Norbornene-silyl ether-containing benzoxazine resin as well as preparation method and application thereof

Abstract

The invention relates to the field of synthesis of novel benzoxazine resin, in particular to benzoxazine resin containing norbornene-silyl ether bonds and a preparation method of the benzoxazine resin. The preparation method comprises the following steps: mixing a phenol source containing norbornene dianhydride, an amine source containing a silyl-ether bond, paraformaldehyde and a drying agent, adding an organic solvent, heating, and reacting for 6-8 hours at the reaction temperature of 110-120 DEG C; and after the reaction is finished, filtering, recrystallizing, carrying out rotary evaporation to remove the solvent, collecting the solid, and drying to obtain the final product. According to the resin prepared by the invention, norbornene and silyl ether bonds are introduced from the perspective of molecular design, so that the benzoxazine resin has excellent heat resistance and degradability. The resin is low in cost and simple to synthesize, the preparation process is optimized, and industrial production is easy to realize.

Description

Technical Field

[0001] The present invention relates to the field of synthesis of novel benzoxazine resins, and in particular to a norbornene-silyl ether-containing benzoxazine resin and a preparation method and application thereof. Background Art

[0002] As a new type of phenolic resin, benzoxazine resin has flexible molecular design and can be endowed with special properties by introducing diversified structures to meet the needs of various application fields. For example, the introduction of dynamic covalent bonds (such as ester bonds, disulfide bonds, acetal bonds, silyl ether bonds and imide bonds) can achieve degradation; the introduction of alkenyl groups and silicon-containing groups can improve its heat resistance. Polybenzoxazine has excellent mechanical properties, heat resistance and flame retardancy, and is expected to replace traditional phenolic resins, epoxy resins and polyimide resins.

[0003] Norbornene, due to its cycloolefin structure, can increase the crosslinking density of benzoxazine after ring-opening metathesis polymerization, thus improving its heat resistance; 3-propylaminotrimethoxysilane contains silyl ether bonds, which can undergo a similar transesterification reaction, making the crosslinked polymer degradable. The presence of silicon enables the polymer to form a silicon dioxide layer at high temperatures, further improving its heat resistance. Summary of the invention

[0004] The present invention overcomes the deficiencies of the prior art and provides a benzoxazine monomer containing norbornene-silyl ether, introduces a special structure through molecular design, improves the carbon residue rate of the benzoxazine resin, and achieves degradability while ensuring good thermal properties.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a benzoxazine monomer containing norbornene-silyl ether type, the structure of which contains norbornene and silyl ether bond, and its structural formula is:

[0006]

[0007] Where -R is any of the following structures:

[0008]

[0009]

[0010]

[0011] Wherein, -R1 is any one of the following structures:

[0012]

[0013] Due to its cycloolefin structure, norbornene can increase the crosslinking density of benzoxazine after ring-opening metathesis polymerization and improve heat resistance; 3-propylaminotrimethoxysilane contains silyl ether bonds, which can undergo a similar ester exchange reaction, making the crosslinked polymer degradable. The presence of silicon allows the polymer to form a silicon dioxide layer at high temperatures, further improving heat resistance. The new benzoxazine synthesized from these two raw materials has excellent heat resistance and degradability. Degradation can alleviate environmental pollution and recover high-value components (such as carbon fiber).

[0014] The present invention also provides a method for preparing the above-mentioned norbornene-silyl ether-containing benzoxazine monomer, which specifically comprises the following steps:

[0015] A phenol source containing nadic anhydride, an amine source containing a silicon ether bond, polyformaldehyde, and a desiccant are mixed, an organic solvent is added, and then the temperature is raised to 110-120° C. and the reaction is carried out for 6-8 hours; after the reaction is completed, the product is filtered and recrystallized, the solvent is removed by rotary evaporation, and the solid is collected and dried to obtain the final product;

[0016] The reaction formula is as follows:

[0017]

[0018] As a further limitation of the technical solution of the present invention, the molar ratio of the phenol of the nadic anhydride, the amine containing a silicon ether bond, the polyformaldehyde, and the desiccant is 1:1:2:0.5-1.

[0019] As a further limitation of the technical solution of the present invention, the organic solvent is at least one of chloroform and xylene.

[0020] As a further limitation of the technical solution of the present invention, the desiccant is anhydrous sodium sulfate or calcium oxide.

[0021] As a further limitation of the technical solution of the present invention, the usage ratio of the phenol of the nadic anhydride to the organic solvent is 1 mol:2L.

[0022] As a further limitation of the technical solution of the present invention, the recrystallization method is to place the mixture in a refrigerator for 10-12 hours.

[0023] In addition, the present invention also provides the use of the above-mentioned norbornene-silyl ether-containing benzoxazine monomer in the preparation of high-temperature resistant materials, high-strength materials and recycled carbon fibers.

[0024] In addition, the present invention also provides a norbornene-silyl ether-containing polybenzoxazine thermosetting resin, which is prepared using the above-mentioned norbornene-silyl ether-containing benzoxazine monomer, and the steps are: removing the solvent from the norbornene-silyl ether-containing benzoxazine monomer in a vacuum drying oven, and then placing it in a blast drying oven, setting the temperature gradient to 160°C for 1h, 180°C for 1h, 200°C for 2h, 220°C for 2h, and 250°C for 1h for curing, and obtaining the polybenzoxazine thermosetting resin after cooling.

[0025] In addition, the present invention also provides a norbornene-silyl ether-containing polybenzoxazine thermosetting resin film, which is prepared using the above-mentioned norbornene-silyl ether-containing benzoxazine monomer, and the specific steps are: dissolving the norbornene-silyl ether-containing benzoxazine monomer in chloroform, adding it dropwise to a film mold, and then placing it in a 45°C blast oven for 12 hours to remove the solvent, and then heating and curing, setting the temperature gradient to 140°C for 1 hour, 160°C for 1 hour, 180°C for 1 hour, 200°C for 2 hours, 220°C for 2 hours, and 250°C for 1 hour for curing, and obtaining the polybenzoxazine thermosetting resin film after cooling.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The resin prepared by the invention introduces norbornene and silyl ether bonds from the perspective of molecular design, so that the benzoxazine resin has excellent heat resistance and degradability.

[0028] The resin of the invention has low cost, simple synthesis, optimized preparation process and is easy to realize industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The H NMR spectrum (a) and IR spectrum (b) of the benzoxazine obtained in Example 1 of the present invention are shown.

[0030] Figure 2 The DSC (a) and heat resistance TGA (b) curves of the benzoxazine obtained in Example 2 of the present invention are shown.

[0031] Figure 3 The prepared film of benzoxazine obtained in Example 3 of the present invention (a) and its water contact angle test (b).

[0032] Figure 4 This is a degradation diagram of the benzoxazine polymer obtained in Example 2 of the present invention at different time periods under alkaline conditions.

[0033] Figure 5 This is a graph showing the degradation rate of the benzoxazine polymer obtained in Example 2 of the present invention under alkaline (0.1-1 M NaOH) conditions at different temperatures (Figure a is 50° C., Figure b is room temperature).

[0034] Figure 6 The infrared spectrum (a) and degradation mechanism diagram (b) of the benzoxazine polymer obtained in Example 2 of the present invention under alkaline conditions. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with specific embodiments.

[0036] Example 1

[0037] A method for preparing a norbornene-silyl ether-containing benzoxazine, comprising the following specific steps:

[0038] 1.5g (0.05mol) of paraformaldehyde and 1.77g of anhydrous sodium sulfate were added to 50ml of xylene solvent, stirred at 40℃ in a constant temperature oil bath for 30min until the solution turned gray and had no granularity, then 6.38g (0.025mol) of phenol (OHPNI) of nadic anhydride was added and stirred for 30min, and then 4.48g (0.025mol) of amine source 3-propylaminobenzoxazine was added dropwise at a rate of one drop per second, the temperature was raised to 120℃, N2 was introduced and stirred for 6h, recrystallized and rotary evaporated, and then vacuum dried to obtain the product, which is a new benzoxazine monomer with a yield of 63.1%. The reaction formula is:

[0039]

[0040] Figure 1 (a) is a benzoxazine H NMR spectrum of Example 1. In the figure, a characteristic peak of hydrogen atoms on the diene ring with a carbon-carbon double bond can be observed at 6.25 ppm. In addition, a proton peak on the oxazine ring (Ar-CH2-N) is found at 3.98 ppm, and a chemical shift of 4.84 ppm corresponds to hydrogen atoms on the oxazine ring (Ar-O-CH2). The characteristic peak of the proton peak on the methyl group connected to siloxane appears at 3.56 ppm. Together with the other H atom peak positions marked on the figure, the basic structure of the new benzoxazine molecule can be determined. Figure 1 (b) is the infrared spectrum of benzoxazine of the present invention. -1 The peak at 695 cm is the characteristic peak of the oxazine ring. -1 The absorption peak of the vibration peak of the cyclic olefin on norbornene is 1072 cm -1 The peak at is the vibration absorption peak of Si-O-CH3 structure. Figure 1 (a) The successful synthesis of benzoxazine can be basically confirmed.

[0041] Example 2

[0042] Preparation of polybenzoxazine monomer in Example 1: Take a certain amount of benzoxazine monomer, dissolve it in DMF and drip it into a polytetrafluoroethylene mold, then place it in a vacuum drying oven at 140°C to remove the solvent, and then place it in a blast drying oven, set the temperature gradient to 160°C (1h), 180°C (1h), 200°C (2h), 220°C (2h), 250°C (v1 h) for curing, and after cooling, obtain polybenzoxazine thermosetting resin, the reaction formula is shown in formula (II). The DSC and TGA curves of the obtained resin are shown in Figure 2 .

[0043] Degradation images and degradation rates are as follows Figure 4 , 5.

[0044]

[0045] Figure 2 The DSC (a) and TGA (b) curves of a polybenzoxazine of Example 2 are shown in FIG. From the DSC curve (a), it can be seen that the curing starting temperature (T onset ) and peak temperature (T peak ) are 194 and 248°C, respectively, with a thermal enthalpy of 120 J / g, and the absorption peak at 200°C is very small, indicating that the benzoxazine monomer has been completely cured at 200°C. During the temperature rise process from 220 to 250°C, there is a small exothermic peak in DSC, indicating that the exchange reaction between the silyl ether bond and the hydroxyl group will release heat. The heat resistance of polybenzoxazine can be seen from the TGA curve (b). When the benzoxazine resin of the present invention is cured at 200°C, its 5% mass loss temperature is 331°C, and the residual carbon rate (Yc) at 800°C is close to 56.9%, while when it is cured at 250°C, its 5% mass loss temperature is 363°C, and the residual carbon rate (Yc) at 800°C is close to 58.5%. These values ​​are greater than most similar resins. The higher the corresponding weight loss temperature and residual carbon rate, the better its heat resistance.

[0046] Figure 4 This is a degradation diagram of a benzoxazine polymer under alkaline conditions at different time periods in Example 2. It can be seen from the figure that as time goes by, the block of resin gradually becomes smaller, and the color of the solution also deepens, and the block of resin completely disappears after 9 hours.

[0047] Figure 5 Figure 2 is a graph showing the degradation rate of a benzoxazine polymer in Example 2 under alkaline (0.1-1M NaOH) conditions at different temperatures (Figure a is 50°C, Figure b is room temperature). As can be seen from Figure (a), when degraded at 50°C, it can be completely degraded in 9 hours, while at room temperature (12-17°C) ( Figure 5-b) takes 3 days to degrade. This indicates that the benzoxazine resin can be degraded even when temperature is applied, and has good degradability under alkaline conditions.

[0048] Figure 6 The infrared spectrum (a) of a benzoxazine polymer degraded under alkaline conditions and its degradation mechanism diagram (b) are shown in Example 2. It can be seen from the infrared spectrum that after the resin is degraded, the -1 The characteristic peak intensity of Si-O-PH at 3569cm -1 New peaks appeared at 780 and 888 cm, which are characteristic peaks of hydroxyl (-OH). -1 There are new peaks at , and these two characteristic peaks are the vibration absorption peaks of Si-OH structure, indicating that Si-O-PH structure can be broken into oligomers containing silanol and phenol (Si-OH, PH-OH) under alkaline conditions. The degradation mechanism of the resin is shown in the figure Figure 6 As shown in b and c.

[0049] Example 3

[0050] Preparation of the benzoxazine film in Example 1: A certain amount of benzoxazine monomer was dissolved in chloroform, and then added dropwise to the film mold, and then placed in a 45°C blast oven for 12 hours to remove the solvent, and then heated to cure, with a temperature gradient of 140°C (1 hour), 160°C (1 hour), 180°C (1 hour), 200°C (2 hours), 220°C (2 hours), and 250°C (1 hour) for curing, and after cooling, a polybenzoxazine thermosetting resin film was obtained. The film and its water contact angle are shown in FIG. Figure 3 .

[0051] Figure 3 A film prepared by a benzoxazine of Example 3 (a) and its water contact angle test (b). As can be seen from the figure, the prepared film can be bent to a certain extent, indicating that the film prepared by the benzoxazine has a certain toughness, indicating that the benzoxazine has certain advantages in preparing films. The test result of its water contact angle is 103°, which means that the film has a certain hydrophobicity.

[0052] It can be seen from the above specific embodiments that the present invention is simple in process. The above embodiments only describe the basic principles, main features and advantages of the present invention. The present invention is not limited by the above embodiments, and the present invention will be further developed without departing from the scope and innovation of the present invention. These developments should be within the scope of the claims.

Claims

1. A norbornene-silyl ether-containing benzoxazine monomer, characterized in that: The structure contains norbornene and silyl ether bonds, and its structural formula is: Where -R is any of the following structures: Wherein, -R1 is any one of the following structures:

2. The method for preparing a norbornene-silyl ether-containing benzoxazine monomer according to claim 1, characterized in that: The specific steps are: A phenol source containing nadic anhydride, an amine source containing a silicon ether bond, polyformaldehyde, and a desiccant are mixed, an organic solvent is added, and then the temperature is raised to 110-120° C. and the reaction is carried out for 6-8 hours; after the reaction is completed, the product is filtered and recrystallized, the solvent is removed by rotary evaporation, and the solid is collected and dried to obtain the final product; The reaction formula is as follows:

3. The method for preparing a norbornene-silyl ether-containing benzoxazine monomer according to claim 1, characterized in that: The molar ratio of the phenol of the nadic anhydride, the amine containing a silicon ether bond, the polyformaldehyde and the desiccant is 1:1:2:0.5-1.

4. The method for preparing a norbornene-silyl ether-containing benzoxazine monomer according to claim 1, characterized in that: The organic solvent is at least one of chloroform and xylene.

5. The method for preparing a norbornene-silyl ether-containing benzoxazine monomer according to claim 1, characterized in that: The desiccant is anhydrous sodium sulfate or calcium oxide.

6. The method for preparing a norbornene-silyl ether-containing benzoxazine monomer according to claim 1, characterized in that: The usage ratio of the phenol of the nadic anhydride to the organic solvent is 1 mol:2L.

7. The method for preparing a norbornene-silyl ether-containing benzoxazine monomer according to claim 1, characterized in that: The recrystallization method is to place the mixture in a refrigerator for 10-12 hours.

8. Use of a norbornene-silyl ether-containing benzoxazine monomer according to claim 1 in the preparation of high temperature resistant materials, high strength materials and recycled carbon fibers.

9. A norbornene-silyl ether-containing polybenzoxazine thermosetting resin, prepared using the norbornene-silyl ether-containing benzoxazine monomer according to claim 1, characterized in that: The specific steps are as follows: removing the solvent from the norbornene-silyl ether type benzoxazine monomer in a vacuum drying oven, then placing it in a forced air drying oven, setting the temperature gradient to 160°C for 1h, 180°C for 1h, 200°C for 2h, 220°C for 2h, and 250°C for 1h for curing, and obtaining the polybenzoxazine thermosetting resin after cooling.

10. A norbornene-silyl ether-containing polybenzoxazine thermosetting resin film, prepared using the norbornene-silyl ether-containing benzoxazine monomer according to claim 1, characterized in that: The specific steps are as follows: dissolving a norbornene-silyl ether-type benzoxazine monomer in chloroform, adding the mixture dropwise into a film mold, placing the mixture in a 45°C forced air oven for 12 hours to remove the solvent, and then heating and curing the mixture. The temperature gradient is set at 140°C for 1 hour, 160°C for 1 hour, 180°C for 1 hour, 200°C for 2 hours, 220°C for 2 hours, and 250°C for 1 hour for curing. After cooling, a polybenzoxazine thermosetting resin film is obtained.

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