JPH061951A - Heat-resistant coating - Google Patents

Abstract

PURPOSE:To provide the subject coating capable of giving nonsticky coating film excellent in heat resistance and flexibility and good in dryability through its application on a metallic base material followed by baking. CONSTITUTION:The objective coating can be obtained by incorporating (A) a coating containing as binder an organometallic polymer such as polysiloxane or polyborosiloxane with (B) 0.5-50 pts.wt., per 100 pts.wt. of the resin component of the above polymer, of an isocyanate compound such as tolylene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI). Owing to the incorporation of the component B, the presence of residual unreacted OH groups in the resin molecules in the resultant coating film can be avoided and also linear C-C bonds introduced into the molecules with three-dimensional network structure, leading to avoiding stickiness and improving flexibility of the resultant coating films.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat resistant paint, and more particularly to a paint for forming a heat resistant insulating coating film on an electric conductor or a steel plate.

[0002]

2. Description of the Related Art In recent years, binders for heat-resistant paints
As such, an organometallic polymer such as polysiloxane, polyborosiloxane, or polytitanosiloxane whose main chain is a metal element such as Si, Ti, or B and O or N is used.

However, in a coating material containing such an organometallic polymer, the baked coating film has a high heat resistance of 500 ° C. or higher due to the thermal stability of the polymer, but on the other hand, for the following reasons, alkyd resin and urethane are used. It has a drawback that it is poor in flexibility as compared with a usual organic paint using a resin, an acrylic resin or the like as a binder. That is,
An organic resin such as an alkyd resin has a linear structure with a small number of branches, whereas the organometallic polymer has a network structure with many branches. In addition, organometallic polymers such as polysiloxane (silicone resin)
In the case of baking, as shown in the following chemical formula 1, a dehydration condensation reaction of terminal OH groups progresses to form a huge three-dimensional network structure. For these reasons, it is considered that the degree of freedom of the molecule decreases and the flexibility of the coating film deteriorates. In Chemical Formula 1, R represents a monovalent organic group such as a methyl group.

[0004]

[Chemical 1] Therefore, conventionally, in heat-resistant paints containing organometallic polymers, in order to improve the flexibility of the coating film, baking is performed at a low temperature for a short time, and a method of suppressing the condensation reaction between the terminal OH groups is performed. ing.

[0005]

However, in such a method, the flexibility of the coating film is secured, but a large amount of uncrosslinked molecules, that is, unreacted OH groups remain in the coating film. Therefore, there is a problem that not only the surface of the coating film becomes sticky, but also the hardness becomes insufficient and the resistance to organic solvents decreases. In particular, the stickiness of the coating film surface has a large industrial impact, which makes it difficult to manufacture electric wires and coated long plates. That is, in the manufacturing process of electric wires and long coated plates, coating, baking and winding are continuously performed, but if the hardness of the coating film is insufficient and there is stickiness, the coating is not performed during winding. The films or the coating film and other substrates are often adhered to each other, and if they are forcibly peeled off, peeling of the coating film or change in appearance occurs, which is not preferable.

The present invention has been made to solve these problems, and forms a heat-resistant coating film having excellent flexibility, good drying property and non-stickiness by coating and baking on a metal substrate. It is an object of the present invention to provide a heat-resistant paint that can be used.

[0007]

The heat-resistant paint of the present invention comprises:
A bifunctional isocyanate compound is added to a coating material containing an organometallic polymer as a binder.
It is characterized by being mixed in a proportion of 0.5 to 50 parts by weight with respect to parts by weight.

The organometallic polymer used in the present invention has a main chain composed of a metal element such as Si, Ti and B and a non-metal element such as O and N, and has a side chain containing an organic group such as a methyl group and a phenyl group. Is a polymer in which is bonded, and for example, polysiloxane, polyborosiloxane, polytitanosiloxane, polycarbosilane, polysilastyrene, polysilazane, polytitanocarbosilane and the like can be used. In the present invention, these polymers are used alone or in combination of two or more, and are dissolved or dispersed in a polar organic solvent such as N-methyl-2-pyrrolidone or a phenolic solvent. These polymers are heated and baked in the absence of oxygen to form a non-oxide ceramic coating film, but when baked in the air, the side chain organic groups are eliminated, resulting in extremely excellent heat resistance. Forming an oxide-based ceramic coating film.

The difunctional isocyanate compound used in the present invention is tolylene diisocyanate (TD).
I), 4,4'-diphenylmethane diisocyanate (MD
I), 3,3'-diphenylmethane diisocyanate, 4,4 '
-Diphenyl ether diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-diphenylmethane diisocyanate,
3,3'-dimethyl-4,4'-diphenylpropane diisocyanate, 3,3'-diphenylsulfone diisocyanate,
There are 3,3'-diphenyl sulfide diisocyanate, hexamethylene diisocyanate (HMDI), nonamethylene diisocyanate, 3-methyl-heptamethylene diisocyanate, 2-11-dodecane diisocyanate, 1,4-cyclohexane diisocyanate and the like.

The highly reactive isocyanate group (NCO group) in such an isocyanate compound reacts with the OH group present at the terminal of the organometallic polymer to form a urethane bond, as shown in Chemical Formula 2, There is no residual unreacted OH group in the molecule. Further, by the reaction with an isocyanate compound, in the structure of the organometallic polymer,
Since the linear connection structure of C—C bond having excellent elasticity is introduced, the flexibility of the coating film is improved.

[0011]

[Chemical 2] Due to the above-mentioned function of the isocyanate compound, the mixing ratio thereof is 0.5 to 50 parts by weight, more preferably 1 to 30 parts by weight, based on 100 parts by weight of the organometallic polymer, in terms of resin content. That is, when the mixing ratio of the diisocyanate is less than 0.5 part by weight per 100 parts by weight of the organometallic polymer, the ratio of the C—C bond portion introduced into the molecule due to the reaction with the diisocyanate is small, so that the ratio is sufficiently high. A coating film having properties is not obtained. Further, when the mixing ratio of the diisocyanate exceeds 50 parts by weight, the C—C bond portion introduced into the molecule becomes too large. The CC bond is gradually decomposed and released in the same manner as the side chains of the polymer during the process of baking the organometallic polymer during baking, so that the coating film changes after heating. Is large and the heat resistance is significantly lowered, which is not preferable.

Further, in the present invention, when the reaction between the diisocyanate and the organometallic polymer is remarkably fast, and the reaction proceeds rapidly only by mixing the diisocyanate, and a rapid increase in viscosity or gelation occurs, the diisocyanate is It is desirable to block the terminal NCO group of with a phenolic compound such as cresol. When such a blocked isocyanate is used, the block is removed only by the heating during baking, and the NCO group reacts with the OH group of the organometallic polymer, so that the workability of the paint preparation is good and good. A coating film is formed.

[0013]

In the heat-resistant paint of the present invention, a bifunctional isocyanate compound is added to a paint containing an organometallic polymer as a binder per 100 parts by weight of the resin content of the polymer.
Since it is blended in a ratio of 0.5 to 50 parts by weight, it is possible to achieve both heat resistance and flexibility by applying such a coating on a metal substrate such as stainless steel or aluminum plated steel and baking it. A coating film having excellent surface hardness and no stickiness is formed.

[0014]

EXAMPLES Examples of the present invention will be described below.

Example To 100 parts by weight of polyborosiloxane, 10 parts by weight of MDI, which is a bifunctional isocyanate compound, and 50 parts by weight of magnesium oxide, respectively, were mixed, and these components were mixed with a stirrer such as a mixer to obtain 50 parts by weight. A coating material was prepared by mixing and dispersing in xylene. For comparison, a polyborosiloxane and MDI were mixed in the proportions shown in Table 1, and 50 parts by weight of magnesium oxide was further added to prepare a coating material in the same manner as in the example.

Next, the coating materials obtained in Examples and Comparative Examples were applied to the surface of a SUS430 stainless plate (150 × 50 × 0.3 mm) by a conventional method such as roll coating, and then fired under the conditions shown in Table 1. Then, a coating film having a thickness of 20 μm was formed. Next, the following performance evaluation tests were performed on the coating films thus formed. That is, the flexibility is JIS K5
400 flex resistance tests were conducted, and a film which had no cracks or peeling after being bent at a curvature of 2 mm was accepted. Regarding the presence or absence of stickiness in the coating film, there was one in which the surface of the coating film was felt with a finger and felt stickiness, and one in which there was no stickiness was not sticky. Further, regarding heat resistance, the coating film was kept at a temperature of 500 ° C. for 50 hours, and those having no cracks or peeling were considered to have good heat resistance. The test results are shown in the lower column of Table 1, respectively.

[0017]

[Table 1] As is clear from the test results shown in the table, according to the coating material of Example, it is possible to form a coating film by baking at a relatively low temperature for a short time, and the coating film thus formed,
The surface is dry, non-greasy, and has excellent heat resistance and flexibility.

[0018]

As described above, in the heat-resistant coating material of the present invention, the heat resistance and the flexibility can be obtained by applying this on a metal base material such as stainless steel or aluminum plated steel and baking it. A coating film excellent in heat resistance, high surface hardness and non-stickiness is formed.

Therefore, it is possible to efficiently manufacture an electric wire or the like having good characteristics by continuously applying the coating material, baking and winding.

[0020]

Claims (1)

[Claims] 1. A coating containing an organometallic polymer as a binder, and a bifunctional isocyanate compound in an amount of 0.5 to 50 parts by weight based on 100 parts by weight of the organometallic polymer. Heat resistant paint.