JPH10212432A - Paint for on-demand type dot printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject paint which dries quickly at a practical level and which can reduce the idle operation, particularly during printing operation by blending an inorganic coloring pigment, a specific film-forming resin and a specific organic solvent mixture. SOLUTION: This paint is intended for use in an on-demand type dot printer provided with a plurality of ejection nozzles. It comprises (A) 5 to 10wt.% of an inorganic coloring pigment such as titanium white, (B) 5 to 10wt.% of a film-forming resin selected from ethyl cellulose resin, acetyl butyl cellulose resin, hydroxypropyl cellulose resin, and thermoplastic acrylic resin, (C) 5 to 15wt.% of a highly volatile organic solvent having a boiling point of <80 deg.C and capable of easily dissolving the component B, (D) 45 to 75wt.% of an organic solvent with a medium-degree of volatility, a boiling point of >80 deg. and, by itself, not capable of easily dissolving the component B, and (E) 10 to 20wt.% of a low-volatile organic solvent having a boiling point exceeding 120 deg.C and capable of easily dissolving the component B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paint for an on-demand type dot printing apparatus, and more particularly, to a paint provided with a plurality of discharge nozzles for printing large dots on the surface of a large steel material such as a steel plate material or a steel shape. The present invention relates to a paint for an on-demand type dot printing device.

[0002]

2. Description of the Related Art As is well known, in a steel material manufacturing plant, an automobile manufacturing plant, a shipyard, etc., letters and symbols indicating the material and application are displayed on the surface of a large steel material such as a steel plate material or a shape steel material. Lines that indicate the positions of cutting, bending, and the like are drawn by an on-demand type dot printing apparatus having a plurality of ejection nozzles.

[0003] An on-demand type dot printing apparatus having a plurality of ejection nozzles widely used for the above-mentioned applications (hereinafter, referred to as a dot printing apparatus).
"On-demand dot printing device for steel"
Is provided with a plurality of discharge nozzles having a diameter of 0.10 to 0.25 mmφ arranged toward the surface of the print-receiving material (the number of discharge nozzles increases according to the width of the target print-receiving material). By controlling the opening and closing of the nozzles, the paint is intermittently discharged in the form of dots, and required characters, symbols and lines are drawn.

As shown in FIG. 1, a typical structure of a discharge nozzle having a diameter of 0.10 to 0.25 mmφ is that a valve seat 3 and a spherical valve body are provided inside a nozzle opening 2 of the discharge nozzle 1. 4
The spherical valve element 4 is connected to a movable iron core 6 of an electromagnetic solenoid via a rod 5 and a paint chamber 7 is provided around the valve seat 3 and the valve element 4.
The discharge control valve is opened and closed by the reciprocating motion of the movable iron core 6 indicated by an arrow in the figure, and the paint is intermittently discharged in a dot form from the nozzle opening 2.
In the figure, 8 is a return spring, 9 is a solenoid coil,
Reference numeral 10 denotes a fixed iron core, and reference numeral 11 denotes a paint feeding path.

[0005] Unlike an on-demand type dot printing apparatus for offices which prints on paper which can absorb paint or ink, an on-demand type dot printing apparatus for steel materials prints on the surface of a steel material which cannot absorb paint. Therefore, it is necessary to use a quick-drying paint, and if the touch drying time (time during which the printed coating film does not stick to the finger) is not short (usually a paint within 120 seconds), the printed coating film must wait for drying. It is not practical because it takes a long time and hinders the assembly work.

[0006] The paint used for the on-demand type dot printing device for iron and steel materials is composed of an inorganic coloring pigment (usually titanium white), a film-forming resin (usually a cellulose resin or a thermoplastic acrylic resin) and a volatile resin. An organic solvent (usually, tetrachloroethylene or dichloromethane) having a touch dry time of 100 seconds or less is commonly used.

[0007]

SUMMARY OF THE INVENTION An on-demand type dot printing apparatus having a plurality of ejection nozzles, when operating,
According to the required characters / symbols and lines to be printed, the required discharge nozzles are activated from among the plurality of discharge nozzles to discharge the paint, and the other discharge nozzles are set to a rest state (a state in which the paint is not discharged). Since printing is performed, the paint adhering to the vicinity of the tip of the discharge nozzle that has been turned off dries and the opening of the discharge nozzle becomes clogged, not only when the device is not operating but also when the device is operating. Even if the discharge nozzle is activated, even if the discharge of the paint becomes impossible or the discharge does not occur, the dried paint adhering becomes an obstacle and the paint does not discharge straight and the dot is not formed. There is a problem that disturbance occurs.

The above problem is unavoidable in an on-demand type dot printing apparatus for steel materials in which the use of quick-drying paint is indispensable. The work is required to discharge the paint from all the discharge nozzles without aiming), and even if the dot is disturbed even during operation, the printing work is interrupted and the blanking work is performed, Aside from the idling operation before the start of operation, the idling operation during operation significantly reduces the printing operation efficiency.

[0009] The above problem becomes more remarkable as the number of discharge nozzles of the on-demand type dot printing apparatus for steel materials increases, and from the viewpoint of increasing the efficiency of the steel material production line, 100
In today's demand for a device in which ~ 1000 discharge nozzles are arranged, there is a problem that it is impossible to sit down.

As far as the present inventor knows, the technique proposed as a solution to the above-mentioned problem is a cleaning means for cleaning and removing dry paint adhering near the discharge nozzle and a discharge nozzle. This is a solution from the discharge nozzle structure surface where paint does not adhere in the vicinity of the opening of any of the above, and any means is not satisfactory in terms of cost and maintenance if the number of discharge nozzles is greatly increased. Met.

Therefore, the inventor of the present invention believes that solving the above problem from the paint side can sufficiently cope with the case where the number of discharge nozzles is greatly increased, and has been applied to an on-demand type dot printing apparatus for steel materials. The technical problem of the present invention is to provide a paint having a quick-drying property and capable of reducing the blanking work, particularly the blanking operation during operation, as much as possible. Trial production·
As a result of repeated experiments, the present invention was completed.

[0012]

The above technical objects can be achieved by the present invention as described below.

That is, the present invention relates to a paint for an on-demand type dot printing apparatus having a plurality of discharge nozzles, comprising 5 to 10% by weight of an inorganic coloring pigment, ethyl cellulose resin, acetyl butyl cellulose resin, and hydroxypropyl cellulose resin. And a highly volatile organic solvent having a boiling point of less than 80 ° C. and a solubility of 5 to 10% by weight of a film-forming resin selected from thermoplastic acrylic resins.
By weight alone, the solubility of the film-forming resin is poor or the volatile organic solvent having a boiling point exceeding 80 ° C. that does not dissolve the resin is 45-75% by weight and the boiling point of 120 ° C. is good for the solubility of the film-forming resin. Low volatile organic solvent exceeding 10-20
% Of the high-volatility organic solvent is vaporized at the opening of the nozzle when the discharge nozzle is at a stop of the paint discharge, and a film is formed on the paint surface to form the medium-volatile organic solvent and the low-volume organic solvent. A paint for an on-demand type dot printing device, characterized in that vaporization of a volatile organic solvent is suppressed to prevent drying of the paint in the opening.

Hereinafter, the configuration of the present invention will be described in more detail.

The inorganic coloring pigment, the film-forming resin and the volatile organic solvent used in the present invention can be selected and purchased from commercial products.
Except for a part of the volatile organic solvents (the above-mentioned medium volatile organic solvents having a boiling point of more than 80 ° C.), all of these volatile organic solvents are widely used as paints for dot printing devices for steel surfaces. .

The color of the inorganic color pigment used in the present invention is not particularly limited, but is preferably white from the viewpoint of visual visibility when printed on a steel material surface. Excellent titanium white is suitable. When the compounding ratio is less than 5% by weight, practical visibility is hardly obtained, and sufficient visibility is obtained in the range of 5 to 10% by weight. Therefore, it is not necessary to contain more than 10% by weight.

The film-forming resin used in the present invention is an ethyl cellulose resin, an acetyl butyl cellulose resin, a hydroxypropyl cellulose resin and a thermoplastic acrylic resin alone or as a mixture. These resins adhere well to the surface of the steel material and can easily select each specific volatile organic solvent used in the present invention. When the compounding ratio is less than 5% by weight, it is difficult to obtain a practical film strength, and
Since sufficient film strength can be obtained in the range of 10 to 10% by weight, it is not necessary to contain more than 10% by weight.

The selection of the specific volatile organic solvent used in the present invention and the mixing ratio thereof are important. In the present invention, the following three types, which are distinguished by the boiling point and the solubility of the specific film forming resin, are specified Must be used in proportion.

A. A highly volatile organic solvent having a boiling point of less than 80 ° C. with good solubility of the specific film-forming resin; for example, dichloromethane (boiling point 39.8 ° C.), acetone (boiling point 56.1 ° C.),
Methyl ethyl ketone (boiling point 79.6 ° C), methyl acetate (boiling point 57.8 ° C), ethyl acetate (boiling point 77.1 ° C), trichloroethane (boiling point 74.0 ° C). When the blending ratio is less than 5% by weight, the resin for forming the specific film cannot be dissolved, so that the paint cannot be formed. Is difficult to obtain the effect of preventing paint drying.

B. Either alone, the specific film-forming resin has poor solubility or is a medium volatile organic solvent having a boiling point exceeding 80 ° C. that does not dissolve the resin; for example, tetrachloroethylene (boiling point: 121.2 ° C.), butanol (boiling point: 117. 7
° C), 1-propanol (boiling point 97.2 ° C), 2-propanol (boiling point 82.4 ° C), toluene (boiling point 110.6 ° C)
° C), octane (boiling point: 125.7 ° C), nonane (boiling point: 15
0.8 ° C). When the blending ratio is less than 45% by weight, the effect of preventing paint drying at the opening of the discharge nozzle is difficult to obtain, and as the blending ratio increases, the effect is significantly improved. In this case, since the specific film-forming resin cannot be dissolved, it is impossible to paint.

C. A low-volatile organic solvent having a boiling point of more than 120 ° C. in which the specific film-forming resin has good solubility;
Ethoxyethanol (boiling point 135.6 ° C), 2-methoxyethanol (boiling point 124.6 ° C), 2-methoxyethanol acetate (boiling point 144.5 ° C), heptanone (boiling point 1
50.2 ° C.), cyclohexanone (bp 155.7 ° C.), butyl acetate (boiling point 126 ° C.). If the blending ratio is less than 10% by weight, the solubility of the film-forming resin is deteriorated and the adhesion of the printed coating film is reduced. If it exceeds 20% by weight, drying of the paint is too slow and the printed coating film is too slow. There is a risk of flowing.

The preparation of the paint according to the present invention is easy. Each of the above-mentioned materials is used within the range of each of the above-mentioned mixing ratios. The desired paint can be obtained by stirring until the specific film forming resin is completely dissolved.

[0023] The viscosity of the paint according to the present invention is determined by using a commercially available paint for dot printing apparatus intended for the surface of a steel material (for example, Tech Marker PLA:
Product name: Mark Tech Co., Ltd. and Tech Marker PS
The viscosity is preferably about 20 to 30 cP (centipoise), similarly to the viscosity of E75 (trade name: manufactured by Mark Tech Co., Ltd.).

[0024]

Next, representative embodiments of the present invention will be described.

7% by weight of an inorganic coloring pigment (anatase type titanium oxide having an average particle diameter of 0.7 μm: titanium white), 7% by weight of a thermoplastic acrylic resin (Dianal BR: trade name: manufactured by Mitsubishi Rayon Co., Ltd.) 5% by weight of a highly volatile organic solvent (dichloromethane: boiling point 39.8 ° C.) of the above-mentioned medium volatile organic solvent (tetrachloroethylene: boiling point 1211.
2 ° C.) and 71% by weight of the low-volatile organic solvent C (2-
A paint having a formulation consisting of 10% by weight of ethoxyethanol (boiling point: 135.6 ° C.) was prepared. The viscosity of this paint is 24 cP.

In the preparation means, each of the above-mentioned materials was put into a stainless steel tank, and stirred using a mixer until the resin was completely dissolved.

A commercially available on-demand type dot printing apparatus for steel materials (Paint Jet Printer TP3000: trade name: manufactured by Mark Tech Co., Ltd .: with a structure shown in FIG.
Dot diameter: 2.5 mmφ, dot pitch (interval between dots on the surface of the printing material): 3 mm, printing distance (ejection nozzle opening and printing target) Distance to the object): 20 mm, printing speed: 60 m / min, paint pressure: 2 MPa, material to be printed:
Rolled steel sheet and room temperature: Under each condition of about 20 ° C., letters and symbols were printed by a dot matrix using the above paint by the following procedure.

First, prior to the start of printing, idle printing is performed to discharge paint from all the discharge nozzles for about 0.5 seconds, and then the operation and pause of each discharge nozzle are repeated in accordance with the characters and symbols to be printed. The printing was stopped when characters and symbols in a dot matrix were continuously printed for one minute on the surface of the material to be printed, and left for 30 minutes. Subsequently, printing was continuously performed for one minute without performing the blanking operation.

No dot disturbance and clogging of the discharge nozzle opening occurred during the preceding continuous printing for one minute, and no dot disturbance and clogging of the discharge nozzle opening occurred during the subsequent continuous printing for one minute. .

Further, when the touch drying time (time from the time when the ejected dots adhere to the surface of the printing material to the time when the ejected dots do not stick to the finger) was measured for the coating film on the surface of the printing material, In the case of, it was 100 seconds.

The strength of the printed coating film was almost the same as that of the commercially available Tech Marker PLA or Tech Marker PSE75.

From the above results, it was confirmed that the paint according to the present invention can be sufficiently used for an on-demand type dot printing apparatus for steel materials.

[0033]

When the paint according to the present invention is used, as described above, even if the printing is resumed after being left for 30 minutes, the disturbance of the dots and the clogging of the ejection nozzle opening do not occur, and
The quick-drying property for practical use of a touch dry time of 100 seconds can be obtained, which can be said to be due to the following action.

That is, the paint according to the present invention contains the highly volatile organic solvent of the above A, the middle volatile organic solvent of the above B and the low volatile organic solvent of the above C at the above-mentioned specific ratio. Is present inside and outside the discharge nozzle opening in the resting state, the distal end portion of the discharge nozzle is open to the atmosphere.
The highly volatile organic solvent of the above-mentioned A in the paint existing near the outside vaporizes in a very short time, and
As the proportion of medium volatile organic solvent increases, the viscosity of the paint increases sharply. And since the evaporation of the volatile solvent occurs from the surface, the viscosity rise occurs on the paint surface,
A high-viscosity coating is formed on the surface of the paint existing inside and outside the opening of the discharge nozzle, and the coating suppresses the vaporization of the B volatile organic solvent and the C volatile organic solvent. Since the drying time of the paint is long and the fluidity is maintained for a long time, the discharge at the time of restarting can be performed smoothly.

When the paint is intermittently ejected from the ejection nozzle in a dot shape during operation, the diameter of the ejected dot (usually 2 to 3 mmφ) depends on the diameter of the ejection nozzle (usually 0.10 to 0). .25 mmφ) about 10 times or more,
Since the surface area of the discharged paint is increased, the medium volatile organic solvent B and the low volatile organic solvent C are also vaporized, so that the drying property of the printed coating film is not significantly affected.

In the practice of the present invention, an anti-settling agent (silica, organic bentonite, coupling agent, etc.) of an inorganic color pigment may be added to the paint formulation as required.
% By weight and a plasticizer (DBT, DOP,
1 to 3% by weight (TCP or the like) may be added, and in this case, the above-described effect can be obtained.

[0037]

EXAMPLES The present invention will be described below with reference to examples and comparative examples.

Example 1 Inorganic Color Pigment (Average Particle Size 0.7
μm anatase type titanium oxide: titanium white 700 g,
700 g of a thermoplastic acrylic resin (Dianal BR: trade name: manufactured by Mitsubishi Rayon Co., Ltd.), 1000 g of the highly volatile organic solvent of the above A (dichloromethane: boiling point 39.8 ° C.),
6,600 g of the above-mentioned medium volatile organic solvent B (tetrachloroethylene: boiling point: 121.2 ° C.) and 100 of the above low-volatile organic solvent of C (2-ethoxyethanol: boiling point: 135.6 ° C.) 100
0 g was placed in a stainless steel tank, and the mixture was stirred using a mixer until the resin was completely dissolved to prepare a paint. The viscosity of this paint is 22 cP.

The paint thus obtained and a commercially available on-demand type dot printing apparatus for steel materials (Paint Jet Printer TP3000: trade name: manufactured by Mark Tech Co., Ltd .: 32 discharge nozzles having a diameter of 0.2 mmφ and a structure shown in FIG. 1) ), And characters and symbols were printed by a dot matrix under the same conditions and procedures as those described in the above-mentioned [Embodiment of the Invention].

The result was the same as the result described in the above-mentioned [Embodiment of the invention] except that the touch drying time was 90 seconds.

Example 2 The amount of dichloromethane and the amount of tetrachloroethylene in Example 1 were changed to 1500 g and 6 g, respectively.
A paint was prepared in the same manner as in Example 1, except that the paint was changed to 100 g. The viscosity of this paint is 20c
P.

Using the paint obtained here and the on-demand type printing apparatus for steel materials used in Example 1, the dot matrix was prepared under the same conditions and procedures as those described in the above [Embodiment of the invention]. Letters and symbols were printed.

The result is the same as the result described in the above-mentioned [Embodiment of the invention] except that the touch drying time is 80 seconds and the ejection dots are disturbed during printing after leaving for 30 minutes. there were.

Therefore, except that the leaving time was changed to 25 minutes in the conditions and procedures described in the above-mentioned [Embodiment of the Invention], printing was performed under the same conditions and procedures as those conditions and procedures. No dot disturbance and no clogging of the ejection nozzle opening occurred in continuous one minute printing.

Comparative Example 1 The amount of dichloromethane in Example 1 was changed to 3200 g, and the amount of tetrachloroethylene was changed to 4
A paint was prepared in the same manner as in Example 1, except that the paint was changed to 400 g. The viscosity of this paint is 18c
P.

Using the paint obtained here and the on-demand type printing apparatus for steel materials used in Example 1, characters under a dot matrix were used under the same conditions as described in the above [Embodiment of the invention]. The symbols were printed according to the following procedure.

Prior to the start of printing, a blanking operation is performed to discharge paint from all the discharge nozzles for about 0.5 seconds, and then the repetition of the operation / pause of each discharge nozzle is controlled in accordance with the characters and symbols to be printed. The printing was stopped when characters and symbols in a dot matrix were continuously printed on the surface of the printing material for one minute, and left for 5 minutes. Next, when the printing was performed again for one continuous minute without performing the idling operation, the dot was disturbed in the subsequent printing for one continuous minute.

Printing was performed in the same procedure as above except that the leaving time was changed to 10 minutes. In the subsequent printing for 1 minute, the discharge nozzle openings were blocked in 32 of the discharge nozzles and paint could not be discharged. The required characters and symbols could not be printed. Printing was performed in the same procedure as described above, except that the leaving time was changed to 3 minutes. Even in the subsequent continuous printing for 1 minute, dot disturbance and clogging of the discharge nozzle opening did not occur.

In each case, the touch drying time of the printed coating film was 70 seconds.

Example 3 Inorganic Color Pigment (Average Particle Diameter 0.7
μm anatase type titanium oxide: titanium white) 1000
g, acetylbutylcellulose resin (CAB381: trade name: manufactured by Eastman Chemical Company) 1000 g, A
Of highly volatile organic solvents (acetone: boiling point 56.1 ° C) 150
0 g of the above-mentioned medium volatile organic solvent (2-propanol:
4,500 g of the above-mentioned low-volatile organic solvent of C (2-ethoxyethanol: boiling point: 135.6 ° C.) 200
0 g was placed in a stainless steel tank, and the mixture was stirred using a mixer until the resin was completely dissolved to prepare a paint. The viscosity of this paint is 23 cP.

Using the paint obtained here and the on-demand type dot printing apparatus for steel materials used in Example 1, the same conditions and procedures as those described in the above [Embodiment of the invention] are used.
The same procedure was used to print characters and symbols using a dot matrix.

The result was the same as the result described in the above-mentioned [Embodiment of the invention] except that the touch drying time was 120 seconds.

Example 4 The amount of acetylbutylcellulose resin in Example 3 was 700 g and the amount of acetone was 1
2,000 g, the amount of 2-propanol to 6000 g, 2
-A paint was prepared in the same manner as in Example 3, except that the amount of ethoxyethanol was changed to 1300 g. The viscosity of this paint is 26 cP.

Using the paint obtained here and the on-demand type printing apparatus for steel materials used in Example 1, the dot matrix was obtained under the same conditions and procedures as those described in the above [Embodiment of the Invention]. Letters and symbols were printed.

The result was the same as the result described in the above-mentioned [Embodiment of the present invention] except that the touch drying time was 110 seconds.

Example 5: The amount of titanium white in Example 3 was changed to 500 g, and the amount of acetylbutylcellulose resin was changed to 5 g.
A paint was prepared in the same manner as in Example 3, except that the amount of acetone was changed to 500 g, the amount of acetone was changed to 500 g, the amount of 2-propanol was changed to 7500 g, and the amount of 2-ethoxyethanol was changed to 1000 g. The viscosity of this paint is 30
cP.

Using the paint obtained here and the on-demand type printing apparatus for steel materials used in Example 1, the dot matrix was produced under the same conditions and procedures as those described in the above [Embodiment of the invention]. Letters and symbols were printed.

The result was the same as the result described in the above-mentioned [Embodiment of the invention] except that the touch drying time was 110 seconds.

Comparative Example 2 The amount of titanium white in Example 3 was set to 500 g, and the amount of acetylbutylcellulose resin was set to 5
00g, the amount of acetone was changed to 500g, the amount of 2-propanol was changed to 8000g, and the amount of 2-ethoxyethanol was changed to 500g. Each of these materials was put into a stainless steel tank, and mixed for 60 minutes using a mixer. Although the mixture was stirred, the resin could not be completely dissolved, and painting was impossible.

Example 6: Inorganic color pigment (average particle size 0.7
μm anatase type titanium oxide: titanium white 700 g,
Acetyl butyl cellulose resin (CAB 381: trade name: manufactured by Eastman Chemical Company) 500 g, thermoplastic acrylic resin (Dianal BR: trade name: manufactured by Mitsubishi Rayon Co., Ltd.) 500 g, highly volatile organic solvent of the above A (dichloromethane: boiling point 39) (1.8 ° C.) 1000 g, medium volatile organic solvent of the above B (tetrachloroethylene: boiling point: 121.2)
C) and 1,000 g of the low-volatile organic solvent of C (butyl acetate: boiling point: 126 ° C.) were put into a stainless steel tank, and stirred by using a mixer until the resin was completely dissolved to prepare a paint. The viscosity of this paint is 25 cP.

Using the paint obtained here and the on-demand type printing apparatus for steel materials used in Example 1, the dot matrix was produced under the same conditions and procedures as those described in the above [Embodiment of the Invention]. Letters and symbols were printed.

As a result, the touch dry time was 90 seconds, and the ejection dots were slightly disturbed during the printing after being left for 30 minutes (although slight disturbance was observed in the printed characters and symbols). , And could be clearly read visually)
Outside, the results were the same as those described in the above [Embodiment of the invention].

Example 7: The amount of tetrachloroethylene in Example 6 was changed to 5800 g, and the amount of butyl acetate was changed to 150.
A paint was prepared in the same manner as in Example 6, except that each was changed to 0 g. The viscosity of this paint is 24 cP.

Using the paint obtained here and the on-demand type printing apparatus for steel materials used in Example 1, the dot matrix was produced under the same conditions and procedures as those described in the above [Embodiment of the Invention]. Letters and symbols were printed.

The result was the same as the result described in the above-mentioned [Embodiment of the invention] except that the touch drying time was 100 seconds.

Example 8: The amount of tetrachlorethylene in Example 6 was changed to 5300 g, and the amount of butyl acetate was changed to 200 g.
A paint was prepared in the same manner as in Example 6, except that each was changed to 0 g. The viscosity of this paint is 24 cP.

Using the paint obtained here and the on-demand type printing apparatus for steel materials used in Example 1, the dot matrix was obtained under the same conditions and procedures as those described in the above [Embodiment of the invention]. Letters and symbols were printed.

The result was the same as the result described in the above-mentioned [Embodiment of the invention] except that the touch drying time was 110 seconds.

Comparative Example 3 The amount of dichloromethane and the amount of tetrachloroethylene in Example 6 were 3000 g and 2 g, respectively.
A paint was prepared in the same manner as in Example 6, except that the amount of butyl acetate was changed to 300 g and the amount of butyl acetate was changed to 3000 g. The viscosity of this paint is 20 cP.

Using the paint obtained here and the on-demand type printing apparatus for steel materials used in Example 1, characters under a dot matrix were used under the same conditions as those described in the above [Embodiment of the invention]. The symbols were printed according to the following procedure.

Prior to the start of printing, a blanking operation is performed to eject paint from all the ejection nozzles for about 0.5 seconds, and then the repetition of the operation and pause of each ejection nozzle is controlled in accordance with the characters and symbols to be printed. The printing was stopped when characters and symbols in a dot matrix were continuously printed on the surface of the printing material for one minute, and left for 5 minutes. Next, when the printing was performed again for one continuous minute without performing the idling operation, the dot was disturbed in the subsequent printing for one continuous minute.

When printing was performed in the same procedure as described above except that the leaving time was changed to 15 minutes, in the subsequent printing for one continuous minute, the discharge nozzle openings were clogged out of the 32 discharge nozzles and paint discharge was performed. Some of the characters and symbols could not be printed. Printing was performed in the same procedure as described above, except that the leaving time was changed to 3 minutes. Even in the subsequent continuous printing for 1 minute, dot disturbance and clogging of the discharge nozzle opening did not occur.

In each case, the touch drying time of the printed coating film was 180 seconds.

[0074]

As described above, when the paint according to the present invention is used in an on-demand type dot printing apparatus having a plurality of discharge nozzles for printing large dots on the surface of a large steel material, as seen in the embodiment, , Touch dry time 80 ~
Practical quick drying of 120 seconds can be obtained, and dot disturbance and clogging of the discharge nozzle opening do not occur during the operation of the apparatus.

In the paint according to the present invention, the drying time of the paint adhering to the vicinity of the opening of the discharge nozzle is extended by devising the paint prescription. This eliminates the need for empty beating work.

Therefore, it can be said that the industrial applicability of the present invention is very large.

[0077]

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a typical structure of a discharge nozzle employed in an on-demand type dot printing apparatus for steel materials.

[Explanation of symbols]

 Reference Signs List 1 discharge nozzle 2 nozzle opening 3 valve seat 4 spherical valve element 5 rod 6 movable iron core 7 paint chamber 8 return spring 9 solenoid coil 10 fixed iron core 11 paint pressure feed path

Claims (5)

[Claims] 1. A paint for an on-demand type dot printing apparatus having a plurality of discharge nozzles, comprising 5 to 10% by weight of an inorganic coloring pigment, ethyl cellulose resin, acetyl butyl cellulose resin, hydroxypropyl cellulose resin and thermoplastic acrylic. Film-forming resin 5 selected from resins
A boiling point of 8 to 10% by weight with good solubility of the film-forming resin
When used alone with 5 to 15% by weight of a highly volatile organic solvent of less than 0 ° C, the film-forming resin has poor solubility or does not dissolve the resin.
Weight% and good boiling point of 120 ° C.
10 to 20% by weight of a low-volatile organic solvent exceeding 10% by weight, and a film is formed on the paint surface when the high-volatile organic solvent vaporizes at the opening of the discharge nozzle while the discharge nozzle is at a standstill. A paint for an on-demand type dot printing device, characterized in that the evaporation of the medium volatile organic solvent and the low volatile organic solvent is suppressed to prevent the paint from drying in the opening. 2. A highly volatile organic solvent having a boiling point of 80 ° C. or less,
The paint for an on-demand type dot printing device according to claim 1, wherein the paint is any one of dichloromethane, acetone, methyl ethyl ketone, methyl acetate, ethyl acetate, and trichloroethane. 3. A medium-volatile organic solvent having a boiling point of 80 ° C. or higher, comprising tetrachloroethylene, butanol, 1-propanol,
The paint for an on-demand type dot printing device according to claim 1 or 2, which is any one of 2-propanol, toluene, octane and nonane. 4. A low-volatile organic solvent having a boiling point of 120 ° C. or more is 2-ethoxyethanol, 2-methoxyethanol,
The paint for an on-demand type dot printing apparatus according to any one of claims 1 to 3, wherein the paint is any one of -methoxyethanol acetate, heptanone, cyclohexanone, and butyl acetate. 5. The method according to claim 1, wherein the inorganic color pigment is titanium white.
5. The paint for an on-demand type dot printing device according to any one of items 1 to 4.