polyvinyl alcohol-tannic acid inner coating film is prepared by using a layer-by-layer self-assembly method, and the bamboo material is treated.

[0082] Comparative Example 1

[0083] The prepared liquid composite preservative is basically the same as that in Example 1, and the only difference is that the bisphenol A glycidyl ether dimethacrylate is not added, and the same mass of the monomer in Example 1 is used instead of the bisphenol A glycidyl ether dimethacrylate to prepare the liquid composite preservative.

[0084] Then, the bamboo material is treated by using the same method as that in Example 1.

[0085] Comparative Example 2

[0086] The same composite preservative as that in Example 1 is used, and the bamboo material is treated by using the same method as that in Example 1, and the only difference is that the preparation of the polyvinyl alcohol-tannic acid film is not performed.

[0087] The bamboo material treated in each example and comparative example is subjected to performance determination, and the results are shown in Table 1.

[0088] Table 1

[0089]

[0090] As shown in Table 1, compared with Comparative Example 1, if the bisphenol A glycidyl ether dimethacrylate is not added in the composite preservative, the treatment effect of the bamboo material is reduced.

[0091] As compared with Example 1 and Comparative Example 2, if the bamboo material treated by the composite preservative is not covered by the polyvinyl alcohol-tannic acid film, the treatment effect of the bamboo material is reduced.

[0092] In addition, within the range of the conditions of the ultraviolet light treatment defined in the example, the treatment effect of the bamboo material is the best.

[0093] The present application has been described in detail by reference to particular embodiments and illustrative examples, but these are not intended to limit the present application to the details described herein. Various modifications and equivalents can occur to one skilled in the art without departing from the spirit and scope of the present application, and it is understood that the present application is intended to cover what falls within the scope of the appended claims.

Claims

1. A method for treating bamboo against decay, characterized by, The preservative treatment method of the bamboo material comprises the following steps: (1) soaking the bamboo material in hot water, and then drying; (2) treating the bamboo material treated in step (1) by vacuum impregnation with a composite preservative under light-proof condition, cleaning the surface of the bamboo material after vacuum impregnation, and then treating the bamboo material under ultraviolet light; step (2), the composite preservative comprises the following components in terms of the total weight of the composite preservative being 100%: the monomer is 40-55 wt%; the photoinitiator is 2-5 wt%; bisphenol A glycidyl ether dimethacrylate is 30-40 wt%; the assistant initiator is 1-5 wt%; the solvent is 1-5 wt%; boric acid is 5-10 wt%; the monomer is selected from at least one of methyl acrylate, methyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, isobornyl methacrylate or isobornyl acrylate; the photoinitiator is selected from at least one of dibenzoyl peroxide, dilauryl peroxide, azobis isobutyronitrile, azobis isoheptyl nitrile, tert-butyl peroxybenzoate or 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide; the assistant initiator is selected from at least one of N,N-dimethylamino methacrylate or p-dimethylamino benzoate; and the solvent is selected from an alcohol solvent; (3) preparing a polyvinyl alcohol-tannic acid film on the bamboo material treated under ultraviolet light in step (2) by using a layer-by-layer self-assembly method.

2. The preservative treatment method of the bamboo material according to claim 1, wherein: in step (1), the temperature of the hot water soaking treatment is 70-90 °C; and / or the time of the hot water soaking treatment is 1-2 h.

3. The preservative treatment method of the bamboo material according to claim 1, wherein: the solvent is selected from at least one of ethanol or propanol.

4. The preservative treatment method of the bamboo material according to claim 1, wherein: in step (2), the vacuum impregnation is performed at a pressure of -0.08-0.1 MPa for 40-60 min.

5. The preservative treatment method of the bamboo material according to claim 1, wherein: in step (2), the temperature of the treatment under ultraviolet light is not more than 20 °C, and the time of the treatment is 30-60 s.

6. The preservative treatment method of the bamboo material according to claim 1, wherein: in step (3), the step of preparing the polyvinyl alcohol-tannic acid film by using the layer-by-layer self-assembly method comprises the following steps: immersing the bamboo material treated under ultraviolet light in a polyvinyl alcohol solution, cleaning, drying, immersing in a tannic acid solution, cleaning, and drying; repeating the above steps for 2-4 times to obtain the polyvinyl alcohol-tannic acid film.

7. The preservative treatment method of the bamboo material according to claim 6, wherein: the concentration of the polyvinyl alcohol solution is 4-5 mg / mL; the concentration of the tannic acid solution is 6-7 mg / mL; the pH value of the polyvinyl alcohol solution and the tannic acid solution is independently adjusted to 2.5-3.

8. A preservative bamboo material treated by the method according to any one of claims 1-7.

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