JPS5934302B2 - Marking method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a marking prevention method in which patterns such as letters are applied using a finely powdered rod-shaped marking material to a member having a dark-colored surface and whose temperature changes from room temperature to relatively high temperature, such as a steel plate in the manufacturing process. It is something.

In a steelworks plant, information such as the manufacturer's name, production record, dimensions, shipping destination, etc. is marked on rolled steel plates at appropriate positions on the production line.

In this steel plate manufacturing process, the steel plate is sent to the marking position while still being heated in the previous rolling process.
In the case of a thin steel plate, heat is radiated to room temperature, but in the case of a thick steel plate, the temperature is relatively high, for example, about 400 to 500°C. In this way, when a member has a temperature range from normal temperature to a relatively high temperature, it is required that the pattern is clearly recorded even when marking is performed in this temperature range, especially in a high temperature region. Traditionally, the most common method for marking steel plates is to apply a stencil made of aluminum or tinplate to the steel material, and then apply a liquid heat-resistant paint (which does not discolor with heat), which is mainly made of inorganic substances, over the stencil. There is a known method for marking desired information by spraying on the object.

Since the surface of steel plates is dark at room temperature, a white heat-resistant paint is used. Although this method is stable and reasonably durable even on steel plates at temperatures ranging from room temperature to several hundred degrees Celsius, it has the drawback of being expensive because it is performed manually by an operator. On the other hand, in recent years, in order to save labor, many proposals have been made in which a computer is used to create a marking pattern according to information from the computer, and a marking material in the form of a liquid or fine powder rod is applied onto the steel material in a pattern. Some of them have already been put into practical use (see "Measuring Technology", August issue 1974, P, 62-70, written by Hisao Suzuki).

The liquid marking used here is mainly made of inorganic materials. This is because inorganic materials are inexpensive and do not require the use of organic solvents.
This is based on the reason that an image (marking pattern) that is stable and has appropriate durability can be obtained even when used in objects subject to high temperatures of 0° C. to 500° C. or higher. In contrast,
Most organic materials cannot withstand the relatively high temperatures mentioned above. First, fine powder marking materials have a short history of development, and there is an additional requirement that they are powders, so no marking material comparable to liquid marking materials has yet been developed. Therefore, the present applicant has developed a force method for marking parts using a remote transfer electrophotographic method using a fine powder marking material, which has so far been used only in low-temperature production lines with a limited temperature range. has already been proposed (patent application 1986-1492)
No. 44).

This marking method using electrophotography is characterized in that it is possible to automatically mark any complex pattern without being affected by variations in the thickness of the steel plate. As the fine powder used in the force method described above, it is desirable to use an organic material with stable development characteristics. Inorganic materials are undesirable because they are highly hygroscopic and cause large fluctuations in development characteristics. As mentioned above, the marking material used in the electrophotographic method is made by using a finely powdered organic resin S as an organic material and adding a heat-resistant pigment thereto. This organic resin provides fluidity over a wide temperature range and has the effect of binding the heat-resistant pigment to the member. However, when organic resins are used, stability at relatively high temperatures, that is, thermal discoloration and thermal decomposition, are problems as mentioned above, and this fine powder also has electrical insulation properties and triboelectrification properties. Conditions are also required.

Furthermore, in order to mark a member having a dark color due to its surface strength, such as a steel plate, a marking material containing an organic resin and a white or light-colored opaque pigment is used. But 350℃
In a steel plate heated to a temperature higher than 100, the organic resin changes color and thermally decomposes, resulting in a problem in that the marking contrast decreases and it becomes difficult to distinguish patterns. In view of the above-mentioned circumstances, the present invention provides a marking color that uses a fine powder marking material containing an organic material to prevent the marking contrast from deteriorating even in high-temperature areas and to obtain clear images. The purpose is to provide law. Another object of the present invention is to provide a marking method particularly suitable for marking by electrophotography.

In the present invention, a member having a dark-colored surface, such as a steel plate, is uniformly coated with a white or light-colored heat-resistant coating (one that does not change color due to heat), and then a dark-colored heat-resistant pigment and a dark-colored organic resin are applied on the heat-resistant coating. The marking material is characterized by being applied in a pattern with a fine powder marking material consisting of.

In this way, since the dark marking material is applied on a white or light colored background, even if the organic resin of the marking material becomes dark and thermally discolored in a high temperature region, the marking contrast does not deteriorate and the pattern can be clearly recognized. becomes possible. In other words, organic resins have a temperature range that allows them to strongly bond pigments to parts even when they discolor due to heat, so conventional marking materials based on organic resins can be used while maintaining good marking contrast. The upper temperature limit can be increased by about 20-50°C. In this way, if a dark-colored marking material is used, thermal discoloration of the organic resin, which was a problem when a white or light-colored marking material was used, will not be a problem.

In other words, this advantage interferes with the thermochromic power S, and has conventionally been considered impossible to utilize. This means that some organic resins can also be actively used, and as mentioned above, it is possible to raise the upper limit of the operating temperature. Further, by utilizing the force method of the present invention, a marking material with particularly excellent electrostatic latent image development characteristics can be obtained.

Furthermore, the force method of the present invention opens the door to the use of new organic resins with high heat resistance for marking purposes.
By appropriately selecting the structure of the organic resin, approximately 50
This provides the possibility of covering temperatures as high as 0°C with organic resin-based marking materials.

Hereinafter, the force method of the present invention will be explained in detail.

An example of a member to which the force method of the present invention can be applied is a steel plate S having a dark surface.

First, a heat-resistant white or light-colored paint is applied to this dark surface. This painting area is the area on which the marking pattern will finally be applied. As this paint, a liquid marking ink is used, which is based on water glass and ethyl silicate, which have been widely used in the past, and which is blended with a heat-resistant white pigment. These marking inks penetrate the structure of the black skin and adhere strongly to the surface of the part. In the case of a smooth member, care must be taken to ensure that it adheres sufficiently to the surface. Regarding the composition of these marking inks, for example, Japanese Patent Publication No. 47-43201,
It is described in Japanese Patent Publication No. 47-14285, Japanese Patent Publication No. 47-14286, and Japanese Patent Publication No. 59109-1987.

The above-mentioned marking ink is fixed by volatilization of a solvent mainly composed of water, which is a dispersion medium, but it does not necessarily have to be dry by the time marking is performed.

In particular, when the marking material is applied in a pattern by the electrophotographic method including remote transfer described in Japanese Patent Application No. 149244/1982, the marking ink does not need to be dry. - Marking is performed by applying a dark-colored fine powder marking material based on an organic resin onto the white or light-colored paint. A typical example of this is electrophotography using remote transfer. In this method, a latent image on a recording drum is developed with a marking material, and an endless belt made of a conductive material is brought into close contact with the recording drum carrying the powder image, so that the powder image is transferred onto the endless belt.
This endless belt has heat resistance and transfers the transferred powder image in close contact with the marking member. Recorded information such as dimensions, manufacturer's name, shipping destination, etc. is marked on the marking member by this endless belt. Next, a mechanism for fixing the marking material according to the temperature of the member will be explained. (1) When the temperature of the part is below 100°C Since the marking material contains a solvent-soluble organic resin and a heat-resistant pigment, spraying a fixing agent containing a solvent or plasticizer will dissolve the organic resin. and fixed onto the member.

Note that the organic resin is not soluble in solvents but may be soluble in heat. When using such organic resin,
Heat can be used instead of a fixing agent. A dark heat-resistant pigment, typically carbon black, is used, and a marking pattern is formed as a dark pattern on a bright background. The solvent is selected depending on the composition of the resin, but non-flammable solvents are preferred for operational convenience, and include chlorinated hydrocarbon solvents. (2) When the temperature of the member is 100° C. or higher, since this is a range in which the organic resin can thermally flow, it is easiest to fix by utilizing the heat flux of the member.

Although the organic resin is in an uncured state in the form of fine powder, it may be cured by a blended curing agent. The desirable upper temperature limit for the organic resin to stably fix is 300 to 35
It is 0°C.

From this point onwards, the organic resin will thermally decompose and coloration will begin. Depending on the compound, thermal separation and coloring may begin at low temperatures. Epoxy resins and nylon resins begin to color rapidly when the temperature exceeds 300°C, so when they are combined with light-colored pigments, the marking contrast decreases, but when combined with dark-colored pigments as in the present invention, Higher temperatures (approximately 2'C) can be used.

Some types of linear polyester begin to slowly become colored when the temperature exceeds 35°C, but they do not lose their ability to bind pigments up to around 400°C.

Therefore, it cannot be used up to 400° C. without deteriorating the marking contrast. The temperature of the member in the above description is the temperature of the member when the member reaches the marking position and marking is performed, and is referred to as "marking temperature 1" in later examples.

Therefore, this temperature decreases rapidly when the steel plate is thin, but it does not decrease easily when the steel plate is thick. Actually, in the case of a steel plate with a thickness of about 5 to 10 V1, this temperature is 10 to 3
A formulation that does not cause blocking when organic resins containing components that can withstand higher temperatures, such as O-silicone-modified epoxy resins and alkyd resins, which deteriorate rapidly in an atmosphere of 0°C, are made into fine powder at room temperature. This extends the marking material to a higher temperature range.

Although there are areas where the organic shelf is considerably colored, the pigment can be bonded to the member by the action of the highly heat-resistant silicone component. Therefore, if the background is made white as in the present invention, the marking contrast will not deteriorate due to the colorability, so the heat resistance of the silicone component can be fully utilized. Organic resins with even higher heat resistance are also known, but since many of them have conjoint double bonds, they are themselves relatively darkly colored.
Therefore, these can be conveniently used in the present invention as they are in the form of a powder in the form of a precursor. The marking material of the present invention will be explained in more detail below.

Heat-resistant pigments include dark-colored pigments such as iron oxide, triiron tetroxide, graphite, carbon black, lead oxide, chrome black, chrome copper, upper, and cobalt oxide. To prevent blocking and excessive increase in specific gravity, extender pigment (Al2
O3, MgO, talc, SiO2., CaSiO3, clay, etc.) may be used in combination. Also, to increase flame retardancy,
Sb2O3 or the like may also be added. It is difficult to use organic resins that have extremely low softening points because they tend to bulge when made into powder.

T9> It is preferable to have a temperature of 50°C and be somewhat crystalline. These include polyvinyl chloride, cellulose, acetate/butyrate, acrylic ester-based copolymers, styrene-based copolymers, linear polyester resins, thermosetting polyester resins, epoxy resins, and polysiloxane resins. , phenolic resin, rosin and its derivatives, polyamide resin, etc. Flow regulators, plasticizers, and pigment dispersants are appropriately added to these. In the present invention, among these resins, one that is soluble in the solvent at room temperature is used because the marking material often adheres to the member and becomes fixed due to the action of the solvent in the following areas when the organic resin is softened.

The organic resin is preferably one that is easily pulverized and melted in an appropriate temperature range, spread over the member, and then hardened. The curing speed depends on the temperature, but the temperature of the member is about 40℃ from room temperature.
Because of the wide temperature range down to 0° C., it is difficult to design a thermosetting composition so that sufficient flow occurs prior to curing over all temperature ranges. In reality, the components of the composition are set according to the temperature range in which the parts are frequently used in the target production line in order to most effectively cause fluidization and hardening. In higher temperature ranges it is advisable to use suitable auxiliary means to ensure compatibility with the components. From the above explanation, the organic resin suitable for the force method of the present invention is generally a thermoplastic resin composition or a composition that hardens easily at the upper limit of the operating temperature range.

These include linear thermoplastic polyesters. It was confirmed that this linear polyester gradually undergoes a thermosetting reaction when the temperature exceeds 300°C. This is thought to be due to mutual dehydration of COOH in the 0H group at the end of the molecular chain, or to the bonding of the cleaved ester bond with the end group. Generally speaking, the technology of so-called fine powder coatings can be effectively transferred to the production of the marking material of the present invention, but unlike in the case of coatings, the pattern does not necessarily have to be glossy, and in some cases Since a high specific gravity is desirable, a high pigment content may be sufficient.

Hereinafter, the present invention will be explained by giving examples.

Example 1 A white paint having the following components was uniformly sprayed with a spray gun onto the area to be marked of a steel plate having black scales after the rolling process.

The temperature of the steel plate during painting ranges from room temperature to 400℃.
Is the thickness of the steel plate 10? It was hot.

A negative electrostatic latent image was formed on a PET film coated with aluminum, and developed with a dark-colored fine powder marking material (particle size: about 20 μm) having the following composition. 5? Apply the developed powder image to the painted surface? When a potential of 900 was applied between the electrode and the steel plate on the back of the PET (the steel plate had negative polarity) and ultrasonic vibration was applied to the PET, the marking material in the form of fine powder was generated. Almost the entire amount was transferred onto the steel plate.

When the marking temperature was 370°C or lower, a clear pattern remained on the steel plate after cooling. When marking was performed on a steel plate at a temperature of 380° C. or higher, the organic resin became crumbly and the pattern peeled off immediately.

Note that when the marking temperature was 125° C. or lower, it was possible to fix using trichlorethylene as a solvent. Example 1 The composition of υ was kneaded and pulverized to obtain a marking material in the form of black fine powder with an average particle size of 30 μm.

Using this marking material, P by the same force method as in Example 1.
An electrostatic latent image was developed on ET. Ichiriki, thickness 50? The same liquid white paint as in Example 1 was uniformly applied onto the steel plate.

The same marking pattern as in Example 1 was transferred onto the steel plate by changing the temperature from 200°C to 360°C. A strong image remained until the steel plate temperature reached 34°C, but at temperatures above 350°C, it carbonized and mechanically collapsed and peeled off immediately. Example A white paint consisting of the following components was applied onto a steel plate.

To this was added 80 parts of a 40% water emulsion of butyl arylate/methyl methacrylate copolymer (weight ratio 60:40).

The marking material consisted of the following ingredients and was made by dry kneading and grinding.

Polyester resin 80 parts by weight (terephthalic acid 50m01%, isophthalic acid 50m01
The person in charge and Neopentyl Glycol 60! NOlf), copolyester consisting of 40m01% of ethylene glycol,
The molecular weight was approximately 20,000) and the average particle size was approximately 40 μm.

Using this marking material, a marking pattern was transferred onto the white paint using the same force method as in the example. The thickness of the steel plate was 501I111, and when the temperature was varied from 200 to 420°C, a strong dark green image was obtained up to 400°C, and no peeling occurred even after the steel plate was naturally cooled.

Comparative Example 1 A steel plate with a thickness of 1077I and 11t has a black crust,
A white powder marking material consisting of the following components was directly transferred in the same manner as in Example 1.

This image maintained high contrast when the steel plate was heated to 300°C or lower, but when the steel plate temperature rose above this temperature, coloring began, and when the marking temperature exceeded 340°C, the contrast decreased and it became difficult to distinguish.

At 370°C, the contrast almost disappeared.

That is, when compared with Example 1, it was confirmed that in Example I, the upper limit temperature that can be used was expanded by about 40°C. Comparative Example] was kneaded and pulverized to obtain a marking material in the form of white fine powder, which was directly transferred onto a black steel plate using the same force method as in the example.

Coloring started at 300°C, almost no contrast was observed at 340°C, and it turned black and carbonized at 350°C.

The upper temperature limit used for marking was up to 32'C. When compared to the embodiments of the present invention, the embodiments are about 3
Since it can be used up to 40°C, the upper limit temperature of the power of the example has been extended by about 20°C.

Comparative Example 25 parts by weight of titanium oxide was used in place of the chromium dioxide and carbon used in the example, and the image was directly transferred onto a black steel plate.

At temperatures above 300°C, discoloration began slowly, and at 380°C, discoloration became severe and the contrast was significantly reduced.

At 400℃, the reflection density of the black skin is 1.6, while the image area has a reflection density of 1.6.
．． 15, the contrast was about 0.45, and the upper limit temperature that could actually be used was about 3700C.

On the other hand, since the embodiment can be used up to about 400°C, the upper limit temperature is extended by about 30°C.

As mentioned above, in the force method of the present invention, a white or light-colored paint is applied onto the member, and a dark-colored marking material is applied on this bright background. The effects of decomposition can be eliminated, thereby extending the usable upper temperature limit.

Claims (1)

[Claims] 1. A method for marking a high-temperature iron plate with a dark-colored surface, in which a white or light-colored heat-resistant coating is applied to at least the area of the iron plate where the marking pattern is to be applied, and a dark-colored coating made of a heat-resistant pigment and an organic resin is applied on top of the white or light-colored heat-resistant coating. A marking method characterized in that a marking material in the form of a fine powder is applied in a pattern by electrophotographic transfer.