A method for preparing an epoxy resin curing agent

Abstract

The application belongs to the technical field of chemical industry, and discloses a method for preparing an epoxy resin curing agent, which comprises the following steps: in the first step, phenyldimethylamine, an inhibitor and a catalyst are added into a reaction kettle in proportion, wherein the molar ratio of the phenyldimethylamine to the inhibitor is 99:2.8-3.5, and the molar ratio of the phenyldimethylamine to the active component of the catalyst is 99:1-1.35; in the second step, hydrogen is introduced into the reaction kettle, and the pressure in the reaction kettle is controlled in the range of 5-6 MPa, the temperature is controlled in the range of 80-85 DEG C, the stirring rate is controlled in the range of 400-500 r / min, and the reaction time is controlled in the range of 4-6 h, so that a reaction liquid is obtained; and in the third step, the reaction liquid is subjected to rectification treatment, and the fraction in the range of 240-245 DEG C is separated, so that the epoxy resin curing agent is obtained. The application solves the problems of low raw material concentration affecting the reaction rate and the problem of continuously generating side reactions in the process of recovering the solvent caused by using the solvent in the phenyldimethylamine hydrogenation reaction. The application also solves the problem of over-hydrogenation in the phenyldimethylamine hydrogenation reaction.

Description

TECHNICAL FIELD

[0001] The present invention belongs to the field of chemical technology. More specifically, the present invention relates to a method for preparing an epoxy resin curing agent. BACKGROUND

[0002] Cyclohexanedimethylamine, also known as dimethylaminomethylcyclohexane, can be divided into 1,3-cyclohexanedimethylamine (1,3-BAC) and 1,4-cyclohexanedimethylamine (1,4-BAC) according to the position of the substituent. Cyclohexanedimethylamine has no unsaturated benzene ring structure in the molecule, and as a fatty amine curing agent, it has low toxicity, fast curing and good compatibility, and can be used as a curing agent for epoxy resin.

[0003] Cyclohexanedimethylamine is usually prepared by hydrogenation of isophthalonitrile or m-xylylenediamine. In an ideal state, the hydrogenation reaction of phthalonitrile includes benzene ring hydrogenation and nitrile group hydrogenation. In the hydrogenation reaction of m-xylylenediamine, benzene ring hydrogenation is included. However, due to the multiple hydrogenation active sites of the reactants, the main hydrogenation reaction is often accompanied by side reactions such as demethylation or deamination, resulting in deep hydrogenation and reducing the yield and selectivity of the target product. The performance of the target product as a curing agent is affected due to the increase in impurities contained in the target product.

[0004] Chinese patent application CN102690203 A uses a high-pressure autoclave batch hydrogenation process with liquid ammonia as the solvent, at a substrate mass concentration of 10%, a reaction temperature of 130°C, and a reaction pressure of 10 MPa, to obtain a 1,3-cyclohexanedimethylamine molar yield of 97.8%.

[0005] Chinese patent application CN102688766 A uses a fixed-bed continuous hydrogenation process with liquid ammonia as the solvent, at a substrate mass concentration of 20%, a reaction temperature of 130°C, and a reaction pressure of 10 MPa, to obtain a 1,3-cyclohexanedimethylamine molar selectivity of up to 97.4%.

[0006] In the above technical solutions, a large amount of liquid ammonia is used as the reaction solvent. In the process of removing the solvent, side reactions such as deamination, polymerization, and hydrolysis occur in the material, reducing the yield and increasing the impurity content in the target product.

[0007] The weather resistance and temperature resistance of epoxy resin coating film are greatly influenced by the type of curing agent. If the weather resistance and temperature resistance are insufficient, it will lead to problems such as powdering, cracking, discoloration, decreased protection, and high-temperature failure of the epoxy resin coating film under wet heat.

[0008] Although cyclohexane dimethylamine has many advantages as an epoxy resin curing agent, it still has some disadvantages, such as insufficient heat resistance, the glass transition temperature of the cured product is usually lower than 150 DEG C, easy to soften and deform at high temperature, limited weather resistance, the cured film is easy to be degraded by ultraviolet light, and easy to be pulverized and yellowed after long-term outdoor exposure. These defects restrict the application of epoxy resin in high-end composite materials and extreme environments, and the weather resistance and temperature discoloration resistance of epoxy resin need to be improved by improving the curing agent.

[0009] Therefore, there is an urgent need to provide a method for preparing an epoxy resin curing agent, which can maintain good yield and selectivity of the target product without using a solvent. SUMMARY

[0010] In order to at least solve one or more technical problems mentioned above, the present application provides a method for preparing an epoxy resin curing agent, comprising: a first step, adding phenyldimethylamine, an inhibitor and a catalyst into a reaction kettle in proportion, wherein the molar ratio of phenyldimethylamine to the inhibitor is 99:2.8-3.5, the inhibitor is selected from any one of sodium hydroxide, potassium hydroxide and liquid ammonia, the molar ratio of phenyldimethylamine to the active component of the catalyst is 99:1-1.35, the active component of the catalyst is selected from any one of ruthenium, nickel and cobalt, and the carrier of the catalyst is selected from titanium dioxide or activated carbon; a second step, introducing hydrogen into the reaction kettle, controlling the pressure range of the reaction kettle to be 5-6 MPa, the temperature range to be 80-85 DEG C, the stirring rate to be 400-500 r / min, and the reaction time to be 4-6 h to obtain a reaction liquid; and a third step, rectifying the reaction liquid to separate the fraction at 240-245 DEG C to obtain the epoxy resin curing agent.

[0011] According to an embodiment of the present application, the phenyldimethylamine comprises m-phenyldimethylamine and / or p-phenyldimethylamine.

[0012] According to an embodiment of the present application, the inhibitor is sodium hydroxide.

[0013] According to an embodiment of the present application, the catalyst is a ruthenium / carbon catalyst.

[0014] According to an embodiment of the present application, the molar ratio of phenyldimethylamine to the inhibitor is 99:3; and the molar ratio of phenyldimethylamine to the active component of the catalyst is 99:1.

[0015] According to an embodiment of the present application, the molar ratio of phenyldimethylamine to the inhibitor is 99:3; and the molar ratio of phenyldimethylamine to the active component of the catalyst is 99:1.2.

[0016] According to an embodiment of the present application, in the second step, the pressure in the reaction kettle is 5 MPa, the temperature is 80 DEG C, the stirring rate is 500 r / min, and the reaction time is 6 h.

[0017] According to one embodiment of the present application, in the second step, the pressure in the reactor is 5 MPa, the temperature is 85℃, the stirring rate is 450 r / min, and the reaction time is 4 h.

[0018] According to one embodiment of the present application, in the second step, the pressure in the reactor is 6 MPa, the temperature is 85℃, the stirring rate is 400 r / min, and the reaction time is 4 h.

[0019] According to one embodiment of the present application, in the second step, the pressure in the reactor is 5 MPa, the temperature is 80℃, the stirring rate is 400 r / min, and the reaction time is 4 h.

[0020] According to another aspect of the present application, there is provided an epoxy resin curing agent prepared by the above method, and its use in the curing process of epoxy resin.

[0021] By the method for preparing an epoxy resin curing agent as provided above, the dependence of the hydrogenation reaction of methylene diamine on solvent is eliminated, on the one hand, the step of removing solvent and the side reactions caused by the removal of solvent are reduced, on the other hand, the concentration of reactants is increased, and the reaction rate is improved. By means of controlling the proportion of each component and the stirring rate, the dispersion effect of the solvent is replaced, and the effect of controlling the contact probability of methylene diamine, hydrogen and catalyst is achieved. By matching the proportion of each component, the stirring rate and the heat dissipation rate, the over-hydrogenation phenomenon caused by local overheating is reduced. By matching the pressure and the stirring rate, the strong adsorption of the reaction product on the catalyst is avoided, and the active center of the catalyst is occupied to affect the reaction rate. By setting the amount of inhibitor, the over-hydrogenation phenomenon is inhibited. By controlling the pressure in the reactor to control the amount of hydrogen dissolved in the liquid phase, the control of the hydrogenation reaction rate is achieved. By matching the reaction rate with the stirring rate, the product is prevented from accumulating in the active center of the catalyst. In summary, the present application solves the problem of the influence of low raw material concentration on the reaction rate caused by the use of solvent, and the problem of continued side reactions in the process of recovering solvent. The present application also solves the problem of over-hydrogenation in the hydrogenation reaction of methylene diamine.

[0022] According to another aspect of the present application, there is provided an epoxy resin curing agent comprising the following components in terms of weight percentage:

[0023] 99.0%~99.7% of the compound represented by formula (I); 0.0%~0.3% of the compound represented by formula (II); 0.1%~0.3% of the compound represented by formula (III); 0.0%~0.3% of the compound represented by formula (IV); and 0.0%~0.5% of the compound represented by formula (V);

[0024] (I);

[0025] (II);

[0026] (III);

[0027] (IV);

[0028] (V);

[0029] wherein,

[0030] the compound of formula (IV) is a compound of formula (I); R2 is any one of a compound of formula (I) or a compound of formula (III) or hydrogen; the compound of formula (V) is any one of a compound of formula (I), a compound of formula (III), R4 is any one of a compound of formula (I), a compound of formula (III) or hydrogen.

[0031] According to an embodiment of the present application, the compound of formula (I) comprises at least one of 1,3-cyclohexanedimethylamine, 1,4-cyclohexanedimethylamine.

[0032] According to an embodiment of the present application, the compound of formula (II) comprises at least one of 1,3-phenyldimethylamine, 1,4-phenyldimethylamine.

[0033] According to an embodiment of the present application, the compound of formula (III) comprises at least one of 3-methylbenzylamine, 4-methylbenzylamine.

[0034] According to an embodiment of the present application, the compound of formula (III) is 0.3% by weight.

[0035] According to an embodiment of the present application, the compound of formula (II) is less than 0.1% by weight.

[0036] According to an embodiment of the present application, the epoxy resin curing agent comprises the following components by weight percentage: 99.6% of the compound of formula (I); 0.0% of the compound of formula (II); 0.3% of the compound of formula (III); 0.0% of the compound of formula (IV); 0.1% of the compound of formula (V).

[0037] According to an embodiment of the present application, the epoxy resin curing agent comprises the following components by weight percentage: 99.4% of the compound of formula (I); 0.1% of the compound of formula (II); 0.2% of the compound of formula (III); 0.1% of the compound of formula (IV); 0.2% of the compound of formula (V).

[0038] According to one embodiment of the present application, the epoxy resin curing agent comprises the following components by weight percentage: 99.5% of the compound shown in formula (I); 0.1% of the compound shown in formula (II); 0.3% of the compound shown in formula (III); 0% of the compound shown in formula (IV); and 0.1% of the compound shown in formula (V).

[0039] According to one embodiment of the present application, the epoxy resin curing agent comprises the following components by weight percentage: 99.2% of the compound shown in formula (I); 0.1% of the compound shown in formula (II); 0.1% of the compound shown in formula (III); 0.3% of the compound shown in formula (IV); and 0.3% of the compound shown in formula (V).

[0040] The epoxy resin curing agent of the present application limits the maximum content of the benzylmethylamine, and weakens the reducing effect of the benzylmethylamine on the curing performance of the epoxy resin curing agent. The epoxy resin curing agent contains 0.1% to 0.3% of the methylbenzylamine, which can generate salt by neutralization reaction with acidic substances, and can also generate stable addition products by ring-opening reaction with epoxy groups, so as to effectively promote the ring-opening polymerization reaction of the epoxy groups, and improve the weather resistance and temperature discoloration resistance of the epoxy resin. BRIEF DESCRIPTION OF DRAWINGS

[0041] The above and other objects, features and advantages of the exemplary embodiments of the present application will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0042] Figure 1 A schematic diagram of the steps of the method for preparing the epoxy resin curing agent is shown. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0044] It should be understood that the terms "comprise" and "include" used in the specification and claims of the present application indicate the presence of the described features, integers, steps, operations, elements, and / or components, but do not exclude one or more other features, integers, steps, operations, elements, components, and / or sets thereof.

[0045] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this specification and claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0046] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0047] Figure 1 A schematic diagram of the steps in preparing an epoxy resin curing agent is shown.

[0048] like Figure 1 As shown, a method for preparing an epoxy resin curing agent includes: a first step S1, adding phenylenediamine, an inhibitor, and a catalyst to a reaction vessel in a specific ratio, wherein the molar ratio of phenylenediamine to the inhibitor is 99:2.8~3.5, the inhibitor is selected from any one of sodium hydroxide, potassium hydroxide, and liquid ammonia, the molar ratio of phenylenediamine to the active component of the catalyst is 99:1~1.35, the active component of the catalyst is selected from any one of ruthenium, nickel, and cobalt, and the catalyst support is selected from titanium dioxide or activated carbon; a second step S2, introducing hydrogen gas into the reaction vessel, controlling the pressure range of the reaction vessel to be 5~6 MPa, the temperature range to be 80~85 °C, the stirring rate to be 400~500 r / min, and the reaction time to be 4~6 h, to obtain a reaction solution; a third step S3, distilling the reaction solution to separate the fraction in the 240~245 °C range, to obtain the epoxy resin curing agent.

[0049] The rate of hydrogenation of phenylenediamine to cyclohexanedimethylamine is affected by the feed concentration, catalyst performance and selectivity, reaction temperature, and hydrogen concentration. Specifically, phenylenediamine binds to the adsorption sites of the catalyst and undergoes hydrogenation upon contact with hydrogen; that is, the probability of contact between phenylenediamine and hydrogen at the catalyst adsorption sites affects the hydrogenation efficiency. After the phenylenediamine hydrogenation reaction is complete, if the target product cyclohexanedimethylamine continues to bind to the catalyst adsorption sites, it may continue to hydrogenate, forming an over-hydrogenated product, resulting in excessive impurities in the cyclohexanedimethylamine. In other words, the residence time of cyclohexanedimethylamine at the catalyst adsorption sites affects the degree of over-hydrogenation of cyclohexanedimethylamine. Furthermore, the addition of inhibitors can also reduce over-hydrogenation.

[0050] In this invention, phenylenediamine includes m-phenylenediamine and / or p-phenylenediamine.

[0051] The present application excludes the use of solvent, specifically, since the melting point of p-xylylamine is 60-63°C, the melting point of m-xylylamine is 13°C, and the melting point of cyclohexane dimethylamine is -9°C, the reaction conditions in the reaction kettle are controlled so that the raw materials and products are in liquid state, and no solvent is needed for dispersion. However, in order to achieve the contact probability of the raw materials to meet the requirements of the reaction rate, the material is homogenized by stirring. When the stirring rate is too high, the catalyst will be pulverized, which will seriously affect the service life of the catalyst. When the stirring rate is too low, the mass transfer between the reactants and the catalyst is poor, the dispersion of the reactants is not good, and partial material reaction is not complete or local over-hydrogenation, polymerization and other side reactions occur, which also reduce the service life of the catalyst. Selecting a suitable stirring rate can improve the heat transfer coefficient, which is beneficial to the removal of reaction heat and the extension of the service life of the catalyst.

[0052] In the present application, no solvent is used for dispersion, but high-frequency contact state between the catalyst and the xylylamine is maintained by high-speed stirring, so that the reaction can occur and be controlled. However, after each raw material molecule is reacted, the reaction product combined with the catalyst adsorption site needs to be dissociated. In the present application, the ratio of xylylamine to catalyst active component is matched, and the stirring rate is set at 400-500 r / min. On the one hand, it can ensure that the combination of raw materials and catalyst adsorption sites is sufficient to occur benzene ring hydrogenation reaction, and the reaction product can be dissociated from the catalyst adsorption site in time; on the other hand, the reaction heat of hydrogenation reaction can be released in time due to stirring, avoiding heat accumulation.

[0053] The hydrogen concentration dissolved in the liquid phase in the reaction kettle and the reaction temperature jointly affect the rate of hydrogenation reaction. Under the premise that the ratio of xylylamine to catalyst is given, when the temperature is too high and / or the pressure is too large, the reaction product may accumulate in the adsorption site of the catalyst, leading to over-hydrogenation. When the temperature is too low and / or the pressure is too small, part of the raw materials may be forced to dissociate from the adsorption site of the catalyst before being hydrogenated, affecting the hydrogenation efficiency. In order to control the rate of hydrogenation reaction to match the stirring rate and avoid over-hydrogenation caused by the long residence of the product in the adsorption site of the catalyst, the hydrogen pressure in the reaction kettle is set to 5-6 MPa and the temperature is set to 80-85°C in the present application.

[0054] Preferably, during the hydrogenation reaction, the hydrogen pressure in the reaction kettle is 5 MPa, the temperature is 80°C, the stirring rate is 400-500 r / min, and the reaction time is 6 h. More preferably, the hydrogen pressure in the reaction kettle is 5 MPa, the temperature is 85°C, the stirring rate is 450 r / min, and the reaction time is 4 h.

[0055] In the present application, an inhibitor is added to inhibit the substitution of the amino group in the aminomethyl by hydrogen during the hydrogenation reaction, thereby reducing the phenomenon of over-hydrogenation. The inhibitor is selected from alkaline sodium hydroxide, potassium hydroxide, liquid ammonia, etc.

[0056] Under the control of the above reaction parameters, the catalytic hydrogenation reaction is carried out for 4-6 hours to obtain a reaction liquid, which is an intermediate product containing cyclohexane dimethylamine and contains unreacted raw materials, cyclohexane dimethylamine and over-hydrogenated products. When the catalytic hydrogenation is carried out for more than 6 hours, the content of over-hydrogenated products will obviously increase.

[0057] In order to further purify the cyclohexane dimethylamine, the reaction liquid is subjected to rectification treatment, and a fraction in the range of 240-245°C is separated to obtain a fatty amine type epoxy resin curing agent containing cyclohexane dimethylamine.

[0058] In the present application, the catalyst is a supported catalyst, and the loading rate of the active component is 2%-6%. It can be prepared by using conventional preparation methods in the art, such as precipitation method, impregnation method, ion exchange method, sol-gel method and microemulsion method, etc. The active component of the catalyst is selected from any one of rhodium, nickel and cobalt. Alternatively, the active component of the catalyst is selected from a combination of ruthenium and nickel; or, the active component of the catalyst is selected from a combination of nickel and platinum. The carrier is selected from titanium dioxide or activated carbon, and compared with other carriers, the carrier of the present application can avoid over-hydrogenation phenomenon.

[0059] Preferably, the molar ratio of phenyldimethylamine to inhibitor is 99:3; and the molar ratio of phenyldimethylamine to active component of the catalyst is 99:1. More preferably, the molar ratio of phenyldimethylamine to inhibitor is 99:3; and the molar ratio of phenyldimethylamine to active component of the catalyst is 99:1.2.

[0060] For example, the phenyldimethylamine, the inhibitor and the active component of the catalyst are in a ratio of 240g:2.0-2.5g:1.8-2.4g by weight.

[0061] According to another aspect of the present application, the epoxy resin curing agent prepared by the above method is applied in the epoxy resin curing process.

[0062] The epoxy resin curing agent prepared by the above method contains the following components in percentage by weight:

[0063] 99.0%-99.7% of the compound represented by formula (I); 0.0%-0.3% of the compound represented by formula (II); 0.1%-0.3% of the compound represented by formula (III); 0.0%-0.3% of the compound represented by formula (IV); and 0.0%-0.5% of the compound represented by formula (V);

[0064] (I);

[0065] (II);

[0066] (III);

[0067] (IV);

[0068] (V);

[0069] wherein,

[0070] The compound of formula (IV) is a compound of formula (I); R2 is a compound of formula (I) or a compound of formula (III) or hydrogen; the compound of formula (V) is a compound of formula (I), a compound of formula (III), R4 is a compound of formula (I), a compound of formula (III) or hydrogen.

[0071] The compound of formula II is residual phenylenedimethylamine, the compound of formula III is by-product methylbenzylamine. The compounds of formula IV and formula V are dimer or polymer.

[0072] The residual phenylenedimethylamine, as a low-component impurity, not only changes the molecular structure and cross-linking density of the cured product, thereby reducing the curing effect, but also can be oxidized to form a compound that can be colored, such as -NH- or benzoquinone, thereby significantly reducing the discoloration resistance of the cured coating film, leading to cracking and discoloration of the epoxy resin coating film during use, thereby affecting the service life and appearance effect. Preferably, the content of phenylenedimethylamine is controlled to be less than 0.1%.

[0073] Methylbenzylamine has typical amine chemical properties, and can react with acidic substances to form salts, and can also react with epoxy groups to form stable addition products. This basic property is the core property of methylbenzylamine as an epoxy resin curing catalyst, which can effectively promote the ring-opening polymerization reaction of epoxy groups. It is found in experiments that when the cyclohexane dimethylamine and methylbenzylamine composition contains a small amount of methylbenzylamine, for example, 0.3% by weight, the weather resistance of the epoxy resin coating film can be further improved. It is possible that its special planar achiral structure can effectively avoid the steric hindrance effect of cyclohexane dimethylamine, weaken the influence of the amino group activity of phenylenedimethylamine, thereby reducing the oxidation process, improving the low-temperature curing speed of the product, and making it better adapt to different construction environments.

[0074] wherein, the compound of formula (I) includes at least one of 1,3-cyclohexane dimethylamine and 1,4-cyclohexane dimethylamine. The compound of formula (II) includes at least one of 1,3-phenylenedimethylamine and 1,4-phenylenedimethylamine. The compound of formula (III) includes at least one of 3-methylbenzylamine and 4-methylbenzylamine.

[0075] Preferably, the weight percentage of the compound of formula (III) is 0.3%. When the content of the methylbenzylamine is higher or lower than the value, the weather resistance and temperature discoloration resistance of the epoxy resin coating film are reduced.

[0076] The following examples take p-xylylenediamine as an example, and those skilled in the art should understand that m-xylylenediamine can also be used as a raw material in the following examples.

[0077] Example 1

[0078] Into a 500ml high-pressure reactor, 240g of p-xylylenediamine, 2.0g of sodium hydroxide, and a ruthenium / carbon supported catalyst containing 1.8g of active component were put. The stirring speed was 400r / min, the pressure in the reactor was 5MPa, the temperature in the reactor was 80℃, and the reaction time was 4h to obtain a reaction liquid. The reaction liquid was transferred to a rectification kettle for rectification treatment, and the fraction at 240~245℃ was recovered to obtain a rectification product. The obtained product was subjected to chromatographic test.

[0079] Example 2

[0080] The other conditions were the same as those in Example 1, except that the stirring speed was 500r / min, the pressure in the reactor was 6MPa, the temperature in the reactor was 85℃, and the reaction time was 6h.

[0081] Example 3

[0082] The other conditions were the same as those in Example 1, except that the inhibitor was 2.5g of sodium hydroxide, and the catalyst was a ruthenium / carbon supported catalyst containing 2.4g of active component.

[0083] Example 4

[0084] The other conditions were the same as those in Example 1, except that the inhibitor was 2.5g of sodium hydroxide, and the catalyst was a ruthenium / carbon supported catalyst containing 2.4g of active component. The stirring speed was 500r / min, the pressure in the reactor was 6MPa, the temperature in the reactor was 85℃, and the reaction time was 6h.

[0085] Example 5

[0086] The other conditions were the same as those in Example 1, except that the inhibitor was 2.8g of potassium hydroxide.

[0087] Example 6

[0088] The other conditions were the same as those in Example 1, except that the inhibitor was 0.85g of liquid ammonia.

[0089] Example 7

[0090] The other conditions are the same as in Example 1, except that the catalyst is a nickel / carbon supported catalyst containing 1.04 g of active component.

[0091] Example 8

[0092] The other conditions are the same as in Example 1, except that the catalyst is a cobalt / carbon supported catalyst containing 1.05 g of active component.

[0093] Example 9

[0094] The other conditions are the same as in Example 1, except that the catalyst is a ruthenium / alumina supported catalyst containing 1.8 g of active component.

[0095] Example 10

[0096] The other conditions are the same as in Example 1, except that the catalyst is a ruthenium / titania supported catalyst containing 1.8 g of active component.

[0097] Example 11

[0098] The other conditions are the same as in Example 1, except that the inhibitor is 3.5 g of potassium hydroxide, the catalyst is a ruthenium / carbon supported catalyst containing 2.4 g of active component. The stirring rate is 500 r / min, the pressure in the reaction kettle is 6 MPa, the temperature in the reaction kettle is 85°C, and the reaction time is 6 h.

[0099] Example 12

[0100] The other conditions are the same as in Example 1, except that the inhibitor is 1.06 g of liquid ammonia, the catalyst is a ruthenium / carbon supported catalyst containing 2.4 g of active component. The stirring rate is 500 r / min, the pressure in the reaction kettle is 6 MPa, the temperature in the reaction kettle is 85°C, and the reaction time is 6 h.

[0101] Example 13

[0102] The other conditions are the same as in Example 1, except that the inhibitor is 2.5 g of sodium hydroxide, the catalyst is a nickel / carbon supported catalyst containing 1.39 g of active component. The stirring rate is 500 r / min, the pressure in the reaction kettle is 6 MPa, the temperature in the reaction kettle is 85°C, and the reaction time is 6 h.

[0103] Example 14

[0104] The other conditions are the same as in Example 1, except that the inhibitor is 2.5 g of sodium hydroxide, the catalyst is a cobalt / carbon supported catalyst containing 1.40 g of active component. The stirring rate is 500 r / min, the pressure in the reaction kettle is 6 MPa, the temperature in the reaction kettle is 85°C, and the reaction time is 6 h.

[0105] Example 15

[0106] Other conditions are the same as in Example 1, except that the inhibitor is 2.5 g of sodium hydroxide, and the catalyst is a ruthenium / alumina supported catalyst containing 2.4 g of active component. The stirring rate is 500 r / min, the pressure in the reactor is 6 MPa, the temperature in the reactor is 85°C, and the reaction time is 6 h.

[0107] Example 16

[0108] Other conditions are the same as in Example 1, except that the inhibitor is 2.5 g of sodium hydroxide, and the catalyst is a ruthenium / titania supported catalyst containing 2.4 g of active component. The stirring rate is 500 r / min, the pressure in the reactor is 6 MPa, the temperature in the reactor is 85°C, and the reaction time is 6 h.

[0109] Table 1 shows the components and their contents in the products obtained in Examples 1 to 16.

[0110] Table 1. Product component content table

[0111]

[0112] Among them, polymer 1 and polymer 2 are specific compounds represented by formula (IV).

[0113] Polymer 3 and polymer 4 are specific compounds represented by formula (V).

[0114]

[0115]

[0116]

[0117]

[0118] Table 2 shows the application evaluation of the epoxy resin curing agent.

[0119] Table 2 only takes Examples 1, 6, 12, and 15 as examples for evaluation. Those skilled in the art can know that other examples also have similar or the same effects.

[0120] Coating film sample preparation: A certain amount of epoxy resin E-44, diluent D-691, and epoxy resin curing agent (cyclohexane dimethylamine composition) with a mass ratio are weighed, mixed uniformly, and coated on a 120 mm x 70 mm glass plate. Then, the coated glass plate is cured in an oven at a specified temperature for a certain period of time, taken out, and cooled to room temperature.

[0121] Evaluation method: coating film hardness, weather resistance and heat resistance. Coating film hardness is tested by Shore hardness tester, and the qualified value is not less than 75D; weather resistance is tested by ultraviolet accelerated aging test, and the aging time of △E=1.5 is investigated, which is not less than 1000h in principle; heat resistance test is carried out at 200℃ for 0.5h, and no cracking, edge lifting or discoloration occurs.

[0122] Table 2. Application evaluation table of epoxy resin curing agent

[0123]

[0124] It can be seen that when the content of methylbenzylamine in the product is 0.3%, the weather resistance of the coating film is better than that of the coating film containing 0.1%, and when the content of methylbenzylamine in the product is 0.5%, the weather resistance of the coating film is reduced compared with that of 0.3%. When the content of methylbenzylamine in the product is 0.3%, the weather resistance decreases with the increase of the content of p-xylylamine. Moreover, with the addition of methylbenzylamine, the hardness of the coating film is improved.

[0125] Comparative example

[0126] The same as example 17, using cyclohexane dimethylamine curing agent single component to carry out curing agent performance evaluation repeated test,

[0127] Table 3 shows the test data of using cyclohexane dimethylamine curing agent single component as curing agent.

[0128] Table 3. Curing agent test data table

[0129]

[0130] It can be seen that when the curing agent contains methylbenzylamine, the hardness and weather resistance of the coating film are improved compared with those without methylbenzylamine.

[0131] By the method for preparing the epoxy resin curing agent as provided above, the dependence of the hydrogenation reaction of the benzene dimethylamine on the solvent is eliminated, on the one hand, the step of removing the solvent and the side reactions caused by the removal of the solvent are reduced, on the other hand, the concentration of the reactants is increased, and the reaction rate is improved. By means of controlling the proportion of the components and the stirring rate, the dispersion effect of the solvent is replaced, and the effect of controlling the contact probability of the benzene dimethylamine, hydrogen and catalyst is achieved. By matching the proportion of the components, the stirring rate and the heat dissipation rate, the over-hydrogenation phenomenon caused by local overheating is reduced. By matching the pressure and the stirring rate, the strong adsorption of the reaction product on the catalyst to occupy the active center of the catalyst and affect the reaction rate is avoided. By setting the amount of the inhibitor, the over-hydrogenation phenomenon is inhibited. By controlling the pressure in the reaction kettle to control the amount of hydrogen dissolved in the liquid phase, the control of the hydrogenation reaction rate is achieved. By matching the reaction rate and the stirring rate, the accumulation of the product in the active center of the catalyst is avoided. In summary, the present application solves the problem of the influence of the low concentration of the raw material on the reaction rate caused by the use of the solvent and the problem of the continuous generation of side reactions in the process of recovering the solvent. The present application also solves the problem of over-hydrogenation in the hydrogenation reaction of the benzene dimethylamine.

[0132] The epoxy resin curing agent of the present application limits the maximum content of the benzene dimethylamine, and weakens the reducing effect of the benzene dimethylamine on the curing performance of the epoxy resin curing agent. The epoxy resin curing agent contains 0.1% to 0.3% of the methyl benzene methylamine, which can generate a salt by neutralization reaction with an acidic substance, and can also form a stable addition product by ring-opening reaction with an epoxy group, can effectively promote the ring-opening polymerization reaction of the epoxy group, and improve the weather resistance and temperature discoloration resistance of the epoxy resin.

[0133] Although a number of embodiments of the present application have been shown and described herein, it would be apparent to those skilled in the art that many modifications, changes, and substitutions can be made thereto without departing from the spirit and scope of the present application. It is to be understood that various alternatives to the embodiments of the application described herein can be employed in practicing the present application. It is intended that the following claims define the scope of the application and that methods equivalent to those shown and described herein can be utilized without departing from the spirit and scope of the present application.

Claims

1. A method for preparing an epoxy resin curing agent, characterized in that, include: The first step involves adding phenylenediamine, inhibitors, and catalysts to the reaction vessel in a specific ratio. The molar ratio of the phenylenediamine to the inhibitor is 99:2.8~3.5, and the inhibitor is selected from any one of sodium hydroxide, potassium hydroxide, and liquid ammonia. The molar ratio of the phenylenediamine to the active component of the catalyst is 99:1 to 1.35, the active component of the catalyst is selected from any one of ruthenium, nickel, and cobalt, and the catalyst support is selected from titanium dioxide or activated carbon. The second step involves introducing hydrogen gas into the reactor, controlling the pressure range inside the reactor to be 5-6 MPa, the temperature range to be 80-85℃, the stirring rate to be 400-500 r / min, and the reaction time to be 4-6 h, to obtain the reaction solution. The third step involves distilling the reaction solution to separate the fraction in the 240-245°C range, thereby obtaining the epoxy resin curing agent.

2. The method according to claim 1, characterized in that, The phenylenediamine includes m-phenylenediamine and / or p-phenylenediamine.

3. The method according to claim 1, characterized in that, The inhibitor is sodium hydroxide.

4. The method according to claim 1, characterized in that, The catalyst is a ruthenium / carbon catalyst.

5. The method according to claim 1, characterized in that, The molar ratio of the phenylenediamine to the inhibitor is 99:3; The molar ratio of the phenylenediamine to the active component of the catalyst is 99:

1.

6. The method according to claim 1, characterized in that, The molar ratio of the phenylenediamine to the inhibitor is 99:3; The molar ratio of the phenylenediamine to the active component of the catalyst is 99:1.

2.

7. The method according to claim 1, characterized in that, In the second step, the pressure inside the reactor is 5 MPa, the temperature is 80°C, the stirring rate is 500 r / min, and the reaction time is 6 h.

8. The method according to claim 1, characterized in that, In the second step, the pressure inside the reactor is 5 MPa, the temperature is 85°C, the stirring rate is 450 r / min, and the reaction time is 4 h.

9. The method according to claim 1, characterized in that, In the second step, the pressure inside the reactor is 6 MPa, the temperature is 85°C, the stirring rate is 400 r / min, and the reaction time is 4 h.

10. The method according to claim 1, characterized in that, In the second step, the pressure inside the reactor is 5 MPa, the temperature is 80℃, the stirring rate is 400 r / min, and the reaction time is 4 h.

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