JPH10277459A - Curtain coating equipment - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To solve the problem of gas entering between a web and a coating solution in a curtain coating apparatus in which a shield for blocking entrained air generated by the movement of the web from the curtain is brought into contact with the web. To provide a curtain coating apparatus for producing a product of stable quality without causing paper dust, fluffing of a continuously running paper, fluffing of coated paper, scratching of a film or the like, abrasion problem, etc. . The contact member to be brought into contact with the web of the shield is a rotating roll, or abrasion-resistant ceramics such as oxide, carbide, nitride, boride, silicide, and sulfide ceramics. A curtain coating device made of a material having excellent wear properties and having a surface composed of a smooth arc. Further, the present invention is a curtain coating device that provides a negative pressure region by a suction device on the upstream side of the web from the contact portion, the curtain coating device having two or more contact portions, and providing a negative pressure region between the contact portions by a suction device. Coating device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the production of printing paper, pressure-sensitive recording paper, heat-sensitive recording paper, photographic paper, printing plate making material, etc. It becomes a problem when applying the coating material at high speed.
To resolve gas intrusion between web coating liquids and to produce products of stable quality without causing paper dust, fluffing of coated paper, flaking of coated paper, scratches on films, etc. A curtain coating device.

[0002]

2. Description of the Related Art A curtain coating method is a method in which a free-falling curtain is formed with one or more coating liquids, and this is caused to collide with a material to be coated to form a coating film on the material to be coated. A surface coating method has been used for a long time. In the curtain coating method, when a coating film is formed on a web, an uncoated portion may occur, or application unevenness may occur.

One of the causes is that the affinity between the web surface and the coating solution is poor. In this case, physical means,
This problem can be solved by increasing the affinity between the web and the coating solution using chemical means. Another cause is the problem of entrained air on the web surface. The entrained air enters the space between the web and the coating liquid to cause an uncoated portion, or causes problems such as shaking the curtain and causing uneven coating, and becomes more remarkable as the coating speed increases.
This is one of the main reasons that the coating speed cannot be increased by the curtain coating method.

In a slide hopper type curtain coating apparatus, which is a typical coating apparatus for coating a photographic light-sensitive material, the pressure is reduced at a coating point (a point where the web and the coating liquid come into contact with each other) so that the heel portion of the coating line is located on the upstream side of the web. To stabilize the application. That alone is not enough.
As described in JP-A-32923, solvent vapor is generated simultaneously with generation of reduced pressure.
As disclosed in Japanese Patent Publication No. 64, a means is disclosed in which the entrained air is replaced with a gas (carbon dioxide gas) which is easily dissolved in the coating liquid.

On the other hand, in the extrusion type curtain coating device, since the falling momentum of the curtain destroys the layer of entrained air, coating can be performed in a higher speed range than in the slide hopper type curtain coating device. However,
As the coating speed increases, and in order to eliminate the occurrence of defects in product quality, various measures have been taken to remove the entrained air itself.

[0006] Basically, as described in JP-B-49-24133, a wind shield plate for shielding entrained air is provided upstream of the curtain. After that, various measures were taken, but a typical method was to suck the entrained air upstream of the curtain (JP-A-62-2892).
No. 64). However, the method of sucking the entrained air could not sufficiently shield the entrained air generated in a higher-speed region.

As a means for sufficiently confirming the effectiveness of shielding the entrained air, there is a method (hereinafter referred to as a contact type) in which the web and the shield are brought into contact with each other several tens of millimeters upstream of the curtain. The contact method is the ultimate method of shielding the entrained air because it physically shields the entrained air with a solid shield, and it is difficult to shield the entrained air more efficiently with the other methods than the contact method. .

[0008] However, in the contact type, since the shielding material comes into contact with the web, paper dust and fuzzing are generated on the web such as paper, and on coated paper and the like, the coating composition peels off, resulting in powder drop. On the web such as film,
It can also cause scratches on the web surface. In addition, when the shield is simply brought into contact, a problem occurs due to wear of the shield as the coating speed increases, which is not suitable for a long-time operation at an actual production level.

That is, in a curtain coating apparatus for applying a coating liquid to a continuously running web, a method of shielding entrained air generated by running of the web from the curtain has a large effect of a contact type, but on the other hand, paper powder, fluff, and It has been difficult to produce a stable product without the problems of dropping, web surface scratches, and abrasion.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a curtain coating apparatus for applying a coating solution to a continuously running web, wherein the curtain is located upstream of a point where the curtain collides with the web.
A shield is provided to block the entrained air generated by the movement of the web from the curtain. In a curtain coating apparatus in which the shield is in contact with the web, there is a problem when coating at a high speed. Solves the ingress of gas, and continuously runs paper dust, fluff, coated paper dust,
An object of the present invention is to provide a curtain coating apparatus for producing a product of stable quality without causing a problem such as damage to a film or abrasion.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a curtain coating apparatus for applying a coating liquid to a continuously running web. The curtain coating apparatus is provided with entrained air generated by the movement of the web upstream of a point where the curtain collides with the web. In a curtain coating apparatus in which a shield for shielding from a curtain is provided and the shield is in contact with a web, a contact member of a portion of the shield which is in contact with the web is a rotating roll, or an oxide-based ceramic or carbide. High-speed coating by a curtain coating device made of a highly wear-resistant material such as ceramic, nitride-based ceramic, boride-based ceramic, silicide-based ceramic, and sulfide-based ceramic, and having a smooth arc-shaped surface. To solve the problems of gas intrusion between the web and the coating liquid, and to reduce paper dust, fluff, flaking of coated paper, Wound to the arm or the like, without generating the wear of the problem, such as it is possible to manufacture a product of stable quality.

Furthermore, a curtain coating device provided with a negative pressure region by a suction device on the upstream side of the web from the contact portion, and a curtain provided with two or more contact portions and provided with a negative pressure region between the contact portions by a suction device. The above problem can be solved by a coating device.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. Needless to say.

FIG. 1 is a schematic view of a curtain coating apparatus showing one embodiment of the present invention. 2, 4, 5, and 6 are side views of the vicinity of the curtain showing one embodiment of the present invention, and FIGS. 3 and 7 are enlarged views of a part of FIGS.

First, the outline of the curtain coating apparatus of the present invention will be described with reference to FIG. The coating liquid adjusted in advance is sent from the coating liquid storage tank 11 to the coater head 1 by the liquid supply pump 12. The inside of the coater head 1 is composed of a manifold 6 and a slit 2, each of which is finished with high precision. The supplied coating liquid is filled in the manifold 6, and the narrow gap that passes when the liquid is supplied to the slit 2 reduces the influence of the dynamic pressure due to the liquid supply of the pump 12, and the pressure distribution in the width direction is made uniform. , Flowing out of the lip 3 to form a vertical curtain 4.

The curtain 4 having a uniform profile in the width direction comes into contact with the continuously running web 5 and forms a coating film on the web 5. Here, the edge guide 10a,
10b is provided not exceeding the width of the coater head 1 and further exceeding the width of the web 5, and the curtain is formed exceeding the width of the web 5. The reason that the curtain 4 is formed to exceed the width of the web 5 is to prevent a thick coating of the coating layer at both ends of the curtain 4. The coating liquid flowing down beyond the width of the web 5 is collected in the liquid receiving tank 14, returned to the coating liquid storage tank 11, and then applied again. Web 5
When the application is interrupted, for example, when is cut, the application liquid is collected in the liquid receiving tank 14.

The curtain head used in the present invention includes a slide hopper type, an extrusion type, and a slide extrusion type in which both are mixed.

In order to apply the formed curtain 4 in a stable state, a certain height from the web 5 to the outflow portion below the coater head 1 is required. In the present embodiment, the height is required. The height suitable for stabilizing the curtain 4 is 60 to 300 mm, preferably 100 to 250 mm, and more preferably 120 to 1 mm.
80 mm.

In the present invention, the shield 7 is provided on the upstream side of the point where the curtain 4 collides with the web 5 and the curtain head 1.
And a contact member having a contact portion 8 that contacts the web 5 is provided at the tip of the shield 7. In the present invention, as described above, the shielding of the entrained air is performed by the most efficient contact method, the curtain is stabilized, and since the coating device is used to solve the remaining problem, the shielding material contacts the web. It must be a contact type.

The position of the contact portion 8 is such that the curtain 4 is
It is necessary that the distance from the point of collision with the vehicle be 200 mm or less on the upstream side. If the distance is more than 200 mm, the curtain will be disturbed by the effect of the entrained airflow generated downstream of the contact portion 8, and a coating failure will occur. However, 200m
Even if the distance is within 10 m, the coating damage does not occur due to the influence of the coating speed or the like, but the curtain may be disturbed.
When the position of is close to the point where the curtain 4 collides with the web 5 within an allowable range in the structure of the apparatus, it is easy to obtain a good coating result.

Although the material of the shield 7 is not particularly limited, the contact member is made of the rotating roll 15 shown in FIGS. 2 and 3 or a material having excellent wear resistance, and is made of a smooth material as shown in FIG. It is necessary that the contact member 16 has an arc-shaped surface.
The contact member 16 having a surface formed of a smooth arc refers to, for example, a circular shape, an elliptical shape, and a shape such as an R-shaped corner.
The circle and the ellipse may have some arcs. (FIG. 4 is a diagram showing an example of a contact member 16 having a surface having a smooth arc, in the case of a surface having a part of a circular arc.)

The material having excellent abrasion resistance is mainly a ceramic material, for example, a sintered ceramic material, and a molded product of solid particles of a ceramic component is fixed by heating, and the sintered ceramic material is sintered. In other words, it may be a sintered ceramic material by either liquid phase sintering or solid phase sintering,
In order to increase the mechanical strength of the sintered ceramic itself,
A sintered ceramic material by a hot press method in which pressure is applied while heating may be used. Further, the contact portion 8 is formed using a spray-type ceramic material in which a molten ceramic material is coated on the tip of the shield 7 by spraying or the like. It does not interfere with the effects of the invention.

Examples of the components of the ceramic material include, but are not limited to, the following specific ceramic components having excellent wear resistance. Further, a multi-component ceramic containing these and mixing two or more kinds may be used.

(1) oxide-based ceramics: beryllia, zirconia, yttria, titania, quartz, silica, tria, alumina, sapphire, lanthania, etc. (2) carbide-based ceramics: silicon carbide, titanium carbide, tantalum carbide, tungsten carbide , Boron carbide, diamond, niobium carbide, zirconium carbide, etc .; (3) nitride-based ceramics: silicon nitride, boron nitride, titanium nitride, aluminum nitride, cermet, etc .; (4) boride-based ceramics: lanthanum boride, borate (5) silicide ceramics, (6) sulfide ceramics: molybdenum disulfide and the like.

As described above, it is necessary that the contact member be a rotating roll 15 or a contact member 16 made of a material having excellent wear resistance and having a surface formed of a smooth arc. , 15 m / min low-speed coating to 1500 m / min or more high-speed coating,
Particularly at high speeds, the friction between the contact portion 8 and the web 5 causes
The contact member is worn, the uniform shape of the contact member in the original width direction of the web collapses, the uniform enclosing air is not shielded in the width direction of the web, or the contact member is roughened by abrasion. This is because it would hurt 5. When the contact member is the rotating roll 15, the web 5
Since the roll 15 rotates as the vehicle travels, there is no wear, and the above-described problem does not occur.

By the way, when a spray-type ceramic is used, there is no need to adhere to the shield 7. However, in the case of a sintered ceramic or the like, a contact member is formed once and then adhered to the shield 7. There is a need. As this method, for example, it is preferable to bond using an adhesive made of an epoxy-based thermosetting resin. This is because the web 5 and the contact portion 8 generate heat due to friction, and if the contact portion material is removed by the heat, the effect of the present invention cannot be sufficiently exhibited. When the rotating roll 15 is used as the contact member, a bearing 23 is attached to the end of the rotating roll 15 as shown in FIG.
And the rotation axis of the rotating roll 15 must not be moved by the running of the web 5. This is because if the rotating shaft moves up and down due to the running of the web 5 and the rotating roll 15 bounces on the web, it becomes impossible to completely shield the entrained air. In order to allow smooth rotation.

Examples of the epoxy-based thermosetting resin include bisphenol A type, bisphenol B type, bisphenol AD type, bisphenol S type, 2,6-xylenol type, phenol novolak type, O-cresol novolak type, and Functional form, tetraphenylolethane form,
Polyethylene glycol form, polypropylene glycol form, neopentyl glycol form, 1,6-hexanediol form, trimethylolpropane form, propylene oxide bisphenol A form, hydrogenated bisphenol form, and the like can be mentioned, but not particularly limited. Instead, another epoxy-based thermosetting resin may be used.

If necessary, a curing agent or a combination of other resins, elastomers, primers and the like may be used to improve the adhesiveness. Specific examples include triethyleneamine (TETA), tetraethylenepentamine (TEPA), diethylenetriamine (DE
TA), diethylaminopropylamine (DEAPA)
Such as aliphatic amines, metaphenylenediamine (MPD
A), aromatic amines such as diaminodiphenylmethane (DDM) and methylene dianiline (MDA), polyamides such as versamide, phthalic anhydride (PA), pyromellitic dianhydride (PMDA), chlorendic anhydride ( HE
And acid anhydrides such as T).

In the present invention, the various webs 5 are effective in shielding the entrained air and preventing the webs 5 from being damaged, but it is preferable that the contact members are variously changed depending on the type of the webs 5. Good coating results can be obtained. That is, for a web 5 such as paper and pigment coated paper, which is more likely to cause problems such as abrasion, paper dust, and powder dropping than a plastic film or the like, abrasion resistance is better than using a rotating roll 15 as a contact member. It is better to use a material of a certain nature. Conversely, in the case of a web 5 that is easily damaged such as a plastic film, it is preferable to use the rotating roll 15. However, these are determined in consideration of the required quality of the product to be manufactured, and there is a case where it is not necessary to use the rotating roll 15 even if it is a plastic film. In any case, the contact member is rotated 15
Alternatively, the contact member 16 having a smooth arc-shaped surface made of an abrasion-resistant material can be used to shield the entrained air and obtain a curtain coating apparatus that manufactures a stable product without damaging the web 5. It is possible.

In the present invention, a more stable product can be manufactured by providing the negative pressure region 18 by the suction device 17 on the upstream side of the web 5 from the contact portion 8 as shown in FIG. Further, two or more contact portions 8 are provided as shown in FIGS.
By forming the negative pressure region 18 between the contact portions 8 by the suction device 17, a very stable product can be manufactured.

When a negative pressure area 18 is provided on the upstream side of the web 5 from the contact portion 8, first, the contact member
Closer contact with For example, in the case of the web 5 made of paper having a rough surface, if the adhesion is poor, it is difficult to completely block the entrained air in some portions of the web 5 in the width direction. Normally, a roll-shaped web take-up roll is prepared and set in a coating device. However, a part of the web in the width direction of the web becomes wavy (partly slackened) due to the influence of hardness or the like in the width direction of the web take-up. Actually, a portion where the contact member does not contact the web 5 is generated. In such a state, it is also difficult to completely block the entrained air. Therefore, by providing the negative pressure region 18 on the upstream side of the web 5 from the contact portion 8, the contact member and the web 5 are attracted, and the adhesion is improved.

Second, the contact member comes into contact with the web 5,
When the coating operation is performed for a long time, dust and paper dust gradually accumulate in the contact portion 8 on the upstream side of the web 5 and finally get caught between the contact member and the web 5 and it is difficult to completely block the entrained air. Or the accumulated dust and paper dust enter between the web 5 and the coating solution, making it difficult to manufacture a stable product. Therefore, by providing the negative pressure region 18 by the suction device 17 on the upstream side of the web 5 from the contact portion 8, dust,
By absorbing the paper powder, a stable product can be manufactured without causing the above-described problems. still,
If two or more contact portions 8 are provided and the space between the contact portions 8 is made to be the negative pressure region 18 by the suction device 17, the effect of suction is improved, and the effect of sucking the above-mentioned dust and paper dust is further improved. .

Although the shape of the shield 7 of the present invention is not particularly limited, in order to exhibit the effect of the present invention, FIGS.
Various shields such as (7 in FIG. 2, 7 in FIG. 4, and 2 in FIG. 5)
0, 21) in FIG. 7 is preferably used. When the negative pressure region 18 is provided by using the suction device 17, FIG.
It is preferable in terms of operation that the pressure gauge 19 be attached to the shield as shown in FIG.

Next, the coating liquid used in the present invention, web 5
Will be described. In addition, the application speed and the application liquid supply amount at the time of application will be described.

In the present invention, the coating solution includes a photographic emulsion solution in which silver halide is dispersed in an aqueous gelatin solution, a magnetic material coating solution in which magnetic particles are dispersed in water or an organic solvent, A color former and a developer are dispersed as a color former coating solution, a microcapsule containing a color former or a developer is dispersed as a pressure-sensitive color developer coating solution, and an inorganic or organic pigment coating paper coating solution is dispersed. Regardless of the solid content, such as those in which pigments are dispersed, any coating liquid capable of performing curtain coating can be used without any limitation. Coating solutions in the range of 300 cps are preferred.

As the web 5 used in the present invention, generally used high-quality paper, medium-quality paper, paper renewal, machine-coated paper, art paper, cast-coated paper, synthetic paper, resin-coated paper, plastic film, metal Board, rubber board,
Includes fabrics woven from natural or synthetic fibers.

[0037]

EXAMPLES Examples will be given below to further clarify the present invention. In the examples, all parts are parts by weight, unless otherwise specified, the concentration is the weight percentage of solid content, and the coating amount is the coating amount after drying.

Example 1 <Capsule Dispersion> 200 parts of a high boiling oil (KMC-113 manufactured by Kureha Chemical Co., Ltd.) in which 5 parts of crystal violet lactone (CVL) were dissolved, was dissolved in a 5% styrene-maleic anhydride copolymer aqueous solution. (PH5.0) added to 250 parts,
The emulsion was emulsified so that the average particle diameter became 6 μm.

Next, a 40% melamine-formalin precondensate aqueous solution (Sumitetsu Chemical Co., Ltd. Sumiretz Resin) 20%
Was added to the above emulsifier, the temperature was adjusted to 75 ° C., and the mixture was reacted for 2 hours.
And cooled to room temperature to obtain a 40% microcapsule dispersion.

<Coating Liquid> The microcapsule dispersion thus obtained was further adjusted to a solid content of 33% by adding water to the following composition to obtain a coating liquid. 40% microcapsule dispersion 100 parts Wheat starch (average particle diameter 20 μm) 50 parts 48% carboxy-modified styrene butadiene copolymer latex 20 parts

2 and 3, the contact member shown in FIGS. 2 and 3 is turned into a rotating roll having a diameter of 20 mm, and the distance between the position where the web and the curtain collide with the contact portion (the value A in FIG. 2) is set to 50.
mm, and the web was coated on a high-quality paper having a basis weight of 40 g / m ² by using an extrusion-type curtain coating apparatus.
The pressure-sensitive recording paper having a total coating length of 100,000 m was coated at a coating speed of 0 m / min so that the coating amount was 3.5 g / m ² . As shown in FIG. 3, the rotating roll was installed by attaching a bearing to the end of the rotating roll, attaching the bearing to the base, and placing the rotating roll in contact with the web. The shield was installed so as to cover the rotating roll.

Example 2 As shown in FIG. 4, a contact member was made of a semicircular zirconia ceramic having a cross section of 8 mm in diameter in place of a rotating roll, and was attached to the tip of a shield made of high carbon steel. Coating was performed in the same manner as in No. 1.

Example 3 As shown in FIG. 5, from the contact portion to the upstream side of the web, suction was performed at a negative pressure of −50 mmAq using a suction device, and coating was performed in the same manner as in Example 2. The shielding object used had the shape shown in FIG.

Example 4 As shown in FIGS. 6 and 7, two contact portions were provided, and the space between the contact portions was suctioned with a negative pressure of -150 mmAq using a suction device, and coating was performed in the same manner as in Example 2. . The shield used was one having the shape shown in FIGS.

Comparative Example 1 Coating was performed in the same manner as in Example 2 except that the contact member of Example 2 was changed to high carbon steel instead of zirconia ceramic.

Comparative Example 2 As shown in FIG. 8, zirconia ceramic was used as a material at the tip of the shield 7 as a contact member.
Coating was performed in the same manner as in Example 2, except that a contact plate 9 having a trapezoidal shape of 0 ° and a thickness of 8 mm was used.

[Evaluation of Paper Powder] With respect to the coated paper after coating 100,000 m, the coated paper of 1,000 m between 99000 m and 100,000 m was irradiated with black light (fluorescent light), and the paper dust was visually inspected. Was counted.

[Evaluation of Curtain Stability] Similar to the evaluation of paper powder, the coating length and the stability of the curtain at the time of 99000 m to 100000 m were visually evaluated according to the following criteria. Note that the allowable level is ○ or more. A: Very stable level without curtain shaking. ○: Curtain sways slightly, but no problem in operation. Δ: A level at which curtain shaking occurs and slight application unevenness (non-application occurs).

[0049]

[Table 1]

Example 5 An application was performed in the same manner as in Example 1 except that the web of Example 1 was changed to a plastic film having a thickness of 0.05 mm.
9900 for the coated web after 100000 m coating
A 1000 m coated web between 0 m and 100,000 m was visually inspected for flaws, but no flaws were found.

[0051]

The evaluation results as shown in Table 1 above were obtained, but it is clear that Examples 1-4 of the present invention have much smaller number of paper dusts than Comparative Examples 1-2. , And Comparative Example 1 at the same time
Then, it is clear that the contact portion is worn out due to the long-time application and the entrained air of the web cannot be completely shielded, and the curtain stability is worse than in Examples 1 to 4. Also, from the results of Example 5, the plastic film was not damaged, and the effectiveness of the present invention is clear. That is, by using the curtain coating apparatus of the present invention, it is possible to stabilize the curtain for a long time, and to produce a product of stable quality without causing a problem of damage to paper dust, film, etc. of continuously running paper. It can be said that the fuzz of paper running continuously,
It is easily presumed that stable quality can be manufactured without any problem of powder falling of the coated paper.

[Brief description of the drawings]

FIG. 1 is a schematic view of a coating apparatus showing one embodiment of the present invention.

FIG. 2 is a side view of the vicinity of a curtain of the coating apparatus according to the embodiment of the present invention.

FIG. 3 is an enlarged view of a portion X in FIG. 2;

FIG. 4 is a side view of the vicinity of a curtain of a coating apparatus according to another embodiment of the present invention.

FIG. 5 is a side view showing the vicinity of a curtain of a coating apparatus according to another embodiment of the present invention.

FIG. 6 is a side view of the vicinity of a curtain of a coating apparatus according to another embodiment of the present invention.

FIG. 7 is an enlarged view of a portion Y in FIG. 6;

FIG. 8 is a side view of the vicinity of a curtain of a coating apparatus showing a comparative example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Curtain head 2 Slit 3 Lip 4 Curtain 5 Web 6 Manifold 7 Shielding object 8 Contact part 9 Contact plate 10a, 10b Edge guide 11 Storage tank 12 Liquid supply pump 13 Roll 14 Liquid receiving tank 15 Rotating roll 16 Surface made of a smooth arc 17 Suction device 18 Negative pressure area 19 Pressure gauge 20 Shield 21 Shield 22 Suction port 23 Bearing 24 Base

Claims (3)

[Claims] 1. A curtain coating apparatus for applying a coating liquid to a continuously running web, wherein a curtain air generated by movement of the web is cut off from the curtain upstream of a point where the curtain collides with the web. In a curtain coating apparatus in which the shield is provided in contact with the web, a contact member of a portion of the shield which is in contact with the web is a rotating roll, or an oxide-based ceramic or a carbide ceramic. A curtain coating device comprising a material having excellent abrasion resistance, such as a nitride ceramic, a boride ceramic, a silicide ceramic, a sulfide ceramic or the like, and having a surface formed by a smooth arc. 2. A negative pressure area is provided by a suction device on the upstream side of the web from the contact portion.
The curtain coating apparatus according to the above. 3. A curtain coating apparatus according to claim 1, wherein said at least two contact portions are provided, and a negative pressure region is provided between said contact portions by a suction device.