JPH0617454B2 - Flexible epoxy resin powder composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an epoxy resin powder composition used for a film capacitor for an AC power supply, a film capacitor having a safety function, etc., and is subjected to charge / discharge treatment under overvoltage. The present invention relates to an epoxy resin powder composition capable of providing a coating film having flexibility that does not break even when it is used.

[Prior art]

Epoxy resin powder coating has excellent adhesion, chemical resistance, thermal stability, mechanical properties, and insulation in terms of characteristics.
In terms of work, it is used in various fields such as electrical insulating materials because it is pollution free, resource saving and energy saving.

Epoxy resin powder coatings used for film capacitors generally form a hard coating film and satisfy mechanical strength and moisture resistance.

By the way, in the film capacitor for AC power supply and the film capacitor with a safety function, there is a risk that the exterior coating material sometimes expands and breaks when an overvoltage is applied to cause insulation failure.

This phenomenon is caused by JIS C4908 "Capacitors for electrical equipment" or US UL (Underwriter's Laboratories Inc.) 141
4 It is standardized as the Discharge Test of "Across-The-Line-CAPACITORS".

Conventionally, an epoxy resin powder coating which forms a hard coating film has also been used for this type of film capacitor.

This is because, in the charge / discharge test, the coating film could be destroyed even if it was broken unless the electrode portion was peeled off.

However, when it is used in household electric appliances such as fluorescent lamps, washing machines, and refrigerators, it has been destroyed and ignited. Therefore, it has been required that the exterior coating material should not be destroyed.

[Object of the Invention]

With the conventional epoxy resin powder coating, the problem that the outer coating material is destroyed by the overvoltage charge / discharge test and the insulation failure is unavoidable, but the present inventors have studied to prevent this. In order to complete the present invention, we have obtained the knowledge that by giving flexibility to the coating film, the coating film does not break by absorbing the stress of expansion and contraction of the film capacitor due to the charge-discharge test, and it does not break. It has come.

[Structure of Invention]

In the present invention, the epoxy resin is 70% by weight or more of the whole, 10 to 30% by weight of the epoxy resin is a dimer acid-modified epoxy resin, and 100 parts by weight of the epoxy resin, 2 or more acid anhydride groups, Alternatively, an acid anhydride compound having at least one acid anhydride group and at least one carboxyl group may be used.
To 20 parts by weight of the flexible epoxy resin powder composition.

It is essential that the epoxy resin used in the present invention accounts for 70% by weight or more of the total composition, and if it is less than 70%, it becomes difficult to obtain sufficient flexibility in the cured product.

Examples of commercially available dimer acid-modified epoxy resin used in the present invention include Epotote YD-172 (trade name, manufactured by Toto Kasei Co., Ltd.). The dimer acid-modified epoxy resin is used by mixing in the range of 10 to 30% by weight, preferably 15 to 25% by weight, based on the whole epoxy resin.

When the dimer acid-modified epoxy resin is added, flexibility is particularly improved among the properties of the resulting resin cured product.

Dimer acid here means linoleic acid, linolenic acid,
It is a dimer of a long-chain fatty acid such as oleic acid, and has a molecularly good stretchability in the long-chain portion. A dimer acid-modified epoxy resin can be obtained by introducing an epoxy group into the terminal portion of this compound.

When the dimer acid-modified epoxy resin is incorporated into the molecular network of the cured product when cured, the stretchability of the cured product itself, that is, flexibility is improved.

In other words, when used as a paint, the coating film as a cured product can have good flexibility like rubber.

If the addition amount is less than 10% by weight, the effect is insufficient, and if it is 30% by weight or more, the melting point is lowered and a blocking phenomenon occurs during storage, resulting in poor fluidity of powder and uneven coating during coating. Or, it may be difficult to use.

When the epoxy equivalent excluding the dimer acid-modified epoxy resin according to the present invention is 1000 or more, the epoxy resin has insulating properties, corrosion resistance, and
It is a component that imparts chemical resistance.

The epoxy resin satisfying the above characteristics is usually a bisphenol A type epoxy resin or a novolac type epoxy resin, and various grades are used alone or as a mixture, and the epoxy resin equivalent is 600 to 1 on average.
The range of 000 is preferable.

When the epoxy equivalent is less than 600, since the melting point of the epoxy resin is low, a blocking phenomenon occurs during storage, which causes poor fluidity of powder during coating, uneven coating, or makes it completely difficult to use. There is also a fear of becoming. Also,
When the epoxy equivalent is 1000 or more, the melting point of the epoxy resin is high, so when coating the film capacitor,
It must be heated to a temperature higher than the melting point of the film, otherwise the amount of adhesion will be small and efficient painting will be difficult.

The novolac type epoxy resin is an ortho-cresol type epoxy resin or a novolac type epoxy resin.
It is preferably used in an amount of not more than wt%. The novolac type epoxy resin is used to improve the moisture resistance,
Usually, if it exceeds 20% by weight, the coating tends to become brittle, which is not preferable.

The curing agent used in the present invention has 2 acid anhydride groups in the molecule.
Or more, or an acid anhydride curing agent having one or more acid anhydride groups and one or more carboxyl groups, and examples thereof include trimellitic anhydride, pyromellitic dianhydride, ethylene glycol bis trimellitate, glycerol tris trimellitate. Tate etc. can be given. The above acid anhydride curing agent has two or more acid anhydride groups or one or more acid anhydride groups and one carboxyl group which are considered to be involved in curing in the molecule.
It is necessary to have more than one. If it is less than this, the moisture resistance of the film capacitor when formed into a coating film is insufficient, which is not preferable.

Moisture resistance is considered to be correlated with the polymer structure forming the coating film, and tends to improve as the molecular network becomes denser. Therefore, it is preferable that the curing agent that serves as the base of the curing network has more functional groups for moisture resistance.

When any of the above curing agents is used, the epoxy resin 10
With respect to 0 parts by weight, 7 to 20 parts by weight, particularly 9 to 18 parts by weight are preferable. At this time, if it is less than 7 parts by weight, the curing rate is remarkably reduced and the cured product is in an insufficiently cured state, so that the mechanical strength of the cured product becomes insufficient, and the flexibility tends to be small and brittle, which is not preferable.

If the amount is more than 20 parts by weight, the storability is deteriorated, and in some cases, the molten state at the time of coating is not good, which may lead to lack of smoothness.

The epoxy resin powder composition of the present invention can be obtained by mixing the components as described above, and various fillers such as silica, calcium carbonate, barium sulfate, alumina powder, talc and clay, titanium dioxide, zinc oxide, It is also possible to add pigments such as iron oxide and graphite, additives such as flow control agents, amines and imidazole derivatives for adjusting the gelation time and the curing time within a range that does not adversely affect flexibility.

〔The invention's effect〕

The coating film obtained by applying a coating to a film capacitor preheated with the epoxy resin powder composition of the present invention by means such as a fluidized dipping method has excellent reliability of the capacitor, and even after repeated charging and discharging. It does not break or crack and is extremely effective in improving safety.

〔Example〕

 Examples of the present invention will be shown below.

Examples 1 to 6 The components were blended in the proportions shown in Table 1, preliminarily mixed with a Henschel mixer, and then kneaded with a twin-screw extruder to give epoxy resin compositions. Next, the composition was pulverized to obtain an intended epoxy resin powder composition.

However, the dimer acid-modified epoxy resin in Table 1 is YD-172 (epoxy equivalent of about 650) manufactured by Tohto Kasei Co., Ltd., and the cresol novolac type epoxy resin is EOCN-102S (epoxy equivalent of Nippon Kayaku Co., Ltd.). 220)
Is.

Comparative Examples 1 to 6 Epoxy resin powder compositions were obtained with the formulations shown in Table 1 by the same operations as in the examples.

With respect to the above powder composition, a charging / discharging test of the coating film was performed as follows.

Coating film charge / discharge test method After preheating the film capacitor to 100 ° C and applying each epoxy resin powder coating material to a film thickness of 500 μm by the fluid immersion method, heat it in the atmosphere of 100 ° C for 2 hours and then to room temperature. Cooled. The state of the obtained coating film was examined according to the safety test of JIS C4908.

The judgment was performed as follows.

◯: No cracks occur.

X: A crack was generated.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01B 3/40 F 9059-5G H01G 4/18 327 Z 8019-5E

Claims (1)

[Claims] 1. Epoxy resin accounts for 70% by weight or more of the whole, 10 to 30% by weight of the epoxy resin is a dimer acid-modified epoxy resin, and two acid anhydride groups are added to 100 parts by weight of the epoxy resin. A flexible epoxy resin powder composition comprising the above or 7 to 20 parts by weight of an acid anhydride curing agent having at least one acid anhydride group and at least one carboxyl group.