JP2007069154A - Coating apparatus and coating sheet produced by coating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating apparatus which does not generate a coating defect and a quality decrease even in fast operations when a coating liquid is applied on the surface of a web which is supported by a backing roll and continuously runs by a blade coating process in which the coating liquid is blown out from a slitted nozzle, to form and supply a coating liquid jet. <P>SOLUTION: In the blade coating process in which the coating liquid is blown out from the slitted nozzle 11a to form and supply the coating liquid jet and applied on the surface of the web 33 which is supported by the backing roll 31 and continuously runs, an accompanying air accompanying the web is removed by arranging an air drafting apparatus 21 having a plurality of ducts which have slitted duct openings in the nearly parallel direction to the width direction of the web so that air is drafted nearly to the vertical direction to the web progressing direction, with the starting point of the air drafting apparatus 21 being positioned 3 to 100 mm upstream of a place where the coating liquid collides with the web. Therefore, the coating apparatus does not generate the coating defect and the quality decrease. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, a coating liquid is blown from a slit-like nozzle and supplied to a surface of a web that is continuously supported by a backing roll, such as a coating apparatus called a jet fountain type. When coating with the blade coating method, a coating device that is excellent in operability even during high-speed operation and that does not cause coating defects or deterioration in quality, and a coating manufactured by the coating device It relates to the sheet.

  A number of methods have been proposed for industrially applying webs continuously. In particular, blade coating is often used in the paper pulp field. This is because the coated paper obtained by the blade coating method is superior in terms of the quality of blank paper and printing quality compared to other coating methods, and the operational aspect of being able to operate stably at high speed. It depends.

  In the blade coating method, the coating liquid supplied excessively on the web is scraped off the excess coating liquid mainly by closely contacting and pressing a metal blade (hereinafter referred to as a measuring blade). Weigh to the coating amount. Before the measurement by the blade, there is an application section for supplying the coating liquid to the web. As the type of the application section, the web is brought into contact with a color pan in which the coating liquid is accumulated, and the coating is applied on the web. Color pan supply system for supplying the working liquid, roll supply system for supplying the coating liquid on the web from a group of rolls composed of single or multiple rolls partially immersed in the color pan, uniform in the width direction There is a jet supply system that discharges the coating liquid with a certain angle with respect to the web traveling direction from between the slits having a gap, but uniform supply of the coating liquid in the width direction and the flow direction on the web, In terms of handling high-speed coating, the blade coating method supplied by the jet supply method, such as the free jet type or jet fountain type exemplified in Patent Document 1, is the most. It can be said that a flow.

Japanese Utility Model Publication No. 2003-159548

  Various problems such as streaks, skip coats, etc. are known as coating problems in blade coaters, such as web breaks, poor coating amount profile, or streaks that appear not to be coated locally. As the coating speed increases, problems such as poor transfer surface and backflow, which will be described below, and operational problems or quality problems induced by these have come to be seen. .

  In the blade coating method, the coating solution supplied by the jet supply method collides with the web supported by the backing roll, and then the excess coating solution is scraped off by the measuring blade. In such a state, the coating liquid on the web from the web collision point of the coating liquid to the blade measuring section has a uniform wet coating liquid amount, and thus has a surface feeling close to a mirror surface. Transfer surface failure means that the unmeasured web coating liquid surface, which is essentially close to a mirror surface, becomes rough, resulting in deterioration of the web coating amount profile or uncoated parts. To tell.

  As a result of investigations by the inventors, the largest cause of transfer surface failure is that the coating liquid supplied by the jet supply method has been accompanied by the web when it collides with the web supported by the backing roll. It was determined that the air layer (hereinafter referred to as the entrained air layer) was caused by pushing the coating liquid jet downstream and at the same time entering the space between the web and the coating liquid.

  As a method for resolving transfer surface defects, empirically, the amount of paint discharged from the slit-shaped nozzle is increased, the collision angle of the coating liquid jet to the web is increased, or the slit of the slit-shaped nozzle that discharges the coating liquid A method has been adopted in which the collision energy in the direction perpendicular to the web traveling direction is increased by increasing the discharge speed by narrowing the interval, thereby inhibiting the entrainment of the entrained air layer. However, with the recent increase in coating speed, there is a limit to these countermeasures, and furthermore, the above countermeasures are such that when the coating liquid jet collides with the web, the coating liquid is applied in the horizontal direction to the web. The effect is limited because it leads to easy scattering, and this causes a new operational problem called backflow.

  The above-described backflow is considered to be likely to occur when the high-speed coating is supported as described below, based on the results of studies by the inventors. In other words, when a coating solution with the same viscosity is applied by the blade coating method under the same coating conditions, the coating amount increases as the coating speed increases. It is necessary to increase the pressing pressure of the blade. However, there is an upper limit to the blade pressing pressure, and the risk of the web becoming broken and becoming unable to operate due to an increase in the blade pressing pressure increases dramatically. For this reason, since it is necessary to reduce the so-called high shear viscosity in order to control to a desired coating amount, a method of reducing the viscosity by reducing the solid content concentration of the coating liquid can be taken. Since the coating liquid supply amount must be increased in proportion to the decrease and the coating speed increase, when the coating liquid jet collides with the web, the collision energy is too large, causing the coating liquid to move in the horizontal direction. As a result, a backflow occurs, resulting in hindrance to operability. Also, due to the occurrence of backflow, the paint scattered before the coating liquid jet collision point is transferred to the web and deteriorates the quality of the product, or the scattered paint solidifies and accumulates on the measuring blade. The occurrence of backflow, such as causing coating defects such as streaks, results in not only a reduction in operability but also a reduction in quality, and a solution is desired.

  Up to now, several apparatus-like measures have been proposed as solutions for transfer surface defects and backflow. For example, regarding improvement of transfer surface defects caused by entrained air, for example, Patent Document 2 discloses a method of blowing an air jet in a direction opposite to the web traveling direction just before a point where the coating liquid jet collides with the web. For example, Patent Document 3 discloses a method for providing an air ejection mechanism that is integrated with the coating liquid ejection unit and that can vary the ejection amount and ejection angle. A steam spray mechanism is added to the method in which an air jet in the direction opposite to the web traveling direction is blown just before the point where the coating liquid jet collides with the web, and the air in the entrained air layer (hereinafter referred to as entrained air) is replaced with steam. For example, Patent Document 4 discloses a method of causing the above to occur. For example, Patent Document 5 discloses a method of installing a suction device in the vicinity of a web after forming a coating liquid jet under specific conditions. Further, for example, Patent Document 6 discloses a method of blowing air from the upstream side of the web toward the traveling direction of the web toward the point where the coating liquid jet collides with the web. .

  However, in the jet supply method, the coating liquid may not be transferred to the entire web due to fluctuations in the paint discharge state. In severe cases, the state becomes close to the backflow described above. Among the improvement proposals for the above device, regarding the method for improving the transfer surface defect caused by entrained air, in the method of blowing an air jet in the direction opposite to the web traveling direction, when the backflow occurs and the coating liquid is scattered, The scattered coating liquid is transferred onto the web before the coating liquid jet collides, deteriorating the coating amount profile, deteriorating the appearance and print quality of the product, and increasing the frequency of cleaning during operation. . In addition, the method of replacing the entrained air with water vapor is expected to have a certain effect in preventing the coating amount profile deterioration due to the entrained air and preventing the skip coating. There is a possibility that the printing quality is deteriorated due to spots or the like, or printing trouble is caused. The method of installing a suction device near the web after forming a coating liquid jet under specific conditions is inferior in the effect of removing entrained air during high-speed coating, and uses a smooth web with an undercoat layer. In some cases, when backflow occurs due to fluctuations in operating factors, the dried coating liquid may accumulate on the suction device, making operation impossible. It is the same as the above-mentioned method that the backflow is not dealt with. In addition, regarding the method for improving the backflow, the method of blowing air from the upstream side of the web toward the point where the coating liquid jet collides with the web can be expected to have a certain effect in suppressing the occurrence of backflow, but the transfer surface is poor. As a result, a satisfactory result cannot be obtained. As described above, there has not yet been proposed a method for simultaneously satisfying the improvement of the transfer surface defect caused by the accompanying air and the countermeasure against the backflow.

Japanese Utility Model Publication No. 1-20244 Japanese Utility Model Publication No. 5-39680 JP 2001-38271 A Japanese Patent Laid-Open No. 10-43661 JP 7-256184 A

  At the point where the jet supply type blade coating method coating liquid jet collides with the base paper, the angle formed between the web before the coating solution is supplied and the coating solution jet is less than 90 degrees, usually 30 to The coating liquid jet collides with the base paper at an angle of about 60 degrees. In the wedge-shaped part near the collision point, the air layer accompanying the web tends to concentrate. However, considering the impact speed of the coating liquid on the web, the jet supply blade coating system, which is a pressure / discharge type and supplies a coating liquid of 10 times or more the desired coating amount, The impact energy on the web is very high. For this reason, in the case of a jet-feed blade coating system, if the coating speed is about 1000 m / min or less without special measures so far, the operation due to the occurrence of a transfer surface defect due to entrained air It is estimated that the quality problem was difficult to be revealed.

  Furthermore, for example, when the smoothness of the base paper is improved in order to improve the quality of the obtained coated paper, the unevenness of the web surface is lowered, so that the coating liquid supplied on the web is moved in the web traveling direction by the unevenness. The present inventors have inferred that the effect of pulling is reduced, and as a result, the coating liquid tends to spread in the direction opposite to the traveling direction, leading to a state where backflow is likely to occur. Operational problems such as transfer surface defects and backflow may be scattered by improving the smoothness of the base paper, further improving the coating speed in recent years, or reducing the viscosity of the coating liquid for high-speed coating. The present inventors think that it is becoming.

  Since the flow velocity in the web traveling direction of the entrained air accompanying the web can be considered to be almost the same as the plate boundary layer flow velocity distribution equation, if the moving speed of the web increases due to an increase in the coating speed, the accompanying air Not only will the flow velocity increase, but the thickness of the air layer with a flow velocity close to that of the moving web will increase, and the kinetic energy of the air flow impinging on the point where the coating liquid jet will collide with the web will also increase. It will be. The thickness of the entrained air layer is several mm or less, but since the flow velocity is very large, it is considered that the entrained air having a slight thickness greatly affects the operability. However, it has been difficult to completely block the high-speed entrained air layer with the counter-air method and the decompression method that have been proposed so far.

  As described above, in the blade coating method of the jet supply method in which the coating liquid is supplied from the slit-like nozzle to form a blown coating liquid jet on the surface of the web continuously supported by the backing roll, There was still room for improvement as a coating apparatus for obtaining a high-quality product having high speed and good operability and no coating defects.

  Therefore, the present invention is a jet supply type blade coating method in which a coating liquid is formed from a slit-like nozzle to form a blown coating liquid jet and supplied to the surface of a web that is continuously supported by a backing roll. Coating is performed by a coating device and a coating device that are excellent in operability without causing coating defects or quality deterioration due to transfer surface defects or backflow even during high-speed operation. It is an object to provide a coated sheet.

The coating apparatus according to the present invention is a coating apparatus that applies a coating liquid to the surface of a web that is continuously supported by a backing roll,
A coating liquid supply unit that has a slit-like nozzle opening, blows a coating liquid from the nozzle opening, and forms a coating liquid jet, and is applied to a web running from the nozzle opening. A coating liquid supply unit arranged so that the distance to the working liquid collision point is in the range of 5 to 700 mm;
A plurality of ducts having slit-shaped duct openings starting from 3 to 100 mm upstream of the web from the point where the coating liquid collides with the web (hereinafter, a plurality of slit-shaped ducts provided in the air suction device) An air suction device having an opening (sometimes referred to simply as a duct opening) has a slit in the width direction connected to an air suction pipe portion that sucks air in a substantially vertical direction with respect to the web traveling direction. An air suction device and an accompanying air removing means;
A measuring unit that is disposed on the downstream side of the web with respect to the coating liquid collision point to the web and scrapes the coated coating liquid,
It is a coating apparatus which has.

Furthermore, it is preferable that the curvature radius R1 of the web facing surface of the air suction device satisfies the following expression (1) with respect to the backing roll radius R2.
1.0 ≦ R1 / R2 ≦ 1.035 Formula (1)
The surface with which the coating liquid of the air suction device may come into contact is preferably a water repellent surface.
As the web-side tip shape of the duct partition wall of the air suction device, it is preferable that the upstream side surface tip of the duct partition wall has an L-shape that protrudes upstream, and the downstream end of the duct partition wall is chamfered. It is preferably formed by a rounded corner or a smooth curved surface.

Further, the first inflow air inhibiting means for inhibiting the accompanying air origin air flow on the side of the accompanying air removing means that is the origin of the redevelopment of the accompanying air downstream from the accompanying air removing means is a downstream side surface of the accompanying air removing means. It is preferable to arrange at least one.
Furthermore, the second inflow air inhibiting means for inhibiting the entrained air origin air flow on the side of the coating liquid jet supply part which is the origin of the redevelopment of the entrained air downstream of the entrained air removing means has a slit-like nozzle It is preferable to arrange at least one upstream of the side surface of the coating liquid jet supply unit.

  The coating sheet according to the present invention is a coating sheet in which a coating layer mainly composed of a pigment and / or an adhesive is provided on at least one surface of a sheet-like substrate by the coating apparatus as described above. is there.

  Even during high-speed operation, the coating apparatus has excellent operability without causing coating defects or quality deterioration due to transfer surface defects or backflow. The obtained coated sheet was also free from coating defects and quality degradation.

An example of the coating apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an example of a coating apparatus according to the present invention. This coating apparatus is a coating apparatus of a blade coating system of a coating liquid jet supply system. The web 33 is continuously running supported by the backing roll 31. The coating liquid jet supply unit 11 supplies the coating liquid to the surface of the web 33 by forming a blown coating liquid jet 13 from the slit nozzle 11 a. The leading end 21a on the downstream side in the web traveling direction of the air suction device 21, which is the main component of the accompanying air removing means, starts from the upstream side (3 to 100 mm) of the web from the point C where the coating liquid collides with the web. Is arranged. FIG. 2 shows the relationship between the coating liquid jet supply unit 11 and the backing roll 31 in more detail in FIG. FIG. 2 is an enlarged cross-sectional view showing only the relationship between the coating liquid jet supply unit 11 and the backing roll 31. The distance from the slit-shaped nozzle tip 11a to the coating liquid collision point C on the running web is represented by d.
In FIG. 1, the coating liquid jet 13 adheres to the surface of the web 33, and the coating layer 13a is formed. Since the coating layer 13a is formed in an excessive thickness, the excess is scraped off by a measuring blade 15 constituting a measuring unit disposed at the rear to form a desired coating layer 13b.

  As described above, the coating liquid jet supply system is affected by the air layer on the web surface that moves at high speed when supplying the coating liquid onto the web, and causes operational problems such as transfer surface defects and backflow. In addition to this, the occurrence of uncoated areas, coating amount profile defects, blank paper and printing quality defects may be induced. The inventors considered that these problems can be solved by efficiently removing the air layer accompanying the web, and conducted various studies. As a result, it has been concluded that it is extremely effective to provide a specific air suction-type accompanying air removing means for removing the air layer accompanying the web.

  That is, by removing the entrained air, the entrained air can be prevented from entering between the web and the coating liquid at the point where the coating liquid jet collides with the web, and as a result, the transfer surface defect can be effectively prevented. Can be prevented. Therefore, as a countermeasure when a transfer surface defect occurs, the discharge speed is increased by increasing the discharge amount of the coating liquid jet, increasing the coating liquid jet collision angle, or narrowing the slit interval of the slit-like nozzle for discharging the coating liquid. It has been found that the occurrence of backflow can be effectively prevented. In addition, with the method of the present invention, when applying high-quality coating sheets and high-speed coating, the coating of highly smooth webs before coating and coating of low-viscosity coating liquids are also possible. It became clear that there was a backflow suppression effect.

  An air suction device having a plurality of ducts having slit-like duct openings parallel to the width direction of the web is used as a main component of the accompanying air removing means. An air suction device, which will be described later, is connected to this air suction device to constitute the accompanying air removal means. As the installation position of the air suction device 21, as shown in FIG. 1, it is necessary to start 3-100 mm upstream of the web from the point C where the coating liquid collides with the web. The starting point of the air suction device referred to in the present invention is the web collision of the coating liquid jet among the ends of the air suction device installed along the web supported by the backing roll as shown in FIG. The backing roll side position on the point C side is shown, and the air suction device actually covers the web on the backing roll at a distance obtained by adding the length of the suction suction device from the starting point. When the coating point of the coating liquid jet on the base paper is less than 3 mm upstream of the point where the coating liquid collides with the web as the installation position, the coating liquid changes when the collision point of the coating liquid jet on the base paper changes due to operational fluctuation factors. The jet may come into contact with the entrained air removal device, leading to a decrease in operability. On the other hand, if the position is more than 100 mm upstream of the web from the point where the coating liquid collides with the web, the effect of removing the entrained air is inferior and the desired effect of the present invention cannot be obtained. In addition, since the entrainment air removal efficiency increases when it is 3-50 mm upstream from the point where the coating liquid collides with the web as the installation position of the accompanying air removing means, the point where the coating liquid collides with the web If it is installed 5-30 mm upstream of the web, it is more preferable because the entrained air removal efficiency is most enhanced and the operability is good.

  When the distance d from the slit-shaped nozzle tip of the coating liquid jet supply unit to the coating liquid collision point on the running web indicated by the symbol d in FIG. 2 is too small, the slit-shaped nozzle May contact the web or splice tape used to connect the webs, causing web breakage or coating defects. If d is too large, the web of the coating liquid jet Since the state of collision with may become unstable, d needs to be 5 to 700 mm. In order to stabilize the flow of the coating liquid jet, the upper limit value of d is preferably 500 mm or less, and in order to further increase the stability, the lower limit value of d is more preferably 10 mm or more, and the upper limit value of d. More preferably, the value is 200 mm or less.

  As the accompanying air removing means, an air suction device having a plurality of ducts having slit-like openings is used in order to efficiently remove accompanying air during high-speed coating. Moreover, about the distance of the web opposing surface (FIG. 3 code | symbol 25c) of this air suction apparatus and the web on a backing roll, it is preferable in it being 1-30 mm. By the way, if the distance is less than 1 mm, there is a risk of contact with the air suction device when the continuous web or a splice tape used for connecting the web passes through the seam. -It is not preferable in terms of quality and operation because it may cause deformation or breakage of the web. On the other hand, when the distance exceeds 30 mm, no matter how large the suction degree of the air suction device is, it is inferior in the effect of removing entrained air at high-speed coating, and the quality of the obtained coated product is lowered or operability is lowered. . In order to improve operability and entrained air removal efficiency, the distance between the web facing surface of the air suction device and the web on the backing roll is more preferably 2 to 15 mm, and further preferably 2 to 10 mm.

  In addition, the present invention is characterized in that the air suction device includes a plurality of ducts so as to suck air in a substantially vertical direction with respect to the web traveling direction. The air suction device for removing entrained air in the present invention sucks air from a slit-like opening at the tip of a plurality of ducts. Therefore, a plurality of slit-like openings are arranged in the web traveling direction on the web facing surface of the air suction device. Since the respective ducts are substantially perpendicular to the traveling direction of the web, the accompanying air suction efficiency can be improved. The shape of the duct is not particularly limited, and it is a structure in which very short ducts are bundled and converged to one duct from the middle, and the duct is gradually narrowed in the width direction of the web to be substantially cylindrical. A structure that finally converges each duct, a structure in which a plurality of ducts are stretched almost as they are, and a duct partition wall between the ducts is eliminated at the end of the air suction device so that only the outer wall is constructed. A structure in which these are appropriately combined can be considered.

  FIG. 3 shows an example of an air suction device and a partial cross-sectional view of the periphery thereof. The air suction device 21 has a plurality of ducts D, D. Ducts D, D ... are duct partition walls 25, 25 ..., duct outer walls 26a, 26b, duct side walls 27a and 27b, a connection port connected to an air suction machine (not shown), and a duct side wall installed as necessary. It is comprised from the connected air suction apparatus bottom face. There are slit-shaped duct openings S, S... At the tip of the duct D. A convex portion 25T is formed at the web-side tip of the duct partition wall on the upstream side surface 25a (hereinafter simply referred to as the upstream side surface) with respect to the web traveling direction. As can be seen from the drawing, the cross-section of the convex portion 25T disappears smoothly so that the cross section becomes the same as the surface of the duct partition wall 25 as the distance from the web increases, that is, returns to the original flat wall surface. It is formed. Moreover, entrained air can be more efficiently removed by forming such convex portions, which is more preferable. The reason will be described below. In addition, the side wall 27 of the duct on the back side in the drawing is omitted for easy understanding of the drawing. The same applies to the subsequent FIG.

  The operation of accompanying air suction of the air suction device will be described with reference to FIG. FIG. 4 is a cross-sectional view in which a part of FIG. 3 is further enlarged, and is a partial cross-sectional view in the vicinity of the duct front end portion and the web of the air suction device. As shown in the figure, in the vicinity of the slit-shaped opening S of the air suction device, the spatial pressure in the region H between the duct partition wall 25 and the web 41 is relative to the spatial pressure in the region L between the duct opening S and the web 41. It is in a high state. As the entrained air layer moves in the web traveling direction as the web 41 proceeds, the pressure drop occurs in the duct opening S, so the air flow tends to expand vertically downward in the figure with respect to the web traveling direction. It is quickly sucked into the duct D through the duct opening S. At this time, when the convex portion 25T is formed at the tip of the upstream side surface 25a of the duct partition wall, the entrained air flow that flows into the duct from the duct opening S is sucked into the original velocity component of the entrained air flow. Since the velocity component is added, entrained air can be more efficiently removed. When such entrained air is removed independently in each duct, the duct length, that is, the length of the duct partition wall is preferably 10 mm or more, more preferably 50 mm or more.

  In addition, since the convex portion 25T is formed so as to disappear smoothly so that the cross section thereof becomes the same as the surface of the duct partition wall 25 as the distance from the web increases, the cross sectional shape of the duct D is as follows: The width H1 of the duct opening S indicated by the symbol W1 in FIG. 4 in the web traveling direction is expanded to the opening width of the duct middle portion indicated by the symbol H2 in FIG. It is preferable to satisfy 0.0 <H2 / H1 ≦ 10.0. In order to make the suction air flow smoother, it is more preferable that 1.2 <H2 / H1 ≦ 5.0. Incidentally, if H2 / H1 exceeds 10, the difference between the width of the duct opening and the inside is too large, so that turbulent flow is generated inside the duct and the entrained air removal efficiency may be inferior.

  A specific example of the convex portion as described above will be described with reference to FIG. FIG. 5A shows an example of the convex portion, and is a cross-sectional view of an example of the end portion of the duct partition wall. The cross section of the convex portion 25T1 has a triangular shape, and the angle of the tip is θ. FIG. 5B is a similar cross-sectional view. In the sectional view of the convex portion 25T2, the lower smooth surface in the drawing is an arc in this example, but various curves such as a parabola and a hyperbola may be used. The tip of the convex portion has an acute angle. FIG. 5C is a similar cross-sectional view. In this example, the tip of the convex portion 25T3 is flat, and a curved surface shape as shown in FIG. 5A is combined with the tip. Thus, various combinations are possible as appropriate for the shape of the tip and the surface where the convex portion disappears smoothly. The angle θ of the tip of the convex portion is preferably 10 to 70 degrees, and more preferably 20 to 60 degrees. 5B and 5C, it is preferable that the radius of curvature r and the thickness t of the duct partition wall satisfy 0.25t ≦ r ≦ 5t. In the example in which the flat tip portion and the smooth curved surface shape are combined as shown in FIG. 5C, the length k of the flat portion is preferably in the range of less than 5 mm.

  Regarding the duct partition wall, the corner of the web side tip of the downstream side surface 25b (hereinafter simply referred to as the downstream side surface) with respect to the web direction of the duct partition wall is formed by a chamfered corner, or a smooth curved surface. Preferably, it is formed by. This example will be described with reference to FIG. FIG. 6 is a cross-sectional view of an example of a duct bulkhead tip. In this figure, the corner K of the web side front end portion of the downstream side surface 25b of the duct partition wall is constituted by a smooth curved surface 25K1. In this way, the corner has a smooth surface. Since the companion air flow originally has a very large component in the direction of travel of the web, when removing the entrained air by air suction, the flow velocity in the direction perpendicular to the direction of travel of the web passes after passing between the tip of the duct partition wall 25 and the web. Making it easy to change is preferable in order to efficiently remove entrained air. For this reason, as shown in FIG. 6C, the corner K of the web side tip portion of the downstream side surface 25b of the duct partition wall is not right-angled as shown in FIG. 6B. By chamfering the corner, it is preferable to have a shape having an angle θ2 of more than 0 degrees and less than 90 degrees, or a smooth curved surface shape as shown in FIG.

  In addition, in the case of the angle θ2 illustrated in FIG. 6C, it means that the angle is less than 90 degrees, which means that chamfering is performed, and in order to further improve the entrained air removal efficiency, θ2 is 70 degrees. The following is more preferable, and 45 degrees or less is still more preferable. If the angle is too small, the entrained air removal efficiency may not be changed as compared with FIG. 6B, and the lower limit of the angle is preferably 10 degrees or more.

  Further, the smooth curved surface shape as the corner of the web side tip portion of the downstream side surface 25b of the duct partition wall is preferably a shape in which the cross section of the curved surface can approximate a part of the circumference of a single circle. Various curves such as a hyperbola may be used. When the cross section of the curved surface is a shape that can be approximated to a part of the circumference of a single circle, as shown in FIG. 6A, the radius of curvature of the smooth curved surface is R, and the thickness T of the duct partition wall is When 0.25T ≦ R ≦ 2T, the entrained air removal efficiency is good, which is a preferable mode.

  As described above, the preferred shape of the corner of the tip of the upstream side surface on the duct partition web side and the corner of the tip of the downstream side surface has been described. Of course, it is possible to use only the shape of the corner at the tip of the side surface, or to combine the preferred shape of the tip of the upstream side surface and the preferred shape of the tip of the downstream side surface as appropriate. Although it is referred to as a duct partition wall, for example, even on the most upstream or downstream side of the air suction device, the upper wall of the inner wall of the duct has a shape as described above even if it is a wall that is the outer wall of the duct. It is preferable to make it a corner.

In order to efficiently remove air entrained by the web, the surface of the air suction device facing the web (reference numeral 25c in FIG. 3 corresponds to a part of this surface) is a curved surface. More preferred. Precisely, the shape of the surface of the duct side wall or the front end of the outer wall on the web side determines this surface. The radius of curvature R1 of the web facing surface of the air suction device preferably satisfies the following formula (1) with respect to the radius R2 of the backing roll.
1.0 ≦ R1 / R2 ≦ 1.035 Formula (1)
When the value of R1 / R2 is less than 1.0, R1 <R2, and therefore, the upstream and downstream ends of the surface facing the web of the air suction device are closer to the web than the other parts. Thus, there is a possibility that the entrained air removal efficiency at the center portion is inferior, and both ends may come into contact with the web. On the other hand, when the value of R1 / R2 exceeds 1.035, both ends of the surface facing the web of the air suction device are arranged farther apart from the web than other portions, and the entrained air removal efficiency is inferior. there is a possibility. Actually, the backing roll is used while the radius is reduced by the polishing operation. However, when the air suction device is installed in a state satisfying Equation (1), the accompanying air removal efficiency is practically sufficient. . In order to make the accompanying air removal efficiency better, the upper limit value of the value of R1 / R2 is preferably 1.020. Although it does not specifically limit about a backing roll diameter, Usually, it is 700-2000 mm in diameter.

  However, even in the state of having the entrained air removing means according to the present invention, the viscosity of the coating liquid may be inevitably reduced in order to cope with an increase in coating speed. In this case, even if the entrained air can be removed completely, the viscosity of the coating liquid is low and the amount of coating liquid discharged increases, so that backflow may easily occur. Even if the operating conditions fluctuate, there is a possibility that a backflow may occur even temporarily, so in the present invention, even if a backflow should occur, the following measures should be taken in order not to affect the operability. I found it effective.

  That is, it is preferable that at least the surface that may be contacted with the coating liquid of the air suction device used for the purpose of preventing entrained air is a water-repellent surface. This is not caused by the entrained air on the web when the coating liquid jet collides with the web, but when the coating liquid jet liquid is disturbed for some reason, Even if it becomes severe and close to a phenomenon called backflow, it effectively prevents the coating liquid from accumulating on the surface of the air suction device, and the amount of coating by the scale in which the coating liquid is accumulated and dried This is because the occurrence of profile defects and the occurrence of coating defects such as streaks can be suppressed and the frequency of cleaning can be reduced. It is preferable to use a resin selected from a fluororesin, a polyethylene resin, a polystyrene resin, and a polyacetal resin for the water repellent finish of the air suction device. By the way, the surfaces that the coating liquid of the air suction device may come in contact with are the side surface of the air suction device on the side where the coating liquid jet collides, the web facing surface, and the inner surface of the duct, particularly the inner surface of the tip. is there. To be precise, these are the corresponding portions of the duct bulkhead and the front end of the outer wall. Although it is most preferable to perform water-repellent treatment on all surfaces that may be contacted by the coating liquid of these air suction devices, it is of course possible to use only a part of the surface that is water-repellent if necessary.

  In order to prevent the coating liquid from accumulating on the air suction device, the water contact angle of the water-repellent surface is preferably 110 degrees or more. The higher the water contact angle, the better the coating liquid accumulation preventing property even when the coating liquid comes into contact with each surface of the air suction device. Therefore, the water contact angle is more preferably 135 degrees or more to prevent the coating liquid accumulation. In order to make the property particularly excellent, the water contact angle is particularly preferably 160 ° or more. The upper limit of the water contact angle is not particularly limited, but since it is practically difficult to reach 180 degrees, the upper limit value of the water contact angle is less than 180 degrees. In addition, since it is excellent in durability when the surface of the water-repellent processed surface is a water-repellent metal film by plating, it is a more preferable form.

  The distance x between the duct partition walls of the air suction device having a plurality of duct openings shown in FIG. 3 is 5 mm or more and 100 mm or less because the efficiency of removing the entrained air is increased and manufacturing is easy. preferable. If it is less than 5 mm, the vertical expansion effect with respect to the web traveling direction of the air flow described above becomes low and the manufacturing is difficult, and the duct opening may be blocked by dust caused by the web or the surrounding environment, which is not preferable. . On the other hand, when it exceeds 100 mm, the space between the duct partition web side and the web becomes high, which may hinder the web progress. The distance x between the duct partition walls is more preferably 5 mm or more and 30 mm or less. In addition, when there are three or more duct openings, the distances x between the duct openings need not all be the same, but in order to stably remove the entrained air, the distance x between the duct openings is Preferably all are the same.

  The thickness of the duct partition wall is preferably 1 mm or more and less than 100 mm, and more preferably 3 mm or more and 25 mm or less in order to maintain the distance x between the duct partition walls. Further, the length of the convex portion (reference numeral 25T in FIG. 3) formed on the upstream side of the duct partition wall is the web traveling direction of the duct opening S in FIG. It is preferable that 1.0 <H2 / H1 ≦ 10.0 to be adjusted with respect to the opening width of the duct middle portion indicated by reference numeral H2 in FIG. In order to increase the entrained air removal efficiency, it is more preferable to adjust so that 1.2 <H2 / H1 ≦ 5.0.

FIG. 8 is a plan view of the air suction device shown in FIG. 3 as viewed from the web side. Duct side walls 27a and 27b that serve as side seal plates may be used for connecting the duct partition wall 25, but within a range that does not reduce entrained air removal efficiency due to air suction, by means such as bolts, welding, and adhesion, They can be linked by a single method or a plurality of methods.
The slit-shaped duct opening of the air suction device is the most preferable shape having a uniform interval in the coating width direction, but if it has a uniform air suction capability in the coating width direction, The interval is not necessarily constant. The width of the duct opening in the web width direction is preferably substantially the same as or greater than the web width.

  In FIG. 3, an air suction machine (not shown) is connected to the air suction device 21 via the air suction pipe 23. In addition, it is preferable to connect a gas-liquid separator before an air suction machine at the following points. When backflow occurs for some reason, the coating liquid may be sucked into the air suction device. If the surface of the air suction device is water repellent, It does not stay on the surface and is easily sucked to the air suction machine side. For this reason, when a gas-liquid separator is connected, it can prevent that a coating liquid is attracted | sucked to air suction machines, such as a suction pump. The form of the gas-liquid separator is not particularly limited. For example, a liquid trap type or cyclone type gas-liquid separator can be used.

  The air suction device is connected to an air suction device that generates a reduced pressure state such as a vacuum pump, a vacuum chamber, or an exhaust blower, but as a connection method to the air suction device, a metal that can withstand a desired degree of suction, It can be connected using piping made of rubber or resin, and connected to the side of the air suction device, the center in the coating width direction, or any place so that the suction in the coating width direction is uniform it can. The number of suction machines and pipes to which the suction machines are connected is not limited to one, and a plurality of pipes may be used as necessary.

  Regarding the air suction of the air suction machine connected to the air suction device, it is necessary to be able to remove the entrained air uniformly in the coating width direction, but if the suction is too high, operability is achieved by the action of separating the web from the backing roll. On the other hand, if the suction degree is too low, the entrained air removal efficiency will be inferior. For this reason, the suction degree is preferably −500 to −10000 Pa, more preferably −1000 to −7000 Pa. This degree of suction is defined at the air suction pipe connection part of the air suction machine. Moreover, since the flow rate of entrained air and the flow rate per unit time increase as the coating speed increases, it is preferable to increase the degree of suction as the coating speed increases. The suction degree of each duct opening may be the same, or may be changed as necessary by lowering the upstream side and raising the downstream side. In order to make these changes and for adjustment, it is more preferable to provide a valve, a baffle or the like at the end of each duct.

  There is no particular limitation on the material of the air suction device, and metal or resin materials can be used. However, considering the robustness of the device, metal is preferable.

  The first inflow air inhibiting means for inhibiting the accompanying air origin air flow on the side of the accompanying air removing means, which is the origin of the redevelopment of the accompanying air downstream of the accompanying air removing means, is provided at least on the downstream side surface of the accompanying air removing means. It is more preferable to arrange one. In the present invention, the entrained air on the web is removed by the air suction device which is the entrained air removing device, but the entrained air is entrained on the web surface during a short distance from the entrained air removing device to the coating liquid jet collision point. There remains a possibility that the air layer will recur. In order to inhibit this re-development and maintain good coating suitability, it is necessary to inhibit the accompanying air-derived air flow on the side of the accompanying air removing means, which is the origin of the re-development of the accompanying air downstream of the accompanying air removing means. By disposing at least one first inflow air inhibiting means on the downstream side surface of the entrained air removing means, the air flow on the downstream side surface of the entrained air removing means is intentionally disturbed, thereby improving the air flow development. It can be effectively suppressed.

  Further, the second inflow air inhibiting means for inhibiting the entrained air origin air flow on the coating liquid jet supply liquid portion side, which is the origin of the redevelopment of the entrained air downstream of the entrained air removing means, comprises a slit nozzle. It is more preferable to arrange at least one on the upstream side of the side surface of the coating liquid jet supply section. When considering the flow of air in the vicinity of the coating liquid jet, the upstream side surface of the slit nozzle that forms the coating liquid jet is directed toward the collision point on the web of the coating liquid jet in the discharge direction of the coating liquid jet. It can be considered that a surface air flow similar to the entrained air on the web is generated. Although this air flow is weaker than the entrained air on the web, there is still a possibility of causing a transfer surface defect. Therefore, the second inflow air inhibiting means for inhibiting the entrained air origin air flow on the coating liquid jet supply liquid portion side that is the origin of the redevelopment of the entrained air downstream of the entrained air removing means, By disposing at least one upstream of the side surface of the coating liquid jet supply having, the flow of the smooth air flow on the side surface of the coating liquid jet supply having the slit-like nozzle is inhibited, and the coating liquid jet is discharged. Therefore, it is possible to reduce the collision energy of the air flow caused by the above, and it is possible to more effectively suppress transfer surface defects.

  The inflow air inhibiting means will be further described based on FIGS. FIG. 10 is a cross-sectional view of the vicinity of the accompanying air removal unit before the inflowing air inhibition unit is arranged, and FIG. 11 is a cross-sectional view of the vicinity of the accompanying air removal unit when the inflowing air inhibition units 101 and 103 are arranged. . Since other configurations are the same as those in FIG. 1, some members are indicated by omitting the reference numerals. The inflow air inhibition means 101 corresponds to the first inflow air inhibition means described above, and is disposed on the side surface on the downstream side of the accompanying air removal air suction device 105, and the inflow air inhibition means 103 is the second inflow air inhibition means described above. It corresponds to the means, and is disposed on the upstream side surface of the coating liquid jet supply unit 107. In the case of the example shown in FIG. 10 in which the inflow air inhibiting means is not arranged, a smooth air flow W1 can be generated on the downstream surface of the entrained air removing air suction device 105. There is a possibility that this air flow W1 becomes an accompanying air origin air flow on the side of the accompanying air removing means, which is the origin of the redevelopment of the accompanying air. On the other hand, when the inflow air inhibiting means 101 is arranged, the air flow on the downstream surface of the accompanying air removing air suction device 105 is shown on the downstream surface of the accompanying air removing air suction device as indicated by reference numeral W3 in FIG. Smooth flow is inhibited, and the re-development of entrained air can be effectively suppressed.

  Further, even when no inflow air inhibiting means is arranged upstream of the coating liquid jet supply unit 107, as shown in FIG. 10, an air flow W2 on the upstream side surface of the coating liquid jet supply unit can be generated. This air flow W2 may flow toward the collision point C of the coating liquid jet on the web, and may be an accompanying air-derived air flow that causes the re-development of the accompanying air layer, and causes a transfer surface defect. There is a possibility to become. On the other hand, when the inflow air inhibiting means 103 is arranged, the air flow on the side surface on the upstream side of the coating liquid jet supply section changes as indicated by reference numeral W4 in FIG. Can be reduced.

  The inflow air inhibiting means can be installed in the web traveling direction A either on the downstream side surface of the entrained air removing air suction device, on the upstream side surface of the coating liquid jet supply unit, or on a plurality of these locations. The number of installation locations is not limited to one, and can be a plurality of locations. Further, the number of installed inflow air inhibiting means is not limited to one, but may be plural. Further, it is of course possible to arrange a plurality of inflow air inhibiting means for one installation place so that, for example, a plurality of inflow air inhibiting means are arranged on the side surface of the entrained air removing air suction device 105.

  Various examples of the inflow air inhibiting means referred to in the present invention are shown in FIG. FIG. 9 is a cross-sectional view of various examples of the inflow air inhibiting means used in the present invention. Reference numeral 91 denotes either the upstream side surface of the coating liquid supply unit having a slit-like nozzle, which is a member for installing the inflow air inhibiting means, or the downstream side surface of the accompanying air removal air suction device. A member selected from a flat plate as indicated by reference numeral 92a, a curved plate as indicated by reference numeral 92b, a polygonal pillar as indicated by reference numeral 92c, a cylinder as indicated by reference numeral 92d, and the like is disposed. . “Polygon middle” refers to a polygon or part of a polygon cut out on a straight line, and “cylinder” refers to a cylinder, an elliptical column, or a part of these cut out linearly. For example, a semi-cylinder is also contained. By arranging these inflow air inhibiting means, in the example shown in FIG. 10, an action of inhibiting or disturbing the air flow from the lower part to the upper part is caused, and therefore the development of the air flow in the traveling direction of the coating liquid jet, It is possible to inhibit the re-development of the accompanying air layer, and to avoid deterioration in operability and quality such as defective transfer surface. About the thickness of a flat plate and a curved plate, when it is too thin, since it deform | transforms easily, a vibration may be excited by an air flow and it is unpreferable. Practically, the thickness is preferably 0.5 mm or more, and more preferably 1 mm. From the viewpoint of safety, the free tip of the flat plate / curved plate is preferably a curved surface. When the overhanging height h of the inflowing air inhibiting means member is too small, the installation effect of the member is lowered. Therefore, the height h is preferably 3 mm or more, more preferably 5 mm or more, and further preferably 10 mm or more. When h is too large, installation may be difficult, and is preferably 100 mm or less, and more preferably 50 mm or less. There are no limitations on the material of the flat plate, curved plate, polygonal column, cylinder, etc. used in the inflow air blocking means, but it is required to be robust, so metals, resins, rubbers, etc. are preferably used it can. Moreover, it is also a preferable form to maintain the good operability by using the surface of these inflow air inhibiting means members after being water-repellent.

  As for the installation position of the inflow air inhibition means, the web on the upstream side surface of the coating liquid supply unit having the slit-like nozzle, which is a member for installing the inflow air inhibition means, on the downstream side surface of the entrained air removal air suction device However, if the distance to the web is increased, the effect may be reduced. On the other hand, if the distance is too small, the operability may be reduced by contact with the web. For this reason, the distance between the inflowing air inhibiting means and the web is preferably 5 mm or more as a lower limit, more preferably 10 mm or more, preferably 800 mm or less, more preferably 300 mm or less, and particularly preferably 50 mm or less.

  The coating apparatus according to the present invention is suitable for producing a coated sheet, particularly a pigment-coated paper, in which a coating layer mainly composed of a pigment and / or an adhesive is provided on at least one surface of a sheet-like substrate. Can be used. In the case of the jet coating type blade coating method, generally, the coating speed of the pigment coated paper is already generally operated at a high speed exceeding 1000 m / min. It is expected to be. During such high-speed coating, there is a problem that coating defects are likely to occur due to entrained air and operability deteriorates easily. The coating apparatus of the present invention can effectively prevent the occurrence of coating defects, deterioration in quality, and deterioration in operability even in such high-speed coating.

  In the present invention, with respect to the slit width of the slit-like nozzle for supplying the jet supply type coating liquid, if the slit width is too narrow, coarse particles or aggregates in the coating liquid may be retained between the slits, resulting in a coating amount. The profile may be deteriorated. On the other hand, if it is too wide, the collision speed of the coating liquid jet to the web may be too low to perform normal coating. For this reason, the slit width of the nozzle is preferably 0.5 to 3.0 mm, and more preferably 1.0 to 2.5 mm in order to further stabilize the coating liquid jet.

  In the present invention, with respect to the coating liquid discharge speed from the slit nozzle of the jet supply system, if the discharge speed is slow, transfer of the coating liquid to the running web surface is difficult to perform normally, so that the transfer surface is defective. Is likely to occur, and if it is too early, backflow is likely to occur. For this reason, the lower limit of the coating liquid discharge speed from the slit-like nozzle is preferably 100 m / min or more, and the upper limit is preferably the web traveling speed or less. From the viewpoint of more effectively preventing both transfer surface defects and backflow, the coating liquid discharge rate from the slit nozzle is more preferably 200 m / min or more as the lower limit and 400 m / min or less as the upper limit. .

  In the present invention, the supply amount of the coating liquid from the slit nozzle of the jet supply method can be appropriately changed with respect to the desired coating amount. The coating amount is preferably about 5 to 30 times, and more preferably 10 to 25 times from the balance between the stability of the coating liquid jet and the meterability of the metering blade.

In the present invention, it is formed between the backing roll tangential T _g and Fluid jet 13 in the coating liquid collision point on the web in FIG. 2, the angle of impingement coating liquid jet, the sign of FIG. 2 When the collision angle is too small, a transfer surface defect is likely to occur, and when it is too large, backflow is likely to occur. The upper limit of the collision angle is preferably 70 degrees or less, and the lower limit is preferably 15 degrees or more. From the viewpoint of more effectively preventing both transfer surface defects and backflow, the upper limit of the collision angle is more preferably 60 degrees. Hereinafter, the lower limit is 35 degrees or more.

Regarding the coating solution viscosity, when the viscosity is too high, it becomes difficult to control the coating amount to a desired value with the measuring blade, and when it is too low, backflow tends to occur. Therefore, the viscosity of the coating liquid, or 5 mPa · s is preferable as the lower limit of the high shear viscosity at shear rate ^{1.8 × 10 5 (1 / s} ) measured at Hercules type high shear viscometer, back In order to prevent flow, the lower limit is more preferably 10 mPa · s or more. In order to maintain good coatability, the upper limit value of the high shear viscosity is preferably 45 mPa · s or less, and in order to further improve coatability, the upper limit value is 35 mPa · s or less. More preferred. When the high shear viscosity is 30 mPa · s or less, transfer surface defects can be suppressed by the effect of the present invention, so that the occurrence of backflow can be suppressed, and the effect of the present invention is remarkable. It is.

  The solid content concentration of the coating liquid is not particularly limited. However, if the solid content concentration is not within an appropriate range, it is difficult to control the coating amount to a desired value with a measuring blade. If the solid content concentration is too high, it is not only impossible to control the coating amount with the measuring blade, but the coating amount profile may be extremely deteriorated. On the other hand, when the solid content concentration is too low, not only the desired coating amount cannot be obtained regardless of the condition of the measuring blade, but the quality of the obtained coated product is lowered, which is not preferable. For this reason, the upper limit of the solid content concentration of the coating liquid is preferably 72% or less, more preferably 70% or less, and particularly preferably 68% or less. The lower limit of the solid content concentration of the coating liquid is preferably 30% or more, more preferably 45% or more, and particularly preferably 55% or more. In addition, when the coating liquid solid content concentration is low, the viscosity of the coating liquid tends to be low, and thus backflow is likely to occur. Therefore, the effect of the present invention tends to appear when the coating liquid solid content concentration is 30% or more and 68% or less, and the effect according to the present invention is remarkable when the solid content concentration is 45% to 64%.

  Regarding the web coating speed, the effect of the present invention is great when coating at higher speeds. For this reason, when the coating speed is low, the effect of the present invention is hardly obtained. The effect is hardly exhibited at a coating speed of less than 500 m / min. In view of the effect, it is more preferably 1000 m / min or more, and particularly preferably 1200 m / min or more. The upper limit of the coating speed is not a problem as long as the coating is normally performed on the measuring blade, but operation exceeding 3000 m / min is difficult, and the upper limit of the coating speed is 3000 m / min. The following are preferred ranges.

  As the measuring blade used in the coating liquid measuring unit in the present invention, either a type called a rigid bevel blade or a type called a bendable bent blade can be used. The material of the blade is not particularly limited, and a publicly known measuring blade can be used. Metal blades, ceramic blades, plating blades, thermal spray blades, soft tip blades and the like can also be used. The thickness of the blade blade and the angle of the blade edge are not particularly limited. For example, a blade having a blade edge thickness of 0.05 to 1.0 mm and a blade edge angle of 10 to 90 degrees can be used.

  The web on which the coating layer is formed is not particularly limited, and for example, paper mainly composed of cellulose fibers, films mainly composed of various resins, and the like can be used. In the case of paper, it can be used regardless of the presence or absence of a size press treatment such as starch on the surface and the presence or absence of a coating layer mainly composed of a pigment and / or an adhesive. In the case of a film, it can be used irrespective of the presence or absence of surface treatment by application of an anchor layer or corona treatment.

  There is no particular limitation on the base paper provided with a coating layer mainly composed of a pigment and / or an adhesive, which is used in the production of coated paper using paper mainly composed of cellulose fibers as a web. It is possible to use a base paper for coating and a base paper for coating in which at least one or more undercoat coating layers mainly composed of a pigment and / or an adhesive are provided in advance. In order to improve the gloss and smoothness of the resulting coated paper, use a base paper for coating that is provided with at least one undercoat layer mainly composed of a pigment and / or an adhesive in advance. It is preferable to do. The effect of the present invention is remarkable when using a highly smooth web such as a coated base paper having a high degree of smoothness, such as at least one undercoat layer that is susceptible to backflow. Therefore, a Parker Print Surf (PPS) surface smoothness tester (for example, model: MODEL M-569, manufactured by MESSMER BUCHEL / UK) is used as a base paper for coated paper, and a backing disk: soft Rubber, clamping pressure: It is preferable to use a base paper having a PPS smoothness of 5.0 μm or less measured under a condition of 1 MPa, and it is more preferable to use a base paper having a smoothness of 4.0 μm or less. The use of a base paper having a thickness of 3.5 μm or less is particularly preferred, and the use of a base paper having a smoothness of 3.0 μm or less is the most preferred form of the present invention because the quality of the resulting coated paper is the best.

  When the method of the present invention is applied to the production of the coating sheet, the contact time of the coating liquid to the web, and the contact amount can be made uniform in both the width direction and the flow direction of the web. Even in the case where an extremely mild transfer surface defect in which a transfer surface defect cannot be visually confirmed has occurred, the coating amount profile of the obtained coating and the print quality can be improved.

  The pulp forming the paper substrate is not particularly limited in terms of the production method and type, etc. Chemical pulp such as KP, SP, mechanical pulp such as SGP, RGP, BCTMP, CTMP, ECF pulp, TCF pulp, etc. Waste paper pulp such as chlorine-free pulp, deinked pulp, non-wood pulp such as kenaf, bagasse, bamboo, straw, hemp, etc., organic synthetic fibers such as polyamide fiber, polyester fiber, polynosic fiber, and glass fiber Inorganic fibers such as ceramic fibers and carbon fibers can also be used.

  Moreover, a filler can be mix | blended with a paper base material as needed. The filler in this case is not particularly limited, but various pigments generally used for fine paper, such as kaolin, calcined kaolin, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, talc, zinc oxide, alumina, Mineral pigments such as magnesium carbonate, magnesium oxide, silica, white carbon, bentonite, zeolite, sericite, smectite, polystyrene resin, urea resin, melamine resin, acrylic resin, vinylidene chloride resin and their dense materials Examples thereof include organic pigments that are actual, fine hollow, and through-hole type particles.

  In addition to pulp fibers and fillers, various anionic, nonionic, cationic or amphoteric yield improvers, freeness improvers, paper strength enhancers, fixings are used in the stock. Various papermaking internal additives such as an additive and an internal sizing agent can be appropriately selected and used as necessary. Furthermore, internal additives for papermaking such as dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents and the like can be appropriately added depending on the use of the paper.

  The paper making method of the paper base is not particularly limited, and includes, for example, an acidic paper making method in which the paper making pH is around 4.5, and a neutral sizing agent and / or an alkaline filler such as calcium carbonate as a main component. It can be applied to all papermaking methods such as weak acidity at pH of about 6 to weak alkaline neutral papermaking at about pH9, and the paper machine is also a long net paper machine, twin wire paper machine, round net paper machine, Commonly used paper machines such as inclined wire paper machines can be used as appropriate.

  As the pigment in the coating layer used in the coating sheet of the present invention, commonly used pigments can be used, for example, heavy calcium carbonate, light calcium carbonate, kaolin, calcined kaolin, structural kaolin, deramikaolin, Mineral pigments such as talc, calcium sulfate, barium sulfate, titanium dioxide, satin white, zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, magnesium aluminosilicate, calcium silicate, white carbon, bentonite, zeolite, sericite, smectite Or solid resin such as polystyrene resin, styrene-acrylic copolymer resin, urea resin, melamine resin, acrylic resin, vinylidene chloride resin, benzoguanamine resin, hollow resin, or through-hole resin Organic pigments can also be used, One or two or more kinds among these are appropriately selected and used.

  As the adhesive, a water-soluble and / or water-dispersible polymer compound can be used. For example, cationic starch, amphoteric starch, oxidized starch, enzyme-modified starch, thermochemically-modified starch, esterified starch, and etherified starch. Starches such as carboxymethylcellulose, hydroxyethylcellulose, etc., natural or semi-synthetic polymer compounds such as gelatin, casein, soybean protein, natural rubber, polydienes such as polyvinyl alcohol, isoprene, neoprene, polybutadiene, polybutene, poly Polyalkenes such as isobutylene, polypropylene, and polyethylene, vinyl halides, vinyl acetate, styrene, methacrylic acid, methacrylic acid esters, methacrylamide, methyl vinyl ether, and other vinyl polymers and copolymers, styrene-butadiene systems, Synthetic polymer latexes such as synthetic rubber latex such as tilmethacrylate-butadiene, polyurethane resin, polyester resin, polyamide resin, olefin-maleic anhydride resin, melamine resin, etc. One or more kinds can be appropriately selected and used according to the above.

  In the coating liquid used in the present invention, in addition to the pigments and adhesives described above, various auxiliary agents such as surfactants, pH adjusters, viscosity adjusters, water retention agents, softeners, gloss imparting agents, waxes, Dispersant, flow modifier, antistatic agent, stabilizer, antistatic agent, cross-linking agent, sizing agent, fluorescent brightener, colorant, ultraviolet absorber, antifoaming agent, water resistant agent, plasticizer, preservative Perfume and the like can be appropriately used as necessary so as not to lose the desired effect of the present invention.

Although the coating amount after drying of the coating layer of this invention is not specifically limited, Generally 1-40 g / m < ² > with respect to the single side | surface of a paper base material, Preferably it is 2-30 g / m < ² >, Furthermore, Preferably it is 5-25 g / m < ² >. When the coating amount is less than 1 g / m ² , the effect of forming the coating layer on the base paper is difficult to appear. On the other hand, when it exceeds 40 g / m ² , rapid drying is required during high-speed coating, resulting in binder migration. This increases the possibility of occurrence of printing troubles such as motoring and a decrease in printing strength, so that the coating amount within the range specified above is preferable.

  The drying method for the coating layer is not particularly limited, and commonly used drying methods such as an air dryer, a cylinder dryer, and an IR dryer can be used.

  As the moisture of the coated paper, when using a paper substrate, after providing a coating layer on the paper substrate and after a normal drying step, or after being smoothed in a surface treatment step or the like, if necessary, It is finished by adjusting the water content to 3 to 10%, preferably about 4 to 8%.

  The smoothing process is performed on-machine or off-machine using a normal smoothing device such as a super calender, gloss calender, or soft calender. The number, heating, etc. are also adjusted as appropriate according to a normal smoothing apparatus.

[Example]
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these ranges. In the examples, “parts” and “%” indicate “parts by mass (solid component)” and “% by mass” unless otherwise specified.

Example 1
A coated paper was prepared as follows using the coating apparatus having the configuration shown in FIG. As the air suction device constituting the accompanying air removal means, the air suction device has five slit-shaped duct openings having an angle θ = 45 degrees shown in FIG. It was used. The distance x between the duct partition walls of this apparatus was 30 mm, the slit-shaped duct opening width H1 was 5 mm, and the duct middle opening width H2 was 20 mm. The radius of curvature of the web facing surface of the air suction device was the same as that of the backing roll. The length of the duct, that is, the length of the duct partition wall was 100 mm. The air suction device was installed so that the distance between the air suction device and the web was 5 mm, starting from the upstream side of the point where the coating liquid jet collided with the web. The coating liquids A and B for pigment coated paper shown below are adjusted and sucked so that the suction degree of the air suction machine is −1500 Pa, and the coating liquid A is applied to the coated base paper in a dry coating amount of 11 g / m. After coating and drying so as to be ² , the coating liquid B was continuously applied so that the dry coating amount was 10 g / m ² . At this time, the coating speed is 1300 m / min, the web collision angle of the coating liquid jet is 48 degrees, the coating liquid discharge amount is 395 L / min · m, the coating liquid supply section slit width is 1.5 mm, and the web from the slit tip The coating solution was supplied under the condition of 50 mm. The discharge speed of the coating liquid jet at this time was 255 m / min. At the time of coating, there was no transfer surface defect and no backflow, and the operation state was good, and coating defects were not detected. In addition, the PPS smoothness after apply | coating the coating liquid A was 3.1 micrometers.

<Base paper for coating>
To a pulp slurry of 70 parts of LBKP (freeness (CSF) = 400 ml) and 30 parts of NBKP (freeness (CSF) = 410 ml), light calcium carbonate (PC: manufactured by Shiroishi calcium) was added so that the ash content was 8 parts, Paper was made with a long paper machine using a stock to which 1.4 parts of starch per 100 parts of pulp, 0.15 part of alkenyl succinic anhydride, and 0.5 part of sulfuric acid band were added. Apply and dry with a size press so that the coating weight is 2 g / m ^{2 in} dry weight, and use a machine calendar with a fully automatic digital type Oken air permeability and smoothness tester EYO made by Asahi Seiko Co., Ltd. The Oken type smoothness measured was smoothed so as to be 35 seconds to obtain a paper substrate having a basis weight of 90 g / m ² . The PPS smoothness of this paper base was 5.8 μm.

<Adjustment of coating liquid A>
100 parts of FMT-97 (component: heavy calcium carbonate, manufactured by Phimatech Co., Ltd.), 6 parts of starch (trade name; Ace B, manufactured by Oji Cornstarch Co., Ltd.), latex (trade name: DL921, Dow Chemical) 9 parts) (manufactured by Nippon Co., Ltd.) was added, and water was further added to prepare a coating solution having a solid concentration of 64%. The high shear viscosity at a shear rate of 1.8 × 10 ⁵ (1 / s) of the coating liquid A was 15 mPa · s.

<Adjustment of coating liquid B>
Water and a dispersing agent (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.1 part are added to 80 parts of Miragloss 91 (component: kaolin, manufactured by Engelhard), and dispersed with a Coreless disperser. A kaolin dispersion with a content of 72% was obtained. 20 parts of FMT-97 (component; heavy calcium carbonate, manufactured by Pimatec Co., Ltd.) with a solid content of 75% was added to this dispersion as a solid content to prepare a pigment slurry. To 100 parts of this pigment slurry solid content, 1.5 parts of starch (trade name; Ace B, manufactured by Oji Cornstarch Co., Ltd.) and 12 parts of latex (trade name; T2535D, manufactured by JSR Corporation) are added, and water is added. In addition, a coating solution having a solid concentration of 63% was prepared. The high shear viscosity of the coating liquid B at a shear rate of 1.8 × 10 ⁵ (1 / s) was 19 mPa · s.

Comparative example 1
Coating was performed under the same conditions as in Example 1 except that the air suction device used in Example 1 was not installed. As a result, a coating defect due to a transfer surface defect occurs, and the quality of the obtained coated paper is inferior in the coating amount profile in the width direction and the flow direction, and neither the blank paper quality nor the printing quality has reached the practical level. It was.

Comparative example 2
Since a transfer surface defect occurred in Comparative Example 1, the supply amount of the coating liquid jet was changed from 395 L / min · m to 450 L / min · m, and the collision angle of the coating liquid jet to the web was 48 ° to 54 °. Changed to As a result, the transfer surface defect was resolved, but a backflow occurred, so the operation could not be continued, and it was impossible to obtain coated paper continuously.

Comparative example 3
Instead of the air suction device used in the example, coating was performed in the same manner as in the example except that the suction box shown in FIG. 7 was installed close to the surface of the base paper. The suction box is the same as that proposed in Japanese Patent Application Laid-Open No. 10-43661, and the air suction port surface of the air suction box 51 is installed so as to be substantially perpendicular to the moving direction of the web. A cover plate 53 having a thickness of 2 mm and a slot having a width of 3 mm was attached to the air suction port. As a result of coating, a coating defect due to defective transfer surface occurs when coating the coating liquid B, and the quality of the obtained coated paper is inferior in the coating amount profile in the width direction and the flow direction, Neither the blank paper quality nor the printing quality reached the practical level.

Sectional drawing of an example of the coating apparatus which concerns on this invention. 4 is a schematic enlarged cross-sectional view showing only the relationship between the coating liquid jet supply unit 11 and the backing roll 31. FIG. The cross-sectional enlarged view seen from the side of an example of air suction apparatus arrangement | positioning. Sectional drawing for demonstrating the condition of the space pressure of the duct partition front-end | tip part vicinity of an air suction device. Sectional drawing which shows the various modifications of the upstream side surface tip shape of the duct partition tip part of an air suction device. Sectional drawing which shows the various modifications of the downstream tip shape of the duct partition tip part of an air suction device. The perspective view of the suction box used in the comparative example 3. FIG. The figure which looked at the cross section of the air suction apparatus perpendicularly to the backing roll direction. Sectional drawing of the various examples of the inflow air inhibition means used by this invention. Sectional drawing of the entrained air removal part vicinity before arrange | positioning an inflow air inhibition means. Sectional drawing of the entrained air removal part vicinity at the time of arrange | positioning the inflow air inhibition means 101 and 103. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Coating liquid jet supply part 11a Coating liquid jet supply part Coating liquid discharge slit front-end | tip 13 Coating liquid jet 13a Coating liquid film transferred on web 13b Coating liquid film measured on web 15 Measuring blade 17 Weighing blade holder 21 Entrained air removal device (air suction device)
21a Start point of entrained air removal device 23 Air suction pipe 31 Backing roll 33 Web A Traveling direction of web / backing roll C Colliding point of coating liquid jet to web T Coating liquid jet collision point tangential direction Φ Coating liquid jet collision angle d Distance from coating liquid discharge slit nozzle tip to web coating liquid collision point 41 Web H1 Duct opening width in web traveling direction H2 Duct width in web traveling direction 51 Suction box 52 Suction tube 53 Cover 72 Duct partition upstream side surface 73 Duct partition upstream side surface convex boundary line 74 Duct partition upstream side surface 91 Coating liquid discharge slit nozzle upstream side surface, entrained air removal device downstream side surface 101 First inflow air inhibiting means 103 Second inflow air inhibiting means

Claims (8)

A coating device for coating a coating liquid on the surface of a web that is continuously supported by a backing roll,
A coating liquid jet supply unit that has a slit-like nozzle opening, blows out the coating liquid from the nozzle opening, and forms a coating liquid jet, from the nozzle opening to the running web A coating liquid supply unit arranged so that the distance to the coating liquid collision point is in the range of 5 to 700 mm;
A slit-like duct that is arranged 3 to 100 mm upstream of the web from the point where the coating liquid collides with the web and is substantially parallel to the width direction of the web for sucking air in a substantially vertical direction with respect to the web traveling direction. Entrained air removal means comprising an air suction device comprising a plurality of ducts having openings;
A measuring unit that is disposed on the downstream side of the web with respect to the coating liquid collision point to the web and scrapes the coated coating liquid,
A coating apparatus having: The coating apparatus according to claim 1, wherein a radius of curvature R1 of a web facing surface of the air suction device satisfies the following expression (1) with respect to a backing roll radius R2.
1.0 ≦ R1 / R2 ≦ 1.035 Formula (1)   The coating apparatus according to claim 1 or 2, wherein a surface with which the coating liquid of the air suction device may come into contact is a water-repellent surface.   A convex portion is formed on the upstream side as a cross section of the duct partition wall at the upstream end of the duct partition upstream side surface constituting the slit-shaped duct opening of the air suction device, and the convex portion is separated from the web. 4. The coating apparatus according to claim 1, wherein the coating apparatus is a convex portion formed so as to disappear smoothly so as to be the same as the surface of the duct partition wall.   The corner of the web side tip on the downstream side surface of the duct partition that forms the slit-shaped duct opening of the air suction device is formed by a chamfered corner or a smooth curved surface. The coating apparatus according to any one of claims 1 to 4.   The first inflow air inhibiting means for inhibiting the accompanying air origin air flow on the side of the accompanying air removing means, which is the origin of the redevelopment of the accompanying air downstream of the accompanying air removing means, is provided at least on the downstream side surface of the accompanying air removing means. The coating apparatus of any one of Claim 1 to 5 arrange | positioned one.   The second inflow air inhibiting means for inhibiting the entrained air origin air flow on the side of the coating liquid jet supply section which is the origin of the redevelopment of the entrained air downstream of the entrained air removing means is a coating having a slit-like nozzle The coating apparatus according to claim 1, wherein at least one coating apparatus is disposed upstream of the side surface of the liquid jet supply unit. A coating produced by applying a coating layer mainly composed of a pigment and / or an adhesive on at least one surface of a sheet-like substrate with the coating apparatus according to any one of claims 1 to 7. Sheet.

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