JP2019189978A - Manufacturing method of coated paperboard - Google Patents

Abstract

To provide a coated paperboard which is capable of bearing high quality printing on a surface layer side even when containing a waste paper pulp at high mixing rate, and is suitable to manufacture a paper container such as a box.SOLUTION: In the method, by using a paper machine having at least a wire part 1, a press part 2, a drier part 3, and a coater part 4, a size press being provided in the middle of the drier part 3, a process liquid containing a polyvinyl alcohol-based resin is applied in the size press in the drier part 3 to a surface of a back layer of a base paper having at least a surface layer and the back layer and whose 70 mass% or more of the pulp component comprises a waste paper pulp, then a surface pigment coating liquid containing a pigment and a binder is applied to a surface of the surface layer of the base paper in the coater part 4.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a coated paperboard. More specifically, the present invention relates to a coated paperboard that is suitably used for manufacturing a paper container such as a box.

A coated paperboard having a printability imparted by applying a coating liquid containing a pigment and a binder to the surface layer side of a base paper composed of a multilayer paper having a surface layer and a back layer is generally used for paper containers (boxes, Blister packs, etc.), paper products (sample book mounts, albums, etc.), publishing (magazines, books, etc.), commercial printing (catalogs, brochures, etc.), etc.
In the production of coated paperboard, in recent years, saving of wood resources and paper recycling have been encouraged from the viewpoint of protecting the global environment, and the use of used wastepaper as a raw material for pulp has been widely performed.

  When used paper is known to be less rigid than virgin pulp, there is a problem that the use of a large amount of used paper works negatively for paper for applications that require rigidity. In the production of paperboard for these applications using waste paper, the basis weight is increased, the density is made as low as possible to increase the thickness, the paper is made bulky, or a relatively stiff softwood pulp is blended. Measures such as internal addition of various sizing agents, paper strength enhancing agents, size press coating, and in some cases, progressing beating of used pulp have been taken in actual operations at factories.

In recent years, as the ratio of used paper increases, the surface strength of the paperboard becomes insufficient, and there is a tendency that a so-called white spot problem that a part of the printing is lost due to the dropped fibers tends to occur.
So, in patent document 1, after apply | coating a coating liquid to the surface layer side of a base paper, the coating liquid containing a pigment and a binder is apply | coated also to the back layer side, and the pulp fiber of a back layer is coat | covered and fixed. It has been proposed to increase white spot resistance.

JP 2000-192395 A

However, the coated paperboard obtained by the method of Patent Document 1 has insufficient surface quality of the coating layer on the surface layer side.
In addition, recently, the ratio of used paper has further increased, and the amount of used paper that is unsuitable for reuse as paper has increased, and the problem of white spots tends to occur more easily. In particular, when the back layer contains pulp derived from a shredded product such as office paper or pulp derived from waste gypsum board, the tendency is strong because it contains fine fibers.
Considering only securing the surface strength, it is conceivable to apply a paper strength enhancer with a size press.

However, if the coating amount of a paper strength enhancer or the like is increased unnecessarily, the paste permeability and the bending ability necessary for manufacturing a paper container such as a box are impaired.
In view of the above circumstances, the present invention is a coated paperboard that is capable of performing high-quality printing on the surface layer side while being highly blended with used paper pulp, and is easy to use for the manufacture of paper containers such as boxes. It is a problem to obtain.

In order to achieve the above object, the present invention employs the following configuration.
[1] At least a wire part, a press part, a dryer part, a coater part, and using a paper machine having a size press in the middle of the dryer part,
In the wire part, at least a surface layer and a back layer are formed, and a base paper in which 70% by mass or more of all pulp components is waste paper pulp is formed,
In the size press in the dryer part, a treatment liquid containing a polyvinyl alcohol-based resin is applied to the surface of the back layer of the base paper,
A method for producing a coated paperboard, wherein a surface pigment coating solution containing a pigment and a binder is applied to the surface of the surface layer of the base paper at the coater part.
[2] The method for producing a coated board according to [1], wherein the size press is a size press of a film transfer system.
[3] The method for producing a coated paperboard according to [1] or [2], wherein the degree of saponification of the polyvinyl alcohol-based resin is 85 mol% or more.
[4] The coating amount of the treatment liquid applied to the surface of the back layer is any one of [1] to [3], which is 0.1 to 7.5 g / m ² in terms of dry mass. Manufacturing method of coated paperboard.
[5] The back layer contains at least one kind of pulp selected from the group consisting of pulp derived from a shredder-treated product and pulp derived from waste gypsum board, according to any one of [1] to [4]. Manufacturing method of coated paperboard.
[6] The at least one pulp selected from the group consisting of the pulp derived from the shredder treated product and the pulp derived from waste gypsum board is 2 to 30% by mass of the pulp constituting the back layer. Manufacturing method of coated paperboard.
[7] The coated paperboard according to any one of [1] to [6], wherein the treatment liquid contains at least one pigment selected from the group consisting of kaolin, talc, calcium carbonate, and titanium dioxide. Production method.
[8] The method for producing a coated paperboard according to any one of [1] to [7], wherein the treatment liquid contains a polyacrylamide resin.

  According to the method for producing a coated paperboard of the present invention, it is possible to perform high-quality printing on the surface layer side while using a high amount of waste paper pulp, and it is easy to use for the production of paper containers such as boxes. A coated paperboard can be obtained.

It is a whole block diagram which shows an example of the paper machine used for the manufacturing method of the coated paperboard of this invention. It is a block diagram which shows an example of the dryer part of the paper machine used for the manufacturing method of the coated paperboard of this invention.

[Paper machine]
FIG. 1 is an overall configuration diagram showing an example of a paper machine used in the method for producing a coated paperboard of the present invention. The paper machine of FIG. 1 is connected to the wire part 1, the press part 2 connected to the downstream side of the wire part 1, the dryer part 3 connected to the downstream side of the press part 2, and the downstream side of the dryer part 3. The coater part 4 is provided. Further, a calendar part or the like may be provided between the dryer part 3 and the coater part 4 or on the downstream side of the coater part 4.

As the wire part 1, the wire part currently used with the well-known multilayer paper machine can be used suitably. For example, it has at least two or more wire part parts. The wire part type generally used for papermaking includes a circular net type, a long net type, a short net type, an inclined type, and a twin wire type.
In multi-layer papermaking, these methods can be combined. For example, there are a long mesh patterning, a short mesh patterning, a short mesh pattern combination, a long mesh pattern combination, and the like.

Among them, it is preferable to use short netting in terms of improving the yield of waste paper pulp containing a lot of fine fibers.
The paper making speed is not particularly limited, but is 1000 m / min or less. In the case of a speed exceeding 1000 m / min, the dehydration and squeezing in the wire part and the following press part are performed firmly, so that the fine fibers fall off and the yield decreases. The preferred paper making speed is 70 to 700 m / min, which will be described in the description of the size press part 18 later.

  As the press part 2, a known press can be used as appropriate, but a shoe press is preferably included. It is also preferable to combine a roll press and a shoe press. When a shoe press is used, water can be sufficiently squeezed in the press part 2, so that it is easy to control the amount of water when performing size pressing with the dryer part 3.

  For example, as shown in FIG. 2, the dryer part 3 includes a pre-dryer part 16, a size press part 18 connected to the downstream side of the pre-dryer part 16, and an after dryer part connected to the downstream side of the size press part 18. 20.

The pre-dryer part 16 is a part that heats a plurality of cylinder dryers 26 in contact with the wet base paper 10 to evaporate a part of the moisture in the base paper 10.
The after dryer part 20 is a part which contacts the base paper 10 after the coating by the size press part 18 and heats the plurality of cylinder dryers 30 to dry the base paper 10 and the coating liquid.

  The after dryer part 20 may change a part of the cylinder dryer into a non-contact dryer, for example, an infrared dryer, a hot air dryer, a Yankee dryer, or the like. Use of a non-contact dryer is preferable because the treatment liquid applied by the size press part 18 can be prevented from adhering to a cylinder or the like. Further, as the cylinder dryer, a cylinder dryer whose surface is processed with fluorine or a cylinder dryer which is mirror-finished are excellent and preferable from the viewpoint of adhesion prevention.

  The size press part 18 includes a size press 28 having a pair of rolls 28a. The treatment liquid is applied to the back layer of the base paper 10 while allowing the base paper 10 having a moisture content of about 6 to 20% by mass to pass between the pair of rolls 28a. Further, a treatment liquid or the like is applied to the surface layer of the base paper 10 as necessary.

The size press 28 supplies a processing liquid or the like to a nip portion formed between the roll 28a and the paper to create a so-called pound system called a pound, and a processing liquid or the like on the surface of the roll 28a. There is a film transfer system in which a film (film) is formed and this film is transferred to paper.
Either of the size presses in the present invention can be used, but a film transfer system is preferred.
In the case of the pound method, a nip pressure is applied between the rolls 28a to form a pound, so that the gap of the base paper to be passed may be crushed and the whiteness of the base paper surface may be lowered. The decrease in whiteness is probably due to the color components in the disintegrated pulp used for the middle layer and the like moving to the surface layer.

Examples of the film transfer type size press include a rod metalling method, a gate roll method, and a blade metalling method. Among the film transfer type size presses, the rod metalling type or the gate roll type is preferable.
The rod metering system is a system in which a film is formed on a roll 28a, which is an applicator roll, via a rod, and the formed film is transferred from the roll 28a to paper.
The size press of the gate roll system is such that a metalling roll rotating in the opposite direction to the roll 28a is brought into contact with the outer side of the roll 28a as an applicator roll, and further, a fountain roll rotating in the opposite direction to the metalling roll on the outer side. And make a pound between the metering roll and the fountain roll. Then, a coating such as a treatment liquid formed on the surface of the metering roll is transferred to the roll 28a which is an applicator roll, and then transferred from the roll 28a to the paper.
The blade metering method is a method of forming a film with a certain thickness on the roll 28a by scraping off the treatment liquid or the like attached to the roll 28a, which is an applicator roll, and transferring the formed film from the roll 28a to the paper. It is.

  Once the film of the treatment liquid is formed, the film transfer type size press that transfers the film to the base paper, when the paper making speed is high, before the polyvinyl alcohol resin constituting the treatment liquid has sufficiently penetrated the base paper from the film. It may dry out. Accordingly, the paper making speed is preferably 700 m / min or less, more preferably 600 m / min or less, and further preferably 500 m / min or less. The lower limit is not particularly limited, but considering productivity, it is preferably 70 m / min or more, more preferably 150 m / min or more, and further preferably 300 m / min or more.

When a calendar part (precalender) is provided between the dryer part 3 and the coater part 4, the base paper 10 after the coating is formed is passed between rolls and tightened. Thereby, the base paper can be smoothed. As a result, the surface pigment coating layer formed in the later coater part 4 becomes smooth, and a uniform coating layer can be obtained.
In the calendar part, any calendar device may be used, in which the base paper is sandwiched between a metal roll and a metal roll, or in which the base paper is sandwiched between a metal roll and a resin roll.

As the coater part 4, a known coating apparatus attached to the paper machine can be used. For example, a blade coater, an air knife coater, a roll coater, a reverse roll coater, a bar coater, a curtain coater, a slot die coater, a gravure coater, A Champlex coater, a brush coater, a slide bead coater, a two-roll or metering blade type size press coater, a bill blade coater, a short dwell coater, a gate roll coater, a nip coater using a calendar, and the like are appropriately used.
Among these, a rod metering coater and a curtain coater are preferable because the coating amount is constant, so that a coating layer with reduced coating unevenness can be obtained. In addition, the coated coating layer is dried with a well-known drying apparatus, and a surface pigment coating layer is formed. A plurality of coater parts 4 may be provided. In this case, the surface pigment coating layer can be applied in a plurality of times.

A calendar part may be provided after the coater part 4 as necessary. By providing the calendar part after the coater part 4, the surface pigment coating layer is smoothed.
For the calendar part after the coater part 4, a known calendar device can be used as appropriate, and examples thereof include a super calendar, a gloss calendar, a soft nip calendar, a thermal calendar, and a shoe calendar. These may be used in combination. Among these, a soft nip calender provided with a metal roll and an elastic roll is preferable because it can smooth the coating layer while maintaining the paper thickness. The calendar part after the coater part 4 may be on-machine or off-machine.

[Production method]
The present invention uses the above paper machine to form a base paper having at least a surface layer and a back layer in the wire part 1, squeezes moisture with the press part 2, dries with the dryer part 3, and in the dryer part 3. With a size press, a treatment liquid containing a polyvinyl alcohol resin is applied to the surface of at least the back layer of the base paper, and a coater part 4 is used to apply a surface pigment coating liquid containing a pigment and a binder to the surface of the base paper. It is a manufacturing method of the coated paperboard to apply | coat.

  When the paper machine shown in FIG. 1 is used, first, the wet base paper 10 obtained by dewatering with the wire part 1 and squeezing with the press part 2 is introduced into the dryer part 3, and then with the pre-dryer part 16 to some extent. After removing the water, the treatment liquid is applied by the size press 28 and then dried by the after dryer part 20. Thereafter, in the coater part 4, a pigment coating solution is applied to the surface of the surface layer.

"Base paper"
The base paper in the present invention is a multilayer papermaking in which at least a surface layer and a back layer are laminated. The surface layer is a layer disposed on the most front side in the base paper for multilayer papermaking, and the back layer is a layer disposed on the most back side (opposite to the surface layer). An intermediate layer may be provided between the surface layer and the back layer. A surface lower layer may be provided between the surface layer and the middle layer. A back lower layer may be provided between the back layer and the middle layer. Each layer may be formed by a single layer or a plurality of layers, but in order to increase the amount of low-quality waste paper pulp used, it is preferable to form the middle layer by a plurality of layers.

  The base paper in the present invention contains pulp as a main component, and 70% by mass or more of all pulp components constituting the base paper is waste paper pulp. The ratio of waste paper pulp in the total pulp components is preferably 75 to 100% by mass, and more preferably 80 to 95% by mass.

In the present invention, the used paper pulp is a pulp obtained by recycling used paper.
As used paper, for example, white paper and ruled white paper that has been used once, but has few printed parts, printed matter such as cards, imitations, color, Kent, white art, and colored paper that has been used once, Used high-quality used paper such as coated paper for printing, beverage packs, office paper, etc.Furthermore, medium-quality used paper such as tickets / medium anti-old / Kent Manila, general medium-sized used paper such as newspapers / magazines / miscellaneous paper, Examples include tea-based waste paper such as cut tea, plain tea, miscellaneous bags, cardboard, and waste paper from waste gypsum board. The gypsum board is obtained by coating the surface of a core material mainly composed of gypsum with a base paper for gypsum board. Used paper such as office paper and tickets having confidentiality may be a shredder processed product.
As the waste paper pulp, a disintegrated pulp obtained by disaggregating used paper, an unbleached deinked pulp subjected to a disaggregating process and a deinking process, a bleached deinked pulp subjected to a bleaching process after the deinking process, and the like can be appropriately used.

  Examples of so-called virgin pulp that is not waste paper pulp include, for example, softwood unbleached kraft pulp (NUKP), hardwood unbleached kraft pulp (LUKP), softwood bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), and hardwood half bleached Kraft pulp (LSBKP), softwood semi-bleached kraft pulp (NSBKP), hardwood sulfite pulp, softwood sulfite pulp and other chemical pulp, thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), chemiground pulp (CGP), refiner Examples include mechanical pulps such as ground pulp (RGP), ground pulp (GP), pressed stone ground pulp (PGW), and stone ground pulp (SGP).

The pulp constituting the base paper is 70% by mass or more of waste paper pulp as a whole, but the blending ratio of the waste paper pulp can be appropriately adjusted for each layer according to the role of each layer. Moreover, the kind of used paper pulp used for each layer can also be suitably selected according to the role of each layer for every layer.
In any layer, two or more kinds of used paper pulp may be mixed and used. Moreover, when using virgin pulp, you may mix and use 2 or more types of virgin pulp.
Hereinafter, although the normal pulp composition etc. in each layer are demonstrated, this invention is not limited to the following normal pulp composition etc.

  For the surface layer, pulp with high whiteness is usually used. For example, the above-mentioned virgin pulp or waste paper bleached deinked pulp can be mainly used. As the used paper, used paper with high whiteness such as upper white / card, extra white / middle white / white Manila, imitation / color, etc. can be preferably used.

The basis weight of the surface layer is preferably set to 15~90g / ^{m 2,} and more preferably a 25~70g / ^{m 2.} The basis weight of each layer constituting the base paper can be measured according to JIS P8124.
If the basis weight of the surface layer is equal to or more than the preferred lower limit value, the darkness of the middle layer can be sufficiently concealed. Further, if the basis weight of the surface layer is not more than the preferred upper limit value, sufficient paper layer strength can be obtained.

  When providing a surface lower layer, the pulp which comprises a surface lower layer uses the pulp whose whiteness is higher than the pulp of a middle layer, and whiteness is lower than the pulp of a surface layer. Although the pulp used for the surface layer may be used for the surface layer, usually, low-grade waste paper compared to the surface layer, that is, waste paper containing a lot of medium fibers is used. For example, deinked waste paper pulp such as newspapers, magazines, colors, and balls is generally used.

Table lower basis weight is preferably in a 15~90g / ^{m 2,} and more preferably a 25~75g / ^{m 2.}
If the basis weight of the surface lower layer is equal to or more than the preferable lower limit value, the blackness of the middle layer can be sufficiently concealed together with the surface layer. Further, if the basis weight of the front and lower layers is not more than the preferred upper limit value, sufficient paper layer strength can be obtained.

The middle layer is usually composed of a plurality of layers, but may be a single layer. When the middle layer is composed of a plurality of layers, the pulp constituting each layer may be all the same or different.
Since the middle layer is a layer sandwiched at least between the front layer and the back layer, usually the lowest pulp among the layers constituting the base paper is generally used. For example, disintegrated pulps such as newspapers, magazines, tickets, medium-sized antiquity, tea imitation, corrugated cardboard, mounts, ground cards, balls, etc. can be mentioned.
The total basis weight of the middle layer is appropriately adjusted according to the thickness required for the application of the coated paperboard, but the basis weight per layer is preferably 15 to 90 g / m ^2, and preferably 25 to 75 g. / M ² is more preferable.

  When providing a back lower layer, the pulp which comprises a back lower layer uses the pulp whose whiteness is higher than the pulp of a middle layer, and whiteness is lower than the pulp of a back layer. For the back and bottom layers, the surface layer and the pulp used for the top and bottom layers may be used. Usually, however, waste paper that is lower in comparison with the surface layer, that is, waste paper containing a lot of medium fibers is used. For example, unbleached waste paper pulp such as newspapers, magazines, colors and balls is generally used.

The basis weight of the lower back is preferably in a 15~90g / ^{m 2,} and more preferably a 25~75g / ^{m 2.}
If the basis weight of the back lower layer is equal to or more than the preferred lower limit, the colored foreign matter in the middle layer can be sufficiently concealed together with the back layer. Moreover, if the basis weight of the back lower layer is not more than the preferable upper limit value, sufficient paper layer strength can be obtained.

  For the back layer, whiteness as high as the surface layer is not required, but in order to touch human eyes, pulp having whiteness higher than that of the middle layer is usually used.

The basis weight of the backing layer is preferably in a 15~90g / ^{m 2,} and more preferably a 25~70g / ^{m 2.} The basis weight of the middle layer is appropriately adjusted according to the thickness required by the application of the coated paperboard.
If the basis weight of the back layer is at least the preferred lower limit, the colored foreign matter in the middle layer can be sufficiently concealed. In addition, if the basis weight of the back layer is equal to or less than the preferable upper limit value, sufficient paper layer strength can be obtained.

  In the manufacturing method of this invention, it is preferable to make the basic weight of a surface layer smaller than the basic weight of a surface layer, and to make the basic weight of a surface layer lower than the basic weight of a middle layer. More preferably, the basis weight of the front and lower layers is equal to or less than the basis weight per layer of the multi-layered middle layer. By reducing the basis weight of the surface layer and the lower layer and increasing the basis weight of the middle layer, the blending amount of the base paper of the disaggregated waste paper can be increased.

When at least one kind of pulp selected from the group consisting of pulp derived from a shredder-treated product and pulp derived from waste gypsum board is used as the waste paper pulp, it is preferably blended in this backing layer. Since shredded products such as office paper and tickets are collected in a finely cut state, the resulting pulp is a pulp with a lot of fine fibers. Since the pulp derived from the waste gypsum board is recovered in a state where the gypsum is peeled off from the paper used for the gypsum board, the obtained pulp is a pulp having a lot of fine fibers. When such a pulp is used, the coated paperboard can be stably produced by blending in the back layer and fixing with a treatment liquid containing a polyvinyl alcohol-based resin by a size press.
At least one kind of pulp selected from the group consisting of pulp derived from shredded products such as office paper and pulp derived from waste gypsum board is preferably 2 to 40% by mass of the pulp constituting the back layer, and 3 to 30 More preferably, it is mass%.

  The above-described pulp slurry composition used for each layer from the surface layer to the back layer, if necessary, paper strength enhancer, water resistant agent, water repellent, foamable microcapsule, sizing agent, dye, Yield improver, filler, pH adjuster, slime control agent, thickener, preservative, fungicide, antibacterial agent, flame retardant, antiseptic, rodenticide, insect repellent, moisturizer, freshness retainer, oxygen scavenger , Microcapsules, foaming agents, surfactants, electromagnetic shielding materials, antistatic agents, rust inhibitors, fragrances, deodorants and the like can be selected and blended. These can be used in combination.

"Processing liquid"
The treatment liquid contains a polyvinyl alcohol resin.
When the treatment liquid is applied to at least the surface of the back layer by the size press 28, the polyvinyl alcohol-based resin fixes the surface of the back layer and the fine fibers in the vicinity thereof to prevent the fine fibers from dropping off from the back layer side. Conceivable.

A polyvinyl alcohol-based resin (hereinafter also referred to as PVA) is a portion of polyvinyl acetate or a completely saponified product, and has a vinyl alcohol unit. PVA may have vinyl acetate units. PVA may further have other monomer units other than vinyl alcohol units and vinyl acetate units.
The other monomer may be any monomer copolymerizable with vinyl acetate, such as olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-octadodecene, acrylic acid, methacrylic acid, and the like. Unsaturated acids such as acids, crotonic acid, maleic acid, maleic anhydride, itaconic acid or salts thereof, mono- or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as acrylamide and methacrylamide, ethylene sulfone Acids, olefin sulfonic acids such as allyl sulfonic acid, methallyl sulfonic acid or salts thereof, alkyl vinyl ethers, N-acrylamidomethyl ammonium chloride, allyl trimethyl ammonium chloride, dimethyl diallyl ammonium chloride, etc. Compounds having one group, vinyl chloride, vinylidene chloride, but may include copolymers saponified unsaturated monomer having a polyoxyalkylene group, it is not necessarily limited thereto. Further, it may be post-modified such as cyanoethylation, urethanization, esterification, or further end-modified with mercaptan or the like.

The average degree of polymerization of PVA is not particularly limited, but is preferably 1700 or less, and more preferably 1300 or less. If the average degree of polymerization is 1700 or less, the coating properties of the treatment liquid are excellent, and coating unevenness is less likely to occur when the treatment liquid is applied.
The degree of polymerization of PVA is measured according to JIS K 6726.

The saponification degree of PVA is not particularly limited, but is preferably 85 mol% or more, and more preferably 90 mol% or more. When the degree of saponification is high, water in the surface layer pigment coating solution to be applied in the subsequent step can be maintained without dissolving even when it comes into contact with PVA in a dry state, and thus it has excellent whiteout resistance.
The degree of PVA is measured according to JIS K6726.

The treatment liquid preferably contains a paper strength enhancer in addition to PVA. Thereby, the strength on the back layer side is secured and white spots are easily suppressed.
Examples of the paper strength enhancer include polyacrylamide resin (PAM), starch, styrene-butadiene copolymer, styrene-acrylate copolymer, polyamide-epichlorohydrin resin, and the like. Any one of these paper strength enhancing agents may be used alone, or two or more thereof may be used in combination. Among these, PAM is preferable in that the effect of the present invention is more excellent.
When PVA and PAM are used in combination, the effect of PVA film formation is to prevent fine fibers from falling off the surface of the back layer, and to prevent the fine fibers existing inside the PAM from falling inside the back layer. It is assumed that

  PAM is a polymer having (meth) acrylamide units. “(Meth) acrylamide” is a general term for acrylamide and methacrylamide. The PAM may have either one of acrylamide units or methacrylamide units, or may have both. PAM may have units other than (meth) acrylamide units.

Examples of PAM include anionic PAM, cationic PAM, amphoteric PAM, and nonionic PAM. Each of these can be used as a paper strength agent in the field of papermaking, for example, those described in JP-A-2002-317393, JP-A-2004-231901, JP-A-2014-205938, etc. It is done.
PAM may be used alone or in combination of two or more. In view of availability, anionic PAM is preferable.
Anionic PAM contains an anionic functional group such as a carboxy group, a sulfonic acid group, a phosphoric acid group, and a salt thereof. For example, a co-polymer of (meth) acrylamide and an anionic functional group-containing monomer (such as acrylic acid). And a partial hydrolyzate of poly (meth) acrylamide.

The treatment liquid may contain a pigment in addition to PVA. Examples of the pigment generally include pigments and fillers used for application to paper or paperboard or internal addition to paper. Specific examples include magnesium carbonates; calcium and magnesium carbonates such as dolomite; kaolin, natural clay, calcined clay, wax, bentonite, feldspar, talc, mica, wollastonite, synthetic silicic acid Silicates such as aluminum and synthetic calcium silicate; Hydrous aluminosilicates such as natural zeolite and synthetic zeolite; Silicates such as diatomaceous earth, quartzite powder, hydrous finely divided silicic acid (white carbon), anhydrous finely divided silicic acid; Aluminum such as synthetic aluminum hydroxide Hydrate; Barium sulfate such as barite and blank finks; Calcium sulfate such as gypsum and synthetic calcium sulfite; calcium sulfite; Titanium dioxide such as anatase type titanium dioxide and rutile type titanium dioxide; Lithium aluminum carbonate; It is done. Of these, kaolin, talc, and calcium carbonate are preferable.
When the treatment liquid contains a pigment, the coating layer formed from the treatment liquid can be prevented from cracking when the coated paperboard is processed into a box or the like. In particular, kaolin and talc are plate-like pigments, and when used, the number of micro-projections on the back surface is relatively small, and even if the surface and the back surface are rubbed after offset printing, the surface printed layer is hardly roughened. Calcium carbonate and titanium dioxide are white pigments, which are preferable because they can increase the whiteness of the back layer and improve printability. In particular, kaolin as a plate-like pigment and calcium carbonate as a white pigment are preferable pigments.

  The average particle diameter of the pigment is preferably 0.1 to 2.5 μm, and more preferably 0.1 to 1.5 μm. It is preferable that the average particle diameter of the pigment is equal to or more than a preferable lower limit value, because dropping of fine fibers is suppressed. It is preferable that the average particle diameter of other pigments is less than or equal to the preferable upper limit value because micro protrusions can be reduced on the coated surface.

When the pigment is blended in the treatment liquid, the blending amount is not particularly limited, but the pigment is preferably contained in an amount of 10 to 2500 parts by mass, more preferably 15 to 1000 parts by mass with respect to 100 parts by mass of PVA. .
When the pigment is added to the treatment liquid within the above range, it is easy to obtain sufficient interlayer strength, and it is excellent in punching suitability during box making and folding suitability during box making.

  The treatment liquid is appropriately adjusted with a dispersant, a pH adjuster such as sodium hydroxide / ammonia water, an antifoaming agent, a fluorescent dye, a mold release agent, a water resistant agent, a fluidity improver, a water retention agent, and slime. You may contain 1 or more types, such as a control agent, antiseptic | preservative, dye, and a color pigment.

The coating amount of the treatment liquid is preferably from 0.1~7.5g / ^{m 2,} is preferably 1 to 6 g / ^{m 2,} further preferably 1.5 to 4 g / ^{m 2} . In addition, in this specification, the coating amount means the coating amount in terms of dry mass.
When the coating amount of the treatment liquid is equal to or more than the preferable lower limit value, it is easy to obtain sufficient strength on the back layer side. If the coating amount of the treatment liquid is equal to or less than the preferred upper limit value, it is easy to ensure the suitability for folding at the time of box molding and the penetration of glue.
In general, starch, vinyl acetate resin emulsion adhesive, vinyl acetate resin solvent adhesive, acrylic resin emulsion adhesive, and the like are used as the paste.

  When applying the treatment liquid to the back layer side with the size press, there is no limitation on the size press on the surface layer side. The treatment liquid applied on the back surface may be applied, or nothing may be applied. When applying the treatment liquid, the treatment liquid applied to the back layer and the treatment liquid applied to the surface layer do not have to be exactly the same, and the coating amount may not be the same.

If nothing is applied, the evaporation of water on the surface layer proceeds, and in some cases there is a risk of curling trouble. In addition, a part of the treatment liquid on the back surface may wrap around to the surface layer side. At that time, the coating liquid that has wrapped around is immediately dried and accumulates as debris. The accumulated waste may then fall off and cause troubles such as contamination of the cylinder dryer 30 and the like in the after dryer part 20 after the size press. In addition, the surface side surface may be excessively dried, and components such as pitch may come out.
For this reason, in the size press, it is preferable to apply water, the treatment liquid used for the back surface, or the surface side size press liquid described below to the surface on the surface layer side.

"Surface size press liquid"
An aqueous coating liquid is used as the surface-side size press liquid.
Accumulation of residue can be suppressed by, for example, blending a release agent with the surface-side size press liquid. Examples of the release agent include higher fatty acids such as stearic acid, oleic acid, and palmitic acid and salts thereof such as calcium, zinc, sodium, and ammonium, stearic acid amide, ethylene bis stearic acid amide, and methylene bis stearic acid amide. Higher alcohols such as amides, cetyl alcohol and stearyl alcohol, fats and oils such as funnel oil and lecithin, hydrocarbons such as microcrystalline wax, paraffin wax and polyolefin wax, various surfactants such as fluorine-containing surfactants, Examples thereof include fluoropolymers such as a fluorinated ethylene polymer and an ethylene-tetrafluoroethylene polymer, and other surfactants having a releasing effect.

Moreover, the trouble of a pitch can be suppressed by mix | blending a pitch control agent with a surface side size press liquid, for example.
Examples of the pitch control agent include an organic pitch control agent and an inorganic pitch control agent.
As an organic pitch control agent, cationic compounds obtained by polymerization containing at least one or more cationic monomers, amine-epihalohydrin resins, polyethyleneimine, polyethyleneimine modified products, polyvinylamine, and other cationic compounds , Nonionic dispersants, anionic surfactants and the like.
Examples of the inorganic pitch control agent include polyaluminum compounds such as polyaluminum chloride, polyaluminum silicate sulfate, polyaluminum hydroxide, polyiron sulfate, zirconium carbonate, bentonite, and talc (fine powder).

Moreover, the surface side size press liquid may contain the water-system adhesive agent, for example. When the water-based adhesive is included, it is possible to prevent the surface pigment coating liquid provided in the subsequent step from sinking into the base paper, and the surface quality and printability are excellent.
Water-based adhesives include oxidized starch, phosphate esterified starch, hydroxyethyl etherified starch, dextrin, enzyme-modified starch, water-soluble starch and the like; styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer Latex such as latex, conjugated diene copolymer latex such as styrene-methyl methacrylate-butadiene copolymer latex, acrylic copolymer latex such as copolymer latex of acrylate ester and / or methacrylate ester; casein Proteins such as gelatin, soybean protein, various polyvinyl alcohols, various polyacrylamides, synthetic resin adhesives such as melamine resins, various cellulose derivatives such as carboxymethylcellulose, etc., one or two of these adhesives more than Selected and can be used.
Moreover, the surface side size press liquid may contain the pigment and the binder, for example. As the pigment, the same pigments as described in the explanation of the treatment liquid can be used. As the binder, the above-described aqueous adhesive is preferable. When a liquid containing a pigment and a binder is applied, the coating amount of the surface pigment coating liquid described later can be reduced.

The coating amount of the surface-side size press solution if it contains solids is preferably 0.1~7.5g / ^{m 2,} is preferably 0.3~6g / ^{m 2,} 0.5 More preferably, it is ˜4 g / m ² .
The treatment liquid and, if necessary, the surface-side size press liquid are applied by a size press and then dried by an after dryer.

"Surface pigment coating solution"
In the production method of the present invention, the surface pigment coating solution is applied to the surface of the surface layer by the coater part 4. The surface pigment coating liquid may be applied directly to the surface of the surface layer, or may be applied via a coating film by a surface side size press liquid applied to the surface of the surface layer. Before applying the surface pigment coating solution, the surface of the surface layer may be smoothed by a pre-calender. The surface pigment coating solution may be applied only once or may be applied a plurality of times. In particular, it is preferable to apply a surface pigment coating solution for the undercoat layer and a surface pigment coating solution for the topcoat layer to sequentially form the undercoat layer and the topcoat layer.
By applying the surface pigment coating solution, it is possible to improve the printability on the surface layer side or increase the whiteness.

The surface pigment coating liquid contains a pigment and a binder.
Examples of the pigment include one or more publicly known pigments used in the general coated paper manufacturing field such as kaolin, heavy calcium carbonate, light calcium carbonate, titanium dioxide, aluminum hydroxide, silica, satin white, and talc. The present invention can be used as appropriate within the above specified range without impairing the effects of the present invention. In particular, kaolin and calcium carbonate are preferable because they are excellent in printability.
Examples of the binder include starches such as oxidized starch, phosphate esterified starch, hydroxyethyl etherified starch, dextrin, enzyme-modified starch, and water-soluble starch; styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, Latexes such as conjugated diene copolymer latex such as styrene-methyl methacrylate-butadiene copolymer latex, and acrylic copolymer latex such as copolymer latex of acrylic acid ester and / or methacrylic acid ester; casein, gelatin , Proteins such as soy protein, various polyvinyl alcohols, various polyacrylamides, synthetic resin adhesives such as melamine resins; various cellulose derivatives such as carboxymethylcellulose, etc., one or more of these adhesives Selected and can be used.

The surface pigment coating liquid preferably contains 2 to 50 parts by mass, more preferably 5 to 25 parts by mass of the binder with respect to 100 parts by mass of the pigment.
If the ratio of a binder is more than a preferable lower limit, the strength of the coating layer of the surface pigment coating layer can be obtained. Moreover, if the ratio of a binder is below a preferable upper limit, ink drying property will be excellent and box-making suitability will also be excellent.
In addition, if necessary, a dispersant, a pH adjuster such as sodium hydroxide or ammonia water, an antifoaming agent, a fluorescent dye, a mold release agent, a water resistance agent, a fluidity improver, a slime control agent, an antiseptic agent In addition, one or more dyes, coloring pigments and the like may be included in the surface pigment coating solution.

The coating amount of the surface pigment coating solution is preferably from 5 to 50 g / ^{m 2} is preferably 8~45g / ^{m 2,} further preferably 10~35g / ^{m 2.}
When the surface pigment coating layer is applied a plurality of times, for example, in two steps, the first (undercoat layer) and second (overcoat layer) coating solutions may be the same or different.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to the following Example. In addition,% is the mass% unless there is particular notice. Further, the “parts” of the raw materials other than the medium are parts by mass not including the dispersion medium unless otherwise specified.

[Example 1]
"Preparation of surface pigment coating solution"
As a pigment, 60 parts of kaolin (trade name “Ultra White 90”, manufactured by BASF), 40 parts of light calcium carbonate (trade name “Brilliant 15”, manufactured by Shiraishi Kogyo Co., Ltd.), and urea phosphated starch as a binder (Part name “Neil Gum A-85”, manufactured by Abebe Co.), 16 parts of carboxylated styrene / butadiene copolymer latex (trade name “B-1525”, manufactured by Asahi Kasei Co., Ltd.) Was prepared.

"Preparation of treatment solution"
PVA (trade name “VF-10”, average polymerization degree 1000, saponification degree 99.4 mol%, manufactured by NIPPON VOC POVAL), surface paper strength enhancer (PAM, trade name “ST-5017”, Starlight) A treatment liquid 1 having a solid content concentration of 2% was prepared by blending PMC) at a mass ratio of 1: 1 (in terms of solid content).

"Manufacture of coated paperboard"
In the wire part of paper machine, Beitsubo 45 g / ^{m 2} of the surface layer pulps, Table lower pulp Beitsubo 55 g / ^{m 2,} the middle pulp Beitsubo 180 g / ^{m 2} (three layers), a pulp for backing layer Papermaking was performed at 60 g / m ² , respectively, and subjected to water pressing with a press part including a roll press and a shoe press to obtain a wet base paper of 340 g / m ² .
As the pulp for the surface layer, 80% pulp obtained by deinking fine waste paper (printed and collected from bookbinding companies) and 20% hardwood bleached kraft pulp were mixed, and a pulp having a whiteness of 85% was used. .
As the pulp for the lower layer, used deinked magazine waste paper with a whiteness of 70% was used.
As the middle layer pulp, used magazine paper with a whiteness of 40% was used.
As the pulp for the back layer, a pulp having a whiteness of 51%, which was blended at a ratio of 50% waste newspaper, 35% magazine waste, and 15% pulp from office paper shredder, was used.

After the wet base paper is dried to some extent by the pre-dryer part of the dryer part, the treatment liquid 1 is applied to one side of each of the back layer surface and the surface layer surface using a rod metering type size press. It apply | coated so that the coating amount might be 1 g / m < ² >. Then, the drying process was performed by the after-dryer part, and the smoothing process was performed by the calendar part.
Next, the surface pigment coating solution was applied with an on-machine rod blade coater so that the coating amount was 20 g / m ² , dried with a dryer, and subjected to on-machine calendering. A processed paperboard was obtained. The paper making speed was 460 m / min.

[Example 2]
In Example 1, a coated paperboard was obtained in the same manner as in Example 1, except that the treatment liquid 1 was coated only on the back surface with a rod metalling size press at a coating amount of 1 g / m ² .

[Comparative Example 1]
"Preparation of treatment solution"
Oxidized starch (trade name “Ace Y”, manufactured by Oji Corn Starch) and surface paper strength enhancer (PAM, product name “ST-5017”, manufactured by Seiko PMC) were blended at a mass ratio of 1: 1 (solid content conversion). A treatment liquid 2 having a solid content concentration of 2% was prepared.

  A coated paperboard of Comparative Example 1 was obtained in the same manner as in Example 2 except that the above treatment liquid 2 was used in place of the treatment liquid 1.

[Comparative Example 2]
In Example 1 “Manufacture of coated paperboard”, a wet base paper of 360 g / m ² was obtained, and then dried with a cylinder dryer (not coated with a size press), and an on-machine rod blade coater Then, the surface pigment-containing coating solution is applied to the surface of the surface layer so that the coating amount is 20 g / m ² , dried with a dryer, and then the processing solution 1 is applied to the surface of the back layer with a rod blade coater. Was 1 g / m ² , dried with a dryer, and smoothed with a calendar to obtain a coated paperboard.

[Example 3]
"Preparation of treatment solution"
PVA (trade name “VF-17”, average polymerization degree 1700, saponification degree 98-99 mol%, manufactured by Nihon Vinegar / Poval), surface paper strength enhancer (PAM, trade name “ST-5017”, Starlight) A treatment liquid 3 having a solid content concentration of 2% was prepared by blending PMC) at a mass ratio of 1: 1 (in terms of solid content).

  A coated paperboard of Example 3 was obtained in the same manner as in Example 1 except that the above-described treatment liquid 3 was used instead of the treatment liquid 1.

[Example 4]
"Preparation of treatment solution"
PVA (trade name “VP-18”, average polymerization degree 1800, saponification degree 86-90%, manufactured by Nihon Vinegar Poval), surface paper strength enhancer (PAM, trade name “ST-5017”, Starlight PMC The treatment liquid 4 having a solid content concentration of 2% was prepared by blending the product at a mass ratio of 1: 1 (in terms of solid content).

  A coated paperboard of Example 4 was obtained in the same manner as in Example 1 except that the above-mentioned treatment liquid 4 was used in place of the treatment liquid 1.

[Example 5]
A coated paperboard of Example 5 was obtained in the same manner as Example 1 except that a gate roll type size press was used instead of the rod metaling type size press.

[Example 6]
A coated paperboard of Example 6 was obtained in the same manner as in Example 1 except that a double roll size press, which was a pound-type size press, was used instead of the rod-metal ring type size press.

[Example 7]
A coated paperboard of Example 7 was obtained in the same manner as in Example 2 except that the coating amount of the treatment liquid 1 was 3.5 g / m ² per side.

[Example 8]
A coated paperboard of Example 8 was obtained in the same manner as in Example 2 except that the coating amount of the treatment liquid 1 was 4.5 g / m ² per side.

[Example 9]
A coated paperboard of Example 9 was obtained in the same manner as in Example 2 except that the coating amount of the treatment liquid 1 was 0.3 g / m ² per side.

[Example 10]
A coated paperboard of Example 10 was obtained in the same manner as in Example 7 except that a pulp with a whiteness of 48%, which was mixed with 50% waste newspaper and 50% magazine wastepaper, was used as the back layer pulp.

[Example 11]
The coated paperboard of Example 11 was obtained in the same manner as in Example 1 except that the surface paper strength enhancer (PAM) was not blended in “Preparation of treatment liquid” in Example 1.

[Example 12]
"Preparation of treatment solution"
PVA (trade name “VF-10”, average polymerization degree 1000, saponification degree 99.4 mol%, manufactured by NIPPON VOC POVAL), surface paper strength enhancer (PAM, trade name “ST-5017”, Starlight) PMC) is blended at a mass ratio of 1: 1 (in terms of solid content), and heavy calcium carbonate A (trade name: FMT-OP, manufactured by PMMA Tech, average particle size 0.6 μm) as a pigment is 100 parts by mass of PVA. A treatment liquid 5 having a solid content concentration of 20% was prepared by blending 40 parts by mass with respect to the above.

  Instead of the treatment liquid 1, a coated paperboard of Example 12 was obtained in the same manner as in Example 7 except that the treatment liquid 5 was used.

[Example 13]
"Preparation of surface pigment coating solution"
As a pigment, 75 parts of heavy calcium carbonate (trade name “FMT97”, manufactured by Phimatech), 25 parts of fine kaolin (trade name “Amazon”, manufactured by CADAM), and as a binder, a styrene-butadiene copolymer latex Surface pigment coating solution 2 was prepared using 12 parts, 0.2 part of surfactant and water.

"Manufacture of coated paperboard"
The coated paperboard of Example 13 was obtained in the same manner as in Example 1 except that the above surface pigment coating liquid 2 was applied by a curtain coating apparatus instead of the surface pigment coating liquid of Example 1 and dried. It was. The coating amount of the surface pigment coating liquid 2 was about 20 g / m ² in terms of mass after drying, and the coating speed was 330 m / min.

[Evaluation methods]
The following evaluation was performed about the coated paperboard of each Example and the comparative example. The results are shown in Table 1.

"White spot resistance"
The obtained coated paperboard was cut with a cutter to obtain a lithographic sample. Using a sheet-fed offset printing press, the above-described flat sample is printed continuously at 1050 sheets, and the amount of white spots in the solid print portion of the 1000th to 1050th print samples is evaluated according to the following criteria: did.
A: There is no white spot.
○: Slight white spots are recognized, but there is no practical problem.
(Triangle | delta): There exists a white spot and a problem arises depending on a use.
X: White spots are very conspicuous and have practical problems.

"Unevenness of back coating"
Black light was irradiated to the back surface of the obtained coated paperboard, and coating unevenness (fluorescence unevenness) on the back surface was visually evaluated.
A: Uniform and no coating unevenness.
○: Slight coating unevenness is observed, but there is no practical problem.
(Triangle | delta): There exists coating unevenness and a problem arises depending on a use.
X: Coating unevenness is very conspicuous and has practical problems.

"Surface coating surface quality"
The surface quality of the coated surface on the surface layer of the obtained coated paperboard was visually observed and evaluated according to the following criteria.
A: Excellent smoothness, gloss, and whiteness.
◯: One or two of the smoothness, glossiness, and whiteness are slightly inferior, but at a level that is not problematic in practice.
(Triangle | delta): One is inferior among smoothness, glossiness, and whiteness, and there exists a problem in practical use.
X: The surface is rough, and there is a problem in practical use.

"Glue permeability"
Prepare two sheets of the coated paperboard obtained, and apply vinyl acetate resin adhesive (product name: Lifebond AV650 (manufactured by Nichiei Kako Co., Ltd.) as glue on the back of one coated paperboard using a specified jig. After 6mm streaks are applied, the other coated paperboard is placed on top of each other so that the surface of the other coated paperboard is in contact with each other, and then crimped. Then, the joining state was visually determined, and from the results, the paste permeability was evaluated according to the following criteria.
(Double-circle): It has joined firmly within 2 minutes.
○: Strongly bonded within 5 minutes.
(Triangle | delta): Although it joins after 5 minutes, joining nonuniformity is recognized.
X: Almost no bonding after 5 minutes, and there is a problem in practical use.

"Processability"
After the obtained coated paperboard was punched with Thomson, the processed part was visually observed and evaluated according to the following criteria.
(Double-circle): There is no peeling of a coating layer and it is very favorable.
A: The coating layer is slightly peeled off, but at a level where there is no practical problem.
(Triangle | delta): The coating layer has peeled and is a practically problematic level.
X: The coating layer is largely peeled off and does not have processability.

As shown in Table 1, all of the coated paperboards of Examples had suppressed white spots, had excellent printability on the surface layer side, and had suitability for producing paper containers such as boxes.
On the other hand, the comparative example 1 which used the process liquid containing starch instead of a polyvinyl alcohol-type resin was inferior to white-out resistance.
In Comparative Example 2 in which the surface pigment-containing coating solution was applied to the surface layer side and then the treatment solution was applied to the back layer side, the surface quality of the surface coating layer was poor and the printability on the surface layer side was poor.

  DESCRIPTION OF SYMBOLS 1 ... Wire part, 2 ... Press part, 3 ... Dryer part, 4 ... Coater part, 16 ... Pre-dryer part, 18 ... Size press part, 20 ... After dryer part

Claims (8)

At least a wire part, a press part, a dryer part, and a coater part, using a paper machine having a size press in the middle of the dryer part,
In the wire part, at least a surface layer and a back layer are formed, and a base paper in which 70% by mass or more of all pulp components is waste paper pulp is formed,
In the size press in the dryer part, a treatment liquid containing a polyvinyl alcohol-based resin is applied to the surface of the back layer of the base paper,
A method for producing a coated paperboard, wherein a surface pigment coating solution containing a pigment and a binder is applied to the surface of the surface layer of the base paper at the coater part.   The manufacturing method of the coated paperboard of Claim 1 whose said size press is a size press of a film transfer system.   The manufacturing method of the coated paperboard of Claim 1 or 2 whose saponification degree of the said polyvinyl alcohol-type resin is 85 mol% or more. The coating amount of the coated paperboard according to any one of claims 1 to 3, wherein the coating amount of the treatment liquid applied to the surface of the back layer is 0.1 to 7.5 g / m ² in terms of dry mass. Production method.   The coated board according to any one of claims 1 to 4, wherein the back layer contains at least one kind of pulp selected from the group consisting of pulp derived from a shredded product and pulp derived from waste gypsum board. Method.   The coated paperboard according to claim 5, wherein at least one kind of pulp selected from the group consisting of pulp derived from the shredded processed product and pulp derived from waste gypsum board is 2 to 30% by mass of the pulp constituting the backing layer. Manufacturing method.   The method for producing a coated paperboard according to any one of claims 1 to 6, wherein the treatment liquid contains at least one pigment selected from the group consisting of kaolin, talc, calcium carbonate, and titanium dioxide.   The manufacturing method of the coated paperboard as described in any one of Claims 1-7 in which the said process liquid contains polyacrylamide type resin.

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