JP2632336B2 - Polyurethane insulating paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention is a brazed insulated wire which is stable for a long period of time, does not cause turbidity, and has excellent low-temperature brazing properties and good crazing properties. The present invention relates to a polyurethane-based insulating paint suitably used for the production of polyurethane.

(B) Conventional technology Brazing insulated wires are widely used in the fields of the electric and electronic industries because they can be directly soldered without peeling the coating film mechanically or with a chemical.

In this field, when soldering a terminal or the like of an electric or electronic component (a core wire or the like), the effect of the heat causes thermal deterioration of the electric or electronic component or thermal deterioration of a terminal or the like of the electric or electronic component. Sometimes.

For this reason, the soldering temperature of electric and electronic parts is low,
It is preferable to be able to solder in a short time, and from the viewpoint of improving productivity, when coating a core wire such as a coil with a polyurethane-based insulating paint, the winding time of this core wire is short and the winding is deteriorated. None is preferred.

For this reason, a polyurethane-based insulating coating suitable for such an application is desirably a one-pack type, and in order to have a pot life, the isocyanate block body and the polyol, which are stable at room temperature and undergo a reaction by heating, are heated. A thermosetting paint obtained by mixing is desirable.

As an isocyanate monomer used in the isocyanate block, metaphenylene diisocyanate has excellent performance due to the short coating film properties and short curing time, and is being widely used.

Therefore, conventionally, as this polyurethane-based insulating coating, a coating composed of a metaphenylene diisocyanate-based block and a polyol has been proposed and used, but the meta-phenylene diisocyanate-based block is practically reactive, viscous and cured. From the viewpoint of economy and the like, those blocked with a kind of blocking agent selected from phenol, xylenol, cresol and the like are used.

(C) Problems to be Solved by the Invention The polyurethane-based insulating coating is stable in order to obtain an insulating coating having a desired coating structure and excellent characteristics without uniform skin. It must be transparent, uniform, free from turbidity, etc. for at least three months or more, and have a viscosity suitable for the coating method and coating conditions.

However, the polyurethane insulating coating using the metaphenylene diisocyanate-based block may be deteriorated during storage or handling, causing turbidity, causing a problem of thickening, and sometimes causing a batter-like thing. When electrical and electronic parts are coated with a non-uniform polyurethane-based insulating coating that has deteriorated in this way, the surface of the coating becomes rough and microvoids form in the coating, resulting in uneven coating and poor electrical characteristics. There's a problem.

For this reason, this kind of polyurethane insulating paint is actually stored or used under restricted and strict conditions, and there is a problem that its handling requires considerable care.

An object of the present invention is to provide a polyurethane insulating paint which is stable over a long period of time, does not cause turbidity, is economical, and has excellent low-temperature solderability and excellent electrical properties. .

(D) Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, as an isocyanate block component, diphenylmethane diisocyanate or NC containing the same as a main component.
What is obtained by blocking an isocyanate group of an O group-containing prepolymer with a mixed blocking agent consisting of at least two kinds selected from isomers of xylenol and at least one kind selected from isomers of cresol Surprisingly, polyurethane-based coatings that provide an insulating film having excellent properties even at room temperature, that is, without causing turbidity and the like over a long period of time without storage under strict conditions Have been found, and the present invention has been completed.

That is, the polyurethane insulating paint of the present invention comprises (A) diphenylmethane diisocyanate or an isocyanate group of an NCO group-containing prepolymer containing the same as a main component,
Blocking with a mixed blocking agent (A ₁ + A ₂ ) consisting of at least two selected from (A ₁ ) xylenol isomers and at least one selected from (A ₂ ) cresol isomers An isocyanate block,
An insulating paint comprising (B) a polyol and (C) the solvent (A + B), wherein the mixed blocking agent (A ₁ +
A ₂₎ cresol isomers in the content of (A ₂₎ is characterized in that 5 to 50% by weight.

 Hereinafter, the present invention will be described in detail.

Isocyanate block used in the present invention (A)
As for (A) diphenylmethane diisocyanate or an isocyanate group of an NCO group-containing prepolymer containing the same as a main component, at least two kinds selected from isomers of (A ₁ ) xylenol and (A ₂ ) cresol It is obtained by blocking with a mixed blocking agent (A ₁ + A ₂ ) comprising at least one member selected from isomers.

Among the above diphenylmethane diisocyanates, the most preferred are the following structural formulas, And 4,4'-diphenylmethane diisocyanate.

Examples of the NCO group-containing prepolymer containing diphenylmethane diisocyanate as a main component include a reaction product of the diphenylmethane diisocyanate and a polyhydric alcohol.

The polyhydric alcohol is an aliphatic polyhydric alcohol having two or more hydroxyl groups in the molecule, and has a molecular weight of
It is not particularly limited as long as it is 62 to 660,
Specifically, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol,
Hexane glycol, butane glycol, glycerin,
Trimethylolpropane, pentaerythritol and the like.

The most significant feature of the present invention is that, as the isocyanate block (A), the above-mentioned diphenylmethane diisocyanate or the isocyanate group of the NCO group-containing prepolymer containing the same as a main component is selected from the isomers of (A ₁ ) xylenol. It is obtained by blocking with at least two selected members and a mixed blocking agent (A ₁ + A ₂ ) composed of at least one member selected from isomers of (A ₂ ) cresol.

The isomers of the above (A ₁ ) xylenol include 2,3-xylenol, 2,4-xylenol, 2,5-xylenol,
Examples include 2,6-xylenol, 3,4-xylenol or 3,5-xylenol.

Further, as the isomers of the above (A ₂₎ cresol, o- cresol, m- cresol, p- cresol.

And, in the mixed blocking agent (A ₁ + A ₂ ),
The mixing ratio of (A ₁ ) and (A ₂ ) is preferably such that (A ₂ ) is in the range of 5 to 50% by weight, and preferably 10 to 30% by weight based on the whole of (A ₁ + A ₂ ).

In the mixed blocking agent (A ₁ + A ₂ ), (A ₂ ) is 5
If the weight is too small, that is, less than 5%, it becomes a mixed blocking agent containing many xylenol isomers (A ₁ ) having many methyl groups, so that the solubility of the obtained isocyanate block (A) tends to be good. Problem with the pot life of
In other words, it is not preferable that turbidity tends to be generated due to deterioration of crystals during storage or handling due to precipitation. On the other hand, if it exceeds 50% by weight, cresol isomer (A ₂ ) increases, so This is not preferable because the solubility of the obtained isocyanate block body (A) becomes poor and it becomes difficult to obtain a uniform paint.

Further, the isocyanate group of the NCO group-containing prepolymer obtained by reacting diphenylmethane diisocyanate blocked with the above-mentioned mixed blocking agent (A ₁ + A ₂ ) with diphenylmethane diisocyanate and a polyhydric alcohol, for example, trimethylolpropane, is used as the above. Comparing those blocked with the mixed blocking agent (A ₁ + A ₂ ), those having blocked isocyanate groups of this high molecular weight type NCO group-containing prepolymer tend to have better pot life.

In the present invention, the mixed blocking agent (A ₁ +
The reason for using A ₂ ) is to prevent deterioration of the paint, that is, crystallization, by using many isomers.

Another reason for containing the cresol isomer (A ₂ ) is that the isocyanate block (A)
This is because in the manufacturing process, the solidification in the winter season is prevented, the energy for heating is reduced, and it is more economical and excellent in handling.

In the mixed blocking agent (A ₁ + A ₂ ) used in the present invention, phenols such as phenol, ethyl phenol and trimethyl phenol, ε
Lactams such as caprolactam, amides, oximes such as ketone oximes, β-ketobutyric acid (CH ₃ COCH ₂ COO
Known blocking agents such as H), alcohols, glycols, acetylacetone, pyrrolidone, and DMF (dimethylformamide) can be used in combination.

When the compounding ratio of this blocking agent exceeds 50% by weight,
It is not preferable because an insulating coating film may deteriorate the surface condition of the coating film.

In the present invention, diphenylmethane diisocyanate or an isocyanate group of an NCO group-containing prepolymer containing the same as a main component is mixed with the mixed blocking agent (A ₁
+ A ₂ ) does not require a special technique as a method of blocking, and can be achieved by a conventional method.

At this time, a catalyst can be optionally used, and the amount of the catalyst is 0.1 to 10 parts by weight per 100 parts by weight of the isocyanate block body (A).

Examples of the catalyst include a metal carboxylate, an amine (such as a tertiary amine), and a phenol.
Specifically, for example, naphthenic acid, octenoic acid, versatic acid, salicylic acid, zinc salt such as acetic acid, iron salt, copper salt, lead salt, manganese salt, cobalt salt, tin salt, cesium salt, aluminum salt, zirconium salt, 1.8 And diaza-bicyclo (5.4.0) undecene-7,2,4.6-tris (dimethylaminomethyl) phenol.

In addition, the use of this type of catalyst plays a role in lowering the brazing temperature of the obtained insulated wire because the catalyst remains in the finally obtained coating composition.

In the present invention, diphenylmethane diisocyanate is used. When an NCO group-containing prepolymer containing diphenylmethane diisocyanate as a main component is used instead, a range of 50% by weight or less based on the diphenylmethane diisocyanate monomer constituting the prepolymer is used. Known aromatic and aliphatic isocyanates such as toluylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, and water-soluble isocyanates can be used in combination.

The polyol (B) used in the present invention generally has an average molecular weight of 200 to 10,000 and a hydroxyl value of about 200 to 700, and those having hydroxyl groups at both molecular terminals are preferably used.

Examples of the polyol (B) include a polyester polyol and a polyether polyol. These include isophthalic acid, terephthalic acid, orthophthalic acid, phthalic anhydride, aromatic imidic acid, aromatic amic acid, trimellitic acid, and anhydride. An aromatic polybasic acid such as trimellitic acid and an aliphatic polyhydric alcohol such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, hexane glycol, butane glycol, glycerin, trimethylolpropane, and pentaerythritol, optionally with succinic acid , Adipic acid, sebacic acid, itaconic acid, can be obtained by a conventional method in combination with an aliphatic polybasic acid such as glutaric acid. In the present invention, the starting materials of the aromatic compounds in the starting materials are all Quantitative proportion is 2 It is preferable to be about 0 to 70% by weight.

Examples of commercially available polyester polyols or polyether polyols having an aromatic ring include Nipporan 2006 manufactured by Nippon Polyurethane Co., and Desmohen 60 manufactured by Bayer Co.
0, 800, F-951, 550, 1025 and the like.

In the present invention, a lactone polyol having an average molecular weight of 200 to 10,000 and a hydroxyl value of about 50 to 700, which is obtained by ring-opening polymerization of lactone as a polyol, can also be used (Japanese Patent Publication No. 34-5294, JP-A-34-5294, This is described in, for example, JP-A-55-104315).

In the present invention, the isocyanate block (A) and the polyol (B) are compounded in an amount of 0.4 to 2.0 equivalents, preferably 0.9 to 1.1 equivalents, and a required amount of a curing accelerator for 1 equivalent of the isocyanate group of the (A). A catalyst is added, and an appropriate amount of the solvent (A + B) is further added.
It can be obtained by setting the solid content to 30 to 50% by weight.

At this time, if necessary, an appropriate amount of an additive such as an antioxidant, an ultraviolet light-resistant agent, an appearance improving agent, or a dye may be added.

In the present invention, the reason for adding 0.4 to 2.0 equivalents of hydroxyl group per equivalent of isocyanate group is that 0.4 equivalent or less,
The resulting insulated electric and electronic parts have reduced wear resistance, while
This is because, when added in an amount of 2.0 equivalents or more, the crazing property of the insulated electric / electronic component becomes inferior.

The amount of the above-mentioned curing promoting catalyst to be added is preferably 0.1 to 10 parts by weight per 100 parts by weight of the isocyanate block (A). This is because the performance tends to deteriorate, and when the content is 10 parts by weight or more, the thermal degradation characteristics of the obtained insulated electric / electronic component can be reduced.

Examples of the curing acceleration catalyst include metal carboxylate, amines and phenols.Specifically, naphthenic acid, octenoic acid, zinc salts such as versatic acid,
Iron salt, copper salt, manganese salt, cobalt salt, tin salt, 1.8-
Diazabicyclo (5.4.0) undecene-7,2.4.6
Known ones such as tris (dimethylaminomethyl) phenol can be exemplified.

The solvent of the above (A + B) is not particularly limited as long as it is used for a polyurethane paint, and specifically, phenols, glycol ethers,
Naphthas and carbitols may be used, and these may be used alone or in combination of two or more.

(E) Action The polyurethane-based insulating paint of the present invention is an isocyanate block obtained by blocking diphenylmethane diisocyanate or an isocyanate group of an NCO group-containing prepolymer containing the same as a main component with a specific mixed blocking agent (A ₁ + A ₂ ). It is stable and hardly crystallizes during storage, and has the effect of improving the pot life of the paint without causing deterioration and turbidity.

Further, in the present invention, a mixed blocking agent containing a cresol isomer is used as the isocyanate blocking agent. Prevents coagulation and requires less energy to heat,
In addition to being more economical and excellent in handleability, the use of the obtained paint has an effect of obtaining an insulating coating film having excellent electrical properties.

(F) Example Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

Examples 1-4 The compositions, viscosities and pot lives of the polyurethane insulating coatings of Examples 1-4 are shown in Table 2.

In Table 2, in the isocyanate block body (I),
(II) was obtained by the following method.

(I). Method for synthesizing diphenylmethane diisocyanate block (A) [isocyanate block (I)] 4,4'-diphenylmethane diisocyanate 125 in a four-necked flask equipped with a thermometer, a stirrer, and a condenser.
g and 255 g of the mixed blocking agent shown in Table 1 are added and dissolved while gradually raising the temperature.

In this case, the contents are completely dissolved at a temperature of 50-60 ° C,
Furthermore, when the temperature is raised and the temperature rises to 70 ° C., the reaction starts and heat is generated, but the reaction is continued as it is.

The mixture was allowed to react at a temperature of about 150 ° C. for 1 to 3 hours. After confirming that free isocyanate groups had disappeared, the mixture was cooled. When the temperature reached 90 to 100 ° C., a diluting solvent [carbitol / naphtha = 50 / 50 (weight ratio)] 380 g. The product thus obtained was designated as an isocyanate block (I).

(II). Method for synthesizing NCO group-containing prepolymer block (A) [isocyanate block (II)] 4 equipped with thermometer, stirrer, cooling tube and dropping funnel
125 g of 4,4'-diphenylmethane diisocyanate is added to a one-necked flask, and 63 g of diethyl glycol dimethyl ether is further added as a reaction solvent, followed by heating and melting.

Then, 22.3 g of trimethylolpropane was added thereto, and the mixture was reacted at a reaction temperature of 60 to 150 ° C. for 2 hours to obtain 4,4 mol / mol of trimethylolpropane.
210.3 g of an NCO group-containing prepolymer to which 4'-diphenylmethane diisocyanate was added in a molar ratio of 3 times was obtained.

Next, 210.3 g of the NCO group-containing prepolymer was added to the first
63 g of the mixed blocking agent shown in the table is added, and these are dissolved while gradually raising the temperature.

In this case, the contents are completely dissolved at room temperature, and when the temperature is raised to 50 ° C., the reaction starts and the exotherm starts.

The reaction was carried out at a temperature of about 50 to 130 ° C for 2 to 3 hours, and after confirming that the free isocyanate groups had disappeared, the mixture was cooled,
When the temperature reaches 50 to 60 ° C., 147.3 g of a diluting solvent [carbitol / naphtha = 50/50 (weight ratio)] is added. The obtained product is an isocyanate block (II)
And

Using the above isocyanate block bodies (I) and (II), Nipporan 2006 (hydroxyl value: 380, manufactured by Nippon Polyurethane Co., Ltd.) and octensan zinc were used as polyols.
In addition to the proportions shown in the table, a polyurethane insulating coating of the present invention having a resin content of 35% by weight was obtained (Examples 1 to 4).

Comparative Examples 1 to 3 In the Examples, a single blocking agent was used instead of the mixed blocking agent, that is, 3,5-xylenol (Comparative Example 1), 2,4-xylenol (Comparative Example 2), o-cresol ( In Comparative Example 3), a product obtained in the same manner as in Example 1 was used except that an isocyanate blocked product blocked in the same manner as in Example 1 was used.

The polyurethane insulating paint of each of the above Examples and Comparative Examples was applied to a 0.2 mmφ copper wire, and the wire speed was 65 m / min and the furnace temperature was 360.
The resultant was baked by passing through a furnace having a baking furnace length of 2 m at 6 ° C six times to obtain a brazed electric wire.

 The obtained brazed electric wire was evaluated based on JIS C 3211.

 Table 3 shows the evaluation results.

From the results shown in Table 2, it is recognized that the polyurethane insulating paint of the present invention is more stable over a long period of time than the comparative example.

Also, from the results shown in Table 3, the brazed wire obtained by using the examples has no crazing property with no generation of microvoids and the like, and has a better appearance than the one using the comparative example. Moreover, it is recognized that there is no pinhole and the dielectric breakdown voltage is high.

Furthermore, from the results shown in Table 3, the soldering could be performed at a low temperature and in a short time, and good results were obtained in the evaluation of thermal deterioration.

(G) Effects of the Invention The present invention has the above-described structure, and is a method for producing an insulated electric / electronic component that is stable over a long period of time, does not generate turbidity, has excellent low-temperature soldering properties, and has excellent crazing properties. This has the effect of being suitably used for

In addition, the use of the polyurethane insulating paint of the present invention has an effect of obtaining an insulating film having a desired coating film structure and having excellent electrical properties without a rough surface.

In blocking diisocyanate groups of diphenylmethane diisocyanate or an NCO group-containing prepolymer containing the same as a main component, 2,3-xylenol, 2,4
Xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol or at least two xylenol isomers selected from 3,5-xylenol and o-cresol, m-cresol or p-cresol When a mixed blocking agent comprising at least one selected cresol isomer is used, it is stable, hardly crystallized during storage, and has an effect of improving the pot life of the paint without causing deterioration and turbidity. is there.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Eiji Aso, Inventor 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nichidenki Kogyo Co., Ltd. (56) References JP-A-60-179468 (JP, A) JP-A-52-114622 (JP, A) JP-A-58-179276 (JP, A)

Claims (3)

(57) [Claims] The method according to claim 1 (A) The isocyanate groups of the NCO-containing prepolymers of diphenylmethane diisocyanate or mainly of this, at least two selected from among isomers of (A ₁₎ xylenol, (A ₂₎ An isocyanate block obtained by blocking with at least one mixed blocking agent (A ₁ + A ₂ ) selected from cresol isomers, (B) a polyol and (C) the (A +
An insulating paint comprising the solvent of B), wherein the content of the cresol isomer (A ₂ ) in the mixed blocking agent (A ₁ + A ₂ ) is 5 to 50% by weight. 2. The method according to claim 1, wherein the isomer of xylenol is 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol or 3,5-xylenol. 2. The polyurethane-based insulating coating according to item 1. 3. An isomer of cresol is o-cresol, m
The polyurethane insulating paint according to claim 1 or 2, which is -cresol or p-cresol.