JPH0122849B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing an epoxy resin curing agent. More specifically, unreacted amines in a reaction product obtained by reacting phenols, formaldehyde, and amines with an amount of unreacted phenols of 5% or less are reacted with acrylonitrile, and the amount of unreacted phenols is reacted with acrylonitrile. is 5% or less, the amount of unreacted amines is 35% or less, and the viscosity is
8000 cps. (25° C.) or less, the product is suitable as a curing agent for epoxy resins. Reaction products of phenols, aldehydes, and aliphatic polyamines are already known and have been put to practical use in a wide range of applications as epoxy resin curing agents for low- and room-temperature curing or wet surface curing. . However, when the content of unreacted phenols in this curing agent exceeds 5%,
This substance is subject to restrictions such as the Poisonous and Deleterious Substances Control Law, and is subject to restrictions such as specified chemical substances or hazardous substances that must be labeled with their names, etc., and if the amount of unreacted amine is large, there is a high risk of causing skin irritation to workers. In recent years, there has been an increasing demand for an epoxy resin curing agent that is a reaction product of phenols, aldehydes, and amines, has a small amount of unreacted phenols in the product, and has a low viscosity. Furthermore, a curing agent with a small amount of unreacted amines is desired, and a synthesis method thereof is eagerly awaited, but conventionally known synthesis methods have a small amount of unreacted phenols and unreacted amines, and It is difficult to obtain reaction products with low viscosity. Namely, known methods for producing reaction products of phenols, aldehydes, and amines include (1) a method in which phenols and aldehydes are reacted in advance, and then amines are added; (2) amines and (3) a method in which phenols and amines are mixed together, and then aldehydes are added and reacted;
(4) There are four methods in which phenols, aldehydes and amines are reacted simultaneously. Among these methods, method (3) above is particularly recommended, but all of the documents teach that aldehydes should be added at a temperature of 40° C. or lower. 40℃ if the amount of aldehydes added is small.
It is possible to synthesize a curing agent at the following temperatures, but when the amount of aldehydes added increases, a large amount of white products are produced due to the reaction between aldehydes and amines, which do not dissolve in the reaction mixture, and the reaction mixture This results in the inconvenience of making stirring and mixing impossible. It is clear that when the amount of aldehydes added is small, the content of unreacted phenols and unreacted amines in the resulting reaction product increases, and the performance desired as a curing agent is lacking. As a method to improve the drawbacks of the above method and obtain a reaction product with a low content of unreacted phenols, the method described in (1) above, in which phenols and aldehydes are reacted in advance, can be considered. It is difficult to avoid obtaining a highly viscous reaction product, and in particular, when the amount of aldehydes added increases, the reaction product becomes even more viscous, making it difficult to use it in practice without using a large amount of diluent. It is. However, if the amount of diluent added is large, it will adversely affect the physical properties and chemical resistance of the cured epoxy resin, making it impractical. In the method (2) above, in which phenols are added after reacting amines and aldehydes in advance, if the amount of aldehydes added is large, the viscosity of the reaction mixture becomes high, and stirring becomes difficult. There is also a risk that the manufacturing operation itself may become impossible. Furthermore, in either method, increasing the amount of amines added is effective in reducing the viscosity of the product, but if there is a large amount of unreacted amines in the resulting reaction product, that is, in the curing agent. Not only does this increase the risk of skin irritation for workers, but during the curing process of the epoxy resin, it absorbs carbon dioxide gas in the air and turns white, resulting in poor appearance of the cured epoxy resin. There are many disadvantages such as causing delamination between layers. The present inventors have conducted intensive studies to solve the disadvantages of each of the above-mentioned methods, reacted phenols, formaldehyde, and amines simultaneously under predetermined reaction conditions, and further reacted the resulting reaction products with By reacting acrylonitrile, it is possible to obtain a reaction product that has a small amount of unreacted phenols and unreacted amines remaining in the reaction product, has a low viscosity, and is optimal as an epoxy resin curing agent. As a result, we have arrived at the present invention. That is, in the present invention, phenols and amines are mixed and kept at 70 to 100°C, formaldehyde is added to this mixture and reacted with stirring at a temperature of 70 to 100°C, and then the reaction mixture is heated to 100°C.
Epoxy resin with low content of unreacted phenols and unreacted amines and low viscosity, which is produced by heating to ~180°C to remove reaction product water, and then adding acrylonitrile to the reaction product. This is a method for producing a curing agent. Thus, the amount of unreacted phenols is 5% or less, the amount of unreacted amines (meaning free amines with unsubstituted hydrogen atoms) is 35% or less, and the amine value is usually 350-600 (mgKOH). /g) and the viscosity is
A practically suitable curing agent for epoxy resin having a curing temperature of 8000 cps or less, usually 8000 to 2000 cps at 25°C, can be obtained. In the method of the present invention, the ternary raw materials of phenols, amines, and formaldehyde are simultaneously reacted under the limited conditions described above, and the amines are reacted at a rate of 1 to 1 to 1 mole of the phenols.
The amount of formaldehyde used is in the range of 2.5 moles, and formaldehyde is used in an amount of 1.1 to 2.0 moles per mole of phenols. Here, if formaldehyde is less than 1.1 mole per mole of phenols, there will be a large amount of unreacted phenols in the curing agent, and if it is in excess of more than 2 moles, the viscosity will increase. Further, if the amount of amines is less than 1 mole per mole of phenol, the viscosity will be high, and if it is in excess of 2.5 moles, the amount of unreacted amines will increase. The larger the amount of amines added, the smaller the amount of unreacted phenols in the curing agent and the lower the viscosity. This is undesirable because it not only causes a poor appearance of the cured epoxy resin, but also causes defects such as delamination in the case of multiple coatings. Formaldehyde is added in a temperature range of 70 to 100°C, but if the temperature of the reaction system is below 70°C, the white product resulting from the reaction between amines and formaldehyde will dissolve slowly, which will interfere with stirring.
Undesirable. Although the time for adding formaldehyde is not particularly limited, it is not practical if it becomes too long. Tertiary amines may be added to the above reaction system as desired. The amount of acrylonitrile added to the reaction product obtained by removing the reaction product water is selected in the range of 0.2 to 1.5 mol per 1 mol of phenols.
The temperature of the reaction with acrylonitrile is not particularly limited, and a temperature of 100°C or lower may be employed. Addition of acrylonitrile is effective in eliminating free amines, but it is also effective in extending pot life as a curing agent, significantly improving workability. If the amount added is less than 0.2 mol, the above-mentioned addition effect will not be observed, and if it exceeds 1.5 mol, the curing time will become longer.
This is not preferable because it causes a decrease in water resistance, moisture resistance, etc. of the cured product. Phenols used in the method of the present invention include phenols; ortho-, meta- or para-cresol, n- or iso-butylphenol, octylphenol, nonylphenol,
Alkylphenols represented by xylenol; allylphenols represented by phenylphenol, tolylphenol, xylylphenol, etc.; aralkylphenols represented by benzylphenol, styrenated phenols, etc.; It can be used alone or in combination. Optionally 4,4'-
Polyhydric phenol compounds typified by dihydroxydiphenylmethane and 2,2-bis(4'-hydroxyphenyl)propane can also be used. As the formaldehyde, an aqueous formaldehyde solution is usually used, but a formaldehyde-donating compound such as paraformaldehyde or trioxane may be used if desired. Examples of amines include chain aliphatic polyamines, such as ethylenediamine, diethylenetriamine,
Triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, tetramethylenediamine, hexamethylenediamine; fatty aromatic polyamines, such as metaxylenediamine, paraxylenediamine; cycloaliphatic polyamines, such as 1,3- or 1,4- It refers to polyamines exemplified by bisaminomethylcyclohexane and N-aminoethylpiperazine, and these can be used alone or in combination. The reaction product obtained by the method of the present invention as described above has a content of unreacted phenols of 5% or less and a content of unreacted amines of 35% or less, Amine value is usually 350-600
The viscosity is in the range of mgKOH/g at 25°C.
8000cps. or less, making it an extremely suitable product as an epoxy resin curing agent. The epoxy resin that can be used with the curing agent obtained by the method of the present invention may be any known epoxy resin such as bisphenol type epoxy resin, novolac type epoxy resin, cyclohexene oxide type epoxy resin, etc., and is not particularly limited. It's not something that should be done. When using a solid epoxy resin, it is preferable to dissolve it in a suitable solvent known per se and use it in liquid form. The amount of curing agent to be used is determined by calculating the active hydrogen equivalent relative to the epoxy equivalent, and of course is appropriately selected in consideration of the performance required of the cured epoxy resin. When blending the curing agent obtained by the method of the present invention into an epoxy resin, a suitable diluent may be used as desired, such as benzyl alcohol, dixylylmethane, dixylylethane, low viscosity xylene formaldehyde resin (Mitsubishi Gas Chemical Co., Ltd.). (product name: Nicanol-LL); monoepoxy compounds (e.g., butyl glycidyl ether, phenyl glycidyl ether, products from Yuka Ciel Epoxy Co., Ltd., product name: "Cardilla-E", etc.); pigments; fillers and It is also possible to add various additives that are normally incorporated into epoxy resins. The epoxy resin blended with the curing agent of the present invention has 0
It cures quickly even at low temperatures of ℃ to 5℃ or on wet surfaces, and the resulting cured product has excellent surface gloss and smoothness, and has excellent properties such as chemical resistance, moisture resistance, and corrosion resistance. Furthermore, it has extremely good adhesive properties and can be applied to a wide range of applications. The present invention will be specifically explained below using Examples and Comparative Examples. Example 1 108 g (1 mol) of orthocresol and 204 g (1.5 mol) of metaxylene diamine were charged into a reaction vessel equipped with a stirrer, and the mixture was heated to 90° C. while stirring under a nitrogen gas stream. After raising the temperature, 97g (1.2 mol) of 37% formalin was added to the mixture over 1 hour, and after reacting at a temperature of 90℃ to 95℃ for 2 hours, the resulting water was gradually raised to 180℃. Distilled away. Next, 27 g (0.5 mol) of acrylonitrile was added to the obtained reaction product to give 1
After stirring for an hour, 35 g of benzyl alcohol was added to obtain a clear pale yellow product ("Curing Agent A"). The properties of the obtained "curing agent A" are shown in Table-1. Example 2 Orthocresol 108g (1 mol) and 1,3
-bisaminomethylcyclohexane 241g (1.7
The mixture was heated to 90° C. under a nitrogen gas flow, and 105 g (1.3 mol) of 37% formalin was added thereto over 1 hour. Next, perform the same operation as in Example 1,
32 g (0.6 mol) of acrylonitrile was added to the reaction product from which water was removed at 180° C. or lower and stirred for 1 hour to obtain a product (“curing agent B”). Its physical properties are shown in Table-1. Example 3 Orthocresol 108g (1 mol), metaxylene diamine 272g (2.0 mol), 37% formalin 122g (1.5 mol) and acrylonitrile
A product ("hardening agent C") was obtained by carrying out the same operation as in Example 1, except that 37 g (0.7 mol) was used and the addition time of formalin was changed to 1.5 hours. Its physical properties are shown in Table-1. Example 4 Orthocresol 108 (1 mol), metaxylene diamine 340 g (2.5 mol), 37% formalin
146g (1.8mol) and acrylonitrile 53
g (1 mol), formalin addition time was 2
A product ("curing agent D") was obtained by performing the same operation as in Example 1 except for changing the time. Characteristics are shown in Table-1
Shown below. Comparative Example 1 94 g (1 mol) of phenol and 272 g (2 mol) of metaxylene diamine were charged into the reaction vessel of Example 1, and the mixture was heated at a temperature of 40°C or less.
122 g (1.5 mol) of 37% formalin was added over 1.5 hours, but a large amount of white product was formed, resulting in poor stirring and subsequent reaction was discontinued. Comparative Example 2 94 g (1 mol) of phenol, 54 g (0.67 mol) of 37% formalin, and 2.5 g of meta-xylene diamine as a catalyst were placed in the reaction vessel of Example 1.
The mixture was heated to 90°C to 95°C under a nitrogen gas stream and reacted for 1 hour. Next, 133.5 g of meta-xylene diamine (1 mole including catalyst addition) was added to approx.
After adding over 15 minutes and reacting at 90°C to 95°C for 2 hours, the water produced was removed while gradually raising the temperature of the reaction product to 180°C, and the product (“curing agent E”) ) was obtained. The characteristic values of "Curing Agent E" are also listed in Table-1. Comparative Example 3 94 g (1 mol) of phenol and 272 g (2 mol) of metaxylene diamine were charged into the reaction vessel of Example 1, and the mixture was heated to 90°C under a nitrogen gas stream, and 97 g (1.2 mol) of 37% formalin was added. ) was added over 1 hour. Then 2 at a temperature of 90℃-95℃
After reacting for a period of time, the water produced was removed while gradually raising the temperature to 180° C. to obtain a product (“curing agent F”). Its physical properties are also listed in Table-1.

【table】

[Table] As is clear from the results in Table 1, the curing agent obtained by the method of the present invention has a low content of unreacted phenols and unreacted amines, has good curing characteristics, and has good workability. It turns out that it is suitable for practical use.

Claims (1)

[Claims] 1 Mix phenols and amines to 70~
Maintain the temperature at 100°C, add formaldehyde to this mixture and react at a temperature of 70-100°C with stirring,
Thereafter, the reaction mixture is heated to 100 to 180°C to remove the water produced by the reaction, and then acrylonitrile is added to the reaction product, thereby reducing the content of unreacted phenols and unreacted amines. Manufacturing method of epoxy resin curing agent that is viscosity.