JP2000107666A - Coating method for paper and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the occurrence frequencies of cut paper at a high-speed blade coater. SOLUTION: Fine water mists are sprayed to either one or both of the mirror finished surface M of the backing roll R of the blade coater or the outer peripheral curvilinear surface N thereof with which the paper does not come into contact. One of the causes for the cut paper is the drying and solidifying of the splashed coating liquid mists on the mirror finished surface M of the backing roll R or the outer peripheral curvilinear surface N thereof with which the paper does not come into contact, forming coating liquid slag. The splashing of this coating liquid slag to the paper surface and the eventual occurrence of the cut paper are admitted. The generation of the coating liquid slag and the occurrence of the cut paper are lessened by spraying the fine water mists as a countermeasure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blade coating method and a coating apparatus which reduce the occurrence of paper breakage in a step of coating a coating liquid on paper with a blade coater, and which are excellent in high-speed operability and production efficiency. It is.

[0002]

2. Description of the Related Art In recent years, offset printing paper is characterized by a steadily growing demand in the commercial printing field for advertisements and advertisements such as flyers, catalogs, pamphlets, and direct mails. Although these commercial prints have low commercial value themselves, it is important that the purpose be achieved as an advertising medium, and therefore, low-cost, high-quality prints have been demanded. In order to improve the printing finish, it is necessary to improve the smoothness of the paper and to reduce the penetration and bleeding of the printing ink.

[0003] Coated paper on which a thin coating film is formed on a paper surface with a pigment, a synthetic resin or the like is manufactured for the above purpose, and is most often used in the field of commercial printing. Also,
On the other hand, the cost reduction of users is becoming stronger, and the paper used is also lower in grade and weight.

[0004] In order to respond to such vigorous demand for lightweight coated paper, paper manufacturers are promoting wider and faster coating equipment in order to achieve more efficient production of products and cost reduction. Under these circumstances, it is an important technical issue to increase productivity while maintaining high quality, and studies are being made on a coating method, speeding up the coating, and reviewing the coating liquid.

[0005] Conventional methods for producing coated paper include an off-machine method in which papermaking and coating are performed in separate steps and an on-machine coating method in which papermaking and coating are continuously performed by a single machine. ,
The on-machine coating method enables more efficient production. In addition, after coating the base paper with an undercoat coating solution containing an inexpensive pigment on-machine, and then applying the top coating solution, the coatability of the base paper is improved by the undercoat coating in terms of quality. Since the shape and the printing quality are improved, the multilayer coating tends to be advanced in the production of lightweight coated paper.

[0006] A blade coater is mainly used for on-machine coating. The blade coater mainly includes a roll application method and a fountain application method. As shown in Fig. 2, the roll applicator system is a coating method in which a back surface of paper coated by an applicator roll is brought into contact with a backing roll, and a blade is pressed against a coating surface to adjust a coating amount. As shown in FIG. 3, the fountain applicator method is a method in which the surface of a paper running in contact with a backing roll is
This is a coating method in which a coating liquid is ejected from a nozzle to apply the coating liquid on the paper surface, and a coating amount is adjusted by pressing a blade against the coating surface.

[0007] However, in the case of on-machine coating, the length of the apparatus from papermaking to overcoating and drying becomes very long. Therefore, once paper breakage (paper cut) occurs, it takes time to re-pass the paper. And production efficiency is greatly reduced. For this reason, it is necessary to establish a manufacturing technique for reducing the frequency of paper breakage as much as possible.

Various factors can be considered for the paper breakage by the coater, in addition to the case where excessive tension is applied to the paper. For example, the coating liquid mist is scattered and adheres to the coating head / coating liquid pan periphery, the outer peripheral curved surface of the backing roll and the mirror surface which is the circular side surface at both ends, peripheral equipment, and the like, and further dried and solidified lees. It scatters and falls on the paper surface, which breaks down as a nucleus, and breaks due to mechanical factors such as raw paper defects and dirt, base paper defects caused by dust and foreign matter contamination, and draw and tension fluctuations due to speed increase. Paper is generated.

[0009] In order to reduce such a large number of paper cutting factors,
At the operation site, great care is taken, and when the machine is stopped, cleaning is performed carefully at various places to respond. In addition, in order to minimize the dispersion of the coating liquid mist in the coater, a vinyl sheet is placed on the backing roll, at the entrance / exit, around the coating liquid pan, or in the case of a fountain applicator type blade coater. Various devices have been devised such as attaching a rubber sheet, a PVC plate, a tape or the like for preventing scattering on both sides of the fountain lip.

[0010] Nevertheless, especially when a lightweight coated paper is manufactured at a high speed by an on-machine blade coater, the frequency of paper breakage increases, and once paper breakage occurs, the production loss is large and There is a problem that the time loss to be spent increases and the production efficiency is greatly reduced.

[0011]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, an object of the present invention is to provide a blade coating method and a coating apparatus which generate less paper breakage and are excellent in production efficiency.

[0012]

Means for Solving the Problems The main cause of paper breakage is that a tension higher than the strength of the paper is applied. However, for a fountain applicator type blade coater which is an example of a coating apparatus shown in FIG. When the cause of the paper was sought, the coating liquid mist scattered and adhered to the coating head, the coating liquid pan periphery, the backing roll, the mirror surface, etc., and the dried coating liquid lees scattered on the paper. It has been found that there are many cases in which the sheet falls and becomes the core of a defect, resulting in paper breakage. In FIG. 1, the coating liquid sprayed from the fountain nozzle is sprayed from the edge of the paper to a portion other than the dry edge portion d of about 5 to 10 mm, and is in contact with the dry edge portion d of the paper and the paper. No backing roll R
It also scatters on the outer peripheral curved portions N at both ends. Further, it also scatters on the mirror surfaces M at both ends of the backing roll R. The coating liquid mist scattered on the dry edge portion d and the portion N which is not in contact with the paper at the outer peripheral curved surface portions at both ends of the backing roll,
Since the coating liquid residue is scraped off by the blade B, the coating liquid residue does not accumulate in a large amount. However, the coating liquid that has scattered on the mirror surface M of the backing roll gradually accumulates and solidifies after drying.
It is easy to become coating liquid cake coating.

Therefore, in the present invention, the fine water mist is continuously sprayed on the mirror surface M of the backing roll R using the spraying device E installed at the position shown in FIG. The frequency of paper generation was greatly reduced. Further, since the residue of the coating liquid may be generated on the portion N which is not always in contact with the paper at the outer peripheral curved portions at both ends of the backing roll R, fine water mist is sprayed on this portion as well, It was found that the effect of reducing the frequency of paper breaks was great.

Hereinafter, features of the present invention will be described in detail. The inventor has
In pursuit of the cause of the paper break, the coating liquid residue generated mainly by drying of the coating liquid mist adhering to the mirror surfaces at both ends of the backing roll, the centrifugal force due to the rotation of the backing roll,
It was recognized that there were relatively many cases in which the paper flow scattered and dropped and adhered to the paper surface due to the air current generated by the running of the paper, and this became a nucleus to cause paper breakage.

[0015] Therefore, in order to continuously wash off the coating liquid mist adhering to the mirror surfaces at both ends of the backing roll and to prevent the formation of coating liquid lees, a method of continuously flowing a water shower to the mirror surfaces at both ends of the backing roll. However, the frequency of paper breaks did not decrease significantly.

[0016] Therefore, as a result of a more thorough re-examination of the causes of paper breakage, it has been found that always keeping the coating liquid mist adhering to the mirror surface in a wet state is effective in preventing the drying lees from scattering and reducing the frequency of paper breakage occurrence. Admitted that it can be. As a result of examining the method of maintaining the wet state, it was confirmed that the air-water mixed mist, which can reduce the particle size of water using high-pressure air instead of the water shower, is more effective.

The reason for this is not clear, but it is thought that the finer water mist has a greater effect of more uniformly penetrating and moistening the applied coating liquid mist or coating liquid lees. Can be In the water shower, water droplets that collided with the mirror surfaces at both ends of the rotating backing roll bounce off,
It is considered that the paper is re-scattered together with the fine residue and dirt, so that the occurrence of paper break cannot be effectively prevented.

[0018] The coating liquid residue scattered from the mirror surface of the backing roll often adheres to the paper surface opposite to the coating surface in most cases. However, the paper surface on the opposite side to the coating surface comes into contact with a roll such as a tension roll immediately after coating, so if the scattered coating liquid cake is in a wet state, even if it adheres to the paper surface, it should be dried. Since it spreads on the paper without being a core, it is considered that it does not cause a paper break.

Further, various experiments were conducted on the particle size of the water mist, and it was found that it is desirable to continuously spray a water mist having a Sauter average particle size of 100 to 400 μm. When a water mist having a Sauter average particle diameter smaller than 100 μm is sprayed, the amount of water sprayed is reduced, and the water mist itself is easily scattered over a wide range. Therefore, it becomes necessary to install a number of spray nozzles close to the backing roll, which deteriorates the operability and, because the spray nozzle and the backing roll are close to each other, mist of the coating liquid scattered from the backing roll is reduced. It was also found that the phenomenon that the injection port of the spray nozzle was blocked was liable to occur.

Conversely, when spraying a water mist having a Sauter average particle size significantly exceeding 400 μm, it is difficult to uniformly wet the coating liquid mist or the coating liquid cake without much difference from the above-mentioned shower ring. It was also found that the effect of reducing the frequency of paper breakage was significantly reduced, and that water mist colliding with the backing roll rebounded and was re-scattered with fine residue and dirt.

Further, the present inventor has found that not only the mirror surfaces at both ends of the backing roll but also the portions of the outer peripheral curved surfaces at both ends which do not come into contact with the paper, the same phenomenon was observed. By spraying the same fine air-water mixture mist on the outer peripheral curved surface as described above, the frequency of paper breakage was further reduced.

Further, the spray effect of the air-water mixed mist of the present invention is as follows.
This is remarkable when using an on-machine blade coater and coating at a high speed of 1000 m / min or more. In the case of an off-machine coater or in the case of coating at a low speed of 1000 m / min or less, in the case of a paper having a normal tensile strength, the frequency of sheet breakage itself is very low. Although it becomes difficult, when the coating treatment is performed on paper having extremely low tensile strength, the effect of the present invention is remarkably exhibited,
Easily imagined.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, it is naturally desirable that the amount of fine water mist sprayed on the mirror surface at both ends of the backing roll and on the outer curved surface portion not in contact with the paper be as small as possible from an economical viewpoint. is there. The amount of the fine water mist to be sprayed greatly varies depending on the components of the coating liquid used for coating. That is, the ratio of the pigment component and the resin contained in the coating liquid and the characteristics thereof cause a difference in the easiness of the generation of the coating liquid lees.

Therefore, the structure of the spraying device used in the present invention does not need to be a special structure, but the Sauter mean particle size of the water mist to be sprayed is at least 100 mμ to 40 μm.
It is necessary that the water mist can be adjusted in a range of 0 μm and the spray amount of water mist can be adjusted in a wide range. In addition, it is desirable that both the air supply pipe and the water supply pipe have a flow rate control valve and / or a pressure reducing valve so that the spray speed can be adjusted, and that the spray pattern can be adjusted.

Furthermore, it is desirable to have a mounting structure in which the spray position, spray direction and spray angle can be freely adjusted.
This is because the spray positions at both ends of the outer peripheral surface of the backing roll change depending on the width of the paper to be coated.

As an example of the spraying device and its mounting position, the distance from the tip of the nozzle to the roll surface is 100 to 60.
At 0 mm, the nozzle spraying on the outer peripheral surface of the roll is movable in the roll width direction from both ends of the roll to 500 mm inside according to the width of the paper. The base pressure of the air pressure of the spraying device is 5.0 kg / cm ² , and the pressure is set to 0.5 to
The water pressure can be adjusted within a range of 5.0 kg / cm ² , and the water pressure is 1.0 to 10.0 kg / cm ^2
It can be adjusted in the range of ² . The mounting position of the nozzle is
At least one point is attached to each of the backing rolls so that they can be sprayed on the outer peripheral curved surfaces at both ends and mirror surfaces at both ends.

[0027] The blade coater used in the present invention is:
The liquid supply system may be any of a roll application, a fountain application, and a short dwell type application. However, in the case of a roll coater type blade coater, since the applicator roll and the backing roll are generally set apart from each other, the coating liquid may scatter to the backing roll as compared with the other two types. Because of the small number, the present invention can be expected to have a great effect when applied mainly to a fountain applicator and a short dwell type applicator type blade coater.

The coating method may be a single-layer coating or a multi-layer coating of two or more coatings. In the case of a multi-layer coating, the undercoating coating method is not particularly limited. A film transfer system such as a blade or rod metering size press coater or various blade coaters as described above may be used.

The paper to be coated may be a commonly used fourdrinier former, a gap type twin wire former, a hybrid former or a circular net former formed with a twin wire in the latter half of the fourdrinier portion, in a single layer or multilayer. Paper made,
Any paper having a basis weight of 30 to 600 g / m ² made by acidic papermaking, neutral papermaking, or alkaline papermaking may be used, and not only chemical pulp but also paper containing mechanical pulp or recovered waste paper pulp may be used. .

[0030] The formed paper is then appropriately pressed and dried, and then subjected to a surface coating using a clear coating liquid containing a water-soluble binder such as starch or a derivative thereof, if necessary, and an auxiliary if necessary. It is treated or a primer coating liquid having a pigment, an adhesive and the like is applied.

[0031] Pigments used in the coating liquid include heavy calcium carbonate, light calcium carbonate, kaolin, clay, delaminated clay, talc, satin white, silica, barium sulfate, calcium sulfate, zinc oxide, titanium dioxide and the like. Inorganic pigments, organic pigments such as plastic pigments, and the like, and these pigments can be used alone or in combination of two or more as necessary.

The adhesive used for the coating liquid is selected from latex or other water-based adhesives, and if necessary, one or more types are selected and used. As latex,
Styrene-butadiene copolymer, conjugated diene-based copolymer latex such as methacrylate-butadiene copolymer,
A vinyl polymer latex such as a polymer or copolymer of an acrylate ester and / or a methacrylate ester, or a product obtained by further modifying these with a functional group-containing monomer such as carboxyl.

Examples of aqueous adhesives other than latex include starches such as oxidized starch, esterified starch such as urea-phosphate esterified starch, etherified starch such as hydroxyethyl etherified starch, dextrin, positive starch and other starches, casein, and the like. Adhesion for ordinary coating such as proteins such as soy protein and synthetic protein, synthetic resin adhesives such as polyvinyl alcohol, polyvinylpyrrolidone, maleic anhydride resin and melamine resin, cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose and hydroxymethylcellulose Agent. Further, various auxiliaries, such as a dispersant, a thickener, a water retention agent, a defoaming agent, and a water-proofing agent, which are blended in a general pigment for coated paper may be used.

[0034]

According to the present invention, the scattered coating liquid mist is dried and solidified on the mirror surface of the backing roll and the outer peripheral curved surface not in contact with the paper to form coating liquid cake. As a result, the paper may be cut. In the present invention, a fine water mist is constantly sprayed on the coating liquid mist adhered to the backing roll to suppress the generation of the coating liquid lees. Can be reduced.

[Brief description of the drawings]

FIG. 1 is a structural explanatory view of an apparatus of the present invention.

FIG. 2 is a structural explanatory view of a roll applicator type blade coater.

FIG. 3 is a structural explanatory view of a fountain applicator type blade coater.

[Explanation of symbols]

 A Applicator roll B Blade C Coated surface d Dry edge E Spray nozzle M Mirror surface N Outer curved surface P Coating liquid R Backing roll S Paper

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masahiro Hirakawa 2-8-1, Iida-cho, Iwakuni-shi, Yamaguchi Japan F-term in Iwakuni Mill (reference) 4D075 AA01 AC21 AC88 AC92 CA48 DA04 DB18 EA06 4F040 AA22 AA31 AB14 AC01 BA23 CB33 DB06 4L055 BE08 CH12 CH30 EA16 FA22

Claims (2)

[Claims] 1. A paper coating method in which a coating solution is adjusted by pressing a blade against a coating surface while a back surface of paper coated with a coating liquid is in contact with a backing roll. One or both of the mirror surface and the outer curved surface not in contact with the paper have a Sauter average particle size of 100
A method for coating paper, which comprises spraying a water mist having an average particle size selected from the range of μm to 400 μm. 2. A paper coating apparatus which adjusts a coating amount by pressing a blade against a coating surface while bringing a back surface of the paper coated with the coating liquid into contact with the backing roll. A Sauter average particle size of 100 μm is applied to one or both of the mirror surface and the outer curved surface that does not contact the paper.
A paper coating device comprising a spray device capable of spraying a water mist of m to 400 μm.