JPH0292951A - Resin composition for self-fusible electric wire - Google Patents

Abstract

PURPOSE:To obtain the title composition outstanding in workability in its coating and capable of giving films of high heat resistance by blending a resin prepared by condensation of both acetaldehyde and furfural with polyvinyl alcohol. CONSTITUTION:The objective composition can be obtained by blending a polyvinyl acetal resin prepared by condensation between polyvinyl alcohol and at least two kinds of aldehydes, i.e., acetaldehyde and furfural. The weight ratio of the vinyl acetalized fraction produced by acetalization by acetaldehyde and furfural in said resin is pref. (3:1)-(40:1), esp. (3:1)-(20:1).

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a resin composition for self-fusing electric wires containing polyvinyl acecool resin, which particularly has excellent workability during application and heat resistance. The present invention relates to a resin composition for self-fusing electric wires that provides a coating with excellent properties.

(Prior art) Self-fusing electric wires are created by applying a resin composition to enameled electric wires and drying them. This self-fusing electric wire is formed into the shape of a coil for electrical equipment, communication equipment, etc., and then heated. This fuses the wires together.

As conventional resin compositions for self-fusing electric wires, those based on polyvinyl formal, polyvinyl butyral, polyester, polyamideimide, etc. are mainly used.

(Problems to be Solved by the Invention) However, both polyvinyl formal and polyvinyl butyral resin compositions have poor heat resistance in practical use, especially for applications that require heat resistance such as compressors and high-power motors. cannot be used for

Furthermore, although polyamide-imide and polyimide-based resin compositions have heat resistance, these resin compositions have poor fluidity, resulting in poor workability when applying the resin composition to enamelled electric wires. However, there is a drawback in that a particularly high temperature is required in the fusing step after applying the resin composition to the enameled electric wire. Furthermore, as pointed out in Japanese Patent Publication No. 62-54144, these resin compositions are usually cured by a condensation reaction, so condensation products such as water are volatilized during the condensation reaction. However, there was a drawback that the appearance of the film was significantly deteriorated.

The present invention is intended to solve the above-mentioned drawbacks, and an object thereof is to provide a resin composition for self-fusing electric wires that has excellent workability during application and excellent heat resistance. Another object of the present invention is to provide a resin composition for self-fusing electric wires that does not require particularly high temperatures in the fusing process and does not impair the appearance of the formed coating.

(Means for Solving the Problems) The present invention provides a method for forming a coating on a self-welding wire by blending a polyvinyl acetal resin obtained by condensing at least two aldehyde components, acetaldehyde and furfural, with polyvinyl alcohol. When a resin composition is applied to an enameled electric wire and dried, it is easy to flow and has excellent coating properties, and when the self-fusing electric wire obtained by drying is formed into a coil shape and the wires are heated and fused together. The present invention was completed based on the knowledge that polyvinyl acecool resin itself cures by self-crosslinking, and thus a film with excellent heat resistance can be obtained.

That is, the resin composition for self-fusing electric wires of the present invention contains a polyvinyl acetal resin obtained by condensing at least two aldehydes, acetaldehyde and furfural, with polyvinyl alcohol, thereby achieving the above object. be done.

In the present invention, at least two kinds of aldehydes, furfural and acetaldehyde, are used and these aldehydes are condensed with polyvinyl alcohol to obtain a polyvinyl acetal resin.

The vinyl acecooled portion acetalized by these two types of aldehydes is preferably 65% by weight or more based on the total amount of the polyvinyl acecooled resin.

When the vinyl acecooled portion is much less than 65% by weight based on the total amount of the polyvinyl acecool resin, heat resistance tends to decrease. Further, this vinyl acecooled portion may be vinyl acetalized with another aldehyde in addition to the above-mentioned two types of aldehydes, furfural and acetaldehyde. If other aldehydes are used in an amount exceeding 15% by weight of the total amount of the vinyl acetalized moiety, the crosslinking reaction, especially during the fusion of the furfural ring, may be inhibited.
Since there is a problem that the acetalization reaction of furfural itself is difficult to proceed, it is preferable to use less than 15% by weight of the other aldehyde based on the total amount of the vinyl acetalization portion. As other aldehydes, various commonly known aldehydes are widely used, such as formaldehyde, boropionaldehyde, butyraldehyde, 2-ethylbutyraldehyde, 2-ethylhexylaldehyde, glutaraldehyde, cyclohexylaldehyde, benzaldehyde, phenyl Examples include aldehydes.

The ratio of the vinyl acetalized moiety acetalized by the acetaldehyde and furfural is preferably 3:1 to 40:1, more preferably 3:1 to 20:1, in terms of weight percent of the vinyl acetal moiety. If the ratio of parts is too high than the above range,
After applying the obtained resin composition to an enameled electric wire and drying it,
When the wires are fused together by heating, the hardening progresses too much, and the formed film tends to bend and its flexibility decreases.

On the other hand, if the ratio of the acetalized portion by furfural is too lower than the above range, the self-crosslinking reaction by furfural will not proceed effectively, and the heat resistance of the film will tend to decrease.

The degree of polymerization of the polyvinyl alcohol used in the present invention is 3
00 or more is preferable. If the degree of polymerization of polyvinyl alcohol is less than 300, the strength of the resin coating after heat fusion will be weak and it will be difficult to use.

Next, a method for producing polyvinyl acecool resin will be explained. Add polyvinyl alcohol to water and dissolve completely.
After adding a catalyst such as an acid to this solution, furfural and acetaldehyde are added to carry out an acetalization reaction. The order in which furfural and acetaldehyde are added is not limited. For example, furfural may be added to the solution first to perform the acetalization reaction, and then acetaldehyde may be added, or conversely, acetaldehyde may be added to the solution first and the acetalization reaction is performed, and then the acetalization reaction is performed. Furfural may be added, or furfural and acetaldehyde may be added simultaneously to the solution to carry out the acetalization reaction. The reaction temperature is preferably about 0 to 50°C, more preferably 5 to 20'C. A colorless powder is precipitated by this acetalization reaction. Then,
After the reaction system is maintained at a constant temperature for a predetermined period of time, it is neutralized and washed with water to remove the catalyst and unreacted aldehyde, and then dried to obtain a polyvinyl acetal resin. The amount of acetyl groups contained in the polyvinyl alcohol of the present invention is not particularly limited, but in order to increase heat resistance, it is usually 0.
．． Those having 5 to 12 mol % of vinyl acetate groups are preferably used.

A self-fusing electric wire resin composition is obtained by blending the polyvinyl acecool resin thus produced. Polyvinyl acecool resin may be used alone or in combination with other thermoplastic resins or thermosetting resins. Examples of the thermosetting resin include urea formaldehyde condensates, melamine formaldehyde condensates, phenol formaldehyde condensates, and phenolacetaldehyde condensates, and these may be used alone or in combination. In particular, as a preferable thermosetting resin, phenoxy resin (
For example, a condensation polymer of epichlorohydrin and bisphenol A) can be cited, and by using this phenoxy resin in combination, the strength of the coating can be particularly improved when used as a fused wire. In addition, the resin composition for self-fusing electric wires includes solvents such as cyclohexane and furfural, colorants,
Additives such as fillers and stabilizers may be added. This resin composition is applied to an enameled electric wire and then dried to produce a self-fused electric wire having a coating on its surface. This self-fusing electric wire is formed into a coil shape, and the coatings are self-fused to each other by heating.

By blending polyvinyl acetal resin obtained by condensing two types of aldehydes, acetaldehyde and furfural, with polyvinyl alcohol, we have created a resin composition for self-fusing wires that has excellent workability and heat resistance during application. Obtainable. In other words, by bonding the self-crosslinking aldehyde called furfural to polyvinyl alcohol through an acetalization reaction to form a polyvinyl acetal resin, the furfural rings can be bonded to each other when the resin composition is heated, resulting in crosslinking. This allows the resin composition to be cured. Since the crosslinking in this case is an addition reaction, there is no volatilization of water, etc., which occurs during a condensation reaction, and the appearance of the film is not impaired.

Further, by using acetaldehyde as the aldehyde used in the acetalization reaction together with furfural, flexibility can be imparted to the formed film, and the heat resistance does not decrease significantly. That is, as mentioned above, the film formed by crosslinking polyvinyl acecool resin obtained by acetalization using only furfural as the aldehyde is very brittle, so by using acetaldehyde in combination, the film becomes flexible. It is given gender. Here, formaldehyde, acetaldehyde, butyraldehyde, etc. can be considered as aldehydes to be used in combination with furfural. By the way, when comparing polyvinyl acetoacetal resin obtained by condensing acetaldehyde and polyvinyl alcohol with °butyral resin obtained by condensing butyraldehyde and polyvinyl alcohol, the glass transition temperature of polyvinyl acetoacetal resin is that of butyral. As can be seen from the fact that the glass transition temperature of the resin is 30 to 50°C higher, the use of acetaldehyde yields a resin with superior heat resistance compared to the use of butyraldehyde. By doing so, the molecular structure of the polyvinyl acecool resin is balanced between the acetalized part by furfural and the acetalized part by acetaldehyde, and the above-mentioned crosslinking by the furfural ring can be effectively promoted. Furthermore, when acetalization is performed using an aldehyde that is bulkier than acetaldehyde, such as butyraldehyde, crosslinking through the furfural ring is difficult to proceed.

On the other hand, when formaldehyde, which is a smaller aldehyde, is used, contrary to the above, cross-linking by the furfural ring proceeds quickly, but formaldehyde itself tends to undergo formalization between molecules during the acetalization reaction. This is undesirable because gelation occurs when the resulting resin is dissolved in a solvent, and fluidity is impaired when the resin composition is applied.

Furthermore, in the present invention, by using acetaldehyde, it is possible to obtain the above-mentioned resin composition for self-fusing electric wires with excellent workability and heat resistance, and in addition, during the production of polyvinyl acecool resin, acetalization is possible. Furfural can be bound without any problem during the reaction. In other words, when performing an acetalization reaction using an aldehyde with a long alkyl group such as butyraldehyde, furfural is an aldehyde with a very bulky molecular structure, so it is difficult to combine during the acetalization reaction. It is. This tendency shows that even if furfural is added first to complete the acetalization reaction by furfural, and then an aldehyde with a long alkyl group such as butyraldehyde is added, furfural will undergo a reversible deacetalization reaction and the same reaction will occur. The result is

(Example) The present invention will be explained in detail below based on examples.

Fruit 1111 Preparation of polyvinyl acecool resin 2630 g of pure water was placed in the separable flask of 51, and 3400 g of polyvinyl alcohol [polymerization degree 55o (number average molecular weight 35,000), saponification degree 98.0 mol% was added. Completely dissolved. The temperature of this solution was maintained at 25° C., 695 g of 35% by weight hydrochloric acid was added thereto, 120 g of furfural was added, the temperature was adjusted to 12° C., and 155 g of acetaldehyde was appropriately added to precipitate a colorless powder. Next, the reaction system was brought to 45° C., maintained at this temperature for 4 hours, neutralized, washed with water to remove the catalyst and unreacted aldehyde, and then dried to obtain a polyvinyl acecool resin. The degree of acetalization of this polyvinyl acetal resin was 73.2 mol% (77.7% by weight). Further, the residual acetyl group was 1.9 mol%.

Preparation of self-fusing electric wire paint 90.0 parts by weight of the polyvinyl acecool resin obtained above and 1000 parts by weight of phenol acetaldehyde condensate were dissolved in 510 parts by weight of cyclohexane to form a paint. Next, the obtained self-fusing electric wire paint was applied onto a 1 mm diameter mild steel wire using a baking machine with an oven length of 4 m under conditions of an upper temperature of 270°C and a line speed of 5 m/min, and was dried to form a coating. A self-welding wire with a layer thickness of 0.024 mm was obtained.

Polyvinyl acecool resin obtained in Example 1: 85.0
parts by weight and 15.0 parts by weight of phenoxy resin were dissolved in 510 parts by weight of cyclohexane to form a paint.

Next, the obtained self-fusing electric wire coating material was applied and dried on an annealed copper wire in the same manner as in Example 1 to obtain a coating layer with a thickness of 0.025 mm.
A self-fused electric wire of m was obtained.

Preparation of Polyvinyl Acetal Resin with Main Spots Pour 2,630 g of pure water into the separable flask of Step 52, add 280 g of polyvinyl alcohol [degree of polymerization 800 (number average molecular weight approximately 50,000), degree of saponification 98.0 mol%]. Completely dissolved. The temperature of this solution was maintained at 25°C, 653g of 35% by weight hydrochloric acid was added thereto, 35g of furfural was added, the temperature was adjusted to 10°C, and 141g of acetaldehyde was appropriately added to precipitate a colorless powder. .

Next, the reaction system was brought to 30'C, maintained at this temperature for 4 hours, neutralized, washed with water to remove the catalyst and unreacted aldehyde, and then dried to obtain a polyvinyl acecool resin.

The polyvinyl acetal resin obtained in this way,
A paint was prepared in the same manner as in Example 1. Next, the obtained paint for self-fusing electric wires was applied and dried on annealed copper wires in the same manner as in Example 1 to obtain self-fusing electric wires having a coating layer thickness of 0.024 mm.

In one-ship construction Example 3, 653 g of 35% by weight hydrochloric acid was added to the polyvinyl alcohol solution, 35 g of furfural was added, and the liquid temperature was set at 10°C, and 141 g of acetaldehyde was added.
A polyvinyl acetal resin was obtained in the same manner as in Example 3, except that 10 g of 2-ethylhexylaldehyde was added to precipitate a colorless powder.

The polyvinyl acecool resin obtained in this way,
It was made into a paint in the same manner as in Example 1, and the obtained paint for a self-fusing electric wire was applied and dried on an annealed copper wire in the same manner as in Example 1 to obtain a self-fusing electric wire with a coating layer thickness of 0.024 ws.

In Example 3, 653 g of 35% by weight hydrochloric acid was added to the polyvinyl alcohol solution, 58 g of furfural was added, the liquid temperature was set to 10°C, and 107 g of acetaldehyde was added.
A polyvinyl acecool resin was obtained in the same manner as in Example 3, except that 55 g of butyraldehyde was added to precipitate a colorless powder.

The polyvinyl acetal resin obtained in this way,
A paint was prepared in the same manner as in Example 1, and the obtained paint for a self-fusing electric wire was applied and dried on an annealed copper wire in the same manner as in Example 1 to obtain a self-fusing electric wire having a coating layer thickness of 0.024 mm.

[In Example 3, after adding 653 g of 35% by weight hydrochloric acid to the polyvinyl alcohol solution, 16 g of furfural was added, the liquid temperature was set to 10 ° C, and 200 g of acetaldehyde was added.
A polyvinyl acecool resin was obtained in the same manner as in Example 3, except that a colorless powder was precipitated by adding .

The polyvinyl acecool resin obtained in this way,
A paint was prepared in the same manner as in Example 1, and the obtained paint for a self-fusing electric wire was applied and dried on an annealed copper wire in the same manner as in Example 1 to obtain a self-fusing electric wire having a coating layer thickness of 0.024 mm.

Example 3 except that in Example 3, 653 g of 35% by weight hydrochloric acid was added to the polyvinyl alcohol solution, then 76 g of furfural was added, the liquid temperature was adjusted to 10° C., and 109 g of acetaldehyde was added to precipitate a colorless powder. Polyvinyl acecool resin was obtained in the same manner as in 3.

The polyvinyl acetal resin obtained in this way,
It was made into a paint in the same manner as in Example 1, and the obtained paint for a self-fusing electric wire was applied and dried on a mild steel wire in the same manner as in Example 1 to obtain a self-fusing electric wire having a coating layer thickness of 0.024 mm.

Preparation of Polyvinyl Acecool Resin 2,630 g of pure water was placed in a separable flask in step 52, and 3,400 g of polyvinyl alcohol [polymerization degree 550 (number average molecular weight 35,000), saponification degree 99.0 mol% was added to the flask. and completely dissolved. The temperature of this solution was maintained at 10°C, and 215 g of 35% by weight hydrochloric acid was added thereto, followed by 475 g of furfural to precipitate a colorless powder.

Next, the liquid temperature was raised to 25°C and held for 2 hours, and then raised to 5°C.
The temperature was raised to 0°C and maintained at this temperature for 5 hours to complete the reaction. Thereafter, it was neutralized and washed with water to remove the catalyst and unreacted aldehyde, and then dried to obtain a polyvinyl acecool resin acetalized with furfural.

The polyvinyl acetal resin obtained in this way,
A paint was prepared in the same manner as in Example 1, and the obtained paint for a self-fusing electric wire was applied and dried on an annealed copper wire in the same manner as in Example 1 to obtain a self-fusing electric wire having a coating layer thickness of 0.024 mm.

Comparison 1: Preparation of polyvinyl acetal resin Pour 2630 g of pure water into the separable flask of 51.
To this, 400 g of polyvinyl alcohol [degree of polymerization 550 (number average molecular weight 35,000), degree of saponification 98.0 mol%)
was added and completely dissolved. The temperature of this solution is 12°C.
610 g of 35% by weight hydrochloric acid and 250 g of acetaldehyde were appropriately added to this while cooling to
) to precipitate colorless powder. Next, Example 1
After neutralization and washing with water were performed in the same manner as above to remove the catalyst and unreacted aldehyde, it was dried to obtain a polyvinyl acecool resin.

The polyvinyl acetal resin obtained in this way,
A paint was prepared in the same manner as in Example 1, and the obtained paint for a self-fusing electric wire was applied and dried on an annealed copper wire in the same manner as in Example 1 to obtain a self-fusing electric wire having a coating layer thickness of 0.024 tm.

1 Comparison 1 In Example 1, polyvinyl butyral resin [S-LEC BM-5J manufactured by Tanemizu Chemical Industry Co., Ltd., polymerization degree of about 850 (number average molecular weight 55,000), residual acetyl resin was used instead of polyvinyl acecool resin in Example 1. A self-adhesive wire coating material was prepared in the same manner as in Example 1, except that 1.8 mol% of the base was used, and the baking process on copper wire was also carried out in the same manner. A fused wire was obtained.

Next, the heat resistance and high temperature bending adhesion of the self-bonding wires obtained in each of the above examples and comparative examples were measured, and the results are shown in Tables 1-1 and 1-2.

Note that the high temperature bending adhesion test was conducted as follows.

Create a helical coil by winding the wire around a 6mm diameter round bar at intervals of approximately 75IIfil, and then
After heat treatment at 0° C. for 20 minutes, the bending adhesive strength was measured. The measurement method is to connect the above helical coil to two
The helical coil was installed horizontally between two supporting stands, and a load was applied from the top of the center of the helical coil at a rate of 50 min/min to determine the strength at the time of failure.

(Hereinafter in the margin) (Effects of the Invention) As described above, according to the present invention, a self-fusing electric wire resin composition that is easy to flow and has excellent workability when applied to an enameled electric wire and has excellent heat resistance. It can be used suitably in applications that require heat resistance, such as compressors and high-power motors. In addition, this resin composition
The fusing process does not require particularly high temperatures and does not damage the appearance of the film.

that's all

Claims (1)

[Claims] 1. A resin composition for a self-fusing electric wire, which contains a polyvinyl acetal resin obtained by condensing at least two aldehydes, acetaldehyde and furfural, with polyvinyl alcohol.