JPH07258384A - Epoxy resin composition - Google Patents

Abstract

PURPOSE:To obtain an epoxy resin used for a powder coating material and excellent in thermoresistant adhesiveness, infiltrability, etc., by using two specified epoxy resins, a curing agent, a specified phenolic resin, a cure accelerator and a specified imidazole compound. CONSTITUTION:This composition comprises a crystalline epoxy resin (A) of the formula I, a bisphenol epoxy resin (B) of the formula II (wherein G is the same as the O-containing group bonded to either benzene ring in the formula I; and n is 10-16), a novolac phenolic resin (C) of the formula III (wherein R1 to R3 are methyl or tert-C4H3), bisphenol A (D), and an imidazole compound (E) of the formula IV (wherein X is H or methyl; and R is methyl, ethyl, C7H15 or C11H23). Component A contributes to the heat resistance and infiltrability of the composition, and component B contributes to the thermal cycling resistance because of its flexibility. It is desirable that component B has an epoxy equivalent of 1500-2500 and a melting point of 120-150 deg.C. The mixing ratio is such that 0.3-0.8 equivalent of the OH groups of components C and D are present per equivalent of the epoxy groups of components A and B, and that component E is present in an amount of 0.2 to 5wt.% based on the resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin composition which is excellent in heat-resistant adhesiveness, cold-heat cycle resistance, impregnation and storage stability.

[0002]

2. Description of the Related Art In recent years, powder compositions, such as powder coatings, are being replaced with solvent-based coatings that have been conventionally used over a wide range as pollution-free, resource-saving and energy-saving coatings.

However, since a general powder coating material has a high viscosity at the time of melting, it has an advantage that a thick film can be finished by one coating operation. Has inferior penetrability, that is, gap filling property, thin film coating property, and the like. Further, in recent years, along with the expansion of applications, there has been a demand for improvement of the above-mentioned drawbacks as well as improvement of heat resistance and adhesiveness, and it is necessary to develop a new material to meet these demands. An epoxy resin composition is generally used as a powder coating material that is often used. As the epoxy resin composition,
For example, an epoxy resin such as a bisphenol A type epoxy resin, a novolac type epoxy resin, an alicyclic type epoxy resin is the main component, and a curing agent such as an acid anhydride or polyamine
It is known that a curing accelerator such as a tertiary amine or imidazole, a filler, and other additives are blended.

[0004]

However, when a general bisphenol A type epoxy resin or the like is used,
If low molecular weight compounds are used with an emphasis on heat resistance, shelf life will decrease, and conversely, if high molecular weight compounds are used, heat resistance and impregnability will tend to decrease, and in fields where higher heat resistance is required. Will have difficulty responding to this.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an epoxy resin composition which is excellent in heat-resistant adhesiveness, impregnating property, preservability and workability.

[0006]

In order to achieve the above objects, the epoxy resin composition of the present invention comprises the following (A) to
It is configured to contain the component (E). (A) A crystalline epoxy resin represented by the following general formula (1).

[Chemical 6] (B) Bisphenol A represented by the following general formula (2)
Type epoxy resin.

[Chemical 7] (C) A novolac-type phenol resin represented by the following general formula (3).

[Chemical 8] (D) Bisphenol A represented by the following general formula (4).

[Chemical 9] (E) An imidazole compound represented by the following general formula (5).

[Chemical 10]

[0007]

The present inventors have conducted a series of studies in order to obtain an epoxy resin composition having excellent heat-resistant adhesiveness, impregnation property, storability and workability. As a result, the epoxy resins represented by the general formulas (1) and (2) are used as the main components, and the general formulas (3) and (4) are used as the curing agent.
When the imidazole compound represented by the general formula (5) is used as each phenol resin represented by
It can suppress the deterioration of adhesiveness due to continuous use in a high temperature atmosphere, obtains excellent impregnating property that can penetrate into details, and significantly decreases the characteristics even after long-term storage under high temperature and high humidity conditions. The inventors have reached the present invention by discovering that characteristics such as small amount can be obtained.

Next, the present invention will be described in detail.

The epoxy resin composition of the present invention comprises two types of specific epoxy resins (components A and B) and two types of specific phenolic resins (components C and D).
It is obtained by using a specific imidazole compound (component E) and is a powder.

One of the above two kinds of specific epoxy resins is an epoxy resin (component A), which is represented by the following general formula (1):
It is a crystalline epoxy resin represented by, and has excellent heat resistance due to its dense cross-linking due to its low molecular structure, and it is solid at room temperature because it is crystalline, and its viscosity rapidly rises above the melting point. Is low and the impregnation property is excellent.

[0011]

[Chemical 11]

Among the above crystalline epoxy resins, the epoxy equivalent is 170 to 210 and the melting point is 90 to 120.
It is preferable to use one having a temperature of ° C.

The remaining epoxy resin (component B) of the above two kinds of specific epoxy resins is represented by the following general formula (2).
A bisphenol A type epoxy resin represented by the following formula. This epoxy resin is classified into a liquid type and a solid type depending on its molecular weight. Bisphenol A used in this invention
A high molecular weight solid type is used as the type epoxy resin. Therefore, it has a characteristic that it has flexibility due to its straight-chain structure and has excellent resistance to cold and heat cycles.

[0014]

[Chemical 12]

Among the above bisphenol A type epoxy resins, the epoxy equivalent is 1500 to 2500,
It is preferable to use one having a melting point of 120 to 150 ° C.

The reason why the above two kinds of specific epoxy resins (component A and component B) are used is as follows. That is, as described above, the crystalline epoxy resin which is the component A has excellent impregnability due to a rapid decrease in viscosity at a temperature equal to or higher than the melting point as described above, but on the other hand, the cured product thereof has a large rigidity, so that it easily becomes brittle. It has the drawback of being inferior in mechanical strength. On the other hand, the bisphenol A type epoxy resin, which is the B component, is flexible and has excellent resistance to cold and heat cycles, but on the other hand, it has a drawback that its melt viscosity is relatively high and impregnation is poor because of its large molecular weight. Therefore, by using both the component A and the component B, the respective defects can be compensated for while making use of the excellent properties of both, and a product having excellent properties can be obtained.

The mixing ratio of both the above-mentioned A component and B component is A / B = 60/40 to 90/1 in weight ratio.
It is preferable to set the ratio to 0. That is, when the amount of A component is less than 60 (the amount of B component exceeds 40), the impregnating property is deteriorated, and when the amount of A component exceeds 90 (the amount of B component is less than 10), the cured product becomes rigid and the cold-heat cycle resistance is deteriorated. This is because there is a tendency.

Of the two specific phenolic resins having a curing action on the two specific epoxy resins, the specific novolac type phenolic resin (component C) is represented by the following general formula (3). Therefore, it becomes possible to obtain a cured product having a high cross-link density and a high heat resistance due to its structure. On the other hand, the cured product has a drawback that it tends to be very brittle.

[0019]

[Chemical 13]

--C in R _{1 to} R ₃ in the above formula (3)
The ratio of H ₃ and -tert-C ₄ H ₉ 1: 2 is preferred.

Further, as the above novolac type phenol resin (component C), it is preferable to use one having a hydroxyl group equivalent of 130 to 160 and a softening point of 90 to 130 ° C.

The specific bisphenol A (D component) of the above two types of specific phenol resins is represented by the following general formula (4) and has a drastically low melt viscosity at a temperature above the melting point. It has the characteristic of having excellent impregnating property.

[0023]

[Chemical 14]

Further, the above bisphenol A (D component)
As a hydroxyl group equivalent of 110 to 120 and a melting point of 140 to
It is preferable to use one having a temperature of 160 ° C.

The mixing ratio of both the C component and the D component is C / D = 30/70 to 70/3 by weight.
It is preferable to set the ratio to 0. That is, when the C component is less than 30 (D component exceeds 70), the heat resistance is significantly lowered, and the C component exceeds 70 (D component is less than 30).
This is because the impregnating property and the resistance to cold and heat cycles tend to decrease.

Further, the compounding ratio of the two kinds of specific epoxy resins (components A and B) and the two kinds of specific phenol resins (components C and D) is such that the two kinds of specific epoxy resins (A Component and B component), the hydroxyl group equivalent in the two specific phenol resins (C component and D component) is 0.3 to 0.
It is preferable to set in the range of 8 equivalents. Ie 2
When the hydroxyl group equivalent in the specific phenolic resin (C component and D component) of less than 0.3 equivalent is deteriorated, heat resistance and thermal cycle resistance are deteriorated, and when it exceeds 0.8 equivalent, storage stability is deteriorated due to moisture absorption and the like. This is because there is a tendency for the adhesive strength of the obtained epoxy resin composition to decrease.

Moreover, the compounding ratio of the above novolac type phenol resin (component C) is such that the hydroxyl group equivalent in the component C is 0 relative to 1 equivalent of the epoxy group in the two specific epoxy resins (component A and component B). It is preferable to set in the range of 0.2 to 0.7 equivalent. That is, when the hydroxyl group equivalent in the C component is less than 0.2 equivalent, the heat resistance tends to decrease, and when it exceeds 0.7 equivalent, the fluidity tends to decrease.

The blending ratio of the bisphenol A (D component) is such that the hydroxyl group equivalent in the D component is 0.2 with respect to 1 equivalent of the epoxy groups in the two specific epoxy resins (A component and B component). It is preferable to set in the range of 0.8 equivalent. That is, if the hydroxyl group equivalent in the component D is less than 0.2 equivalent, the fluidity tends to decrease, and if it exceeds 0.8 equivalent, the heat resistance tends to decrease.

Further, the imidazole compound (E component) used together with the above-mentioned two specific epoxy resins (component A and component B) and two specific phenolic resins (component C and component D) acts as a curing accelerator. And is represented by the following general formula (5). Then, among the imidazole compounds represented by the above general formula (5), 2-methylimidazole is preferably used.
It is particularly preferable because it has excellent quick-curing properties and heat resistance.

[0030]

[Chemical 15]

The compounding amount of the imidazole compound (component E) is 0.2 to 5.0 in the epoxy resin composition.
It is preferable to set it to be a weight% (hereinafter abbreviated as “%”). That is, when the blending amount of the imidazole compound (E component) is less than 0.2%, the curing time may be long and the workability may be deteriorated. This is because it tends to decrease.

In the epoxy resin composition of the present invention, in addition to the above-mentioned components A to E, various conventionally used additives can be appropriately blended as required.

As the above-mentioned various additives, there are used fillers such as talc, silica sand, silica, calcium carbonate and barium sulfate, pigments such as carbon black, red iron oxide, titanium oxide, chromium oxide, cyanine blue and cyanine green, and other streams. Examples include regulators.

The blending amount of such various additives is usually
It is preferable to set the proportion of the epoxy resin composition to 0.5 to 200%, particularly preferably 0.5 to 50%.
Is.

The epoxy resin composition of the present invention has the above-mentioned A
~ E component and various additives can be produced by, for example, mixing each component by a conventionally known means such as a melt mixing method, and pulverizing and classifying.

The particle size in the classification is preferably set so as to pass through 30 mesh. By setting the particle size to the above, it is possible to obtain the effects of preventing dust scattering, blocking, and improving fluidity during melting.

The epoxy resin composition thus obtained is composed of the above-mentioned two types of specific epoxy resins (components A and B), two types of specific phenolic resins (components C and D), and specific imidazoles. By virtue of the action of the compound (component E), the powder as powder has a low viscosity when melted, is excellent in the gap filling property, and further has good wettability with respect to the article to be coated and coating property of the coating film. Further, it has excellent storability capable of withstanding long-term storage under high temperature and high humidity conditions. Also,
The cured product has excellent heat resistance and cold / heat cycle resistance. A composition having such characteristics.
Therefore, this epoxy resin composition is a powder adhesive,
It is suitable for use as powder paint, coil impregnation paint, and rust preventive material that is sprayed onto steel plates to prevent rust.

[0038]

As described above, the epoxy resin composition of the present invention comprises the specific epoxy resin represented by the general formulas (1) and (2) and the specific epoxy resins represented by the general formulas (3) and (4). Is a powdery resin composition containing the phenolic resin described above and an imidazole compound represented by the general formula (5). Therefore, it is excellent in adhesive strength in a high temperature atmosphere, shear adhesive strength after cooling / heating cycle, storability and impregnation property. Therefore,
The epoxy resin composition of the present invention is most suitable as a rust preventive material for powder adhesives, powder paints, coil impregnation paints, steel plates and the like.

Next, examples will be described together with comparative examples.

First, prior to the examples, the following epoxy resins a to f, phenol resins g and h, and 2-methylimidazole were prepared.

[Epoxy resin a]

[Chemical 16] Epoxy equivalent 170-210, melting point 90-120 ° C

[Epoxy resin b]

[Chemical 17] Epoxy equivalent 1500-2500, melting point 120-150
℃

[Epoxy resin c]

[Chemical 18] Epoxy equivalent 170-330, liquid

[Epoxy resin d]

[Chemical 19] Epoxy equivalent 450-900, melting point 50-70 ° C

[Epoxy resin e]

[Chemical 20] Epoxy equivalent 2400-3500, melting point 140-160
℃

[Epoxy resin f]

[Chemical 21]

[Phenolic Resin g]

[Chemical formula 22] Hydroxyl equivalent 130-160, softening point 110 ° C

[Phenolic resin h]

[Chemical formula 23] Hydroxyl equivalent 110-120, melting point 140-160 ° C

[2-Methylimidazole]

[0050]

Examples 1 to 15 and Comparative Examples 1 to 4 The components shown in Tables 1 to 4 below were blended in the proportions shown in the same table, melt-kneaded, pulverized, and classified (30 mesh pass). A target powdery epoxy resin composition was obtained.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

[Table 3]

[0054]

[Table 4]

With respect to the epoxy resin compositions of Examples and Comparative Examples thus obtained, the shear adhesive strength under 250 ° C., thermal cycleability, fluidity and storability were measured and evaluated according to the following methods. The results are shown in Tables 5 to 8 below.

(A) 250 ° C. shear adhesive strength Two steel plates each having a width of 10 mm, a length of 150 mm and a thickness of 1.0 mm were preheated at 250 ° C. and then lapped for 5 mm and bonded with an epoxy resin composition. Next, this is 250
The mixture was kept at 20 ° C. for 20 minutes for curing to prepare a shear adhesive strength test piece, and the shear adhesive strength of this test piece was measured using a tensile tester (initial shear adhesive strength). Then, the shear adhesive strength of this test piece in an atmosphere of 250 ° C. was measured, and shown as a ratio (%) to the initial shear adhesive strength.

(B) Cooling and Thermal Cycling Property A test piece produced by the above shear adhesive strength was 250 ° C. × 60 mi.
n and 20 ° C. water × 30 min were alternately stored, and after 10 cycles, the shear adhesive strength was measured and shown as a ratio (%) to the initial shear adhesive strength.

(C) Flowability 300 mg of the epoxy resin composition was compression-molded into a tablet having a diameter of 10 mm, the tablet was placed on a tilted plate in a curing oven at 180 ° C., and the flow length was measured. In addition,
The tilt angle was set to 30 °.

(D) Storability The epoxy resin composition was stored at 50 ° C. × 90% for 72 hours, and the fluidity after storage was measured by the same method as the fluidity of (c) above. It is shown as a ratio (%) to the value obtained in. In addition, whether or not the properties (powdered state) in the initial state are maintained and whether or not there is blocking were evaluated. Then, as a result, ◯ indicates no blocking, and x indicates blocking.

[0060]

[Table 5]

[0061]

[Table 6]

[0062]

[Table 7]

[0063]

[Table 8]

From Tables 5 to 8 above, the comparative example product is 250 ° C.
The measured values of shear adhesive strength, thermal cycleability, fluidity and storability under conditions are low. On the other hand, the example products obtained favorable values for all the test results. From these, it can be seen that the product of the example is excellent in both heat resistance and impregnation property. From the above, the example product is most suitable for use as a coil impregnating material, for example.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C09D 163/00 PJB

Claims (1)

[Claims] 1. An epoxy resin composition containing the following components (A) to (E). (A) A crystalline epoxy resin represented by the following general formula (1). [Chemical 1] (B) Bisphenol A represented by the following general formula (2)
Type epoxy resin. [Chemical 2] (C) A novolac-type phenol resin represented by the following general formula (3). [Chemical 3] (D) Bisphenol A represented by the following general formula (4). [Chemical 4] (E) An imidazole compound represented by the following general formula (5). [Chemical 5]