JPH068401B2 - Low temperature brazed polyurethane insulated wire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polyurethane insulated wire used for windings of a magnetic head coil, a small precision relay coil, and the like, and particularly inhibits thermal characteristics of a polyurethane insulating film. The present invention relates to a low-temperature brazed polyurethane insulated wire which can be soldered at a low temperature of 300 ° C. or lower without performing.

[Conventional technology]

Polyurethane insulated wire is made by coating and baking polyurethane paint on the conductor, and has the characteristic that it can be soldered as it is without peeling off the urethane film. It is often used for lines.

Generally, polyurethane insulating paint is a thermosetting type one-part paint, which has an oligomer having an activated hydrogen atom having a molecular weight of 1,000 to 5,000, such as polyester, polyether ester, epoxy, etc. as the main component, and as a crosslinking component to this,
For example, 1 mol of trimethylolpropane was reacted with 3 mol of toluene diisocyanate, and the remaining polyisocyanate having blocked isocyanate groups with a blocking agent such as phenol was added, and the main component and the crosslinking agent were dissolved in an organic solvent. It is a thing. In the process of coating and baking this paint on a conductor, when the temperature reaches 150 ° C. or higher, the blocking agent of the blocked polyisocyanate dissociates to generate an isocyanate group. The generated isocyanate group is highly reactive and reacts with coexisting oligomers having activated hydrogen atoms to form urethane bonds between the oligomers, and the three-dimensional network structure has excellent flexibility, adhesion and electrical properties. Form a polyurethane film.

[Problems to be solved by the invention]

The soldering temperature (depolymerization temperature of the urethane film) of polyurethane insulated wire that has been commonly used in the past is 360 to 380.
When a polyurethane insulated wire is immersed in molten solder at a temperature of ℃, the time required for decomposition of the urethane film is 2 to 3 seconds. Further, if the soldering temperature, that is, the thermal decomposition temperature of the urethane film is lowered by more than 50 deg, the thermal characteristics of the urethane film are necessarily lowered significantly. With the recent trend toward lighter, thinner, and smaller electronic components, the mounting density of printed circuit boards has improved, and the emergence of polyurethane ultrafine wires that can be soldered at lower temperatures is strongly desired.

[Means for solving problems]

The present invention aims to significantly reduce the soldering temperature without deteriorating the heat resistance and thermal softening temperature of the polyurethane insulating film by using a material having a characteristic composition for the polyurethane insulating coating and the catalyst added thereto. It was successful.

The present inventors have previously developed a thermosetting one-component polyurethane coating prepared by dissolving a block polyisocyanate and an oligomer having an active hydrogen atom in an organic solvent for the purpose of lowering the baking temperature of the polyurethane coating, and 1.8-diaza- A polyurethane insulating coating containing a bicyclo (5.4.0) undecene-7-organic acid salt and an alkyltin mercaptide compound as a catalyst has been proposed (JP-A-55-73765). By doing so, we were able to achieve the intended purpose for a while. The polyurethane insulated wire coated with this polyurethane paint on the conductor had a high soldering temperature of 380 ° C and a dipping time of 1-2 in the molten solder. Its application to ultra-fine polyurethane insulated wires in seconds was severely limited.

In the present invention, in order to improve these drawbacks, various studies were conducted on a film forming agent and a cross-linking agent, which are the main components of the polyurethane insulating coating, and a catalyst added thereto. As a result, as the film forming agent, a polyester oligomer having a molecular weight of 1,000 to 5,000 synthesized by a dehydration condensation reaction of glycerin or ethylene glycol with terephthalic acid or dimethyl terephthalic acid, and an alcohol-soluble copolymerized polyamide resin as a brazing extender. As a cross-linking agent, the structural formula Using a block polyisocyanate compound represented by,
As a catalyst to be added to a thermosetting type one-component polyurethane coating in which these are dissolved in an organic solvent, 1.8-diaza-bicyclo (5.4.0) undecene-7-organic acid salt and general formula (In the formula, R ″ represents an alkyl group having 1 to 8 carbon atoms) to solve the problem.

The reaction system of polyurethane insulation paint is a two-step reaction,
One is a dissociation reaction of the blocked polyisocyanate compound, which is represented by the following formula (1).

Next, the reaction of the formula (2) is a reaction between the free isocyanate group generated by the reaction of the formula (1) and the polyester oligomer, in other words, a cross-linking reaction between the polyester oligomers, and forms a cross-linked structure of the urethane film. . Furthermore, in this crosslinked network, alcohol-soluble polyamide resin Long molecular chains are entangled with each other to form an interpenetrating network structure.

In the above-mentioned two-step reaction, (1) is a rate-determining reaction, and as a catalyst for promoting this reaction, 1.8-diaza-bicyclo (5.4.0) undecene-7-organic acid salt and the crosslinking reaction of the formula (2) are used. Alkyl tin maleate ester effectively acts as the catalyst. The alkyl tin maleate is represented by the above general formula, and the content as metal tin is generally 10 to 35%.
To some extent, it is industrially widely used as a heat and light stabilizer for polyvinyl chloride blends, and is readily available as an organotin stabilizer.

[Work]

According to the present invention, it is the first catalyst in the rate-determining reaction, which is the first step of the reaction mechanism of polyurethane insulating coating film formation.
The 1.8-diaza-bicyclo (5.4.0) undecene-7-organic acid salt acts, and the dissociation proceeds at a temperature about 50 deg lower than that of the blank to generate a free isocyanate group. Next, in the curing reaction in the second step, by the action of the alkyltin maleate ester which is the second catalyst, the produced isocyanate group immediately reacts with the activated hydrogen atom of the polyester oligomer to form a urethane bond to form an intermolecular bond. Form a crosslinked structure. This means that the curing reaction is completed at a lower temperature in the reaction system to which the catalyst is added.

Most of the polyurethane insulating film of the present invention exhibits a cross-linked structure of polyurethane bond due to the action of the first and second catalysts. The polyurethane bond is thermally decomposed (thermal depolymerization) at a temperature of 300 ° C, and the main reaction of the decomposition is the reverse reaction of the urethane formation reaction. Therefore, the obtained insulating film has low-temperature brazing characteristics. In the reaction system in which these catalysts are not present, side reactions other than urethane bond are likely to occur, and when other bond formation such as puret bond or allophanate bond is formed, low temperature brazing property can no longer be imparted. This is because the former bond type method allows the reaction to proceed much faster than that of the bond generated by the thermal decomposition reaction of the urethane bond and other side reactions.

The reason why the polyester oligomer as the film-forming agent is used in combination with the alcohol-soluble copolyamide resin is that by inserting a polyamide resin having a large molecular weight, it becomes a form in which it intervenes between urethane cross-linking points and a bidirectional interpenetrating network structure is formed. To impart sufficient mechanical strength to the coating, to control the occurrence of side reactions other than urethane bonds during the curing reaction, and to impart the effect as a flow regulator and viscosity regulator to the paint. is there.

The addition amount of the first and second catalysts used in the present invention is
It is limited to 0.1 to 5% with respect to the solid portion of the paint. This is because if the amount added is smaller than this, it is less effective in achieving the intended purpose, and if it exceeds this amount, properties other than solderability are affected.

[Example] A polyurethane insulating paint was prepared with the compounding ratios shown in Table 1.

Conductor diameter 0.1mm
Solderability and other performances of the insulated electric wire coated and baked to two kinds of film thickness on the copper wire were measured. Table 2 shows the characteristic results.

[Advantages of the Invention] The low-temperature brazed polyurethane insulated wire of the present invention has a soldering temperature of 290 to 300 ° C, which is about 50 ° lower than that of a conventional polyurethane wire, as shown in Table 2, and has excellent heat resistance and other characteristics. It is an excellent one. Therefore, it is possible to improve the efficiency of the soldering work and prevent the thermal effect that is received at that time
In particular, when applied to an ultrafine wire with a conductor diameter of 0.03 mm or less, its hardening is great, and the reliability of parts can be greatly improved.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Yoshikawa 300 Oya, Oita, Ueda, Nagano Tokyo Special Electric Cable Co., Ltd. Ueda Factory Examiner Eiwa Kashimoto (56) JP-A-55-73765 (JP, A) JP-A-53-11930 (JP, A) JP-A-61-130377 (JP, A) JP-A-62-30161 (JP, A)

Claims (1)

[Claims] 1. Structural formula A thermosetting type in which three components of a block polyisocyanate compound represented by, a polyester oligomer synthesized by a dehydration condensation reaction of glycerin or ethylene glycol with terephthalic acid or dimethyl terephthalic acid, and an alcohol-soluble copolymerized polyamide resin are dissolved in an organic solvent. 1.8-diaza-bicyclo (5.4.0) undecene-7-as a catalyst for one-component polyurethane paint
Organic acid salt and general formula (In the formula, R ″ represents an alkyl group having 1 to 8 carbon atoms.) Add 0.1 to 5% each of the alkyl tin maleate ester represented by the formula to the fixed part of the paint, and add this on the conductor. A low temperature brazed polyurethane insulated wire characterized by being applied and baked on.