JPH08266998A - Evaluation of coating properties of paint - Google Patents

Abstract

PURPOSE: To simply evaluate the coating aptitude and operability of paint in blade coating by evaluating the coating properties of paint from the exudation and precipitation of paint at the edge of a blade at a time of coating and/or the presence of floc or the coating flaw of a roll surface. CONSTITUTION: An applicator roll 1 raises paint 3 from a liquid receiving pan 2 to supply the same to a backing roll 4 and the excessively supplied paint 3 is scraped off by a blade 5 to form a liquid film with predetermined thickness on the backing roll 4. As the blade, a rigid bevel blade having an angle of inclination provided to the leading end thereof is used and, as the backing roll 4 being a support, a metal roll or a roll covered with rubber is used. The angle formed by the blade 5 and the backing roll 4 and the liquid thickness applied to the roll 4 at a time of coating are made constant and the coating properties of the paint 3 is evaluated from the exudation and precipitation of the paint 3 at the edge of the blade at a time of coating and/or the presence of floc or the coating flaw of a roll surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paint applied to a base paper such as a paper for the purpose of improving printability, and more particularly to a technique for evaluating the coatability of a latex-containing paint and the operability of a coating process.

[0002]

2. Description of the Related Art A blade coater method is known as a method for coating a coating material on paper, plastic film or the like. This method is suitable for applying a small amount of paint evenly to high-speed moving paper, and is used by many paper manufacturing companies. This blade coater method, when the coating speed is faster or the coating amount is smaller, the coating exudes or deposits on the blade edge or the back side of the blade during coating, and the coated paper surface Operational defects such as polluting bleeding and streaks occur.

Therefore, when coating under new conditions,
Paper coating is performed with an operating machine or a coater similar to the operating machine, and the coating suitability and operability are confirmed. The coating suitability and operability vary greatly depending on the flow characteristics of the coating material, and the flow characteristics vary depending on the composition of the coating material and the solid content concentration. Therefore, a great deal of manpower and time are spent in selecting the coating material. Therefore, instead of actually applying paper, it is applied to the backing roll and a simple evaluation is performed to check the exudation of the paint on the blade edge of the blade, but reproducible results are obtained. Not not.

Further, evaluation of operability using a bench scale blade coater has been attempted, and further, even in a lab coater which uses a small amount of paint and finishes the coating in a short time, the coating suitability of the paint can be evaluated. Although it is evaluated, it is not used for evaluating operability such as the occurrence of operation defects. In the evaluation method of operability by backing roll coating described above, since the coating thickness on the backing roll has not been specified, it is not an evaluation with the same coating thickness, which is an evaluation method with poor reproducibility. ing.

Further, it is known that the angle between the blade and the support remarkably affects the occurrence of operational defects such as bleeding and streak, and a general bench scale blade coater is originally designed for coated paper. Since the purpose is to measure the quality, the angle between the blade and the support during coating cannot be controlled, so the operability of the operating machine cannot be reproduced well. Further, these operation defects require a time of tens of minutes to several hours for their manifestation, and therefore, such a phenomenon of operation defects cannot be confirmed even by a lab coater or the like which completes coating in a few seconds.

[0006]

DISCLOSURE OF THE INVENTION The present invention has improved the above-mentioned drawbacks of the prior art and applied it to a backing roll while keeping the coating thickness and the angle formed by the blade and the support constant, thereby exhibiting operational defects. It is intended to provide a method for easily evaluating the coating suitability and operability of a coating material in blade coating by observing the blade edge for a sufficient time.

[0007]

In order to solve the above-mentioned problems, according to the present invention, in addition to a backing roll consisting of a metal roll or a rubber coating roll, a roll driving device, a paint application section, coating of the applied paint is carried out. Coating is carried out using a device equipped with an instrument that measures the thickness online in the wet state and an instrument that measures the angle between the blade and the support (hereinafter referred to as the "working angle") online or offline. Evaluate sex.

The evaluation method of the present invention uses the above apparatus,
Apply the paint directly to the backing roll without using paper,
The operability is evaluated by observing the state of the blade edge and the back surface for several minutes under the condition that the liquid thickness and working angle are constant. The present invention can be generally applied to general paints, but is preferably applied to latex-containing paints. Next, the present invention will be described in detail using the apparatus shown in FIG.

In FIG. 1, reference numeral 1 denotes an applicator roll, which serves as a mechanism for lifting the paint 3 from the liquid receiving pan 2 and supplying it to the backing roll 4. The applicator roll and backing roll are not in contact,
The gap between the rolls can be changed. In addition, the surface speed and rotation direction of the applicator roll can be changed, and the amount of paint supplied to the backing roll can be set widely. It should be noted that the mechanism of these applications does not necessarily have to be the roll application system, and a short dwell system (FIG. 2) or a fountain system (FIG. 3) can be adopted as necessary.

The coating material excessively supplied from the applicator roll 1 is scraped off by the blade 5 to form a liquid film having a predetermined thickness on the backing roll. The blade uses a bevel blade that is rigid and has an inclined angle at the tip, and the free length a from the blade edge to the clamp location (Fig. 1)
Are attached to the blade supporting portion 6 so that they have the same size in the width direction. This blade support has a structure in which the blade rotates as a whole, and the blade can be set at an arbitrary angle with respect to the backing roll. Further, this blade supporting portion is attached to the slide table 7, and the gap between the blade and the backing roll or the pressing force can be changed by sliding the table.

The blade 5 is straight until it comes into contact with the backing roll 4, but when it is pressed against the backing roll to scrape off the paint, a deflection b occurs at the blade tip and the working angle θ also changes (FIG. 4). Therefore, in the present invention, as shown in FIG. 5, an optical displacement gauge 8 is attached to the blade supporting portion 6, the displacement of the blade tip is measured, and the deflection b of the blade tip during coating is obtained. The deflection angle φ of the blade tip was determined from the relation between the deflection and the deflection angle, regarding the deformation of the blade as the deflection deformation of a straight beam. The working angle θ0 before the blade contacts the backing roll is read from the angle gauge 9 (FIG. 1). As described above, the working angle θ during coating can be obtained from the deflection angle φ during coating and the working angle θ0 before contact. With the blade support mechanism of this device, the position where the tip contacts the roll changes when the blade is pressed.
= (Θ0-φ), but the actual coating is at a deflection angle φ
Is performed in a very small area, so θ≈ (θ0−
You can think of it as φ). It should be noted that the mechanism for obtaining the deflection angle φ of the blade edge does not necessarily need to use an optical displacement gauge, and can be obtained by using a contact displacement gauge or a strain gauge.

The coating thickness on the backing roll 3 is measured by an optical displacement meter 12. With an optical displacement meter attached to the evaluation device, the backing roll surface position c before coating and the position d of the coating surface on the backing roll after coating are measured,
The coating thickness e is determined from the deviation (Fig. 6).

The method of determining the coating thickness from the deviation is not a problem when the backing roll is sufficiently hard like a metal roll, but when the roll is soft like a rubber-coated roll, the roll near the blade is pressed against the blade. Due to the large deformation, the position of the roll surface is different before and after pressing the blade. Therefore, the surface of the roll and the surface of the coating film are measured sufficiently downstream from the blade, as shown in FIG. 7, at a place where the influence of the deformation of the roll does not affect (for example, diameter φ300 mm, coating rubber thickness 20).
mm, rubber hardness JIS 90 ° using a backing roll, a coating material having a viscosity of 20 to 100 cp and a coating speed of 100 to
In the case of coating at 500 m / min, the surface displacement was measured 350 mm downstream from the blade tip and 135 ° downstream in angle). The paint applied on the backing roll accompanies the backing roll, reaches the supply section by the applicator roll, and returns to the liquid receiving pan again, so the paint can be used repeatedly.

The procedure for evaluating the coating suitability and operability according to the present invention is as shown in the flow sheet of FIG. 8, and is as follows. 1. Prepare the paint to be evaluated. 2. The paint is applied directly to the backing roll, which is kept at a given speed. 3. Adjust the blade support and slide table so that the liquid thickness and working angle are constant. 4. The state of the blade tip and the back surface of the blade is observed with a predetermined liquid thickness and a working angle. It should be noted that the deposition state can be easily understood by using a monitor microscope 13 as shown in FIG. 7 for observing the cutting edge.

As a result of confirmation with a pilot coater similar to an operating machine, it takes at least 2 to 3 minutes until the coating deposits on the blade edge and the back surface of the blade to develop the operation defect. Therefore, the blade edge and the back surface of the blade cannot be observed. It is necessary to continue for about 3 to 5 minutes, preferably 5 minutes or more. On the contrary, by continuing the backing roll coating for a long time, it is possible to evaluate the denaturation of the paint and the easiness of wear of the blade edge. When paint is deposited on the blade edge and the back surface of the blade during the adjustment stage, the coating is once stopped, the blade edge and the back surface are cleaned, and then the observation is performed. 5. The solid content concentration of the paint and the speed of the backing roll are changed, and the same adjustment is performed and observation is performed.

Through the above procedure, the solid content concentration of the coating material, the coating suitability for each coating speed, and the operating limit are grasped. An observation example is shown in FIG. The symbols in the figure mean the following coating situations. ◯: Stable coating was possible Δ: Slight paint deposition (confirmed by monitor microscope; critical) X: Paint deposition was observed (visually confirmed)

From FIG. 9, it can be seen that when the solid content concentration of the coating material increases, operational defects occur even at a low coating speed. Further, in the case of evaluating the coating property by fixing the coating speed and sequentially changing the set value of the coating thickness, by operating the blade, the evaluation as shown in the flow sheet as shown in FIG. Just take steps.

[0018]

In the present invention, since the backing roll is coated and observed, the evaluation work can be easily performed without using paper. Further, since the paint can be used repeatedly, evaluation can be performed with a small amount of paint. In the present invention, since the coating thickness and working angle are strictly measured, it is possible to perform an evaluation that accurately reflects the operating conditions set in the operating machine. Further, in the conventional method, since the evaluation is performed while the coating thickness and working angle, which have not been sufficiently controlled, are kept constant, reproducible results can be obtained.

Since the coating thickness and working angle are measured online, the target value can be reached relatively easily. Since the evaluation according to the present invention does not include the influence of the base paper which is said to be greatly involved in the coating suitability and operability, the characteristics of the paint itself excluding the influence of the base paper are directly evaluated. be able to.

[0020]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Example 1 Pigments, binders, and additives were mixed in the composition shown in Table 1 and dispersed in water to prepare three kinds of paints.
With respect to one kind of paint, the solid content concentration was divided into three kinds to prepare paints having almost the same viscosity. The flow characteristics of each paint (dependence of viscosity on shear rate) are shown in FIG.

[0021]

[Table 1]

These coating materials were applied to a backing roll using the evaluation coater of the present invention, and the presence or absence of the occurrence of operational defects was observed. When the operation defect did not appear, the coating speed was increased and the same experiment was conducted. The tested coating speed is in the range of 100 to 500 m / min.

When the limit coating speed at which the operation defect starts to occur is plotted against the coating viscosity at the shearing speed at the time of coating, it becomes as shown in FIG. 12. As the coating viscosity increases, the operation defect starts from the lower speed region. Was observed to occur. This tendency is a phenomenon generally recognized in operating machines. However, even with the same paint viscosity, the result that the speed at which operation defects occur is different between paints with different formulations,
It suggests that the operating limit cannot be grasped only by the paint viscosity.

(Reference Example 1) When the same coating material as in Example 1 was used to coat paper with a pilot coater similar to an operating machine, precipitation on the blade edge was observed. The relationship between the coating viscosity and the coating speed at the operating limit is as shown in FIG. 12, and the results of paper coating by the pilot coater were almost the same as those of the evaluation coater of the present invention.

As is clear from Example 1 and Reference Example 1,
Regarding the relationship between the coating viscosity and the coating speed at the operating limit, the results of paper coating by a pilot coater and the results of backing roll coating by the evaluation coater of the present invention are almost the same. Further, the relative superiority and inferiority of operability between paints having different formulations is the same in both paper coating and backing roll coating of the present invention. From this, it can be seen that the evaluation coater of the present invention can judge the superiority or inferiority regarding the operability of the paint, like the operating machine.

Example 2 By the same method as in Example 1, the angle formed by the blade and the roll was changed, and the deposition of the blade edge was observed. When the angle formed by the blade and the roll was made smaller and the gap between the lower surface of the blade and the roll became wider toward the downstream side, that is, in the so-called heel contact state, operation defects began to appear even if the coating speed was slow. On the contrary, when the angle formed by the blade and the roll was increased, the operation defect was not easily recognized even when the coating speed was increased, and it was found that the operation limit was significantly affected by the angle formed by the blade and the roll.

Example 3 Using the same method as in Example 1, the coating thickness was changed and the deposition of the blade edge was observed. When the coating thickness was thin, operational defects began to appear while the coating speed was relatively slow (Fig. 13). On the other hand, when the coating thickness was increased, it was found that even if the coating speed was increased, operating defects did not readily appear, and the operating limit was significantly affected by the coating thickness. As is clear from Examples 2 and 3, the occurrence of operational defects is significantly affected not only by the viscosity of the paint and the coating speed but also by the working angle and the coating thickness. , It is understood that it is necessary to make the working angle and coating thickness uniform.

[0028]

INDUSTRIAL APPLICABILITY In the present invention, in a method for evaluating the coating suitability and operability of a paint, since the backing roll is coated and evaluated without using paper, equipment such as a winder, an unwinder, and a dryer is used. It can be omitted and the equipment load for evaluation can be greatly reduced.Since paper is not used, complicated and troublesome work such as threading paper and setting drying conditions can be omitted, and efficient evaluation work can be performed. Since the base paper for evaluation and the heat source necessary for drying are unnecessary and it is not necessary to prepare a large amount of paint, the cost required for evaluation can be greatly reduced, the coating thickness on the roll, and the blade Since the angle formed by the rolls is set to almost the same conditions as the operating machine and is closely monitored, the evaluation is highly reliable and reproducible, and the evaluation work can be carried out with high efficiency. Not to use Without being affected by the base paper inherent properties such as sizing degree and surface roughness, it is possible to evaluate coating performance of the coating, an effect that.
As described above, by using the evaluation method of the present invention, the coating suitability and operability of the coating material can be easily grasped, and a coating material of good quality can be provided for stable coating.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an evaluation device for carrying out an evaluation method according to the present invention.

FIG. 2 is a schematic diagram of an evaluation device in which the application mechanism for implementing the evaluation method of the present invention is a short dwell method.

FIG. 3 is a schematic diagram in which an application mechanism for implementing the evaluation method of the present invention is a fountain type evaluation device.

FIG. 4 is an explanatory diagram of an angle (working angle) formed by a blade and a support in the evaluation method of the present invention.

FIG. 5 is an explanatory diagram of the principle of measuring the deflection of a blade.

FIG. 6 is an explanatory diagram of the principle of online measurement of the coating thickness of the paint in a wet state in the evaluation method according to the present invention.

FIG. 7 is an explanatory diagram of an arrangement example of an optical displacement meter for measuring a coating thickness and a monitor microscope for observing a blade edge.

FIG. 8 is a flowchart showing a coating test in which the coating thickness is fixed and the coating speed setting value is sequentially changed.

FIG. 9 shows the results of the operability evaluation performed by the evaluation device for carrying out the evaluation method according to the present invention and the coater for operating machine.
The coating conditions at each solid content concentration and coating speed are shown.

FIG. 10 is a flowchart showing a coating test in which the coating speed is fixed and the set value of the coating thickness is sequentially changed.

FIG. 11 shows the flow characteristics of the coating materials used in Examples 1 and 2 and Reference Example 1.

FIG. 12 is a plot of the limit coating speed with respect to the paint viscosity, based on the results of the operability evaluation performed by the evaluation device according to the present invention and the coater for operating machines.

FIG. 13 is a graph showing whether or not the workability is good or bad by plotting the coating speed and the coating thickness from the result of the workability evaluation performed by the coater for operating machine.

[Explanation of symbols]

 1 Applicator Roll 2 Liquid Receiving Pan 3 Paint 4 Backing Roll 5 Blade 6 Blade Support 7 Slide Table 8 Optical Displacement Meter (For Deflection Measurement) 9 Angle Gauge 10 Short Dwell 11 Fountain Nozzle 12 Optical Displacement Meter (Coating Thickness Measurement) 13) Monitor Microscope

Claims (3)

[Claims] 1. A method for evaluating the coatability of a coating material in a blade coating method, wherein a coating material supplied from an applicator to a support is scraped to a predetermined thickness with a blade, and a metal roll or a roll coated with rubber is used as the support. Using, the angle between the blade and the roll at the time of coating and the thickness of the liquid applied to the roll is constant, the exudation of the coating material at the blade edge of the blade at the time of coating, the presence or absence of precipitates and / or aggregates, or the roll A method to evaluate the coating property of paint from the coating defects on the surface. 2. A method for evaluating the coatability of a coating composition according to claim 1, wherein the coating thickness is fixed and
A method of evaluating the coating properties of paint by changing the coating speed setting value. 3. A method for evaluating the coatability of a coating composition according to claim 1, wherein the coating speed is fixed and
A method to evaluate the coating properties of paint by changing the set value of coating thickness.