CN115558341B

CN115558341B - Hydrophobic paint for wood and preparation method and use method thereof

Info

Publication number: CN115558341B
Application number: CN202211128466.0A
Authority: CN
Inventors: 黄腾华; 王军锋; 宋恋环; 雷福娟; 彭晋达
Original assignee: Guangxi Zhuang Autonomous Region Forestry Research Institute
Current assignee: Guangxi Zhuang Autonomous Region Forestry Research Institute
Priority date: 2022-09-16
Filing date: 2022-09-16
Publication date: 2023-06-23
Anticipated expiration: 2042-09-16
Also published as: CN115558341A

Abstract

The embodiment of the application discloses a hydrophobic paint for wood, a preparation method and a use method thereof, wherein the paint comprises a dispersing agent and nano silicon dioxide particles dispersed in the dispersing agent, and the main component of the dispersing agent is hemicellulose; or the main component of the dispersing agent is a mixture of hemicellulose and long-chain anhydride modified hemicellulose. Hemicellulose has good agglomeration performance, amphipathy performance and dispersibility, so that the hemicellulose aqueous solution used as the dispersion liquid of the hydrophobic coating has the comprehensive advantages of degradability, safety, environmental protection, relatively good coating adhesion effect, lower manufacturing cost and simple process, and has the application prospect of forming industrialization in the wood processing field.

Description

Hydrophobic paint for wood and preparation method and use method thereof

Technical Field

The invention relates to the technical field of hydrophobic coating, in particular to a hydrophobic coating for film forming modification of the surface of wood; the invention also relates to a preparation method and a use method of the hydrophobic paint for wood.

Background

As a natural porous material, the hydrophilicity of wood makes it susceptible to moisture expansion, drying shrinkage, deformation, and even mildew and decay caused by changes in environmental humidity. In the prior art, modifying means for reducing the hydrophilicity of wood are abundant, and nano silicon dioxide is piled on the surface of wood to form a hydrophobic surface (namely, a surface with a water contact angle larger than 90 degrees) or a super-hydrophobic surface (namely, a surface with a water contact angle larger than 150 degrees and a sliding angle smaller than 10 degrees) which is one common method. The principle is that the nano silicon dioxide has lower surface energy, and can form a micro-nano structure with certain roughness on the surface of the wood, so that the surface of the wood meets two factors forming a hydrophobic or super-hydrophobic surface, namely a low surface energy and micro-nano rough structure. For example, in the chinese patent database, the publication number CN105599077a, the invention patent application entitled "a method for preparing super-hydrophobic wood based on sol-gel method" describes the following technical scheme: the nano silicon dioxide sol subjected to hydrophobic modification is coated on the surface of wood by adopting an impregnation or spraying process, and then the super-hydrophobic film layer is formed by drying in an oven. According to the technical scheme, the problems of mechanical property loss, environmental pollution and the like existing in the traditional thermal modification and chemical modification are solved, however, the film layer formed by drying the nano silicon dioxide sol has poor adhesion effect with the wood surface, and the film layer is easy to fall off along with the time, so that the time for providing hydrophobic protection for the wood surface is short.

In the Chinese patent database, the publication number is CN103448116A, and the following technical scheme is recorded in the patent application of the invention named as a method for improving the mechanical stability of super-hydrophobic wood: firstly, immersing wood in an epoxy resin solution to form an epoxy resin bottom layer on the surface of the wood, then immersing the wood with the epoxy resin bottom layer in a submicron silicon dioxide solution modified by a coupling agent, taking out and drying, and finally immersing the wood in an OTS ethanol solution, taking out and drying to form the superhydrophobic film layer. In the Chinese patent database, the publication number is CN105563577A, and the following technical scheme is recorded in the invention patent application with the name of "a method for improving the mechanical stability of a hydrophobic film on the surface of wood: firstly, wood is immersed in an epoxy resin solution to form an epoxy resin bottom layer on the surface of the wood, then hydrophobic nano silicon dioxide particles/epoxy resin/triethoxy-1H, 2H-heptadecafluorodecylsilane organic-inorganic composite coating solution is prepared, the solution is coated on the epoxy resin bottom layer through an immersion or spraying process, and finally, the super-hydrophobic film layer is formed by drying. According to the technical scheme, the adhesion effect of the super-hydrophobic film layer and the wood surface can be improved through the crosslinking between the epoxy resin in the film coating solution and the epoxy resin bottom layer on the wood surface and the effect of the coupling agent, however, most of synthetic adhesives are petroleum-based chemicals, petroleum resources are required to be consumed, natural degradation is difficult, and the environment friendliness of the wood as renewable resources can be reduced when the wood is treated. At the same time, fluorinated compounds can cause environmental pollution and safety hazards in production, as well as increased production costs.

In the Chinese patent database, the publication number is CN110499073A, and the following technical scheme is recorded in the patent application of the invention, namely a method for preparing the super-hydrophobic coating by modifying nano cellulose and nano particles serving as raw materials in an aqueous solution by using a fluorine-free modifier: firstly, loading a coupling agent (gamma-aminopropyl triethoxysilane) into deionized water to prepare a modified nano cellulose solution, dispersing nano particles (nano silicon dioxide particles) into the deionized water, preparing a modified silicon dioxide solution by promoting dispersion through hexadecyl trimethoxy silane and formic acid, mixing the modified nano cellulose solution and the modified silicon dioxide solution to obtain a super-hydrophobic coating, and finally, spraying the super-hydrophobic coating on a substrate to form a super-hydrophobic film layer. According to the technical scheme, the nano cellulose is used as a raw material to replace a synthetic adhesive, so that the environmental hazard and the potential safety hazard in production are reduced, but in actual operation, the raw material of the nano cellulose is expensive, and the technical scheme is difficult to form industrialized application in the field of wood processing.

Disclosure of Invention

The invention aims to at least overcome one of the technical problems, and provides a coating for the hydrophobic modification of wood, and simultaneously, the invention also provides a preparation method and a modification treatment method of the hydrophobic coating for wood.

To achieve the above object, a first embodiment of the present invention provides a hydrophobic paint for wood, the paint comprising a dispersant, and nano silica particles dispersed in the dispersant, wherein a main component of the dispersant is hemicellulose, or a mixture of hemicellulose and long chain anhydride modified hemicellulose.

Preferably, in the coating material, the ratio of the concentration of the main component to the concentration of the nano silica particles is 1:1.

Preferably, the long-chain anhydride modified hemicellulose is dodecenyl succinic anhydride graft modified hemicellulose.

Preferably, in the paint, the dispersant is an aqueous solution of the main component.

In order to achieve the above object, a second embodiment of the present invention provides a method for preparing a hydrophobic paint for wood, comprising a preparation process of a dispersant and a process of a mixing process, wherein,

the preparation process of the dispersing agent is a process of dissolving a main component in water under stirring to obtain the dispersing agent, wherein the main component is hemicellulose or a mixture of hemicellulose and long-chain anhydride modified hemicellulose;

the step of mixing is a step of dispersing the nano silica particles in the dispersing agent while stirring to obtain the coating material.

Preferably, the long-chain anhydride modified hemicellulose is prepared through a hemicellulose modification process, specifically, the hemicellulose is subjected to esterification reaction with a hemicellulose modifier in an alkaline environment, wherein the hemicellulose modifier is a dodecenyl succinic anhydride reagent.

Preferably, the hemicellulose modifying step is to dissolve hemicellulose in a solvent at 58-62 ℃, then cool the solvent in which the hemicellulose is dissolved, and add a catalyst and the hemicellulose modifier to the solvent after the temperature of the solvent is reduced to 48-52 ℃.

Preferably, the molar ratio between the amount of hemicellulose modifier and the amount of hemicellulose to be modified is (0.60-0.80): 1.

Preferably, the solvent is dimethyl sulfoxide solvent, and the catalyst is 4-dimethylaminopyridine powder.

To achieve the above object, a third embodiment of the present invention provides a method for using a hydrophobic paint for wood, the paint including a dispersant, and nano silica particles dispersed in the dispersant, wherein a main component of the dispersant is hemicellulose, or a mixture of hemicellulose and long chain anhydride modified hemicellulose; soaking the wood to be treated in the paint for 18-72 h, and then finishing the drying of the wood and the paint coating on the surface of the wood within 35 min.

By the product and the method, compared with the prior art, the invention has the beneficial effects that:

1. hemicellulose has good agglomeration performance, amphiphilicity (nano silicon dioxide and wood) performance and dispersibility, so that the hemicellulose aqueous solution used as the dispersion liquid of the hydrophobic coating has the comprehensive advantages of degradability, safety, environmental protection, relatively good coating adhesion effect and simple process, and has the application prospect of forming industrialization in the wood processing field.

2. The long-chain anhydride modified hemicellulose is used for partially replacing hemicellulose, so that the dispersion efficiency of a dispersing agent and the particle size of an agglomerate can reach a synergistic high-efficiency level, the roughness and uniformity of a micro-nano structure of a hydrophobic surface after the coating is formed into a film can be improved, and the hydrophobic performance of the hydrophobic surface is further improved. Meanwhile, the affinity between the long-chain anhydride modified hemicellulose and the wood surface can be higher than that of the hemicellulose, so that the adhesion effect of the paint and the wood surface can be improved, the effective hydrophobic time of the hydrophobic surface can be prolonged, and the service life of the hydrophobic surface can be prolonged. Furthermore, the hemicellulose subjected to esterification modification has higher hydrophobic property than hemicellulose, so that the hydrophobic property of the coating can be improved in an auxiliary manner.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive faculty for a person skilled in the art.

Fig. 1 is a schematic representation of the surface contact angle of a hydrophobic surface obtained by coating a wood surface with the coating of examples 1, 2, 3, 4.

Detailed Description

In order to better understand the technical solutions in the present application, the following description will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, shall fall within the scope of the present application.

Example 1

The embodiment of the application discloses a hydrophobic paint for wood, which comprises a dispersing agent and nano silicon dioxide particles dispersed in the dispersing agent. Specifically, the dispersant is an aqueous solution, and the main component of the dispersant is hemicellulose; in this coating, the ratio of hemicellulose concentration to nanosilica particle concentration was 1:1.

The inventor creatively discovers that hemicellulose has relatively good agglomeration performance, amphipathy performance and dispersion performance in long-term research practice, so that the hemicellulose can be used as a carrier of nano silicon dioxide particles and a coupling agent of the nano silicon dioxide particles and the wood surface, and a hydrophobic coating taking hemicellulose aqueous solution as a dispersion liquid and a nano silicon dioxide particle stacking main agent is prepared. Compared with the nano silica gel coating and the coating with the nano silica particles dispersed by the synthetic adhesive in the prior art, the coating of the embodiment has the comprehensive advantages of degradability, safety, environmental protection and relatively good coating adhesion effect. Additionally, compared with the prior art coating with nano silicon dioxide particles dispersed by cellulose solution, the technical scheme of the application does not use an additional coupling agent and a dispersing agent, so the method has the advantage of relatively lower manufacturing cost. The advantages are combined, so that the method has an application prospect of forming industrialization in the field of wood processing.

In particular, the better agglomeration properties enable the nano-silica particles dispersed in the hemicellulose aqueous solution to form larger (but suitable) agglomerates, thereby forming a micro-nano structure with relatively higher roughness when forming a film to build a hydrophobic surface with better hydrophobic properties. The better amphipathy of hemicellulose can be expressed in the following steps: the nano silicon dioxide particles can be agglomerated in hemicellulose water solution to form agglomerates with a certain particle size, and meanwhile, as a part of wood fiber raw materials, hemicellulose has strong affinity with the wood surface, so that the hemicellulose can become a connecting bridge between the nano silicon dioxide particles and the wood surface, one side is loaded with the nano silicon dioxide particles, and the other side is attached to the wood surface with affinity. Therefore, the coating in the technical scheme does not need to add a dispersing agent to promote the dispersing efficiency of the nano silicon dioxide particles, or to add a coupling agent to promote the adhesion of the nano silicon dioxide particles on the surface of the wood, so that the manufacturing cost of the coating can be further reduced, and the manufacturing process of the coating is simplified. The better dispersion property enables the nano silicon dioxide particles to be uniformly dispersed in hemicellulose aqueous solution to form agglomerates with larger particle size (but proper) so as to improve the uniformity of film formation and the roughness of micro-nano structure. It is noted that, in the prior art, an auxiliary dispersing agent is necessary to be used in the coating for dispersing the nano silicon dioxide particles in the cellulose solution, or the nano silicon dioxide particles are modified to have better dispersing performance, otherwise, the nano silicon dioxide particles are excessively agglomerated in the cellulose aqueous solution to cause the agglomerate particle size to be too large to form the coating with the micro-nano structure.

Preferably, the hemicellulose is extracted from bagasse and prepared. Firstly, putting bagasse into a plant crusher to crush and screen to obtain a bagasse sample with 40-60 meshes, extracting the bagasse sample in a Soxhlet extractor by using absolute ethyl alcohol for 6 hours, standing and air-drying, and then obtaining a dried first intermediate product in an oven under the drying condition of 70 ℃. Then, putting the first intermediate product into a conical flask, adding a sodium chlorite solution with the concentration of 2.0wt% to obtain a first mixed solution, wherein the solid-liquid ratio of the first intermediate product to the sodium chlorite solution is 1:25, regulating the pH value of the first mixed solution to 4.5 by using glacial acetic acid (acetic acid), and then reacting for 1h by using a heating magnetic stirrer at the temperature of 60 ℃ and the rotating speed of 450rpm to obtain a second mixed solution; continuously adding sodium chlorite solution into the second mixed solution to increase the concentration of the sodium chlorite solution to 3.0 weight percent, maintaining the pH value of the second mixed solution to 4.5 by using glacial acetic acid, and continuously reacting for 1h to obtain a third mixed solution; and continuously adding sodium chlorite solution into the third mixed solution to raise the concentration of the sodium chlorite solution to 3.0wt%, maintaining the pH value of the third mixed solution to 4.5 by using glacial acetic acid, and continuously reacting for 1h (dispersing the solution bagasse raw material by using a glass rod every 15min in the process to uniformly react) so as to obtain a fourth mixed solution. And after the reaction is finished, filtering the fourth mixed solution, collecting the solid part to obtain the heald cellulose, and drying the heald cellulose in an oven under the drying condition of 70 ℃ until the dryness is more than 90%. And finally, adding a 1.5% sodium hydroxide solution into the dried holocellulose, wherein the solid-liquid ratio of the holocellulose to the sodium hydroxide solution is 1:15, extracting for 3 hours at 60 ℃ by using a heating magnetic stirrer at the speed of 300rpm, filtering to obtain a fifth mixed solution, regulating the pH value of the fifth mixed solution to 5.5 by using concentrated hydrochloric acid, precipitating hemicellulose in the fifth mixed solution by using three times the volume of absolute ethyl alcohol of the fifth mixed solution, and standing for 10-12 hours to obtain the hemicellulose.

The nano-silica particles used are obtained by purchase. For example, the nano silicon dioxide particles with the model of SP30T have the particle size of 30+/-5 nm, the specific surface area of 150-300 m/g and the pH value of 5-7.

The method for preparing the hydrophobic paint for the wood by utilizing the hemicellulose and the nano silicon dioxide particles comprises a preparation process of a dispersing agent and a process of mixing treatment, and takes 100ml of paint as an example:

the dispersant is prepared by dissolving a main component, which is hemicellulose in this example, in water under stirring. Specifically, hemicellulose was dissolved in water using a heated magnetic stirrer at a temperature of 60 ℃ and a rotation speed of 400 rpm. The mass ratio of hemicellulose to water was 1:100, in other words, 1.0g hemicellulose was dissolved in 100ml water.

The step of mixing is a step of further dispersing the nano silica particles in the dispersant while stirring to obtain the paint. Specifically, nano silicon dioxide particles are dissolved in a dispersing agent, and then an ultrasonic cell wall breaking instrument is used for dispersing the dispersing liquid for 5min. The mass ratio of the nano-silica particles to hemicellulose was 1:1, in other words, 1.0g of nano-silica particles was dispersed in the above-mentioned dispersing agent.

The application method of the hydrophobic coating is that wood to be treated is soaked in the coating prepared by the method for 18-72 h (for example, 24 h), and the application amount of the coating is only required to submerge the wood. Drying of the wood and its paint coating was then completed within 35 minutes. For example, placing the impregnated wood in an oven employs drying conditions at 105 ℃ to allow the wood and its surface coating to dry rapidly within 30 minutes. The rapid drying helps the paint form a stable coating on the surface of the wood, and avoids excessive penetration of moisture in the paint.

The surface properties of the hydrophobic surface obtained by coating the wood surface with the coating of example 1 are shown in table 1. The contact angle after abrasion of the experimental item is obtained by a method that the hydrophobic surface of the wood is placed on 12000Pa high-pressure sand paper for 15cm to rub for 100 times in a reciprocating way, and then the surface contact angle is measured; the coating agglomerate particle size is the average geometric particle size of the agglomerate. The experimental control group 1 is a hydrophobic coating prepared by taking an unmodified cellulose aqueous solution as a dispersing agent, and the control group 2 is a hydrophobic coating prepared by grafting a vinyl trioxysilane polymer and modifying nano silica sol; the coatings of the control group 1 and the control group 2 are coated on the surface of the wood by a method of soaking for 24 hours, and are dried in an oven in an environment of 105 ℃ for 30 minutes.

TABLE 1 hydrophobic wood surface Properties obtained by applying the coating of example 1

As is clear from the data in table 1, although the surface of the wood formed by the hydrophobic coating prepared by using the hemicellulose aqueous solution as the dispersing agent is only close to the performance level of the superhydrophobic surface (the surface contact angle should reach 150 °), it is obvious that the hydrophobic coating of the embodiment is composed of only water, hemicellulose and nano silica particles and is a degradable coating, so that the use of the coating does not affect the environmental protection of the wood as renewable resources, the components are relatively simple, and no additional coupling agent or dispersing agent is needed, thereby reducing the production and manufacturing cost, safety and environmental protection.

Further, the particle size of the cellulose-nano silica particle agglomerate is too large, so that the dispersion efficiency of the agglomerate in the dispersing agent is affected, and the too large particle size and the relatively low dispersion efficiency of the agglomerate make it difficult to form a relatively uniform micro-nano structure after the coating of the cellulose-nano silica system of the control group 1 is formed into a film, so that the hydrophobic effect of the hydrophobic surface formed by the coating is poor. In the coating of this example, the hemicellulose-nanosilica particle agglomerate has a large and moderate particle size and a relatively high dispersion efficiency, so that a hydrophobic surface with a better hydrophobic property can be obtained as compared with the coating of the control group 1. In addition, the manufacturing cost of hemicellulose is lower than that of cellulose, so that the technical solution of the embodiment can achieve the effect of obtaining a better hydrophobic surface at a lower cost than that of the control group 1.

Further, the hydrophobic surfaces of example 1, control 2 reduced the hydrophobic angle by 23.1%, 24.6%, and 34.1%, respectively, after repeated rubbing with sandpaper. According to the method, the cellulose and the nano silicon dioxide particle aggregates and the hemicellulose and the nano silicon dioxide particle aggregates can form relatively better crosslinking with the wood surface through the hydrogen bond connection and the chemical bond connection formed by the cellulose and the hemicellulose and the wood surface in the soaking and hot drying processes, so that the coating has better adhesion effect with the wood surface compared with the coating of the hydrophobically modified nano silicon dioxide sol system of the control group 2.

In summary, considering the advantages of low manufacturing cost, safety and environmental protection of the hydrophobic performance achieved by the coating of the embodiment, the comprehensive performance of the coating is superior to that of the cellulose-nano silica system coating and the hydrophobic modified nano silica sol system coating, and the coating can become a waterproof coating for industrial application in the wood processing field.

Example 2

Example 2 differs from example 1 in that the main component of the dispersant is a mixture of hemicellulose and long-chain acid anhydride modified hemicellulose, in other words, the dispersant is an aqueous solution of a mixture of hemicellulose and long-chain acid anhydride modified hemicellulose; meanwhile, in the coating, the ratio of the concentration of the main component (mixture of hemicellulose and long-chain anhydride modified hemicellulose) to the concentration of the nano silica particles is 1:1. Preferably, the long chain anhydride modified hemicellulose is dodecenyl succinic anhydride graft modified hemicellulose. Of course, other esterified modified hemicelluloses, as would be known to one of ordinary skill in the art, may also be the primary component of the dispersants of the present application.

Compared with the technical scheme of the embodiment 1, in the embodiment, the long-chain anhydride modified hemicellulose is used for replacing hemicellulose, so that the dispersion efficiency of a dispersing agent and the particle size of an agglomerate can reach a synergistic high-efficiency level, the roughness and uniformity of the micro-nano structure of the hydrophobic surface of the coating after film formation can be improved, and the hydrophobic performance of the hydrophobic surface is further improved. The inventor creatively discovers that the affinity between the long-chain anhydride modified hemicellulose and the wood surface can be higher than that of the hemicellulose, so that the adhesion effect of the paint and the wood surface can be improved, the effective hydrophobic time of the hydrophobic surface can be prolonged, and the service life of the hydrophobic surface can be prolonged. Furthermore, the hemicellulose subjected to esterification modification has higher hydrophobic property than hemicellulose, so that the hydrophobic property of the coating can be improved in an auxiliary manner.

The method for preparing the hydrophobic coating by using the long-chain anhydride modified hemicellulose and the nano silicon dioxide particles comprises the steps of hemicellulose modification, dispersant preparation and mixing treatment, and takes 100ml of coating as an example:

the hemicellulose modifying process is to esterify hemicellulose with hemicellulose modifier in alkaline environment.

Specifically, the hemicellulose modification step is to dissolve the prepared hemicellulose in a solvent, preferably dimethyl sulfoxide solvent (DMSO), in a heated magnetic stirrer at 60 ℃, at 300rpm or 400 rpm. The mass ratio of hemicellulose to solvent is 1 (380-420), for example, hemicellulose is 1.98g, and dimethyl sulfoxide solvent (DMSO) is 80ml. Then, the solvent in which the hemicellulose is dissolved is cooled, and after the temperature of the solvent is reduced to 50+/-2 ℃, the catalyst and the hemicellulose modifier are added into the solvent. Preferably, the catalyst is 4-Dimethylaminopyridine (DMAP) and the mass ratio of catalyst to hemicellulose is about 2:1, for example when the hemicellulose is dosed in an amount of 1.98g, the amount of 4-Dimethylaminopyridine (DMAP) is 1.0g. The hemicellulose modifier is dodecenyl succinic anhydride (DDSA, concentration 266.38 g/mol). The difference in the ratio of the amount of dodecenyl succinic anhydride (DDSA) to the amount of hemicellulose added can affect the degree of esterification of hemicellulose in the modification reaction. In this example, four modified hemicelluloses, referred to as DDSA-0.05, DDSA-0.15, DDSA-0.25, and DDSA-0.50, can be obtained by controlling the molar ratio of the two to be 0.05:1, 0.15:1, 0.25:1, and 0.50:1, respectively. Finally, the mixed powder of hemicellulose and dodecenyl succinic anhydride grafted modified hemicellulose is obtained through the drying and baking means in the prior art.

Subsequently, in the preparation process of the dispersant, 1.0g of the mixed powder of hemicellulose and dodecenyl succinic anhydride graft-modified hemicellulose was added to 100ml of water at 60℃with continuous stirring, to obtain the dispersant.

Finally, in the mixing treatment process, 1.0g of nano silicon dioxide particles are added into the dispersing agent at the temperature of 60 ℃ under the continuous stirring state, and the dispersing agent is transferred into an ultrasonic cell wall breaking instrument for continuous dispersion treatment for 5min after uniform dispersion, so as to obtain the coating.

The application method of the hydrophobic coating is that wood to be treated is soaked in the coating prepared by the method for 30 hours, and the usage amount of the coating is only required to submerge the wood. Then the wood soaked with the paint is placed in an oven, and the paint coating on the wood and the surface of the wood is quickly dried in 25 minutes by adopting a drying condition of 108 ℃.

Example 3

Example 3 differs from example 2 in that the main component of the dispersant of this hydrophobic coating is a mixture of hemicellulose and dodecenyl succinic anhydride graft modified hemicellulose, and dodecenyl succinic anhydride (DDSA) is attached to the surface of the mixture.

In the hemicellulose modification step, the molar ratio of dodecenyl succinic anhydride (DDSA) to hemicellulose was controlled to be 0.75:1 to obtain modified hemicellulose, which was designated as DDSA-0.75. Finally, the mixed powder of the hemicellulose with the surface attached with the dodecenyl succinic anhydride (DDSA) and the dodecenyl succinic anhydride grafted modified hemicellulose is obtained by the drying and drying means in the prior art.

In the preparation process of the dispersant, 1.0g of the above powder was added to 100ml of water at 60℃with continuous stirring to obtain the dispersant.

Example 4

Example 4 differs from example 3 in that in the hemicellulose modification step, the molar ratio of dodecenyl succinic anhydride (DDSA) to hemicellulose was controlled to be 0.85:1 to give modified hemicellulose, designated DDSA-0.85.

The surface contact angles of the hydrophobic surfaces obtained by coating the wood surfaces with the coatings of examples 1, 2, 3, 4 are shown with reference to fig. 1.

The surface properties of the hydrophobic surfaces obtained by coating the wood surfaces with the coatings of examples 2, 3, 4 are shown with reference to table 2, wherein the solution of example 1 can be designated DDSA-0.

TABLE 2 hydrophobic wood surface Properties obtained by applying the coatings of examples 2, 3, 4

As is clear from the data in Table 2, the hydroxyl substitution degree of hemicellulose and the molecular weight of the dodecenyl succinic anhydride graft modified hemicellulose increased with the increase of the molar ratio of dodecenyl succinic anhydride (DDSA) to hemicellulose, but when the substitution degree reached about 0.50, the esterification reaction did not proceed even when the amount of dodecenyl succinic anhydride (DDSA) used was increased, and the molecular weight was maintained at a level of about 0.50. With the progress of the esterification reaction, the long-chain anhydride can not be subjected to the esterification reaction with unreacted hydroxyl due to the steric hindrance, and the reaction reaches an equilibrium state, and at the moment, the hydroxyl substitution degree of hemicellulose is not increased with the increase of the use amount of dodecenyl succinic anhydride (DDSA).

After the esterification reaction, the dispersing efficiency of the dispersing agent is greatly improved, but the dispersing efficiency of the dispersing agent is reduced along with the increase of the molar ratio of dodecenyl succinic anhydride (DDSA) to hemicellulose until the molar ratio of the dodecenyl succinic anhydride (DDSA) to the hemicellulose reaches 0.75:1 (namely DDSA-0.75), and the transition type is improved, wherein the dispersing efficiency of the dispersing agent exceeds the numerical value of the example 1 (DDSA-0) again. Continuing to increase the molar ratio of the two, the dispersing efficiency of the dispersant still maintains the level of DDSA-0.75. The experimental results of the agglomerate particle size are similar to those of the case of dispersion efficiency. From the above data, it can be seen that the aqueous hemicellulose solution modified by the esterification reaction affects the formation of agglomerates of nano silica particles, so that the particle size of the agglomerates is small but the dispersing efficiency of the dispersing agent is relatively high, which makes the mole ratio of dodecenyl succinic anhydride (DDSA) to hemicellulose lower in the hydrophobic property (surface contact angle, 14s rear contact angle) of the hydrophobic surface after the coating film formation, compared with the hemicellulose, before the esterification reaction reaches the equilibrium state. However, when the esterification reaction reaches an equilibrium state and stops the reaction, the particle size of the agglomerates suddenly increases, and at the same time, the dispersion efficiency does not decrease due to the increase in the particle size of the agglomerates, but rather, the synergistic increase occurs. After the particle size of the agglomerate and the dispersion efficiency are synergistically increased, the hydrophobic property of the DDSA-0.75 hydrophobic surface is improved.

The mechanism by which the above phenomenon occurs is not clear, and the inventors speculate that the residual dodecenyl succinic anhydride (DDSA) adheres to the surface of hemicellulose or dodecenyl succinic anhydride graft-modified hemicellulose due to insufficient esterification reaction, and after the preparation of the dispersant, the residual dodecenyl succinic anhydride (DDSA) is insoluble in water, so that agglomeration of hemicellulose or dodecenyl succinic anhydride graft-modified hemicellulose and nano silica particles can be promoted, the particle diameter of the agglomerates can be increased, and at the same time, dispersion of the agglomerates in the dispersant can be promoted.

Therefore, although the long-chain anhydride-modified hemicellulose itself has a negative effect on the hydrophobic property of the coating, when the hemicellulose, the long-chain anhydride-modified hemicellulose and dodecenyl succinic anhydride (DDSA) coexist, a relatively good hydrophobic effect can be achieved, and the hydrophobic surface reaches the level of the superhydrophobic surface.

Further, it is currently believed that loading nano silica particles on cellulose can improve the hydrophilicity of cellulose, and therefore, in the technical solution of the prior art, only nano silica particles are loaded on the surface of cellulose to form agglomerates, which are used as a hydrophobic coating. However, the inventors have found that the hydrophilicity of cellulose itself still affects the durability of the hydrophobic effect of the hydrophobic surface, i.e. the appearance of the hydrophobic angle after 14 s. Since modification of hemicellulose by dodecenyl succinic anhydride (DDSA) is achieved by replacing hydroxyl groups, dodecenyl succinic anhydride (DDSA) also reduces hydrophilicity of hemicellulose at the same time, so that hydrophobic durability of the coating is improved.

In summary, hemicellulose, long-chain anhydride modified hemicellulose, and dodecenyl succinic anhydride (DDSA) that coexist in the coating when the molar ratio of dodecenyl succinic anhydride (DDSA) to hemicellulose is at a level of (0.7 to 0.8): 1 are capable of promoting the hydrophobic property of the hydrophobic surface, the durability of the hydrophobic property, and the adhesion effect of the coating.

Example 5

Example 5 differs from example 3 in that the method of using the hydrophobic coating of this example sprays water onto the surface of the wood to be treated in an amount of 30 to 35 grams per square meter; and sanding the wood surface in a state that the water spraying surface is not dried, wherein the model number of the sand paper is 240#, 320# or 400#. The sanded wood is soaked in the paint for 30 hours, the temperature of the paint is maintained at 55 ℃ by heating during soaking, and the usage amount of the paint only needs to submerge the wood. Then placing the wood soaked with the paint in an oven, and adopting a drying condition of 105 ℃ to quickly dry the paint coating on the wood and the surface of the wood within 30 minutes. The surface properties of the hydrophobic surface obtained by coating the wood surface with the coating of example 5 are shown in table 3.

TABLE 3 hydrophobic wood surface Properties obtained by applying the coating of example 5

From the data in Table 3, it is understood that in example 5, the adhesion effect of the coating on the treated surface can be improved by using a soaking temperature of 55℃and roughening the surface of the wood before the soaking treatment. The inventors believe that this phenomenon is caused by residual dodecenyl succinic anhydride (DDSA) contacting the wood surface. Specifically, after the residual dodecenyl succinic anhydride (DDSA) contacts the wood surface, esterification reaction is carried out on the wood surface under specific conditions, so that the hydroxyl groups on the wood surface are replaced, the hydrophobicity of the wood surface is improved, and meanwhile, the affinity between the dodecenyl succinic anhydride grafted modified hemicellulose in the coating and the wood surface is improved, and the adhesion effect between the coating and the wood surface is further improved. The decrease in contact angle after abrasion was reduced from 23% to 30% to a level of 14.0%. It is apparent that the paint, the paint preparation method, and the paint application method of example 5 can improve the adhesion effect and the service life of the paint.

The foregoing description is for purposes of illustration and is not intended to be limiting. Many embodiments and many applications other than the examples provided will be apparent to those of skill in the art upon reading the above description. The scope of the present teachings should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are incorporated herein by reference for the purpose of completeness. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended to forego such subject matter, nor should the applicant be deemed to have such subject matter not considered to be part of the subject matter of the disclosed application.

Claims

1. The preparation method of the hydrophobic coating for the wood comprises a preparation process of a dispersing agent and a mixing process, and is characterized in that the hydrophobic coating consists of water, hemicellulose, long-chain anhydride modified hemicellulose and nano silica;

the preparation process of the dispersing agent is a process of dissolving a main component in water under stirring to obtain the dispersing agent, wherein the main component is a mixture of hemicellulose and long-chain anhydride modified hemicellulose;

the step of mixing is a step of dispersing nano silica particles in the dispersing agent while stirring to obtain the coating material;

the long-chain anhydride modified hemicellulose is prepared through a hemicellulose modification procedure, specifically, the hemicellulose is subjected to esterification reaction with a hemicellulose modifier in an alkaline environment, wherein the hemicellulose modifier is a dodecenyl succinic anhydride reagent;

the molar ratio of the dodecenyl succinic anhydride reagent to the hemicellulose is (0.7-0.8): 1.

2. The method for preparing a hydrophobic paint for wood according to claim 1, wherein the hemicellulose modifying step is to dissolve hemicellulose in a solvent at 58 ℃ to 62 ℃, then cool the solvent in which the hemicellulose is dissolved, and add a catalyst and the hemicellulose modifier to the solvent after the temperature of the solvent is reduced to 48 ℃ to 52 ℃.

3. The method for preparing a hydrophobic paint for wood according to claim 2, wherein the solvent is dimethyl sulfoxide solvent and the catalyst is 4-dimethylaminopyridine powder.