JP2010077555A - Coated liner and corrugated sheet using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated liner; to provide a corrugated sheet using the liner; especially to provide a coated liner which can be used as a liner for a decorated corrugated sheet excellent in the color-developing property of a water-based flexographic ink and is used for a corrugated box strong in impact and compression on transportation; and to provide the corrugated sheet using the same. <P>SOLUTION: The coated liner prepared by disposing a coating layer containing a pigment and an adhesive on one side of base paper composed of a plurality of embedded layers of at least three, wherein pulp used in either of the middle layer and back layer of the base paper is waste corrugated board and/or coniferous un-bleached kraft pulp; the coating layer contains reclaimed pigment obtained by calcining paper-making sludge and talc as pigments in the coating layer; the coated liner has a burst index of 2.0-5.0 kPa×m<SP>2</SP>/g. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coating liner and a corrugated cardboard sheet using the liner. In particular, it is a front liner for cardboard boxes that can be used as a liner for cosmetic cardboard sheets having excellent ink color development properties for flexographic printing and is resistant to impact and compression during transportation.

  In general, the liner is a cardboard made up of 2 to 9 layers. In the case of 2 layers, waste paper pulp that is not deinked is used for the back layer, and in the case of 3 layers or more, for the purpose of cost and resource saving. The Liners are processed into corrugated cardboard sheets in combination with core base paper and used in various packaging boxes, etc. In recent years, the function of corrugated cardboard boxes can be seen in the display of goods packed or displayed on the face of goods. In order to add the function as a multi-color printing, a lot of multi-color printing has been performed. For this reason, flexo printing, which has made remarkable technological progress compared to offset and gravure printing, is a recent wave of digitization in response to market issues such as the increase in variety of small lots, environmental and safety issues, and cost reduction. At the same time, it is attracting attention with its innovative and innovative technology. Furthermore, the print quality is comparable to other printing methods, and has a great advantage in terms of water-based and solvent-free. Flexo printing has already become mainstream in the packaging field in Europe and the United States. There are signs of dissemination. Under such circumstances, in addition to the usual craft colors, liners called cosmetic liners, which perform multi-colored printing with outstanding appearance, are blended with bleached pulp or upper white waste paper pulp on the surface, or coated with white pigment paint. It was manufactured by working and increasing the whiteness of the surface. Further, since measures for the surface layer alone are costly, pulp having a certain degree of whiteness may be used for the surface lower layer (layer immediately below the surface layer) to conceal the color of the intermediate layer. Those having such a high whiteness appearance give not only a blank paper surface but also an effect that the printed surface looks beautiful and vivid when printed on it. For this reason, corrugated cardboard boxes that have been color-printed using this type of liner have a high eye-catching effect, and in order to faithfully represent the contents, the contents are excellent. There is an excellent aspect that can appeal strongly. In recent years, it has become common to sell products packed in cardboard boxes at stores, mainly from mass retailers. From this point of view, a beautiful and vivid liner has been printed. It has been demanded. Even when a liner having a cosmetic property is formed as a corrugated cardboard box, it is a necessary function to protect the product from physical forces that are received in the distribution process such as storage and transportation.

  For this reason, a liner that provides a calm visual effect with a deep white paper appearance and printed appearance by adjusting the whiteness and hue of the liner surface to a predetermined range is disclosed (see Patent Document 1). Furthermore, as a liner excellent in white paper appearance and printed image sharpness, surface layer brightness is within a certain range (60-73), and ash content of the surface layer is disclosed to be 3% by weight or more and less than 9%. (See Patent Document 2). In addition, the coating layer containing pigments and binders as main components adjusts the whiteness, hue, and gloss to specific ranges, giving a calm visual effect on white paper, making the printed characters easy to read, and color A cosmetic liner is disclosed which has a good ink colorability when printed and a clear printing surface with a good printing gloss (see Patent Document 3). However, all of these disclosures only define the hue and brightness as a liner, and are not proposals that sufficiently satisfy the printability in flexographic printing. In addition, there is a method in which a large amount of white ink is printed on a general brown liner and then multicolor is printed to add cosmetics. In this case, the surface of the brown liner is made white, red or indigo. In order to improve the finish of multi-color inks and the like, it is necessary to print a large amount of expensive white ink, and this method is also a large economical burden. A liner having a coating layer containing a pigment and a binder on the surface layer of the liner and having an oil resistance (number of kits) of 12 or more is disclosed (see Patent Document 4). This liner has an oil resistance level that is too high to provide excellent flexo ink color development.

  Furthermore, as a method for obtaining a liner having excellent flexographic printability, a technique for improving the printing effect by applying a cationic resin to the liner surface is disclosed (see Patent Documents 5 and 6). However, the color development of the ink and the finished print surface are not fully satisfactory.

Further, (a) 20 to 70 parts by weight of calcined kaolin (b) structured kaolin as a pigment composition in the aqueous composition when an aqueous composition mainly composed of a pigment and an adhesive is applied to liner base paper And / or 15 to 77 parts by weight of delaminated kaolin, and (c) 3 to 20 parts by weight of plastic pigment, and the total of (a) + (b) + (c) is 70 parts by weight or more. A coating liner is disclosed (see Patent Document 7). However, the purpose is to obtain a coating liner that is suitable for gravure printing and excellent in white paper gloss and printing gloss. When a liner having a coating layer of this pigment composition is water-based flexographically printed, Only inferior density and inferior print finish can be obtained. Furthermore, in order to obtain a coating liner excellent in blank paper gloss and printing gloss without occurrence of flexo printing mottling, as a smoothness characteristic of the coating layer surface, a pressure type smoothness meter was used under a pressure condition of 5 kgf / cm ² . A coating liner having a smoothness of 3.0 μm or less when measured and a ratio of 0.3 to 0.8 with the smoothness measured at 20 kgf / cm ² has been proposed (see Patent Document 8). This proposal solves the problem by specifying appropriate smoothing because normal coating liners are low in smoothness and tend to cause mottling and to increase printing gloss. In this case, the ink absorption of the coating layer is inferior, and in particular, only a level at which the color development of the ink is insufficient is obtained. In gravure printing, flexographic printing, offset printing, and inkjet recording methods, high printing gloss is obtained, and inorganic pigments, binders, and surfaces are used on the surface layer for the purpose of preventing ink from peeling off due to friction after printing. It has been proposed to apply a coating agent containing three sizing agents (see Patent Document 9). Among these, since the surface sizing agent is blended in order to suppress the absorption of water and solvent, the ink absorption is suppressed and a high ink color developability cannot be obtained.

  Moreover, the proposal which prescribed | regulated both the specific bursting strength of the liner used for a corrugated cardboard sheet, and the pulp water retention in the layer of the thickness from the bonding surface to 1/3 of the whole thickness is made (refer patent document 10). ). However, this proposal is aimed at improving the initial adhesive strength when a corrugated core is laminated with a corrugated core, and a coating liner having a pigment coating layer on the liner surface. No mention is made of the resistance to impact and compression during transport. Further, a corrugated cardboard sheet and a corrugated cardboard box having improved vertical compression strength in a double-sided corrugated cardboard sheet are disclosed (Patent Document 11). This proposal is not described at all for a coating liner having a pigment coating layer on the liner surface.

  In recent years, it has been forced to reduce industrial waste from activities associated with production from the viewpoint of environmental conservation. Even in the paper industry, the treatment of paper sludge has become a problem. Papermaking sludge is a solid raw material that is mixed with wastewater without being used in fiber such as pulp, which is a papermaking material, organic matter mainly composed of starch and synthetic adhesive, and inorganic matter mainly composed of white pigment, Consists of lignin washed out in the pulping process, fine fibers, or waste paper-derived filler, printing ink adhering thereto, and excess sludge resulting from the biological wastewater treatment process. The main sources of paper sludge other than excess sludge generated in the biological wastewater treatment process are those that flow out through the wire during paper making, those that occur during the removal of contaminants in the waste paper treatment process, the deinking process, and the washing process. The waste water containing these solids is separated and recovered by a solid content separation device using precipitation or flotation, and then required. Correspondingly, after being subjected to biological treatment such as activated sludge treatment, it is discharged. The solid content separated and recovered by such treatment and the excess sludge generated by the final biological treatment of waste water become papermaking sludge.

  In the past, paper sludge generated from such paper mills was often landfilled as industrial waste, but recently, organic matter contained in sludge in incinerators such as fluidized bed furnaces and stoker furnaces. At the same time, the volume of papermaking sludge is reduced. However, since papermaking sludge contains inorganic substances, there is a problem that a large amount of residue (incinerated ash) remains after combustion. At present, some of the incineration ash is mixed with cement, used as an antioxidant for iron making, and a soil conditioner, but most of it is landfilled as industrial waste. In the future, as waste paper is reused, the amount of papermaking sludge becomes extremely large, and waste disposal becomes increasingly difficult. In addition, processing costs that are rising year by year are expected to press the profits of the pulp and paper industry. For this reason, in the paper industry that recycles used paper, the problem of papermaking sludge is extremely serious and its effective use is strongly demanded as part of its countermeasures. For this reason, if paper sludge incineration ash (inorganic matter) can be reused as papermaking fillers and coating pigments as papermaking materials, not only industrial waste will be reduced, but also the utilization rate of wastepaper will be improved. It can be linked and environmental problems can be solved. A number of methods for regenerating and reusing paper sludge for papermaking materials have been studied for such a social environment, and paper sludge was incinerated in an incinerator as a method for obtaining recycled pigment from the paper sludge. A method for improving the whiteness by burning unburned carbon by reburning incinerated ash (Patent Document 12), a method for forming papermaking sludge, incinerating with an internal combustion rotary kiln, etc., and pulverizing (Patent Document 13), After the first stage of incineration of organic compounds in paper sludge and the second stage of incineration of residual carbonaceous material under excessive oxygen supply, the heat treatment product is made into an aqueous suspension and carbon dioxide is blown in (Patent Document) 14) a method in which the paper sludge is dried, the organic component is completely burned in a combustion furnace, and coarsely pulverized or finely pulverized to form an aqueous dispersion and carbon dioxide gas is blown (Patent Document 15); Tsu multistage combustion method and the like have been proposed, such as grinding process during the combustion.

JP 2001-146697 A Japanese Patent Laid-Open No. 2007-100300 JP 2002-317395 A JP 2007-154360 A JP 2004-232158 A JP 2004-231901 A Japanese Patent Application Laid-Open No. 11-279989 JP 2000-314095 A Japanese Patent Laying-Open No. 2005-089931 JP 2003-247199 A JP 2007-253490 A JP-A-11-310732 JP 2002-167523 A JP-A-10-29818 JP 2002-356629 A

  According to the present invention, a regenerated pigment produced by effectively utilizing papermaking sludge disposed as industrial waste can be used as a liner for a cosmetic corrugated cardboard sheet having excellent color developability of water-based flexographic ink. An object of the present invention is to provide a coating liner for corrugated cardboard boxes that is resistant to impact and compression during transportation, and a corrugated cardboard sheet using the same.

The present invention provides a coating liner in which a coating layer containing a pigment and an adhesive is provided on one side of a base paper composed of at least three layers, and at least one of the middle layer and the back layer of the base paper. The pulp used in the layer is waste corrugated paper and / or unbleached kraft pulp, and contains, as a pigment in the coating layer, a regenerated pigment and talc obtained by burning papermaking sludge, The coating liner is characterized in that the specific bursting strength of the coating liner is 2.0 to 5.0 kPa · m ² / g.
The coating liner preferably has a specific compressive force of 115 N to 300 N · m ² / g.
It is preferable that the content of the regenerated pigment obtained by burning the papermaking sludge in the coating layer is 30 to 95 parts by mass per 100 parts by mass of the pigment.
The content of talc in the coating layer is preferably 5 to 50 parts by mass with respect to 100 parts by mass of the pigment.
A corrugated cardboard sheet using the coating liner is preferred.

  According to the present invention, a recycled pigment produced by effectively utilizing papermaking sludge disposed as industrial waste according to the present invention is used, and according to the present invention, the ink coloring property in flexographic printing is excellent and the printing uniformity is excellent. It has become possible to provide a liner and a corrugated sheet for corrugated cardboard boxes that are good and resistant to impact and compression during transportation.

  In general, flexographic printing is performed using a water-type ink, so that the ink penetration varies depending on the degree of water absorption of the printed surface. For this reason, the color developability, printing uniformity and halftone dot reproducibility in flexographic ink are greatly influenced by the degree of water absorption on the printed surface and the flexographic ink amount. When there is a regenerated pigment obtained by burning papermaking sludge in the coating layer formed on the liner surface, the flexographic ink absorbability is extremely improved, and the blended amount of regenerated pigment obtained by burning this papermaking sludge, and By adjusting the amount of other pigments blended, it is possible to obtain a liner with good ink color development suitable for various flexographic printing machines.

  The reason for improving the flexibility of flexographic printing when the recycled pigment obtained by burning papermaking sludge is contained in the coating layer is not necessarily clear, but the recycled pigment obtained by burning papermaking sludge has a collapsed crystal structure. Many of them have an amorphous structure, and are opaque, porous, and have excellent ink absorbability. Because of this, the porosity of the regenerated pigment allows ink to be incorporated into the pigment, and the solvent in the ink is evenly absorbed, resulting in uniformity of ink coloring and reproducibility of halftone dots. I think. However, the regenerated pigment is harder than a general pigment because it has undergone a baking process, and if contained in the coating layer, it increases the frictional resistance of the coating layer surface. Therefore, talc is required in the coating layer. The reason for this is that when foreign matter comes into contact with the liner surface and rubs during the production of corrugated cardboard sheets or boxes, the liner surface is likely to be contaminated with foreign matter if the frictional resistance of the liner surface is high. Is a flat pigment and has the property of reducing frictional resistance when it is present in the coating layer, thereby reducing dirt due to foreign matter. In general, talc for papermaking is a flat pigment with excellent covering properties and excellent ink acceptability. The average particle size measured by sedigraph is 1-5 μm, and the chlorite content is 0-90. %. Among them, the use of talc having a chlorite content of 5 to 50% is more preferable because it balances the dispersibility of the pigment and the effect of reducing stains during processing. Further, the content of talc is preferably 5 to 50 parts by mass per 100 parts by mass of the pigment. More preferably, it is 15-40 mass parts by chlorite content rate. Here, the content of the regenerated pigment obtained by burning the papermaking sludge in the case of containing talc is preferably 30 to 95 parts by mass, and more preferably 60 to 90 parts by mass.

  The sludge which is the raw material of the regenerated pigment in the present invention is waste generated from sewage or industrial wastewater of an industrial plant or process. Since sewage and factory wastewater contain solids, they are discharged after being settled and separated in a clarifier or a coagulation sedimentation tank. At this time, the solid content contained in the wastewater as waste is sludge. Here, the sludge discharged from the paper mill is referred to as paper sludge.

  In order to reduce the hardness of inorganic particles used as recycled pigments from papermaking sludge, a slurry of ash particles and calcium hydroxide incinerated at a high temperature at which the hydrocarbon material in the sludge is oxidized is prepared, and the slurry is carbonated. As a method of producing a composite granular material in which calcium carbonate is precipitated on the surface of ash particles, and other methods, the incineration ash can be mixed and baked with an alkali metal compound to prevent the formation of a high-hardness compound. A method of producing an amorphous silica fine particle by treating a product with an acid can be applied. A regenerated pigment obtained by a method for producing a porous granule in which incinerated ash is included in silicic acid by immersing the incinerated ash in an alkaline solution containing silicic acid and neutralizing the incinerated ash with acid. Can be used.

  Therefore, an example of a preferable method for obtaining inorganic particles to be a regenerated pigment from papermaking sludge is shown below. FIG. 1 is a view showing a basic flow sheet of a method for producing inorganic particles which are preferably used as regenerated pigments in the present invention, and will be described according to the basic flow sheet.

[Sludge]
Sludge is a raw material for inorganic particles to be a regenerated pigment according to the present invention. Raw material paper sludge is a combination of processes such as agglomeration, precipitation, concentration, and dewatering as a sludge recovery process for wastewater discharged from various processes in the paper mill such as pulping, paper manufacturing, and used paper recycling. Thus, the solids (various types of papermaking sludge) collected from each wastewater can be used alone or mixed and used as raw material sludge as appropriate. Of these, sludge from the used paper recycling process is subjected to agglomeration and dehydration treatment on the deinking waste liquid separated and discharged from the used paper pulp by pressurized flotation (flotation or flotation) and / or washing in the used paper deinking process. It is recommended to collect the solids in the deinking wastewater as deinking sludge. Also, when recovering sludge from waste paper raw materials with low whiteness, it is better to sufficiently perform deinking treatment and flotation treatment in the waste paper recycling process and remove ink particles including carbon black as much as possible. If necessary, a plurality of sludge pressurization and / or washing steps may be added. In addition, the deinking sludge collected from the wastepaper deinking process is separated into high-quality wastepaper, newspaper wastepaper, magazine (coating paper) wastepaper, etc., and deinking sludge is prepared for each type of wastepaper. The deinked waste paper classified by waste paper type can be used alone or as a mixture and appropriately used as a raw material sludge.

The inorganic component (ash content) in the papermaking sludge is a main component in which kaolin (clay) and calcium carbonate derived from a papermaking filler and a pigment for coated paper account for about 80 to 95% by mass of the whole inorganic component, A small amount of talc, titanium dioxide, etc. are mixed. The ratio of kaolin, which is the main component of the inorganic component, and calcium carbonate varies somewhat depending on the type of waste paper to be treated, but is generally in the range of 20/80 to 80/20 in terms of the mass ratio of kaolin / calcium carbonate. . Further, the calcium in the inorganic component (ash) (CaO equivalent), aluminum _(Al 2 _{O 3} basis) and silicon each content ratio (calcium / aluminum / silicon) of the (SiO ₂ equivalent), 13-73 / 12 -40 / 15-47.

  In addition, the ratio of the organic component and the inorganic component in the papermaking sludge varies somewhat depending on the type of waste paper to be treated and the degree of the deinking process, but is generally an inorganic component / organic component mass ratio of 30/70 to 80/20. Range.

  Apart from sludge, RPF (Refused Paper & Plastic Fuel) mainly composed of low-grade waste paper that is difficult to reuse as a papermaking material and its associated plastic can also be used as a raw material.

[Dehydration process]
Examples of a method for recovering raw material sludge from wastewater of various processes as a solid content include methods such as filtration, centrifugal separation, pressure dehydration, and pressing, and a papermaking sludge having a required water content is obtained by combining the various methods. As a suitable filtration device, there is a filtration device called a rotary screen, and as a dehydration device, there are a pressure / squeeze dehydration device called a screw press and a centrifugal dehydration device called a decanter. A filtering device and a pressing device can be used alone or in appropriate combination.

  Since the solid content concentration in the sludge varies depending on the capacity of the dehydrator, it is usually 5 to 60% by mass. However, the solid content concentration exceeding 70% by mass can be achieved by the current dehydrator or concentrator capacity. difficult.

[Drying process]
The solid content concentration of the sludge used in the heat treatment step is not particularly limited, but from the viewpoint of reducing the energy cost during the heat treatment step and from the viewpoint of reducing the heat treatment apparatus, it is preferable to increase the solid content concentration of the sludge as much as possible. It should be 70% or more. However, although only the above-mentioned dehydration step varies depending on the capacity of the dehydrator, the solid content concentration is about 5 to 60% by mass, and therefore it is recommended to further increase the solid content concentration by drying treatment.

  In order to increase the solid content concentration of the sludge, it is preferable to provide a drying step for drying the sludge before the heat treatment step as shown in FIG. The dryer used in the drying process is not particularly limited, and a direct heating rotary kiln, an indirect heating rotary kiln, an air flow dryer, a fluidized bed dryer, an oscillating fluid dryer, a rotary / aeration rotary dryer (cyclone), or the like is used. be able to. Moreover, as a heat source of these dryers, it is possible to reduce energy cost by using the exhaust heat of the baking process mentioned later.

  The temperature of the drying process may be set to 600 ° C. or less in an apparatus for drying using hot air such as an air dryer or a rotary / aeration rotary dryer in order to prevent combustion and carbonization of sludge. It is preferably 250 ° C. or less. If this hot air temperature is too high, sludge will ignite, and if the firing conditions at that time are not appropriate, there is a concern that the readily combustible organic components will carbonize and become incombustible. Moreover, in order to improve the drying efficiency in the drying process, it is preferable to break up sludge finely, forcibly with a stirrer or mechanical roll, etc., and classify the sludge to about 300 to 2000 μm as necessary. And drying.

  The sludge used in the heat treatment step is not particularly limited as long as it has a size and shape that can come into contact with oxygen when the sludge is stacked in the heat treatment apparatus. However, if the sludge is made fine and the size is uniform, the sludge is laminated like a close packing, and oxygen does not enter into the lamination, so the burning of organic matter, especially carbon, becomes insufficient and the whiteness does not improve there is a possibility. If the sludge is too large, the carbon cannot be burned completely, and unburned carbon may remain in the center of the sludge lump. In view of the above, it is preferable to use sludge having a length or diameter in the range of 2 mm to 30 mm. As the shape, a columnar shape, a spherical shape, an ellipse, a triangle, other polygonal shapes, or those having irregularities can be used.

  In order to form sludge into the desired size and shape as described above, granulation can be performed. The method of granulating sludge is a method using a compression molding machine such as a briquette machine or a roller compactor, a method using a semi-dry granulator such as a disk pelleter, a rolling granulation method, a stirring granulation method, an extrusion molding. There are laws.

  Moreover, even if it does not granulate sludge using a granulation molding machine as mentioned above, it is also possible to adjust the size with a screw feeder or the like when putting hydrous sludge into the dryer or putting dried sludge into the heat treatment device. Is possible. It is also possible to adjust the size and shape with a sludge dryer. That is, it may be formed into a certain block size.

[Heat treatment process]
In the heat treatment step, the combustion efficiency is improved by performing in an excess air (oxygen) atmosphere, so that the heat treatment apparatus can be reduced in size and labor can be saved. The heat treatment temperature is controlled by the method described later so that the ink pigment such as carbon black in the sludge and the organic matter such as fiber and polymer can be stably burned.

  An example of a heat treatment apparatus used for such a heat treatment step is shown in FIG. FIG. 2 is a block diagram of a heat treatment apparatus using an indirect heating type rotary kiln used in a heat treatment step when producing a regenerated pigment according to the present invention.

  There are no particular limitations on the firing furnace that is the main part of the heat treatment process. Box furnaces such as tunnel kilns, roller hearth kilns, pusher kilns, shuttle kilns, vertical cylindrical furnaces, rotary horizontal cylindrical furnaces, and screw-type horizontal furnaces A cylindrical furnace or the like can be used. As a system for supplying sludge, there are a batch system and a continuous system, but a continuous system capable of treating a large amount is preferable. It is preferable to use a rotary horizontal cylindrical furnace that has good heat transfer to the sludge and allows sludge in the heating furnace to come out to the surface more uniformly, or a screw type horizontal cylindrical furnace that can flow. A rotary kiln, which is a rotary horizontal cylindrical furnace that is as simple as possible from the viewpoint of maintenance of equipment and has a low driving energy, is preferable. As the shape of the rotary kiln firing chamber, a cylindrical shape, a hexagonal shape, or the like can be used. As rotary kilns, Takasago Industry Co., Ltd., externally heated continuous rotary kiln, Kurimoto Iron Works Co., Ltd., continuous externally heated rotary kiln IRK, Noritake Engineering Co., Ltd., indirectly heated continuous rotary kiln RKC-SG, Iwasa Machinery An externally heated rotary kiln manufactured by Co., Ltd. can be used.

  In addition, by providing a lifter and a stirring member that can be driven to rotate in the kiln furnace, more sludge and oxygen are in uniform contact with each other, so that the organic matter is burned efficiently and the whiteness of the sludge burned product is improved. However, it is more preferable because the quality becomes uniform.

  In addition, the multi-cylinder kiln and the kiln firing chamber have a multi-partition partition structure, which increases the heat transfer area, reduces sludge stacking / deposition in the kiln furnace, and contacts sludge with oxygen. Since heat transfer to the sludge is improved, the whiteness of the sludge fired product is improved, and uniform quality can be obtained. In addition, by using a multi-partition partition structure in the firing chamber, it is possible to reduce sludge stacking / deposition as described above compared to conventional kilns. Can be scaled. The number of divisions in the firing chamber is not particularly limited, but is preferably 6 divisions or more, and more preferably 10 divisions or more.

  Therefore, a heat treatment apparatus using these firing furnaces that can be suitably used for a heat treatment apparatus used in a heat treatment process uses a horizontal or vertical cylinder, so a cylindrical heat treatment apparatus using a cylindrical heat treatment furnace and Called.

  As shown in FIG. 2, a continuous indirect heating type that is an example of a cylindrical heat treatment apparatus, in which sludge S that has been processed individually or in combination with dehydration, drying, and granulation is sent from a drying apparatus that is not shown. The rotary kiln 1 is introduced into a supply hopper 2 serving as a sludge supply port installed at one end of the rotary kiln 1 in the cylinder axis direction, and supplied to the firing chamber 9 in the rotary kiln 1 via a screw feeder 10. As the sludge S passes through the firing chamber 9 of the rotary kiln 1, the organic components in the sludge S are combusted. The sludge S after combustion is taken out of the furnace through the sludge discharge port 8 installed at the end opposite to the sludge supply port in the cylinder axis direction, and sent to the next step.

  An exhaust fan 4 as an exhaust means is installed in the vicinity of the supply hopper 2. This exhaust fan forcibly exhausts the air in the rotary kiln 1, and the air installed in the vicinity of the sludge discharge port 8 into the rotary kiln 1. Air is sucked into the rotary kiln 1 from the supply port 3 as indicated by a dashed arrow A. In this way, the air flow indicated by the broken-line arrow A always occurs from the air supply port 3 toward the exhaust fan 4. This air flow becomes an unburned matter conveying air flow A described later. The air amount is controlled by controlling the exhaust amount of the exhaust fan 4. This amount of air is preferably controlled to be excessively sucked so that the inside of the furnace is in an excess (rich) oxygen atmosphere.

  Heat for heating the inside of the rotary kiln 1 is mainly supplied from the indirect heating means 5. The inside of the baking chamber 9 is indirectly heated by this heat. Heat is also generated by burning combustible components in the sludge in the firing chamber 9 of the rotary kiln 1, but the heat supplied from the indirect heating means 5 is much larger than this heat. By controlling the indirect heating means 5, the temperature in the rotary kiln 1 is kept uniform. The indirect heating means 5 can be electrically heated, but heating with a combustion gas of kerosene or heavy oil or heating with a gas burner is economically preferable. Combustion exhaust gas discharged from existing incineration facilities can be used, and steam or the like can also be used. In the example shown in FIG. 2, the combustion exhaust gas is supplied as the indirect heating means 5 by the circulation blower 7.

  The organic components in the sludge are basically combusted in the firing chamber 9 of the rotary kiln 1, but a part of the unburned matter is put on the air flow A and taken out from the rotary kiln 1. Since the air flow forcedly exhausted through the exhaust fan 4 is hot air, it is preferable to use the hot air circulation fan 6 to be sent to a sludge dryer (not shown) and reused as heat energy.

  As described above, the heat treatment step is performed by an indirect heating method capable of uniform temperature control in an excess air (oxygen) atmosphere. The indirect heating method is one method for heating the firing chamber (inside the furnace) 9. In the indirect heating type combustion furnace, the hot air generated by the combustion gas or the combustion gas and sludge are not in direct contact with each other. This is called because a partition is provided. As another heating method, there is a direct heating method in which a flame, combustion gas, or hot air is blown from one end of a cylinder. Since the direct heating type firing furnace is a method of heating from one end of the firing chamber (inside the furnace), the temperature differs greatly between the heating side and the opposite side, and the temperature of the entire firing chamber (inside the furnace) is accurately set. I can't control it. In contrast, the indirect heating method is not a method in which combustion gas or hot air is blown from one end of the cylinder as in the direct heating method, but a method in which the entire firing chamber (inside the furnace) is heated. Uniform temperature control is facilitated. Uniform temperature control is important for the following reasons.

  In the sludge, there are ink components such as carbon black, organic substances such as fibers and polymers, and inorganic particles such as calcium carbonate, kaolin, and talc. In order to improve the whiteness of the sludge fired product, it is necessary to remove carbon black which is a black ink component. In order to completely burn a single carbon black, at least a combustion treatment time of 60 minutes at 600 ° C. and 20 minutes at 850 ° C. is required in an excess air atmosphere. Therefore, it is preferable to increase the heat treatment temperature as much as possible. However, if the temperature is too high, the inorganic particles in the sludge undergo a sintering change, the sludge fired product becomes hard, and it tends to exhibit properties that are undesirable as a papermaking material.

  The hardening of the inorganic particles by the high-temperature heat treatment is caused by a thermal alteration phenomenon of inorganic calcium carbonate and kaolin (clay), which are mainly contained in sludge, as described below. That is, calcium carbonate begins to be decarboxylated from the vicinity of over 600 ° C., and at least part of it begins to be decomposed into calcium oxide, and completely decomposes into calcium oxide at 900 ° C. Talc does not change its crystal structure up to 900 ° C. Titanium dioxide is stable even at 1000 ° C. and does not change at all. Kaolin is crystal water desorbed from around 400 ° C. and exists as amorphous metakaolin up to 500 to 850 ° C. This amorphous metakaolin is called calcined kaolin, and is an inorganic particle that is bulky, has good opacity, and is excellent in smoothness. When the temperature exceeds 900 ° C., γ-alumina and mullite are generated. Since these γ-alumina and mullite are very hard, wire wear and coating blade wear are deteriorated, which is not preferable as a papermaking material. In addition, if there is calcium oxide decomposed from amorphous metakaolin and the above-mentioned calcium carbonate in a region slightly exceeding 850 ° C., hard and unsuitable galenite is generated by a chemical reaction.

  Therefore, it is preferable that the sludge temperature in the heat treatment step does not exceed 850 ° C. at which a hard fired product is not generated. Further, when the maximum temperature is less than 600 ° C., it takes a very long processing time to improve the whiteness, which not only increases the energy cost but also increases the heat treatment apparatus, which is not preferable in practice. Accordingly, a preferable sludge temperature is preferably 600 ° C. or higher and 850 ° C. or lower, and more preferably 600 ° C. or higher and 800 ° C. or lower.

  Further, in the heat treatment step, the sludge temperature may be increased stepwise to a temperature not exceeding 850 ° C.

Eventually, if it is going to prevent the sludge fired product from becoming hard in this way, the sludge temperature at the time of firing will be set lower, and it is difficult to completely burn the organic content in the sludge S, There is a risk that some unburned matter typified by carbon black remains. In addition, the temperature shown here is a sludge temperature when baking is performed in the baking chamber 9, and is strictly different from the atmospheric temperature in the heat treatment apparatus. Although the atmospheric temperature in the heat treatment apparatus depends on the temperature of the supplied air, it is usually lower than the sludge temperature.

  In the heat treatment step, the reason why the heat treatment apparatus is heat-treated in an excess air atmosphere, that is, in an oxygen-rich atmosphere is to efficiently burn organic substances contained in the sludge. The excess (rich) oxygen atmosphere here refers to supplying sufficient air (oxygen) necessary for combustion to the organic matter to be burned so that the residual oxygen concentration in the combustion exhaust gas is 5% or more. In this state, organic matter can be completely burned. It is also possible to adjust the sludge temperature according to the amount of air to be exhausted and the temperature of the air to be sucked.

  The amount of air sucked into the heat treatment apparatus is preferably equal to or greater than the theoretical oxygen amount necessary for burning organic components. However, since the combustion gas generated by burning the organic component is larger than the air amount corresponding to the theoretical oxygen amount, it is necessary to exhaust at least the generated combustion gas to make excess (rich) oxygenation. . Therefore, the amount of air to be sucked is controlled by adjusting the exhaust amount of the exhaust fan. The displacement is preferably 1.1 times the theoretical air amount, more preferably 1.5 times or more, and even more preferably 2 times or more. However, if the amount of intake air is too large, the sludge temperature is lowered, which is not preferable in terms of energy cost. Further, the inhaled air may contain more carbon dioxide than usual. Note that when the oxygen amount in the heat treatment apparatus is less than the theoretical oxygen amount and becomes deficient, it becomes in an oxygen-poor state and the sludge is carbonized, so that unburned carbon remains in the sludge. In order to remove this unburned carbon, it is necessary to increase the heat treatment temperature or to treat for a long time. Eventually, it is difficult to obtain a fired sludge product as a raw material for the regenerated pigment used in the present invention. Therefore, it is absolutely necessary to avoid making the inside of the furnace poorly oxygenated.

  Although the whiteness of the sludge fired product is increased by high-temperature treatment in order to burn the sludge S more completely in an excess (rich) oxygen atmosphere, as described above, a hard fired product is easily generated.

  As shown in FIG. 2, when the air supply port 3 is installed in the vicinity of the sludge discharge port 8 and the exhaust fan 4 for discharging the unburned matter conveying air flow A is installed in the vicinity of the sludge supply port 2, heat treatment is performed. An unburned matter conveying air flow A can be generated in a direction opposite to the direction B in which the sludge S travels in the apparatus.

  The method of generating the unburned matter conveying air flow A in the direction opposite to the direction B in which the sludge S travels is called a countercurrent method. In this counterflow method, the unburned matter conveying air flow flows in the opposite direction to that sent to the sludge discharge port 8 side of the sludge fired product, so that the unburned product can be efficiently removed from the sludge fired product. The whiteness of the fired product can be improved, which is more preferable. In particular, the unburned matter generated during the combustion in the first stage of the heat treatment process is difficult to be completely burnt until later, and can be effectively removed by this counter-flowing unburned matter carrying air flow.

  Therefore, in order to increase the whiteness, the sludge temperature is set higher, and the unburned product of the sludge is completely burned to 100%. By removing the product from the burned sludge, inorganic particles having high whiteness and not containing a high-hardness composite can be obtained. The above-mentioned unburned substances are unburned organic substances, and most are unburned carbon particles, in other words, carbide particles. That is, it is a carbon black-like substance, and the carbon black is in the form of a fine powder having a size of 10 to 500 nm and a specific gravity of 1.8 to 1.9. In order to remove the unburned matter in the form of fine powder, the air in the furnace is exhausted by the exhaust fan 4 to generate an unburned matter transfer air flow A in the heat treatment apparatus and put it on the transfer air flow A. The unburned material is taken out. In this way, it is very preferable to forcibly exhaust the unburned-substance conveying air flow using an exhaust fan or the like. More preferably, air is forcibly introduced in addition to such forced exhaust.

  The flow rate of the unburned product air flow by forced exhaust or the like is not particularly limited as long as it can remove the fine powdery unburned product, but when the flow rate is slow, the air flow flows to the supply hopper 2 side. Therefore, there is a concern that unburned matter cannot be removed well and is mixed in the sludge fired product, resulting in a decrease in whiteness. The flow rate of the unburned matter transporting air flow for transporting unburned matter containing carbon black having the above properties is preferably 0.4 m / min or more, more preferably 0.8 to 1.5 m / min or more, and particularly Preferably it is 1.5 m / min or more. However, if the flow rate of the air flow is too high, there is a greater possibility that the fired sludge will be mixed with the exhaust fan 4 side and the thermal efficiency will be reduced. The flow rate of the air flow was theoretically determined from the values of the exhaust fan, the air temperature, and the like, and the temperature in the heat treatment apparatus.

  On the other hand, FIG. 3 shows an example of an air inflow method opposite to the counter current method as another method. FIG. 3 is a configuration diagram of another example of a heat treatment apparatus using an indirect heating type rotary kiln. 3, the members denoted by the same reference numerals as those in FIG. 2 are the same as those described in FIG. In the heat treatment apparatus of FIG. 3, the exhaust fan 4 is installed in the vicinity of the sludge discharge port 8, and therefore, the unburnt substance conveying air flow A (or A ′) and the sludge traveling direction B are the same direction. Such a method is called a parallel flow method. In this co-current method, since the discharge port for separating and extracting the sludge fired product and the unburned product is in the same direction, there is a concern that the unburned product is likely to be mixed into the sludge fired product. Further, in the parallel flow method, as described above, even if the flow rate of the air flow for conveying unburned material is adjusted, the unburned material is likely to be mixed into the sludge fired product, so the counter current method is more preferable.

  In addition, when the sludge combustion temperature in this heat treatment device becomes high, the air flow is increased by a certain amount, thereby discharging excess sludge combustion heat to the outside of the heat treatment device by the air flow, that is, the rotary kiln. By discharging the high-temperature combustion exhaust gas in one firing chamber 9 to the outside of the rotary kiln 1 by the exhaust fan 4 on the sludge supply side, the combustion temperature of the sludge S in the firing chamber 9 can be lowered. Therefore, in the present heat treatment apparatus, contrary to the above, even if the temperature is high, the sludge combustion heat is discharged out of the heat treatment apparatus by increasing the air inflow amount above a certain amount, that is, the sludge from the main body cylinder portion of the rotary kiln. The temperature can be lowered by discharging heat to the outside of the supply side together with the air flow. That is, it is possible to perform control so as to avoid a rise above the set heat treatment temperature. Therefore, the unburned matter transport air flow A described above also serves as a sludge combustion heat exhaust air flow. Also in this point, the counterflow method has an exhaust port near the sludge supply port that discharges the airflow, so that the sludge combustion heat is heat treated without passing through the heat treatment device compared to the parallel flow method. It is more preferable because it can be discharged out of the apparatus and the sludge temperature can be easily controlled.

  In addition, when the sludge combustion temperature is high, the combustion can be suppressed and the temperature can be controlled by reducing the amount of air inflow, but it is necessary to make the heat treatment apparatus rich in oxygen and sufficiently burn the sludge. For this reason, it is not preferable to reduce the air flow rate more than necessary. On the other hand, even when the sludge combustion temperature is low, a large amount of air can be introduced to increase the temperature. That is, the combustion temperature can be adjusted by the air inflow amount.

  Such a difference in characteristics between the counter-flow method and the parallel-flow type air inflow method tends to be noticeable in a rotary horizontal cylindrical furnace and a screw-type horizontal cylindrical furnace. On the other hand, in a vertical cylindrical furnace, it is difficult to make a difference because it is necessary to flow air in order to improve the contact between air and sludge, but the parallel flow method is slightly more effective than the countercurrent method. is there.

  Unburned matter that has been separated and taken out on the air flow A for transporting unburned matter is removed by a bag filter provided after the hot air circulation fan 6 and / or captured by a combustion device (both not shown) together with exhaust gas. It is more preferable to remove or burn.

  The hot air discharged from the heat treatment apparatus is preferably reused as a heat source such as a heat treatment apparatus or a drier by the heat circulation fan 6, so that the energy cost can be reduced.

  The time during which the sludge is heated to a certain temperature (heat treatment time) is not particularly limited, but the time for the organic matter remaining in the firing chamber 9 to be completely burned without being blown off by the air flow A for conveying the unburned air flow is maintained. Since it is necessary to do, 1 hour or more is preferable. However, an unnecessarily long heat treatment time not only increases the energy cost but also increases the heat treatment apparatus. Therefore, the heat treatment time during the heat treatment step is more preferably 1 to 5 hours. By suitably controlling the conditions such as the heat treatment time, sludge temperature, air flow rate, flow rate, etc., the decomposition rate of the calcium carbonate component in the sludge is preferably 50% or more, more preferably 60% or more, and even more preferably 70%. That's it.

[Firing product suspension process]
As illustrated in FIG. 1, the fired product after the heat treatment step may include a suspension process after the heat treatment step in which the fired product is mixed with water and stirred to form a suspension of the fired product. The purpose of the suspension process is to dissolve calcium contained in the sludge calcined product as calcium ions in water, and there is no particular restriction on the suspension temperature of the calcined product, but it is necessary to maintain the temperature when the treatment temperature is high Since it is economically unfavorable, it is usually preferable to carry out at 20 to 80 ° C.

  The solid content concentration of the baked product suspension can be adjusted to the range of 5 to 20% by mass to efficiently carry out the subsequent carbonation treatment, and the viscosity of the suspension is kept low so that the fluid agitation and liquid feeding can be maintained. In order to maintain good properties. When the solid content concentration of the fired product suspension is less than 5% by mass, the productivity is inferior because it is not preferable. This is not preferable because the stirring power increases and the operability is inferior.

In addition to the calcined sludge of the present invention, calcium oxide (CaO: quick lime) or calcium hydroxide [Ca (OH) ₂ : slaked lime] is separately added to the calcined product suspension as necessary. In this case, calcium oxide and calcium hydroxide can be mixed with calcium hydroxide [Ca (OH), which is a form after dehydration. ₂ : Slaked lime] can be added up to 100 parts by mass (sludge: calcium hydroxide = 50: 50) with respect to 100 parts by mass of the sludge burned product. Although calcium hydroxide can be added in excess of 100 parts by mass, it is not preferable because the blending ratio of the sludge fired product in the slaked suspension is reduced and sludge utilization does not proceed.

[Carbonation process]
In the sludge containing calcium carbonate, calcium carbonate (CaCO ₃ ) is decomposed in a heat treatment step of 600 ° C. or higher. If the calcined ash containing decomposed calcium carbonate is made into an aqueous suspension, it becomes highly alkaline, and there are problems such as an increase in slurry viscosity and poor dispersion. Therefore, it is used as it is as a paper filler and coating pigment. Is difficult. When the sludge combustion efficiency is improved as in the heat treatment step described above, the decomposition of calcium carbonate is promoted. That is, the whiteness of the calcined ash after the heat treatment step and the decomposition rate of calcium carbonate are in a proportional relationship, and in order to obtain a desired white calcined ash, the calcium carbonate in the sludge is decomposed to exceed 50%. In order to obtain high white baked ash, 60% or more is decomposed, and in order to obtain high whiteness baked ash, 70% or more is decomposed. For this reason, it is preferable to neutralize the alkali component by some method such as carbonation treatment or aluminum sulfate mixing treatment on the heat-treated sludge calcined ash.

By performing the carbonation step after the calcination product suspension step, the calcium ions in the calcination product suspension are regenerated and converted to calcium carbonate (CaCO ₃ ), and the pH of the regenerated inorganic particle slurry can be lowered. In addition, by making the pH of the regenerated inorganic particle slurry 11 or less, preferably 10 or less, it is possible to suppress an increase in slurry viscosity and to prevent poor pigment dispersion. The regenerated inorganic particles mainly include calcium carbonate particles newly precipitated by carbonation treatment and amorphous component particles in which kaolin is modified by heat treatment. This amorphous component shows properties similar to those of calcined kaolin. Therefore, this amorphous component can be called a calcined kaolin-like component.

  In addition, when calcium carbonate is not contained in the sludge, calcium carbonate is not decomposed and calcium ions are not liberated, so that the calcined ash can be dispersed at a high concentration, and the calcined product suspension step after the heat treatment step and Even if a carbonation step is not used, it can be reused as it is as a papermaking material.

  A carbonation process can be performed by the method similar to a normal light calcium carbonate manufacturing process. That is, carbon dioxide gas or carbon dioxide-containing gas is blown into the fired product suspension. The gas used for carbonation is industrially preferably a carbon dioxide-containing gas, and the concentration of carbon dioxide in this case is not particularly limited, but is preferably 5 to 40% by volume, more preferably 10 to 35% by volume. The carbon dioxide containing gas is used. Examples of the carbon dioxide-containing gas include sludge calcined exhaust gas, limestone calcined exhaust gas, lime calcined exhaust gas, waste incineration exhaust gas, power generation boiler exhaust gas, exhaust gas discharged from a causticized calcium carbonate calcined kiln used in a pulp manufacturing process, etc. May be used after dust removal by an appropriate means.

  The carbon dioxide gas or the carbon dioxide-containing gas is blown into the fired product suspension so as to have a rate of 0.5 to 15 L / min per 1 kg of the fired product as carbon dioxide gas. If the amount of carbon dioxide introduced is less than 0.5 L / min, the productivity is inferior, and an amount exceeding 15 L / min can be adopted, but it is commensurate with the power load necessary to increase the amount of use. The effect cannot be expected. The reaction start temperature for carbonation is preferably 30 to 80 ° C, more preferably 40 to 70 ° C. The shape of the regenerated calcium carbonate component contained in the regenerated inorganic particles can be rice granule, spindle shape, colloidal shape, needle shape, cubic shape, plate shape, etc. There is no particular limitation on the shape, and carbonation In order to obtain crystals having a desired shape during the process, seed crystals may be added.

  In addition, the inorganic particles after the carbonation treatment are aggregated with fine calcium carbonate primary particles generated by the carbonation treatment to form secondary particles (aggregated particles), and have a particle size suitable for a papermaking filler. There is. In such a case, this suspension can be used as it is by blending it with a papermaking raw material such as pulp as a papermaking filler.

[Dehydration and dispersion process]
When the regenerated inorganic particle slurry (slurry after carbonation) is used as a coating pigment, a dehydration step of dehydrating the composition regenerated inorganic particle slurry after the carbonation step into a dehydrated composition, and the dehydration step It is preferable to include a dispersion step of adding water to the obtained dehydrated composition to form a slurry-like dispersion composition. The dehydration step can be performed by operations such as filtration, centrifugation, pressure dehydration, and pressing. As a suitable dehydrating apparatus, there is a press filtration apparatus called a filter press, and a dehydrated cake of a carbonized product can be obtained. The dispersion process may be any process as long as water is added to the dehydrated composition obtained by the dehydration process to form a slurry-like dispersion composition. It is preferable to add a dispersing agent in addition to moisture during the dispersing step, because it is possible to satisfactorily disperse the regenerated inorganic particles using sludge as a raw material, improving the quality as a papermaking material and facilitating handling. As the dispersing agent, for example, a general dispersing agent used in the manufacture of a papermaking material such as a synthetic polymer dispersing agent such as sodium polyacrylate can be used.

[Crushing process]
The pulverization process may be provided after the dispersion process. By carrying out the pulverization treatment, the particle diameter of the regenerated inorganic particles can be reduced, and the smoothness is improved, which is preferable. As a pulverizer used in the pulverization step, a wet pulverizer such as a sand mill, a wet ball mill, a vibration mill, a stirring tank mill, a flow tube mill, or a coball mill can be used. Moreover, you may grind | pulverize, blowing in a carbon dioxide.

  The size (particle diameter) of the inorganic particles to be the regenerated pigment is particularly preferably 0.3 to 5 μm when used as a coating pigment as an average particle diameter by laser diffraction particle size distribution measurement.

  Incidentally, when fine particles with an average particle size of regenerated inorganic particles of less than 0.3 μm are effective for improving opacity, whiteness, smoothness, etc., they are used as coating pigments. In order to develop a sufficient coating layer strength, it is not preferable because a considerable amount of adhesive is required. When used as a coating pigment, the smoothness and gloss of the coated paper product are lowered, and as a result, the printability is also lowered.

  It is preferable to provide a dispersion step and a pulverization step after the dehydration step in order to make the inorganic particles to be the regenerated pigment have the desired particle size, but the average particle size of the regenerated inorganic particles after the dispersion treatment is the above-mentioned particle size. If it falls within the range, the dispersion of inorganic particles after the dispersion treatment may naturally be used as the coating pigment as it is without carrying out the pulverization step.

Although a heat treatment step is necessary, a drying step, a granulation step, a suspension step, a carbonation step, a dehydration / dispersion step, and a pulverization step can be appropriately selected and combined. Devices that perform these processes are combined to form one plant.
The inorganic particles obtained as described above can be used as a regenerated pigment.

In the present invention, the coating layer containing the regenerated pigment and talc may be a single layer or multiple layers, but the total coating amount is preferably ² to ²⁰ g / m ² . When the coating amount is within this range, it is possible to obtain a liner which is excellent in economic efficiency and excellent in water-based flexo ink color development. A more preferable coating amount is 3 to 10 g / m ² . Since the main component of the inorganic component in the paper sludge is kaolin / calcium carbonate in the range of 20/80 to 80/20, the recycled inorganic material after the step of bringing carbon dioxide into contact with the inorganic material after the baking treatment is heated by the baking treatment. The ratio of the modified kaolin component and calcium carbonate component is in the range of approximately 20/80 to 80/20. If there is 10% by mass or more of the kaolin component thermally modified by the baking treatment, that is, the calcined kaolin-like component, the ink is taken into the pigment and the solvent in the ink is uniformly absorbed due to the porosity of the calcined kaolin-like component. The color development and uniformity of the ink can be obtained, and the reproducibility of the halftone dot due to the improved adhesion is considered to be more preferable. If it is less than 10% by mass, it is easy to add expensive calcined kaolin, which is economically disadvantageous.

  Recycled pigments obtained by burning papermaking sludge with paint pigments to be applied to the liner base paper surface, and pigments other than talc include pigments commonly used in the papermaking field, such as clay, structured kaolin, engineered One kind or two or more kinds of kaolin, aluminum hydroxide, calcined kaolin, titanium dioxide, light calcium carbonate, heavy calcium carbonate, barium sulfate, zinc oxide, satin white, calcium sulfate and the like can be used. In addition, the regenerated pigment obtained by burning papermaking sludge and the pigment excluding talc can be used within a range that does not impair the desired effect of the present invention from the viewpoint of the absorbability of flexographic ink. In particular, calcined kaolin is a more preferred pigment for enhancing the flexo ink color developability, and the blending number when calcined kaolin is blended is preferably 65 parts by mass or less. Note that organic pigments such as plastic pigments are not preferable because of poor ink absorbability.

Furthermore, it is preferable to add a water retention agent to the coating material to be coated on the liner base paper surface because the coating suitability is improved. As the water retention agent to be added, sodium salt of carboxymethyl cellulose, which is generally called CMC in the papermaking field, hydroxyethyl cellulose, polyvalent carboxylic acid acrylic copolymer called synthetic water retention agent, methacrylic acid and acrylic ester And the like. Among them, sodium salt of carboxymethyl cellulose is easy to apply uniformly on the coated surface, and particularly has a degree of etherification of 0.60 to 1.00 and a degree of polymerization of 600 to 1200.
Those in the range are preferable in terms of good handleability.

The adhesive in the paint of the present invention is not particularly limited, and a known adhesive used in the general coated paper manufacturing field is appropriately used. For example, styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, conjugated diene copolymer latex such as styrene-methyl methacrylate-butadiene copolymer latex, acrylic ester and / or methacrylate ester Acrylic polymer latex such as a polymer or copolymer latex, vinyl polymer latex such as ethylene-vinyl acetate polymer latex, or these various polymer latexes were modified with a functional group-containing monomer such as a carboxyl group. Examples include water-dispersible adhesives such as polymer or copolymer latex, synthetic resin adhesives such as polyvinyl alcohol and olefin-maleic anhydride resins, and starches such as oxidized starch, amphoteric starch, esterified starch, and dextrin. The One or more of these water-dispersible and / or water-soluble adhesives can be appropriately selected and used. It is preferable to use 10 to 50 parts by mass of the adhesive with respect to 100 parts by mass of the pigment. More preferably, it is 15-40 mass parts. Incidentally, if the content of the adhesive is less than 10 parts by mass, the strength of the coating layer cannot be maintained. If the amount exceeds 50 parts by mass, the ratio of the pigment in the coating layer becomes small, so that the ink color development in flexographic printing and / or the printing uniformity are inferior.

  Additives such as anti-slip agents and dyes may be used in combination in the paint used in the present invention as long as the effects of improving the ink coloring property and finishing the printing uniformity are not impaired.

When coating the paint of the present invention on the liner base paper, a coating device generally used for coated paper production can be used, for example, blade coater, air knife coater, roll coater, reverse roll coater, bar coater, curtain. On-machine or off-machine liners using coating equipment such as coaters, die slot coaters, gravure coaters, chaplex coaters, 2 roll size press coaters, gate roll size press coaters, film metallizing size press coaters, etc. The base paper is coated with a single layer or multiple layers. The solid content concentration of the pigment composition at the time of coating can be selected in the range of 10 to 75% by mass, but the coater to be applied should be applied so that the coating amount remains in the range of ² to 10 g / m ^2. It is preferable to adjust appropriately in consideration.

  In order to further improve the coating surface and printability, the coating liner coated in the present invention is a calender device such as a super calender using a cotton roll as an elastic roll and a soft nip using a synthetic resin roll as an elastic roll. The smoothing process can be performed. The soft nip calender can set the heat-resistant temperature on the surface of the synthetic resin roll higher than that of the cotton roll, so it can be processed at high temperatures, and compared with the super calender when the same smoothness is targeted. This is a preferred embodiment because the treatment linear pressure can be set low.

  As the pulp constituting the middle layer and the back layer of the base paper for a coated liner of the present invention, used corrugated paper and / or softwood unbleached kraft pulp (NUKP) is used, and the beating degree is preferably 250 to 500 ml. The reason why these pulps are selected is because the fiber length of the pulp is long, so that the fibers are entangled after paper making, and as a result, the required specific burst strength and good specific compression force can be obtained. .

  In addition, in the case of multi-layer paper making of the surface layer, 4 layers or more, the pulp constituting the surface layer is not particularly limited, for example, unbleached, bleached chemical pulp, mechanical pulp, non-wood pulp, which is wood pulp, Kent waste paper, magazine waste paper, flyer waste paper, newspaper waste paper, office waste paper, information paper waste paper, corrugated paper waste, waste paper pulp such as paper waste paper, etc. Are appropriately blended and used. However, since the surface layer is a layer in contact with the coating layer, it is preferable to use bleached pulp or deinked pulp. This is because if the whiteness of the surface layer is high, the whiteness becomes higher when the coating layer according to the present invention is provided, and a coating liner having excellent cosmetic properties can be obtained. In the case of four or more layers, it is preferable to use bleached pulp or deinked pulp because the lower surface layer is also a layer in contact with the liner surface layer and the surface whiteness is easily affected. Their beating degree is preferably 250 to 500 ml. As other pulp types, pulp obtained by deinking waste paper pulp such as waste magazine paper, flyer waste paper, newspaper waste paper, office waste paper, information paper waste paper, corrugated waste paper, paper waste paper, etc. is used.

By selecting the above pulp, the specific burst strength in the resulting coating liner is in the range of 2.0 to 5.0 kPa · m ² / g, formed into a cardboard box, and impact during product transportation. And strength against compression is maintained. Furthermore, if the specific compressive force in the lateral direction of the coating liner is in the range of 115 to 300 N · m ² / g, the strength against impact and compression during product transportation can be maintained as well as the specific burst strength. .

  Here, the internal chemicals used for the liner coated base paper can be used as necessary, for example, sizing agent such as sulfate band and rosin, paper strength enhancer such as polyamide and starch, drainage retention improver, polyamide Water resistant agents such as polyamine epichlorohydrin, dyes and the like are used. The exemplified pulp and internal chemicals can be used.

  Further, the whiteness of the liner base paper surface is applied to the present invention in the range of 40 to 80%. The higher the whiteness of the base paper, the higher the visual whiteness after coating, and the higher the contrast of the portions with and without flexographic printing, so the printed finish is improved. In order to increase the whiteness of the base paper, it is necessary to whiten the pulp used, which increases the economic burden. Considering the balance between printing finish and economy, the base paper whiteness is preferably in the range of 50 to 70%. In addition, it is desirable to add a sizing agent to the surface layer of the base paper to be coated in order to suppress the penetration of the paint.

  The flexographic ink for printing on the coating liner of the present invention is not particularly limited, and examples thereof include an alcohol type, a cosolvent type, an aqueous type, and a UV curable type. Among these flexographic inks, an aqueous type is also included. However, it is also excellent in safety, workability, and economical efficiency, and is an embodiment in which the effects of the present invention are most prominent.

  Also, the flexographic printing press used is classified into three types, stack type, line type, and central impression type, depending on the arrangement of printing units, but any type can be used.

  The coating liner obtained according to the present invention is used as a liner for corrugated cardboard sheets provided on at least one outermost surface. As a corrugated cardboard sheet, a single-sided cardboard sheet in which a liner is bonded only to one side of the core, a double-sided cardboard sheet in which a liner is bonded to both sides of the core, and a plurality of core / liner laminates provided in a plurality of stages Although there are corrugated cardboard sheets, the present invention is applicable to any corrugated cardboard sheet.

  There is no restriction | limiting in particular as a core of the corrugated member which comprises a corrugated cardboard sheet | seat with a liner, What is used for the general corrugated cardboard sheet | seat can be used. As raw material pulp, semi-chemical pulp (SCP), Chemi-ground pulp (CGP), corrugated waste paper pulp, magazine waste paper pulp, unbleached kraft pulp, kraft pulp, synthetic fiber, etc. can be used. It is preferable to use a lot of waste paper pulp such as corrugated waste paper pulp and magazine waste paper pulp. The core may be a laminated paper, and may further be a laminated paper having a synthetic resin adhesive layer between layers.

  The corrugated board sheet of the present invention can be produced by applying a conventionally known corrugated board sheet production method as it is, for example, through a corrugator treatment in which a core and a liner are bonded via an adhesive substance. Adhesive materials include starch paste and synthetic resins (polyethylene, polypropylene, polyamide, polyester, ethylene-unsaturated carboxylic acid copolymer, styrene-butadiene copolymer, butadiene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer). Polymer, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyacrylate copolymer, styrene-acrylate copolymer, etc.).

  Specific bonding methods for corrugated cardboard sheets are as follows: (1) An adhesive layer is formed on the surface of the core or liner by extrusion lamination, synthetic resin emulsion application, etc., and then these are stacked, pressed and heated (2) A method in which a synthetic resin film is interposed between the core and the liner, and the pressure is applied and heated to bond, and (3) an emulsion or solution of the synthetic resin between the core and the liner. And a method of adhering them by pressurization and heating. In the method (2), a pre-molded synthetic resin film can be fed out and supplied between the core and the liner, or the synthetic resin film can be supplied between the core and the liner while being melt-extruded. You can also

  A single-sided cardboard sheet is manufactured by performing the corrugator process once, and a double-sided cardboard sheet or a multi-stage cardboard sheet is manufactured by repeatedly performing a plurality of times. The double-sided corrugated cardboard sheet is, for example, a single facer (SF) in which a core and a liner are bonded with a heat and pressure roll to form a single-sided cardboard sheet, and a liner is further provided on the core side of the single-sided cardboard sheet obtained by SF. It can be manufactured using a corrugator having a double facer (DF) that travels on a hot plate while being stacked and pressed. The heating and pressing conditions are not particularly limited. For example, the heating temperature of SF is 150 to 200 ° C., the linear pressure is 20 to 40 kN / m, the pressing time is 0.01 to 0.20 seconds, and the heating temperature of DF is 150 to 200 ° C. A linear pressure of 0.1 to 1.0 kN / m, a pressurization time of 2 to 7 seconds, and the like are preferable.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these ranges. In the examples, “parts” and “%” indicate parts by mass and mass% unless otherwise specified.

Example 1
(Preparation of regenerated pigment)
[Sludge]
In the waste paper deinking process mainly used for magazine waste paper at a paper mill with waste paper processing equipment, waste water from waste paper pulp was supplied to a flotation machine and subjected to flotation treatment to obtain white water. A flocculant was added to the obtained white water to agglomerate the solid content in the waste liquid, and then sequentially passed through a rotary screen and a screw press to recover papermaking sludge (deinking sludge) having a solid content of about 50%. . The ash content in this papermaking sludge was 60%, and the composition was calcium carbonate 55%, kaolin 40%, and talc 5%.

[Heat treatment process]
This heat treatment step was performed by a heat treatment apparatus (countercurrent system) having the configuration shown in FIG. Specifically, a continuous external heating type rotary kiln 1 (IRK-02 manufactured by Kurimoto Iron Works, heated portion: Φ25 × 180 cm) was used as a heat treatment apparatus. Paper sludge S was supplied to rotary kiln 1 from supply hopper 2 which is a sludge supply port at a speed of 3.5 kg / h. The supplied papermaking sludge S is conveyed by a screw feeder 10 to a firing chamber (rotary cylinder) 9 in the rotary kiln 1 and is heat-treated, that is, fired while passing through the firing chamber (rotary cylinder) 9. As the indirect heating means 5, combustion gas from a combustion boiler (not shown) is supplied from the circulation blower 7 and used. At this time, the sludge temperature becomes 850 ° C. by controlling the air flow rate and indirect heating while exhausting the gas in the kiln from the exhaust fan 4 as an unburned matter conveying air flow A at 150 L / min (20 ° C. conversion). And heated for 140 minutes to prepare a fired product.

  The obtained sludge fired product was measured by X-ray diffraction to determine the decomposition rate of calcium carbonate. As a result, the calcium carbonate component was decomposed 100%. Further, the kaolin component was transformed into a 100% amorphous component, and talc was not decomposed at all.

[Firing product suspension process]
The obtained sludge fired product is mixed with 60 ° C. warm water in a suspension tank (dissolving tank) and stirred for 60 minutes while maintaining the suspension tank at 60 ° C. to prepare a 12% fired product suspension. did.

[Carbonation process]
In a carbonation reaction tank, 10 kg of a 12% calcined product suspension at a temperature of 60 ° C. was introduced, and 25% by volume of carbon dioxide-containing gas was blown at 20 L / min while maintaining the reaction tank at 60 ° C., and stirring was performed for 60 minutes. Regenerated inorganic particles were obtained. When the obtained regenerated inorganic particles were measured by X-ray diffraction, the calcium carbonate decomposed by the firing treatment was regenerated to calcium carbonate.

[Dehydration and dispersion process]
The composition after completion of the carbonation step was dehydrated with a filter press to obtain a dehydrated composition having a solid content of about 50%, and then the dehydrated composition was dispersed in water with a coreless mixer so that the solid content was 48%. At the time of dispersion, a polyacrylic acid-based dispersant (trade name: Aron T-50, manufactured by Toa Gosei Co., Ltd.) is added to water in an amount of 1.0 part relative to the solid content of the composition (the dehydrated composition). And a slurry was prepared.

[Crushing process]
The slurry composition after the dispersion step was pulverized using a sand grinder as a wet pulverizer to obtain a regenerated pigment as inorganic particles having an average particle size of 1.6 μm.

(Manufacture of coating liner)
As surface pulp, NBKP 15%, Kent waste paper 85%, USP 35g / m ² , Kent waste paper 100% Kent waste 35G / m ² , NMPP 60%, magazine waste paper 40 % And the weight of the paper is 120 g / m ² , and the back layer is 60% newspaper waste paper, 40% waste magazine paper is 90 g / m ² , and the paper is 280 g / m ² liner. I got the base paper. The surface layer contains a paper strength agent (trade name: Polystron P-1222, manufactured by Arakawa Chemical Industries) 1.3%, a sulfuric acid band 3%, a sizing agent (trade name: Size Pine SPN-815, Arakawa Chemical). 2.5%) was added. Further, 0.1% of a paper strength agent (trade name: Polystron P-1222, supra) was added to the front, lower, middle and back layers.

85 parts of the regenerated pigment obtained above, 15 parts of talc (trade name: Microtouch, manufactured by Nippon Mystron), 28 parts of adhesive (trade name: B-1535, manufactured by Asahi Kasei), synthetic water retention agent (product) Name: SN-924 (manufactured by San Nopco)) 0.4 parts (all in terms of solid content) was prepared to a concentration of 40%. The prepared paint was coated on the above 280 g / m ² liner base paper with a bar coater so that the dry mass was 6 g / m ² (solid content), dried, and then a calendar composed of an elastic roll and a metal roll. 2Nip was calendered to obtain a coated liner.

Example 2
Example 1 Example 1 except that 50 parts of the regenerated pigment obtained above, 25 parts of talc (trade name: Microtouch, supra), and 25 parts of heavy coal (trade name: FMT90, manufactured by PMMA Tech) were used in Example 1. In the same manner as in No. 1, a coated liner was obtained.

Example 3
In Example 1, a coated liner was obtained in the same manner as in Example 1 except that the middle-layer pulp was 60% waste newspaper, 40% magazine waste paper, and the back layer pulp was 100% corrugated waste paper.

Example 4
In Example 1, the back layer pulp is 100% corrugated cardboard, 20 parts of the regenerated pigment obtained above as a paint, 60 parts of talc (trade name: Microtouch, supra), calcined kaolin (trade name: Ansilex) 93, manufactured by BASF) and a coating liner was obtained in the same manner as in Example 1 except that 5 parts of titanium dioxide (trade name: KA-100, manufactured by COSMO CHEMICAL) were used.

Example 5
In Example 1, the surface pulp was 80% Kent waste paper and LBKP 20%, the back layer pulp was 100% corrugated paper, and 95 parts of the regenerated pigment obtained above as a paint, talc (trade name: Microtouch, supra ) 5 parts, 29 parts of adhesive (trade name: B-1535, supra), 0.8 parts of carboxymethyl cellulose (trade name: BSH, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) (all in terms of solid content) The concentration was adjusted to 30%. A coated liner was obtained in the same manner as in Example 1 except that the prepared coating was applied to the liner liner paper of Example 1 with a bar coater at 5.0 g / m ² .

Comparative Example 1
A coating liner was obtained in the same manner as in Example 1, except that 100 parts of talc (trade name: Microtouch, supra) was used.

Comparative Example 2
A coated liner obtained by applying only 0.2 g / m ² of a surface sizing agent (trade name PM385, manufactured by Arakawa Chemical Industries, Ltd.) to the liner base paper used in Example 1 was obtained.

Comparative Example 3
In Example 1, a coating liner was prepared in the same manner as in Example 1 except that 80 parts of kaolin (trade name: Konzer 1500, supra) and 20 parts of titanium dioxide (trade name: KA-100, supra) were used. Obtained.

Comparative Example 4
In Example 1, a coated liner was obtained in the same manner as in Example 1, except that the surface layer pulp was 100% Kent waste paper, the middle layer and the back layer pulp was newspaper waste paper 50%, and magazine waste paper 50%.

  The resulting coated liner was evaluated by the following evaluation method, and the results are shown in Table 1. The measurement and evaluation of the printing liner in the present invention were performed in an environment of 23 ° C. and 50% RH unless otherwise specified.

[Measurement of X-ray diffraction]
The sample was crushed in a mortar until coarse particles disappeared, and measurement was performed at a measurement condition of 40 KV, 20 mA, and a measurement range: 5 to 50 degrees using MO3XHF manufactured by Mac Science Co., Ltd.
[Calcium carbonate decomposition rate after combustion treatment]
About each Example, the calcium carbonate decomposition | disassembly rate after heat processing calculates | requires the quantity of the calcium carbonate component in the calcium sludge in paper sludge before heat processing, and the residual calcium carbonate component in a sludge baking thing in the procedure of (1)-(6) below. And evaluated.

(1) Preparation of calibration curve of calcite calcium carbonate Zinc oxide (made by Kishida Chemical Co., Ltd .: reagent grade) is used as an internal standard substance for calcium carbonate having a crystal structure of calcite (Okutama Kogyo Co., Ltd .: Tamapearl 222H). They were mixed so that the mass ratio was 1: 5, 1: 1, 5: 1. Next, each mixture was sufficiently ground using a mortar, and then measured using an X-ray diffractometer (manufactured by Max Science: MO3XHF) under conditions of 40 KV, 20 mA, and a diffraction angle measurement range of 5 to 50 degrees. Then, based on the X-ray diffraction 100% peak areas of calcium calcite and zinc oxide, a calibration curve for calcium calcite was prepared.

(2) Preparation of calibration curve for aragonite calcium carbonate Aragonite calcium carbonate was prepared in the same manner as the calibration curve for calcite calcium carbonate except that calcium carbonate having an aragonite crystal structure (Okutama Kogyo Co., Ltd .: Tama Pearl 123) was used. A calibration curve was created.

(3) Quantitative determination of calcium carbonate in papermaking sludge before combustion treatment Weighed zinc oxide (special reagent grade: the above) was added and mixed to the weighed absolute dry papermaking sludge. Next, after the mixture was sufficiently ground using a mortar, it was measured using an X-ray diffractometer (MO3XHF: supra) at 40 KV, 20 mA, and a diffraction angle measurement range of 5 to 50 degrees. Obtain 100% peak area of X-ray diffraction of calcium calcite carbonate and aragonite calcium carbonate with respect to zinc oxide, and calculate the amount of calcium carbonate (g) contained in 1 g of papermaking sludge based on the calibration curve of each calcium carbonate described above. did.

(4) Measurement of ash content of papermaking sludge Weighed absolutely dry papermaking sludge in a muffle furnace at 350 ° C for 30 minutes, weighed the mass of the resulting sludge fired product, and contained sludge ash content according to the following formula The amount (%) was measured.
Ash content (%) = (weight of sludge burned product / weight of paper drying sludge) × 100

(5) Quantitative determination of calcium carbonate in the burned sludge The weighed sludge burned product was added and mixed with a weighed zinc oxide (reagent special grade mentioned above). Next, the mixture was sufficiently ground using a mortar, then measured using an X-ray diffractometer (MO3XHF, supra) at 40 KV, 20 mA, a diffraction angle measurement range of 5 to 50 degrees, and oxidized. Obtain 100% peak area of X-ray diffraction of calcium calcite carbonate and aragonite calcium carbonate with respect to zinc, and calculate the amount of calcium carbonate (g) contained in 1 g of the sludge fired product based on the calibration curve of each calcium carbonate described above. did.

(6) Decomposition rate of calcium carbonate after combustion treatment The amount of calcium carbonate (g) in 1 g of the sludge fired product is A, the amount of calcium carbonate (g) in 1 g of papermaking sludge is B, and the ash content (%) is C. The decomposition rate of calcium carbonate after the combustion treatment was calculated by the following equation.
Calcium carbonate decomposition rate (%) = 100− [A × (C / 100)] ÷ B × 100

(Whiteness)
The whiteness was determined according to JIS P 8148 using a spectral whiteness colorimeter (manufactured by Suga Test Instruments Co., Ltd.).

(Smoothness)
JAPAN TAPPI No. According to 5-2: 2000, Oken type smoothness meter (manufactured by ASAHI-SEIKO) was used.

(Specific burst strength)
The obtained coating liner was measured according to JIS P 8131 (1995).

(Specific compression strength)
The obtained coating liner was measured according to JIS P 8126 (2005).

(Evaluation of dirt during processing)
The obtained coated liner and non-coated liner were bonded with a corrugator using a core (trade name: OPM200, manufactured by Oji Paperboard Co., Ltd.) and a back liner (trade name: OFK280, manufactured by Oji Paperboard Co., Ltd.). Corrugated sheet was made in the flute form. Thereafter, a cardboard case was prepared through a box making process. The dirt in the bonding and box making process was subjected to sensory evaluation based on the following criteria.
○: No dirt due to adhesion of foreign matter is observed on the liner surface.
Δ: Slight contamination due to adhesion of foreign matter is seen on the liner surface, but there is no practical problem.
X: Dirt due to adhesion of foreign matter is remarkably observed on the liner surface, and there is a practical problem.

(Vertical compressive strength)
Corrugated cardboard prepared for evaluation of dirt during processing was measured according to JIS Z-0403-2 (1999).

(Color development and uniformity of ink in flexographic printing)
K printing proofer (manufactured by RK Print-Coat Instruments), an anilox plate engraved at 100 lines / inch, obtained using aqueous flexo indigo ink (trade name: AQUACONTE GN39SA indigo, manufactured by Toyo Ink Co., Ltd.) Printed on the coating liner. The printed surface was measured for cyan ink density with a color reflection densitometer (Model 404G, manufactured by X-Rite).
The following visual evaluation was performed for flexographic printing uniformity.
A: The uniformity of the flexographic printing surface is excellent.
○: Slight unevenness is observed on the flexographic printing surface.
X: Light and shade unevenness is remarkably seen on the flexographic printing surface.

(Halftone dot reproducibility)
Ink is printed using a water-based flexographic ink (trade name: FK-99D-260 Kuro PR-7, manufactured by Sakata Inx Corporation) with a printing station type gravure printing tester (based on JAPAN TAPPI paper pulp test method No. 24). The 50% gradation part was magnified 25 times, and the halftone dot state was subjected to the following sensory evaluation.
○: The shape of the halftone dots is clearly recognized, but there are some defects.
Δ: A halftone dot shape is recognized, but there are more than half of the defects.
X: The shape of a halftone dot is not recognized.

As is clear from Table 1, Examples 1 to 5 contain regenerated pigment and talc in the coating layer, so that the ink density of flexographic printing is high, and the uniformity and halftone dot reproducibility are excellent. Since the corrugated cardboard and softwood unbleached kraft pulp are used for the back layer, it is excellent in terms of strength. Example 4 is slightly less regenerated pigment, but has excellent ink density, halftone dot reproducibility, and uniformity because it contains calcined kaolin. On the other hand, since Comparative Example 1 contains only talc in the coating layer, it is inferior in flexographic printing uniformity and halftone dot reproducibility. In Comparative Example 2, since there is no pigment coating layer, the flexo ink soaks in, and it is difficult to visually recognize as unevenness, and the printing uniformity is excellent, but the ink density is low, and the flexo printing quality is inferior. Also, the halftone dot reproducibility is poor. Since the comparative example 3 which does not contain a regenerated pigment in the pigment blend has poor ink absorbability, the ink concentration is low. Comparative Example 4 is inferior in strength because no corrugated paper or softwood unbleached kraft pulp is used for the middle layer and the back layer. In addition, the vertical compressive strength of the corrugated board sheet produced from the coating liner of the present invention was excellent.
As described above, according to the present invention, a coating liner capable of providing a corrugated cardboard box having excellent ink colorability and a printed surface finish for flexographic inks, particularly aqueous flexographic inks, and being resistant to impact and compression during transportation is obtained. I was able to.

The figure which shows the basic flow sheet of the manufacturing method of the inorganic particle which uses as a raw material the sludge used as the reproduction | regeneration pigment used suitably by this invention. The block diagram of an example of the heat processing apparatus using the indirect heating type rotary kiln used at the heat processing process of this invention. The block diagram of another example of the heat processing apparatus using the indirect heating type rotary kiln used in the heat processing process of this invention.

Explanation of symbols

1 Indirect heating type rotary kiln 2 Supply hopper (sludge supply port)
3 Air supply port 4 Exhaust fan
5 Indirect heating means 6 Hot air circulation fan 7 Circulation blower 8 Sludge discharge port 9 Baking chamber 10 Screw feeder S Papermaking sludge A, A 'Air flow B Papermaking sludge traveling direction

Claims (5)

In a coating liner in which a coating layer containing a pigment and an adhesive is provided on one side of a base paper composed of at least three layers, it is used for at least one of the base layer and the back layer of the base paper. The recycled pulp is corrugated waste paper and / or softwood unbleached kraft pulp, and contains recycled pigment and talc obtained by burning paper sludge as a pigment in the coating layer, and the ratio of the coating liner A coating liner having a bursting strength of 2.0 to 5.0 kPa · m ² / g. The coating liner according to claim 1, wherein a specific compressive force in a lateral direction of the coating liner is 115 to 300 N · m ² / g.   The coating liner according to claim 1 or 2, wherein the content of the regenerated pigment obtained by burning the papermaking sludge in the coating layer is 30 to 95 parts by mass per 100 parts by mass of the pigment.   The content of the talc in the said coating layer is 5-50 mass parts with respect to 100 mass parts of pigments, The coating liner of any one of Claims 1-3.   A cardboard sheet using the coating liner according to claim 1.

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