JPH07121997B2 - Cured product of epoxy resin powder composition, epoxy resin composition and method for curing epoxy resin powder composition - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a cured product of an epoxy resin powder composition which has excellent durability against mechanical shock and thermal shock, and also has excellent surface hardness and mechanical strength. The present invention relates to an epoxy resin powder composition that gives a product and a method for curing the composition.

[0002]

2. Description of the Related Art Conventionally, a powder composition in which an organic foaming agent such as azodicarbonamide is added to an epoxy resin is known (JP-A-63-273652).
A cured product obtained from an epoxy resin powder composition containing a foaming agent contains bubbles therein, and thus is obtained from a composition containing no foaming agent in terms of durability against mechanical shock or thermal shock. Better than the cured product. However, since a cured product obtained from an epoxy resin powder composition containing a foaming agent known so far contains a large amount of bubbles uniformly in the entire cured product, an epoxy resin powder containing no foaming agent. It was inferior in surface hardness, mechanical strength and water resistance as compared with the cured product obtained from the composition. In addition, since an organic foaming agent such as azodicarbonamide is used as a foaming agent, when the composition is heated and cured, rapid foaming occurs when the composition reaches its foaming temperature, and it is difficult to control foaming. There was a problem. In the field of small motors, in order to increase the output, a small armature is used, and a coil having a large wire diameter is wound around the coil with a large tension. Therefore, the armature insulating resin must have excellent impact resistance so that cracks and cracks are unlikely to occur, and that even if the coil rises to a high temperature when wound with a large tension, Has a high surface hardness to prevent it from being bitten, and has excellent thermal shock resistance so that cracks, cracks, and interfacial peeling do not occur even if thermal shocks from room temperature to high temperature and from high temperature to room temperature occur repeatedly. There are strong demands for characteristics such as The above-mentioned conventional epoxy resin powder composition containing a foaming agent cannot meet such a demand.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks found in an epoxy resin powder composition containing an organic foaming agent, is excellent in durability against mechanical shock and thermal shock, and has a surface hardness of A cured product of an epoxy resin powder composition having excellent mechanical strength and water resistance is provided, and an epoxy resin powder composition that gives such a cured product and is easy to control foaming is provided. It is an object to provide a method for curing the composition.

[0004]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, according to the present invention, in a cured product containing bubbles of an epoxy resin powder composition formed on a substrate, (i) the cured product comprises an epoxy resin, an acid anhydride and an alkali metal carbonate. A content of the alkali metal carbonate is 0.1 to 2 parts by weight per 100 parts by weight of the epoxy resin, (ii) the expansion ratio of the cured product is 7 Is in the range of ˜35%, (iii) there is a substantial amount of bubbles on the surface of the cured product that contacts the substrate, and (iv) there is substantially unevenness on the surface of the cured product due to blistering of bubbles. The present invention provides a cured product of an epoxy resin powder composition, which is characterized in that it does not exist. Further, according to the present invention, it is composed of an epoxy resin, an acid anhydride and an alkali metal carbonate, and the content of the alkali metal carbonate is epoxy resin 1
An epoxy resin powder composition is provided in a ratio of 0.1 to 2 parts by weight per 00 parts by weight. Furthermore, according to the present invention, an epoxy resin, an acid anhydride and an alkali metal carbonate are contained on the substrate, and the content of the alkali metal carbonate is
An epoxy resin powder composition having a ratio of 0.1 to 2 parts by weight per 100 parts by weight of the epoxy resin is adhered, and the composition is heated and cured through a base material to form a cured product containing bubbles. A method for curing a featured epoxy resin powder composition is provided.

The epoxy resin powder composition of the present invention is characterized by containing an acid anhydride and an alkali metal carbonate. In such a composition, carbon dioxide gas is generated as bubbles from the alkali metal carbonate by the action of the acid anhydride,
The carbon dioxide gas generation rate is related to the heating temperature, and the carbon dioxide gas generation rate increases as the heating temperature is increased. When the composition of the present invention is heated, a substantial amount of bubbles are generated at a temperature about 40 ° C. lower than the melting point of the acid anhydride,
A large bubble generation rate is obtained at a temperature near the melting point of the acid anhydride.

The epoxy resin used in the present invention may be any epoxy resin that is solid at room temperature, and conventionally known epoxy resins can be used. Examples thereof include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type or cresol novolac type epoxy resin, alicyclic epoxy resin,
Hydrogenated bisphenol A type or AD type epoxy resin,
Propylene glycol diglycidyl ether, aliphatic epoxy resin such as pentaerythritol polyglycidyl ether, epoxy resin obtained from aliphatic or aromatic carboxylic acid and epichlorohydrin, epoxy resin obtained from aliphatic or aromatic amine and epichlorohydrin, Examples thereof include a heterocyclic epoxy resin, a spiro ring-containing epoxy resin, and an epoxy modified resin.
If necessary, a thermoplastic resin can be blended with the epoxy resin, and a liquid epoxy resin can be blended within a range such that the resulting composition does not cause blocking.

Aliphatic and aromatic acid anhydrides are used as the acid anhydride, but aromatic acid anhydrides are preferably used. Specific examples of the acid anhydride include, for example,
Phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, 3,3 ', 4,4'-benzophenone tetracarboxylic acid anhydride, ethylene glycol-anhydrotrimellitate,
Glycerol-tris-anhydrotrimellitate, 5- (2,
Examples thereof include 5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic acid anhydride, tetrahydrophthalic acid anhydride, and 4,4′-oxydiphthalic acid anhydride. The acid anhydride acts as a curing agent for the epoxy resin, and reacts with the alkali metal carbonate under heating to generate carbon dioxide gas.

The composition of the present invention may contain, as a curing agent, another curing agent in addition to the above-mentioned acid anhydride. Examples of such a curing agent include mercaptan-based, amine-based, polyamide-based, boron-based, dicyandiamide-based, hydrazide-based, imidazole-based, phenol-based, amineimide-based curing agents, etc., but preferably phenol Resin is used. The proportion of the curing agent used is 0.5 to 1.5 equivalents, preferably 0.7 to 1. 1 equivalent of functional groups per epoxy equivalent of the epoxy resin.
It is a ratio of 2 equivalents.

The phenol resin which is preferably used in combination with an acid anhydride as a curing agent is a compound synthesized from phenols and formaldehyde and containing two or more OH groups in one molecule. Examples of such a resin include phenol novolac resin, cresol novolac resin, t-butylphenol novolac resin, octylphenol novolac resin, nonylphenol novolac resin, and bisphenol novolac resin. Further, the phenolic resin may be a mixture of the various phenolic resins, and in the production thereof, phenol and other phenols, for example,
It is also possible to use, as a raw material, a mixed phenol with one kind or two or more kinds of bisphenol A, bisphenol F, butylphenol, nonylphenol and the like, and react this with formaldehyde. The acid anhydride used in the present invention may be melt-kneaded with the phenol resin in advance and mixed in the phenol resin.

The acid anhydride and the phenol resin are used in proportion to the epoxy resin in an amount of 20 to 95% of the acid anhydride and 5 to 5 of the phenol resin with respect to the theoretical addition amount of each of them.
It is preferable to use them together at a ratio of 80%.

Examples of alkali metal carbonates include sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), and lithium carbonate (Li ₂ CO ₃ ). These alkali metal carbonates are usually used in the anhydrous form. The proportion of the alkali metal carbonate used is 0.1 to 2 parts by weight, preferably 0.5 to 100 parts by weight, based on 100 parts by weight of the epoxy resin.
It is 1.5 parts by weight. Moreover, 0.05 to 0.5 mol, preferably 0.1 to 0.
It is preferable to use it in a ratio of 3 mol. This alkali metal carbonate reacts with an acid anhydride to generate carbon dioxide gas when the composition is heated and cured. The alkali metal carbonate also has the effect of shortening the gel time of the composition.

The composition of the present invention optionally contains a curing accelerator. As the curing accelerator, various compounds conventionally used for epoxy resins can be used. Specifically, tertiary amines such as triethylamine, N, N-dimethylbenzylamine, 2,4,6-tris (dimethylaminomethyl) phenol, N, N-dimethylaniline: 2-methylimidazole, 2-phenyl Imidazole compounds such as imidazole; various salts of imidazole compounds such as imidazole compounds such as triazine salts, cyanoethyl salts, cyanoethyl trimellitate salts; metal compounds such as zinc acetate and sodium acetate; quaternary ammonium salts such as tetraammonium bromide other,
Amide compound, peroxide, azo compound, cyanate compound, isocyanate compound, triphenylphosphine,
Examples include DBU phenol novolac salts and the like. The amount of the curing accelerator used is 0.05 to 10 parts by weight, preferably 0.1 to 100 parts by weight, based on 100 parts by weight of the epoxy resin.
It is 5.0 parts by weight.

The composition of the present invention optionally contains a filler. As the filler, conventionally known inorganic or organic fillers can be used. Examples of such fillers include calcium carbonate, magnesium carbonate,
Powders of silica, alumina, talc, clay, mica, nylon and the like can be mentioned, but inorganic fillers are preferably used. These fillers may be surface-treated with a surface treatment agent such as a silane coupling agent or polysiloxane, or may not be surface-treated. The filler is used in an amount of 30 to 270 parts by weight, preferably 100 to 25 parts by weight, based on 100 parts by weight of the epoxy resin.
0 parts by weight. As the filler, those having an average particle size of 0.5 to 100 μm, preferably 0.5 to 80 μm (D ₁ ) and those having an average particle size of less than 0.5 μm, preferably 0.1 μm or less ( It is preferred to use two fillers consisting of D ₂ ). The ratio of the component (D ₁ ) is 99.7.
˜87.0% by weight, preferably 99.5 to 90.0% by weight, the proportion of the component (D ₂ ) is 0.3 to 13.0% by weight,
It is preferably 0.5 to 10.0% by weight.

The composition of the present invention comprises, in addition to the above-mentioned components, if necessary, further flame retardants such as hexabrombenzene, antimony trioxide and tetrabromobisphenol A; carbon black, titanium oxide, red iron oxide, chromium oxide and the like. Coloring agent: various coupling agents of zirco aluminum type, silane type, titanium type, leveling agent consisting of acrylic acid ester oligomer, butyral resin, rubber component (CT
BN, NBR, etc.), polyester resin, etc. can be contained in appropriate amounts.

The preferred composition of the present invention is 100 parts by weight of epoxy resin, 5 to 35 parts by weight of acid anhydride, 2 to 30 parts by weight of phenol resin, 0.05 to 5 parts by weight of curing accelerator, and 130 to 130 parts of inorganic filler. 270 parts by weight and 0.1 to 2 parts by weight of alkali metal carbonate. Such a composition provides a cured product having excellent durability against thermal shock and mechanical shock, as well as excellent mechanical strength and water resistance, and easily controls the bubble generation rate by the heating temperature. be able to.

The composition of the present invention is applied to the surface of a substrate by a conventionally known powder coating method such as a fluidized dipping method, an electrostatic coating method and a spray method. The composition applied to the surface of the substrate is
It is heated through the substrate, and this heating softens and cures. The heating of the composition can be carried out by applying the composition to the surface of the base material which has been heated in advance, or by applying the composition to the surface of the base material and then heating the base material. You can Conventionally known heating methods such as hot air, electric current heating, dielectric heating, and high frequency heating are used for heating the base material. The heating temperature of the substrate is usually in the range of about 40 ° C. below the melting point of the acid anhydride to about 50 ° C. above the melting point of the acid anhydride.

When the composition deposited on the substrate is heated and cured through the substrate, the temperature of the composition surface in contact with the outside air is lower than the temperature of other parts. On the other hand, the temperature of the part of the composition that contacts the substrate is higher than the temperature of the other parts. Therefore, the cured product obtained by heating the composition deposited on the substrate through the substrate does not have substantial bubbles on the surface of the cured product that comes into contact with the outside air, and the bubbles on the surface of the cured product are not present. The occurrence of surface irregularities due to swelling is prevented, and the surface quality is good.
The surface hardness is high. When heating the composition attached to the surface through the substrate, the surface temperature of the composition is determined by blowing a cooling gas onto the composition.
It can be further lowered, whereby a cured product having a higher surface hardness can be obtained.

The substrate used in the present invention means an article to which the composition is applied, including a metal plate, an iron core, a ceramic plate,
It includes electronic components, winding coils for motors and generators, and the like.

The expansion ratio of the cured product obtained from the composition of the present invention is in the range of 7 to 35%, preferably 7 to 30%. If the expansion ratio is higher than 35%, it will be difficult to prevent the occurrence of surface irregularities due to air bubble swelling on the surface of the cured product, while if the expansion ratio is lower than 7%,
The obtained cured product has poor durability against thermal shock and mechanical shock. The expansion ratio of the cured product in this specification is represented by the following formula. R (%) = (A−B) / A × 100 R: Expansion ratio (%) A: Density of unfoamed cured product (g / cm ³ ) B: Density of expanded cured product (g / cm ³ ).

[0020]

EXAMPLES Next, the present invention will be described in more detail by way of examples. Example 1, Comparative Example 1 A mixture composed of the components (parts by weight) shown in Table 1 was melt-mixed in an extruder and pulverized to obtain a desired particle size distribution to obtain a powder coating material. . Next, the gelation time of these powder coating materials was examined. The density, impact resistance, heat shock resistance, and the presence or absence of air bubbles in the cured product were examined for the cured product obtained by curing this powder coating material. The results are shown in Table 2. In addition, the measurement of each physical property is performed as shown below.

Gelation time: According to JIS C2104, sample powder is about 0.1 to 0.2.
g was put in a circular recess of a hot plate kept at 200 ° C., and the time until the powder gelled was measured.

(Impact resistance) A 60 × 60 × 3.0 mm iron plate preheated to 230 ° C. is coated with a sample powder by a fluid immersion method so that the thickness of the coating film becomes 0.5 mm. Then, let it stand for 30 seconds,
Allow the gelling reaction to proceed sufficiently to the surface, then 200 ° C,
It was post-cured under the condition of 30 minutes. The obtained cured film was allowed to stand at room temperature after coating and then gradually cooled. Using a DuPont type impact tester, the load is dropped from 500 mm onto the cured film. At that time, the cured film has no cracks or cracks, ○, slightly there is Δ, and many there are ×. The evaluation was made in 3 stages.

(Heat Shock Resistance) Motor armature (slot diameter: 55 mmφ, stacking thickness: 40 mm, slot width: 3 mm, number of slots: 1)
(4, shaft diameter: 8 mm) was preheated to a temperature of 230 ° C, sample powder was adhered to the surface of the surface, coated, allowed to stand for 30 seconds, and then post-cured at 200 ° C for 30 minutes. Was used as a sample. This sample is subjected to a condition of 125 ° C. × 1 Hr and −40 ° C.
10 heat shock processes consisting of applying 1Hr
After repeating 0 times, the appearance of the cured film was checked, and those having no cracks or chips were evaluated as ◯, those having some cracks were evaluated as Δ, and those having many were evaluated as ×.

(Specific gravity of unfoamed molded product) A mold is used by pressing at a temperature of 75 ° C. lower than the melting point of the acid anhydride used (substantially no foaming reaction occurs) at 150 ° C. for 10 minutes, and a molding pressure is applied. 47 m / cm ² and thickness of 3 m
The specific gravity of an unfoamed molded product that was molded by molding a molded product of m and then post-cured at 150 ° C. for 60 minutes was measured. (Specific gravity of cured product) 100 mm x 100 mm x 3 mm release-treated mild steel sheet preheated to 230 ° C was coated with a sample powder with a film thickness of about 0.5 mm by a fluidized dipping method, and left in that state for 30 seconds After 20
After post-curing at 0 ° C. for 30 minutes, the cured film was peeled off and the specific gravity of the cured film was measured.

(Presence or absence of bubbles in the cured product) The cross section of the cured product film obtained in the measurement of the specific gravity of the cured product was observed with an electron microscope to examine whether or not there were bubbles in the cured product film. As a result, it was confirmed that in the cured product film of Example 1, bubbles were concentrated on the contact surface portion with the base material (mild steel plate), and substantially no bubbles were present on the surface portion. On the other hand, the cured product film of Comparative Example 1 was found to show some expansion ratio due to the gas contained in the raw material powder,
At such an expansion ratio, the performance of the cured film was still unsatisfactory.

[0026]

[Table 1]

[0027]

[Table 2]

The specific contents of the components shown in Table 1 are as follows. Epoxy resin (1): Bisphenol A type epoxy resin, epoxy equivalent 92
5, trade name Epicoat 1004, Epoxy Shell Epoxy Co., Ltd. epoxy resin (2): o-cresol novolac epoxy resin, epoxy equivalent 211, trade name Epicoat E180S75, Yuka Shell Epoxy Co., Ltd. inorganic filler (1) ): Calcium carbonate, trade name KC-30, average particle size 6.5 μ
Inorganic filler (2) manufactured by Bihoku Powder Co., Ltd .: Light calcium carbonate, trade name Homocal D, average particle size 0.
07 μm, manufactured by Shiraishi Industry Co., Ltd. Acid anhydride: 3,3 ′, 4,4′-benzophenone tetracarboxylic acid anhydride Phenolic resin: Orthocresol novolac resin, trade name OCN13
0, softening point 130 ° C., Nippon Kayaku Co., Ltd. curing accelerator: 1-cyanoethyl-2-phenylimidazolium trimellitate, product name 2PZ-CNS, Shikoku Kasei Co., Ltd. leveling agent: acrylic acid ester oligomer , Viscosity 1300cps
(25 ° C.), trade name Nicalite XK-21, manufactured by Nippon Carbide Industry Co., Ltd. Sodium carbonate: Commercially available granular Na ₂ CO ₃ .H ₂ O is crushed with a dairy drum to prepare 1
Dehydrated by heating at 50 ° C for 1 hour

Example 2 In Example 1, the preheating temperature of the iron plate in the impact resistance test was changed to 200 ° C., the preheating temperature in the heat shock resistance test was changed to 200 ° C., and the specific gravity of the cured product was measured. The same experiment was conducted except that the preheating temperature was changed to 200 ° C.

Example 3 In Example 1, the preheating temperature of the iron plate in the impact resistance test was changed to 250 ° C., the preheating temperature in the heat shock resistance test was changed to 250 ° C., and the specific gravity measurement test of the cured product was conducted. An experiment was conducted in the same manner except that the preheating temperature was changed to 250 ° C. The following table shows the results obtained in Example 2 and Example 3 described above.

[0031]

[Table 3]

[0032]

The composition of the present invention, when heated,
Carbon dioxide gas is generated as bubbles to give a cured product containing bubbles. Since the bubble generation rate of the composition of the present invention can be easily controlled by the heating temperature, the foaming ratio of the cured product can be delicately controlled by the heating temperature. A cured product containing bubbles obtained by heating and curing the composition of the present invention through a substrate has substantially no bubbles on its surface and has no surface irregularity due to bubble swelling. Therefore, this cured product has a high surface density, excellent surface hardness, and excellent water resistance and chemical resistance. Further, since bubbles are present inside the cured product, mechanical impact and heat It has excellent durability against mechanical impact and mechanical strength.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location C09D 163/00 PJU // C08L 63:00 (72) Inventor Mikio Naga Ginza, Chuo-ku, Tokyo Inc. 11-2 Somer Co., Ltd. (72) Inventor Ken Watanabe Inc. 4-11-2 Ginza, Chuo-ku, Tokyo In Somar Co., Ltd. (56) Reference JP-A-1-103633 (JP, A)

Claims (9)

[Claims] 1. A cured product containing bubbles of an epoxy resin powder composition formed on a substrate, comprising: (i) the cured product consisting of an epoxy resin, an acid anhydride, and an alkali metal carbonate. The metal carbonate is formed from a composition having a content of 0.1 to 2 parts by weight per 100 parts by weight of the epoxy resin, (ii) the expansion ratio of the cured product is 7 to 35% (Iii) Substantial amount of bubbles are present on the surface of the cured product which contacts the substrate, and (iv) Substantially unevenness due to swelling of bubbles is present on the surface of the cured product. A cured product of an epoxy resin powder composition, characterized by: 2. The cured product of the epoxy resin powder composition comprises 100 parts by weight of an epoxy resin, 5 to 35 parts by weight of an acid anhydride, 2 to 30 parts by weight of a phenol resin, and a curing accelerator of 0.0.
2. An epoxy resin powder composition comprising 5 to 5 parts by weight, 130 to 270 parts by weight of an inorganic filler, and 0.1 to 2 parts by weight of an alkali metal carbonate. A cured product of the epoxy resin powder composition. 3. The cured product of the epoxy resin powder composition according to claim 1, wherein the base material is a metal plate, an iron core, a ceramic plate, an electronic component or a wound coil. 4. An epoxy resin, an acid anhydride and an alkali metal carbonate, wherein the content of the alkali metal carbonate is
An epoxy resin powder composition having a ratio of 0.1 to 2 parts by weight per 100 parts by weight of the epoxy resin. 5. An epoxy resin 100 parts by weight and an acid anhydride 5
To 35 parts by weight, phenol resin 2 to 30 parts by weight, curing accelerator 0.05 to 5 parts by weight, inorganic filler 130 to 270 parts by weight and alkali metal carbonate 0.1 to 2 parts by weight. Composition. 6. A base material comprising an epoxy resin, an acid anhydride and an alkali metal carbonate, wherein the content of the alkali metal carbonate is 0.1 to 2 parts by weight per 100 parts by weight of the epoxy resin. A method for curing an epoxy resin powder composition, which comprises applying a certain epoxy resin powder composition and heating and curing the composition through a substrate to form a cured product containing bubbles. 7. An epoxy resin 100 parts by weight on a substrate,
Acid anhydride 5 to 35 parts by weight, phenolic resin 2 to 30 parts by weight, curing accelerator 0.05 to 5 parts by weight, inorganic filler 130
To 270 parts by weight and 0.1 to 2 parts by weight of an alkali metal carbonate are attached, and the composition is heat-cured through a substrate to form a cured product containing bubbles. A method for curing an epoxy resin powder composition, comprising: 8. The epoxy resin powder composition according to claim 6, wherein the base material is previously heated to a curing temperature of the composition before the epoxy resin powder composition is attached. Curing method. 9. The method for curing an epoxy resin powder composition according to claim 6, wherein the base material is heated at a high frequency to a curing temperature of the composition to which the epoxy resin powder composition is attached. .