Insulating varnish for enameled wires

 

(57) Abstract:

The invention relates to the production of electrical insulating varnishes for coating of enamel wires and reduces the emission of harmful volatile substances by increasing the solids to increase the mechanical strength and breakdown voltage of insulation, as well as to expand the raw material base. The composition includes liquid or low-melting polyester, epoxy resin, blocked isocyanate, ethylene glycol, glycerol and the catalyst at a certain ratio of components. table 2.

The invention relates to polymer chemistry, in particular the production of heat-resistant insulating varnishes for coating of enamel wires.

Known electrical insulating varnishes based on polyester resins. As well known electrical insulating varnish PE-939 [1], which consists of polyester resin, organic solvents, polybutylene.

The disadvantages of this varnish are low resistance and low dry matter content, which leads to emission of a large volume of harmful volatile substances.

The closest in composition and technical characteristics to offer the varnish is a lacquer UR-9119 [2]. In his thought - blocked isocyanate Surisan BBT and curing catalyst.

Disadvantages varnish UR-9119 are low resistance and mechanical strength of the coating, and low dry matter content and, consequently, a large amount of harmful volatile substances. In addition, to get used in the composition of the locked triisocyanate necessary scarce and expensive components.

The objective of the invention is to reduce emissions of harmful volatile substances by increasing the solids improving the reliability of insulation proudof on its basis by increasing the mechanical strength, as well as the expansion of raw materials.

To solve this problem is proposed varnish, which consists of liquid or low-melting polyester, epoxy, blocked isocyanate, organic solvents, glycol, glycerol and the catalyst in the following ratio, wt.%:

Polyester - 10 - 30

Epoxy - 8 - 30

The blocked isocyanate - 25 - 40

Tricresol - 12 - 16

Solvent - 12 - 16

Ethylene glycol is not more than 3

Glycerin - no more than 2

The curing catalyst is not more than 0.3

about polyester. Polyester interacts with the isocyanate forms a urethane links polymeric coating. It gives elasticity and contributes to the improvement of the mechanical characteristics of the insulation. In addition, the introduction in the composition of this liquid or low-melting polyester reduces the amount of harmful organic solvents in the composition and, therefore, its emission into the atmosphere in the form of volatile substances.

2. The use of epoxy resin. When the interaction of the epoxy resin with the isocyanate formed heat-resistant polyoxazolines. This gives the coating hardness, improves its mechanical and electrical characteristics.

3. The use of glycerin. Glycerin is used as a crosslinking agent, resulting in higher mechanical strength.

4. The use of ethylene glycol. The glycol acts as a chain extension, which leads to the improvement of the effective flowing property, the improvement of physico-mechanical characteristics of the coating.

Comparative analysis of the proposed solution with the prototype revealed the presence of distinctive features, which is associated with the achievement of the claimed technical result.

Thus, the proposed solution meets the criterion of izvestno in the technique. However, in the known solutions are not revealed to the joint application of polyester and epoxy resin in combination with a blocked polyisocyanate, and it is this set of features provides education polyurethanecoated enamel coating-wires and improves the operational reliability of the insulation.

This allows to make a conclusion on compliance of the proposed solution the criteria of the invention "inventive step".

To obtain the proposed composition of the lacquer you can use any liquid or low-melting polyesters, for example polyoxyalkylene. As epoxy compounds applicable to various epoxy resins. As the blocked isocyanate may use any utilized in industry oligomers.

Method for producing electrically insulating varnish.

In a reactor equipped with a stirrer, a thermometer and a shirt, upload a blocked isocyanate, an organic solvent and stirred until complete dissolution within 3 h at 60-80oC. After complete dissolution of the blocked isocyanate in the solvent in the reactor type polyester, epoxy resin, ethylene glycol, glycerol and the catalyst. Then SLAC.

An example of a specific implementation.

In a reactor equipped with a stirrer, a thermometer and a shirt, loaded preliminary ground blocked isocyanate is 29.1 wt.h., tricresol and 14.6 wt.h., solvent and 14.6 wt.h. and stirred for 3 h at 60-80oC until complete dissolution of the blocked isocyanate. After that, the reactor was added polyester PDA-800 - 19.5 wt.h., epoxy resin ED-20 - 19.5 wt. hours, the glycerol - 0.5.h., the glycol - 2 wt.h. and curing catalyst is 0.2 wt.h. and stirred until complete dissolution of the catalyst for 2 h at 60-80oC. the resulting mixture was filtered and got ready enamel-lacquer.

Samples of the modified varnish used for enameling wire on the adopted technology. The wire was tested for compliance with THE 16-705.110-79.

Were investigated varnishes and enamel wires with different ratio of components, including the minimum and maximum values (table. 1). The results of the tests of varnishes and enamel wires are presented in table. 2.

Compared with the prototype of the proposed electrical insulating varnish has the following techno-economic advantages:

- increases the dry residue in 2 times,

- powiaza,

- possible to use oligomers, are utilized in industry, more affordable and cheap compared with the proposed prototype.

Insulating varnish for enameled wires, including polyester, blocked isocyanates, organic solvents tricresol and the solvent and the curing catalyst, characterized in that it contains a liquid or low-melting polyester and additionally includes epoxy resin, ethylene glycol and glycerol in the following ratio, wt.%:

Polyester - 10 - 30

Epoxy - 8 - 30

The blocked isocyanate - 25 - 40

Tricresol - 12 - 16

Solvent - 12 - 16

Ethylene glycol is Not less than 3

Glycerin - No more than 2

The curing catalyst is Not more than 0.3 with

 

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