JPH11138090A - Device and method for evaluating coating operation properties - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating operation properties evaluation device for evaluating streaks generated at the time of paper coating for evaluating only the properties of a coating material simply and quantitatively without using paper. SOLUTION: A coating operation properties evaluation device is provided with a backing roll section 4, a roll rotation driving section of the roll 4, a coating material feed section 3 disposed in the vicinity of the roll 4, a blade section 5 disposed on the downstream of the coating material feed section 3 in the rotating direction of the roll 4 and being brought into contact with a roll face by the rotation of the face of the blade 5, a sensing section disposed on the downstream of the blade section 5 and a coating material measuring section disposed likewise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a coating material applied to base paper such as paper for the purpose of improving printability, in particular, to a blade coating suitability of a latex-containing coating material and coating defects generated during coating in a blade coating process. Particularly, streak-like coating defects (hereinafter, referred to as streaks) can be easily and easily formed.
The present invention relates to an evaluation device that can reliably evaluate.

[0002]

2. Description of the Related Art As a method of coating a paint on paper, plastic film, or the like, there is a blade coater method. This method is used by many paper companies because it is suitable for smoothly applying a small amount of paint to paper at high speed.
With this blade coater method, if the coating speed is increased or the coating amount is reduced, the coating will seep or precipitate on the blade edge and back side of the blade during coating, and the coated paper surface will be Contamination bleeding, portions where the amount of coating is insufficient are continuously generated, and operational defects such as streaks which become streak-like defects are likely to occur.

Therefore, when performing coating under new conditions,
Paper coating is carried out with an operating machine or a coater similar to an operating machine, and the suitability for coating and operability are confirmed. The coating aptitude and operability greatly vary depending on the flow characteristics of the paint, and the flow characteristics vary depending on the composition of the paint and the solid content concentration. Therefore, enormous manpower and time are required for selecting the paint. For this reason, operability evaluation using a bench-scale blade coater has been attempted. In addition, lab coaters that use a small amount of paint and finish coating in a short period of time have been evaluated for paint aptitude, but should be used for operability evaluation on actual machines due to the small equipment capacity. Can not.

There have been several reports on efforts to elucidate the bleeding phenomenon. JP-A-8-2669
Japanese Patent Publication No. 98 discloses an operability evaluation method in which a paint is directly applied to a backing roll and a bleeding phenomenon occurring at a blade edge is directly observed. In addition, research has been conducted to estimate occurrence of bleeding from liquid properties such as viscosity and dynamic viscoelasticity of a paint. For example, Vol. 49, No. 2 (1
Pp. 391 to 397, published February, 995), describes the bleeding phenomenon, entitled "A Consideration on Bleeding Phenomena in Blade Coating". On page 395, FIG. 5 shows the result that the lower the viscosity at the blade edge, the less bleeding occurs.

On the other hand, it is said that streak may be reduced by reducing the high shear viscosity and increasing the mechanical stability of the color. However, such a tendency is not always true, and no clear guideline has been disclosed yet. There are few books. Conventionally, there has been no other way than to prepare a paper coating liquid and actually apply it to paper with a pilot coater to check whether streaking occurs.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a simple and simple method for determining coating defects that occur during paper coating, especially for streaking, which is a streak-like coating defect, without actually using paper. It is an object of the present invention to provide a coating operability evaluation device which can be evaluated at low speed and an evaluation method using the same.

In this case, it is an object of the present invention to provide a coating operability evaluation apparatus which can reliably and quantitatively detect coating coating defects and an evaluation method using the same. Further, the present invention provides a coating operability evaluation apparatus and an evaluation method that can reliably and quantitatively evaluate coating defects that change from moment to moment and minute thickness changes that can be overlooked visually. Is also an issue.

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies and found that a coating operability evaluation apparatus provided with a specific detection mechanism has a coating defect at the time of paper coating. In particular, the present inventors have found that it is effective for easily evaluating the likelihood of occurrence of streaks, and have reached the present invention. That is, the present invention is as follows. 1. A backing roll portion having a backing roll made of metal or rubber or plastics, a rotation drive portion of the backing roll, a paint application portion disposed in close proximity to the backing roll, A detection unit disposed downstream of the paint application unit, the blade surface rotating and contacting the surface of the backing roll at a fixed angle, a detection unit disposed downstream of the blade unit with respect to the rotation direction of the backing roll, A coating operability evaluation device having a coating thickness measuring unit disposed downstream of the blade portion with respect to the rotation direction of the backing roll. 2. A backing roll portion made of metal or coated with rubber or plastics, and having a backing roll for directly applying a coating material on a roll surface, a rotation drive portion for rotating the backing roll, and the backing roll A paint application section for supplying and applying a paint to the blade, a blade section for adjusting the paint applied on the backing roll to a constant thickness, a detection section for detecting a coating defect generated in the blade section, and a coating section adjusted by the blade section. A coating operability evaluation device having a thickness measuring unit for measuring the thickness of a paint. 3. The detection unit is an optical detection unit that optically detects a coating defect. Or 2. Coating operability evaluation apparatus according to 4. 4. 2. The detection unit includes an image capturing unit that captures the coating defect as optical image data, and a data processing unit that binarizes the image data. Coating operability evaluation apparatus according to 4. 5.1. ~ 4. A method for evaluating the coating operability of a latex-containing paint using the apparatus according to any one of the above.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings. The backing roll section has a backing roll 4 made of metal or covered with rubber or plastics, and a supporting portion (not shown) of the backing roll 4. The backing roll 4 is for applying a paint directly on the backing roll surface, and plays a role in place of paper in a pilot coater test or the like conventionally used for evaluation of paper coating.

The material of the backing roll 4 is a metal itself or a metal coated with rubber or plastic. The material of the metal is not specified, but the surface is smooth and iron plated for corrosion protection.
Stainless steel or the like is used. The material of the rubber is not particularly limited, but urethane rubber having a JIS hardness A of 60 to 90 degrees is used. As the plastic coating, a method of winding a film such as polyethylene terephthalate on a metal roll can be used. In any case, the thickness is preferably 1 mm or more. The surface roughness can be appropriately determined according to the pigment size in the paint at the actual machine site, the roughness of the coated surface, and the like.

The size of the backing roll 4 can be appropriately determined in consideration of the fact that the paint does not fly due to the centrifugal force generated at the coating speed to be tested and the size appropriate for a laboratory apparatus. The working width may be any size as long as the size of the observation field of view can be ensured, but the working width can be appropriately determined while taking care not to be affected by the paint scraped off by the blade, since the paint tends to splash.

A rotation drive unit (not shown) of the backing roll 4 rotates the backing roll 4 in a predetermined direction in accordance with the direction of the blade 5. The rotation speed can be appropriately determined in consideration of the roll size and actual application conditions. The paint application unit is disposed close to the backing roll 4 and supplies and applies paint to the backing roll 4. The paint application section has an applicator roll 1 and a liquid receiving pan 2 containing paint 3. The applicator roll 1 is a mechanism that lifts the paint 3 from the liquid receiving pan 2 and supplies the paint 3 to the backing roll 4. The applicator roll 1 and the backing roll 4 need not be in contact, and the gap between the rolls can be changed. Also, the surface speed and the rotation direction of the applicator roll 1 can be changed,
The amount of paint supplied to the backing roll 4 can be set widely. In addition, the mechanism of these applications does not necessarily need to be a roll application method, and a conventionally known method such as a short dwell method, a fountain method, or a jet fountain method can be used as necessary.

Incidentally, the paint applied on the backing roll 4 accompanies the backing roll 4, reaches the applicator roll 1 again, and returns to the liquid receiving pan 2. Therefore,
The paint can be used repeatedly. The blade part
Blade 5, blade support 6, slide table 7,
It has a blade rotation shaft 14 and an angle gauge 9.

The blade portion is disposed downstream of the coating material application portion with respect to the rotation direction of the backing roll 4, and partially scrapes off the coating material excessively applied to the backing roll 4 in the coating material application portion to adjust it to a constant thickness. . The blade 5 may be a bevel blade that is rigid and has a tip with an inclined angle, or a bent blade that coats easily on a flexible surface. In particular, a bevel blade is generally used in high-speed coating. Hereinafter, a bevel blade will be described as an example.

The blade 5 is attached to the blade support 6 so that the free length a (FIG. 1) from the cutting edge to the clamping point has the same dimension in the width direction. This blade support 6
The entire structure is configured to rotate around a blade rotation shaft 14 installed parallel to the rotation axis of the backing roll 4, and the blade 5 can be set at an arbitrary angle with respect to the backing roll 4. The blade support 6 is attached to a slide table 7, and by sliding the slide table 7, the gap between the blade 5 and the backing roll 4 or the pressing force can be changed.

The blade 5 is straight until it comes into contact with the backing roll 4, but when the blade 5 is pressed against the backing roll 4 to scrape paint, the blade b
Occurs, and the working angle θ also changes (FIG. 2). If the change can be considered to be sufficiently small, it is not necessary to adjust the angle. However, in order to perform a strict evaluation, as shown in FIG.
More preferably, the displacement of the tip of the blade 5 is measured to determine the deflection b of the tip of the blade 5 during coating. Blade 5
The deflection angle φ at the tip can be determined from the relational expression between the deflection and the deflection angle by regarding the deformation of the blade as the straight deflection deformation of the beam. The working angle θ ₀ before the blade 5 contacts the backing roll 4 is read from the angle gauge 9 (FIG. 1). As described above, the working angle θ at the time of coating is determined from the deflection angle φ at the time of coating and the working angle θ ₀ before contact. With the blade support mechanism of the present apparatus, the position at which the tip contacts the backing roll 4 when the blade 5 is pressed changes, so that strictly θ = (θ ₀ −φ) is not achieved. Since the operation is performed in a region where the angle φ is very small, θ may be considered to be approximately equal to (θ ₀ −φ). The mechanism for determining the deflection angle φ of the blade tip does not necessarily need to use an optical displacement meter, but can also be obtained using a contact displacement meter or a strain gauge.

The coating thickness of the coating can be set in an arbitrary range depending on the coating speed. If it is too thin, the background color of the backing roll 4 and the scratches on the backing roll surface may be erroneously recognized as streaks. If it is too thick, the color may be scattered by centrifugal force depending on the coating speed. There is. Coating speed in actual machine is 100m
/ Min ~ 1500m / min.
The preferred coating thickness is from 10 to 200 μm.

The detecting unit 20 is disposed downstream of the blade 5 with respect to the rotation direction of the backing roll 4,
Detects coating defects, especially streaks, which are streak-like defects. As the detection unit 20, any of a contact type and a non-contact type can be used, but a non-contact type is preferable, and a type that can detect by an optical means is more preferable. For example, there is a method of detecting that the streak portion is thinner than the other coated surface by using a laser displacement meter.

Further, it is preferable that the detecting section 20 has a mechanism for quantifying the frequency of occurrence of streaks.
For example, it may be possible to count the number of streaks generated by the naked eye, but in combination with the above optical method, the streaks can be viewed in a unit field of view, the number of streaks generated per unit time, the length of time generated, the width of the generated streaks, etc. It is more preferable to have a mechanism for quantification by As a method of quantification, for each type of paint, the number of occurrences of streaks within a unit time, the total time that occurred, and the sum of the product of the generation time and the generation width are quantified and calculated. An example of performing processing is given. Thereby, it is possible to quantitatively compare the difference in the streak occurrence state depending on the type of the paint. Since the occurrence of streaks varies, and the situation changes one after another with time, evaluation with such a quantification mechanism makes evaluation much more reliable and simpler than evaluation based on visual observation alone. be able to.

More specifically, it is desirable that the detection unit 20 includes an image capturing unit that captures coating defects as optical image data, and a data processing unit that binarizes the image data. The image capturing unit captures the situation of a specific observation area on the backing roll surface as image data,
The data processing unit uses the image data to binarize the image data by utilizing the fact that when a streak defect occurs in a certain visual field, the color of the background of the roll appears at the portion, The shape defect is regarded as a black part. For example, when utilizing the difference between the color of the ground of the paint and the roll, the color of the ground of the roll represented by a defect in the paint surface (white) is binarized by image processing (to be black), and the white It quantifies the time, width, and frequency with which black appears in it. The threshold value for determining black is related to the roll, the color of the color, the intensity of light, and the like, and may be appropriately determined by preliminary experiments. If the threshold value is properly determined, streaks that can be missed by visual observation can be reliably detected.

The data processing section for binarizing image data may be provided separately from the image capturing section. When the observation field of view is enlarged by using the monitor microscope 13 as shown in FIG. 5, the occurrence state can be observed in more detail. Further, it is more preferable to record the occurrence status with a video camera in terms of data reliability. Of course, there is a method of once capturing an image as a video and analyzing the image later.

The paint thickness measuring unit 12 is disposed downstream of the blade 5 with respect to the rotation direction of the backing roll 4, and measures the coating thickness of the paint adjusted by the blade 5. It is desirable that the paint thickness measuring unit 12 use a non-contact optical displacement meter. Specifically, the surface position c of the backing roll 4 before coating and the position d of the coating film surface on the backing roll 4 after coating are measured with an optical displacement meter, and the coating thickness e is determined from the deviation. Is determined (FIG. 4).

The method of determining the coating thickness from the deviation is not particularly problematic when the backing roll 4 is sufficiently hard like a metal roll, but when the backing roll 4 is soft like a rubber-coated roll, the method for determining the coating thickness is close to the blade 5. The backing roll 4 is greatly deformed by the pressing of the blade 5, and a problem occurs in that the surface position of the backing roll 4 differs before and after pressing the blade 5. Therefore, it is preferable that the measurement of the surface of the backing roll 4 and the surface of the coating film be performed at a location sufficiently downstream from the blade 5 and at a location where the deformation of the backing roll 4 does not affect, as shown in FIG. , Coating rubber thickness 20mm,
Using a backing roll with a rubber hardness of JIS 90 degrees,
Coating speed of 100 to 50 for paint with viscosity of 20 to 100 cps
When applying at 0 m / min, the surface displacement is preferably measured at a position 350 mm downstream from the blade tip and 135 ° downstream at an angle).

The procedure of a coating operability evaluation method using the coating operability evaluation apparatus of the present invention is as follows. (1) Prepare a paint to be evaluated. (2) Directly on the backing roll maintained at a predetermined speed,
Apply paint. (3) Adjust the blade support and the slide table so that the liquid thickness and working angle are constant. (4) The frequency, width, and frequency of streak-like defects appearing on the backing roll in a state where the liquid thickness and the working angle have reached a predetermined value.
Observe the onset time.

If another abnormality occurs in the adjustment stage, the coating is stopped once, the blade edge and the back surface are cleaned, and the observation is performed again from (2). (5) The same adjustment is performed by changing the solid content concentration of the paint and the speed of the backing roll, and observation is performed. Through the above procedure, the occurrence state of the streak defect is grasped for each of the solid content concentration of the paint and the coating speed.

[0026]

According to the apparatus of the present invention, since paper is not used, equipment such as a winder, an unwinder, and a dryer as in an actual machine can be omitted.
The equipment load for evaluation can be greatly reduced. Efficient and time-consuming work such as paper threading and setting of drying conditions can be omitted, and efficient evaluation work can be performed. Since the paint can be reused, there is no need to prepare a large amount of paint for evaluation, and the cost required for evaluation can be greatly reduced. Since the coating thickness on the roll and the angle between the blade and the roll can be set to almost the same conditions as those of the operating machine, the evaluation can be performed with high reliability and reproducibility and with high efficiency. Since paper is not used, it is possible to evaluate the coating performance of the paint itself without being affected by the characteristics inherent to the base paper, such as the size and surface roughness of the paper. By mechanically detecting coating defects, it is possible to reliably and quantitatively catch coating defects in paint, making it possible to perform evaluations that were difficult with the conventional visual inspection, and are useful in evaluating the suitability and operability of paints. Information can be obtained. If the coating defect is captured as optical data, the coating surface can be detected in a non-contact manner, and the coating surface itself is not affected. Furthermore, if the optical data obtained from coating defects are binarized, coating defects that change every moment, and subtle changes in the thickness of the coating surface that can be overlooked especially by visual observation, can be reliably and quantitatively detected. Can be evaluated.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an example of an evaluation device of the present invention.

FIG. 2 is an enlarged schematic view of a portion where a blade 5 and a backing roll 4 come into contact with each other in the evaluation device of the present invention.

FIG. 3 is a conceptual diagram of a principle of measuring a bending deformation of a blade 5;

FIG. 4 is a conceptual diagram of a principle of online measurement of a coating thickness of a paint in a wet state in the evaluation device of the present invention.

FIG. 5 is an explanatory diagram of an example of arrangement positions of an optical displacement meter 12 for measuring a coating thickness, a monitor microscope 13 for observing a blade edge of a blade 5, and a coating defect detecting device 20.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Applicator roll 2 Liquid receiving pan 3 Paint 4 Backing roll 5 Blade 6 Blade support part 7 Slide table 8 Optical displacement meter (For deflection measurement) 9 Angle gauge 12 Optical displacement meter (For coating thickness measurement) 13 Monitor microscope 14 Rotary axis of blade support part 20 Detecting device for coating defect a Blade free length b Blade deflection c Backing roll surface position d Coating surface position e Coating thickness θ Working angle during coating (pressing force> 0) θ ₀ Working angle before blade contact (pressing force =
0) φ deflection angle

Claims (5)

[Claims] 1. A backing roll unit having a backing roll made of metal or coated with rubber or plastics, a rotation driving unit of the backing roll, a paint application unit disposed in close proximity to the backing roll,
A blade portion that is disposed downstream of the coating application portion with respect to the rotation direction of the backing roll, and a blade portion rotates and a blade surface contacts a surface of the backing roll at a fixed angle, and the blade portion with respect to the rotation direction of the backing roll. A coating operability evaluation apparatus comprising: a detection unit arranged downstream of the blade unit; and a paint thickness measurement unit arranged downstream of the blade unit with respect to the rotation direction of the backing roll. 2. A backing roll portion made of metal or coated with rubber or plastics and having a backing roll on which paint is applied directly on the roll surface, and a rotary drive for rotating the backing roll. Unit, a paint application unit for supplying and applying paint to the backing roll, a blade unit for adjusting the paint applied to the backing roll to a constant thickness, a detection unit for detecting a coating defect generated in the blade unit, the blade A coating operability evaluation device having a thickness measuring section for measuring the thickness of the paint adjusted in the section. 3. The coating operability evaluation device according to claim 1, wherein the detection unit is an optical detection unit that optically detects a coating defect. 4. The coating operability according to claim 3, wherein the optical detection unit has an image capturing unit that captures the coating defect as optical image data, and a data processing unit that binarizes the image data. Evaluation device. 5. A method for evaluating the coating operability of a latex-containing paint using the apparatus according to claim 1.