JPS6126566B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel epoxy resin composition comprising an epoxy resin mixed with a specific curing agent. More specifically, it relates to an epoxy resin composition that cures very quickly even in the relatively low temperature range of around 100 to 130°C, has a long pot life, and provides a cured product with excellent mechanical and electrical properties when heated. . Traditionally used as a latent curing agent for epoxy resins
_BF3 -amine complexes are known. When used as a one-component curing agent for epoxy resin, the BF ₃ -amine complex has a long posytolife;
It can be cured in a relatively short time of several minutes at high temperatures such as 150°C or higher, making it extremely useful and widely used. However, a drawback of this curing agent is that the curing agent has poor high-temperature properties, particularly poor electrical properties. Furthermore, the curing time of the BF ₃ -amine complex is slow at relatively low temperatures around 100 to 130°C, making it unsuitable as a curing agent for use at temperatures around this range. There are many curing agents such as aromatic amines, aliphatic amines, imidazoles, etc., but all of these have short pot lives and are inconvenient to use, and the cured products have poor properties. many. In this way, the curing agents that have been discovered so far have various drawbacks, and from both a technical and economic point of view, they have a long pot life and cannot be used quickly even in the temperature range of around 100 to 130 degrees Celsius. There is a strong demand in various fields for a curing agent that can be used in curing resins and that can provide excellent properties. However, as a result of various research conducted by the present inventors,
By blending and using a BF ₃ -amine complex and an isocyanate compound as a curing agent in an epoxy resin, the above-mentioned drawbacks can be eliminated and the above-mentioned objectives can be fully achieved. We have discovered a new fact that it is possible to provide an epoxy resin composition that gels in a few minutes by heating to a temperature around 130°C and provides a curing agent with excellent mechanical and electrical properties. The invention was completed. That is, the present invention relates to an epoxy resin composition characterized by blending a BF ₃ -amine complex and an isocyanate compound as a curing agent into an epoxy resin, which has excellent mechanical and electrical properties. Moreover, an epoxy resin composition with excellent workability is provided. The reason why the epoxy resin composition of the present invention provides such a large effect is not yet clear, but the inventors' assumptions will be described below. Several reaction mechanisms have been proposed for the reaction between the BF ₃ -amine complex and epoxy resin. The initiation reaction occurs when the hydrogen atom bonded to nitrogen attacks the oxygen atom of the oxirane ring of the epoxy resin, and then the activated BF ₃ -amine complex acts as a catalyst, causing the epoxy resin to polymerize. The reaction mechanism is currently the most likely. Assuming this, in the curing agent of the present invention, the hydrogen atom bonded to the nitrogen atom in the BF ₃ -amine complex attacks the isocyanate group before attacking the oxygen atom of the oxirane ring of the epoxy resin. It is believed that the activated BF ₃ -amine complex formed thereby acts as a catalyst and causes polymerization of the epoxy resin. As described above, it is thought that the active species are the same when the curing agent of the present invention is used and when the BF ₃ -amine complex is used alone, and therefore, the curing agent of the present invention is different from the case where the BF ₃ -amine complex is used alone. It is believed that it has similar potential benefits, namely a long pot life and rapid hardening upon use. In addition, the hydrogen atom bonded to the nitrogen atom in the BF ₃ -amine complex is
Because it has greater reactivity with isocyanates than with epoxy resins, the curing agent of the present invention is thought to be able to exhibit rapid curing properties that show gelation within a few minutes even at relatively low temperatures around 100 to 130°C. . The improvement in the properties of the curing agent is thought to be due to the presence of isocyanate groups partially reacting with epoxy groups to form oxazolidone rings with excellent mechanical and electrical properties. Examples of epoxy resins that can be used in the present invention include 2,2'-bis(P-hydroxy)propane, 2,2'-bis(4-hydroxy-3,5-dibromphenyl)propane, 1 ，
1,2,2-tetrakis(P-hydroxyphenyl)ethane, 4,4-dihydroxydiphenyl,
Glycidyl ethers of aromatic phenols such as resorcinol, catechol, hydroquinone, and glycidyl ethers such as phenol novolak, cresol novolak, triglycidyl isocyanurate, N of 5,5-dimethylhydantoin,
Examples include N'-diglycidyl derivatives and isoheterocyclic epoxy resins. These can be used alone or in combination. Examples of the isocyanate compound used in the present invention include phenyl isocyanate, benzyl isocyanate, m-tolyl isocyanate, P-tolyl isocyanate, 2-chlorophenyl isocyanate, 1-naphthyl isocyanate, and other functional isocyanate compounds. Also, for example, tolylene diisocyanate, hexamethylene diisocyanate, naphthalene-1,5-diisocyanate, diphenyl ether 4,4'-diisocyanate, biphenyl-4,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, triphenylmethane diisocyanate, isocyanate,
Polyfunctional isocyanate compounds such as 3,3'-4,4' diphenylmethanetetrisocyanate, and dimers and trimers thereof can be used alone or in combination. Furthermore, the BF ₃ -amine complex used in the present invention has the general formula

[Formula] (where R ₁ , R ₂ , and R ₃ represent a hydrogen atom or a monovalent hydrocarbon group. However, at least one of R ₁ to _{R 3} is a hydrogen atom.) , e.g. _BF3 -monomethylamine, _BF3 -monoethylamine, _BF3 -mono-n-
Butylamine, BF ₃ -mono-t-butylamine,
_BF3 -monopentylamine, _BF3 -aniline,
BF ₃ -benzylamine, BF ₃ -dimethylamine,
Examples include BF ₃ -diethylamine, BF ₃ -methylethylamine, BF ₃ -diphenylamine, BF ₃ -phenylethylamine, and the like. These can be used alone or in combination. The blending ratio of the curing agent in the epoxy resin composition of the present invention is 1.1 to 2.4 moles of the isocyanate compound per mole of the BF ₃ -amine complex. This is because if less than 1.1 mol of the isocyanate compound is blended with respect to 1 mol of the BF ₃ -amine complex, sufficient rapid curing properties and improved properties of the cured product cannot be obtained. Furthermore, if more than 2.4 mol of an isocyanate compound is blended, the isocyanate reacts with moisture in the air, resulting in a shortened pot life and reduced potential. Moreover, this is because foaming occurs during curing, resulting in deterioration of properties. A curing agent containing 1.1 to 2.4 mol of an isocyanate compound per 1 mol of BF _{3 -amine} complex is
It is added in an amount of 7 to 12 parts by weight per 100 parts by weight of the epoxy resin. Of course, it is possible to obtain a cured product even at a blending ratio outside this range, but it is not possible to obtain one that is electrically and mechanically satisfactory. That is, if the amount of the curing agent is less than 7 parts by weight, sufficient thermosetting properties cannot be exhibited, and if it exceeds 12 parts by weight, the epoxy resin is relatively reduced, resulting in deterioration of the properties of the cured product. In addition, an increase in the amount of isocyanate compounds may cause foaming due to reaction with moisture or adversely affect pot life. Further, the epoxy resin composition of the present invention may contain an epoxy resin, a BF ₃ -amine complex, and an isocyanate compound as its components, and there is no problem with the method of mixing them. For example, the isocyanate compound may be added after adding the BF ₃ -amine complex to the epoxy resin, or the BF ₃ -amine complex may be added after adding the isocyanate compound to the epoxy resin, or the BF ₃ -amine complex may be added to the epoxy resin. The complex and the isocyanate compound may be mixed and then added to the epoxy resin. Moreover, these substances may be added at the same time. The BF ₃ -amine complex used in the present invention is usually solid at room temperature, and many isocyanate compounds are also solid at room temperature. However, these are all 50
Can be mixed with epoxy resin at temperatures around ~60℃. Of course, depending on the application, it may be used by dispersing it in a liquid epoxy resin as a fine powder, or it may be used in a powder form together with a solid epoxy resin. If necessary, various fillers, diluents, modifiers, pigments, extenders, softeners, etc. may be added to the epoxy resin composition of the present invention. Next, the epoxy resin composition of the present invention will be specifically explained with reference to Examples and Comparative Examples. Examples 1 to 3 (Comparative Examples 1 to 3) 100 parts by weight of diglycidyl ether of 2,2'-bis(P-hydroxy)propane (epoxy equivalent: about 184) (trade name, Epicote 828 manufactured by Ciel Chemical Co., Ltd.) (hereinafter simply referred to as “part”), as a hardening agent.
Two parts of BF ₃ monoethylamine were mixed with varying amounts of diphenylmethane-4,4'-diisocyanate (hereinafter abbreviated as MDI), and 120
The gelation time of the resin heated at ℃, the potlife when the resin is placed in a sealed container and stored at 20℃, and the ratio of gelation time to potlife are calculated as follows:
Shown in the table. To measure the gelation time, put a certain amount (1 g) of the sample into a glass test tube with a diameter of 10 mm.
A glass rod with a diameter of 5 mm was inserted, rotated and heated in an oil bath, and the point at which the torque of the inserted glass rod reached 3.2 g cm was defined as the gel point.
In addition, the pot life was defined as the time required for the viscosity to reach 10 times the initial viscosity.

[Table] The ratio of gel time and pot life in Table 1 can be easily used as a measure of the latent potential of the curing agent. In other words, the larger this value is, the greater the latent potential is, indicating that it is an advantageous curing agent. Looking at Table 1 for the values of this ratio, we find that
Examples 1, 2, and 3 and Comparative Example 1 showed excellent values, and it can be seen from the values that they have the same potential as BF ₃ -monoethylamine shown in Comparative Example 3. Furthermore, it can be seen that Comparative Example 2, in which the molar ratio of MDI to BF ₃ -monoethylamine was 5 or more, had slightly inferior latency. Although Comparative Example 1 has latent effects, the curing time is slower than in Examples 1 to 3, and as will be shown later, the cured product has poor electrical and mechanical properties. Examples 4 to 6 100 parts of diglycidyl ether of 2,2′-bis(P-hydroxy)propane (epoxy equivalent: approximately 184) (trade name, Epicote 828 manufactured by Ciel Chemical Co., Ltd.)
5 parts of MDI and various BF ₃ -amine complexes were mixed and heated at 120°C.
Shown in the table.

[Table] From Table 2, it can be seen that changing the amine salt of the BF ₃ -amine complex does not significantly affect the gelation time. In addition, for Examples 4 to 6, the pot life at 20°C in a sealed state was measured in the same manner as Examples 1 to 3, and in each case it was about 3 days (72 hours), so the ratio of pot life/gelation time was also measured. The values are comparable to Examples 1 to 3. Examples 7 to 9 100 parts of diglycidyl ether of 2,2'-bis(P-hydroxy)propane (epoxy equivalent: approximately 184) (trade name Epicote 828, manufactured by Ciel Chemical Co., Ltd.)
Table ₃ shows the gelation time, pot life at 20℃, and the ratio of gelation time to potlife when 2 parts of BF 3 -monoethylamine were blended and various isocyanate compounds were further blended and heated at 120℃. .

Table 3 shows that even when the isocyanate compound is changed in this example, the pot life/gel time ratio values are similar to those seen in the previous example. Furthermore, it can be seen from this that diisocyanate is the isocyanate compound that gives good results. Example 10 BF ₃ using 100 parts of phenol novolac polyglycidyl ale (trade name: DEN-438 manufactured by Dow Chemical Company) having an epoxy equivalent of 180 as an epoxy resin.
- Two parts of monoethylamine are blended, and tolylene diisocyanate (80% of 2.4-substituted product, 80% of 2.6-substituted product)
When the gelation time of 5 parts of 20%) was measured at 120°C, it was 212 seconds. Further, when the pot life of this product was measured at 20° C. in the same manner as in the above-mentioned Examples, it was 60 hours. The gelation time/pot life ratio was 0.283 (x3600), which indicates that it has fast curing properties and high latent properties. Example 11 N,N'-diglycidyl derivative of 5,5-dimethylhydantoin (epoxy equivalent: approx. 140, trade name: XB- manufactured by Ciba Geigy) as an epoxy resin
2793), 2 parts of BF ₃ -N-methylaniline, and 5 parts of MDI were blended, and the gelation time was measured at 120°C, and it was 190 seconds. Further, when the pot life of this product was measured at 20° C. in the same manner as in the above-mentioned Examples, it was 48 hours. Gel time/pot life ratio is 0.253
(×3600), it can be said that it has fast curing properties and high latent potential. Comparative Example 4 As an epoxy resin, 100 parts of diglycidyl ether of 2,2'-bis(P-hydroxy)propane (epoxy equivalent: approximately 184, trade name Epicote 828 manufactured by Ciel Chemical Co., Ltd.) was added to 2-ethyl-4-methyl. When 5 parts of imidazole was blended and the gelation time was measured at 120°C, it was 180 seconds. Further, when the pot life of this product was measured at 20° C. in the same manner as in the above-mentioned Examples, it was 24 hours. The gelation time/pot life ratio was 0.133 (x3600), and although it was fast curing, it could be said that the latentity was small compared to the case where the BF ₃ -amine complex was used alone and compared to the present invention. Comparative Example 5 As an epoxy resin, 100 parts of diglycidyl ether of 2,2'-bis(P-hydroxy)propane (epoxy equivalent: approximately 184, trade name Epicote 828, manufactured by Ciel Chemical Co., Ltd.) and 8 parts of BF ₃ -monoethylamine were used.
After adding 60 parts of MDI and curing at 120℃,
There was a lot of foaming and a uniform cured product could not be obtained. In this comparative example, the molar ratio of the BF ₃ -amine complex and the isocyanate compound is 1/3.14, which is less than 1/2.4.
This corresponds to the case where the amount of curing agent exceeds 12 parts. Comparative Example 6 As an epoxy resin, BF ₃ -monoethylamine was added to 100 parts of diglycidyl ether of 2,2'-bis(P-hydroxy)propane (epoxy equivalent: approximately 184, trade name Epicote 828, manufactured by Ciel Chemical Co., Ltd.).
0.2 parts and 0.5 parts of MDI were added, and the gelation time was measured at 120°C, but gelation did not occur even after 2 hours. In this comparative example, the molar ratio of the BF ₃ -amine complex to the isocyanate compound is 1/1.136, which is between 1/1.1 and 1/2.4, but corresponds to a case where the amount of curing agent is less than 7 parts. Example 12 As an example of the characteristics of the cured product of the epoxy resin composition of the present invention, the temperature characteristics of tan δ (dielectric loss tangent), which is commonly used as a measure of excellent electrical properties, are shown in the attached drawing. (Measured at 60Hz) The cured products used in the measurements were cured at 100°C for 2 hours, 120°C for 2 hours, and 150°C for 1 hour, respectively. As is clear from the drawing, when BF ₃ -monoethylamine is used, the temperature decreases rapidly at around 100 to 120℃.
Although the tan δ increases and the properties deteriorate, in the case of the epoxy resin composition of the present invention, the tan δ increases even at 160°C.
It exhibits extremely excellent properties with less than 5%.
Furthermore, similarly excellent electrical properties were obtained for the cured products of other Examples. Example 13 Epoxy resin composition of the present invention and Comparative Example 1,
The composition in Comparative Example 4 was cured under the same curing conditions as in Example 12, and the bending strength at room temperature (20° C.) was measured as an example of the mechanical properties and is shown in Table 4. Note that the measurements were conducted based on JIS standard K-6911.

[Table] As explained above, the epoxy resin composition according to the present invention can be used even at relatively low temperatures around 100 to 130°C.
It exhibits extremely fast curing properties, gelling in a few minutes.
Furthermore, it exhibits the same level of potential as the BF ₃ -amine complex. In addition, the epoxy resin composition of the present invention can be said to be an epoch-making product having the advantage that the cured product has excellent mechanical and electrical properties.

[Brief explanation of the drawing]

The figure is a characteristic diagram comparing the tan δ-temperature characteristics of those obtained by curing the compositions of Examples 2 and 3 of the present invention and those obtained by curing with BF ₃ -monoethylamine alone. Note that the measurement was performed at 60Hz.

Claims (1)

[Claims] 1. 100 parts by weight of epoxy resin and general formula (Here, R ₁ , R ₂ , and R ₃ represent a hydrogen atom or a monovalent hydrocarbon group. However, at least one of R ₁ to _{R 3} is a hydrogen atom.) BF ₃ -amine complex represented by /An epoxy resin composition comprising 7 to 12 parts by weight of a curing agent having a molar ratio of 1/1.1 to 1/2.4 of an isocyanate compound.