JPH05263043A - Composition for forming terminal protecting film - Google Patents

Abstract

PURPOSE:To provide the subject compsn. which prevents adhesion of varnish and facilitates soldering after varnish treatment. CONSTITUTION:This compsn. contains an org. solvent and a urethane resin which is prepd. by reacting a diisocyanate with a 10C or lower hydrocarbonbased compd. having three hydroxyl groups in a molar ratio of the OH groups of the compd. to the NCO groups of the diisocyanate of 1.5 or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for forming a terminal protective film, which is used as a protective material for connecting terminals of electric equipment such as coils to which a varnish is impregnated.

[0002]

2. Description of the Related Art For electric devices such as motors and transformers,
Usually leads are connected for electrical input and output to the coil. However, in recent years, electric devices in which terminals such as connectors are attached to the input / output portions instead of the lead wires have been used. The electrical equipment such as the coil is treated with an insulating varnish for the purpose of insulating repair and fixing. And in the coil with the above terminals, by the insulating varnish treatment,
A hardened material is formed on the input / output terminal portion by the insulating varnish treatment, and the terminal portion is covered with insulation. For this reason, it is necessary to remove the cured varnish from the terminal portion because the lead wire cannot be soldered in the subsequent step. In recent years, unsaturated polyester has been widely used as the insulating varnish.

[0003]

Since the above unsaturated polyester does not decompose at a soldering temperature of 200 to 400 ° C., it is necessary to remove the unsaturated polyester cured product mechanically treated with an insulating varnish. For this,
For example, there has been proposed a method in which an insulating varnish is not attached by applying a release material such as silicon or fluorine resin to the terminal portion. However, even with the above method, it is difficult to completely prevent the varnish from adhering, and even if a small amount of a release material such as silicon or fluororesin is mixed in the insulating varnish, the iron core or There is a problem in that the coil portion causes a repellency phenomenon, which adversely affects the insulation, adhesion, etc., which is the purpose of varnish treatment. In addition, a method of protecting the terminal part with a masking tape has been proposed and implemented partially, but this method requires steps such as tape attachment and removal, which complicates the work process and results in mass production of electrical equipment. It is not realistic from the viewpoint of sex.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a composition for forming a terminal protective film, which can prevent the adhesion of varnish and can easily perform solder connection after varnish treatment. And

[0005]

In order to achieve the above object, the composition for forming a terminal protective film of the present invention comprises an organic solvent, a urethane resin obtained by reacting the following component (A) with diisocyanate. A composition for forming a terminal protective film, which comprises: (A) component and OH in the component and NC in the diisocyanate.
The ratio (OH / NCO) with O is set to be 1.5 / 1 or more. (A) A hydrocarbon compound having 3 hydroxyl groups and having 10 or less carbon atoms.

[0006]

That is, the present inventors have conducted a series of researches in order to obtain a varnish that can be subjected to solder treatment without removing the varnish at the time of solder connection. As a result, a specific hydrocarbon-based compound and diisocyanate, using a urethane resin obtained by reacting at a specific ratio, using a composition containing this in an organic solvent, to apply this to the terminal to form a protective film. When formed, the protective film protects the terminal portion from the cured product of the electrically insulating varnish, and during solder connection, the protective film can be removed together with the varnish depending on the solder connection temperature, so that solder connection can be easily performed. Therefore, it is not necessary to go through the step of removing the varnish, and the workability can be improved.

Next, the present invention will be described in detail.

The terminal protective film-forming composition of the present invention can be obtained by using a specific urethane resin and an organic solvent.

The above-mentioned specific urethane resin is obtained by reacting a hydrocarbon compound (component A) having three hydroxyl groups and having 10 or less carbon atoms with diisocyanate.

As described above, in the present invention, the hydrocarbon compound has three hydroxyl groups and has 10 carbon atoms.
It is necessary to use the following hydrocarbon compounds. That is, in the above-mentioned hydrocarbon compound, if the number of hydroxyl groups is less than 2, the film-forming property will be lost, and if it is 4 or more, gel will be formed and coating will be impossible. Further, when the carbon number is 11 or more, it dissolves or swells in the solvent of the varnish or the styrene monomer, and the coating film and the varnish easily adhere.

As the above-mentioned hydrocarbon compound (component A), glycerin, trimethylolpropane, 1,2,6
-Hexanetriol and the like. These may be used alone or in combination. In the above-mentioned hydrocarbon compound, if the number of hydroxyl groups is less than 2, the film forming property is absent, and if it is 4 or more, a gel occurs and coating cannot be performed. Furthermore, carbon number is 1
This is because if the ratio is 1 or more, the varnish adheres to the thinner or the styrene monomer of the varnish or is swollen.

As the above diisocyanate, 4,4 '
-Diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate and the like can be used, and these can be used alone or in combination.

The blending ratio of the specific hydrocarbon compound (component A) and diisocyanate is the ratio (OH / NCO) of OH in component A and NCO in diisocyanate.
It is necessary to set it to be 1.5 / 1 or more. That is, when the value is less than the above OH / NCO value, a gel is formed at the stage of the synthesis reaction and the solution does not become a solution.

Examples of the organic solvent include dioxane, acetone, methanol, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, ethanol and the like. These may be used alone or in combination. Among the above organic solvents, it is preferable to use a polar solvent in which at least one has an SP (solubility parameter) value of 9 or more. That is, if the SP value is less than 9, the above-mentioned specific urethane resin tends to be insoluble or the urethane resin tends to separate over time.

The terminal protective film forming composition of the present invention is obtained, for example, as follows. That is, it can be obtained by preparing a urethane resin by mixing the specific hydrocarbon compound (component A) and diisocyanate in a specific proportion in an organic solvent and reacting them.

A reaction catalyst is preferably used in the reaction for producing the urethane resin. As the reaction catalyst,
Examples thereof include dibutyltin dilaurate (DBTL), cobalt naphthenate, triethylamine, dibutyltin oxide and the like.

The amount of the organic solvent blended is 20 to 9 based on the total weight.
It is preferably set in the range of 5% by weight. That is,
If the thickness is out of the above range, the coating thickness tends to be too thin or the viscosity tends to be high, so that the coating operation tends to be difficult.

The composition for forming a terminal protective film thus obtained is used as follows. First, a terminal 1 of an electric device such as a transformer as shown in FIG. 1 (see FIG. 2)
This terminal protective film forming composition is applied to the entire surface of the above using a brush, a dispenser or the like, and is dried at room temperature or by utilizing preheating during varnish treatment of the coil. In the figure, 2 is a coil and 3 is a core. Then, as shown in FIG. 3, a protective film 4 is formed on the entire surface of the terminal 1. After that, the electric device is dipped in a bath of impregnated varnish such as unsaturated polyester varnish to remove excess drops, and then the varnish is dried and hardened, and as shown in FIG.
To form. At this time, the protective film 4 does not dissolve in the varnish and does not melt and flow out when the varnish is dried and cured. Then, the connection terminal 1 is heated by using a soldering iron or the like for solder connection or solder application, and brought into contact with high-temperature molten solder. At this time, as shown in FIG.
The protective film 4 formed on the inner side of the is decomposed, the varnish film 5 is pushed away, and the flux produced by the glycol produced by the decomposition of the protective film 4 is obtained. Then, the solder 6 is attached to the terminal 1 so that the terminal 1 is electrically connected.

[0019]

INDUSTRIAL APPLICABILITY As described above, the composition for forming a terminal protective film of the present invention specifies a hydrocarbon compound (component A) having three hydroxyl groups and having 10 or less carbon atoms and diisocyanate. It contains a urethane resin obtained by reacting in a proportion and an organic solvent. For this reason, when this is applied to the terminals to form a protective film, the protective film protects the terminal portion from the cured product of electrical insulating varnish, and during solder connection, the protective film is removed together with the varnish due to the solder connection temperature. And solder connection can be easily performed. Therefore, there is no need to go through the process of removing the varnish,
Workability is improved.

Next, examples will be described together with comparative examples.

[0021]

Example 1 In a 300 ml three-necked flask equipped with a cooling condenser, a thermometer and a stirrer, 36.5 g of glycerin was added.
g, 50 g of 4,4'-methylene diisocyanate,
86.8 g of dioxane was charged, and 0.05 g of dibutyltin dilaurate (DBTL) was added as a reaction catalyst. Then, when the reaction was carried out at 30 to 40 ° C. for 5 hours, the absorption of NCO had disappeared by infrared absorption (IR) measurement, and a viscous urethane resin solution was obtained.

This urethane resin solution was applied to tin-plated terminals of a small power transformer and then naturally dried for 60 minutes, whereby a protective film was formed on the terminals. Then, this transformer was dipped in a styrene-based unsaturated polyester varnish for 1 minute, after dropping for 10 minutes, cured at 120 ° C. for 2 hours. Then, the coil was cooled, and the terminal was soldered to a lead wire using a soldering iron heated to 360 ° C.
As a result, the protective film was decomposed, the cured film of the varnish adhering to the surface of the protective film was also removed, and the solder was wetted on the terminal, so that the connection with the lead wire was made possible and conduction was established.

[0023]

Example 2 The same reactor as in Example 1 was used, in which 64.3 g of trimethylolpropane, 69.6 g of tolylene diisocyanate, and 133.9 g of dioxane were used.
Was charged, and 0.07 g of DBTL was added as a reaction catalyst. Then, when the reaction was carried out at 30 to 40 ° C. for 10 hours, absorption of NCO disappeared by IR measurement, and a viscous urethane resin solution was obtained.

Using this urethane resin solution, Example 1
As a result of performing the same operation as in 3,
Completed in seconds. At that time, the protective film was decomposed, the cured film of the varnish adhering to the surface of the protective film was also removed, and the solder was wetted on the terminal, so that the connection with the lead wire was made possible and conduction was established.

[0025]

Comparative Example 1 16.6 g of glycerin, 50 g of 4,4'-methylene diisocyanate and 86.8 of dioxane.
g was used. Other than that, the same operation as in Example 1 was performed, and as a result, the solution lost its fluidity after 3 hours, and the intended solution could not be obtained.

[0026]

Comparative Example 2 30.4 g of propylene glycol was used instead of glycerin. A urethane resin solution was obtained in the same manner as in Example 1 except for the above.

Then, using the above urethane resin solution,
The same operation as in Example 1 was performed. As a result, the protective film melted and flowed out when the varnish was heated, and the varnish adhered to the terminals, making solder connection impossible.

[0028]

Comparative Example 3 1,4-butanediol was used instead of glycerin. A urethane resin solution was obtained in the same manner as in Example 1 except for the above.

Then, using the above urethane resin solution,
The same operation as in Example 1 was performed. As a result, the protective film melted and flowed out when the varnish was heated, and the varnish adhered to the terminals, making solder connection impossible.

[Brief description of drawings]

FIG. 1 is a perspective view showing a transformer.

FIG. 2 is a perspective view of relevant parts showing terminals provided on a coil.

FIG. 3 is a cross-sectional view showing the terminal with a protective film formed thereon.

FIG. 4 is a cross-sectional view showing the terminal in a state where a varnish film is further formed on the surface of the protective film.

FIG. 5 is a cross-sectional view showing a state in which a terminal having a two-layer film formed thereon is soldered.

Claims (2)

[Claims] 1. A composition for forming a terminal protective film, comprising a urethane resin obtained by reacting an organic solvent with the following component (A) and diisocyanate, wherein the compounding ratio of the component (A) and diisocyanate is: , The ratio (OH / NCO) of OH in component (A) to NCO in diisocyanate
A composition for forming a terminal protective film, which is set to 1.5 / 1 or more. (A) A hydrocarbon compound having 3 hydroxyl groups and having 10 or less carbon atoms. 2. The composition for forming a terminal protective film according to claim 1, wherein at least one of the organic solvents is a polar solvent having an SP value of 9 or more.