JP2009228173A - Production method of liner for corrugated card board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the yield ratio of chemicals to be used by preventing the chemicals from getting mixed in white water. <P>SOLUTION: A corrugated cardboard liner having a basis weight of 75-290 g/m<SP>2</SP>is produced at a paper making rate of not less than 500 m/min. The method includes the following steps (1)-(6) continuously and successively: (1) a paper making step for forming wet paper formed of at least two layers obtained by combining at least a layer formed by a gap former system and a layer formed by a fourdrinier system including a fourdrinier part, (2) a dehydrating step for dehydrating with a dehydrating facility including a shoe press, (3) a predrying step for predrying the dehydrated wet paper, (4) a coating step for coating chemicals for the surface which contains at least a sizing agent and a dye on the wet paper surface after predried, and coating chemicals for the rear surface which contains at least a paper-strengthening agent on the rear surface, (5) a post drying step for drying the coated paper after coating, and (6) a flattening step for flattening the surface of the coated paper with a flattening facility. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a cardboard liner intended for manufacturing a cardboard liner. In addition, the process which concerns on this invention can be utilized also for manufacture of a core base paper.

  The paperboard is a paper machine in which a plurality of paper layers are stacked, and is used as a packaging material as a corrugated liner and a corrugated core base paper.

  For example, in the case of corrugated cardboard, it is a three-layer structure in which corrugated paper is used to paste corrugated core base paper that has been processed into a corrugated board (corrugating machine) into a corrugated cardboard liner, and then another corrugated cardboard liner is glued onto it. is there.

  Paperboard has traditionally been a product that uses a large amount of wastepaper. However, in recent years, wastepaper pulp has been subjected to repeated recycling, and the pulp fibers are exhausted, the Runkel ratio is increased, and the fiber length is shortened with each recycling process. The cardboard liners using these waste paper pulps tend to have low compressive strength.

  Since paperboard is mainly used for packaging materials, high strength is required for the cardboard liner and the core base paper. However, there is a technique to increase the blending ratio of virgin pulp in order to cope with the decrease in strength due to the increase in the frequency of waste paper recycling, but this is contrary to the recent increase in environmental protection awareness and the trend toward resource saving. There is also an inevitable cost increase.

  Taking strength improvement as an example, as a measure to obtain a corrugated liner having a high compressive strength while using a large amount of waste paper, a method of adding a paper strength enhancer to the raw material pulp for improving the compressive strength has been performed. . As this paper strength enhancer, starch, which is a natural polymer, and polyacrylamide, which is a synthetic polymer, are widely used.

  Conventionally, however, the paper strength enhancer is contained in the raw material pulp (that is, added internally), so the excess amount of the paper strength enhancer that does not settle on the pulp fiber at the paper making stage flows out into the white water, causing equipment contamination and wastewater. The load of the processing equipment (for example, increase in the COD value) and problems that impair the stability of the wet end control occur.

  As mentioned above, the problem in the internal addition of the paper strength enhancer to the raw material pulp has been described as a representative example. However, the above-mentioned problem is not limited to the paper strength enhancer, but various dyes, sizing agents, etc. in the case of producing a liner for cardboard. The same occurs when functional chemicals are added to raw pulp.

  On the other hand, a technique is disclosed in which an aqueous starch suspension added with an inorganic acid and urea is passed through a continuous gelatinizer to apply a starch paste liquid having a reduced viscosity by thermochemical modification to the surface of the core base paper. (Patent Document 1).

  The thing of patent document 1 is the invention of about 20 years ago at this time, and while the quality of the used paper pulp at that time was good, it is as above-mentioned that the quality of the current used paper pulp is falling. is there. Moreover, the thing of patent document 1 is only research at the laboratory level, and continuous production, especially production at high speed is not considered. Furthermore, the invention of Patent Document 1 relates only to the improvement of the strength of the core base paper, and is not assumed for the liner paper.

  In any case, the current general-purpose technology is that various functional chemicals are added to the paper stock, and the deterioration of the quality of waste paper pulp is dealt with by increasing the amount of functional chemicals added. Yes.

  In some manufacturers, for the production of the core base paper, a paper strength enhancer is also applied by a size press. On the other hand, when manufacturing a liner for corrugated cardboard, high size strength is required on the outer surface side to be printed, so it is necessary to use a sizing agent and it is also a printing surface. In this respect, a coloring dye is required. Therefore, when manufacturing the outer layer of the cardboard liner, the sizing agent and the dye are added to the raw pulp and the other layers are made together. As described above, when the sizing agent and the dye are added to the raw material pulp, the sizing agent and the dye are mixed into the white water as in the case of the paper strength enhancer, causing the equipment to be contaminated and increasing the load of the wastewater treatment equipment (for example, COD). Such as an increase in value). In particular, mixing of the dye into the wastewater is a matter that should be avoided due to the coloration of the wastewater.

  As far as the present inventor is aware, there is no technique for coating a sizing agent and a dye with a size press or the like, particularly when making a cardboard liner at a paper making speed of 500 m / min or more.

JP 07-26494 A

  Therefore, the main problem of the present invention is to solve problems such as various functional chemicals mixed into white water, causing equipment contamination and increasing the load on the wastewater treatment equipment (for example, increasing the COD value). Another object is to improve the yield of functional chemicals. Other issues will become apparent from the description below.

  In the process of trying to coat a sizing agent and a dye with a size press when making a corrugated board liner at a paper making speed of 500 m / min or more, the inventor makes the formation good and rapidly dehydrates. It was found that the agent and the dye can be uniformly applied to the outer surface of the wet paper after the preliminary drying, and the present invention has been completed.

The present invention that has solved the above problems is as follows.
[Invention of Claim 1]
A method for producing a corrugated board liner, comprising producing a liner for corrugated board having a basis weight of 75 to 290 g / m ² for paper making at a paper making speed of 500 m / min or more.
The following processes (1) to (6) are incorporated in order.
(1) A wet paper web forming step for forming a wet paper web comprising at least two layers obtained by combining at least a layer made by a gap former method and a paper made by a Ford linear method having a long mesh part,
(2) a dehydration step of dehydrating the wet paper with a dehydration facility including a shoe press;
(3) a pre-drying step of pre-drying the dehydrated wet paper;
(4) A coating process in which an outer surface chemical containing at least a sizing agent and a dye is applied to the outer surface of the wet paper after preliminary drying, and a rear surface chemical including at least a paper strength enhancer is applied to the rear surface;
(5) A post-drying step for drying the coated paper after coating,
(6) A flattening step of flattening the surface of the coated paper with a flattening facility.
(Function and effect)
In the present invention, a cardboard liner is made at a paper making speed of 500 m / min or more in order to increase production efficiency. In addition, according to the present invention, by applying functional chemicals with a size press or the like, the above-mentioned functional chemicals are mixed into white water, causing contamination of the equipment and increasing the load on the wastewater treatment equipment (for example, increasing the COD value). Can solve such problems.
In the case of high speed papermaking at a papermaking speed of 500 m / min or more, the formation is deteriorated and the dewaterability is reduced. Deterioration of the formation is a problem to be solved particularly when producing a corrugated board liner that requires printability. And in order to coat functional chemicals with a size press or the like, it is necessary to complete the rapid dehydration with good formation. Therefore, according to the present invention, when a wet paper comprising at least two layers is formed by combining at least a layer made by a gap former method and a layer made by a Ford linear method having a long mesh portion, While it is a high-speed papermaking of 500 m / min or more, a wet paper excellent in formation can be obtained.
When the wet paper is dehydrated using a dehydration facility including a shoe press, rapid dehydration is possible. When functional chemicals are applied to the wet paper after dehydration and preliminary drying using a size press, etc. Uniform functional chemicals can be applied to the surface part.
When producing a liner for corrugated board, in contrast to the case of adding a sizing agent and a dye to a conventional raw pulp, according to the present invention, at least a layer that is made by a gap former method and a Ford linear method having a long mesh part Apply a sizing agent and a dye to the outer surface of the wet paper (which will eventually become the outer surface of the corrugated cardboard product) by using a size press, etc., on the wet paper consisting of at least two layers. In order to achieve the target strength and reduce the amount of chemicals used for coloring and to improve the yield, it is desirable to make paper at the lowermost layer by a gap former method, It is preferable to form the sizing agent and the dye intensively on the front and back surfaces of the wet paper by forming the upper layer by a Ford linear system having a long web part. Therefore, it is necessary to ensure sufficient formation and dewatering before coating in order to make the sizing agent and dye uniformly and unevenly distributed on the surface of the wet paper using a size press or the like. .

  The present invention includes a flattening step of flattening the surface of the coated paper after drying with a flattening facility. Accordingly, not only the surface of the coated paper is flattened, but also the external chemicals including the sizing agent and the dye are uniformly fixed by the flattening treatment.

  In the structure which can obtain the said effect most simply, it is not giving the said chemical | medical agent for an outer surface and a chemical | medical agent for a back surface until it reaches a coating process.

[Invention of Claim 2]
The method for producing a corrugated board liner according to claim 1, wherein the raw material pulp contains 50% by weight or more of used paper pulp made of corrugated used paper.

(Function and effect)
Even if it contains 50% by weight or more of waste paper pulp made of corrugated paper that has been repeatedly recycled, it ensures the formation and the strength of the outer surface due to the sizing agent. Obtainable.

[Invention of Claim 3]
The manufacturing method of the liner for corrugated boards of Claim 1 or 2 with which a coating process coats with the size press which consists of a film transfer system or a pound system.

(Function and effect)
According to this aspect, good coating can be performed.

[Invention of Claim 4]
In the dewatering process, using a trinip press comprising a first press, a second press and a third press from the upstream side to the downstream side:
The first press is a double felt press in which water is squeezed from wet paper through two felts by a press nip formed by a pair of suction rolls and grooved rolls, and the grooved rolls are covered with rubber. A roll having a rubber hardness (JIS K6253) of 95 ° or more;
The second press is a single felt press that squeezes water from a wet paper through a single felt by a press nip formed by a suction roll and a surface ceramic-coated roll or a surface artificial stone cover roll;
The third press is a single felt press that squeezes water from a wet paper through a single felt by a press nip formed by a surface ceramic-coated roll or a surface artificial stone cover roll and a shoe press;
The manufacturing method of the liner for corrugated boards of Claim 1 or 2.

(Function and effect)
According to this aspect, rapid and appropriate dehydration can be performed.

According to the present invention, various functional chemicals can be mixed into white water, causing equipment contamination, and solving conventional problems such as increased load on the wastewater treatment equipment (for example, increased COD value).
And it can manufacture the liner for corrugated board which shows a required characteristic, although it is high speed papermaking with a papermaking speed of 500 m / min or more.

Next, an embodiment of the present invention will be described.
The liner for corrugated board according to the present invention is one in which the outer surface (which finally becomes the outer surface of the cardboard product) is colored with a dye. In addition, the back surface basically refers to the color tone of raw material pulp. However, a base paper having an outer surface that is basically colored with a dye simply by applying a water repellent or the like during or after the coating process according to the present invention is included in the concept of the cardboard liner of the present invention.

  An example of manufacturing equipment will be outlined in advance, and then each process will be described in detail.

<About manufacturing equipment examples>
The drawing shows an example of manufacturing equipment, and flows from upstream to downstream in the order of the drawing numbers. Moreover, it is a paper machine capable of making not only a corrugated board liner but also a core base paper by the manufacturing equipment. In the following, description will be made centering on the manufacture of a liner for corrugated cardboard, and how to manufacture the core base paper will be described to the extent necessary.
In the embodiment, a two-layered corrugated liner for a first layer and a second layer is manufactured.

  (Wet paper forming step 10) The lower layer (first layer) is provided with a first head box 11 capable of controlling the density in the width direction, and paper is made by a gap former method. The upper layer (second layer) includes the second head box 12 and is made by a paper machine formed by a Ford linear system having a long net portion. The upper and lower layers are combined to form a two-layer wet paper.

  (Dehydration step 20) The wet paper is dehydrated by a trinip press 21 as a dehydration equipment including a first press, a second press and a third press.

  (Preliminary drying step 30) The dehydrated wet paper is preliminarily dried by a predryer 31.

  (Coating process 40) The wet paper after the preliminary drying is coated with the coating liquid on the outer surface and the back surface by the size press 41. Then, an outer surface chemical containing at least a sizing agent and a dye is applied to the outer surface, and a rear surface chemical containing at least a paper strength enhancer is applied to the rear surface to obtain a coated paper.

  (Post-drying step 50) The coated paper after coating is dried by the dryer 51.

  (Flatening step 60) The surface of the coated paper is flattened by a calendar 61 as a flattening facility.

  Moreover, in the most suitable structure which solves the subject in this invention, until the coating process 40 is reached, the said chemical | medical agent for an outer surface and a chemical | medical agent for a back surface are not given to a paper material.

<About chemicals used in the coating process>
In the present invention, an outer surface chemical containing at least a sizing agent and a dye is applied to the wet paper outer surface after preliminary drying, and a rear surface chemical including at least a paper strength enhancer is applied to the rear surface.
As the chemicals for the outer surface and the chemicals for the back surface, various functional chemicals are included in order to provide a function necessary for the target as a cardboard liner. As the external chemicals, at least a sizing agent and a dye are included, and (surface) paper strength enhancer, yield improver, anti-slip agent, ink acceptor and the like can be used as necessary. As the chemicals for the back surface, a paper strength enhancer is included, but a sizing agent or an anti-slip agent can be used if necessary.

  These chemicals are applied to the outer surface of the wet paper after pre-drying by applying a sizing agent and dye to the outer surface of the wet paper with a size press, etc. Compared to the above, the amount of chemicals used for obtaining the target strength and coloring is reduced, and the yield is improved. Of course, in the conventional example, functional chemicals are mixed into the white water, causing the equipment to be contaminated, and problems such as an increase in load on the wastewater treatment equipment (for example, an increase in the COD value) can be solved.

"About dyes"
As a method for dyeing a liner containing a large amount of waste paper pulp, a method for dyeing a liner is proposed in which a dye is added directly at the front stage in the raw pulp preparation process, and a basic dye is added in a seed box immediately before the paper machine ( Japanese Patent Laid-Open No. 2002-88686). The present invention intends to apply a dye as well. By applying the dye, there is no uneven coloring even when the amount of the dye used is small compared to the case where the dye is added to the conventional raw material pulp.

  There is no restriction | limiting in particular in the dye used for this invention, A basic dye, an acid dye, an anionic direct dye, a cationic direct dye, and a nonionic dye can be used. If necessary, organic pigments and inorganic pigments can be used in combination with dyes.

  In the present invention, an anionic direct dye is most suitable as the dye. Dyes include anionic direct dyes and cationic basic dyes. Anionic direct dyes are more excellent in fading. However, when adding at the same time as the sizing agent or paper strength enhancer, anionic starch is often used as the paper strength enhancer, and in the case of a cationic dye, there is a possibility of forming an aggregate. Therefore, it is desirable to use an anionic direct dye.

  Further, as the paper strength enhancer, an anionic paper strength enhancer is desirable, which prevents aggregation with the sizing agent and facilitates handling.

Since the dye may react with other functional chemicals, in order to avoid the reaction, it is preferable to disperse the dye dispersed in advance in the coating liquid immediately before the coating step. Next, dyes are exemplified.
R1: Red anion direct dye, manufactured by Toa Kasei Co., Ltd.
R2K: Red cationic direct dye, “Cartazol Red K2BN Liquid” manufactured by Clariant Japan
Y1: Yellow anion direct dye, “Mikado First Yellow 21R” manufactured by Toa Kasei Co., Ltd.
Y2K: Yellow cationic direct dye, “Cartazole Yellow KGL Liquid” manufactured by Clariant Japan
B1: Blue anion direct dye, Nippon Kayaku Co., Ltd. “Direct Sky Blue 5B200”
B2K: Blue cationic direct dye, “Cartazole Blue KRL Liquid” manufactured by Clariant Japan
B3: Blue basic dye, “Basazol Blue 16L” manufactured by BASF Japan Ltd.

About paper strength enhancers
In the present invention, a paper strength enhancer is applied to at least the back surface. The paper strength enhancer is desirably blended in an amount of 0.2 g / m ² or more in terms of pulp on the surface of the back layer. As the paper strength enhancer, it can be used to improve surface strength, dry strength or wet strength, such as starches, polyvinyl alcohol (PVA), vegetable gum, cellulose derivatives (CMC, etc.), polyacetic acid Vinyl, polyacrylamide (PAM), formaldehyde resin, etc. can be used arbitrarily. The paper strength enhancer can also be applied to the outer surface.

  As for an outer surface and a back surface, it is desirable for the surface strength by the wax method of JIS P8129 (1997) surface strength test to be 8A-20A. In particular, the outer surface is preferable because it satisfies the required printability. If the surface strength is lower than 8A, a whitening problem may occur due to paper peeling during printing. If it is within the range of the above surface strength, it becomes necessary and sufficient surface strength.

  Also in the paper strength enhancer, in order to develop a synergistic effect with other functional chemicals on the waste paper pulp showing anionic property, as described above, it is possible to use an anionic paper strength enhancer. It is preferable for exhibiting

  As the paper strength enhancer, it is preferable to use starches. One kind or two or more kinds of anionic starch, cationic starch, and amphoteric starch can be used. The raw material starch applied to the aqueous starch solution is not particularly limited. For example, raw starch such as wheat, rice, corn, potato, tapioca, and a cation subjected to a predetermined thermochemical treatment using these as raw materials. Various modified starches such as modified starch, phosphate starch and urea phosphate ester starch are listed. In addition, although these starches may be used independently, you may mix and use 2 or more types according to a use and needs.

  The starch dilution concentration of the applied starch aqueous solution is preferably adjusted to 5 to 15%, and preferably 5 to 10%. If the starch dilution concentration of the aqueous starch solution is less than 5%, there is no effect as an adhesive and the desired surface strength cannot be obtained. On the other hand, if the starch dilution concentration of the starch aqueous solution is higher than 15%, it is not preferable because stains are likely to occur and there is a risk of causing unevenness of the paper surface or contamination of starch due to starch agglomeration.

  As a suitable starch in the present invention, the molecular weight is less than 3 million, the concentration of the coating solution (starch paste) is 35%, and the viscosity at a temperature of 40 ° C. is 85 cp or less, preferably 10 to 90 cp, more preferably. Can suitably use 30-85 cp of modified starch. In particular, when high-speed papermaking at 500 m / min or higher, there is a problem of “mist” when the starch viscosity is low, and there is a problem of “paper cut due to viscosity” when the viscosity is high.

  As the starch, for example, various known ones such as oxidized starch, cationized starch, carboxymethylated starch, pregelatinized starch, phosphate esterified starch, ester-modified starch, urea phosphate-modified starch, and unmodified starch are used alone. Or 2 or more types can be mixed and used. Modified starches such as carboxymethyl starch (anionic) and phosphate starch (anionic) exhibit the effect of improving tensile strength and surface strength while penetrating into paper.

The starch used in the present invention is an analytical value based on the amount of starch in paper based on TAPPI T419 om-91, and the content of the starch for the cardboard liner (solid content) in the state where the liner for the cardboard is divided into two substantially equally in the thickness direction. ) is, the surface side (0.30～3.00G the exposed surface) when forming the cardboard sheets / m ² cardboard liner, preferably 0.50～2.50G / m ^2, even more preferably 1 It is applied to the surface of the liner for corrugated board by a coating equipment so as to contain .50 to 2.40 g / m ² . Further, on the back side (the surface hidden when the corrugated cardboard sheet is formed), 0.20 to 3.00 g / m ² , preferably 1.00 to 2.40 g / m, similarly to the front side of the corrugated board liner. ² , and more preferably applied to the surface of the liner for corrugated board by a coating equipment so as to contain 1.00 to 1.80 g / m ² . Thereby, the cardboard liner of improved compression strength can be obtained without impairing the bonding property (bonding suitability), the disaggregation property, and the economic efficiency of the cardboard liner of the present invention. In addition, when the coating content of starch is less than 0.30 g / m ² on the front side and less than 0.20 g / m ² on the back side, it is difficult to maintain compressive strength and to suppress the generation of paper dust. When the coating content on the front side of the coating exceeds 3.00 g / m ² and the coating content on the back side of the starch exceeds 3.00 g / m ² , coating with coating equipment represented by the existing film transfer system is difficult. Therefore, the operability is greatly reduced, and the paper machine is damaged and the cost burden is increased. Therefore, the starch coating content is preferably 0.50 to 6.00 g / m ^{2 in} total on the front and back sides.

It is also effective to use polyvinyl alcohol (PVA) as a paper strength enhancer. Polyvinyl alcohol does not exhibit a specific ionicity, but has a remarkable effect on coating properties such as fluidity depending on the molecular weight and the degree of saponification. In addition, it is desirable that polyvinyl alcohol having a saponification degree of 90 to 99 mol% is contained in the coating liquid in an amount of 0.30 g / m ² or more in terms of solid content and 0.60 g / m ² or more in terms of the coating content in total. .

“(Surface) sizing agent”
Examples of the surface sizing agent used in the present invention include styrene / acrylic acid (methacrylic acid) copolymers, styrene / acrylic acid ester copolymers or copolymers of these with other monomers, and styrene / maleic acid copolymers. Olefin / maleic acid copolymer, vinyl acetate / maleic acid copolymer, polyacrylamide, polyamine, alkyl ketene dimer, and the like. Examples of acrylic acid (methacrylic acid) esters include methyl, ethyl, propyl, and butyl esters of acrylic acid (methacrylic acid). Other monomers include α-methylstyrene, vinyl toluene, ethylene, propylene, butene, butadiene, acrylic acid, methacrylic acid, and the like. Of these, styrene / acrylic acid ester copolymers, styrene / maleic acid copolymers, and olefin / maleic acid copolymers are preferred. For example, “Polymaron product number 1329” manufactured by Arakawa Chemical Industries, Ltd. and “BLS720” manufactured by Seiko PMC Co., Ltd. may be mentioned. By providing functional layers of these surface sizing agents on the surface of the multilayer paperboard and the surface of the back layer, it is possible to suppress ink absorption at the time of printing and to suppress ink bleeding, thereby improving printability.

"Other"
An anti-slip agent can be used in combination, and as this anti-slip agent, one or more selected from styrene, styrene / acrylic, acrylic and colloidal silica are preferably used. For example, “Kay Coat US200” manufactured by Modern Chemical Industry Co., Ltd. and “Hama Coat G280 / 315” manufactured by Seiko PMC Co., Ltd. may be mentioned. By providing functional layers of these anti-slip agents on the surface and the back layer of the multilayer paperboard, it is possible to prevent the cardboard from slipping when the multilayer paperboard is formed into a cardboard case.

<Specific examples of manufacturing equipment>
(Wet paper forming step 10)
The gap former type first head box 11 in the above manufacturing equipment example is installed upward in a state inclined in the horizontal or downstream side, and when the paper discharge direction line is a horizontal line, the discharge angle θ is 0 degree to 45 degrees. It is desirable that the degree. In the layer structure of the lower layer containing many pulp fibers that have been repeated many times and exhausted, from the viewpoints of formation, Z-axis strength, front / back difference, fiber orientation angle, etc. while performing high speed dewatering under high speed papermaking It is desirable that the head box be an upward head that is less affected by the fiber weight. In the gap type twin wire former, if the head box is vertical, ancillary equipment that enhances the dewatering effect is required under high-speed papermaking, and it is difficult to obtain the characteristics required for a corrugated board liner.

  The upper layer is preferably a long-net type Ford linear system, and the upper layers are preferably combined so that the surface of the wet paper is on the lower layer side. In the Ford Linear method, the surface of the wet paper has a relatively large amount of fine fibers remaining compared to the back surface, and the wet paper can be used for press dehydration in the next process by combining with the lower layer in the wet paper state. While much entanglement with the outer surface is obtained, when spraying a starch dispersion that improves the interlayer adhesion strength described later, the starch dispersion is less likely to be taken into the paper layer, and the interlayer strength can be improved.

  In a multilayer paper machine, for example, when making an upper layer and a lower layer (or via an intermediate layer), it is effective to spray a starch dispersion to improve the interlayer adhesion strength.

  The type of starch used between the layers in this embodiment is not particularly limited. For example, various raw and processed starches such as corn starch (corn starch), potato starch, sweet potato starch, and acetylated tapioca starch should be used. However, corn starch is most suitable in consideration of economic efficiency and compressive strength, which are one of the problems. In addition, as the starch, if it is used in combination with any one of oxidized starch, anionic starch, cationic starch and amphoteric starch, or in combination, the dispersibility of starch between the layers of wet paper is not clear. Better and more preferable.

In the wire part (paper making stage), for example, a spray spray used as a particularly suitable means for providing an aqueous starch solution on the lower wet paper, first, spray spray is a one-fluid or gas-liquid two-fluid spray. Is preferably used. The nozzle diameter in this spraying may be selected from, for example, non-gelatinized starch that does not clog the pores. A nozzle having a diameter of 0.5 to 2.5 mm, preferably 0.8 to 1.5 mm, is appropriately selected. Use. Such spray guns may be provided in a single row in the width direction of the wet paper web, or may be provided in multiple rows, and are devised so as to be sprayed uniformly on the surface of the wet paper web. The pressure of the spray is not particularly limited as long as fine droplets can be obtained with the supplied air pressure, but can be 0.3 to 35 kg / cm ² , preferably 2.0 to 10 kg / cm ² . The discharge rate is 0.4 to 4.0 liters / minute, preferably 1.0 to 3.0 liters / minute. Further, the starch is preferably ungelatinized starch, preferably corn starch having an average particle diameter of 12.0 to 16.0 μm, for example, having a particle diameter that is easy to retain between pulp fibers without gelatinization, and an average particle diameter of 6. Rice starch smaller than 0 μm tends to cause a problem that starch particles flow between fibers forming a paper layer together with dehydration at the wet end, and it is difficult to obtain a sufficient binding force between the wet paper and the upper layer superimposed on the wet paper. Wheat starch, sweet potato, and potato starch with an average particle size exceeding 20.0 μm remain on the surface layer at the wet end, but the variation in the interlaminar strength presumed to be due to the large particle size and the content of starch particles between the paper layers Since there is little (inflow), it does not contribute so much to the improvement of paper interlayer strength like rice starch having an average particle diameter of less than 6.0 μm. Corn starch is preferably corn starch because the starch particle size is polygonal, and the entanglement with the pulp fibers increases when the paper layer is formed.

  In the formation of wet paper, the surface of the wet paper, where fine fibers are difficult to come off with white water, is distributed more than the back of the wet paper, which is easy to come off with white water. It is easy to keep an aqueous suspension of non-gelatinized starch such as corn starch. Preferably, the upper wet paper is further layered on the surface layer sprayed with an aqueous suspension of non-gelatinized starch, and forced dehydration by dehydration in the press part is applied after the layer construction of multiple layers. The aqueous suspension of non-gelatinized starch applied between the surface layer and the wet paper layer diffuses into the wet paper layer and is gelatinized with a dryer to which heat of 100 ° C. or more is applied. The strength inside the layer can be improved.

  Here, when forming a laminated body in which an aqueous solution of starch is provided between wet papers, when two layers of wet paper are laminated, an ungelatinized starch aqueous solution is preferably formed on the lower wet paper (lower layer). It is preferable to laminate the upper wet paper (upper layer) by spraying. On the other hand, when laminating a plurality of wet paper webs of three or more layers, there are a plurality of lower wet paper webs and upper wet paper webs adjacent to each other, but at least one of the lower web papers is targeted. As a result, it is preferable to spray the starch aqueous solution on all lower wet papers.

  Although the preparation method of the water-soluble suspension of the non-gelatinized starch used with the application | coating (spraying) equipment of a spray system is not specifically limited, Preferably it is as follows. That is, first, ungelatinized raw starch is dispersed in water, and preferably an aqueous suspension having a concentration of less than about 10 to 20% so that the final starch paste solution has a concentration of 10% or more. The “ungelatinized starch” as used in the present invention refers to untreated starch that has not been subjected to a treatment for gelatinizing raw starch by heat treatment or the like.

  Application (spraying) of a water-soluble suspension of ungelatinized starch by spraying is also applied to the surface (first wire surface), preferably the back surface (second wire surface) of one of the adjacent wet paper webs. In a configuration suitable for obtaining a core having high compressive strength, which is a subject of the present invention, it is possible to spray, but during the overlap of wet paper immediately after the outlet discharge in the wire part, preferably after the water break line It is preferred that

The starch dispersion can obtain a suitable effect with either gelatinized starch or non-gelatinized starch. However, the interlaminar strength can be further increased by using non-gelatinized starch and gelatinizing with the heat of drying with a dryer.

  The lowermost layer in the papermaking process is formed by a gap former method with a head box that can adjust the concentration in the width direction, and the upper layer is formed by a Ford linear method with a long mesh part, so that functional chemicals are added to the raw pulp Even without this, a cardboard liner having a compressive strength comparable to that of the conventional one can be obtained, and the cardboard liner can be produced efficiently.

  The lowermost layer is preferably formed by a gap former method using a head box 11 capable of adjusting the density in the width direction. Headboxes capable of adjusting the density in the width direction are publicly known, and description of the structure and the like is omitted. For example, “Optic Flow Headbox” manufactured by Metso, Kawanoe Kikai-GL & V “BTF-Dilution System” And so on.

(Dehydration process 20)
As a dewatering facility including a shoe press, a trinip press including a first press, a second press, and a third press from the upstream side to the downstream side is used: the first press includes a pair of suction rolls and a grooved roll; Is a double felt press in which water is squeezed out of wet paper through two felts by a press nip formed by the above, the grooved roll is a rubber coated roll, and its rubber hardness (JIS K6253) is 95 ° or more The second press is squeezed from wet paper through a single felt by a press nip formed by a suction roll and a surface ceramic-coated roll or a surface artificial stone cover roll. Single felt press; said third press is a surface ceramic coated roll or surface artificial stone cover What is a single felt press for performing dewatering from the wet paper through the single felt by a press nip formed by the roll and the shoe press is optimal. This trinip press is used in printing paper applications, but is not normally used as a production facility for cardboard liners.

  In the above press arrangement, the first press usually has a high dewatering load, and in order to obtain symmetry in paper quality, a double felt press that performs dewatering by nip pressure with wet paper sandwiched between two felts. A mechanism is used. In this double nip press mechanism, a suction roll is used on the side where wet paper is transferred to the next stage press, and a grooved roll having a groove for escaping felt water is used as a counterpart roll forming the nip.

  In the present invention, when used for a multilayer paperboard having at least two layers, the grooved roll is a rubber-coated roll, and the rubber-coated roll is formed of a rubber layer having a rubber hardness (JIS K6253) of 95 ° or more. Can be suitably used.

  By using a relatively soft rubber material, it becomes possible to dehydrate slowly without excessively crushing the wet paper of the relatively thick cardboard liner, and a bulky cardboard liner can be obtained.

(Preliminary drying step 30)
The pre-dryer part is a single deck dryer of a no-open draw type, and preferably has a roll configuration with an appropriate number of heating rolls on the upper side and vacuum rolls on the lower side. The single-deck type dryer is capable of drying with high efficiency without reducing bulk in high-speed papermaking of 500 m / min or more, which is an object of the present invention, and is excellent in terms of quality and operation.

  In the single-deck type pre-dryer part, a plurality of dryer rolls are arranged in the upper stage, and a plurality of vacuum rolls are arranged in the lower stage, and strip-like canvases are alternately wound around the dryer roll and the vacuum roll. The paper web (wet paper) dewatered by the upstream press part runs around the dryer roll and the vacuum roll alternately while being supported on one side by the canvas. The paper web is supported on the lower surface side of the canvas. On the dryer roll, the paper web is pressed against the surface of the dryer roll by the canvas and dried by the heat of the dryer roll.

  Drying is advanced early with a single deck type with high drying efficiency and stabilized by double deck type drying in the next process. In the double deck type dryer part, a plurality of dryer rolls are arranged in two stages, an upper stage and a lower stage, respectively, and a canvas is wound around these dryer rolls. The paper web (wet paper) from the press part runs around the upper dryer roll and the lower dryer roll alternately while being supported by the canvas. The paper web is heated and dried by the dryer roll directly or via the canvas in the course of running on the peripheral surface of the dryer roll.

  By combining a single deck type and a double deck type drying method, it is possible to improve operability such as canvas marks in high speed papermaking, paper breaks in high speed drying, wrinkles, and paper splicing.

(Coating process 40)
Conventionally known coating means are used for the coating process, but placing various functional chemicals used for the cardboard liner on the front and back of the paperboard makes it easy to make a difference in the solid content concentration between the front and back and the difference in coating amount. A film transfer system or a pound system that can be attached can be suitably employed.

  The pound-type roll coater is composed of a pair of applicator rolls whose axes rotating at the same peripheral speed as the web are parallel to each other and the outer circumference of the applicator roll is in contact with a line to form a nip. The line connecting the centers of the rolls is horizontal or slightly inclined, and the nip is a coating liquid pond (liquid reservoir), and the web passes through the pond to cause the coating liquid to adhere excessively to the web. After that, it is squeezed at the nip of the applicator roll to adjust the coating amount and allow the coating liquid to penetrate into the web.

  The film transfer system is a coating system typified by a gate roll coater, and includes an outer roll, an inner roll, and a pair of applicator rolls. In this method, a pound of coating liquid is formed in the nip between the outer roll and the inner roll, the coating liquid is transferred from the inner roll to the applicator roll, the coating liquid is transferred to one peripheral surface of the applicator roll, and the web Is transferred to the web as it passes through the nip of the pair of applicator rolls.

  A rod is used instead of the outer roll and the inner roll, the coating liquid is sprayed between the applicator roll and the rod, the coating liquid is scraped off by the rod, transferred to the applicator roll, and the web is further niped between the pair of applicator rolls. The rod metalling method that is transferred to the web when passing through the roller can be suitably used because roll marks are hardly generated.

<About front and back differential coating>
Since the outer surface of the cardboard liner is required to have at least an excellent appearance and good printability, at least a dye that does not maintain the color tone of the raw material pulp and a sizing agent for improving printability are included. It is necessary to apply external chemicals. On the other hand, it is not necessary to consider appearance and printability on the back side, and it is only necessary to place importance on the adhesiveness to the core base paper, and a back side chemical containing a paper strength enhancer is applied.

  Therefore, according to the present invention, according to the difference in front and back quality required for the cardboard liner, different chemicals are applied on the front and back sides, so that the chemical yield can be improved. . In addition, when adding a paper strength enhancer to the raw material pulp in response to the use of waste paper with reduced quality, excessive addition of the paper strength enhancer results in a so-called ruled line during box making because the paper surface becomes too hard. May cause cracking. Therefore, by not applying the paper strength enhancer to the outer surface or by using a small amount, it is possible to prevent the ruled line from being broken during canning even when using waste paper with reduced quality.

  Thus, it will be apparent that the front / back differential coating according to the present invention provides an unexpected advantage.

(Post-drying step 50)
The after-dryer is a double-deck type, and a high-tension canvas is wound around the dryer rolls arranged in two stages above and below, and the surface of the paper web is pressed against the dryer roll with the canvas and restrained. Yes. In addition, a drying device is arranged opposite to the bottom group of dryer rolls, and the drying medium is sprayed onto the back surface of the paper web through a canvas for drying.

  In the coating process, the coated paper with various functional chemicals coated on the front and back surfaces of the cardboard liner has a moisture content of, for example, 10% to 40%. When drying with an after dryer, the front and back surfaces are uniformly dried. It is preferable that the upper dryer roll and the lower dryer roll are circulated alternately while being supported by the canvas, and the front and back surfaces of the paper web are evenly applied directly or by the dryer roll in the process of running the dryer roll peripheral surface. It is heated and dried through a canvas.

(Planarization step 60)
The paperboard obtained by applying various functional chemicals on the front and back sides of the paperboard can be further flattened with calendar equipment such as a machine calendar, soft calendar, super calendar, gloss calendar, etc. preferable. Among these calendar facilities, it is preferable to use a machine calendar from the viewpoints of practicality and the like that can easily impart a Beck smoothness difference or the like on the front and back surfaces of the paperboard.

  A soft calender can also be used, and the paper passing process by the soft calender is preferably performed by adjusting the nip pressure within the range of 5 to 50 kN / m, more preferably 12 to 25 kN / m. If the nip pressure is less than 5 kN / m, the smoothness of the paper surface that did not contact the metal roll in the dryer part may not be sufficiently improved. On the other hand, if it exceeds 50 kN / m, the smoothness of the paper surface may be reduced. There is a risk of becoming too high.

  As for the hardness of the elastic roll of the soft calender, it is preferable that the Shore hardness conforming to “Shore hardness test-test method” described in JIS Z 2246 is about 87 to 95 °. If the Shore hardness is less than 87 °, the durability of the elastic roll may be low, and sufficient smoothness may not be obtained. On the other hand, if it exceeds 95 °, a uniform profile may not be obtained. . In addition, the roughness of the elastic roll is the maximum value of the surface roughness in accordance with “Product Geometric Specification (GPS) —Surface Properties: Contour Curve Method—Terminology, Definition and Surface Property Parameters” described in JIS B 0601. It is particularly preferable that the thickness is less than about 0.5 μm because the suitability for processing in a corrugator for paperboard can be improved. Further, in order to smooth the surface of the soft calender in contact with the metal roll, the surface temperature of the metal roll facing the elastic roll is about 40 to 200 ° C., further about 60 to 150 ° C., particularly about 80 to 120 ° C. It is preferable to do. By setting the surface temperature of the metal roll within such a range, a printing surface with a more uniform density can be obtained, for example, even when printing is performed on the surface that is affected by slight density unevenness.

(Final process)
After flattening, it is wound up by a winder 70 to obtain a cardboard liner product.

As the coating amount (one side) of the coating liquid of the present invention, for example, the following amount (dry solid content amount) is suitable.
Coating liquid for outer surface: sizing agent; 0.10 to 1.00 g / m ² , dye; 0.10 to 1.00 g / m ² , paper strength enhancer; 0.30 to 3.00 g / m ² .
Back surface coating solution: paper strength enhancer; 0.20 to 3.00 g / m ² .

The coating amount of the coating liquid containing a functional chemicals, between the front surface and the back surface of the base paper, 0.5 g / m ² or more in each dry solids, further is adjusted to 1.50 g / m ² or more In addition, it is preferable that the dry solid content is adjusted to 6.00 g / m ² or less, more preferably 5.00 g / m ² or less. When the coating amount of the coating liquid containing functional chemicals is less than 0.50 g / m ^2, it is difficult to obtain sufficient surface strength and quality due to the coating liquid containing the surface treating agent, particularly when the proportion of waste paper pulp is high. Problems arise. If the coating amount exceeds 5.00 g / m ² , problems such as drying ability with an after dryer, uneven effect of functional chemicals, and deterioration in operability will occur, so a coating solution containing a surface treatment agent is necessary. It is desirable not to apply any more.

The liner for corrugated board in the present invention is used in a variety of ways, including starch derived from waste paper, starch used as an intercalation chemical, and starch as a paper strength enhancer. Papermaking with a starch amount of 10.00 g / m ² is preferable for manufacturing cost, prevention of paper machine fouling, and reduction of white water COD load.

  In the outer surface coating liquid, it is desirable that the sizing agent is anionic and the dye is anionic, or the sizing agent is nonionic and the dye is anionic. A paper strength enhancer can be further contained in the outer surface coating solution. In this case, it is preferable that the paper strength enhancer is anionic.

<Manufacture of core base paper>
The said manufacturing equipment can be utilized for manufacture of core raw paper. For example, at the time of manufacturing the core base paper, the outer surface and the rear surface of the wet paper after the pre-drying are each coated with a coating solution containing substantially no coloring dye and containing a paper strength enhancer with substantially the same coating amount. can do.

<About raw pulp>
As a raw material pulp, what contains 50 weight% or more of used paper pulp which consists of corrugated used paper can be used. According to the present invention, even if such raw material pulp is used, it is possible to produce a cardboard liner having necessary characteristics of basis weight of 75 to 290 g / m ² by making paper at a paper making speed of 500 m / min or more.

  The advantages of the present invention are particularly apparent when the pulp slurry used as the raw material for the cardboard liner contains at least 50% by weight of waste paper pulp based on the total dry weight of the pulp. Moreover, the pulp slurry which consists only of used paper pulp may be sufficient, or what mixed other pulp besides used paper pulp may be sufficient.

  Used paper pulp includes corrugated paper, magazine paper, bookbinding, printing factories, cutting offices, cut paper, waste paper, widened waste paper, and unprinted waste paper such as white, extra white, medium white, and white loss. Used paper pulp, high quality paper, high quality coated paper, medium quality paper, medium quality coated paper, reprinted paper, lithographic, letterpress, intaglio printing, electrophotographic system, thermal system, thermal transfer system, pressure sensitive recording system, inkjet A recording system, waste paper printed with carbon paper, water-based, oil-based ink, waste paper written with a pencil, pulp de-inked after dissociation of newspaper waste paper (hereinafter abbreviated as DIP), and the like can be used.

  In addition to the above-mentioned waste paper pulp, virgin chemical pulp (CP: hardwood bleached kraft pulp, softwood bleached kraft pulp, hardwood unbleached kraft pulp, softwood unbleached kraft pulp, hardwood bleached sulfite Pulp, softwood bleached sulfite pulp, hardwood unbleached sulfite pulp, pulp made by chemically treating wood and other fiber materials such as softwood unbleached sulfite pulp), and wood or chips were mechanically pulped Virgin such as semi-chemical pulp that has been soaked with chemical solution into ground pulp, wood or chips, then digested to mechanical soft pulp, chemi-mechanical pulp and chips until slightly softened, and then refined with refiner Pulp may be included. However, it is desirable to minimize the use of virgin pulp from the viewpoint of resource saving and raw material cost.

  The raw material pulp suitably used for the corrugated board liner of the present invention is JAPAN TAPPI No. in the disaggregated pulp obtained by disaggregating the corrugated board liner according to JIS P 8220. The weight average fiber length measured in accordance with No. 52 (hereinafter simply referred to as “weight average fiber length”) is 0.80 to 1.40 mm, more preferably 0.90 to 1.30 mm. Thereby, strength, such as a compressive strength, can be kept constant irrespective of the compounding quantity of used paper pulp. Moreover, since it can prevent that the amount of short fibers increases, generation | occurrence | production of paper dust can be suppressed. Furthermore, the paper thickness decrease in the subsequent head box and press part is reduced, and it is possible to form a paper layer with a good formation, that is, with less uneven thickness. When the weight average fiber length is less than 0.80 mm, the effect of improving the compressive strength is reduced and the amount of short fibers is increased, so that paper dust is likely to be generated. On the other hand, if the weight average fiber length exceeds 1.40 mm, the yield is lowered by the classification process in the manufacturing process, and there are problems in terms of resource saving and cost, and the formation becomes worse, resulting in uneven thickness. Since it becomes easy to do, repeatability deteriorates.

  It is desirable to spray-coat an aqueous solution containing gelatinized starch or ungelatinized starch on at least a part of the paperboard liner.

In the wire part (paper making stage), for example, a spray spray used as a particularly suitable means for providing an aqueous starch solution on the lower wet paper, first, spray spray is a one-fluid or gas-liquid two-fluid spray. Is preferably used. The nozzle diameter in this spraying may be selected from, for example, non-gelatinized starch that does not clog the pores. A nozzle having a diameter of 0.5 to 2.5 mm, preferably 0.8 to 1.5 mm, is appropriately selected. Use. Such spray guns may be provided in a single line in the wet paper width direction, or may be provided in multiple lines, and are devised so as to be sprayed uniformly on the surface of the wet paper. The pressure of the spray is not particularly limited as long as fine droplets can be obtained with the supplied air pressure, but can be 0.3 to 35 kg / cm ² , preferably 2.0 to 10 kg / cm ² . The discharge rate is 0.4 to 4.0 liters / minute, preferably 1.0 to 3.0 liters / minute.

  The starch is preferably non-gelatinized starch, preferably non-gelatinized and having a particle diameter that is easy to retain between pulp fibers, for example, corn starch having a volume average particle diameter of 12.0 to 16.0 μm, and a volume average particle diameter of In rice starch of less than 6.0 μm, starch particles flow into the fibers forming the paper layer with dehydration at the wet end, resulting in a problem that it is difficult to obtain sufficient binding strength between the wet paper and the upper layer superimposed on the wet paper. Wheat starch, sweet potato, and potato starch with a volume average particle diameter of more than 20.0 μm remain on the surface layer at the wet end, but the dispersion of interlaminar strength presumed to be due to the large particle diameter and starch particles between the paper layers Since the content (inflow) is small, the volume average particle diameter is less than 6.0 μm, and it does not contribute so much to the improvement in strength between paper layers as in the case of rice starch. Corn starch is preferably corn starch because the starch particle size is polygonal, and the entanglement with the pulp fibers increases when the paper layer is formed.

  In the formation of wet paper, the surface of the wet paper, where fine fibers are difficult to come off with white water, is distributed more than the back of the wet paper, which is easy to come off with white water. It is easy to keep an aqueous suspension of non-gelatinized starch such as corn starch. Preferably, the upper wet paper is further layered on the surface layer sprayed with an aqueous suspension of non-gelatinized starch, and forced dehydration by dehydration in the press part is applied after the layer construction of multiple layers. The aqueous suspension of non-gelatinized starch applied between the surface layer and the wet paper layer diffuses into the wet paper layer and is gelatinized with a dryer to which heat of 100 ° C. or more is applied. The strength inside the layer can be improved.

  Here, when forming a laminated body in which an aqueous solution of starch is provided between wet papers, when two layers of wet paper are laminated, an ungelatinized starch aqueous solution is preferably formed on the lower wet paper (lower layer). It is preferable to laminate the upper wet paper (upper layer) by spraying. On the other hand, when laminating a plurality of wet paper webs of three or more layers, there are a plurality of lower wet paper webs and upper wet paper webs adjacent to each other, but at least one of the lower web papers is targeted. As a result, it is preferable to spray the starch aqueous solution on all lower wet papers. Although the preparation method of the water-soluble suspension of the non-gelatinized starch used with the application | coating (spraying) equipment of a spray system is not specifically limited, Preferably it is as follows. That is, first, ungelatinized raw starch is dispersed in water, and an aqueous suspension having a concentration of less than about 5 to 20% is preferably formed so that the final starch paste solution has a concentration of 5% or more. The “ungelatinized starch” as used in the present invention refers to untreated starch that has not been subjected to a treatment for gelatinizing raw starch by heat treatment or the like. Application (spraying) of a water-soluble suspension of ungelatinized starch by spraying is also applied to the surface (first wire surface), preferably the back surface (second wire surface) of one of the adjacent wet paper webs. In a configuration suitable for obtaining a corrugated liner having a high compressive strength, which can be sprayed, which is a subject of the present invention, while the wet paper is superimposed immediately after the inlet discharge in the wire part in the gap former, Preferably, the wet paper is sprayed from between the two wires immediately after exposure, and in Ford Linear, it is preferably sprayed immediately after the water break line.

<About the color of the liner for cardboard>
In the present invention, the outer surface chemicals containing at least a sizing agent and a dye are applied to the outer surface of the wet paper after the preliminary drying. In this case, for example, a color sensor (for example, an MxOpen type color sensor manufactured by Honeywell or a 2000ET color sensor, a Macbeth fixed point measurement color sensor) 80 is provided in the vicinity of an existing so-called BM meter provided on the outlet side of the calendar 61. Based on the color tone, it is preferable to adjust the dye to be given to the size press (mixing of yellow, black and magenta and adjusting the addition amount). Fortunately, the present invention does not add the dye internally, but applies the dye together with the sizing agent at the size press site, so there is an advantage that the color tone variation in the manufacturing process can be quickly fed back and adjusted. is there.

  Next, an example is shown and the effect of this invention is clarified.

  Type of raw material pulp, origin of used paper, presence / absence of density adjustment function of head box, type and amount of paper strength enhancer, type and amount of sizing agent, presence / absence of dye addition in size press, coating amount The characteristics obtained were investigated by changing the above. The results are shown in the table.

In addition, the planarization process in Examples 11 to 17 of the present invention is performed under soft calender conditions of an elastic roll hardness of 90 °, a planarization temperature of 100 ° C., and a nip pressure of 20 kN / m. It is as follows.
Oxidized starch: Ace AT-110 (manufactured by Oji Cornstarch)
Amphoteric starch: Cato3210 (NSC Japan)
Ester-modified starch: Corn Pol CP-5 (manufactured by Oji Cornstarch)
Raw starch: Corn starch (manufactured by Oji Corn Starch)
Cationic starch: EX-3 (manufactured by Nissho Chemical Co., Ltd.)
PVA: PVA110 (manufactured by Kuraray)
Copolymerized PAM: Polyaclon ST-13 (manufactured by Seiko Chemical Co., Ltd.)

It is a schematic diagram of the upstream process of the example of manufacturing equipment concerning the present invention. It is a schematic diagram of the downstream process of the example of manufacturing equipment concerning the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Wet paper formation process, 20 ... Dehydration process, 30 ... Pre-drying process, 40 ... Coating process, 50 ... Post-drying process, 60 ... Flattening process.

Claims (4)

A method for producing a corrugated board liner, comprising producing a liner for corrugated board having a basis weight of 75 to 290 g / m ² for paper making at a paper making speed of 500 m / min or more.
The following processes (1) to (6) are incorporated in order.
(1) A papermaking process for forming a wet paper having at least two layers by combining at least a layer made by a gap former method and a layer made by a Ford linear method having a long mesh part,
(2) a dehydration step of dehydrating the wet paper with a dehydration facility including a shoe press;
(3) a pre-drying step of pre-drying the dehydrated wet paper;
(4) A coating process in which an outer surface chemical containing at least a sizing agent and a dye is applied to the outer surface of the wet paper after preliminary drying, and a rear surface chemical including at least a paper strength enhancer is applied to the rear surface;
(5) A post-drying step for drying the coated paper after coating,
(6) A flattening step of flattening the surface of the coated paper with a flattening facility.   The method for producing a corrugated board liner according to claim 1, wherein the raw material pulp contains 50% by weight or more of used paper pulp made of corrugated used paper.   The manufacturing method of the liner for corrugated boards of Claim 1 or 2 with which a coating process coats with the size press which consists of a film transfer system or a pound system. In the dewatering process, using a trinip press comprising a first press, a second press and a third press from the upstream side to the downstream side:
The first press is a double felt press in which water is squeezed from wet paper through two felts by a press nip formed by a pair of suction rolls and grooved rolls, and the grooved rolls are covered with rubber. A roll having a rubber layer having a rubber hardness (JIS K6253) of 95 ° or more;
The second press is a single felt press that squeezes water from a wet paper through a single felt by a press nip formed by a suction roll and a surface ceramic-coated roll or a surface artificial stone cover roll;
The third press is a single felt press that squeezes water from a wet paper through a single felt by a press nip formed by a surface ceramic-coated roll or a surface artificial stone cover roll and a shoe press;
The manufacturing method of the liner for corrugated boards of Claim 1 or 2.

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