JPS5817178A - Weldable paint with excellent film properties - Google Patents

Abstract

PURPOSE:To provide a weldable paint excellent in workability, electric weldability and film properties, prepared by adding hollow, thin-walled carbon particles as electrically conductive ingredient. CONSTITUTION:The weldable paint is prepared by dispersing hollow, thin-walled carbon particles (particle size of about 100-350mu and wall thickness of about 5mu) in a mixture of a binder (e.g. PVC or polyurethane resin) and a solvent (e.g. ketone, aromatic hydrocarbon or lower alcohol). The carbon particles are used in amount of about 15wt% or more (pref. 20-40wt%) of dry film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to reduce the amount of conductive material added (by adding hollow thin-walled carbon grains as a conductive material), thereby creating a weldable paint with improved coating performance.

Conventionally, as a method of making the coating film conductive and improving weldability, it has been carried out to add conductive substances such as metal powder, carbon black, and graphite to the Ik material. However, in order to make the paper coating film conductive by adding these conductive substances, it is necessary to increase the amount of addition, and the coating workability and coating performance of the paint may be significantly reduced.

For example, when using 808 powder as a metal powder, 808 powder has coarse particles and is heavy, so it settles during paint storage or painting, making it difficult to coat evenly and requiring a large amount of addition. As a result, the adhesion, processability, and corrosion resistance of the coating film were significantly reduced.

In the case of some carbon plaques and graphite, there is no problem of separation because they are light, but the particles are moldy, so it is necessary to add a large amount of K to connect them and make them conductive. Therefore, as with 808 powder, there were various problems in terms of coating film performance compared to conventional powders.

The present invention provides a weldable coating material that solves the problem of deterioration in coating workability and coating film performance due to the addition of a conductive substance.

In general, in weldable paints, in order to improve coating workability and coating performance, it is advantageous to reduce the amount of conductive substances added. However, if the amount added is reduced, the conductive substance will not stick together and will no longer have conductivity, making it impossible to weld even if it is painted on a metal plate.

Although this problem has been difficult to solve by combining or improving conductive materials that have been used in the past, the present inventors have solved this problem by using hollow thin-walled carbon grains.

That is, the present inventors have succeeded in reducing the amount of added conductive material while maintaining the conductivity of the paper by adding hollow thin-walled carbon grains as at least part of the added conductive material.

Since the hollow thin-walled carbon grains have a low specific gravity, the amount of the conductive material added can be reduced by replacing at least part or all of the conventionally added conductive material with the hollow thin-walled carbon grains.

In the case of the present invention, such hollow thin-walled carbon particles include carbospheres (particle size 5 to 150μ, particle thickness 1 to 2s,
VIILI9AR, USA), Flekasphere [particle size 1
00-350a% particles with a wall thickness of 5μ, using Kureha Chemical Co., Ltd., are used alone or together with a conventional conductive substance and dispersed in a binder and a solvent to form a paint.

In this case, hollow thin-walled carbon grains are used as the binder.There is no need to use a special binder, and any binder that can be used in ordinary paints can be used.For example, vinyl chloride resin, vinyl acetate, etc. Resins based on thermoplastic resins such as polyester resins and fluorine resins, resins based on thermosetting resins such as alkyd resins, polyurethane resins, epoxy resins, acrylic resins and unsaturated polyester resins, etc. All resins conventionally used as binders for paints can be used.

The same applies to the solvent, and any solvent that can dissolve the binder may be appropriately selected and used. For example, depending on the type of binder, ketone solvents such as methyl ethyl ketone and cyclohexanone, aromatic hydrocarbon solvents such as doluol and quidylol, and ether solvents may be appropriately selected and used.

Furthermore, in the case of the paint of the present invention, the use of additives that are normally added to paints, such as anticorrosive pigments, stabilizers, etc., is not prohibited.

When only hollow thin-walled carbon grains are used as the conductive material,
K is used to impart weldability to the coating film, and the K content is about 15% by weight in the dry coating film. 10
- Below -, the coating film does not conduct electricity at all, and when it reaches about 15 -, electricity becomes possible. However, with this consistency, there are many variations in the welded part, and K of about 201 is required to obtain stable weldability.

On the other hand, even if the addition amount is increased by about 20-20%, welding stability will be improved slightly, but the coating performance will deteriorate.
When the temperature reaches about 5 sos, the coating becomes so K that cracks and peels of the coating occur in some areas. Therefore, in order to maintain good weldability and coating film performance, 20 to 9 hollow thin carbon grains can be used interpolated with other conventional conductive materials. In this case, the addition of hollow carbon grains reduces the slack conductive material.Equivalent weldability can be achieved without the addition of a corresponding amount, and therefore the overall amount of conductive material added can be reduced.

Next, the present invention will be explained with reference to examples.

Example 1 Commercially available hollow thin-walled carbon grain carbospheres were sieved and separated to adjust the particle size to 1325 mesh, which was then heated in a paint conditioner together with a binder and a solvent for 2 hours. Mu.

82 types of paint were prepared. On the other hand, as a comparative example, Kerr's Pump Rack (Pulcan XO-72, Cabot Granules [3]
0ftμ) with the same binder and solvent in paint preparation machine K.
The meat was kneaded for 24 hours, and the result was 0.0% as shown in Table 1. Adjusted the D2 type of paint and mourned.

(Note) The values in C) in the table are the weight ratios of the dry paint film.

Next, these paints were painted and baked on a chromate-treated galvanized steel plate to produce a coated steel plate with a coating thickness of 20 μm, which was subjected to a spot welding test and a bending test under the following conditions.

(1) Spot welding conditions Painted steel plates are most likely to be welded together. Two steel plates were stacked one on top of the other with their coated surfaces facing each other, and welding was performed by applying electrodes to the unpainted surfaces on both sides. Welding was performed using a chromium copper electrode with a tip diameter of 4.8 mm, a welding current of 7000 A, and a pressure of 15
The test was carried out at 0A9 with a current application time of 12 seconds. In addition, this welding was judged based on the following criteria.

0 Nugget can be formed and welding is good.

× No current flows at all.

(2) Bending test JI81G-3! Based on bending test of I 12 2t4j
y) Bending was performed, and the cellophane tape was peeled off from the bent portion.

Judgment was based on the following criteria.

O There is nothing abnormal.

8. Part of the paint film peeled off.

×: The paint film was mostly peeled off.

Table 2 shows the results of these tests.

Table 2 shows that when the amount of hollow thin carbon particles in the coating film is 209%, both weldability and coating processability are good, but when it becomes 40%, the coating processability deteriorates.

On the other hand, when a carbon black is used, the result is that one has to choose between weldability and coating processability.

Furthermore, when hollow thin-walled carbon grains are used to impart weldability to the coating film, the content can be reduced to half that of carbon black.

Example 2 In the same manner as in Example 1, the paints shown in Table 3 were prepared and subjected to surface treatment, and painted and baked on a galvanized steel sheet. Thereafter, the obtained painted copper plate was spot welded under the same conditions as in Example 1, and its weldability was investigated.

The results are shown at the bottom of each paint in Table 3.

The values in parentheses in Table 3 (2) are the weight ratios of the metal powder and the hollow thin carbon particles in the case of a dry coating film.

As is clear from the above table, when hollow thin-walled carbon grains are interpolated in place of a part of the metal powder, it is possible to achieve the same weldability even without containing an amount equivalent to the reduced amount of metal powder. I can do it.

As described above, since the coating material of the present invention has a lower content of conductive substances than the conventional coating material, the processability of the coating film is significantly improved. Furthermore, unlike conventional conductive materials, there is no problem of sedimentation, so painting workability is improved.

patent applicant Nisshin Steel Co., Ltd. agent Mitsuru Susumu Fuji

Claims (1)

[Claims] A weldable paint with excellent coating film performance, characterized in that hollow thin-walled carbon grains are added as at least a part of the conductive substance in a paint to which the conductive substance is added.