JPH0160164B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to latent curing agents for epoxy resins. More specifically, the present invention relates to a latent curing agent for epoxy resins that has quick curing properties at low temperatures and excellent storage stability at room temperature. Epoxy resins can be cured using acid anhydride curing agents or amine curing agents, etc.
Because it provides cured products with excellent mechanical, electrical, and chemical properties, it is widely used as electrical insulating materials, various molded products, adhesives, and paints. However, epoxy resin compositions containing amine compounds have poor storage stability.
Furthermore, epoxy resin compositions containing acid anhydride curing agents are relatively stable at room temperature, but on the other hand, they have the disadvantage of requiring heating at considerably high temperatures and for long periods of time during curing. Therefore, it is common practice to shorten the curing time by using a curing accelerator such as a tertiary amine, a quaternary ammonium compound, or an organic metal salt. However, although the addition of a curing accelerator improves curability, it has the drawback of significantly impairing storage stability. Therefore, there is a strong demand for so-called latent curing agents, which are stable at relatively low temperatures, do not gel, and quickly harden when heated. Incidentally, several latent curing agents have been proposed so far, and representative compounds include dicyandiamide, dibasic acid dihydrazide, boron trifluoride-amine adducts, guanamines, and melamine. However, although dicyandiamide, dibasic acid dihydrazide, and guanamine have excellent storage stability, they have the disadvantage of requiring long curing at high temperatures of 150°C or higher, and boron trifluoride-amine adducts are hygroscopic. This has a large effect on the properties of the cured product, and until now, there are almost no compounds known that are quick-curing at low temperatures and have excellent storage stability. As a result of intensive studies to develop a latent curing agent that has quick curing properties at low temperatures and excellent storage stability, the present inventor found that (a) a polyfunctional epoxy compound and (b) a tertiary amino acid in the molecule. Addition compounds obtained by reacting with phenols or alcohols having groups or the above
In addition to the two components (a) and (b), we added (c) a polyhydric phenol compound and discovered that the resulting addition compound was an excellent latent curing agent that met the purpose of the present invention. Completed the invention. In particular, the three-component system (a), (b), and (c) generally has better storage stability than the two-component system (a) and (b), and is superior as a latent curing agent. The latent curing agent according to the present invention will be explained in detail below. The polyfunctional epoxy compound (a) used as a raw material for the latent curing agent of the present invention is one having two or more epoxy groups in one molecule, such as bisphenol A, bisphenol F, catechol, resorcinol, etc. polyglycidyl ether obtained by reacting a polyhydric phenol or a polyhydric alcohol such as glycerin or polyethylene glycol with epichlorohydrin, and a polyglycidyl ether obtained by reacting a hydroxycarboxylic acid such as P-oxybenzoic acid or β-oxynaphthoic acid with epichlorohydrin. glycidyl ether esters obtained from polycarboxylic acids such as phthalic acid and terephthalic acid, glycidyl amine compounds obtained from 4,4'-diaminodiphenylmethane and m-aminophenol, and even epoxidized novolacs. and epoxidized polyolefin. (b) The phenol or alcohol having a tertiary amino group in the molecule used to react with these polyfunctional epoxy compounds includes, for example, 2-dimethylaminoethanol, 1-methyl-2-dimethylaminoethanol, 1 -Phenoxymethyl-2-
Dimethylaminoethanol, 2-diethylaminoethanol, 1-butoxymethyl-2-dimethylaminoethanol, 1-(2-hydroxy-3-
phenoxypropyl)-2-methylimidazole,
1-(2-hydroxy-3-phenoxypropyl)
-2-ethyl-4methylimidazole, 1-(2
Hydroxy-3-butoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)- 2-phenylimidazoline, 1-
(2-hydroxy-3-butoxypropyl)-2-
Examples include methylimidazoline, 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminophenol), and the like. Further, as the polyhydric phenol which is the component (c), for example, bisphenol A, bisphenol F, bisphenol S,
hydroquinone, catechol, resorcinol,
Examples include pyrogallol, phenol novolak resin, and the like. When producing an addition compound that is a latent curing agent, the reaction ratio of both components (a) and (b) is 1 equivalent of the OH group of the phenol or alcohol that has a tertiary amino group in the molecule that is component (b). In contrast, the epoxy group of the polyfunctional epoxy compound which is component (a) is 0.8 to 2.5 equivalent, preferably 0.9 to 1.5 equivalent, and the epoxy group is OH
If the amount is less than 0.8 equivalents per equivalent of the group, the softening temperature of the addition compound will be low and pulverization will be difficult, and if it is blended into the epoxy resin as a latent curing agent, sufficient storage stability will not be obtained. In addition, the addition compound in which the epoxy group has 2.5 equivalents per equivalent of OH group partially becomes three-dimensional and becomes an infusible solid, and when this compound is added to the epoxy resin as a latent curing agent, it has fast curing properties. not demonstrated and
There is a drawback that the cured product becomes non-uniform. Furthermore, when producing a latent receptor using three components (a), (b), and (c), it is preferable to use component (c) in an amount equal to or less than the mole of component (b). If the amount of component () exceeds the equimolar amount, there is a drawback that curability decreases. Furthermore (a),
The reaction ratio of the three components (b) and (c) is 0.8 to 0.8 to the epoxy group of component (a) relative to the sum of the number of hydroxyl equivalents of both components (b) and (c).
2.5 times equivalent, especially 0.9 to 1.5 times equivalent is preferable for the same reason as the two-component system (a) and (b). Preferred addition compounds as the latent curing agent of the present invention satisfy the above-mentioned equivalence relationship between OH groups and epoxy groups, and have a softening temperature of about 60 to 180°C. If the softening temperature is less than 60°C, the storage stability at room temperature will be poor, and if it exceeds 180°C, the curing property will be poor. The latent curing agent of the present invention has the above-mentioned OH group,
If the equivalence relationship with the epoxy group is satisfied, (a),
(b) and (c) Each component may be used as a mixture of two or more compounds, and the type of compound of each component,
By changing the mixing ratio, an addition compound having an arbitrary softening temperature can be obtained. These latent curing agents are (a), (b) or (a), (b), (c)
Mix each component thoroughly, gelatinize at room temperature, then complete the reaction at a temperature of about 80 to 150℃, cool,
It can be easily obtained by solidification and pulverization, or addition reaction in a solvent such as tetrahydrofuran, dioxane, methyl ethyl ketone, etc., followed by removal of the solvent and pulverization of the solid. The latent curing agent of the present invention can also be used in combination with known curing agents such as acid anhydrides, dicyandiamide, dibasic acid hydrazides, guanamines, and melamine. In particular, when used in combination with a latent curing agent such as dicyandiamide, curability is greatly improved without reducing storage stability. The epoxy resin applied to the latent curing agent of the present invention has two or more epoxy groups in one molecule. As exemplified as the polyfunctional epoxy compound of component (a), various well-known compounds may be mentioned. The amount of latent curing agent used in the present invention is based on 100 parts by weight of epoxy resin.
The amount is preferably from 0.5 to 40 parts by weight; if it is less than 0.5 parts by weight, sufficient curability will not be exhibited, and if it exceeds 40 parts by weight, it will cause a decline in the performance of the cured product. Next, the present invention will be specifically explained using synthesis examples and examples. The abbreviations of raw materials used in the synthesis examples and examples are as follows. (a) Epoxy resin "Epikoat #828" (Product name: Ciel Chemical Co., Ltd.) Bisphenol A-based epoxy resin Epoxy equivalent 185-190 "Epicoat #834" (Product name: Ciel Chemical Co., Ltd.) Bisphenol A-based epoxy resin Epoxy equivalent 245-260 "Epicote #1001" (product name Ciel Chemical Co., Ltd.) Bisphenol A-based epoxy resin Epoxy equivalent weight 460-480 "Epicron #830" (product name Dainippon Ink Chemical Co., Ltd.) Bisphenol F-based Epoxy resin Epoxy equivalent weight 170-190 (b) Phenol or alcohol having a tertiary amino group in the molecule DMAE 2-dimethylaminoethanol DMP-30 2,4,6-tris(dimethylaminomethyl)phenol DMP-10 2-( dimethylaminomethyl)phenol PG-MZ 1-(2-hydroxy-3-phenoxypropyl)-2-methylimidazole PG-EMZ 1-(2-hydroxy-3-phenoxypropyl)-2-ethyl-
4-Methylimidazole PG-PZL 1-(2-hydroxy-3-phenoxypropyl)-2-phenylimidazoline DEAE Diethylaminoethanol DMAPA 1-methyl-2-dimethylaminoethanol BG-MZ 1-(2-hydroxy-3 -butoxypropyl)-2-methylimidazole (c) Polyhydric phenol compound BA Bisphenol A HQ Hydroquinone PG Pyrogallol synthesis example 1 Synthesis of adduct of DMAE and "Epicote 828" 33.44 g (0.176 equivalent) of "Epicote 828"
Weigh 9.0 g (0.1 equivalent) of DMAE into a beaker,
Saturate well at room temperature and gradually raise the temperature while stirring. The reaction progresses rapidly at around 70℃ and lasts about 1 hour.
Keep at 100℃. After the reaction was completed, the mixture was cooled to room temperature to obtain a pale yellow solid. The softening temperature of this adduct is 100℃
Therefore, it is assumed to be sample No. 1. Synthesis Example 2 Synthesis of adducts of PG-MZ, BA and "Epicote 828" 11.6 g (0.05 equivalents) of PG-MZ, BA5.7 in a 200 ml three-necked flask equipped with a reflux condenser and a stirring device.
g (0.05 eq), methyl ethyl ketone as solvent
50 ml of the mixture was added, and while stirring with heating, 19 g (0.1 equivalent) of "Epicote 828" dissolved in 30 ml of methyl ethyl ketone was added dropwise (30 minutes). After dropping, stir 2
The mixture was heated to reflux for an hour. The solvent methyl ethyl ketone was distilled off under reduced pressure, and upon cooling, a pale yellow solid adduct was obtained. The softening temperature of this adduct is 140℃,
Let's call it sample No. 13. The sample numbers and softening temperatures of the latent curing agent of the present invention synthesized according to Synthesis Example 1 or Synthesis Example 2 are shown below.

【table】

[Table] Example 1 Curability, storage stability, and glass transition temperature were evaluated using the blending ratios shown in Table 1. 1 Method of preparing samples for evaluation Each material was degassed and mixed under reduced pressure using a vacuum stirring and crushing machine (manufactured by Ishikawa Factory Co., Ltd.) at the mixing ratios shown in Table 1.
I spent time. 2 Evaluation of Curability 2-1) Curing initiation temperature (Ti) and peak temperature (Tp) were measured by differential thermal analysis. Sample: Approximately 10 mg Reference material α-alumina Heating rate: 5°C/min 2-2) The sample was placed in a gear oven at a constant temperature and its hardening state was observed. 3 Storage Stability A sample was placed in a constant temperature bath at a predetermined temperature (30°C), and the number of days until fluidity disappeared was measured. 4 Glass transition temperature (Tg) Using a thermomechanical analyzer (TMA, manufactured by Rigaku Denki Co., Ltd.), a sample cured at a specified temperature and time was measured.
Tg was measured by TMA penetration method. Temperature increase rate: 10°C/min Load: 10g Needle diameter: 1mm The results obtained are shown in Table 2. Table 1 Epikote #828 100 parts by weight Latent curing agent of the present invention 20 ZnO 3 TiO ₂ 2

【table】

[Table] As shown in Table 2, the addition compound of the present invention has significantly improved storage stability and excellent latent curing compared to alcohol or phenol alone (comparative example) having a tertiary amino group in the molecule. It will be understood that it is a drug. Example 2 Curability and storage stability were evaluated in a system in which the latent curing agent of the present invention was used in combination with a dibasic acid hydrazide. The formulations are shown in Table 3 and the results are shown in Table 4. Table 3 Epikote #828 100 parts by weight Curing accelerator of the present invention (No. 1 to No. 28) 20 parts by weight Adipic acid hydrazide 8 ZnO 5

【table】

[Table] By comparing Tables 2 and 4, it can be seen that the latent curing agent of the present invention and adipic acid hydrazide exhibit an excellent synergistic effect, and the curing properties are greatly improved. . Example 3 Storage stability and curability were evaluated in a system in which the latent curing agent of the present invention was used in combination with a known latent curing agent. Fifth
The results are shown in the table.

[Table] As shown in Table 5, the known latent curing agent alone does not cure at all (100°C, 1 hour), but when used in combination with the latent curing agent of the present invention, it completely cures at a temperature of 100°C. It can be seen that the curability is significantly improved.

Claims (1)

[Claims] 1. Latency for epoxy resin containing an addition compound obtained by reacting (a) a polyfunctional epoxy compound and (b) a phenol or alcohol having a tertiary amino group in the molecule. Hardening agent. 2 (a) polyfunctional epoxy compound, (b) phenol or alcohol having a tertiary amino group in the molecule and
(c) A latent curing agent for epoxy resin containing an addition compound obtained by reacting with a polyhydric phenol compound.