Modified phenolic resin, composite material and preparation method thereof

Abstract

The invention provides a modified phenolic resin, a composite material and a preparation method thereof, and belongs to the technical field of composite material molding, the preparation method of the modified phenolic resin comprises the following steps: mixing raw materials in a solvent, and adjusting the pH value to a set pH value to obtain the modified phenolic resin; wherein the raw materials comprise phenol, formaldehyde and azobenzene modified polydimethylsiloxane. Based on the method, the polydimethylsiloxane PDMS has methyl, is low in surface energy and is hydrophobic, so that the obtained modified phenolic resin is good in waterproofness, the phenolic resin composite material prepared from the modified phenolic resin is not prone to moisture absorption and deformation and convenient to transport and store, and epoxy resin does not need to be coated on the surface of a composite material product.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material molding, and specifically relates to a modified phenolic resin, a composite material and a preparation method thereof. Background Art

[0002] RTM molding is the abbreviation of resin transfer molding. It is a composite material production process in which the reinforced fiber flat fabric is placed in the mold first, and then a low-viscosity resin is injected into the mold under vacuum or pressure or both, impregnating the fiber flat fabric and curing. Phenolic resin has excellent heat resistance, flame retardancy, wear resistance and low smoke rate properties, and is widely used in molding compounds, adhesives, fireproof materials and the matrix of advanced composite materials.

[0003] However, since phenolic resin is hydrophilic, the phenolic resin composite material (cured product) obtained by RTM molding is also hydrophilic. In order to avoid moisture absorption and deformation of the phenolic resin composite material during transportation and storage, it is necessary to coat a layer of epoxy resin on the surface of the phenolic resin composite material to achieve a waterproof effect. In addition, when the cured product is sprayed with paint, in order to ensure that the paint is effectively attached to the surface of the product, the epoxy resin on the product surface needs to be polished off.

[0004] It can be seen that the existing phenolic resin composite materials have the problems of inconvenient storage and transportation, as well as a complicated painting process. Summary of the invention

[0005] Therefore, the present invention provides a modified phenolic resin, a composite material and a preparation method thereof, which can solve the technical problem of inconvenient storage and transportation of phenolic resin composite materials in the prior art.

[0006] In order to solve the above problems, the present invention provides a method for preparing a modified phenolic resin, comprising the following steps:

[0007] The raw materials are mixed in a solvent, and the pH value is adjusted to a set pH value to obtain a modified phenolic resin;

[0008] Wherein, the raw materials include phenol, formaldehyde and azobenzene-modified polydimethylsiloxane;

[0009] Wherein, the structural formula of the azobenzene-modified polydimethylsiloxane is as follows:

[0010]

[0011] Furthermore, the preparation steps of the azobenzene-modified polydimethylsiloxane include:

[0012] The polydimethylsiloxane containing a mercapto group, azobenzene containing a carbon-carbon double bond, and a catalyst are mixed and reacted to obtain the azobenzene-modified polydimethylsiloxane;

[0013] Preferably, the reaction time is 12 to 72 hours;

[0014] Preferably, the mass ratio of the azobenzene containing carbon-carbon double bonds to the polydimethylsiloxane containing mercapto groups is 1:100-105;

[0015] Preferably, the catalyst is triethylamine;

[0016] Preferably, the mass of the catalyst is 0.02 to 0.03 times the mass of azobenzene containing a carbon-carbon double bond;

[0017] Preferably, the structural formula of the mercapto-containing polydimethylsiloxane is as follows:

[0018]

[0019] Preferably, the structural formula of the azobenzene containing a carbon-carbon double bond is as follows:

[0020]

[0021] Furthermore, the step of preparing the polydimethylsiloxane containing mercapto groups comprises:

[0022] The polydimethylsiloxane (PDMS), a thiol compound and an alkaline catalyst are mixed in a solvent to obtain the polydimethylsiloxane containing a thiol group after reaction;

[0023] Preferably, the mass ratio of the polydimethylsiloxane PDMS to the thiol compound is 1:0.05-0.1;

[0024] Preferably, the mass of the alkaline catalyst is 0.1 to 0.3 times the mass of the thiol compound;

[0025] Preferably, the mass of the solvent is 10 to 20 times the mass of polydimethylsiloxane PDMS;

[0026] Preferably, the thiol compound is (3-mercaptopropyl)trimethoxysilane;

[0027] Preferably, the catalyst is potassium hydroxide;

[0028] Preferably, the solvent is acetone;

[0029] Preferably, the blending method is mechanical stirring.

[0030] Further, the azobenzene containing a carbon-carbon double bond is 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene;

[0031] Preferably, the preparation steps of 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene include:

[0032] Step S11) mixing nitroaniline solution, aniline ethanol solution and sodium nitrite aqueous solution to make nitroaniline and aniline react with each other to obtain a first suspension; filtering, washing and drying the first suspension to obtain 4-nitro-4′-amino-azobenzene;

[0033] Step S12) blending the 4-nitro-4′-amino-azobenzene and maleic anhydride in a solvent to allow the 4-nitro-4′-amino-azobenzene and maleic anhydride to undergo a second reaction to obtain a second suspension; filtering and washing the second suspension to obtain a precipitate;

[0034] The precipitate is mixed with a triethylamine solution, and then acetic anhydride and manganese acetate are added to obtain a mixed solution; the mixed solution is separated and purified to obtain the 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene.

[0035] Further, in the step S11), in the aniline ethanol solution, the mass of ethanol is 10 to 20 times the mass of aniline; and / or

[0036] The nitroaniline solution is obtained by adding nitroaniline to concentrated hydrochloric acid; preferably, the concentration of the concentrated hydrochloric acid is 36% to 38%; preferably, the mass of the concentrated hydrochloric acid is 2.5 to 3 times the mass of the nitroaniline; and / or

[0037] The molar mass ratio of the nitroaniline, sodium nitrite, aniline and concentrated hydrochloric acid is 1:1-1.05:1-1.05:1-1.05; and / or

[0038] The blending method is mechanical stirring; preferably, the mechanical stirring time is 2 to 4 hours; and / or

[0039] After filtering the first suspension, it is washed with water and ethanol in sequence.

[0040] Further, in the step S12), the mass of the solvent is 10 to 20 times the mass of 4-nitro-4′-amino-azobenzene; the solvent is acetone; and / or

[0041] The blending method is mechanical stirring; preferably, the mechanical stirring is carried out at 60-80° C.; the stirring time is 4 to 6 hours; and / or

[0042] The mass of triethylamine is 0.02 to 0.03 times the mass of 4-nitro-4′-amino-azobenzene; and / or

[0043] Before the step of adding acetic anhydride and manganese acetate, the method further comprises: a first stirring step; preferably, the first stirring step is performed at 60-80° C.; preferably, the first stirring step lasts for 5 to 20 minutes; and / or

[0044] The molar mass ratio of the 4-nitro-4′-amino-azobenzene, maleic anhydride, triethylamine and acetic anhydride is 1:1-1.05:1-1.05:6-6.5; and / or

[0045] After the step of adding acetic anhydride and manganese acetate, the method further comprises: a second stirring step; preferably, the second stirring step is performed at 60 to 80° C.; preferably, the second stirring step lasts for 4 to 6 hours; and / or

[0046] The mixed solution is separated and purified by column chromatography; preferably, the solvents used in the column chromatography are petroleum ether and ethyl acetate; wherein the volume ratio of petroleum ether to ethyl acetate is 1:1-1.5.

[0047] Furthermore, in the step 2), the phenol and formaldehyde undergo a polycondensation reaction to obtain a phenolic resin; preferably, the mass of the azobenzene-modified polydimethylsiloxane is 5% to 15% of the mass of the phenolic resin; and / or

[0048] The molar ratio of phenol to formaldehyde is 1:1.5-2.5; and / or

[0049] The amount of the solvent added is 10 to 20 times the mass of the azobenzene-modified polydimethylsiloxane; preferably, the solvent is ethanol;

[0050] The set pH value is 8 to 11; and / or

[0051] The pH value is adjusted using an alkaline catalyst; preferably, the alkaline catalyst is one or more of sodium hydroxide, magnesium hydroxide, barium hydroxide, and aluminum hydroxide; preferably, the amount of the alkaline catalyst is 0.1 to 0.3 times the mass of phenol.

[0052] In another aspect, the present invention provides a modified phenolic resin, comprising a phenolic resin and azobenzene-modified polydimethylsiloxane dispersed on the phenolic resin;

[0053] Preferably, the modified phenolic resin is obtained by any of the preparation methods described above.

[0054] In another aspect, the present invention provides a method for preparing a phenolic resin composite material, comprising the following steps:

[0055] Impregnation step: impregnating the fiber fabric with modified phenolic resin to obtain a fabric intermediate;

[0056] Curing step: performing a curing reaction on the fabric intermediate to obtain a phenolic resin composite material;

[0057] Preferably, in the impregnation step: the modified phenolic resin is the modified phenolic resin described above;

[0058] Preferably, the step of impregnating the fiber fabric with the modified phenolic resin comprises: applying the modified phenolic resin to the surface of the fiber fabric, and brushing the modified phenolic resin flat with a pressure roller; further preferably, the mass of the modified phenolic resin applied to the surface of the fiber fabric is 5-10% of the mass of the fiber fabric;

[0059] Preferably, the impregnation pressure is 1.2 to 1.5 MPa;

[0060] Preferably, the curing reaction temperature is 120-160° C., and the curing reaction time is 8-12 hours.

[0061] In another aspect, the present invention provides a phenolic resin composite material, wherein the contact angle of the phenolic resin composite material under visible light is greater than 81°;

[0062] Under ultraviolet light of 365 nm, the contact angle of the phenolic resin composite material is less than 66°;

[0063] Preferably, the phenolic resin composite material is obtained by the preparation method described above.

[0064] Compared with the prior art, the present invention has at least the following beneficial effects:

[0065] 1. On the one hand, the present invention provides a method for preparing a modified phenolic resin, wherein the modified phenolic resin is obtained by mixing phenol, formaldehyde and azobenzene-modified polydimethylsiloxane; based on the above method, since polydimethylsiloxane PDMS has methyl groups, has a low surface energy and exhibits hydrophobicity, the modified phenolic resin has good waterproofness, and the phenolic resin composite material prepared by the modified phenolic resin is not easy to absorb moisture and deform, is easy to transport and store, and does not need to coat epoxy resin on the surface of the composite material product.

[0066] 2. Furthermore, due to the presence of azobenzene, the painting process of the phenolic resin material product obtained by modifying the phenolic resin is relatively simple. On the one hand, there is no need to polish the epoxy resin on the surface. On the other hand, under the irradiation of ultraviolet light of different wavelengths, the structure of azobenzene changes, so that the obtained phenolic resin composite material is transformed from hydrophobic to hydrophilic, which allows the paint to effectively adhere to the surface of the composite material.

[0067] 3. On the other hand, the present invention provides a method for preparing a phenolic resin composite material, which adopts the above-mentioned modified phenolic resin to obtain a phenolic resin composite material through RTM molding, specifically comprising: using the above-mentioned modified phenolic resin to impregnate fiber fabric to obtain a fabric intermediate; then curing the fabric intermediate to obtain a phenolic resin composite material; the phenolic resin composite material obtained by the above method has a contact angle of more than 81° under visible light, that is, it is hydrophobic; after irradiation with 365nm ultraviolet light, its contact angle is less than 66°, showing hydrophilicity. DETAILED DESCRIPTION

[0069] In view of the fact that existing phenolic resin composite materials need to be coated with a layer of epoxy resin on the surface during transportation and storage, and the epoxy resin on the surface needs to be polished off when the product is spray-painted; the present invention provides a phenolic resin composite material with waterproofness and a preparation method thereof, and the specific scheme is as follows:

[0070] In one aspect, the present invention provides a method for preparing a modified phenolic resin, comprising the following steps:

[0071] The raw materials are mixed in a solvent, and the pH value is adjusted to a set pH value to obtain a modified phenolic resin; wherein the raw materials include phenol, formaldehyde and azobenzene-modified polydimethylsiloxane;

[0072] The molar ratio of phenol to formaldehyde is 1:1.5-2.5; phenol and formaldehyde undergo polycondensation to obtain phenolic resin; the mass of azobenzene-modified polydimethylsiloxane is 5%-15% of the mass of the phenolic resin; ethanol is used as the solvent, and the amount of ethanol added is 10-20 times the mass of the azobenzene-modified polydimethylsiloxane;

[0073] The pH value is set to 8-11 by using an alkaline catalyst; the alkaline catalyst is selected from one or more of sodium hydroxide, magnesium hydroxide, barium hydroxide, and aluminum hydroxide; the amount of the alkaline catalyst is 0.1-0.3 times the mass of phenol;

[0074] The preparation steps of azobenzene-modified polydimethylsiloxane include: mixing polydimethylsiloxane containing a mercapto group and azobenzene containing a carbon-carbon double bond, and under the action of a catalyst, causing the mercapto group and the carbon-carbon double bond to undergo a click chemical reaction to obtain azobenzene-modified polydimethylsiloxane; wherein the azobenzene-modified polydimethylsiloxane can be obtained by reacting at room temperature; the azobenzene containing a carbon-carbon double bond is 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene;

[0075] The reaction formula is as follows:

[0076]

[0077] In the above reaction formula, (3) is polydimethylsiloxane containing a mercapto group, (8) is 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene (azobenzene containing a carbon-carbon double bond), and (9) is azobenzene-modified polydimethylsiloxane;

[0078] The reaction time is 12 to 72 hours; the mass ratio of 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene to the mercapto-containing polydimethylsiloxane is 1:100 to 105; the catalyst is triethylamine; and the mass of the catalyst is 0.02 to 0.03 times the mass of the azobenzene containing a carbon-carbon double bond.

[0079] The step of preparing the polydimethylsiloxane containing a mercapto group comprises: mixing polydimethylsiloxane PDMS, a thiol compound, and an alkaline catalyst in a solvent so that the polydimethylsiloxane PDMS reacts with the thiol compound to obtain polydimethylsiloxane containing a mercapto group; wherein the polydimethylsiloxane containing a mercapto group can be obtained by reacting at room temperature;

[0080] Among them, the reaction formula is as follows:

[0081]

[0082] In the above reaction formula, (1) is polydimethylsiloxane PDMS, (2) is a thiol compound, and (3) is polydimethylsiloxane containing a mercapto group;

[0083] Preferably, the mass ratio of polydimethylsiloxane PDMS to the thiol compound is 1:0.05-0.1; the mass of the alkaline catalyst is 0.1-0.3 times the mass of the thiol compound; the mass of the solvent is 10-20 times the mass of the polydimethylsiloxane PDMS; the thiol compound is (3-mercaptopropyl)trimethoxysilane; the catalyst is potassium hydroxide; the solvent is acetone; and mechanical stirring is selected as the blending method.

[0084] The steps for preparing 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene include:

[0085] Step S11) mixing the nitroaniline solution, the aniline ethanol solution and the sodium nitrite aqueous solution to allow the nitroaniline and the aniline to undergo a first reaction to obtain a first suspension; filtering the first suspension to obtain a precipitate, then washing the obtained precipitate with water and ethanol in sequence, and drying to obtain 4-nitro-4′-amino-azobenzene;

[0086] Among them, the first reaction formula is as follows:

[0087]

[0088] In the first reaction formula, (4) is nitroaniline, (5) is aniline, and (6) is 4-nitro-4′-amino-azobenzene;

[0089] Specifically, firstly, water is used as a solvent to prepare a sodium nitrite aqueous solution, and ethanol is used as a solvent to prepare an aniline ethanol solution; then nitroaniline is added to concentrated hydrochloric acid to obtain a nitroaniline solution, and then the sodium nitrite aqueous solution is dripped into the nitroaniline solution to obtain the above-mentioned first suspension; wherein, in the aniline ethanol solution, the mass of ethanol is 10 to 20 times the mass of aniline; the nitroaniline solution is obtained by adding nitroaniline to concentrated hydrochloric acid; the concentration of concentrated hydrochloric acid is 36% to 38%; preferably, the mass of concentrated hydrochloric acid is 2.5 to 3 times the mass of nitroaniline; the molar mass ratio of nitroaniline, sodium nitrite, aniline and concentrated hydrochloric acid is 1:1 to 1.05:1 to 1.05:1 to 1.05; mechanical stirring is selected as the blending method; preferably, the mechanical stirring time is 2 hours;

[0090] Step S12) 4-nitro-4′-amino-azobenzene and maleic anhydride are mixed in a solvent to allow 4-nitro-4′-amino-azobenzene and maleic anhydride to undergo a second reaction to obtain a second suspension; the second suspension is filtered and washed to obtain a precipitate;

[0091] The precipitate is mixed with a triethylamine solution, and then acetic anhydride and manganese acetate are added to obtain a mixed solution; the mixed solution is separated and purified by column chromatography to obtain 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene; wherein the solvents used in the column chromatography are petroleum ether and ethyl acetate; wherein the volume ratio of petroleum ether to ethyl acetate is 1:1; wherein the precipitate has a carboxyl group, and undergoes an ion exchange reaction with triethylamine, and the hydroxyl group (OH) in the carboxylic acid (i.e., the precipitate) combines with the hydrogen (H) in the triethylamine to form water; acetic anhydride provides an acidic environment, and manganese acetate is a catalyst;

[0092] Wherein, the second reaction formula is as follows:

[0093]

[0094] In the first reaction formula, (6) is 4-nitro-4′-amino-azobenzene, (7) is maleic anhydride, and (8) is 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene;

[0095] Wherein, the mass of the solvent is 10 to 20 times the mass of 4-nitro-4′-amino-azobenzene; the solvent is acetone; the blending method is mechanical stirring; preferably, the mechanical stirring is carried out at 60-80° C.; the stirring time is 4 to 6 hours; the mass of triethylamine is 0.02 to 0.03 times the mass of 4-nitro-4′-amino-azobenzene; before the step of adding acetic anhydride and manganese acetate, it also includes: a first stirring step; preferably, the first stirring step is carried out at 60-80° C.; preferably, the first stirring step is carried out for 5 to 20 minutes; the molar mass ratio of 4-nitro-4′-amino-azobenzene, maleic anhydride, triethylamine, and acetic anhydride is 1:1 to 1.05:1 to 1.05:6 to 6.5; after the step of adding acetic anhydride and manganese acetate, it also includes: a second stirring step; preferably, the second stirring step is carried out at 60 to 80° C.; preferably, the second stirring step is carried out for 4 to 6 hours;

[0096] On the other hand, the present invention provides a modified phenolic resin, which comprises a phenolic resin and azobenzene-modified polydimethylsiloxane dispersed on the phenolic resin. The modified phenolic resin is obtained by any of the above preparation methods.

[0097] In another aspect, the present invention provides a method for preparing a phenolic resin composite material, comprising the following steps:

[0098] The impregnation step comprises applying the modified phenolic resin to the surface of the fiber fabric, and brushing the modified phenolic resin flat with a pressure roller so that the phenolic resin impregnates the fiber fabric to obtain a fabric intermediate; wherein the modified phenolic resin adopts the modified phenolic resin mentioned above; the content of the modified phenolic resin applied to the surface of the fiber fabric is 5-10%; and the impregnation pressure is 1.2-1.5 MPa;

[0099] Curing step: curing the fabric intermediate to obtain a phenolic resin composite material; the curing reaction temperature is 120-160° C.; the curing reaction time is 8-12 hours.

[0100] The above method is a method for RTM molding of modified phenolic resin composite materials. Based on the above method, since polydimethylsiloxane PDMS has methyl groups, has low surface energy and exhibits hydrophobicity, the modified phenolic resin obtained has good water resistance. The phenolic resin composite material prepared by the modified phenolic resin is not easy to absorb moisture and deform, is easy to transport and store, and does not need to be coated with epoxy resin on the surface of the composite material product; at the same time, due to the presence of azobenzene, the painting process of the phenolic resin material product obtained by the modified phenolic resin is relatively simple. On the one hand, there is no need to polish the epoxy resin on the surface. On the other hand, under the irradiation of ultraviolet light of different wavelengths, the structure of azobenzene changes, so that the obtained phenolic resin composite material is transformed from hydrophobic to hydrophilic, so that the paint can be effectively attached to the surface of the composite material.

[0101] Among them, under normal conditions, azobenzene presents a low-energy trans state; the trans state of azobenzene has a strong π-π* absorption band in the ultraviolet band, with a dominant peak around 325nm; in the visible light range, it has a weaker n-π* band, with a dominant peak around 450nm; under the induction of ultraviolet light, azobenzene will transform from a trans state to a high-energy cis state, thereby changing the phenolic resin composite material from hydrophobic to hydrophilic.

[0102] In another aspect, the present invention provides a phenolic resin composite material obtained by the above-mentioned preparation method; under visible light, the contact angle of the phenolic resin composite material is greater than 81°, that is, it is hydrophobic;

[0103] Under ultraviolet light of 365nm, the contact angle of the phenolic resin composite material is less than 66°, that is, it is hydrophilic, which is conducive to the adhesion of paint to the surface of the phenolic resin composite material product.

[0104] The present invention is further described below with reference to specific embodiments and comparative examples.

[0105] Example 1

[0106] This embodiment provides a method for preparing a modified phenolic resin, comprising the following steps:

[0107] Preparation of polydimethylsiloxane containing mercapto groups:

[0108] 1 part of polydimethylsiloxane PDMS, 0.05 part of (3-mercaptopropyl)trimethoxysilane (thiol compound), and 0.1 part of potassium hydroxide (alkaline catalyst) were mixed in 10 parts of ethanol (solvent), and mechanically stirred for 20 minutes to obtain polydimethylsiloxane containing mercapto groups;

[0109] The mass ratio of polydimethylsiloxane PDMS to the thiol compound is 1:0.05; the mass of the alkaline catalyst is 0.1 times the mass of the thiol compound; the mass of the solvent is 10 times the mass of the polydimethylsiloxane PDMS;

[0110] Preparation of 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene (azobenzene containing a carbon-carbon double bond):

[0111] Step S11) using 10 parts of water as a solvent and 1 part of sodium nitrite as a solute to prepare a sodium nitrite aqueous solution; using 10 parts of ethanol as a solvent and 1 part of aniline as a solute to prepare an aniline ethanol solution; adding 1 part of nitroaniline to 2.5 parts of concentrated hydrochloric acid to obtain a nitroaniline solution;

[0112] Dropping a sodium nitrite aqueous solution into a nitroaniline solution, then adding the solution into an aniline ethanol solution, and mechanically stirring the solution at room temperature for 2 hours to obtain a first suspension; filtering and separating the first suspension, washing the obtained precipitate with water and ethanol, and drying the obtained precipitate to obtain 4-nitro-4′-amino-azobenzene;

[0113] In the aniline ethanol solution, the mass of ethanol is 10 times the mass of aniline; the nitroaniline solution is obtained by adding nitroaniline to concentrated hydrochloric acid; the concentration of concentrated hydrochloric acid is 36%; the mass of concentrated hydrochloric acid is 2.5 times the mass of nitroaniline; the molar mass ratio of nitroaniline, sodium nitrite, aniline and hydrochloric acid is 1:1:1:1;

[0114] Step S12) 10 parts of acetone as a solvent, 1 part of 4-nitro-4′-amino-azobenzene and 1 part of maleic anhydride as a solvent are mixed, and mechanically stirred at 60° C. for 4 hours to obtain a second suspension; the second suspension is filtered, and a precipitate is obtained after washing with ethyl acetate;

[0115] Using 10 parts of acetone as a solvent, the above precipitate was mixed with 0.02 parts of triethylamine, and mechanically stirred at 60°C for 20 minutes to dissolve the above precipitate; then 6 parts of acetic anhydride and 0.02 parts of manganese acetate were added, and stirred at 60°C for 4 hours to obtain a mixed solution; after cooling to room temperature, the mixed solution was separated and purified by column chromatography (the solvent was petroleum ether and ethyl acetate, and the volume ratio was 1:1) to obtain 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene;

[0116] The mass of the solvent is 10 times the mass of 4-nitro-4′-amino-azobenzene; the mass of triethylamine is 0.02 times the mass of 4-nitro-4′-amino-azobenzene; the molar mass ratio of 4-nitro-4′-amino-azobenzene, maleic anhydride, triethylamine and acetic anhydride is 1:1:1:6;

[0117] 100 parts of the above mercapto-containing polydimethylsiloxane, 1 part of 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene, and 0.02 parts of triethylamine (catalyst) were mixed for 12 hours to obtain azobenzene-modified polydimethylsiloxane;

[0118] 1 part of phenol, 1.5 parts of formaldehyde, and 0.1 part of azobenzene-modified polydimethylsiloxane are mixed in 10 parts of ethanol solvent, sodium hydroxide is added as a catalyst, and the pH value is adjusted to 8 to obtain a modified phenolic resin;

[0119] The molar ratio of phenol to formaldehyde is 1:1.5; phenol and formaldehyde undergo polycondensation to obtain phenolic resin; the mass of azobenzene-modified polydimethylsiloxane is 10% of the mass of the phenolic resin; ethanol is used as the solvent, and its added amount is 10 times the mass of phenol.

[0120] This embodiment also provides a method for preparing a phenolic resin composite material, comprising the following steps:

[0121] Impregnation step: placing the glass fiber cloth (fiber fabric) into a mold, injecting the modified phenolic resin at a pressure of 1.5 MPa (impregnation pressure) to impregnate the glass fiber cloth with the modified phenolic resin to obtain a fabric intermediate; wherein the mass ratio of the modified phenolic resin to the glass fiber cloth is 1.5:1;

[0122] Curing step: placing the above fabric intermediate in an oven and performing a curing reaction at a temperature of 160° C. for 8 hours to obtain a phenolic resin composite material.

[0123] Example 2

[0124] This embodiment provides a method for preparing a modified phenolic resin, comprising the following steps:

[0125] Preparation of polydimethylsiloxane containing mercapto groups:

[0126] 1 part of polydimethylsiloxane PDMS, 0.075 parts of (3-mercaptopropyl)trimethoxysilane (thiol compound), and 0.015 parts of potassium hydroxide (alkaline catalyst) were mixed in 15 parts of ethanol (solvent), and mechanically stirred for 20 minutes to obtain polydimethylsiloxane containing mercapto groups;

[0127] The mass ratio of polydimethylsiloxane PDMS to the thiol compound is 1:0.075; the mass of the alkaline catalyst is 0.2 times the mass of the thiol compound; the mass of the solvent is 15 times the mass of the polydimethylsiloxane PDMS;

[0128] Preparation of 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene (azobenzene containing a carbon-carbon double bond):

[0129] Step S11) using 15 parts of water as a solvent and 1 part of sodium nitrite as a solute to prepare a sodium nitrite aqueous solution; using 15 parts of ethanol as a solvent and 1 part of aniline as a solute to prepare an aniline ethanol solution; adding 1 part of nitroaniline to 2.75 parts of concentrated hydrochloric acid to obtain a nitroaniline solution;

[0130] Dropping a sodium nitrite aqueous solution into a nitroaniline solution, then adding the solution into an aniline ethanol solution, and mechanically stirring the solution at room temperature for 2 hours to obtain a first suspension; filtering and separating the first suspension, washing the obtained precipitate with water and ethanol, and drying the obtained precipitate to obtain 4-nitro-4′-amino-azobenzene;

[0131] The mass of ethanol in the aniline ethanol solution is 15 times the mass of aniline; the nitroaniline solution is obtained by adding nitroaniline to concentrated hydrochloric acid; the concentration of the concentrated hydrochloric acid is 37%; the mass of the concentrated hydrochloric acid is 2.75 times the mass of nitroaniline; the molar mass ratio of nitroaniline, sodium nitrite, aniline and concentrated hydrochloric acid is 1:1.05:1:1-1.025;

[0132] Step S12) 15 parts of acetone as a solvent, 1 part of 4-nitro-4′-amino-azobenzene and 1 part of maleic anhydride as a solvent are mixed and mechanically stirred at 60° C. for 5 hours to obtain a second suspension; the second suspension is filtered and washed with ethyl acetate to obtain a precipitate;

[0133] Using 15 parts of acetone as a solvent, the above precipitate was mixed with 0.025 parts of triethylamine, and mechanically stirred at 60°C for 20 minutes to dissolve the above precipitate; then 6 parts of acetic anhydride and 0.02 parts of manganese acetate were added, and stirred at 60°C for 5 hours to obtain a mixed solution; after cooling to room temperature, the mixed solution was separated and purified by column chromatography (the solvent was petroleum ether and ethyl acetate, and the volume ratio was 1:1) to obtain 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene;

[0134] The mass of the solvent is 15 times the mass of 4-nitro-4′-amino-azobenzene; the mass of triethylamine is 0.025 times the mass of 4-nitro-4′-amino-azobenzene; the molar mass ratio of 4-nitro-4′-amino-azobenzene, maleic anhydride, triethylamine and acetic anhydride is 1:1.05:1:6.5;

[0135] 100 parts of the above mercapto-containing polydimethylsiloxane, 1 part of 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene, and 0.02 parts of triethylamine (catalyst) were mixed for 24 hours to obtain azobenzene-modified polydimethylsiloxane;

[0136] 1 part of phenol, 2 parts of formaldehyde, and 0.1 part of azobenzene-modified polydimethylsiloxane are mixed in 15 parts of ethanol solvent, sodium hydroxide is added as a catalyst, and the pH value is adjusted to 8 to obtain a modified phenolic resin;

[0137] The molar ratio of phenol to formaldehyde is 1:2; phenol and formaldehyde undergo polycondensation to obtain phenolic resin; the mass of azobenzene-modified polydimethylsiloxane is 10% of the mass of the phenolic resin; ethanol is used as the solvent, and the added amount thereof is 15 times the mass of the azobenzene-modified polydimethylsiloxane.

[0138] This embodiment also provides a method for preparing a phenolic resin composite material, comprising the following steps:

[0139] Impregnation step: placing the glass fiber cloth (fiber fabric) into a mold, injecting the modified phenolic resin at a pressure of 1.5 MPa (impregnation pressure) to impregnate the glass fiber cloth with the modified phenolic resin to obtain a fabric intermediate; wherein the mass ratio of the modified phenolic resin to the glass fiber cloth is 1.5:1;

[0140] Curing step: placing the above fabric intermediate in an oven and performing a curing reaction at a temperature of 160° C. for 8 hours to obtain a phenolic resin composite material.

[0141] Example 3

[0142] This embodiment provides a method for preparing a modified phenolic resin, comprising the following steps:

[0143] Preparation of polydimethylsiloxane containing mercapto groups:

[0144] 1 part of polydimethylsiloxane PDMS, 0.1 part of (3-mercaptopropyl)trimethoxysilane (thiol compound), and 0.03 part of potassium hydroxide (alkaline catalyst) were mixed in 20 parts of ethanol (solvent), and mechanically stirred for 20 minutes to obtain polydimethylsiloxane containing mercapto groups;

[0145] The mass ratio of polydimethylsiloxane PDMS to the thiol compound is 1:0.1; the mass of the alkaline catalyst is 0.3 times the mass of the thiol compound; the mass of the solvent is 20 times the mass of the polydimethylsiloxane PDMS;

[0146] Preparation of 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene (azobenzene containing a carbon-carbon double bond):

[0147] Step S11) using 20 parts of water as a solvent and 1 part of sodium nitrite as a solute to prepare a sodium nitrite aqueous solution; using 20 parts of ethanol as a solvent and 1 part of aniline as a solute to prepare an aniline ethanol solution; adding 1 part of nitroaniline to 3 parts of concentrated hydrochloric acid to obtain a nitroaniline solution;

[0148] Dropping a sodium nitrite aqueous solution into a nitroaniline solution, then adding the solution into an aniline ethanol solution, and mechanically stirring the solution at room temperature for 2 hours to obtain a first suspension; filtering and separating the first suspension, washing the obtained precipitate with water and ethanol, and drying the obtained precipitate to obtain 4-nitro-4′-amino-azobenzene;

[0149] In the aniline ethanol solution, the mass of ethanol is 20 times the mass of aniline; the nitroaniline solution is obtained by adding nitroaniline to concentrated hydrochloric acid; the concentration of concentrated hydrochloric acid is 38%; the mass of concentrated hydrochloric acid is 3 times the mass of nitroaniline; the molar mass ratio of nitroaniline, sodium nitrite, aniline and concentrated hydrochloric acid is 1:1:1.05:1.05;

[0150] Step S12) 20 parts of acetone as a solvent, 1 part of 4-nitro-4′-amino-azobenzene and 1 part of maleic anhydride as a solvent are mixed, and mechanically stirred at 60° C. for 6 hours to obtain a second suspension; the second suspension is filtered, and a precipitate is obtained after washing with ethyl acetate;

[0151] Using 20 parts of acetone as a solvent, the above precipitate is mixed with 1 part of triethylamine, and mechanically stirred at 60°C for 20 minutes to dissolve the above precipitate; then 6 parts of acetic anhydride and 0.02 parts of manganese acetate are added, and stirred at 60°C for 6 hours to obtain a mixed solution; after cooling to room temperature, the mixed solution is separated and purified by column chromatography (the solvent is petroleum ether and ethyl acetate, and the volume ratio is 1:1) to obtain 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene;

[0152] The mass of the solvent is 20 times the mass of 4-nitro-4′-amino-azobenzene; the mass of triethylamine is 0.03 times the mass of 4-nitro-4′-amino-azobenzene; the molar mass ratio of 4-nitro-4′-amino-azobenzene, maleic anhydride, triethylamine and acetic anhydride is 1:1:1.05:6.5;

[0153] 100 parts of the above mercapto-containing polydimethylsiloxane, 1 part of 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene, and 0.02 parts of triethylamine (catalyst) were mixed for 72 hours to obtain azobenzene-modified polydimethylsiloxane;

[0154] 1 part of phenol, 2.5 parts of formaldehyde, and 0.1 part of azobenzene-modified polydimethylsiloxane are mixed in 20 parts of ethanol solvent, sodium hydroxide is added as a catalyst, and the pH value is adjusted to 8 to obtain a modified phenolic resin;

[0155] The molar ratio of phenol to formaldehyde is 1:2.5; phenol and formaldehyde undergo polycondensation to obtain phenolic resin; the mass of azobenzene-modified polydimethylsiloxane is 15% of the mass of the phenolic resin; ethanol is used as the solvent, and the added amount thereof is 20 times the mass of the azobenzene-modified polydimethylsiloxane.

[0156] This embodiment also provides a method for preparing a phenolic resin composite material, comprising the following steps:

[0157] Impregnation step: placing the glass fiber cloth (fiber fabric) into a mold, injecting the modified phenolic resin at a pressure of 1.5 MPa (impregnation pressure) to impregnate the glass fiber cloth with the modified phenolic resin to obtain a fabric intermediate; wherein the mass ratio of the modified phenolic resin to the glass fiber cloth is 1.5:1;

[0158] Curing step: placing the above fabric intermediate in an oven and performing a curing reaction at a temperature of 160° C. for 8 hours to obtain a phenolic resin composite material.

[0159] Comparative Example

[0160] This comparative example provides a method for preparing a phenolic resin composite material, comprising the following steps:

[0161] Impregnation step: placing the glass fiber cloth (fiber fabric) into a mold, injecting the phenolic resin at a pressure of 1.5 MPa (impregnation pressure) to impregnate the glass fiber cloth with the phenolic resin to obtain a fabric intermediate; wherein the mass ratio of the phenolic resin to the glass fiber cloth is 1.5:1;

[0162] The phenolic resin is prepared by the following method: 1 part of phenol and 1.5 parts of formaldehyde are mixed in 5 parts of ethanol solvent, sodium hydroxide is added as a catalyst, and the pH value is adjusted to 8 to obtain the phenolic resin;

[0163] Curing step: placing the above fabric intermediate in an oven and performing a curing reaction at a temperature of 160° C. for 8 hours to obtain a phenolic resin composite material.

[0164] The phenolic resin composite materials prepared in Examples 1-3 and Comparative Example 1 of the present invention were subjected to performance tests (contact angles). The test results are shown in Table 1.

[0165] Table 1

[0166] Contact angle (visible light) Contact angle (365nm UV irradiation) Example 1 81.25° 65.96° Example 2 82.96° 64.25° Example 3 83.25° 62.86° Comparative Example 1 63.86° 64.16°

[0167] It can be seen from Table 1 that compared with Comparative Example 1, the contact angles of the phenolic resin composites prepared in Examples 1-3 of the present invention under visible light are increased, and the higher the contact angle, the higher the hydrophobicity of the composite. Under 365nm ultraviolet light irradiation, the contact angles of Examples 1-3 are similar to those of Comparative Example 1, indicating that Examples 1-3 exhibit hydrophilicity at this time.

[0168] It is easy for those skilled in the art to understand that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0169] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present invention. These improvements and variations should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a modified phenolic resin, characterized in that: The following steps are involved: The raw materials are mixed in a solvent, and the pH value is adjusted to a set pH value to obtain a modified phenolic resin; Wherein, the raw materials include phenol, formaldehyde and azobenzene-modified polydimethylsiloxane; Wherein, the structural formula of the azobenzene-modified polydimethylsiloxane is as follows:

2. The method for preparing a modified phenolic resin according to claim 1, wherein The preparation steps of the azobenzene-modified polydimethylsiloxane include: The polydimethylsiloxane containing a mercapto group, azobenzene containing a carbon-carbon double bond, and a catalyst are mixed and reacted to obtain the azobenzene-modified polydimethylsiloxane; Preferably, the reaction time is 12 to 72 hours; Preferably, the mass ratio of the azobenzene containing carbon-carbon double bonds to the polydimethylsiloxane containing mercapto groups is 1:100-105; Preferably, the catalyst is triethylamine; Preferably, the mass of the catalyst is 0.02 to 0.03 times the mass of azobenzene containing a carbon-carbon double bond; Preferably, the structural formula of the mercapto-containing polydimethylsiloxane is as follows: Preferably, the structural formula of the azobenzene containing a carbon-carbon double bond is as follows:

3. The method for preparing the modified phenolic resin according to claim 2, characterized in that: The step of preparing the polydimethylsiloxane containing mercapto group comprises: The polydimethylsiloxane (PDMS), a thiol compound and an alkaline catalyst are mixed in a solvent to obtain the polydimethylsiloxane containing a thiol group after reaction; Preferably, the mass ratio of the polydimethylsiloxane PDMS to the thiol compound is 1:0.05-0.1; Preferably, the mass of the alkaline catalyst is 0.1 to 0.3 times the mass of the thiol compound; Preferably, the mass of the solvent is 10 to 20 times the mass of polydimethylsiloxane PDMS; Preferably, the thiol compound is (3-mercaptopropyl)trimethoxysilane; Preferably, the catalyst is potassium hydroxide; Preferably, the solvent is acetone; Preferably, the blending method is mechanical stirring.

4. The method for preparing the modified phenolic resin according to claim 2, characterized in that: The azobenzene containing a carbon-carbon double bond is 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene; Preferably, the preparation steps of 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene include: Step S11) mixing nitroaniline solution, aniline ethanol solution and sodium nitrite aqueous solution to make nitroaniline and aniline react with each other to obtain a first suspension; filtering, washing and drying the first suspension to obtain 4-nitro-4′-amino-azobenzene; Step S12) blending the 4-nitro-4′-amino-azobenzene and maleic anhydride in a solvent to allow the 4-nitro-4′-amino-azobenzene and maleic anhydride to undergo a second reaction to obtain a second suspension; filtering and washing the second suspension to obtain a precipitate; The precipitate is mixed with a triethylamine solution, and then acetic anhydride and manganese acetate are added to obtain a mixed solution; the mixed solution is separated and purified to obtain the 4-(pyrrole-2,5-dione)benzene-4-nitro-azobenzene.

5. The method for preparing the modified phenolic resin according to claim 4, characterized in that: In the step S11): in the aniline ethanol solution, the mass of ethanol is 10 to 20 times the mass of aniline; and / or The nitroaniline solution is obtained by adding nitroaniline to concentrated hydrochloric acid; preferably, the concentration of the concentrated hydrochloric acid is 36% to 38%; preferably, the mass of the concentrated hydrochloric acid is 2.5 to 3 times the mass of the nitroaniline; and / or The molar mass ratio of the nitroaniline, sodium nitrite, aniline and concentrated hydrochloric acid is 1:1-1.05:1-1.05:1-1.05; and / or The blending method is mechanical stirring; preferably, the mechanical stirring time is 2 to 4 hours; and / or After filtering the first suspension, it is washed with water and ethanol in sequence.

6. The method for preparing the modified phenolic resin according to claim 4, characterized in that: In the step S12), the mass of the solvent is 10 to 20 times the mass of 4-nitro-4′-amino-azobenzene; the solvent is acetone; and / or The blending method is mechanical stirring; preferably, the mechanical stirring is carried out at 60-80° C.; the stirring time is 4 to 6 hours; and / or The mass of triethylamine is 0.02 to 0.03 times the mass of 4-nitro-4′-amino-azobenzene; and / or Before the step of adding acetic anhydride and manganese acetate, the method further comprises: a first stirring step; preferably, the first stirring step is performed at 60-80° C.; preferably, the first stirring step lasts for 5 to 20 minutes; and / or The molar mass ratio of the 4-nitro-4′-amino-azobenzene, maleic anhydride, triethylamine and acetic anhydride is 1:1-1.05:1-1.05:6-6.5; and / or After the step of adding acetic anhydride and manganese acetate, the method further comprises: a second stirring step; preferably, the second stirring step is performed at 60 to 80° C.; preferably, the second stirring step lasts for 4 to 6 hours; and / or The mixed solution is separated and purified by column chromatography; preferably, the solvents used in the column chromatography are petroleum ether and ethyl acetate; wherein the volume ratio of petroleum ether to ethyl acetate is 1:1-1.

5.

7. The method for preparing the modified phenolic resin according to claim 1, characterized in that: The phenol and formaldehyde undergo a polycondensation reaction to obtain a phenolic resin; preferably, the mass of the azobenzene-modified polydimethylsiloxane is 5% to 15% of the mass of the phenolic resin; and / or The molar ratio of phenol to formaldehyde is 1:1.5-2.5; and / or The amount of the solvent added is 10 to 20 times the mass of the azobenzene-modified polydimethylsiloxane; preferably, the solvent is ethanol; and / or The set pH value is 8 to 11; and / or The pH value is adjusted using an alkaline catalyst; preferably, the alkaline catalyst is one or more of sodium hydroxide, magnesium hydroxide, barium hydroxide, and aluminum hydroxide; preferably, the amount of the alkaline catalyst is 0.1 to 0.3 times the mass of phenol.

8. A modified phenolic resin, characterized in that: The modified phenolic resin comprises a phenolic resin and azobenzene-modified polydimethylsiloxane dispersed on the phenolic resin; Preferably, the modified phenolic resin is obtained by the preparation method according to any one of claims 1 to 7.

9. A method for preparing a phenolic resin composite material, characterized in that: The following steps are involved: Impregnation step: impregnating the fiber fabric with modified phenolic resin to obtain a fabric intermediate; Curing step: performing a curing reaction on the fabric intermediate to obtain a phenolic resin composite material; Preferably, in the impregnation step: the modified phenolic resin is the modified phenolic resin according to claim 8; Preferably, the step of impregnating the fiber fabric with the modified phenolic resin comprises: applying the modified phenolic resin to the surface of the fiber fabric, and brushing the modified phenolic resin flat with a pressure roller; further preferably, the mass of the modified phenolic resin applied to the surface of the fiber fabric is 5-10% of the mass of the fiber fabric; Preferably, the impregnation pressure is 1.2 to 1.5 MPa; Preferably, the curing reaction temperature is 120-160° C., and the curing reaction time is 8-12 hours.

10. A phenolic resin composite material, characterized in that: Under visible light, the contact angle of the phenolic resin composite material is greater than 81°; Under ultraviolet light of 365 nm, the contact angle of the phenolic resin composite material is less than 66°; Preferably, the phenolic resin composite material is obtained by the preparation method described in claim 9.

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