阅读说明：本技术 一种潜伏性环氧树脂固化剂及其制备方法和应用 (Latent epoxy resin curing agent and preparation method and application thereof ) 是由 周萌 刘岩 方璞 杨在刚 刘赵兴 于 2020-04-30 设计创作，主要内容包括：本发明公开了一种如结构式(I)所述的化合物作为潜伏性环氧树脂固化剂,<Image he="314" wi="700" file="DDA0002474835740000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>所述潜伏性环氧树脂固化剂的结构为酚醛化苯硫醇酯,其制备原料包括苯硫醇、羧基化合物、醛类化合物和芳香族二仲胺,该固化剂在常温下为低粘度液体,与环氧树脂配合后具有较长的适用期,升高温度后苯硫醇酯发生Fries重排从而将活性基团硫醇解离出来,在叔胺基的催化作用下可以迅速与环氧树脂反应,特别适用于对长操作时间有要求的预浸料领域。(The invention discloses a compound as shown in a structural formula (I) as a latent epoxy resin curing agent,)

1. A compound of formula (I),

wherein R is₁Is H₃C-、R₂Is H- (a),H₃C-orR₃Is composed ofR₄Is composed of

2. A process for the preparation of a compound of formula (I) comprising the steps of:

(1) under the protection of inert gas, reacting benzenethiol with a carboxyl compound at 110-170 ℃ for 3-5 h, preferably at 120-150 ℃ for 3.5-4.5 h under the action of a catalyst to obtain benzenethiol ester;

(2) adding aromatic di-secondary amine into the benzenethiol ester obtained in the step (1), fully and uniformly stirring, heating to 70-100 ℃, preferably 80-95 ℃, slowly adding an aldehyde compound, and reacting for 2-5 hours, preferably 3-3.5 hours to obtain the compound.

3. The method of claim 2, wherein in step (1), the molar ratio of benzenethiol to carboxyl compounds selected from one or more of acetic acid, propionic acid and benzoic acid is 1 (0.8-1.3), preferably 1: 0.9-1.1: 1.

4. The method as claimed in claim 2 or 3, wherein in step (2), the molar ratio of the benzenethiol ester to the aromatic secondary amine is 1 (0.8-1.3), and the aromatic secondary amine is selected from one or more of WANA L INK6200 in Wanhua chemical industry, UNI L INK7100 in Air chemical industry, UNI L INK4100 and UNI L INK 4102;

the molar ratio of the benzene thiol ester to the aldehyde compound is 1 (1.9-2.1), and the aldehyde compound is selected from one or more of acetaldehyde, benzaldehyde and 5-40% formaldehyde aqueous solution.

5. Use of a compound according to claim 1 or a compound prepared according to the process of any one of claims 2 to 4 as a latent epoxy resin curing agent.

6. An epoxy resin composition comprising the following components:

the component A comprises: an epoxy resin comprising an optional diluent and an anti-foaming agent;

and B component: comprising a latent epoxy resin curing agent and a catalyst, wherein the latent epoxy resin curing agent is a compound according to claim 1 or a compound prepared according to the process of any one of claims 2 to 4;

the mass ratio of the component A to the component B is (1-6) to 1, preferably (2-3) to 1.

7. The composition of claim 6, wherein the A-side comprises the following components: based on the weight of the A component,

55-80 wt% of epoxy resin, preferably 65-75 wt%;

2-23 wt% of diluent, preferably 7-14 wt%;

1-22 wt% of defoaming agent, preferably 11-21 wt%;

the component B comprises the following components: based on the weight of the component B,

75-95 wt% of latent epoxy resin curing agent;

5-25 wt% of a catalyst.

8. The composition of claim 6 or 7, wherein the epoxy resin is one or more of bisphenol a and bisphenol F epoxy resins; preferably selecting one or more of epoxy resin bisphenol A type and bisphenol F type epoxy resin with an epoxy value of 0.1-0.65 and liquid at room temperature; more preferably bisphenol A epoxy resin with an epoxy value of 0.1-0.65 and liquid at room temperature; and/or

The diluent is selected from one or more of alkyl glycidyl ether with a molecular main chain containing C12-C14, butyl glycidyl ether, benzyl glycidyl ether, butanediol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, 1, 2-cyclohexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, benzyl alcohol, phenethyl alcohol, nonyl phenol, propylene carbonate, trimethylolpropane triacrylate, diisopropanol methyl ether, toluene and xylene; and/or

The defoaming agent is one or more of polyacrylate and modified organic silicon, preferably one or more of BYK066N, BYKA530, BYK6800, BYK141 and BYK 354; and/or

The catalyst is selected from one or more of aluminum trichloride, boron trifluoride, zinc chloride, ferric chloride, titanium tetrachloride, stannic tetrachloride and trifluoromethanesulfonate.

9. The composition according to any one of claims 6 to 8, characterized in that:

preparation of the component A: uniformly mixing the epoxy resin with a diluent and a defoaming agent, and standing;

preparation of the component B: uniformly mixing a latent epoxy resin curing agent and a catalyst, and standing;

when in use, the component A and the component B are mixed uniformly and then are defoamed and cured.

10. The composition of claim 9, wherein in use, the component A and the component B are uniformly mixed and then are kept stand for 15-60 min, preferably 20-45 min; the curing temperature is 80-120 ℃, preferably 90-115 ℃, and the curing time is 3-6 hours, preferably 4-5 hours.

Technical Field

The invention belongs to the field of epoxy resin, and particularly relates to an epoxy resin latent curing agent and application thereof in preparation of an epoxy resin composition.

Background

Epoxy resins are widely used in the field of composite material manufacture and the like due to their excellent properties such as heat resistance, mechanical properties, adhesion, electrical insulation, chemical resistance and the like. Epoxy resin is generally liquid or solid micromolecule or oligomer at room temperature, and forms a three-dimensional cross-linked network structure after reacting with a curing agent, wherein common curing agents comprise amines, anhydrides, thiols, phenols, phenolic compounds, imidazoles and the like.

When the epoxy resin is used for a large composite material system, the resin needs to be capable of flowing fully in a mould before curing, at the moment, a mixed system needs to have a longer pot life and even does not react at normal temperature, and after the temperature of the mould is raised, the curing agent and the epoxy resin are subjected to crosslinking curing, so that the curing agent needs to have lower reactivity, and the currently commonly used low-activity curing agent is mainly a latent curing agent.

The commonly used latent curing agents for the large-scale composite materials mainly comprise ketimine, dicyandiamide, organic acid anhydride and microcapsules, wherein the ketimine is easy to absorb moisture in air to decompose and has higher requirements on construction environment; dicyandiamide is solid at normal temperature and has poor compatibility with epoxy resin; the organic acid anhydride is easy to hydrolyze and has poor moisture resistance, chemical modification is not easy to carry out, and the post-curing temperature is higher; the microcapsule preparation process has strict requirements, the thickness of the microcapsule membrane can bring different degrees of influence on storage, transportation and use, and the industrial application is difficult.

US4335228 proposes that acyl group substituted modified imidazole is adopted, the electron donating ability of imine is weakened due to the strong electron withdrawing effect of acyl group, the energy barrier of imine reacting with epoxy resin is improved, and curing activity is lost at normal temperature, so that the imidazole modified imidazole has good latency, and when the temperature is raised enough to overcome the energy barrier of imine reacting with epoxy resin, the curing activity can be recovered by acyl group substituted imidazole curing agent, but the modified imidazole is generally solid and has poor compatibility with epoxy resin;

CN101885832A proposes that imine compounds of secondary amine prepared by reacting polyamine and carbonyl compounds are used for end capping, the imine structure in a curing agent is hydrolyzed to generate hydrophilic amino in water environment, and the carbonyl compounds generated during the hydrolysis of the latent curing agent exist as a toughening agent in the system, so that the mechanical property of the material is reduced;

CN105837798A proposes that mono-thiocarboxylic acid and epoxy resin are subjected to ring-opening addition to seal mercaptan, the curing agent can automatically convert mercaptan groups in the presence or absence of a catalyst to react with the epoxy resin, but the acetylation reaction dissociation temperature of the mercaptan group dissociation is higher, and the curing agent does not meet the use requirements of a large-scale composite material perfusion process.

In order to solve the problems, a new latent epoxy resin curing agent needs to be found, which has a long pot life after being matched with epoxy resin at normal temperature, can dissociate active groups after the temperature is raised, and can rapidly react with the epoxy resin.

Disclosure of Invention

One of the objects of the present invention is to provide a latent epoxy resin curing agent which is a low viscosity liquid at room temperature and does not contain an active group, and thus does not react with an epoxy resin after being mixed at room temperature, and when the temperature is raised, a thiol group generated by rearrangement reaction of a phenylthiol ester group in the structure of the latent epoxy resin curing agent reacts with the epoxy resin to cure the epoxy resin.

Another object of the present invention is to provide an epoxy resin composition comprising the above latent epoxy curing agent.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

in a first aspect of the present invention, there is provided a latent epoxy resin curing agent, which is a compound represented by formula (I) and has a structure of a phenolated benzenethiol ester:

wherein R is₁Is prepared from,R₂Is H-, orR₃Is composed ofR₄Is composed of

The preferred structure is:

the preparation method of the latent epoxy resin curing agent comprises the following steps:

(1) under the protection of inert gas, reacting benzenethiol and carboxyl compounds in a molar ratio of 1 (0.8-1.3), preferably 1: 0.9-1: 1.1, at 110-170 ℃ for 3-5 h, preferably at 120-150 ℃ for 3.5-4.5 h under the condition of a catalyst to obtain benzenethiol ester;

(2) adding aromatic di-secondary amine into the reaction product of the benzenethiol ester obtained in the step (1), fully and uniformly stirring, heating to 70-100 ℃, preferably 80-95 ℃, dropwise adding an aldehyde compound, and reacting for 2-5 h, preferably 3-3.5 h to obtain the latent epoxy resin curing agent.

In the preparation method of the latent epoxy resin curing agent, the carboxyl compound in the step (1) is selected from one or more of acetic acid, propionic acid and benzoic acid, and acetic acid is further preferred.

The catalyst in the step (1) can be AlCl₃、FeCl₃、KHSO₄And CH₃One or more of COONa, preferably AlCl₃. The amount of the catalyst is 0.1 to 5 wt%, more preferably 0.5 to 3 wt% of the thiophenol.

In the preparation method of the latent epoxy resin curing agent, the molar ratio of the benzene thiol ester to the aromatic secondary amine in the step (2) is 1 (0.8-1.3), preferably 1 (0.9-1.1), the aromatic secondary amine is preferably selected from one or more of WANA L INK6200 in Wanhua chemistry, UNI L INK7100 in air chemical industry, UNI L INK4100 and UNI L INK4102 in Wanhua chemistry, and more preferably WANA L INK6200 in Wanhua chemistry.

In the preparation method of the latent epoxy resin curing agent, the molar ratio of the benzene thiol ester to the aldehyde compound in the step (2) is 1 (1.9-2.1), and preferably 1 (1.95-2.05); the aldehyde compound is one or more selected from acetaldehyde, benzaldehyde and 5-40% formaldehyde water solution, preferably acetaldehyde.

The reaction process for preparing the latent curing agent is further illustrated below by taking thiophenol, acetic acid, acetaldehyde and WANA L INK6200 as raw materials, and the principle is shown as the following formula:

in a second aspect, the present invention relates to an epoxy resin composition comprising the following components:

the component A comprises: comprising an epoxy resin, optionally a diluent and a defoamer;

and B component: comprises the latent epoxy resin curing agent and a catalyst;

the mass ratio of the component A to the component B is preferably (1-6): 1, and more preferably (2-3): 1.

In the epoxy resin composition of the present invention, the component a is preferably prepared from the following raw materials, based on the weight of the component a:

55-80 wt% of epoxy resin; preferably 65 to 75 wt%;

2-23 wt% of a diluent; preferably 7 to 14 wt%;

1-22 wt% of defoaming agent, preferably 11-21 wt%.

The component B is preferably prepared from the following raw materials in parts by weight:

75-95 wt% of latent epoxy resin curing agent;

5-25 wt% of a catalyst.

In one embodiment of the present invention, the epoxy resin composition is prepared by the following steps:

preparation of component A: uniformly mixing the epoxy resin with a diluent and a defoaming agent, and standing;

preparation of the component B: adding the latent curing agent and the catalyst into a reaction kettle, uniformly mixing, and standing;

when in use, the component A and the component B are mixed uniformly and then are defoamed and cured.

In the component a, the epoxy resin is not particularly limited, and may be one or more of bisphenol a type epoxy resin and bisphenol F type epoxy resin; one or more of bisphenol A type epoxy resin and bisphenol F type epoxy resin with the epoxy value of 0.1-0.65 and liquid at room temperature are preferably selected; more preferably bisphenol A epoxy resin with an epoxy value of 0.1-0.65 and liquid at room temperature; including but not limited to one or more of E-44, E-51, E-54, and the like;

the diluent is not particularly limited and may be one or more of a reactive diluent and a non-reactive diluent, and preferred diluents include, but are not limited to, one or more of alkyl glycidyl ether having a molecular main chain of C12 to C14, butyl glycidyl ether, benzyl glycidyl ether, butanediol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, 1, 2-cyclohexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, benzyl alcohol, phenethyl alcohol, nonylphenol, propylene carbonate, trimethylolpropane triacrylate, diisopropanol methyl ether, toluene, xylene, and the like;

the defoaming agent can be one or more of polyacrylate and modified silicone, and is preferably one or two or more of BYK066N, BYKA530, BYK6800, BYK141 and BYK 354.

In the component B, the catalyst is selected from one or more of aluminum trichloride, boron trifluoride, zinc chloride, ferric chloride, titanium tetrachloride, stannic tetrachloride and trifluoromethanesulfonate.

In some specific embodiments of the preparation method of the epoxy resin composition, when the epoxy resin composition is used, the component A and the component B are uniformly mixed and then stand for 15-60 min, preferably 20-45 min; the curing temperature is usually 80-120 ℃, preferably 90-115 ℃, and the curing time is 3-6 hours, preferably 4-5 hours.

In the invention, the compound shown in the formula (I) is used as a latent curing agent, is low-viscosity liquid at normal temperature, has a long pot life after being matched with epoxy resin, and can react with the epoxy resin quickly under the catalysis of tertiary amino after the temperature is raised and Fries rearrangement occurs on phenylthiol ester, so that active group mercaptan can be dissociated;

the action principle is as follows:

the epoxy resin composition can be applied to building enclosures, acid storage tanks, acid-proof pumps, wind power blades, chemical pipelines, reaction tanks, containers, automobile shells, yachts, minesweeping boats, submarine components, buoys, yachts, electric poles, motor retaining rings, radar covers, floating bridges and the like.

The invention has the beneficial effects that:

1. the latent curing agent provided by the invention is a thiol ester group-terminated low-viscosity liquid at normal temperature, and has good compatibility with epoxy resin.

2. The latent curing agent does not contain active groups, has a longer working life when being matched with epoxy resin, and is particularly suitable for the use requirement of prepreg.

3. The latent curing agent can dissociate the active group mercaptan after the temperature is raised, and can quickly react with epoxy resin under the catalytic action of tertiary amine.

Drawings

FIG. 1 is an infrared spectrum of an epoxy resin curing agent of example 1.

Detailed Description