JP6212269B2 - Printing paper manufacturing method - Google Patents

Description

  The present invention relates to printing paper.

  Various fillers (titanium dioxide, calcium carbonate, kaolin, talc, hydrated silicic acid (white carbon), urea-formalin polymer fine particles, etc.) are internally added to printing paper such as newsprint to increase the opacity of white paper and printing. It is generally done. However, although these fillers are excellent in whiteness, they are expensive and low in oil absorption and do not contribute to recycling of used paper. Recycled particles obtained by dewatering and heat-treating paper sludge from the viewpoint of recycling contain metal compounds such as kaolin and hydrous magnesium silicate. These compounds have low whiteness and reduce the whiteness of the regenerated particles. It is a factor.

  Waste paper contains adhesive foreign matter (pitch) such as glue and hot melt, and these mainly adhere to fillers, ash and fine fibers having a large specific surface area in waste paper. If this sticky foreign material is brought into the papermaking process, it will adhere to and grow on the press / dryer part, etc., and will drop on the paper surface, leading to defects and leading to increased paper loss. . It is desirable to remove this sticky foreign matter as much as possible in the waste paper pulp manufacturing process. However, if this is done, a large amount of ash, etc. will be discharged out of the system together with the sticky foreign matter. This leads to an increase in external waste. Therefore, by collecting the ash, etc. discharged outside the system, the sticking foreign material is burned, the ash is burned in a temperature controlled state so as not to be overfired, and the ash is collected to greatly increase the amount of waste outside the system. It is possible to remove the sticking foreign matter without any trouble.

  On the other hand, the reuse of inorganic substances in paper sludge discharged from various processes in a paper mill as so-called recycled particles for paper making fillers has become an important issue related to environmental problems in the paper industry. As a method for producing such regenerated particles, paper sludge is used as a main raw material, and dehydration, heat treatment and pulverization steps are generally performed in this order. Such regenerated particles have been improved in various ways, but because the raw material is waste, the quality including the particle size is not constant, and the whiteness is not sufficient. Therefore, as a technique for improving the quality of fillers such as regenerated particles, composites in which particles are coated with silica have been attempted (see JP 2008-81390 A and JP 2003-49389 A). Thus, by covering the regenerated particles with silica, the yield and whiteness are improved, but the regenerated particles have not reached the same quality as other fillers.

  Further, paying attention to the problem of hardening of the obtained regenerated particles, the decrease in whiteness, the problem of thickening when solidified, and the problem of solidification, the pulverization method is specified in detail and carbon dioxide is blown in No. -356629), a method for specifying in detail how to blow carbon dioxide (see Japanese Patent Application Laid-Open No. 2009-292666), and the like have also been developed. However, these methods are excellent in improving the problem of thickening and solidifying when slurried, but the manufacturing method is complicated.

  On the other hand, as a method for solving these problems, a method for producing regenerated particles using a newspaper waste ink deinking sludge as a raw material, preferably using means for thermally decomposing calcium carbonate contained therein by 80 mass% or more has been developed. (See JP 2012-97368 A). When recycled particles made from waste newspaper deinking sludge are used as a filler for newsprint, self-circulation is preferable from the viewpoint of recycling newsprint, but means for pyrolyzing calcium carbonate by 80 mass% or more is a large amount of heat. Energy is required, black foreign matter is generated due to generation of a hot-melt hard substance accompanying high-temperature processing and carbon black of an organic substance contained in inorganic particles, and reduction of the hard substance and black foreign matter is required. Therefore, there is room for improvement in printing paper using recycled particles as a filler.

JP 2008-81390 A JP 2003-49389 A JP 2002-356629 A JP 2009-292666 A JP 2012-97368 A

  The present invention has been made in view of the above problems, and contributes to the reuse of papermaking sludge such as waste newspaper deinking floss, and is inexpensive printing paper excellent in printability, opacity and whiteness. The purpose is to provide. In particular, an object of the present invention is to provide newsprint paper with excellent opacity and whiteness and high newsprint paper recycling rate at low cost by reusing papermaking sludge such as wastepaper deinking floss.

  As a result of intensive investigations to solve the above problems, the present inventor made paper sludge mainly composed of newspaper wastepaper deinking floss as a raw material as a filler, and obtained through a dehydration process, a combustion process, and a firing process. By using the particles and finding a suitable range of the content of calcium carbonate in the regenerated particles, it was confirmed that the printing paper as described above could be provided, and the present invention was completed.

The invention made to solve the above problems is
Printing paper with internal fillers,
The filler is a paper sludge mainly composed of newspaper waste paper deinking floss, and contains regenerated particles obtained through a dehydration process, a combustion process and a firing process,
The printing paper is characterized in that the content of calcium carbonate in the regenerated particles is 65% by mass or more.

  In recent years, the regenerated particles are made of paper sludge, which is mainly made from newspaper deinking floss of newsprint paper with a high calcium carbonate content and low kaolin content. The content of calcium carbonate therein can be 65% by mass or more. For this reason, the opacity and whiteness of the printing paper can be increased by relatively reducing the amount of foreign matter contained in the regenerated particles. Further, since the recycled particles are mainly derived from used newspaper deinking floss, it is possible to effectively utilize and reuse the used newspaper deinking floss.

  In the combustion step, it is preferable to supply an oxygen-containing gas and discharge an exhaust gas having an oxygen concentration of 5% by volume to 11% by volume to form a combustion product. By supplying the oxygen-containing gas and exhausting the exhaust gas having an oxygen concentration in the above range, the combustion process can be performed at a relatively mild temperature while the papermaking sludge is self-combusted, and the result is less expensive. High quality printing paper can be obtained.

  The combustion temperature in the combustion process is preferably less than 600 ° C. By setting the combustion temperature in the above range, the combustion becomes gentle, the generation of hard substances accompanying the combustion at high temperature, the containment of unburned matter and black foreign matter in the regenerated particles, and the whiteness of the printing paper The degree can be improved.

  The decomposition rate of calcium carbonate contained in the papermaking sludge after the combustion step into calcium oxide is preferably 30% by mass or less. Thus, by setting the decomposition rate within the above range, the generation of hard substances due to combustion at high temperatures, the containment of unburned matter and black foreign matter in the regenerated particles can be reduced, and the whiteness of the printing paper can be improved. Can do.

  The filler is preferably silica-coated regenerated particles in which the regenerated particles are further coated with silica. In this way, by further covering the regenerated particles with silica, the blank paper opacity and whiteness of the printing paper can be further improved.

  Therefore, the printing paper is preferably used as newsprint paper with a blank paper opacity of 91% or more. Thus, by setting the blank sheet opacity of the print sheet to 91% or more, the print sheet can be suitably used as a newspaper sheet having excellent blank sheet opacity and an increased newspaper recycling rate.

  As described above, it is possible to provide inexpensive printing paper that contributes to the reuse of papermaking sludge such as waste newspaper deinking floss and is excellent in printability, printing opacity, and whiteness. In particular, when used in newsprint with a high blend of used newspaper pulp, recycled paper made from deinked floss derived from used newspaper is used as a filler in addition to recycling raw pulp, contributing to recycling newsprint. .

FIG. 1 shows a process chart of a method for producing regenerated particles and silica-coated regenerated particles.

The printing paper is
Printing paper with internal fillers,
The filler is a paper sludge mainly composed of newspaper waste paper deinking floss, and contains regenerated particles obtained through a dehydration process, a combustion process and a firing process,
The printing paper is characterized in that the content of calcium carbonate in the regenerated particles is 65% by mass or more.

  The printing paper is obtained by adding a filler to raw pulp. The printing paper can also contain other papermaking chemicals as long as the effects of the present invention are not impaired. Hereinafter, the printing paper and the like will be described in detail.

<Raw material pulp>
The raw material pulp is not particularly limited, and waste paper pulp, virgin pulp, or a combination thereof can be appropriately used. In addition, it is preferable from a viewpoint of resource saving to use waste paper pulp as a main component.

  Waste paper pulp includes, for example, tea waste paper, craft envelope waste paper, magazine waste paper, newspaper waste paper, leaflet waste paper, office waste paper, corrugated waste paper, Kamihiro waste paper, Kent waste paper, imitation waste paper, and old paper waste paper. Examples of such a paper include disaggregation / deinked waste paper pulp (DIP) and disaggregation / deinking / bleached waste paper pulp.

  Among these waste paper pulp, newspaper waste paper pulp derived from newspaper waste paper, magazine waste paper pulp derived from magazine waste paper, and the like are preferable, and it is more preferable to mix newspaper waste paper pulp and magazine waste paper pulp. Such waste paper pulp and magazine waste paper pulp has a high recovery rate of waste paper, and the paper pulp types and fillers that make up news paper and magazine paper are similar in each paper maker, thus suppressing fluctuations in the raw material composition. It is suitable at the point which can do. In particular, the waste paper pulp is generally 50% or more of the waste paper pulp in the news paper, and because the content of virgin mechanical pulp and kraft pulp is low, and even when various virgin pulps are used, Since it is once paper-made and used paper pulp by used paper processing, its properties are preferable because it is homogenized and has almost constant properties. Of the printing papers, it is preferable to use newspaper waste paper pulp for newsprints because the recycling rate of newsprints can be increased. The used newspaper and magazine used in the present invention mean used newspaper and magazine used in accordance with the “Recycled Paper Recycling Promotion Center“ Statistical Classification and Major Brands of Used Paper ”(revised on April 22, 2010).

  Examples of virgin pulp include hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), softwood unbleached kraft pulp (NUKP), hardwood semi-bleached kraft pulp (LSBKP), Chemical pulp such as softwood semi-bleached kraft pulp (NSBKP), hardwood sulfite pulp, softwood sulfite pulp, etc .; Stone Grand Pulp (SGP), Pressurized Stone Grand Pulp (TGP), Chemi Grand Pulp (CGP), Ground Pulp (GP), Various known pulps such as a mechanical pulp (MP) such as a thermomechanical pulp (TMP); a pulp chemically or mechanically produced from non-wood fibers such as kenaf, hemp, and straw can be used.

  Among these virgin pulps, in the production of printing paper, mechanical pulp (MP) having an effect of complementing the decrease in bulk due to the use of used paper pulp is preferable, and thermomechanical pulp suitable for adjustment of used paper pulp obtained from used paper ( TMP) is more preferred.

  The content of waste paper pulp in the raw material pulp is preferably 50% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more. By setting the content of the used paper pulp in the raw material pulp within the above range, environmental properties such as effective use of resources are improved, and printability such as ink inking properties is also improved. On the contrary, the content of virgin pulp in the raw material pulp is preferably 10% by mass or more, and more preferably 20% by mass or more. When the content of virgin pulp is less than the above range, it is difficult to adjust the strength and bulk of the printing paper, and the transportability and workability may be reduced.

<Filler>
The filler contains regenerated particles obtained through a process of burning papermaking sludge containing newspaper waste paper deinking floss as a main component. In recent years, the regenerated particles have been made into neutral paper and have used a large amount of calcium carbonate as a filler, a paper sludge mainly made of deinked floss of newsprint paper with a high calcium carbonate content and a low kaolin content. The content of the calcium compound in the regenerated particles can be increased. Therefore, the printability, opacity and whiteness of the printing paper can be improved by relatively reducing the amount of foreign matter contained in the regenerated particles. Further, since the recycled particles are mainly derived from newspaper waste paper deinking floss, they can be effectively utilized and reused.

  The filler is preferably silica-coated regenerated particles in which the regenerated particles are further coated with silica. As described above, the filler is silica-coated regenerated particles in which the regenerated particles are further coated with silica, whereby the blank paper opacity and whiteness of the printing paper can be further improved.

  The said filler can also contain another filler in the range which does not impair the effect of this invention.

<Method for producing regenerated particles and silica-coated regenerated particles>
The regenerated particles can be produced through a dehydration process, a combustion process, and a firing process using paper sludge mainly composed of newspaper waste paper deinking floss as a raw material.

Specifically, the method for producing regenerated particles is:
A process of dewatering paper sludge mainly composed of newspaper wastepaper deinking floss (dehydration process);
A process of burning the dehydrated product (combustion process);
And a step of firing the combustion product (firing step).

The method for producing the regenerated particles is after the dehydration step and before the combustion step as long as the effects of the present invention are not impaired.
A step of crushing the dehydrated product (crushing step) may optionally be included.

The production method of the regenerated particles is within the range not impairing the effects of the present invention, after the firing step,
A step of dispersing the fired product in water (slurry step);
A step of crushing the fired product in the slurry (crushing step);
A step of blowing carbon dioxide into the slurry (carbon dioxide blowing step) may optionally be included.

On the other hand, in addition to the process which the manufacturing method of the above-mentioned reproduction | regeneration particle | grains has, the manufacturing method of a silica covering reproduction | regeneration particle | grains has the
The obtained regenerated particles are coated with silica (silica coating step).

(Paper sludge (newspaper deinking floss))
As a raw material, papermaking sludge mainly composed of used newspaper deinking floss is used. “Paper sludge” refers to sludge obtained by separation from pulp fibers in a paper manufacturing process such as deinking. “Newspaper deinking floss” is a newspaper deinking pulp (NDIP) manufacturing process, which is obtained by separating from pulp fibers during deinking, and is obtained from magazine deinking pulp (MDIP), etc. It is preferable that other sludge to be contained is contained as little as possible.

  “Paper making sludge mainly composed of used newspaper deinking floss” means that the content (based on solid content) of used newspaper deinking floss in the paper making sludge is 50% by mass or more. The raw material other than the used newspaper deinking floss in the papermaking sludge is not particularly limited, and examples thereof include other papermaking sludge other than the used newspaper deinking floss. Specifically, sludge generated in other processes such as factory effluent and papermaking raw material preparation process, other deinking floss such as magazine wastepaper deinking floss, and the like can be mentioned.

  The main material (waste paper) of magazine waste paper deinking floss is coated paper and contains a lot of calcium carbonate and kaolin. For this reason, when the magazine waste paper deinking floss is used as a raw material, it becomes easy to produce | generate a cement-like substance as a foreign material. Therefore, it is preferable to refrain from using magazine waste paper deinking floss as a raw material for papermaking sludge, and to use newspaper waste paper deinking floss as a main component.

  In recent years, since the papermaking used in the production of newsprint has become neutral papermaking, the content of calcium carbonate in waste newspaper deinking floss is relatively high and the content of kaolin tends to be relatively low. is there. The ratio of calcium carbonate exceeds 70% by mass, and the proportion of kaolin is changed to less than 30% by mass. For this reason, if the main raw material of papermaking sludge is newspaper waste paper deinking floss, the amount of cementitious substances generated from calcium carbonate derived from calcium carbonate and kaolin is reduced, the resulting recycled particles are hardened, and the whiteness is low. It is easy to improve the problem of thickening and the problem of thickening and solidifying when slurryed. Therefore, the content ratio (based on solid content mass) of calcium carbonate in the inorganic particles in the papermaking sludge is usually 65% by mass or more, preferably 70% by mass or more, and more preferably 72% by mass or more. On the other hand, the amount of kaolin in the papermaking sludge (solid mass basis) is usually less than 35% by mass, preferably less than 30% by mass, more preferably less than 28% by mass, thereby suppressing the formation of hard metakaolin. Can do.

  The content of calcium carbonate in the inorganic particles in the papermaking sludge is determined according to JIS-P8251: 2003 “Paper, paperboard and pulp—ash content test method—525 ° C. combustion method”. Using an X-ray microanalyzer (model number: E-MAX · S-2150) manufactured by Seisakusho, the oxide-converted mass ratios of various elements contained in the combustion products were determined at an acceleration voltage of 15 KV. It can be calculated by performing proportional calculation based on the chemical formula and atomic weight of kaolin, talc and silicon dioxide.

  The content of newspaper deinking floss in the entire papermaking sludge is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more in terms of solid content. When the content of newspaper deinking floss in the entire papermaking sludge is less than the above value, the whiteness and oil absorption of the regenerated particles obtained may decrease due to a decrease in the content of calcium oxide contained in the papermaking sludge. In addition, the recycling rate of used newspaper is reduced.

  In the production of newspaper deinked pulp, in order to continuously obtain newspaper deinked pulp of stable quality, there is a tendency to use a certain quality newspaper that has been selected as a raw material, and the components of newspaper deinked floss are also stable. Tend to. Therefore, the quality of regenerated particles can be stabilized by using waste newspaper deinking floss as the main raw material.

  Waste newspaper deinking floss has a calorific value that is combustible, usually 1600 cal / g or more, since the ash content of the newspaper used as a raw material is relatively low and contains fat and oil components derived from newspaper ink. . Therefore, by using paper sludge made mainly from newspaper deinking floss as a starting material, combustion does not require a large amount of energy for combustion, and the oxygen concentration in the exhaust gas is burned by itself so that it falls within a predetermined range. The process can be performed at a relatively mild temperature, and fuel such as heavy oil used during combustion can be reduced.

(Dehydration process)
In the dehydration step, the dehydrated product can be obtained from the papermaking sludge. By performing this process, excess water in the papermaking sludge can be removed, and the following combustion process can be performed efficiently.

  The moisture content in the dehydrated product is not particularly limited, and is usually 30% by mass or more and 60% by mass or less, and preferably 30% by mass or more and 50% by mass or less. If the moisture content in the dehydrated product exceeds the upper limit, the load in the combustion process may increase. On the other hand, if the moisture content in the dehydrated product is less than the above lower limit, the outflow of inorganic particles to the waste liquid is increased, and the yield of the obtained inorganic particles may be decreased, and the drainage load may be increased.

  The equipment used in the dehydration step is not particularly limited, and examples thereof include known filters such as a centrifugal dehydrator, a rotary screen, a screw press, and a filter press, a centrifugal separator, a dehydrator, and a press.

(Crushing process)
In the crushing step, the crushed product can be obtained from the obtained dehydrated product. By performing this process, the dehydrated product can be crushed more uniformly and with a small particle size, and the combustion process can be performed more efficiently.

  The average particle size of the dehydrated product after crushing is not particularly limited, and is usually 2.5 mm or more and 12.5 mm or less, and preferably 3 mm or more and 7 mm or less. If the upper limit of the average particle diameter is higher than 12.5 mm, heating in the following steps may not be performed uniformly. On the other hand, if the lower limit of the average particle diameter is lower than 2.5 mm, heating in the following steps may be excessive. Here, the “average particle size” of the dehydrated product after crushing is obtained by sieving with sieves with different eye holes, measuring the mass of each sieved sample (hydrated material), and the total value of these measured values is It is the size of the eye opening of the sieve at a stage corresponding to 50% by mass of the whole, and is a value measured using a metal plate sieve based on JIS-Z8801-2: 2000.

  It does not specifically limit as a crushing method, A well-known method can be mentioned. For example, a crusher having a cylindrical body through which dehydrated matter (hydrated material) passes and a net member that rotates within the cylindrical body can be used. Moreover, as a crushing method, it can crush by using the crusher which rotates the said net | network material and collides the hydrated substance currently passing through the cylinder with the surface of a net | network material.

(Combustion process)
In the combustion process, the combustion product can be obtained from the dehydrated product. Since paper sludge mainly composed of waste newspaper deinking floss is used as a starting material, this process can be performed under a milder temperature condition and atmosphere than the conventional method due to its synergistic effect, resulting in whiteness. It is possible to produce high-quality regenerated particles that are high and contain few hard substances.

  In the combustion step, it is preferable to supply an oxygen-containing gas into the combustion furnace. Thus, paper sludge can be burned reliably and easily by supplying the oxygen-containing gas into the combustion furnace. The oxygen-containing gas is not particularly limited as long as it contains oxygen, and examples thereof include high-temperature air.

  In the combustion step, exhaust gas having an oxygen concentration of preferably 5% by volume or more and 11% by volume or less, more preferably 6% by volume or more and 10% by volume or less is discharged outside the combustion furnace. By discharging exhaust gas having an oxygen concentration in the above range to the outside of the combustion furnace in this way, the combustion process can be carried out at a milder temperature while self-burning paper sludge, and cheaper and higher quality regenerated particles can be produced. Can be obtained. Specifically, in this step, by supplying an oxygen-containing gas into the combustion furnace, the dry matter derived from the papermaking sludge in the combustion furnace is burned, and as a result, a desired combustion product (combustion ash) is obtained. be able to. The oxygen-containing gas is not particularly limited, and examples thereof include high-temperature air. Further, the oxygen concentration in the oxygen-containing gas tends to be consumed and lowered by the burner as the combustion means, but the oxygen concentration in the exhaust gas is 5% by volume or more and 11% by volume or less, preferably 6% by volume or more and 10% or less. By performing the combustion treatment so that the volume percent is less than or equal to the volume%, the combustion treatment can be achieved while suppressing the decomposition of calcium carbonate, so that regenerated particles that are soft and have high whiteness can be obtained. If the oxygen concentration exceeds the above upper limit, excessive combustion may be caused and the production of hard substances and the decomposition of calcium carbonate may be increased. If the oxygen concentration is less than the lower limit, combustion may be insufficient, and organic matter may be carbonized and oxidation may not proceed.

  Further, the temperature of the oxygen-containing gas is preferably 600 ° C. or lower, more preferably 300 ° C. or higher and 500 ° C. or lower. When the upper limit of temperature is higher than 600 ° C., calcium carbonate may be excessively decomposed. On the other hand, if the lower limit of the temperature is lower than 300 ° C., self-combustion may be impaired and combustion may be insufficient depending on the properties of the papermaking sludge. Note that the temperature of the oxygen-containing gas refers to a temperature measured using a thermocouple at the oxygen-containing gas inlet in the combustion furnace.

  By exhausting the exhaust gas having an oxygen concentration in the above range to the outside of the combustion furnace, it is possible to reuse the exhaust gas, preferably for the drying process or the carbon dioxide blowing process, and as a result, the manufacturing cost can be reduced. . Moreover, the decomposition | disassembly of the excessive calcium carbonate which was a problem conventionally can be suppressed, As a result, the burden of a carbon dioxide blowing process can be reduced. Furthermore, it is possible to suppress the thickening and solidification of the solution when it is slurried due to the generation of calcium oxide.

  The temperature of the exhaust gas is preferably 800 ° C. or lower, more preferably 640 ° C. or higher and 780 ° C. or lower, and even more preferably 680 ° C. or higher and 770 ° C. or lower. By setting the temperature of the exhaust gas within the above range, the combustion temperature during the combustion process becomes milder, and as a result, decomposition of calcium carbonate can be suppressed to a lower level. If the upper limit of the temperature is higher than 800 ° C, calcium carbonate may be excessively decomposed. On the other hand, if the lower limit of the temperature is lower than 640 ° C., combustion may be insufficient. The temperature of the exhaust gas refers to a temperature measured using a thermocouple at the exhaust gas outlet in the combustion furnace.

  The decomposition rate of calcium carbonate contained in the papermaking sludge after the combustion step into calcium oxide is preferably 30% by mass or less, and more preferably 10% by mass or more and 26% by mass or less. In this way, by setting the decomposition rate within the above range, the generation of hard substances due to combustion can be suppressed, and the organic components can be gently burned to reduce the containment of unburned matter and black foreign matter into the regenerated particles. The whiteness can be improved, which is preferable. In addition, the regenerated particles can suppress excessive decomposition of calcium carbonate, and can reduce the burden in the carbon dioxide blowing step. Furthermore, the regenerated particles can reduce the problems such as thickening and solidification of the slurry during the slurrying process, which has been regarded as a problem in the past, and as a result, the regenerated particles have high whiteness and stable inorganicity at low energy cost. Become particles. There exists a possibility that the whiteness of the said reproduction | regeneration particle | grain may fall that a decomposition rate is more than the said upper limit. If the decomposition rate is less than the above lower limit, combustion may be insufficient.

  In the combustion process, it is preferable to burn while moving the dehydrated product, crushed product, dried product and the like after the dehydration step. In this case, combustion can be performed more uniformly and continuously by moving them so as to knead, and inorganic particles with higher whiteness can be obtained. Here, “moving” is not particularly limited, and means moving inside the combustion furnace by, for example, transfer. For example, the dehydrate is continuously transferred from the outside of the combustion furnace to the inside of the combustion furnace and from the inside of the combustion furnace to the outside of the combustion furnace by a moving means such as a lifter. Moreover, it does not specifically limit as a moving means, For example, well-known means like a lifter, a feeder, a screw feeder, and a conveyor can be mentioned.

  In the combustion process, it is preferable to burn the dehydrated product after the dehydration process while moving it in the direction opposite to the flow direction of the oxygen-containing gas. By moving these in the combustion furnace in the above-mentioned direction, these combustion can be performed more uniformly and continuously, and as a result, inorganic particles with higher whiteness can be produced. . Further, floating foreign substances such as black foreign substances are taken into the exhaust gas by wind force and removed to the outside of the combustion furnace together with the exhaust gas, and as a result, the whiteness of the inorganic particles can be increased.

  Equipment used in the combustion process is not particularly limited, and examples thereof include a stalker furnace, a fluidized bed furnace, a cyclone furnace, a rotary kiln furnace, a cylindrical heat treatment furnace, a screw kiln furnace, a tower kiln furnace, a negative pressure combustion furnace, and a carbonization furnace. be able to.

  In these, the rotary kiln furnace which can perform combustion more efficiently is preferable.

  Moreover, a combustion process can be performed on moderate temperature conditions by using the above raw materials. Specifically, the combustion temperature during the combustion step is preferably less than 600 ° C., more preferably 300 ° C. or more and 500 ° C. or less, and even more preferably 320 ° C. or more and 470 ° C. or less.

  In particular, in the preferred combustion process according to the present invention, the first to third combustion treatments are used within the combustion temperature range, and the predetermined high calorific value components (acrylic organic matter and cellulose) are made in the first heat treatment. Heat treatment is removed from the sludge, thereby suppressing overcombustion and suppressing the formation of hard substances. Further, the regenerated particles obtained by pyrolyzing and gasifying acrylic organic substances and cellulose contained in the papermaking sludge in the first heat treatment and pyrolyzing and gasifying the styrenic organic substances remaining in the papermaking sludge in the second heat treatment. Therefore, it is possible to obtain regenerated particles uniformly and stably. In the third heat treatment, organic substances including residual carbon contained in the papermaking sludge are efficiently removed by heat treatment, and generation of hard substances caused by overcombustion is suppressed. Since the ignition temperature of the pyrolysis gas of cellulose is lower than the pyrolysis temperature of styrene, it is preferable that the cellulose is pyrolyzed and removed in the first heat treatment, and the styrene is pyrolyzed in the second heat treatment.

  If the upper limit of the combustion temperature is 600 ° C. or higher, excessive combustion occurs, and the production of calcium oxide due to excessive thermal decomposition of calcium carbonate is promoted, and an excessive amount of fuel is required, which may increase the manufacturing cost. It is also sufficient if the paper sludge has enough heat to start self-combustion. In addition, the generation of hard sintered material called gehlenite becomes obvious, and the papermaking equipment may be worn. On the other hand, if the lower limit of the combustion temperature is lower than 300 ° C., combustion may be insufficient. The combustion temperature and firing temperature in the present invention refer to the temperature obtained by measuring the outline of the combustion furnace with a known non-contact radiation thermometer in the external heating type rotary kiln furnace, and the internal heating type rotational kiln. In a kiln furnace, it means the temperature inside an internal combustion kiln furnace obtained by using a thermocouple. In addition, the combustion temperature of the internal heat kiln furnace may be adjusted by supplying heated air together with the supply gas into the combustion furnace. In the external heat kiln furnace, the combustion temperature should be adjusted by adjusting the temperature generated by the external heating equipment. Can do.

  When calorimetric analysis (TG / DTA) of papermaking sludge, there are three main components that burn at 200 ° C. or higher and lower than 300 ° C., 300 ° C. or higher and lower than 400 ° C., 400 ° C. or higher and lower than 500 ° C. In particular, the ratio of components that burn at 300 ° C. or higher and lower than 400 ° C. is large. From this, if the component of 300 ° C. or more and less than 400 ° C. is combusted, in particular, self-combustion, the temperature after the combustion rises to the temperature necessary for combusting the component combusted at 400 ° C. or more and less than 500 ° C. It is not necessary to increase the burner temperature (combustion temperature) using this fuel. On the other hand, when the burner temperature is less than 300 ° C., the combustion of components that burn at 300 ° C. or more and less than 400 ° C. may be insufficient.

  The raw material input amount and the combustion time are adjusted so that the unburned ratio in the combustion product obtained in the combustion process is preferably 3% by mass to 12% by mass, more preferably 4% by mass to 9% by mass. May be. When the upper limit of the unburned rate is higher than 12% by mass, combustion may be insufficient and the whiteness of the inorganic particles may be reduced. On the other hand, if the lower limit of the unburned ratio is lower than 3% by mass, the thermal decomposition of calcium carbonate becomes excessive, causing thickening and solidification in the slurrying process, and the whiteness may be lowered.

  The burning time in this step is not particularly limited, and is usually from 5 minutes to 10 hours, preferably from 1 hour to 8 hours. If the upper limit of the combustion time is longer than 10 hours, thermal decomposition of calcium carbonate may be excessive. On the other hand, if the lower limit of the combustion time is shorter than 5 minutes, combustion may be insufficient.

(Baking process)
In the firing step, the fired product can be obtained from the combustion product. By performing this step, the combustion product can be sufficiently fired, and as a result, a fired product with higher whiteness can be produced. As long as the effects of the present invention are not impaired, the fired product may be used as regenerated particles, or the regenerated particles may be recovered after the fired product is further subjected to a carbon dioxide blowing step or the like.

  The decomposition rate of calcium carbonate contained in the papermaking sludge after the firing step to calcium oxide is preferably less than 50% by mass, more preferably 20% by mass to 45% by mass, and even more preferably 20% by mass or more. It is preferable to obtain a fired product by firing the fired product after the combustion step so that the content becomes 30% by mass or less. By providing the firing step, the combustion product can be sufficiently fired, and as a result, inorganic particles with higher whiteness can be produced, which is preferable. If the upper limit of the decomposition rate is 50% by mass or more, the energy cost may increase or the whiteness of the obtained regenerated particles may decrease. On the other hand, if the lower limit of the decomposition rate is lower than 20% by mass, firing may be insufficient.

  The equipment used in the firing process is not particularly limited, and publicly known equipment can be used as in the combustion process. The combustion process and the firing process may be performed using the same equipment or different equipment.

  The firing temperature is not particularly limited, and is usually from 680 ° C. to 750 ° C., preferably from 690 ° C. to 730 ° C., more preferably from 700 ° C. to 730 ° C. Thus, there exists a tendency which can burn a combustion substance more effectively by making baking temperature into the said range. When the firing temperature exceeds the above upper limit, decomposition of calcium carbonate into calcium oxide becomes excessive, and as a result, the slurry obtained in the slurrying step may be thickened. On the other hand, if the firing temperature is less than the above lower limit, firing may be insufficient and desired whiteness may not be obtained.

  As an example of the firing step, as means for obtaining a fired product such that the decomposition rate of calcium carbonate into calcium oxide is less than 50% by mass, supply of an oxygen-containing gas and oxygen concentration of 5% by volume to 10% by volume are performed. Regenerated particles with higher whiteness can also be produced by using a series of equipment for the combustion process for exhaust gas discharge and the subsequent firing process.

  The firing time is not particularly limited, and is usually from 5 minutes to 10 hours, preferably from 1 hour to 8 hours.

(Slurry process)
In the slurrying step, the fired product can be dispersed in water to obtain a slurry. By performing this step, calcium oxide contained in the combustion product is dispersed in water to obtain a calcium hydroxide solution, and the carbon dioxide blowing step can be performed more efficiently. The calcined product obtained through the combustion process and the calcining process as described above has a low decomposition rate of calcium carbonate and a small amount of foreign matter, thereby eliminating the problems of thickening and solidifying the slurry, which has been a problem in the past. And an emulsion slurry is obtained.

  It does not specifically limit as a solvent for slurries, For example, water etc. can be mentioned. In addition, as long as the desired regenerated particles can be obtained, water may contain a small amount of a water-soluble organic solvent such as alcohol, and other components such as an electrolyte and a dispersant.

  The density | concentration of the baked product in a slurry is not specifically limited, Usually, 2 to 25 mass% is preferable, and 3 to 20 mass% is preferable.

(Crushing process)
In the pulverization step, the fired product in the slurry can be pulverized. By performing this process, the following carbon dioxide can be blown efficiently.

  The average particle size of the pulverized product is not particularly limited, and is usually 0.5 μm or more and 10 μm or less, preferably 1 μm or more and 8 μm or less, more preferably 1 μm or more and 4 μm or less. When the upper limit of the average particle diameter is higher than 10 μm, there is a possibility that paper powder is generated or the flatness of the paper surface is impaired as a foreign matter when used as a filler or pigment for papermaking. On the other hand, if the lower limit of the average particle size is lower than 0.5 μm, the particles aggregate to show a broad particle size distribution, or flow away in the papermaking system, resulting in a decrease in yield, and excessive energy is required for grinding. There is a risk of becoming. The average particle diameter here is a volume average particle diameter (D50) measured using a particle size distribution diameter of a laser diffraction method (manufactured by Shimadzu Corporation, product name SA-LD-2200).

  It does not specifically limit as a grinding | pulverization method, For example, stirring a slurry with a serie mixer etc. is mentioned.

(CO2 blowing process)
In the carbon dioxide blowing step, desired regenerated particles can be obtained by blowing carbon dioxide into the slurry. By performing this step, carbon dioxide is blown into the slurry, calcium carbonate is obtained from calcium oxide and calcium hydroxide derived therefrom (carbonation treatment), and the content of calcium carbonate in the regenerated particles is increased. Thus, high-quality regenerated particles with high whiteness can be obtained. Moreover, even when the coarse particles in the slurry contain a small amount of metakaolin or hydrous magnesium silicate, calcium carbonate obtained from calcium oxide or calcium hydroxide derived from it can adhere to and coat the surface. Also from the viewpoint, high-quality regenerated particles with high whiteness can be obtained.

  It does not specifically limit as a blowing method of a carbon dioxide, A well-known method can be mentioned. For example, carbon dioxide-containing gas is guided to the diffuser in the reaction vessel through the transport pipeline, and fine bubbles are generated from each of the diffuser groups in the slurry accommodated in the reaction vessel. Further, the slurry may be stirred with a stirring blade provided on the diffuser group.

  Carbon dioxide used in the carbon dioxide blowing step is not particularly limited, and examples thereof include commercially available carbon dioxide gas, mixed gas containing carbon dioxide, and exhaust gas obtained in the combustion step. In this step, it is preferable to use exhaust gas obtained in the combustion step from the viewpoint of reuse. The concentration of carbon dioxide in the exhaust gas is usually 5% by volume or more and 20% by volume or less, preferably 8% by volume or more and 20% by volume or less, more preferably 10% by volume or more and 20% by volume or less for the purpose of promoting the carbonation reaction. It is as follows. There is a tendency that a gas whose upper limit of concentration is higher than 20% by volume cannot be obtained as the capability of the combustion process. In order to obtain a carbon dioxide concentration of 20% or more, it is necessary to make a capital investment for separately installing equipment, and a desired combustion product may not be obtained in the combustion process. On the other hand, if the lower limit of the concentration is lower than 5% by volume, calcium carbonate may not be sufficiently precipitated in the carbon dioxide blowing step, and it takes a long time to complete the reaction, and the particle size cannot be controlled within the desired range. There is. In the present invention, since the exhaust gas obtained in the incineration process contains a large amount of carbon dioxide, the exhaust gas obtained in the combustion process can be reused in the drying process and the carbon dioxide blowing process. Moreover, dry ice can also be used together as solid carbon dioxide.

  Completion of the carbonation reaction can also be confirmed by a decrease in the pH of the slurry solution. Specifically, assuming that the pH of the slurry at the end of the carbonation reaction after the blowing of carbon dioxide is the post-reaction pH, the post-reaction pH is usually 6.8 or more and 7.8 or less, preferably 6.9 or more. 7.7 or less.

(Silica coating process)
In the silica coating step, the obtained regenerated particles are coated with silica. By carrying out this step, silica-coated regenerated particles with higher printing opacity and whiteness can be produced.

  The silica coating method is not particularly limited. For example, an alkali silicate aqueous solution and a mineral acid are added to the aggregate slurry in this order, and the silica is coated on the aggregate surface, or the aggregate slurry is applied to the alkali silicate aqueous solution. In addition, there is a method of mixing and then adding a mineral acid to coat silica.

  It does not specifically limit as said alkali silicate aqueous solution, For example, sodium silicate aqueous solution (No. 3 water glass) etc. are mentioned.

  The mineral acid is not particularly limited, and examples thereof include dilute sulfuric acid, dilute hydrochloric acid, and dilute nitric acid.

  Of these, dilute sulfuric acid is preferred for reasons such as price, handling, prevention of calcium content in calcium carbonate, and countermeasures against corrosion of facilities and equipment.

  It does not specifically limit as process temperature of a silica coating process, Usually, 50 to 100 degreeC is preferable and 50 to 98 degreeC is preferable.

  The process time of the silica coating process is not particularly limited, and is usually 5 minutes to 10 hours, and preferably 10 minutes to 1 hour.

<Regenerated particles>
The regenerated particles are produced through the manufacturing process as described above using papermaking sludge mainly composed of newspaper waste paper deinking floss as a raw material. Therefore, the papermaking sludge mixed with various conventional components is used as a raw material. Unlike the case, the regenerated particles obtained have a small amount of foreign matter. Therefore, the content of calcium carbonate in the regenerated particles is 65% by mass or more, preferably 70% by mass or more, and more preferably 72% by mass or more in terms of calcium oxide. Thus, the whiteness of the said reproduction | regeneration particle | grains can be improved by making content of calcium carbonate into the said range. When the content of calcium carbonate is less than the above lower limit, the whiteness of the regenerated particles decreases.

  The content of calcium carbonate in the regenerated particles is, for example, an oxide of various elements contained in the regenerated particles at an acceleration voltage of 15 KV using an X-ray microanalyzer (model number: E-MAX · S-2150) manufactured by Horiba, Ltd. It can calculate by calculating | requiring a conversion mass ratio and performing a proportional calculation based on this result, the chemical formula of calcium carbonate, kaolin, talc, and silicon dioxide, and atomic weight.

  The whiteness of the regenerated particles is not particularly limited, and is usually 72% or more, preferably 76% or more and 85% or less, and more preferably 77% or more and 83% or less. Thus, by setting the whiteness to the above range, the whiteness of the printing paper tends to be improved. If the whiteness exceeds the above upper limit, the production cost may increase. If the whiteness is less than the lower limit, the whiteness of the printing paper may be reduced.

  The average particle size of the regenerated particles is not particularly limited and is usually 1 μm or more and 10 μm or less, preferably 1.5 μm or more and 8 μm or less, and more preferably 2 μm or more and 6 μm or less. Thus, by making an average particle diameter into the said range, the yield property, opacity, etc. at the time of using as a filler in paper manufacture can be improved, and there exists a tendency for wire wear property to improve. When the average particle diameter exceeds the above upper limit, when used as a filler internally added to paper, the bond strength between pulp fibers is lowered, and the paper strength of printing paper may be lowered. If the average particle diameter is less than the above lower limit, the yield is low, and the effect of improving the oil absorption and opacity may not be seen. The average particle diameter here is a volume average particle diameter (D50) measured using a laser diffraction particle size distribution meter (manufactured by Shimadzu Corporation, product name SA-LD-2200).

  The oil absorption amount of the regenerated particles is not particularly limited, and is usually 30 mL / 100 g or more and 100 mL / 100 g or less, and preferably 50 mL / 100 g or more and 90 mL / 100 g or less. Thus, there exists a tendency for the printability of a printing paper to improve by making oil absorption amount into the said range. If the amount of oil absorption exceeds the above upper limit, uneven printing density may occur. If the oil absorption is less than the above lower limit, the printing opacity and ink fillability may be reduced.

  The abrasion degree of the regenerated particles is not particularly limited, and is usually 70 mg or more and 150 mg or less, and preferably 75 mg or more and 145 mg or less. This indicates that the hard particles content of the regenerated particles is small and has excellent wear characteristics.

<Silica-coated regenerated particles>
The filler is preferably silica-coated regenerated particles in which the regenerated particles are further coated with silica. Thus, by further covering the regenerated particles with silica, the printing opacity and whiteness of the printing paper can be further improved. Also, as described later, by depositing and coating silica in an aqueous solution, it is possible to efficiently coat the regenerated particle aggregate, and it is possible to coat in a porous state, so that the silica-coated regenerated particles are excellent. Demonstrate oil absorption ability.

  The silica content of the silica-coated regenerated particles is not particularly limited, and is usually 5% by mass to 15% by mass, and preferably 6% by mass to 13% by mass. Thus, by setting the silica content in the above range, sufficient precipitation of silica can be obtained on the surface of the regenerated particles, preventing ink sinking, and improving the whiteness and printing opacity of the printing paper. This is preferable. If the silica content exceeds the above upper limit, fine silica particles may be excessively precipitated, leading to a decrease in oil absorption and opacity. On the other hand, if the silica content is less than the above lower limit, sufficient silica cannot be deposited on the surface of the regenerated particles, and the whiteness and printing opacity of the printing paper may be lowered.

  The content of calcium carbonate in the silica-coated regenerated particles is not particularly limited, and is preferably 52% by mass or more and more preferably 60% by mass or more in terms of calcium oxide. Thus, the whiteness of the said printing paper can be improved by making content into the said range. If the content of calcium carbonate in the silica-coated regenerated particles is less than the lower limit, the whiteness of the printing paper may be reduced.

  The whiteness of the silica-coated regenerated particles is not particularly limited and is usually 75% or more and preferably 78% or more. Thus, by setting the whiteness to the above range, the whiteness of the printing paper tends to be improved. If the whiteness is less than the lower limit, the whiteness of the printing paper may be reduced.

  The average particle diameter of the silica-coated regenerated particles is not particularly limited, and is usually from 1.7 μm to 10 μm, and preferably from 3 μm to 7 μm. Thus, by making an average particle diameter into the said range, there exists a tendency which can improve the yield property, opacity, etc. at the time of using as a filler in paper manufacture, and can improve wire abrasion. When the average particle diameter exceeds the above upper limit, when used as a filler internally added to paper, the bond strength between pulp fibers is lowered, and the paper strength of printing paper may be lowered. If the average particle diameter is less than the above lower limit, the yield is low, and the effect of improving the oil absorption and opacity may not be seen.

  The oil absorption amount of the silica-coated regenerated particles is not particularly limited, and is usually from 30 mL / 100 g to 100 mL / 100 g, and preferably from 50 mL / 100 g to 100 mL / 100 g. Thus, there exists a tendency for the printability of a printing paper to improve by making oil absorption amount into the said range. If the amount of oil absorption exceeds the above upper limit, uneven printing density may occur. If the oil absorption is less than the above lower limit, the printing opacity and ink fillability may be reduced.

<Other fillers>
The filler can also contain other fillers other than the regenerated particles and the silica-coated regenerated particles as long as the effects of the present invention are not impaired. Other fillers are not particularly limited, and examples include titanium oxide, calcium carbonate, kaolin, talc, barium sulfate, white carbon (hydrated silicic acid), urea-formalin polymer fine particles, and the like.

<Other papermaking chemicals>
Other papermaking chemicals are not particularly limited. For example, surfactants, waxes, sizing agents, rust preventives, conductive agents, antifoaming agents, dispersants, viscosity modifiers, flocculants, coagulants, and paper strength enhancement. Agents, yield improvers, paper powder fall-off prevention agents, bulking agents, binders, surface treatment agents and the like.

  In these, a surface treating agent and a sizing agent are preferable.

  By adding the above regenerated particles or silica-coated regenerated particles as a filler, and further applying a surface treatment agent, the amount of the filler added can be suppressed, opacity can be ensured, and in combination with the surface treatment agent, more printing can be achieved. Generation of paper dust can be suppressed. In addition, the opacity of the printing paper can be improved.

  The surface treatment agent is not particularly limited, and examples thereof include oxidized starch and hydroxyethylated starch. It is preferable to apply a coating solution of oxidized starch and hydroxyethylated starch in a solid content ratio of 3: 7 to 7: 3.

The coating amount of the surface treatment agent is not particularly limited, and is usually 0.1 g / m ² or more and 2.0 g / m ² or less, and 0.3 g / m ² or more and 1 or less in terms of dry mass per side on the front and back surfaces of paper. 0.5 g / m ² or less is preferable. Thus, there exists a tendency for the surface strength of printing paper to fully improve by making application quantity into the said range. When the coating amount exceeds the above upper limit, a large amount of mist of a surface treatment agent such as starch is generated around the coating equipment, and the peripheral equipment may be soiled, and paper breakage and paper defects may be caused due to the soiling. When the coating amount is less than the above lower limit, it is difficult to obtain a sufficient film with starch or the like, and there is a possibility that sufficient paper surface strength cannot be obtained.

  Further, by using the surface sizing agent, it is possible to suppress the penetration of liquid such as ink into the paper, and to reduce the set-off and bleeding.

  It does not specifically limit as a surface sizing agent, For example, a styrene-type sizing agent etc. are mentioned.

<Printing paper manufacturing method>
The method for producing the printing paper is not particularly limited, and examples thereof include a method of making a pulp slurry containing raw material pulp, filler and the like.

  In the above method, first, a pulp slurry is prepared and paper is made to obtain a base paper. The pulp slurry can contain the above-mentioned other fillers as well as the above-mentioned filler.

  You may apply | coat the said surface treating agent to both surfaces of the base paper obtained by the said papermaking. The surface treatment agent coating apparatus is not particularly limited, and examples thereof include a size press, a blade metalling size press, a rod metalling size press, a blade coater, a bar coater, a gate roll coater, a rod coater, and an air knife coater.

  The temperature of the base paper during the application of the surface treatment agent is not particularly limited, and is usually 35 ° C. or higher and 85 ° C. or lower, and preferably 40 ° C. or higher and 75 ° C. or lower.

  After the surface treatment agent is applied and dried, in order to improve printability (for example, high smoothness and high gloss), the paper may be passed through a calendar and subjected to pressure finishing. The calendar device is not particularly limited, and examples thereof include a super calendar, a gloss calendar, and a soft compact calendar.

<Printing paper>
The printing paper is excellent in opacity and whiteness as described above.

  Specifically, the blank paper opacity of the printing paper is preferably 91% or more, more preferably 91% or more and 96.5% or less, and even more preferably 92% or more and 96% or less. By setting the blank paper opacity within the above range, the opacity of the printing paper is improved. When the blank paper opacity exceeds the above upper limit, the necessary filler is increased, and as a result, the adhesion between the pulp fibers is lowered, and the strength of the printing paper may be lowered. If the blank paper opacity is less than the above lower limit, the print paper may fall through and may not be suitable for use as newsprint.

  The printing opacity of the printing paper is preferably 91% or more, more preferably 91% or more and 94.5% or less, and even more preferably 91.5% or more and 94.0% or less. By setting the printing opacity within the above range, the opacity of the printing paper tends to be improved. If the printing opacity exceeds the above upper limit, the necessary filler increases, resulting in a decrease in the adhesion between the pulp fibers, the strength of the printing paper decreases, or the paper during printing due to the loss of the filler from the paper surface. There is a risk of increased powder and contamination in the machine system during the manufacturing process. If the printing opacity is less than the above lower limit, there is a possibility that show-through may occur.

  The whiteness of the printing paper is preferably 50% or more and 56% or less, and more preferably 51% or more and 55% or less. By setting the whiteness to the above range, the whiteness of the printing paper tends to be improved. When the whiteness exceeds the above upper limit, the blank paper opacity is lowered, and there is a possibility that the showthrough occurs. When the whiteness is less than the above lower limit, the opacity is improved, but the appearance of the printed surface may be deteriorated.

  The tensile strength in the longitudinal direction of the printing paper is preferably 2.0 kN / m or more and 2.8 kN / m or less, more preferably 2.1 kN / m or more and 2.7 kN / m or less. By setting the tensile strength within the above range, the printing paper tends to have sufficient strength. When the tensile strength exceeds the above upper limit, the filler is insufficient, and the opacity and whiteness may decrease. There exists a possibility that the intensity | strength of the said printing paper may become inadequate that tensile strength is less than the said minimum.

The basis weight of the print sheet is not particularly limited, is usually 39g / ^{m 2} or more 47 g / ^{m 2} or less, 39.5 g / ^{m 2} or more 44.5 g / ^{m 2} or less. Thus, the printing paper tends to have sufficient strength by setting the basis weight within the above range. If the basis weight exceeds the above upper limit, it goes against the recent weight reduction and resource saving. If the basis weight is less than the above lower limit, for example, it may be difficult to ensure strength in a high-speed offset rotary printing press.

  The ash content of the printing paper is not particularly limited and is usually 5% by mass to 20% by mass, and preferably 7% by mass to 17% by mass. Thus, by making ash into the said range, there exists a tendency for the opacity and whiteness of the said printing paper to improve. Further, since the filler fills the voids of the fibers, the penetration of the surface treatment agent can be suppressed, and as a result, the surface strength and the printing workability tend to be improved. If the ash content exceeds the above upper limit, the tensile strength may be reduced, causing a paper breakage trouble during the paper making process or rotary printing, and there is a risk of increasing paper dust during the rotary printing. If the distribution is less than the above lower limit, there is a risk that the filler will be insufficient and show through.

<Others>
Other process conditions such as temperature, pressure, time, and equipment in the production process are not particularly limited, and are appropriately set according to the raw materials used. The number of stages in the production process is not particularly limited, and may be performed in one stage or in multiple stages. The quantification and qualification of raw materials and products can be performed according to known methods such as NMR, IR, elemental analysis, and mass spectrum. Moreover, the raw material to be used may be used independently and may be used combining multiple types of raw material.

  The printing paper is excellent in printability, opacity and whiteness. Therefore, the printing paper can be suitably used as an application that requires such characteristics, for example, newsprint.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limited to these.

<Evaluation method>
The evaluation methods performed in the examples and comparative examples will be described.

(Oxygen concentration)
The oxygen concentration (volume%) was measured by using an automatic oxygen concentration measuring device (manufactured by Horiba, Ltd., product name ENDA-5250).

(Process temperature)
The process temperature (° C.) such as the combustion temperature and the firing temperature was measured using a thermocouple or the like in the process equipment.

(Unburnt rate)
The unburned rate (mass%) is a value obtained by calculating the unburned amount from the change in weight before and after combustion after placing the sample in a crucible after the temperature of the electric muffle furnace is raised to 600 ° C. in advance and completely burning in about 3 hours.

(CO2 concentration)
The carbon dioxide concentration (volume%) is a value measured using an automatic carbon dioxide concentration measuring device (Tech Jam, trade name TESTO-535).

(PH)
The pH (post-reaction pH and product pH) is a value measured using an automatic pH measuring device (product name: PH450G, manufactured by Yokogawa Electric Corporation).

(Decomposition rate of calcium carbonate)
The decomposition rate (mass%) of calcium carbonate was measured using a measuring device (product name TG / DTA6200, manufactured by SII Nano Technology), and the measurement conditions were as follows: (1) Temperature rising rate 20 ° C./min (25 ° C. or higher) (2) Supply gas air (oxygen concentration about 5% by volume), (3) Supply gas flow rate is about 48 mL / min.

(Calcium carbonate content)
The content (mass%) of calcium carbonate in the inorganic particles in the papermaking sludge is a residue obtained by ashing the sample in accordance with JIS-P8251: 2003 “Paper, paperboard and pulp-ash content test method—525 ° C. combustion method”. Using an elemental analyzer (X-ray microanalyzer (Horiba Seisakusho, product name E-MAX / S-2150)), the oxide-converted mass ratios of various elements contained in the combustion products at an acceleration voltage of 15 KV This is a value obtained by performing proportional calculation based on this result and the chemical formula and atomic weight of calcium carbonate, kaolin, talc and silicon dioxide. Similarly, the content of calcium carbonate in the obtained regenerated particles was determined by using an elemental analyzer (X-ray microanalyzer (manufactured by Horiba Ltd., product name E-MAX · S-2150)) as an acceleration voltage of 15 KV. Is a value obtained by performing proportional calculation based on this result, the chemical formulas of calcium carbonate, kaolin, talc and silicon dioxide, and atomic weight. .

(Average particle size)
The average particle diameter (μm) is a value obtained by measuring the volume average particle diameter (D50) using a laser diffraction particle size distribution diameter (manufactured by Shimadzu Corporation, product name SA-LD-2200). In the preparation of the measurement sample, particles were added to a 0.1% sodium hexametaphosphate aqueous solution and dispersed with an ultrasonic wave for 1 minute.

(Silica content)
The silica content (mass%) was measured by elemental analysis at an acceleration voltage (15 KV) using an X-ray microanalyzer (model number: E-MAX · S-2150) manufactured by Horiba, Ltd. Then, the content ratios of kaolin, talc, silica and the like were estimated, and the silica content (% by mass) was calculated from the content of the silica component after the silica coating.

(Whiteness)
The whiteness (%) of the regenerated particles and silica-coated regenerated particles is a value measured by using a color difference meter (manufactured by Tokyo Denshoku Co., Ltd., product name SP-80), grinding the powder sample with a mortar, and packing it in a glass cell. It is.

(Oil absorption)
The oil absorption (mL / 100 g) was measured according to JIS-K5101-13-1: 2004. That is, 2 g or more and 5 g or less of a sample dried at 105 ° C. or more and 110 ° C. or less for 2 hours is placed on a glass plate, and refined linseed oil (having an acid value of 4 or less) is dropped from the buret to the center of the sample little by little. Then, the dripping and kneading operations were repeated, and the amount of refined linseed oil dropped was determined with the time when the whole was first assembled into one rod shape as the end point, and the oil absorption amount was calculated by the following formula (1).
Oil absorption (mL / 100g)
= [Look of linseed oil (mL) x 100] / sample (g) (1)

((Wire) wear degree)
The plastic wire wear degree (manufactured by Nippon Filcon Co., Ltd., product name: wire wear degree tester, 3 hours) is a value measured at a slurry concentration of 2% by mass.

(Basis weight)
Basis weight (g / m < ² >) was measured based on JIS-P8124: 2011 "Paper and board-Basis weight measuring method".

(ash)
Ash content (mass%) was measured in accordance with JIS-P8251: 2003 “Paper, paperboard and pulp-ash content test method—525 ° C. combustion method”.

(Blank paper opacity)
The blank paper opacity (unit:%) was measured in accordance with JIS-P8149: 2000 “Paper and paperboard—Opacity test method (backing of paper) —diffuse illumination method”.

(Print opacity)
The printing opacity (%) is measured according to JAPAN TAPPI No. No. 45 (2000) “Newspaper—Post-printing opacity test method”, and measured using a measuring instrument ISO whiteness meter (manufactured by Suga Test Instruments Co., Ltd.).

(Whiteness)
The whiteness (%) was measured in accordance with JIS-P8148: 2001 “Paper, paperboard and pulp—Measurement method of ISO whiteness (diffuse blue light reflectance)”.

(Tensile strength (longitudinal))
The tensile strength (longitudinal) (unit: kN / m) was measured in accordance with JIS-P8113: 2006 “Paper and paperboard—Testing method of tensile properties—Part 2: Constant speed stretching method”.

(Ink fillability)
Ink fillability using an offset printing machine (model number: Komori SYSTEMC-20, manufactured by Komori Corporation) and newspaper ink (trade name: News Zet Naturalis (black), manufactured by Dainippon Ink & Chemicals, Inc.) Continuous 10,000 copies were printed. About the obtained printed matter, the clearness and the shading unevenness of an image were observed visually, and it evaluated based on the following evaluation criteria.

[Evaluation criteria]
5: The image is clear and there is no unevenness in density, and the ink deposition property is excellent.
4: The image is clear, there is almost no unevenness in density, and the ink deposition property is good.
3: There are some portions where the image is unclear and some shading unevenness.
2: There are a portion where the image is unclear and uneven density, and ink deposition is not good.
1: Overall, the image is unclear, the density unevenness is remarkable, and the ink deposition property is inferior.

(Blanket paper powder piling)
Blanket paper dust piling uses an offset rotary printing press (model number: LITHOPIA BTO-4, manufactured by Mitsubishi Heavy Industries) to print 100,000 copies on both sides of printing paper on 50 continuous rolls. The occurrence and accumulation of paper dust in the blanket non-image area were visually observed and evaluated based on the following evaluation criteria.

[Evaluation criteria]
5: Generation | occurrence | production of paper surface scraps and paper dust is not recognized at all.
4: Scratch on the paper surface is slightly observed, but no deposition on the blanket is observed.
3: Scratch on the paper surface is slightly recognized and a little accumulation on the blanket is recognized.
2: Generation | occurrence | production of the paper surface scraping was recognized and it has accumulated on the blanket.
1: Accumulation of paper dust on the paper surface and blanket is remarkable.

<Production of regenerated particles of Production Example 1>
(Paper sludge (raw material))
In the wastepaper deinking process, the foamy newspaper deinking floss that was floated and removed from the wastepaper pulp by the floatation method (floating method) and in the magazine wastepaper deinking process, the floating separation method floated from the magazine wastepaper pulp. The flocculant (product name: MX2101, manufactured by Hymo Co., Ltd.) is added to the deinking flotation waste liquid in which the removed foam-like magazine deinking floss is mixed at a solid content ratio of 9: 1, and the solid content in the waste liquid is added. To make papermaking sludge.

(Dehydration process)
Subsequently, the raw material was sequentially passed through a rotary screen (manufactured by Togoku Kogyo Co., Ltd.) and a screw press (manufactured by Hokurin Seisakusho Co., Ltd.) to recover a dehydrated product having a moisture content of 40% by mass.

(Crushing process)
Next, the dehydrated product was crushed using a crusher to obtain a crushed dehydrated product having an average particle diameter of 3.5 mm.

(Combustion process)
Next, the dehydrated product after crushing was burned using a rotary kiln furnace (manufactured by Actley) at a combustion temperature of 350 ° C. and a combustion time of 4 hours. During combustion, high-temperature air (oxygen-containing gas) was supplied into the combustion furnace, and the exhaust gas was discharged out of the combustion furnace while adjusting the oxygen concentration in the exhaust gas to 9.0% by volume. The decomposition rate of calcium carbonate contained in the papermaking sludge into calcium oxide was 22% by mass.

(Baking process)
Next, the combustion product was fired in the same manner using a rotary kiln furnace (manufactured by Actley) at a firing temperature of 720 ° C. and a firing time of 3 hours. After the firing step, the decomposition rate of calcium carbonate contained in the combustion product into calcium oxide was 27% by mass.

(Slurry process)
Next, the combustion product was mixed with water and dispersed using a mixer (manufactured by Eirich) to obtain a slurry having a concentration of 17% by mass.

(Crushing process)
Subsequently, the fired product in the slurry was pulverized using a bead mill type wet pulverizer (manufactured by Eirich) to obtain a burned product having an average particle size of 1.7 μm.

(CO2 blowing process)
Next, the exhaust gas containing carbon dioxide obtained in the combustion process is introduced into the slurry obtained from the diffuser, and the content of calcium carbonate is 75% by mass, the average particle size is 2.9 μm, and the whiteness is 78.0%. The regenerated particles of Production Example 1 having an oil absorption of 55 mL / 100 g and a (wire) wear level of 123 mg were obtained.

<Manufacture of silica-coated regenerated particles>
(Silica coating process)
The regenerated particles obtained in Production Example 1 were dispersed in water to obtain a regenerated particle slurry of 17% by mass (solid content concentration). The regenerated particle slurry (10,000 kg) is placed in a tank equipped with a stirrer, and stirred with a sodium silicate aqueous solution (No. 3 sodium silicate: SiO ₂ concentration 29 wt / wt%, Na ₂ O concentration 9.5 wt / wt%) 469 kg and dilution water And the solid content concentration of the slurry composed of alkali silicate and regenerated particles was adjusted to 11% by mass. Diluted sulfuric acid (4 N) was added and stirred as a mineral acid to obtain a silica-coated regenerated particle slurry. The slurry was stirred using a known mixer, the pH of the slurry was measured with a pH meter manufactured by Horiba, and the reaction temperature was measured with a known thermometer. In the primary reaction step, dilute sulfuric acid was added for 22 minutes so that the neutralization rate of the sodium silicate aqueous solution and sulfuric acid was 33%. Next, the temperature of the slurry was adjusted to 93 ° C. by heating and stirring. Thereafter, in the secondary reaction step, dilute sulfuric acid was added for 45 minutes until the pH of the dilute sulfuric acid reached 8.4 to obtain a silica-coated regenerated particle slurry. The obtained silica-coated regenerated particles had a silica composite rate of 8% by mass, a volume average particle size of 4.5 μm, a whiteness of 82%, an oil absorption of 88 mL / 100 g, and a wire wear of 82 mg.

<Regenerated Particle Production Examples 2-9, Regenerated Particle Comparative Production Examples 1-2>
Regenerated particles of Production Examples 2 to 9 and Comparative Production Examples 1 and 2 were produced in the same manner as Production Example 1 except that the raw material composition and the like were changed as shown in Table 1.

<Example 1>
A pulp slurry containing 85% by mass of newspaper waste paper pulp and 15% by mass of thermomechanical pulp (TMP) was obtained. To this pulp slurry, 30 kg / ton of regenerated particles of Production Example 1 as a filler per ton of pulp solid content was added at a solid content of 30 kg / ton, and 0.07 parts by mass of a flocculant per 100 parts by mass of absolutely dry pulp (manufactured by BASF, product Nominal polymin PR8150) and 0.05 part by weight of a coagulant (manufactured by BASF, product name: Cathiofast SF) were added to make a base paper having a basis weight of 41.8 g / m ² using a twin wire paper machine.

Furthermore, styrene is added to a starch solution in which 50 parts by mass of oxidized starch (manufactured by Nippon Food Processing Co., Ltd., product name MS-3800) and 50 parts by mass of hydroxyethylated starch (manufactured by Penford Co., Ltd., product name HES) are mixed as a surface treatment agent. A system sizing agent (product name: SS2712 manufactured by Seiko PMC Co., Ltd.) was blended in an amount of 15 parts by mass with respect to 100 parts by mass of starch. The surface treatment agent was applied to both surfaces of the base paper having a surface temperature of 50 ° C. in a dry mass of 1.2 g / m ² (each 0.6 g / m ² per side) to obtain a printing paper of Example 1. The ash content of the printing paper is 9.4% by mass, the blank paper opacity is 94.3%, the printing opacity is 92.0%, the whiteness is 54.0%, and the tensile strength in the longitudinal direction. Was 2.49 kN / m.

<Examples 2 to 10 and Comparative Examples 1 and 2>
Examples 2 to 10 and Comparative Examples 1 and 2 were performed in the same manner as Example 1 except that the raw materials and the like were changed as shown in Table 2.

  Table 2 shows the raw materials used in the examples and comparative examples and the evaluation results.

  From Table 2, it can be seen that the printing paper obtained in the examples is superior in whiteness, blank paper printing opacity, printing opacity, tensile strength, printability and the like than those obtained in the comparative examples.

  The printing paper is excellent in printability, opacity and whiteness. Therefore, the printing paper can be suitably used as an application that requires such characteristics, for example, newsprint.

S Papermaking sludge R ¹ Regenerated particle R ² Silica coated regenerated particle

Claims (4)

Printing paper with internal fillers,
The filler is a paper sludge mainly composed of newspaper waste paper deinking floss, and contains regenerated particles obtained through a dehydration process, a combustion process and a firing process,
The combustion temperature of the combustion process is 320 ° C. or higher and 470 ° C. or lower;
A method for producing a printing paper , wherein the content of calcium carbonate in the regenerated particles is 65% by mass or more. The method for producing a printing paper according to claim 1, wherein in the combustion step, an oxygen-containing gas is supplied and an exhaust gas having an oxygen concentration of 5% by volume to 11% by volume is discharged to form a combustion product. The method for producing a printing paper according to claim 1 or 2 , wherein a decomposition rate of calcium carbonate contained in the papermaking sludge after the combustion step into calcium oxide is 30% by mass or less. The method for producing a printing paper according to claim 1, wherein the filler is silica-coated regenerated particles in which the regenerated particles are further coated with silica.

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