Benzoxazine-type phthalonitrile monomer containing siloxane chain segment and preparation method thereof

Abstract

The invention belongs to the technical field of polymer materials, and specifically relates to a benzoxazine-type phthalonitrile monomer containing a siloxane chain segment and a preparation method thereof. The benzoxazine-type phthalonitrile resin is prepared by structural design, and the phenolic hydroxyl group formed by the ring-opening of the oxazine ring can promote the polymerization of the cyano group, realize the self-catalytic curing reaction of the cyano group, thereby reducing the curing temperature; the silicon-oxygen chain segment is introduced into the molecular structure, and the molecular chain mobility is improved by reducing the rotation energy barrier of the molecular chain, thereby reducing the melting point of the resin.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, in particular to a benzoxazine-type phthalonitrile monomer containing a siloxane segment and a preparation method thereof. Background Art

[0002] Compared with traditional lightweight alloy materials, resin-based composite materials have lower density, higher specific strength, and highly flexible structural design. With the continuous development of the demand for structural weight reduction, resin-based composite materials are being increasingly used in aerospace, high-end automobile and other fields.

[0003] Phthalonitrile is a type of aromatic monomer containing dicyano groups. Phthalonitrile monomers can be cross-linked with cyano groups under heating conditions to obtain phthalonitrile resins containing triazine rings, isoindole rings and phthalocyanine ring structures. The mechanical and heat resistance properties of fully cured phthalonitrile resins are excellent, and the glass transition temperature can exceed 400°C, which exceeds most types of polyimide resins. However, the melting point and curing temperature of phthalonitrile monomers are usually high, which makes the resin difficult to process, the processing window is narrow, and the product is prone to defects. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the main purpose of the present invention is to provide a benzoxazine-type phthalonitrile monomer containing a siloxane segment and a preparation method thereof.

[0005] To solve the above technical problems, according to one aspect of the present invention, the present invention provides the following technical solutions:

[0006] A benzoxazine-type phthalonitrile monomer containing a siloxane segment has a structure of the following molecular formula 1 or molecular formula 2:

[0007] Molecular formula 1:

[0008]

[0009] Molecular formula 2:

[0010]

[0011] in,

[0012] R1, R2, R5, and R6 are each independently an alkyl group, an alkoxy group, or an aryl group;

[0013] R3, R4, R7, R8, R9, and R10 are each independently alkyl, alkoxy, or aryl, or halogen, or halogenated alkyl;

[0014] V1 and V2 are divalent groups, which may be alkylene, alkylidene, -O-, -S-, -C(=O)-, -S(=O)-, -S(=O)2-, -C(=O)-O-L1-OC(=O)-, -L2-C(=O)-O-L3-, -L4-OC(=O)-L5- or -L6-Ar1-L7-Ar2-L8-, L1~L8 are each independently a single bond, -O-, alkylene or alkylidene, and Ar1 and Ar2 are each independently an arylene;

[0015] U1~U4 are divalent groups, which are the aminophenol structures except -NH 2 and structures other than -OH functional groups.

[0016] As a preferred embodiment of the benzoxazine-type phthalonitrile monomer containing a siloxane segment of the present invention, wherein: the specific structures of U1 to U4 are as shown in Molecular Formula 3 to Molecular Formula 6:

[0017]

[0018] in,

[0019] R11 to R15 represent substituents on the benzene ring, each independently being an alkyl group, an alkoxy group, an aryl group, a halogen atom or a halogenated alkyl group;

[0020] X is a divalent group, which is an alkylene group, an alkylidene group, -O-, -S-, -C(=O)-, -S(=O)-, -S(=O)2-, -C(=O)-O-L1-OC(=O)-, -L2-C(=O)-O-L3-, -L4-OC(=O)-L5- or -L6-Ar1-L7-Ar2-L8-, L1 to L8 are each independently a single bond, -O-, an alkylene group or an alkylidene group, and Ar1 and Ar2 are each independently an arylene group.

[0021] To solve the above technical problem, according to another aspect of the present invention, the present invention provides the following technical solution:

[0022] A method for preparing the above-mentioned benzoxazine-type phthalonitrile monomer containing a siloxane segment comprises the following steps:

[0023] S1, synthesizing amino-terminated phthalonitrile monomer;

[0024] S2, synthesizing benzoxazine-type phthalonitrile intermediates;

[0025] S3, benzoxazine-type phthalonitrile monomer containing siloxane chain segments.

[0026] As a preferred embodiment of the method for preparing the benzoxazine-type phthalonitrile monomer containing a siloxane segment of the present invention, wherein: in the step S1, the aminophenol monomer and anhydrous potassium carbonate are mixed in a polar aprotic solvent at a molar ratio of 1:1.2-1.5, and the reaction system is heated to 60-90° C. under the protection of an inert gas, and refluxed for reaction for 1-2 hours; then 4-nitrophthalonitrile is added to the reaction solution, and the reaction is continued for 2-3 hours; then, the filtrate is filtered, and the filtrate is poured into 5-10 times the volume of 0.1 mol / L dilute hydrochloric acid to precipitate a precipitate, which is then washed with ethanol to obtain an amino-terminated phthalonitrile monomer.

[0027] As a preferred embodiment of the method for preparing the benzoxazine-type phthalonitrile monomer containing a siloxane segment according to the present invention, wherein: in the step S1, the polar aprotic solvent includes one or more of dimethyl sulfoxide, dimethylformamide, and dimethylacetamide, and the weight of the solvent is 3 to 5 times the total mass of the reactants.

[0028] As a preferred embodiment of the method for preparing the benzoxazine-type phthalonitrile monomer containing a siloxane segment according to the present invention, wherein: in the step S1, the aminophenol monomer includes p-aminophenol, m-aminophenol, 4-amino-4'-hydroxydiphenyl ether, 4-amino-4'-hydroxydiphenyl sulfone and aromatic substituents of the above monomers.

[0029] As a preferred embodiment of the method for preparing the benzoxazine-type phthalonitrile monomer containing a siloxane segment of the present invention, wherein: in the step S2, the amino-terminated phthalonitrile monomer, the hydroxybenzyl alcohol monomer, and the paraformaldehyde obtained in the step S1 are dissolved in a mixed solvent consisting of toluene and dioxane at a molar ratio of 1:1:1.1-1.2, and under the protection of an inert gas, the reaction system is heated to 100-150° C., refluxed at a constant temperature for 5-8 hours, and distilled under reduced pressure to remove the solvent, and the crude product is washed with hot ethanol to obtain a benzoxazine-type phthalonitrile intermediate.

[0030] As a preferred embodiment of the method for preparing the benzoxazine-type phthalonitrile monomer containing a siloxane segment of the present invention, wherein: in the step S2, the hydroxybenzyl alcohol monomer includes p-hydroxybenzyl alcohol and its aromatic substituents, m-hydroxybenzyl alcohol, 4-hydroxymethyl-4'-hydroxydiphenyl ether, 3-hydroxymethyl-3'-hydroxydiphenyl ether, 4-hydroxymethyl-4'-hydroxybiphenyl, 4-hydroxymethyl-4'-hydroxybiphenyl and aromatic substituents of the above monomers.

[0031] As a preferred embodiment of the method for preparing the benzoxazine-type phthalonitrile monomer containing a siloxane chain segment of the present invention, wherein: in the step S3, the benzoxazine-type phthalonitrile intermediate obtained in step S2, dichlorosilane, and triethylamine are dissolved in a mixed solvent consisting of toluene and dioxane at a molar ratio of 2-2.2:1:2, and reacted at 30-50° C. for 3-5 hours, and the precipitate produced by the reaction is collected, washed with tetrahydrofuran, and dried to obtain the benzoxazine-type phthalonitrile monomer containing a siloxane chain segment.

[0032] As a preferred embodiment of the method for preparing the benzoxazine-type phthalonitrile monomer containing a siloxane segment of the present invention, wherein: in the steps S2 and S3, the volume ratio of the mixed solvent composed of toluene and dioxane is 1:3-4, and the total mass of the solvent is 3-5 times the total mass of the reactants.

[0033] To solve the above technical problem, according to another aspect of the present invention, the present invention provides the following technical solution:

[0034] A phthalonitrile resin is obtained by curing the above-mentioned benzoxazine-type phthalonitrile monomer containing siloxane chain segments.

[0035] As a preferred embodiment of the phthalonitrile resin of the present invention, the curing process is: keeping warm at 220°C for 1 hour, keeping warm at 250°C for 1 hour, keeping warm at 280°C for 2 hours, and keeping warm at 320°C for 2 hours.

[0036] The beneficial effects of the present invention are as follows:

[0037] The invention provides a benzoxazine-type phthalonitrile monomer containing a siloxane chain segment and a preparation method thereof. A benzoxazine-type phthalonitrile resin is prepared by structural design. The phenolic hydroxyl group formed by the ring-opening of the oxazine ring can promote the polymerization of the cyano group, realize the self-catalytic curing reaction of the cyano group, and thus reduce the curing temperature. The silicon-oxygen chain segment is introduced into the molecular structure, and the molecular chain mobility is improved by reducing the rotation energy barrier of the molecular chain, thereby reducing the melting point of the resin. DETAILED DESCRIPTION

[0038] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] The invention provides a benzoxazine-type phthalonitrile monomer containing a siloxane chain segment and a preparation method thereof. On the one hand, the phenolic hydroxyl group of the ring-opening of the oxazine ring can promote the polymerization of the cyano group, realize the self-catalytic curing reaction of the cyano group, and thus reduce the curing temperature of the phthalonitrile resin; on the other hand, the siloxane chain segment has excellent conformational flexibility, can increase the spatial mobility of the molecular chain, thereby significantly reducing the melting point of the monomer, and ultimately improving the processing window of the monomer; in addition, the Si-O bond has a relatively high bond energy, so after the Si-O chain segment is introduced, the heat resistance of the cured product will not be significantly affected.

[0040] According to one aspect of the present invention, the present invention provides the following technical solution:

[0041] A benzoxazine-type phthalonitrile monomer containing a siloxane segment has a structure of the following molecular formula 1 or molecular formula 2:

[0042] Molecular formula 1:

[0043]

[0044] Molecular formula 2:

[0045]

[0046] in,

[0047] R1, R2, R5, and R6 are each independently an alkyl group, an alkoxy group, or an aryl group;

[0048] R3, R4, R7, R8, R9, and R10 are each independently alkyl, alkoxy, or aryl, or halogen, or halogenated alkyl;

[0049] V1 and V2 are divalent groups, which may be alkylene, alkylidene, -O-, -S-, -C(=O)-, -S(=O)-, -S(=O)2-, -C(=O)-O-L1-OC(=O)-, -L2-C(=O)-O-L3-, -L4-OC(=O)-L5- or -L6-Ar1-L7-Ar2-L8-, L1~L8 are each independently a single bond, -O-, alkylene or alkylidene, and Ar1 and Ar2 are each independently an arylene;

[0050] U1~U4 are divalent groups, which are the aminophenol structures except -NH 2 and structures other than -OH functional groups.

[0051] Preferably, the specific structures of U1 to U4 are as shown in Molecular Formula 3 to Molecular Formula 6:

[0052]

[0053] in,

[0054] R11 to R15 represent substituents on the benzene ring, each independently being an alkyl group, an alkoxy group, an aryl group, a halogen atom or a halogenated alkyl group;

[0055] X is a divalent group, which is an alkylene group, an alkylidene group, -O-, -S-, -C(=O)-, -S(=O)-, -S(=O)2-, -C(=O)-O-L1-OC(=O)-, -L2-C(=O)-O-L3-, -L4-OC(=O)-L5- or -L6-Ar1-L7-Ar2-L8-, L1 to L8 are each independently a single bond, -O-, an alkylene group or an alkylidene group, and Ar1 and Ar2 are each independently an arylene group.

[0056] According to another aspect of the present invention, the present invention provides the following technical solution:

[0057] A method for preparing the above-mentioned benzoxazine-type phthalonitrile monomer containing a siloxane segment comprises the following steps:

[0058] S1, synthesizing amino-terminated phthalonitrile monomer;

[0059] S2, synthesizing benzoxazine-type phthalonitrile intermediates;

[0060] S3, benzoxazine-type phthalonitrile monomer containing siloxane chain segments.

[0061] Preferably, in step S1, the aminophenol monomer and anhydrous potassium carbonate are mixed in a polar aprotic solvent at a molar ratio of 1:1.2-1.5, and the reaction system is heated to 60-90°C under the protection of an inert gas, and refluxed for 1-2 hours; then 4-nitrophthalonitrile is added to the reaction solution, and the reaction is continued for 2-3 hours; then, the filtrate is filtered, and the filtrate is poured into 5-10 times the volume of 0.1 mol / L dilute hydrochloric acid to precipitate a precipitate, which is then washed with ethanol to obtain an amino-terminated phthalonitrile monomer. The reaction principle is as follows.

[0062]

[0063] Preferably, in step S1, the polar aprotic solvent includes one or more of dimethyl sulfoxide, dimethylformamide, and dimethylacetamide, and the weight of the solvent is 3 to 5 times the total mass of the reactants.

[0064] Preferably, in step S1, the aminophenol monomers include p-aminophenol, m-aminophenol, 4-amino-4'-hydroxydiphenyl ether, 4-amino-4'-hydroxydiphenyl sulfone and aromatic substituents of the above monomers.

[0065] Preferably, in the step S2, the amino-terminated phthalonitrile monomer, hydroxybenzyl alcohol monomer and paraformaldehyde obtained in the step S1 are dissolved in a mixed solvent consisting of toluene and dioxane at a molar ratio of 1:1:1.1-1.2, and the reaction system is heated to 100-150° C. under the protection of an inert gas, refluxed at a constant temperature for 5-8 hours, and distilled under reduced pressure to remove the solvent, and the crude product is washed with hot ethanol to obtain a benzoxazine-type phthalonitrile intermediate. The reaction principle is as follows.

[0066]

[0067] Preferably, in step S2, the hydroxybenzyl alcohol monomer includes p-hydroxybenzyl alcohol and its aromatic substituents, m-hydroxybenzyl alcohol, 4-hydroxymethyl-4'-hydroxydiphenyl ether, 3-hydroxymethyl-3'-hydroxydiphenyl ether, 4-hydroxymethyl-4'-hydroxybiphenyl, 4-hydroxymethyl-4'-hydroxybiphenyl and aromatic substituents of the above monomers.

[0068] Preferably, in the step S3, the benzoxazine-type phthalonitrile intermediate obtained in step S2, dichlorosilane and triethylamine are dissolved in a mixed solvent consisting of toluene and dioxane at a molar ratio of 2-2.2:1:2, and the mixture is reacted at 30-50° C. for 3-5 hours. The precipitate produced by the reaction is collected, washed with tetrahydrofuran, and dried to obtain a benzoxazine-type phthalonitrile monomer containing a siloxane segment. The reaction principle is as follows.

[0069]

[0070] Preferably, in steps S2 and S3, the volume ratio of the mixed solvent composed of toluene and dioxane is 1:3-4, and the total mass of the solvent is 3-5 times the total mass of the reactants.

[0071] According to another aspect of the present invention, the present invention provides the following technical solution:

[0072] A phthalonitrile resin is obtained by curing the above-mentioned benzoxazine-type phthalonitrile monomer containing siloxane chain segments.

[0073] Preferably, the curing process is: keeping warm at 220°C for 1 hour, keeping warm at 250°C for 1 hour, keeping warm at 280°C for 2 hours, and keeping warm at 320°C for 2 hours.

[0074] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0075] Example 1

[0076] A method for preparing a benzoxazine-type phthalonitrile monomer containing a siloxane segment comprises the following steps:

[0077] S1. Synthesis of amino-terminated phthalonitrile monomer

[0078] Para-aminophenol and anhydrous potassium carbonate were mixed in a polar aprotic solvent at a molar ratio of 1:1.2. Under the protection of inert gas, the reaction system was heated to 80°C and refluxed for 2 hours. 4-nitrophthalonitrile was then added to the reaction solution and the reaction continued for 3 hours. Afterwards, the filtrate was filtered and poured into 5-10 times the volume of 0.1 mol / L dilute hydrochloric acid to precipitate the precipitate, which was then washed with ethanol to obtain an amino-terminated phthalonitrile monomer. The reaction principle is shown below.

[0079]

[0080] S2. Synthesis of benzoxazine-type phthalonitrile intermediates

[0081] The amino-terminated phthalonitrile monomer, p-hydroxybenzyl alcohol monomer, and paraformaldehyde obtained in step S1 are dissolved in a mixed solvent consisting of toluene and dioxane (the volume ratio of toluene and dioxane is 1:4) at a molar ratio of 1:1:1.1. Under the protection of inert gas, the reaction system is heated to 120°C and refluxed at a constant temperature for 6 hours. The solvent is removed by vacuum distillation, and the crude product is washed with hot ethanol to obtain a benzoxazine-type phthalonitrile intermediate. The reaction principle is as follows.

[0082]

[0083] S3, benzoxazine-type phthalonitrile monomer containing siloxane segments

[0084] The benzoxazine-type phthalonitrile intermediate obtained in step S2, dichlorodimethylsilane, and triethylamine are dissolved in a mixed solvent consisting of toluene and dioxane (the volume ratio of toluene and dioxane is 1:4) at a molar ratio of 2-2.2:1:2, and the reaction is carried out at 35° C. for 4 hours. The precipitate produced by the reaction is collected, washed with tetrahydrofuran, and dried to obtain a benzoxazine-type phthalonitrile monomer containing a siloxane segment, and its molecular formula is shown below.

[0085]

[0086] A phthalonitrile resin is obtained by curing the benzoxazine-type phthalonitrile monomer containing a siloxane segment obtained in this embodiment at 220° C. / 1 h, 250° C. / 1 h, 280° C. / 2 h, and 320° C. / 2 h.

[0087] Example 2

[0088] The difference from Example 1 is that

[0089] The p-aminophenol in step S1 is replaced by m-aminophenol;

[0090] The p-hydroxybenzyl alcohol in step S2 is replaced by m-aminophenol;

[0091] The molecular formula of the obtained benzoxazine-type phthalonitrile monomer containing a siloxane segment is shown below.

[0092]

[0093] A phthalonitrile resin is obtained by curing the benzoxazine-type phthalonitrile monomer containing a siloxane segment obtained in this embodiment at 220° C. / 1 h, 250° C. / 1 h, 280° C. / 2 h, and 320° C. / 2 h.

[0094] Example 3

[0095] The difference from Example 1 is that

[0096] The p-hydroxybenzyl alcohol in step S2 is replaced by 4-hydroxy-4'-hydroxymethylbiphenyl;

[0097] The molecular formula of the obtained benzoxazine-type phthalonitrile monomer containing a siloxane segment is shown below.

[0098]

[0099] A phthalonitrile resin is obtained by curing the benzoxazine-type phthalonitrile monomer containing a siloxane segment obtained in this embodiment at 220° C. / 1 h, 250° C. / 1 h, 280° C. / 2 h, and 320° C. / 2 h.

[0100] Comparative Example 1

[0101] This comparative example is prepared according to the following steps:

[0102] Add bisphenol A, 4-nitrophthalonitrile, and anhydrous potassium carbonate to the reactor in a molar ratio of 1:2:1.2, add N,N-dimethylformamide as a solvent at a volume of 5 times the total mass of the reactants, and react at 85°C for 5 hours under nitrogen protection. Pour the reaction solution into 0.1 mol / L dilute hydrochloric acid at a volume of 5 times the volume of the reaction solution to precipitate and filter, repeatedly wash and precipitate until neutral, and obtain bisphenol A type phthalonitrile monomer, the molecular formula of which is shown below.

[0103]

[0104] The obtained bisphenol A type phthalonitrile monomer was cured at 220° C. / 1 h, 250° C. / 1 h, 320° C. / 2 h, and 350° C. / 2 h to obtain phthalonitrile resin.

[0105] Comparative Example 2

[0106] The phthalonitrile monomer was prepared according to the method of Comparative Example 1, except that bisphenol A was replaced with 4,4'-dihydroxydiphenyl ether, and the rest was the same as Comparative Example 1. The molecular formula of the prepared phthalonitrile monomer is shown below.

[0107]

[0108] The obtained phthalonitrile monomer was cured at 220° C. / 1 h, 250° C. / 1 h, 320° C. / 2 h, and 350° C. / 2 h to obtain phthalonitrile resin.

[0109] Comparative Example 3

[0110] The preparation of a phthalonitrile monomer containing a benzoxazine structure and no siloxane segment comprises the following steps:

[0111] S1, same as step S1 of embodiment 1;

[0112] S2. The amino-terminated phthalonitrile monomer, bisphenol A, and paraformaldehyde obtained in step S1 are dissolved in a mixed solvent consisting of toluene and dioxane (the volume ratio of toluene and dioxane is 1:4) at a molar ratio of 2:1:2.2. Under the protection of an inert gas, the reaction system is heated to 110° C. and refluxed at a constant temperature for 6 hours. The solvent is removed by distillation under reduced pressure, and the crude product is washed with hot ethanol to obtain a bisphenol A-type phthalonitrile monomer containing a benzoxazine functional group, the molecular formula of which is shown below.

[0113]

[0114] The obtained bisphenol A type benzoxazine functional group-containing phthalonitrile monomer is cured at 220° C. / 1 h, 250° C. / 1 h, and 280° C. / 4 h to obtain a bisphenol A type benzoxazine functional group-containing phthalonitrile resin.

[0115] The properties of the resins formed by curing the phthalonitrile monomers prepared in Examples 1-3 and Comparative Examples 1-3 were tested (the curing temperature was determined by the DSC method, which was determined by the peak temperature of the curing heat protection; the initial pyrolysis temperature was obtained by thermogravimetric analysis, which was the 5% thermal weight loss temperature; the glass transition temperature was determined by the DSC method), and the results are shown in the following table.

[0116]

[0117] It can be seen from the above table that the melting point of the resin formed by curing the benzoxazine-type phthalonitrile monomer containing siloxane segments prepared by the preparation method of the present invention is significantly lower than the melting point of the resin formed by curing the conventional phthalonitrile monomer, and the thermal stability and mechanical properties are comparable to those of the conventional phthalonitrile resin.

[0118] The present invention prepares benzoxazine-type phthalonitrile resin through structural design. The phenolic hydroxyl group formed by the opening of the oxazine ring can promote the polymerization of cyano groups, realize the self-catalytic curing reaction of cyano groups, and thus reduce the curing temperature; silicon-oxygen chain segments are introduced into the molecular structure, and the molecular chain mobility is improved by reducing the rotation energy barrier of the molecular chain, thereby reducing the melting point of the resin.

[0119] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A benzoxazine-type phthalonitrile monomer containing a siloxane segment, It is characterized in that It has the following structure of formula 1 or formula 2: Molecular formula 1: Molecular formula 2: in, R1 and R2 are each independently an alkyl group or an alkoxy group; R3 and R4 are each independently alkyl, alkoxy or halogen or halogenated alkyl; The specific structures of U1~U2 are shown in Molecular Formula 3~Molecular Formula 5: Among them, * indicates the connection position; R11 to R13 represent substituents on the benzene ring, and are each independently an alkyl group, an alkoxy group, a halogen atom or a halogenated alkyl group.

2. A method for preparing the benzoxazine-type phthalonitrile monomer containing a siloxane segment according to claim 1, It is characterized in that The steps include: S1, synthesize amino-terminated phthalonitrile monomer, the reaction formula is as follows: ； S2, synthesizing benzoxazine-type phthalonitrile intermediate, the reaction formula is as follows: ， Among them, (CH 2 O) n It is paraformaldehyde; S3, synthesizing a benzoxazine-type phthalonitrile monomer containing a siloxane segment, the reaction formula is as follows: 。 3. The method for preparing the benzoxazine-type phthalonitrile monomer containing a siloxane segment according to claim 2, It is characterized in that In the step S1, aminophenol monomer and anhydrous potassium carbonate are mixed in a polar aprotic solvent at a molar ratio of 1:1.2-1.5, and the reaction system is heated to 60-90° C. under the protection of an inert gas, and refluxed for 1-2 hours; then 4-nitrophthalonitrile is added to the reaction solution, and the reaction is continued for 2-3 hours; then, the filtrate is filtered, and the filtrate is poured into 5-10 times the volume of 0.1 mol / L dilute hydrochloric acid to precipitate a precipitate, which is then washed with ethanol to obtain an amino-terminated phthalonitrile monomer.

4. The method for preparing the benzoxazine-type phthalonitrile monomer containing a siloxane segment according to claim 3, It is characterized in that In step S1, the polar aprotic solvent is one or more of dimethyl sulfoxide, dimethylformamide, and dimethylacetamide, and the weight of the solvent is 3 to 5 times the total mass of the reactants; and the aminophenol monomer is p-aminophenol or m-aminophenol.

5. The method for preparing the benzoxazine-type phthalonitrile monomer containing a siloxane segment according to claim 2, It is characterized in that In the step S2, the amino-terminated phthalonitrile monomer, p-hydroxybenzyl alcohol and paraformaldehyde obtained in the step S1 are dissolved in a mixed solvent consisting of toluene and dioxane at a molar ratio of 1:1:1.1-1.2, and the reaction system is heated to 100-150° C. under the protection of an inert gas, refluxed at a constant temperature for 5-8 hours, and distilled under reduced pressure to remove the solvent, and the crude product is washed with hot ethanol to obtain a benzoxazine-type phthalonitrile intermediate.

6. The method for preparing the benzoxazine-type phthalonitrile monomer containing a siloxane segment according to claim 5, It is characterized in that In the step S3, the benzoxazine-type phthalonitrile intermediate obtained in step S2, dimethyldichlorosilane and triethylamine are dissolved in a mixed solvent consisting of toluene and dioxane at a molar ratio of 2-2.2:1:2, and reacted at 30-50° C. for 3-5 hours. The precipitate produced by the reaction is collected, washed with tetrahydrofuran, and dried to obtain a benzoxazine-type phthalonitrile monomer containing a siloxane segment.

7. The method for preparing the benzoxazine-type phthalonitrile monomer containing a siloxane segment according to claim 6, It is characterized in that In the steps S2 and S3, the volume ratio of the mixed solvent composed of toluene and dioxane is 1:3-4, and the total mass of the solvent is 3-5 times the total mass of the reactants.

8. A phthalonitrile resin, It is characterized in that The product is obtained by curing the benzoxazine-type phthalonitrile monomer containing siloxane segments as described in claim 1.

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