JPS5833904B2 - Paint for protecting metal plates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a paint for protecting metal plates that can prevent corrosion and scratches on metal plates and greatly improve friction resistance.

= Metal plates such as general stainless steel plates, aluminum plates, and steel plates are subjected to cold plastic processing such as punching, bending, and drawing by press or roll processing, and are used for various purposes such as automobiles, home appliances, and kitchens. It is served to.

Conventionally, when manufacturing these metal products, post-processing steps such as puff polishing are required after processing to prevent corrosion and scratches on the metal plate during storage and processing before cold plastic processing. Efforts have been made to simplify the process as much as possible, to improve the wear resistance of the metal plate, to prevent the metal plate from cracking or cracking during processing, and to improve workability.

However, none of these methods that have been used for a long time have been effective in preventing corrosion and scratches on metal plates and improving their abrasion resistance or workability.

For example, it is known that the main purpose of preventing corrosion and scratches is to apply general strippable paint or an adhesive sheet to the surface of a metal plate, but this method cannot be expected to provide much abrasion resistance during processing. On the contrary, if the viscosity of the adhesive layer of the coating film or sheet decreases due to frictional heat during processing, the frictional resistance will increase and there is a risk that the processability will be adversely affected.

In addition, a method of applying a liquid lubricant such as animal or vegetable oil to the surface of a metal plate is known as an advantageous means of improving friction resistance, but this method prevents corrosion and scratches during storage or processing. showed little efficacy.

Therefore, in recent years, polyvinyl chloride organosol and other special resins or resin compounds have been used as strippable paints to give the paint film a certain degree of lubricity. Various improvements have been devised, such as applying lubricants.

However, none of these methods can fully satisfy both the prevention of corrosion and scratches on metal plates and the improvement of abrasion resistance, and if one property is satisfied, the other property may have some drawbacks. There was a tendency for it to occur.

Moreover, many of these conventional methods have the disadvantage that the workability is significantly inferior when removing a metal plate after cold plastic working.

For example, when an adhesive sheet is used, the peeling process tends to be laborious and cumbersome, and it is extremely difficult to clean using lubricating oil.

Another disadvantage is that, for example, products using polyvinyl chloride organosol require high temperatures of 200 to 400°C for baking, so when coating steel plates, strain patterns due to heat treatment called stretcher strain occur, resulting in the product being damaged. This has led to problems such as roughening of the skin and accelerated corrosion.

The purpose of the present invention is to provide a paint for protecting metal plates that is capable of preventing corrosion, abrasion, and scratches on metal plates as well as improving abrasion resistance. It is an object of the present invention to provide a paint for protecting a metal plate that can be easily cleaned and removed without requiring any manual labor after cold plastic working and has few other drawbacks seen in conventional methods.

This invention was discovered as a result of intensive studies to achieve the above object. A paint that can be easily removed by a cleaning solution, and in which a lubricant that is poorly soluble or incompatible with the paint resin and has a melting point that can be melted by frictional heat during processing is added to the paint resin component. This is due to the fact that it was mixed in at a rate that was 50% less than the total amount.

The lubricant used in this invention, which has a melting point that can be melted by frictional heat during processing, is generally a solid at room temperature and has a melting point of 10 to 40°C or higher, although it varies depending on the atmospheric temperature.

On the other hand, machine oil, rapeseed oil, silicone oil, etc., which are liquid lubricants at room temperature, can significantly impair the adhesion between the metal plate and the coating film during storage or processing. It cannot be used because the coating film easily peels off.

Preferred examples of these lubricants include natural fats and oils having a relatively wide melting point range, such as cacao butter, wax, coconut oil, beef tallow, and pig intestines.

Paraffins such as cleaved n-octadecane and n-hexadecane, fatty acids such as lauric acid, stearic acid, and oleic acid, fatty acid esters such as methyl myristate and ethyl stearate, and fatty acid amides such as stearic acid amide are also used. can.

In the present invention, a lubricant must be selected from among these lubricants that is poorly soluble or incompatible with the resin component of the paint used.

This is because if a compatible lubricant is used, it will act like a plasticizer and reduce the strength of the coating film, causing problems in preventing scratches and scratches on the metal plate. When the paints are stored on top of each other, blocking may occur between the coatings, causing problems such as 15.

In this way, for the present invention, by selecting and using a lubricant with an appropriate melting point as described above and a lubricant that is poorly soluble or incompatible with the paint resin used, good lubrication ability can be imparted to the paint film. At the same time, it maintains adhesion to metal plates, coating strength, and other functions necessary as a protective coating.
This aims to simultaneously prevent the occurrence of corrosion and scratches on the metal plate and improve its abrasion resistance.

In this invention, the lubricant content should be 50% less by weight than the total amount including the paint resin, and if it is used in excess of this amount, the strength of the coating will be extremely poor and the metal plate will corrode. Problems arise in preventing the occurrence of scratches.

On the other hand, if the amount of stool is too small, the lubrication prevention function will not be sufficient, so generally the ratio should be more than 2 weights and 50 weights less, preferably 2 to 30 weights more. good.

In this invention, paints to which such lubricants are mixed include generally commercially available varnishes and lacquers, as well as paints whose resin content is polyacrylic resin, polyvinyl alcohol, polyvinyl acetate, polyacetal resin, and cellulose resin. , polystyrene, polyamide resin, polyurethane, polyester resin, alkyd resin, etc., as long as they can be easily washed and removed with a cleaning solution such as general organic solvents, water, and aqueous alkaline solutions.

This paint contains conventionally known additives, such as rust preventives,
Preservatives, antifoaming agents, etc. may be added. In order to apply the protective coating of this invention to the surface of a metal plate, general coating methods such as spray, reverse roll coater,
The coating may be carried out by using a kiss coater, flow coater, knife coater, brush coating, or the like, and when dried after coating, a coating film in which the lubricant is uniformly dispersed and mixed is formed.

This coating has good adhesion to the metal plate surface and sufficient coating strength, and like general strippable paints, it effectively prevents corrosion, abrasions, and scratches on the metal plate. do.

In addition, the lubricant added gives the coating film itself a lubricating ability, which greatly improves the friction resistance during processing and prevents metal plates from cracking under severe processing conditions such as deep drawing. It also prevents cracks and contributes to improved workability.

On the other hand, after cold plastic processing such as deep drawing, ordinary organic solvents,
The lubricant is easily removed by immersion in a cleaning solution such as water or an aqueous alkaline solution, and at this time the lubricant separates from the metal plate surface along with the coating, making it difficult to remove the lubricant as in the case of using conventional liquid lubricants alone. It won't cause any problems.

The coating thickness required to exhibit this effect is usually 3 to 50μ, and preferably tL< is 5 to 15μ; if the coating thickness is too thin, the corrosion and scratch prevention effect will be poor, and if it is too thick. Both of these methods are not preferable, since the time required for cleaning and removal after processing becomes longer.

As detailed above, this invention has excellent lubricity by mixing a specific proportion of a lubricant that is poorly soluble or incompatible with the paint resin and has a melting point that can be melted by frictional heat during processing. The objective is to provide a coating for protecting metal plates that can form a coating film with good washability.This coating prevents corrosion and scratches on metal plates and improves the abrasion resistance of metal plates. The following are examples of the present invention. Describe.

In the following, parts shall mean parts by weight.

Example 1 n per 100 parts of a copolymer consisting of 40 parts of butyl acrylate, 50 parts of methyl methacrylate and 10 parts of styrene.
- 10 parts of octadecane (melting point 28 DEG C.) was added and kneaded with a roll in the presence of xylene to obtain a paint for protecting metal plates of the present invention having a solid content of 24 weight and a multiviscosity of 8 poise.

This coating material was applied to a JIS-03310 SPC-grade bright steel plate (0.5 fl thickness) to a dry thickness of 10 microns and dried to form a protective coating film having lubricity.

This coating has good adhesion to the surface of the steel plate, and has satisfactory coating strength and surface hardness of 4H, and can sufficiently prevent corrosion and scratches during storage before processing or during processing. Ta.

Next, in order to examine the workability of this coating film, the drawing depth at which the bottom of the metal plate cracked was measured using a Swift deep drawing test.

The diameter of the test piece is 100B (cut out into a disk), the die hole diameter is 53.64M, the die shoulder radius is 13.0m,
The punch diameter is 501F/IL button and the punch bottom round radius is 511WL, and the measurement result is a drawing depth of 27M, which is a great improvement compared to the drawing depth of 23m in the case of the steel plate alone without coating. It turned out that there was.

In addition, when similar measurements were performed on the above-mentioned paint without the addition of n-octadecane, the aperture depth was 22.
m, and the workability of the paint not containing n-octadecane was worse than that of the steel plate alone.

Next, on the test piece that was drawn in this way,
When we tested the cleanability of the paint film by immersing it in gasoline, we found that it could be washed off in a short time.

Example 2 Beef tallow (melting point 30-38°C ) was added and uniformly dispersed and mixed to obtain a paint for protecting metal plates of the present invention having a solid content of 23 and a weight multiviscosity of 11 poise.

Using this paint, the steel plate described in Example 1 was coated with a dry thickness of i.
A protective coating film having lubricating properties was formed by coating and drying so as to give oμ.

As in the case of Example 1, this coating film had good adhesion to the steel plate surface, and the coating strength was satisfactory with a pencil hardness of 2H, and corrosion and scratches did not occur during storage or processing before processing. It was possible to sufficiently prevent this.

Next, in order to examine the workability of this coating film, the critical drawing ratio (diameter of the test piece relative to the die diameter at which cracks occur in the test piece) was measured using a Swift deep drawing test, and the value was 2.34. It was found that the workability was greatly improved compared to the limit drawing ratio of 2.26 in the case of a steel sheet alone without a coating film formed thereon.

After the octopus processing test, the washability of the coating film was examined by immersing it in a 2N aqueous solution of caustic soda, and it was found that it could be washed away within 1 minute at 60°C.

Example 3 In a resin solution prepared by dissolving 50 parts of butyral resin (BM-3 manufactured by Tsukisui Kagaku Co., Ltd.) and 50 parts of butyl acrylate-methyl methacrylate copolymer in methanol,
Cocoa butter (melting point 22 to 27°C) is added at a ratio of 20 parts to 100 parts of resin content and uniformly dispersed and mixed to provide a metal plate protection of the present invention with a solid content of 21% by weight and a multiviscosity of 9 poise. I obtained the paint for use.

A stainless steel plate (SUS430, 0.5M thick) bright annealed using this paint has a dry thickness of 1.
A protective coating film having lubricating properties was formed by coating and drying to a coating thickness of 0μ.

This coating film has good adhesion to the stainless steel plate and has satisfactory coating strength with a pencil hardness of 2H, and can sufficiently prevent corrosion and scratches during storage before processing or during processing. Ta.

Next, the quality of workability due to this coating film was investigated in the same manner as in Example 2, and the limiting drawing ratio was 2.36, which was 2.06 for the stainless steel plate alone without the coating film.
It was found that the workability was greatly improved compared to the previous one.

Further, after this processing test, the cleaning properties were examined by immersing it in a commercially available cleaning solution (Fine Cleaner 3152 manufactured by Nippon Parkerizing Co., Ltd.), and it was found that the paint film could be easily cleaned and removed by just immersing it at 70° C. for 1 minute.

Example 4 Tetradecyl alcohol (melting point 38°C) was added to a methanol solution of butyl acrylate-methyl methacrylate-acrylic acid copolymer at a ratio of 10 parts to 100 parts of resin and uniformly dispersed with a homomixer. By mixing, a coating material for protecting a metal plate of the present invention having a solid content of 22% by weight and a viscosity of 10 poise was obtained.

This coating material was applied to a 0.5-mm aluminum plate to a dry thickness of 10 microns and dried to form a protective coating film having lubricating properties.

This coating film has good adhesion to the aluminum plate surface, and the coating strength is satisfactory with a pencil hardness of 2H.
It was possible to sufficiently prevent corrosion and scratches from occurring during storage before processing or during processing.

Next, in order to examine the workability of this coating film, we first measured the drawing depth at point 1 where the upper part cracked using the Erichsen test.
At No. 08, the drawing depth was 5.1 mm, and the effect of improving workability was clearly recognized compared to the drawing depth of 4.5 M in the case of aluminum plate alone.

Next, we measured the punching force at point 1 where the bottom part cracked using the Swift deep drawing test, and found that the diameter of the test piece was 10Crr.
When the wrinkle weight load is 50 to 2 at L, the punch force is 91
3KP, and the punching force for aluminum plate alone is 5
It was found that the workability was clearly improved compared to 45KP.

After such a processing test, the cleaning performance was examined by immersing it in Fine Cleaner 342, and it was found that it could be easily cleaned and removed within 1 minute at 75°C.

Comparative Example A paint for protecting a metal plate was obtained in exactly the same manner as in Example 4, except that 3 parts of machine oil, which is liquid at room temperature (20° C.), was used instead of tetradecyl alcohol.

Using this paint, a coating film was formed on the surface of an aluminum plate in the same manner as in Example 4, and a drawing test (circle diameter lQa, load 5
00g), the results were 8 to 10/10, and the value measured for Example 4 was O/1.
The adhesion was very poor compared to that of 0.

For this reason, it has not been possible to sufficiently prevent the occurrence of scratches on the metal plate during storage or processing.

Claims (1)

[Claims] 1. A paint that is applied to the surface of a metal plate before cold plastic working and that can be easily removed with a cleaning solution after the above-mentioned processing, and that is insoluble or incompatible with the resin component of the paint and that A paint for protecting a metal plate, characterized in that it contains a lubricant having a melting point that can be melted by frictional heat in a proportion of 50% less by weight than the total amount of the paint and resin.