Curing agent with adjustable reaction activity, high-modulus epoxy resin matrix and preparation method of high-modulus epoxy resin matrix

Abstract

The invention discloses a curing agent with adjustable reaction activity, a high-modulus epoxy resin matrix and a preparation method of the high-modulus epoxy resin matrix. The adjustable curing activity epoxy resin matrix disclosed by the invention has the characteristics of high strength and high modulus, and is a combination of polyfunctionality epoxy resin and a novel activity adjustable aromatic amine curing agent; the novel activity-adjustable aromatic amine curing agent is a compound obtained after amino and an electron-withdrawing group or an electron-donating group replace aromatic ring structures such as a benzene ring, biphenyl, diphenyl and a fused ring, and on the basis that the high modulus and other mechanical properties of the epoxy resin can be guaranteed, the curing activity of the resin can be regulated and controlled within a large range; therefore, the actual requirements of different composite material forming processes are met.

Description

Technical Field

[0001] The invention relates to the technical field of resin-based composite materials, in particular to a curing agent with adjustable reaction activity and a high-modulus epoxy resin matrix and a preparation method thereof. Background Art

[0002] Epoxy resin is the most commonly used resin matrix for resin-based composite materials. It has a wide range of sources and types. The molecular structure and crosslinking density of epoxy resin and curing agent determine the mechanical properties of the resin cured product. Common epoxy resin curing agents include amines, anhydrides, imidazoles, etc. Among them, amine curing agents are widely used because of their cheap raw materials and high performance of the reaction cured products. Amine curing agents can be divided into two categories: aliphatic amines and aromatic amines. Aromatic amines have a benzene ring structure, and the molecular chain rigidity is relatively high, so the obtained cured product has a higher modulus.

[0003] There are many methods for epoxy resin-based composite molding processes, but no matter which process is used, the molding process can be roughly summarized as the resin impregnating the reinforcing fibers and undergoing a curing reaction under pressure / temperature conditions to obtain a composite product. Whether the formulation of composite molding process parameters is reasonable determines the molding quality of the composite material. The optimal molding process parameters must be formulated in combination with the molding process characteristics, product size, shape characteristics, resin rheological properties, resin curing properties and other characteristics. The formulation of molding process parameters is closely related to the curing reaction activity of the resin, and the resin gel time that reflects the resin reaction activity determines the process window time of the resin. The resin matrix must have a certain process window to meet the needs of composite material preparation.

[0004] For a given combination of resin and curing agent, the method for adjusting its reaction activity and process window is usually to add accelerators or inhibitors. This method has two problems. First, the additive is the third phase, which may significantly affect the physical properties of the epoxy cured product. For example, the activity is adjusted, but the strength, modulus and other properties of the cured product are significantly changed. On the other hand, for amine curing agents, most amine curing agents have relatively high reaction activity. The effect of adding inhibitors on adjusting the reaction activity of amine curing agents is not obvious, and it is difficult to meet the actual requirements of the composite material molding process. Summary of the invention

[0005] The present invention provides a curing agent with adjustable reactivity and a high modulus epoxy resin matrix and a preparation method thereof. By combining a multifunctional epoxy resin and a novel adjustable reactivity aromatic amine curing agent, a cured product with a high crosslinking density can be easily obtained. The multifunctional epoxy resin has higher rigidity than traditional resins. The novel adjustable reactivity aromatic amine curing agent is a compound obtained by replacing structures such as a benzene ring with an amino group and an electron-withdrawing group or an electron-donating group. The present invention can achieve regulation of the resin curing activity within a larger range on the basis of ensuring mechanical properties such as high modulus of the epoxy resin, thereby meeting the actual needs of different composite material molding processes.

[0006] In a first aspect, a curing agent with adjustable reactivity is provided, wherein the curing agent with adjustable reactivity comprises a combination of one or more compounds obtained by substituting a main structure with an X1 substituent and an X2 substituent, wherein in any compound, the main structure is any one of a benzene ring structure, a diphenyl structure, a biphenyl structure, a heterocyclic structure and a condensed ring structure, and the X2 substituent is an amino group; when the X1 substituent is an electron-donating group, the curing agent with adjustable reactivity is a promoting curing agent; when the X1 substituent is an electron-withdrawing group, the curing agent with adjustable reactivity is an inhibiting curing agent.

[0007] In conjunction with the first aspect, in certain implementations of the first aspect, the electron donating group includes -OH, -(CH2) n CH3, -O(CH2) n CH3, -(CH2) n At least one of NH2 and -NH2.

[0008] In combination with the first aspect, in certain implementations of the first aspect, the electron withdrawing group includes at least one of Y, -CY3, -NO2, -SO3H, -CONH- and -CN, wherein Y represents a halogen element.

[0009] In combination with the first aspect, in certain implementations of the first aspect, the number of amino groups substituted on the main structure satisfies: 1≤number of amino groups≤3.

[0010] In a second aspect, a high modulus epoxy resin matrix is ​​provided, comprising:

[0011] 100 parts of multifunctional epoxy resin;

[0012] 10 to 50 parts of a curing agent with adjustable reactivity;

[0013] The functionality of multifunctional epoxy resin is ≥3;

[0014] The reactivity-adjustable curing agent is the reactivity-adjustable curing agent as described in any one of the implementations of the first aspect above.

[0015] In conjunction with the second aspect, in certain implementations of the second aspect, the curing agent with adjustable reactivity is a facilitating curing agent, including at least one of 1,3,5-tris(4-aminophenyl)benzene and tris(4-aminophenyl)amine;

[0016] The structural formula of 1,3,5-tri(4-aminophenyl)benzene is as follows:

[0017]

[0018] The structural formula of tris(4-aminophenyl)amine is as follows:

[0019]

[0020] In conjunction with the second aspect, in certain implementations of the second aspect, the reactivity-adjustable curing agent is an inhibited curing agent, including at least one of 4-fluoro-1,2-phenylenediamine, 3,5-diaminotrifluorotoluene, sulfonaniline, 1,5-naphthalenediamine, 1,8-naphthalenediamine, and diaminodiphenylamide;

[0021] The structural formula of 4-fluoro-1,2-phenylenediamine is as follows:

[0022]

[0023] The structural formula of 3,5-diaminotrifluorotoluene is as follows:

[0024]

[0025] The structural formula of sulfoaniline is as follows:

[0026]

[0027] The structural formula of 1,5-naphthalenediamine is as follows:

[0028]

[0029] The structural formula of 1,8-naphthalenediamine is as follows:

[0030]

[0031] The structural formula of diaminodiphenylamide is as follows:

[0032]

[0033] In conjunction with the second aspect, in certain implementations of the second aspect, the molar ratio of the amino active hydrogen in the curing agent with adjustable reactivity to the epoxy group in the multifunctional epoxy resin is 0.8 to 1.2.

[0034] In a third aspect, a method for preparing a high modulus epoxy resin matrix as described in any one of the implementations of the second aspect is provided, comprising:

[0035] Mixing a multifunctional epoxy resin matrix and a curing agent with adjustable reactivity uniformly at room temperature;

[0036] homogenizing the obtained mixture to obtain a resin composition;

[0037] The resin composition is poured and degassed to obtain a high-modulus epoxy resin matrix.

[0038] In conjunction with the third aspect, in certain implementations of the third aspect, the preparation method satisfies at least one of the following:

[0039] The mixture is homogenized, including: placing the mixture in a dispersing homogenizer, and stirring at a high speed of 300 to 18,000 rpm for 5 to 30 minutes;

[0040] The resin composition is poured and degassed, comprising: pouring the resin composition into a mold preheated to 40-100° C., and placing the mold in a vacuum oven for degassed for 5-20 minutes.

[0041] Compared with the prior art, the solution provided by the present invention includes at least the following beneficial technical effects:

[0042] (1) The present invention provides a curing agent with adjustable reactivity and a high modulus epoxy resin matrix, which is a combination of a multifunctional epoxy resin and an aromatic amine curing agent, ensuring that the resin modulus can be maintained at a relatively high level (above 4.5 GPa). When used as a matrix, it is beneficial to improve the properties of the composite material such as compression and shearing which are closely related to the resin;

[0043] (2) The present invention provides a curing agent with adjustable reactivity and a high modulus epoxy resin matrix, and further provides specific compounds and combinations thereof used as a promoting curing agent and an inhibiting curing agent. Compared with the aromatic amine main structure, the promoting curing agent can shorten the gel time of the resin matrix to less than half of the original gel time, and the inhibiting curing agent can extend the gel time of the resin matrix to more than twice the original gel time;

[0044] (3) The present invention provides a curing agent with adjustable reactivity and a high modulus epoxy resin matrix. The present invention is directed to a widely used aromatic amine curing agent. From the perspective of molecular structure design, the reactivity of the amino group is regulated by means of the electrophilic and nucleophilic effects of the substituents, thereby achieving the regulation of the curing reaction activity. The type, quantity, and position of the substituents in the novel aromatic amine curing agent are designed by molecular structure to change the reactivity of the aromatic amine, thereby achieving the purpose of controllable reactivity. The reactivity of the curing agent is regulated within a large range from the perspective of molecular structure, while minimizing the change in the performance of the original curing agent. When the epoxy resin matrix provided by the present invention is used as a composite material matrix, the curing activity can be regulated by molecular design according to the requirements of different molding processes, thereby adjusting the resin matrix performance to meet the requirements.

[0045] (4) The present invention provides a curing agent with adjustable reactivity and a high modulus epoxy resin matrix. The curing activity is changed by designing the molecular structure of the substituent. While adjusting the curing activity, there is no need to add a third phase reaction inhibitor or accelerator. The curing activity has little effect on the viscosity of the resin matrix and the mechanical properties of its cured product, and both mechanical properties and process performance can be taken into account. DETAILED DESCRIPTION

[0046] The present invention is further described in detail below in conjunction with specific embodiments.

[0047] The invention provides a curing agent with adjustable reactivity. By designing the molecular structure of the X1 substituent, a promoting aromatic amine curing agent or an inhibiting aromatic amine curing agent can be obtained.

[0048] The reactivity-adjustable curing agent includes a combination of one or more compounds obtained by substituting the main structure with the X1 substituent and the X2 substituent, in any compound, the main structure is any one of a benzene ring structure, a diphenyl structure, a biphenyl structure, a heterocyclic structure and a condensed ring structure, and the X2 substituent is an amino group; when the X1 substituent is an electron-donating group, the reactivity-adjustable curing agent is a promoting curing agent; when the X1 substituent is an electron-withdrawing group, the reactivity-adjustable curing agent is an inhibiting curing agent.

[0049] The structural formula of the reactivity adjustable curing agent is as follows:

[0050]

[0051] The curing agent with adjustable reactivity can be a single compound or a mixture of multiple single compounds; the main structure of the single compound can be a benzene ring structure or a diphenyl structure, biphenyl structure, heterocyclic structure and condensed ring structure obtained by replacing R1 in formula (1); the aromatic ring main structure carries one or more amino groups, and the number of -NH2 in the amino group is n, 1≤n≤3; in addition to the amino group, there are other substituents X1.

[0052] The curing agent with adjustable reactivity can be used as a low-activity inhibitory curing agent according to the different substituents X1. Compared with the curing agent without X1 substitution, the room temperature gel time is extended to more than 2 times; or used as a high-activity accelerator curing agent, that is, compared with the curing agent without X1 substitution, the room temperature gel time is shortened to less than half of the original.

[0053] In some embodiments, the number of amino groups substituted on the main structure satisfies: 1≤number of amino groups≤3.

[0054] In some embodiments, the electron donating group includes -OH, -(CH2) n CH3, -O(CH2) n CH3, -(CH2) n At least one of NH2 and -NH2.

[0055] In some embodiments, the electron withdrawing group includes at least one of Y, -CY3, -NO2, -SO3H, -CONH-, and -CN, wherein Y represents a halogen element.

[0056] The present invention also provides a high modulus epoxy resin matrix, comprising the following components in parts by mass:

[0057] 100 parts of multifunctional epoxy resin;

[0058] 10 to 50 parts of a curing agent with adjustable reactivity;

[0059] The functionality of multifunctional epoxy resin is ≥3;

[0060] After curing the multifunctional epoxy resin and the curing agent with adjustable reactivity, the modulus of the high modulus epoxy resin matrix is ​​≥4.5GPa, and it is suitable for one or more of the molding processes such as composite prepreg / autoclave, molding, liquid molding, etc. For the aromatic amine main structure, after using the X1-substituted accelerating curing agent, the gel time of the resin matrix can be shortened to less than half of the original time compared with the X1 unsubstituted curing agent; after using the X1-substituted inhibiting curing agent, the gel time of the resin matrix can be extended to more than 2 times compared with the X1 unsubstituted curing agent.

[0061] In some embodiments, the curing agent with adjustable reactivity is an accelerating curing agent, including at least one of 1,3,5-tris(4-aminophenyl)benzene and tris(4-aminophenyl)amine.

[0062] The structural formula of 1,3,5-tri(4-aminophenyl)benzene is as follows:

[0063]

[0064] The structural formula of tris(4-aminophenyl)amine is as follows:

[0065]

[0066] In some embodiments, the curing agent with adjustable reactivity is an inhibited curing agent, including at least one of 4-fluoro-1,2-phenylenediamine, 3,5-diaminotrifluorotoluene, sulfonaniline, 1,5-naphthalenediamine, 1,8-naphthalenediamine, and diaminodiphenylamide.

[0067] The structural formula of 4-fluoro-1,2-phenylenediamine is as follows:

[0068]

[0069] The structural formula of 3,5-diaminotrifluorotoluene is as follows:

[0070]

[0071] The structural formula of sulfoaniline is as follows:

[0072]

[0073] The structural formula of 1,5-naphthalenediamine is as follows:

[0074]

[0075] The structural formula of 1,8-naphthalenediamine is as follows:

[0076]

[0077] The structural formula of diaminodiphenylamide is as follows:

[0078]

[0079] In some embodiments, the molar ratio of the amino active hydrogen in the curing agent with adjustable reactivity to the epoxy group in the multifunctional epoxy resin is 0.8-1.2.

[0080] The present invention also provides a method for preparing a high modulus epoxy resin matrix, comprising the following steps:

[0081] (1) uniformly mixing a multifunctional epoxy resin matrix and a curing agent with adjustable reactivity at room temperature;

[0082] (2) homogenizing the mixture obtained in step (1) to obtain a resin composition;

[0083] (3) The resin composition is poured and degassed to obtain a high modulus epoxy resin matrix.

[0084] In some embodiments, in step (2), the specific method for homogenizing the mixture obtained in step (1) is to place the mixture obtained in step (1) in a dispersion homogenizer and stir it at a high speed of 300 to 18,000 rpm for 5 to 30 minutes.

[0085] In some embodiments, in step (3), the resin composition is poured into a mold preheated to 40-100° C. and placed in a vacuum oven for degassing for 5-20 minutes.

[0086] The solution provided by the present invention can meet the requirements of composite material molding processes for high modulus resin process windows. On the basis of ensuring the mechanical properties of epoxy resin such as high modulus, the curing activity of the resin can be regulated within a larger range, thereby meeting the actual requirements of different composite material molding processes.

[0087] On the one hand, by designing a multifunctional epoxy resin structure and a new multifunctional active adjustable aromatic amine curing agent, the crosslinking density and molecular chain rigidity of the resin cured product are improved, thereby achieving high modulus performance of the epoxy resin; on the other hand, based on the principle of the reaction between amino groups and epoxy groups, electron-withdrawing or electron-donating groups are designed to be introduced into the curing agent molecule to change the electron cloud density of the amino group of the curing agent, thereby inhibiting or enhancing the reaction activity of the amino group, adjusting the curing activity of the resin system, and thus adjusting the processability of the resin composition; the molecular structure design does not need to introduce a third phase, and while adjusting the processability, it tries to avoid affecting other properties of the resin curing.

[0088] Embodiment 1:

[0089] The epoxy resin is 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, namely TDE-85 epoxy resin; the curing agent is a mixture of 2,4-diaminotoluene and 1,3,5-tri(4-aminophenyl)benzene. 100 parts (by mass) of epoxy resin, 10 parts (by mass) of 2,4-diaminotoluene and 30 parts (by mass) of 1,3,5-tri(4-aminophenyl)benzene curing agent are mixed and placed in a high-speed dispersing homogenizer for high-speed homogenization for 5 minutes. A portion of the sample is taken for measuring the gel time at room temperature; the other portion of the sample is poured into a mold preheated to 60°C and placed in a vacuum oven. After degassing for 5 minutes, it can be used for the preparation of resin castings or for the preparation of composite materials after cooling.

[0090] Embodiment 2:

[0091] The epoxy resin is TDE-85 epoxy resin, and the curing agent is 4-fluoro-1,2-phenylenediamine. 100 parts (by mass) of epoxy resin and 27 parts (by mass) of curing agent are mixed and placed in a high-speed dispersing homogenizer for high-speed homogenization for 30 minutes. A portion of the sample is taken to measure the gel time at room temperature; the other portion of the sample is poured into a mold preheated to 60°C and placed in a vacuum oven. After degassing for 10 minutes, it can be used for the preparation of resin castings or for the preparation of composite materials after cooling.

[0092] Embodiment 3:

[0093] The epoxy resin is TDE-85 epoxy resin, and the curing agent is 3,5-diaminotrifluorotoluene. 100 parts (by mass) of epoxy resin and 38 parts (by mass) of curing agent are mixed and placed in a high-speed dispersing homogenizer for high-speed homogenization for 10 minutes. A portion of the sample is taken to measure the gel time at room temperature; the other portion of the sample is poured into a mold preheated to 80°C and placed in a vacuum oven. After degassing for 10 minutes, it can be used for the preparation of resin castings or for the preparation of composite materials after cooling.

[0094] Embodiment 4:

[0095] The epoxy resin is TDE-85 epoxy resin, and the curing agent is a mixture of diaminodiphenylamide and 1,8-naphthalenediamine. 100 parts of epoxy resin, 25 parts (by mass) of diaminodiphenylamide, and 12 parts (by mass) of 1,8-naphthalenediamine curing agent are mixed and placed in a high-speed dispersing homogenizer for high-speed homogenization for 20 minutes. A portion of the sample is taken to measure the gel time at room temperature; the other portion of the sample is poured into a mold preheated to 80°C and placed in a vacuum oven. After degassing for 10 minutes, it can be used for the preparation of resin castings or for the preparation of composite materials after cooling.

[0096] Embodiment 5:

[0097] The epoxy resin is TDE-85 epoxy resin, and the curing agent is sulfonaniline. 100 parts of epoxy resin and 26 parts (by mass) of sulfonaniline curing agent are mixed and placed in a high-speed dispersing homogenizer for high-speed homogenization for 30 minutes. A part of the sample is taken to measure the gel time at room temperature; the other part of the sample is poured into a mold preheated to 100° C. and placed in a vacuum oven. After degassing for 10 minutes, it can be used for the preparation of resin castings or for the preparation of composite materials after cooling.

[0098] Comparative Example 1

[0099] By searching the literature, a common high modulus epoxy resin composition was selected for comparison, namely TDE-85 epoxy resin and m-phenylenediamine curing agent. Compared with Comparative Example 1, the resin modulus of Examples 1-5 of the present invention is kept relatively high, above 4.5 GPa, while maintaining a similar main molecular structure, and the mechanical properties are not significantly sacrificed while adjusting the curing activity of the resin matrix.

[0100] Compared with the interphenylenediamine curing agent in comparative example 1, on this commonly used aromatic amine main structure, embodiment 1 is designed to introduce methyl and amino electron-donating groups, and mix them, improve the amino activity, and use it as a promoting curing agent; embodiment 2 and 3 are designed to introduce halogen electron-withdrawing groups, reduce the amino activity, and use it as an inhibitory curing agent; embodiment 4 is designed to introduce condensed ring structure and diphenylamide electron-withdrawing groups, and mix them, reduce the amino activity, and use it as an inhibitory curing agent; embodiment 5 is designed to introduce sulfonyl electron-withdrawing groups, reduce the amino activity, and use it as an inhibitory curing agent. Compared with the 22h gel time measured in comparative example 1, embodiments 1-5 of the present invention achieve several times longer or shorter gel time by designing different substituents on the curing agent molecule, and the gel time at room temperature is shortened to 4.5h at the minimum and extended to 168h (one week) at the maximum, achieving a significant adjustment of the reaction activity of the resin composition. See Table 1 for details.

[0101] Table 1 Performance comparison of each embodiment and comparative example

[0102]

[0103] Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A curing agent with adjustable reactivity, characterized in that: The reactivity-adjustable curing agent comprises a combination of one or more compounds obtained by substituting a main structure with an X1 substituent and an X2 substituent, wherein in any compound, the main structure is any one of a benzene ring structure, a diphenyl structure, a biphenyl structure, a heterocyclic structure and a condensed ring structure, and the X2 substituent is an amino group; when the X1 substituent is an electron-donating group, the reactivity-adjustable curing agent is a promoting curing agent; when the X1 substituent is an electron-withdrawing group, the reactivity-adjustable curing agent is an inhibiting curing agent.

2. The reactivity adjustable curing agent according to claim 1, characterized in that: Electron donating groups include -OH, -(CH2) n CH3, -O(CH2) n CH3, -(CH2) n At least one of NH2 and -NH2.

3. The reactivity adjustable curing agent according to claim 1, characterized in that: The electron withdrawing group includes at least one of Y, -CY3, -NO2, -SO3H, -CONH- and -CN, wherein Y represents a halogen element.

4. The reactivity adjustable curing agent according to claim 1, characterized in that: The number of amino groups substituted in the main structure satisfies: 1≤number of amino groups≤3.

5. A high modulus epoxy resin matrix, characterized in that: include: 100 parts of multifunctional epoxy resin; 10 to 50 parts of a curing agent with adjustable reactivity; The functionality of multifunctional epoxy resin is ≥3; The reactivity-adjustable curing agent is the reactivity-adjustable curing agent as claimed in any one of claims 1 to 4.

6. The high modulus epoxy resin matrix according to claim 5, characterized in that: The curing agent with adjustable reactivity is a promoting curing agent, including at least one of 1,3,5-tri(4-aminophenyl)benzene and tri(4-aminophenyl)amine; The structural formula of 1,3,5-tri(4-aminophenyl)benzene is as follows: The structural formula of tris(4-aminophenyl)amine is as follows:

7. The high modulus epoxy resin matrix according to claim 5, characterized in that: The curing agent with adjustable reactivity is an inhibited curing agent, including at least one of 4-fluoro-1,2-phenylenediamine, 3,5-diaminotrifluorotoluene, sulfonaniline, 1,5-naphthalenediamine, 1,8-naphthalenediamine, and diaminodiphenylamide; The structural formula of 4-fluoro-1,2-phenylenediamine is as follows: The structural formula of 3,5-diaminotrifluorotoluene is as follows: The structural formula of sulfoaniline is as follows: The structural formula of 1,5-naphthalenediamine is as follows: The structural formula of 1,8-naphthalenediamine is as follows: The structural formula of diaminodiphenylamide is as follows:

8. The high modulus epoxy resin matrix according to claim 5, characterized in that: The molar ratio of the amino active hydrogen in the curing agent with adjustable reaction activity to the epoxy group in the multifunctional epoxy resin is 0.8-1.

2.

9. A method for preparing a high modulus epoxy resin matrix as claimed in any one of claims 5 to 8, characterized in that: include: Mixing a multifunctional epoxy resin matrix and a curing agent with adjustable reactivity uniformly at room temperature; homogenizing the obtained mixture to obtain a resin composition; The resin composition is poured and degassed to obtain a high-modulus epoxy resin matrix.

10. The preparation method according to claim 9, characterized in that: The preparation method satisfies at least one of the following: The mixture is homogenized, including: placing the mixture in a dispersing homogenizer, and stirring at a high speed of 300 to 18,000 rpm for 5 to 30 minutes; The resin composition is poured and degassed, comprising: pouring the resin composition into a mold preheated to 40-100° C., and placing the mold in a vacuum oven for degassed for 5-20 minutes.

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