JPS5827828B2 - Epoxy powder coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to epoxy powder coating compositions.

In recent years, with the production of high-performance laminates and the rationalization of coating processes in the electrical industry, there have been an extremely large number of opportunities to use powder coatings that enable pollution-free production, especially epoxy powder coatings with excellent electrical properties.

In addition, as a recent trend, along with the reinforcement of flame retardancy related to UL standards, the requirements for thermal shock resistance of electronic components are becoming stricter.

The specific details of the thermal shock resistance test are as follows: -
Thermal shock resistance test was performed for 5 cycles by leaving the product in an atmosphere of 30℃ for 30 minutes and then in an atmosphere of +85℃ for 30 minutes to check the occurrence of cranking and the characteristics of the molded electronic components. However, recently, the temperature has been changed to -40℃ to +85℃, left for 30 minutes each, 100 cycles, and even -55℃ to +125℃.
℃, left for 45 minutes, 100 cycles, and (1) test conditions are becoming more common.

On the other hand, the common bisphenol A type epoxy resin has an aromatic nucleus, and therefore has the disadvantage of not only high rigidity but also high brittleness, that is, low thermal shock resistance.

However, there are very few commercially available solid products made of epoxy resins other than bisphenol A type, and they are expensive.

Conventionally, methods used to improve thermal shock resistance include adding plasticizers and flexible epoxy resins, but the physical and electrical properties after the resin hardens are significantly reduced. I couldn't get away with it.

In order to overcome these shortcomings, the present inventors have conducted intensive research to improve thermal shock resistance by adding a high molecular weight thermoplastic resin to epoxy resin, and have investigated the physical properties, electrical properties, and electrical properties of epoxy resin after curing. It has been discovered that random copolymerized saturated polyester is suitable, taking into consideration its compatibility with

Generally used thermoplastic polyesters are linear polymeric saturated polyesters formed by the condensation polymerization of dibasic acids and dihydric alcohols. -1- is common.

However, as it is, there are problems with flexibility and adhesiveness.

Therefore, if a part of the dibasic acid is replaced with another component and random condensation polymerization is performed, the flexibility and adhesiveness are significantly improved.

The present invention was developed in view of point 1, and includes a bisphenol A epoxy resin, a curing agent for curing the bisphenol A epoxy resin, terephthalic acid as the main component, sebacic acid, succinic acid, adipine, etc. Consisting of a condensation product of acid and ethylene glycol, with a molecular weight of 500 or more.
Random copolymerized saturated polynisdel of
X-250J (commercially available as Byron 30PJ)
A powdered epoxy resin was prepared by blending 1 to 30 weight percent of the following, and further blending 2 to 20 weight weight of a phosphoric acid ester plasticizer thereto.

A thermal shock resistance test was conducted on the samples obtained by molding the powdered epoxy resin of the present invention into electronic parts using the fluidized dip coating method. As a result, no cracks were observed after 100 cycles of testing, and electrical Almost no changes were observed in properties or physical properties.

Comparative Examples and Examples of the present invention will be explained below by showing the results of various tests.

Comparative Example 100 parts by weight of a bisphenol A-type epoxy resin with an epoxy equivalent of 850, 6 parts by weight of dicyandiamide (epoxy resin curing agent), 25 parts by weight of talc, 2 parts by weight of a colored pigment and a random copolymerized saturated polyester ("Vylon GX- 250J, Toyobo Co., Ltd., 15 parts by weight was heated to about 15 parts by weight on two rolls adjusted to 120°C.
The mixture was kneaded for a minute, taken out into a sheet and pulverized, and the amount that passed through an 80-mesh standard sieve was collected.

For comparison, a non-additive composition of Kiboshin's random copolymerized saturated polynisdel ("Vylon GX25o", Toyobo Co., Ltd.) was prepared in the same manner as described above.

Two types of powder paints were applied to a ceramic varistor element using a fluidized dip coating method, and a thermal shock resistance test was conducted.

The number of samples for each was 20.

The results are shown in the table below. As is clear from the above results, random copolymerized saturated polyester ("Vylon GX250J
) did not cause any cracks in the 100-cycle thermal shock test, while samples without additives showed cracks in all of the thick and large devices.

The characteristics of the device before and after the thermal shock resistance test remained unchanged regardless of whether random copolymerized saturated polyester was added or not.

However, in this characteristic measurement, the element in which cranking occurred was excluded from the target.

Example 100 parts by weight of a bisphenol A type epoxy resin with an epoxy equivalent of 1900, 3.6 parts by weight of diaminodiphenylsulfone (epoxy resin curing agent), 35 parts by weight of calcined clay, 2 parts by weight of a colored pigment, and a phosphate ester plasticizer. 1
A comparison is shown below between a composition in which 10 parts by weight of a random copolymerized saturated polyester ("Vylon 30P", Toyobo Co., Ltd.) was added to a composition of 5 parts by weight, and a composition in which no additive was added.

As a method for producing a powder coating, the mixture was kneaded for about 15 minutes on two rolls adjusted to 135°C, taken out into a sheet, pulverized, and the amount that passed through a standard sieve of 80 mesh was collected.

Using the obtained powder paint, a porcelain capacitor (27 mm φ, 3.5 mm t)*wood was coated by a fluidized dipping method.

The following table shows the thermal shock resistance test results of 50 samples for each sample.

As mentioned above, by adding random copolymerized saturated polyester, thermal shock resistance is greatly improved, and
Regarding the electrical properties and physical properties, it can be seen that there is almost no change in the thermal deformation temperature, except for a slight decrease.

However, if the amount of random copolymerized saturated polyester exceeds 30% by weight, it becomes difficult to grind, so the total amount including the resin should be 1 to 30% by weight, more preferably 5 to 15% by weight. .

Next, the epoxy powder coatings of Comparative Examples and Examples were applied to ceramic varistors, and after being left at 120° C. for 500 hours, a thermal shock resistance test was conducted.

As a result, cranking occurred in the comparative example as shown below.

The element coated with the powder coating of the comparative example was heated to 500℃ at 120℃.
When the thermal shock resistance test was carried out for 14 minutes without being left for a long time, no cracks were generated, but in the test after being left at a high temperature, a considerable amount of cracking occurred.

A possible cause of this is that when left at high temperatures, random copolymerized saturated polyester has hydroxyl and carboxyl groups at the molecular chain ends, which react with epoxy groups and reduce its flexibility. .

In other words, if it is a random copolymerized saturated polyester or if it is scattered in the powder coating without reacting with the epoxy group, there is little change in flexibility before and after leaving it at high temperatures.

In order to inhibit the reaction between the epoxy group and the hydroxy group or carboxyl group at the molecular chain end of the polyester, it is effective to add a phosphoric ester plasticizer.

It is thought that 1 phosphorus in the phosphoric acid ester plasticizer suppresses the action of the catalyst, significantly reducing the reaction.

It was also found that the addition of Nisdel phosphate plasticizers was effective in increasing storage stability.

Specifically, no cracks were observed in the compositions of Examples even when subjected to a thermal shock resistance test after being left at high temperatures.

In other words, by adding a phosphate ester plasticizer (commercially available products such as triphenylphos-1) and random copolymerized saturated polyester to the epoxy resin, there is less influence of changes over time due to high temperature storage, etc. can maintain excellent thermal shock resistance.

The amount of phosphoric acid ester plasticizer is 2 to 20 percent by weight of the composition, and 5 to 15 percent by weight, taking into account the bagging during storage of the powder paint.
It's weight related.

As mentioned above, bisphenol A type epoxy resin,
By containing the random copolymerized saturated polyester in a weight coefficient of 1 to 30% relative to the total amount of the resin, thermal shock resistance can be improved without lowering electrical properties or physical properties.

Furthermore, 2 to 20% of the phosphoric acid ester plasticizer is added to the resin composition.
By adding it in combination with weight, it is possible to obtain an epoxy powder coating with little change in thermal shock resistance over time after being left at high temperatures.

Claims (1)

[Claims] 1 Bisphenol A type epoxy resin, a curing agent for curing this bisphenol A type epoxy resin, and a random copolymerized saturated polyester resin with terephthalic acid as the main component, sebacic acid, succinic acid, adipic acid, and ethylene glycol with an average molecular weight of An epoxy powder coating composition comprising 1 to 30% by weight of a 500 or more phosphoric acid ester plasticizer and 2 to 20% by weight of a phosphoric acid ester plasticizer.