JP2012117177A - Newsprint paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a newsprint paper that is high in surface strength and excellent in printing workability, while having a high filler content and being high in opacity.SOLUTION: The newsprint paper includes a base paper for newsprint paper and both sides of the base paper for newsprint paper are coated with a surface treatment agent. The surface treatment agent contains an oxidized starch and a hydroxyethylated starch, the content ratio of the oxidized starch to hydroxyethylated starch is 1:9 or more and 9:1 or less in terms of mass, and the ash content is 5% or more and 20% or less. The surface treatment agent preferably has a B type viscosity of 5 cps or more and 80 cps or less.

Description

  The present invention relates to newsprint.

  Printing on newsprint is generally performed by offset printing. In this offset printing, dampening water is added to the paper surface. For this reason, when paper with low surface strength is used for offset printing, paper dust is generated from the paper surface, which may cause troubles such as smearing on the printing surface due to accumulation on the blanket or mixing with ink. . In addition, inorganic pigments (fillers) that are added to newsprint to increase opacity are easily spilled from the paper by dampening water during offset printing, resulting in paper dust that causes blanket piling. Yes. In particular, in recent years, the amount of filler added has increased due to the high opacity associated with the reduction in weight of newsprint, and prevention of the filler from falling off during printing has become an important issue.

  In order to cope with such problems of offset printing, it is a common practice to apply a surface treatment agent containing a water-soluble polymer material such as starch, polyvinyl alcohol, or polyacrylamide to the surface of newspaper. These surface treatment agents improve the printing workability by increasing the strength of the paper surface and strongly adhering fine fibers and fillers on the paper surface to the paper. However, when the amount of the surface treatment agent applied increases, the adhesiveness of the paper surface increases in a wet state, and there is a problem called Nappari trouble that the paper sticks to the blanket during printing or induces paper breakage. appear.

  Therefore, for the purpose of increasing the surface strength and suppressing the occurrence of Nepari trouble, it is newsprint paper coated with a surface treatment agent containing a specific processed starch, and further the viscosity and the coating amount of this surface treatment agent Those with limited relationships have been developed (see Japanese Patent Application Laid-Open Nos. 2003-113592 and 2009-235664). As the specific processed starch, etherified starch, esterified starch, aldehyded starch, hydroxyethylated starch, hydroxypropylated starch and the like are used. However, even by such a method of applying a surface treatment agent, the surface strength is not sufficiently improved, and in particular, it cannot sufficiently cope with the recent reduction in weight of newspapers and increase in the amount of filler used.

JP 2003-113592 A JP 2009-235664 A

  The present invention has been made based on the above-described circumstances, and an object of the present invention is to provide a newsprint having a high surface strength and excellent printing workability despite a high amount of filler and high opacity. To do.

The invention made to solve the above problems is
Newspaper paper provided with newspaper base paper, and surface treatment agent applied to both sides of the newspaper base paper,
The surface treatment agent contains oxidized starch and hydroxyethylated starch,
The content ratio of the oxidized starch and hydroxyethylated starch is from 1: 9 to 9: 1 on a mass basis,
The ash content is 5% or more and 20% or less.

  The newsprint uses a surface treatment agent to be applied to both sides of the newsprint, which contains a predetermined ratio of oxidized starch and hydroxyethylated starch. Starch does not penetrate into the base paper and forms a strong film on the surface. Therefore, the newsprint has a high surface strength and can suppress the generation of paper dust, and thus has excellent printing workability. Further, according to the newsprint, occurrence of nappari trouble during printing is also suppressed. By using the above two types of starch, the starch does not penetrate to the inside of the base paper, and the cause of forming a strong film on the surface is not clear, but the carboxyl group etc. of oxidized starch and the hydroxyl group of hydroxyethylated starch It is conceivable that the polymer becomes a polymer by bonding with and becomes difficult to penetrate into the inside. Furthermore, in addition to having high opacity because the ash content is high in the above range, the newsprint can suppress the penetration of the surface treatment agent by filling the voids of the fiber with a large amount of filler, The surface strength is increased. In addition, according to the newsprint, the surface treatment agent does not penetrate to the inside and a film is formed on the surface, so that voids inside the paper can be left, and blank paper opacity and printing opacity can be reduced. Can be increased.

  The B-type viscosity of the surface treatment agent is preferably 5 cps or more and 80 cps or less. According to the newsprint, by setting the viscosity of the surface treatment agent at the time of application to the above range, the applicability can be further improved, the penetration of starch into the paper is further reduced, and the surface strength is further increased. Can be increased.

  The newspaper may be internally added with a filler having a volume average particle size of 0.1 μm or more and 15 μm or less. According to the newspaper, by adding the filler having the above particle diameter, the opacity increases, the penetration of the surface sizing agent can be further suppressed, and the surface strength can be further increased. The reason why the penetration of the surface sizing agent can be further suppressed by adding such a fine filler is not certain, but the fine filler (inorganic substance) is a catalyst for the esterification reaction of the above two kinds of starches. It is thought that it is to fulfill a typical function.

  The filler is at least one selected from the group consisting of regenerated particles obtained from paper sludge as a main raw material and subjected to dehydration, heat treatment and pulverization steps, and silica composite regenerated particles obtained by coating the regenerated particles with silica. It may be a particle. According to the newspaper, by using such regenerated particles or silica composite regenerated particles as a filler, the surface strength can be further increased and the printing workability can be further improved.

Here, “ash content” is a measurement value based on “paper, paperboard and pulp-ash content test method—525 ° C. combustion method” described in JIS-P8251. “B-type viscosity” is a digital B-type viscometer (manufactured by Toki Sangyo Co., Ltd., model number: TVB-10M) No. It is a value measured at 60 rpm and 45 ° C. using the rotor No. 1. “Volume average particle diameter” refers to the volume average particle diameter (D ₅₀ ) in the particle size distribution measured by the laser diffraction scattering method.

  As described above, according to the newsprint of the present invention, the surface strength is high and the printing workability is excellent despite the high blending amount of filler and high opacity.

  Hereinafter, embodiments of the newsprint of the present invention will be described in detail.

  The newsprint of the present invention is provided with a newsprint, and a surface treatment agent is applied to both sides of the newsprint. First, the surface treatment agent that is a feature of the present invention will be described, and then other components will be described.

(Surface treatment agent)
The surface treatment agent contains oxidized starch and hydroxyethylated starch (HES), and the content ratio of the oxidized starch and hydroxyethylated starch is from 1: 9 to 9: 1 on a mass basis.

  The newsprint uses a surface treatment agent to be applied to both sides of the newsprint, which contains a predetermined ratio of oxidized starch and hydroxyethylated starch. Starch does not penetrate into the base paper and forms a strong film on the surface. Therefore, the newsprint has a high surface strength and can suppress the generation of paper dust, and thus has excellent printing workability. Further, according to the newsprint, occurrence of nappari trouble during printing is also suppressed.

  By using the above two types of starch, the starch does not penetrate to the inside of the base paper, and the cause of forming a strong film on the surface is not clear, but the carboxyl group etc. of oxidized starch and the hydroxyl group of hydroxyethylated starch It is conceivable that it becomes difficult to penetrate into the interior by being polymerized by bonding (cross-linking or the like) and crosslinking. In addition, it is considered that the mixing of the two types of starch results in an appropriate viscosity, and the esterification reduces the affinity between the starch and cellulose constituting the pulp fiber, making it difficult to penetrate. It is done. In addition, it is thought that the fall of the said viscosity is a cause of reaction of 2 types of starch. Furthermore, suppression of the occurrence of Nepari trouble in the newspaper is also considered to be caused by the decrease in the hydrophilicity of starch due to the esterification.

  In addition, according to the newsprint, the surface treatment agent does not penetrate into the interior as described above, and a void is left inside the paper by forming a film on the surface. According to the newsprint, this gap increases the degree of light scattering inside the paper, and as a result, the white paper opacity and the printing opacity can be increased.

  Examples of the oxidized starch include those in which a carboxyl group or the like has been introduced into the molecule by an oxidation reaction with sodium hypochlorite or the like. The mass average molecular weight of the oxidized starch is preferably 500,000 to 1,000,000. The hydroxyethylated starch preferably has a mass average molecular weight of 1.2 million to 2,000,000. By setting the molecular weights of the two types of starch within the above range, the viscosity of the surface treatment agent can be controlled within a suitable range, the coating property can be improved, and the penetration of starch into the paper can be further reduced. The mass average molecular weight is a numerical value measured using a gel permeation chromatography method (GPC method).

  When the mass average molecular weight of the oxidized starch and hydroxyethylated starch is less than the lower limit, the starch easily penetrates into the paper during coating, and as a result, the surface strength may not be sufficiently improved. On the other hand, when these mass average molecular weights exceed the above upper limit, the viscosity is increased and the applicability may be lowered.

  The content ratio of the oxidized starch and hydroxyethylated starch is from 1: 9 to 9: 1 on a mass basis, and preferably from 5: 5 to 7: 3. By setting the content ratio of the two types of starch within the above range, it can be prepared to have a suitable viscosity, and it is considered that the above esterification reaction and the like can proceed efficiently. Can be prevented from penetrating into the paper, and a strong film can be formed on the surface.

  The surface treatment agent may contain other starch, PVA (polyvinyl alcohol), polyacrylamide, antifoaming agent, water-resistant agent, surface sizing agent, preservative, etc., as appropriate, in addition to the two types of starch. it can. Among these, a surface sizing agent is preferably contained in order to improve sizing properties.

  As the surface sizing agent, known ones are used, and for example, styrene-based sizing agent, olefin-based sizing agent, alkyl ketene dimer, alkenyl succinic anhydride, rosin and the like can be used. Styrenic sizing agents are preferred from the viewpoint of compatibility with ink in rotary printing and the effect of preventing the filler from falling off. By using a styrene-based sizing agent as a surface sizing agent for starch having a content ratio of oxidized starch and hydroxyethylated starch of from 1: 9 to 9: 1 on a mass basis, the starch can be applied more uniformly and the surface strength can be increased. The styrenic sizing agent stays on the surface of the paper and the size effect is enhanced.

  The blending ratio of the styrenic sizing agent to the total starch of the oxidized starch and the hydroxyethylated starch is preferably 5 to 30 parts by mass of the styrenic sizing agent with respect to 100 parts by mass of starch as a solid content. When the styrenic size is less than 5 parts by mass, it is difficult to sufficiently improve the size and surface strength of the paper, and when it exceeds 30 parts by mass, the cost is increased and the opacity and ink drying properties are reduced. There is a fear.

  Examples of the styrene-based sizing agent include styrene acrylic acid copolymer, styrene (meth) acrylic acid copolymer (note that (meth) acrylic acid means “acrylic acid and / or methacrylic acid”), styrene. Examples include (meth) acrylic acid (meth) acrylic acid ester copolymers, styrene maleic acid copolymers, styrene maleic acid half ester copolymers, and styrene maleic acid ester copolymers.

  The B-type viscosity of the surface treatment agent is preferably 5 cps or more and 80 cps or less, and more preferably 10 cps or more and 40 cps or less. According to the newsprint, by setting the viscosity of the surface treatment agent at the time of application within the above range, the applicability can be further improved and the penetration of starch into the paper can be further reduced. When the viscosity of the surface treatment agent is less than the above lower limit, this surface treatment agent containing starch or the like is likely to penetrate into the inside of the paper at the time of coating, and as a result, it may be difficult to obtain newspaper paper with high surface strength. is there. On the other hand, if this concentration exceeds the above upper limit, workability during application may be reduced, or uniform application may be difficult.

As the coating amount of the surface treating agent, in order to sufficiently improve the surface strength of the paper, the dry weight per side on the front and back of the newspaper base paper is 0.1 to 2.0 g / m ² , and further 0.3 It is preferably applied in an amount of ˜1.5 g / m ² . If it is less than 0.1 g / m ² , it may be difficult to obtain a sufficient film with starch or the like, and sufficient paper surface strength may not be obtained. On the other hand, if it exceeds 2.0 g / m ² , a large amount of mist of a surface treatment agent such as starch is generated around the coating equipment, and the peripheral equipment is soiled, and there is a risk of paper breakage and paper defects due to the soiling. .

(Newspaper for newspaper)
The above-mentioned newspaper base paper is usually obtained by making a pulp slurry containing pulp and preferably a filler.

  As said pulp, a well-known thing can be used and used paper pulp, virgin pulp, or these combined things can be used suitably. 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 particularly preferable to use a mixture of 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, wastepaper pulp is generally used in newsprints because it is already 50% or more of wastepaper pulp and the content of virgin mechanical pulp and kraft pulp is low. Since it is once paper-made and used paper pulp by used paper processing, it is particularly preferable in that it has uniform properties and has almost constant properties.

  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 well-known pulps such as mechanical pulps such as thermomechanical pulp (TMP); pulps 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 newsprint, mechanical pulp (MP) having an effect of complementing the decrease in bulk due to the use of waste paper pulp is preferable, and thermomechanical pulp suitable for the adjustment of waste paper pulp obtained from waste paper ( TMP) is particularly preferred.

  The content of waste paper pulp in the raw material pulp is preferably 50% by mass or more, particularly preferably 80% by mass or more, and further 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. Conversely, the content of virgin pulp in the raw material pulp is preferably 10% by mass or more, and particularly preferably 20% by mass or more. If the content of the virgin pulp is less than the above range, it is difficult to adjust the waste paper pulp obtained from the waste paper, and the newspaper paper does not become bulky and has no waist, which may deteriorate the transportability and workability.

(Filler)
The filler is not particularly limited, and examples thereof include titanium dioxide, calcium carbonate, kaolin, talc, hydrated silicon, white carbon, regenerated particles, and silica composite regenerated particles. The method for producing regenerated particles and silica composite regenerated particles will be described in detail later.

  Among these fillers, it is preferable to use at least one kind of particles selected from the group consisting of regenerated particles and silica composite regenerated particles. According to the newspaper, by using such regenerated particles or silica composite regenerated particles as a filler, the surface strength can be further increased and the printing workability can be further improved. The reason why the surface strength is increased by using the regenerated particles and the silica composite regenerated particles is not clear, but the regenerated particles are a mixture formed of various oxides, so that any component can contain the above two kinds of starches. It is conceivable that, when a surface treatment agent is applied, such as the esterification reaction, the surface film-forming property is improved by this catalytic action. In addition, since these particles have an irregular shape and a porous shape, it is considered that this shape enhances the catalytic function.

  Moreover, the surface of the regenerated particles and silica-coated regenerated particles, particularly silica-coated regenerated particles, has a porous shape. Therefore, by using these fillers, the newspaper can exhibit an extremely high oil absorption function, and in addition, the opacity can be further increased due to the high light scattering property.

  The volume average particle size of the filler is preferably 0.1 μm to 15 μm, and more preferably 2 μm to 8 μm. According to the newspaper, by adding the filler having the above particle diameter, the opacity increases, the penetration of the surface sizing agent can be further suppressed, and the surface strength can be further increased. The reason why the penetration of the surface sizing agent can be further suppressed by adding such a fine filler is not certain, but as described above, the fine filler (inorganic substance) is an ester of the above two types of starch. It may be possible to fulfill the catalytic function of the chemical reaction.

  When the volume average particle diameter of the filler is less than the above lower limit, the yield is low, and as a result, the ash content becomes low and the opacity may not be improved. In addition, the voids of the pulp fiber cannot be sufficiently filled, and the starch is likely to permeate, and the surface strength may not be sufficiently increased. On the contrary, when the volume average particle diameter exceeds the upper limit, the entanglement between the pulp fibers may be weakened and the paper strength may be reduced, and the above-described catalytic function is not sufficiently exhibited, and the film forming property is weakened. The surface strength may not be sufficiently increased.

(Quality etc.)
The ash content of the newspaper is 5% or more and 20% or less, and more preferably 7% or more and 15% or less. In addition to having high opacity (blank paper opacity and printing opacity) because the ash content is high in the above range, the newsprint has a large amount of filler that fills the voids of the fiber, so The penetration can be suppressed, and as a result, the surface strength is increased.

  Therefore, according to the newspaper, despite the high filler content (high ash content), conversely, the high content of this filler is used to increase the surface strength, resulting in excellent Printing workability can be demonstrated.

The basis weight of the newspaper is measured in accordance with the “basis weight measurement method” described in JIS-P8124 from the viewpoint of weight reduction, for example, ensuring the paper quality strength in high-speed rotary printing, ensuring the printing opacity, It is preferably 38 g / m ² or more, more preferably 40 g / m ² or more, and from the viewpoint of weight reduction, the basis weight is preferably 48 g / m ² or less, more preferably 46 g / m ² or less. If the basis weight is less than the above lower limit, for example, it is difficult to ensure strength in a high-speed offset rotary printing press. If the basis weight exceeds the above upper limit, it will go against the recent weight saving and resource saving.

  The whiteness of the newspaper is in accordance with “Measuring method of paper, paperboard and pulp-ISO whiteness (diffuse blue light reflectance)” described in JIS-P8148 so as not to cause eye strain of subscribers. Measured to be 52% to 57%, more preferably 53% to 56%.

  The opacity of the newsprint is required to be high because it is difficult to see through. However, “Paper and paperboard—Opacity test method (paper backing)”-Diffusion described in JIS-P8149 The lower limit measured according to the “illumination method” is preferably 90%, particularly preferably 92%. Moreover, as an upper limit of opacity, 96% is preferable and 95% is especially preferable. If the opacity is less than the above lower limit, the show-through tends to occur. On the other hand, when the opacity exceeds the upper limit, the necessary filler is increased. As a result, the adhesion between the pulp fibers is lowered, and the strength of the newsprint is lowered.

  The printing opacity of the newspaper is required to be high because it is difficult to show through during printing, but 90% is the lower limit measured in accordance with the printing opacity test method described later. Preferably, 91% is particularly preferable. Moreover, as an upper limit of opacity, 95% is preferable and 94% is especially preferable. If the printing opacity is less than the above lower limit, show-through tends to occur. Conversely, if the printing opacity exceeds the above upper limit, the necessary fillers increase, resulting in a decrease in the adhesion between pulp fibers, the strength of the newsprint, or printing due to the loss of the filler from the paper surface. Not only the paper dust increases, but also dirt in the machine system in the manufacturing process increases and the operability deteriorates.

(Newspaper production method)
The newsprint can be manufactured by a known manufacturing method.

  First, a pulp slurry is prepared as described above, and paper is made to obtain a newspaper base paper. In this pulp slurry, in addition to the above-mentioned fillers, for example, starch, polyacrylamide, paper strength enhancers such as epichlorohydrin, rosin, alkyl ketene dimer, ASA (alkenyl succinic anhydride), internal sizing agents such as neutral rosin, A coagulant such as a sulfuric acid band or polyethyleneimine, and a coagulant such as polyacrylamide or a copolymer thereof can be contained.

  The surface treatment agent is applied to both sides of a newspaper base paper obtained by the paper making. For the application of the surface treatment agent, a coating device generally used in the papermaking field, such as 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, an air knife coater, etc. Can be used.

  The temperature of the newspaper base paper at the time of applying the surface treatment agent is preferably 35 ° C. or higher and 85 ° C. or lower, and more preferably 40 ° C. or higher and 75 ° C. or lower. By applying a surface treatment agent to both sides of such relatively high temperature newspaper base paper, when the surface treatment agent comes into contact with the newspaper base paper, a binding reaction between the two types of starch occurs, and so on. The penetration of internal starch is suppressed, and a thin and high-strength film can be formed on the surface. When the temperature of the newspaper base paper is less than the above lower limit, the starch is likely to penetrate into the inside, and the surface strength may not be sufficiently increased. On the other hand, when this temperature exceeds the upper limit, applicability is lowered and a uniform film may not be formed.

  After the surface treatment agent is applied and dried, generally, press finishing is performed by passing the paper through a calendar for the purpose of imparting printability (for example, high smoothness and high gloss). As the calendar device in this case, for example, various calenders such as a super calender, a gloss calender, a soft compact calender, or a combination of a drum and an elastic roll can be used as appropriate in an on-machine or off-machine specification.

(Production method of regenerated particles and silica composite regenerated particles)
Hereinafter, regarding the method for producing regenerated particles suitably used as a filler for the newsprint of the present invention, the method for producing silica composite regenerated particles and the silica coating step will be described in detail in the order of raw materials and dehydration, heat treatment and pulverization steps. . In addition, it is preferable to have a mixing | blending / slurry process between a heat treatment process and a grinding | pulverization process, and also other processes can be provided as needed.

(material)
As the raw material for the regenerated particles, papermaking sludge is used as the main raw material, and among the papermaking sludge, deinking floss is preferably used. The deinking floss refers to what is separated from the pulp fiber in the deinking process for removing ink adhering to the used paper in the used paper processing process for producing the used paper pulp. In the used paper pulp manufacturing process in papermaking, for the purpose of continuously producing used paper pulp of stable quality, the used paper is selected and selected, and used paper of a certain quality is used. For this reason, the types, ratios, and amounts of inorganic substances brought into the used paper pulp manufacturing process are basically constant. Moreover, even if the waste paper contains plastics such as vinyl and film that cause fluctuations in unburned materials, these foreign matters are removed at the stage before the deinking process for obtaining the deinking floss. Accordingly, the deinking floss is a raw material for producing regenerated particles having extremely stable quality as compared with papermaking sludge generated in other processes such as a factory drainage process and a papermaking raw material preparation process.

(Dehydration process)
The dehydration step is a step of removing moisture of a raw material such as deinking floss up to a predetermined ratio. For example, deinking floss separated from pulp fibers in a deinking process for producing waste paper pulp is subjected to various operations and dehydrated by a known dewatering facility.

  Examples of the dehydration step include the following steps. First, water is separated from the deinking floss by a screen as one dehydrating means and dehydrated. The deinking floss dehydrated to 70% to 90% in this screen is sent to another dehydrating means such as a screw press, and further dehydrated to a predetermined moisture content.

  The raw material after dehydration (deinking floss) is 60% or less, preferably 30% or more and less than 50%, more preferably 30% or more and 45% or less, and particularly preferably more than 30% and 40% or less.

  When the moisture content of the raw material after dehydration exceeds 60%, the processing temperature in the heat treatment process is lowered, energy loss for heating increases, and uneven combustion of the raw material is likely to occur, making it difficult to promote uniform combustion. Become. Further, the exhaust gas discharged has a large amount of moisture, which has the disadvantage that the efficiency of the recombustion treatment in the dioxin countermeasures is reduced and the load of the exhaust gas treatment equipment is increased. On the other hand, if the moisture content of the raw material after dehydration is as low as less than 30%, it is contrary to the reduction of dehydration energy.

  As described above, if the raw material (deinking floss) is dehydrated in a multi-stage process and abrupt dehydration is avoided, the outflow of inorganic substances can be suppressed and the deinking floss flocs do not become too hard. In the dehydration treatment, an auxiliary agent for improving the dehydration efficiency such as an aggregating agent for aggregating the deinking floss may be added, but it is preferable to use an aggregating agent that does not contain iron. When iron is contained, the whiteness of the regenerated particles may be reduced due to oxidation of iron.

  It is preferable in terms of production efficiency that the equipment for the dehydration process is adjacent to the equipment of other processes of the regenerated particles, but the equipment is provided in advance adjacent to the waste paper pulp manufacturing process to transport the dehydrated material. It is also possible to transport to a metering feeder by a transport means such as a truck or a belt conveyor, and to supply the heat treatment process from this metering feeder.

  The raw material after dehydration is a particle having an average particle diameter of 40 mm or less, preferably an average particle diameter of 3 mm to 30 mm, more preferably an average particle diameter of 5 mm to 20 mm by a pulverizer (or pulverizer) before being supplied to the heat treatment step. It is preferable to arrange the diameters, and it is preferable to arrange the particle diameters so that the ratio of the particle diameters of 50 mm or less is 70% by mass or more. If the average particle size is less than 3 mm, overcombustion tends to occur. Conversely, when the average particle diameter exceeds 40 mm, it becomes difficult to uniformly burn the raw material core.

  The average particle diameter and the ratio of the particle diameter in the dehydration step are values measured using a sample sufficiently dispersed by a stirring type disperser. In addition, the particle diameter in each heat processing process mentioned later is the value measured with the metal plate sieve based on JIS-Z8801-2: 2000.

(Heat treatment process)
The heat treatment step includes a first heat treatment step in which drying for further moisture removal of the dehydrated raw material and a first combustion at a relatively low temperature are performed in series, and the heat treatment product obtained in the first heat treatment step is again used. And a second heat treatment step for heat treatment (combustion) at a higher temperature than the first heat treatment step. By passing through the two-stage heat treatment step in which the temperature is raised in this way, over-combustion of the raw material can be suppressed, and thickening when the obtained regenerated particles are slurried can be suppressed. In addition, by performing the heat treatment at a relatively low temperature, it is possible to similarly suppress over-combustion of the raw material and suppress thickening when the obtained regenerated particles are slurried. Specifically, the upper limit of the heat treatment temperature is preferably 780 ° C, more preferably 750 ° C.

(First heat treatment step)
The raw material that has undergone the dehydration step is heat-treated as a first heat treatment step using, for example, an internal heat kiln furnace in which the main body is placed horizontally and rotates around the central axis.

  In this internal heat kiln furnace, hot air generated in the hot air generation furnace is sent from the outlet side so as to counter-flow with the raw material flow. An exhaust gas chamber is provided on one side of the internal heat kiln furnace, and an exhaust chamber is provided on the other side. Hot air is blown from the other side of the internal heat kiln furnace through the discharge chamber, and is charged from the other side to dry and burn the raw material sequentially transferred to the other side as the internal heat kiln furnace rotates. To do.

  In this way, in the first heat treatment step, the raw material is dried and burned gently from the supply port to the discharge port by drying and burning in the internal heat kiln furnace in which the main body is placed horizontally and rotates around the central axis. Can control the degree of combustion of raw materials with various properties such as agglomeration, hard and soft, and stable grain alignment. Can do. In addition, drying can be divided into separate steps and dried by, for example, a blow-up type dryer.

  The heat treatment temperature in the first heat treatment step (for example, the outlet temperature (hot air temperature) of the internal heat kiln furnace) is 300 ° C. or higher and lower than 600 ° C., preferably 400 ° C. or higher and lower than 550 ° C., more preferably 400 ° C. or higher and 500 ° C. or lower. Is preferred. In the first heat treatment step, it is preferable to heat-treat at a temperature in the above range for the purpose of slowly burning the combustible organic matter and suppressing the formation of residual carbon that is difficult to burn. When the temperature is excessively low, the organic matter is not sufficiently combusted. On the other hand, when the temperature is excessively high, overcombustion occurs, and calcium oxide is easily generated by decomposition of calcium carbonate. In addition, when the temperature is 600 ° C. or higher, drying / combustion proceeds locally faster than the alignment of dehydrated materials having various properties such as hard and soft, so that the particle surface and the interior of the particle are not. It becomes difficult to reduce the difference in the flammability and make it uniform.

  In the first heat treatment step, an easily combusted organic substance contained in the raw material is slowly burned, and in order to suppress the formation of residual carbon, the heat treatment is performed for 30 minutes to 90 minutes in the residence (heat treatment) time under the above conditions. Is preferred. If the heat treatment time is less than 30 minutes, sufficient combustion is not performed and the ratio of remaining carbon increases. On the other hand, when the heat treatment time exceeds 90 minutes, thermal decomposition of calcium carbonate occurs due to excessive combustion of the dehydrated product, and the obtained regenerated particles become extremely hard. In terms of organic combustion and production efficiency, heat treatment is preferably performed with a residence time of 40 minutes to 80 minutes. In order to ensure constant quality, it is preferable to perform heat treatment combustion with a residence time of 50 minutes to 70 minutes.

(Second heat treatment step)
The raw material which passed through the 1st heat treatment process is heat-processed using the external heat kiln furnace which has the external heat jacket which a main body turns sideways and rotates around a central axis as a 2nd heat treatment process. In this way, through the first and second heat treatment steps, the organic component in the raw material is burned and removed, and the inorganic substance can be discharged as a heat treatment product.

  In the second heat treatment step, in order to burn the residual organic matter that could not be burned in the first heat treatment step, for example, residual carbon, the heat treatment adjusted to a particle size smaller than the particle size of the raw material supplied in the first heat treatment step. It is preferable to use a product. The grain alignment of the heat-treated product after the first heat treatment step is preferably adjusted so as to be an average particle diameter of 10 mm or less, more preferably adjusted so as to be an average particle diameter of 1 to 8 mm, and an average particle diameter of 1 to It is particularly preferable to adjust to 5 mm. If the average particle diameter at the inlet of the external heat kiln in the second heat treatment step is less than 1 mm, there is a risk of overcombustion. If the average particle diameter exceeds 10 mm, the remaining carbon is difficult to burn, and combustion may not proceed to the core. There is a possibility that the whiteness of the regenerated particles may decrease.

  As the external heat source of the external heat kiln furnace, an electric heating type heat source that is easy to control the temperature in the external heat kiln furnace and easy to control the longitudinal temperature is suitable. Is preferred. By using electricity as an external heat source, the temperature in the furnace can be finely and uniformly controlled, and the degree of combustion of the heat-treated product having various properties such as formation of aggregates, hard and soft, Grain alignment can be performed stably. In addition, by providing a plurality of electric heaters in the flow direction of the furnace, the electric furnace can arbitrarily provide a temperature gradient, and the temperature of the heat-treated product can be maintained at a constant temperature for a certain period of time. Residual organic content in the heat-treated product after one heat treatment step, especially residual carbon, can be brought to zero as much as possible without causing decomposition of calcium carbonate in the second heat treatment step, for example, low wire wear compared to heavy calcium carbonate And high whiteness regenerated particles can be obtained.

  The heat treatment temperature in the second heat treatment step is higher than the first heat treatment temperature, preferably 550 ° C. to 780 ° C., more preferably 600 ° C. to 750 ° C. In the second heat treatment step, as described above, since it is necessary to burn the residual organic matter that has not been burned in the first heat treatment step, particularly the residual carbon, it is preferable to perform the heat treatment at a higher temperature than the first heat treatment step. If the heat treatment temperature is less than 550 ° C., there is a possibility that the residual organic matter cannot be burned sufficiently. If the heat treatment temperature exceeds 780 ° C., decarboxylation of calcium carbonate in the heat treatment proceeds and the particles become hard. There is a fear.

  The residence (heat treatment) time in the external heat kiln furnace as the second heat treatment step is preferably 60 minutes or more, more preferably 60 minutes to 240 minutes, particularly preferably 90 minutes to 150 minutes, and most preferably 120 minutes to 150 minutes. Minutes are desirable for complete combustion of the remaining carbon. In particular, the remaining carbon must be burnt slowly at a high temperature that does not cause the decomposition of calcium carbonate as much as possible. If the residence time is less than 60 minutes, the remaining carbon is burnt in a short time, If the residence time exceeds 240 minutes, the calcium carbonate may be decomposed. In addition, in the stable production of the heat-treated product, it is preferable that the residence time is 60 minutes or more, and in order to prevent overcombustion and secure productivity, the residence time is 240 minutes or less.

  The average particle diameter of the heat-treated product discharged from the external heat kiln furnace as the second heat treatment step is preferably adjusted to 10 mm or less, preferably 1 mm to 8 mm, more preferably 1 mm to 4 mm. This adjustment can be performed, for example, by passing the heat-treated product between two rotating rolls having a certain clearance.

  The heat-treated product that has undergone the second heat treatment step is preferably an agglomerate, for example, cooled by a cooler, sorted by a particle size sorter such as a vibration sieve, and temporarily stored in a combustion product silo. Then, after adjusting to the target particle diameter in the blending / slurry step and the pulverization step, the particles are used as reclaimed particles for application destinations such as fillers.

  In addition, although the case where the deinking floss was used as a raw material was illustrated above, the deinking floss was used as a raw material, and the raw material was appropriately mixed with other papermaking sludge such as paper sludge in the papermaking process. You can also.

(Formulation / slurry process)
The blending / slurrying step is a step of blending an acid and / or salt into the heat-treated product discharged from the second heat treatment step and suspending the heat-treated product in water to make a slurry.

  This heat-treated product is preferably pulverized after being suspended in water by using a mixer or the like in order to achieve effective pulverization in the subsequent pulverization step. In this case, the lower limit of the slurry concentration (mass ratio of the heat-treated product added to the whole slurry) is preferably 15%, and more preferably 20%. Further, the upper limit of the slurry concentration is preferably 50%, and more preferably 40%. When the slurry concentration is less than the above lower limit, when the finally obtained particles are made into a solid state, production efficiency decreases, for example, enormous energy is generated. On the other hand, if the slurry concentration exceeds the above upper limit, effective pulverization may be difficult in the subsequent pulverization step, and solidification and solidification may easily occur.

  The acid and / or salt can precipitate a calcium salt in the presence of calcium ions. According to the acid and / or salt, it reacts with calcium ions dissolved in the slurry due to calcium oxide and metakaolin generated by overcombustion, and precipitates calcium salt, thereby coexisting with calcium ions in the slurry. The reaction with silicate ions and aluminate ions can be suppressed, and the generation of a cured substance can be suppressed. As a result, by using this acid and / or salt, solidification and solidification of the slurry can be suppressed.

(Crushing process)
The pulverization step is a step in which regenerated particles are obtained by pulverizing the slurry obtained in the above-described step to obtain fine particles. In this pulverization step, a known pulverizer or the like can be used. Through this pulverization step, the resulting regenerated particles can be suitably used as a pigment for coating and a filler for internal addition by finely pulverizing the slurry to a necessary particle size.

(Other processes)
In the method for producing regenerated particles, a raw material aggregation process, a granulation process, a classification process between the processes, a carbonation process for carbonizing the slurry, and the like may be provided.

(Carbonation process)
The slurry of the regenerated particles thus obtained is alkaline with a pH of 12 or more, and can be used as a filler for internal addition as it is, but for example, it reacts with other papermaking chemicals and causes a decrease in quality. There is a fear. Therefore, in order to return the calcium oxide in the heat-treated product or the regenerated particles to calcium carbonate and reduce the pH, the carbon dioxide in the exhaust gas discharged in the first heat treatment combustion step or the second heat treatment step is used, for example, 7 It is more preferable to adjust the pH to ˜9.

  The carbonation step may be performed between the blending / slurry step and the pulverization step, simultaneously with the pulverization step, or after the pulverization step. The carbon dioxide blowing may be a blending / slurrying step as a blending of carbonic acid instead of or in addition to blending with other acids and / or salts.

  During carbonation, a gas blowing port is provided at the bottom of the reaction tank, and a pH meter for measuring the pH in the tank is provided, and batch processing is performed on the slurry in the tank until the pH of the slurry falls below a predetermined value. This can be done by blowing gas. Further, a gas blowing port is provided in a portion where the gears such as a VF pump mesh with each other, and pulverization and gas blowing can be simultaneously performed on the slurry.

As carbon dioxide for carbonation, carbon dioxide can be separated from exhaust gas using a carbon dioxide separator such as a PSA separator in the CO ₂ separation step. Moreover, exhaust gas can be used directly, or commercially available carbon dioxide gas can be used and used together.

  The blowing rate of carbon dioxide can be constant or variable, and in the case of being variable, it can be appropriately adjusted according to the transition of pH.

  In this embodiment, in order to further stabilize the quality of the regenerated particles, it is preferable to classify the particle diameter of the object to be processed uniformly in each process, and feed back coarse and fine particles to the previous process. By doing so, quality can be further stabilized.

  In addition, it is preferable to granulate the deinked floss (dehydrated product) that has been subjected to dehydration in the previous stage of the drying process, and it is more preferable to classify the granulated product to make the particle size uniform. The quality can be further stabilized by feeding back coarse and fine granulated particles to the previous process. In granulation, known granulation equipment can be used, but equipment such as a rotary type, a stirring type, and an extrusion type is suitable.

(Silica coating process)
After the regenerated particles obtained through the above steps are added and dispersed in an alkali silicate aqueous solution to prepare a slurry, a diluted solution of a mineral acid such as sulfuric acid, hydrochloric acid or nitric acid is added at a liquid temperature of 70 to 100 ° C. while stirring with heating. The silica sol is produced, and the pH of the final reaction solution is adjusted to the range of 8.0 to 11.0 to produce silica sol particles having a particle diameter of 10 to 20 nm on the surface of the regenerated particles. obtain.

Although the alkali silicate aqueous solution to be used is not particularly limited, a sodium silicate aqueous solution (No. 3 water glass) is desirable in view of availability. The concentration of the alkali silicate aqueous solution is preferably 3 to 10% by mass in terms of silicic acid content in the aqueous solution (in terms of SiO ₂ ). If it exceeds 10% by mass, white carbon is liable to be precipitated, which makes it difficult for silica to precipitate on the surface of the regenerated particles, and the opacity cannot be improved sufficiently. Moreover, even if it is less than 3 mass%, since silica hardly precipitates on the regenerated particle aggregate, it is not preferable.

  The liquid temperature is preferably 70 to 100 ° C, more preferably 80 to 100 ° C, and most preferably 90 to 100 ° C. If the liquid temperature is less than 70 ° C., the particle diameter does not grow, and it is not preferable because the particles may not become as large as several μm that can be used as a filler. By setting the liquid temperature to 70 ° C. or higher, preferably 80 ° C. or higher, most preferably 90 ° C. or higher, it is possible to grow to a suitable particle size.

  The pH of the final reaction solution is preferably 8.0 to 11.0, more preferably 8.3 to 10.0, and most preferably 8.5 to 9.0. Usually, in the production of silica particles (white carbon), in order to complete the reaction between hydrated silicic acid and mineral acid, a method of adding mineral acid until pH 5.5 to 7.0 is common, but the pH is 7 In the acidic region below, the calcium carbonate contained in the regenerated particles is likely to be decomposed into calcium hydroxide and carbonic acid, the particle diameter is reduced and the yield on paper is likely to be reduced, and sufficient opacity is obtained. It is not preferable because it is difficult. If the pH exceeds 11.0, silica is difficult to precipitate and the particles are not easily covered with silica, so that it is difficult to obtain sufficient opacity.

  EXAMPLES Hereinafter, although a synthesis example and an Example demonstrate this invention further in detail, this invention is not limited to these Examples.

  In addition, each measured value in a present Example is a value measured with the following method.

[Average particle size (unit: μm)]
A volume average particle diameter (D ₅₀ : μm) was measured using a laser diffraction particle size distribution measuring device [Microtrack / Nikkiso Co., Ltd.] (model number: MT-3300). 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.

[Viscosity (unit: cps)]
A digital B-type viscometer (manufactured by Toki Sangyo Co., Ltd., model number: TVB-10M) was used. Measurement was performed at 60 rpm and 45 ° C. using one rotor.

[Ash content (unit:%)]
It was measured according to “Paper, paperboard and pulp-ash content test method” described in JIS-P8251.

[Basis weight (unit: g / m ² )]
Measured according to JIS-P8124 (1998) “Paper and paperboard—basis weight measurement method”.

[Whiteness (Unit:%)]
Measured according to JIS-P8148 (2001) “Paper, paperboard and pulp—Measurement method of ISO whiteness (diffuse blue light reflectance)”.

[Opacity (Unit:%)]
Measured according to JIS-P8149 (2000) "Paper and paperboard-Opacity test method (backing of paper)-Diffuse illumination method".

[Printing opacity (unit:%)]
JAPAN TAPPI No. 45, using a measuring instrument ISO whiteness meter (manufactured by Suga Test Instruments Co., Ltd.).

[Paper dust piling]
Using an offset rotary printing press (model number: LITHOPIA BTO-4, manufactured by Mitsubishi Heavy Industries, Ltd.), printing 100,000 copies on both sides of newspaper with 50 rolls of paper, paper on the printed paper and blanket non-image part The presence or absence of powder generation and accumulation was 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.

[Nepparity (Blanket adhesive)]
Two samples obtained by cutting newspaper paper into a size of about 4 cm in width and about 6 cm in length were prepared and immersed in water for 10 seconds, and then these two samples were quickly brought into close contact with each other. This was passed through a calendar at a linear pressure of 100 kg / cm, dried at room temperature for 24 hours, and then manually peeled off two samples (T peel peel test imitation sensory test). Based on the evaluation.
(Evaluation criteria)
(Double-circle): It did not peel and it did not adhere | attach at all.
○: Although partly adhered, it could be easily peeled off.
(Triangle | delta): There existed a part which has adhere | attached and was hard to peel.
X: Adhered as a whole, and fluffing of fibers from the adhesion surface was observed at the time of peeling.

(Production of regenerated particles and silica composite regenerated particles)
A deinking floss was used as a raw material, and the dehydration step was performed so that the moisture content was 45 mass%, the average particle size was 10 mm, and the proportion of particles of 50 mm or less was 90 mass%. This dehydrated product was washed with shower water, and the first heat treatment step and then the second heat treatment step were performed under the following conditions to obtain a heat treatment product.
First heat treatment process conditions Combustion type: Internal heat kiln Combustion temperature: 500 ° C
Oxygen concentration: 10%
Residence time: 50 minutes Second heat treatment process conditions Combustion type: Combined use of external and internal heat kilns Average particle diameter at inlet: 5 mm
Combustion temperature: 700 ° C
Oxygen concentration: 14%
Residence time: 140 minutes Average particle diameter at outlet: 5 mm

To 100 parts by mass of the obtained heat-treated product, 0.3 parts by mass of calcium sulfate dihydrate is added as a blending / slurry step, and the additive is suspended in water to obtain a concentration (total slurry). A mass of 35% by mass of a heat-treated product with respect to mass was obtained and pulverized with a pulverizer. This pulverized product was classified to obtain regenerated particles having a volume average particle size shown in Table 1.

  The regenerated particles (volume average particle diameter 2 μm) are used as slurry solutions (slurry concentration 20% by mass), 38% by mass sodium silicate solution (No. 3 water glass), which is an alkali silicate aqueous solution, and the slurry solution (slurry concentration 20% by mass). %) Is mixed so that the solid content ratio of the regenerated particles and the alkali silicate is 100: 5, further diluted water is added, and the slurry composed of the alkali silicate and the regenerated particles is reacted at a reaction start concentration (slurry concentration 10% by mass). After the preparation, the mixture was heated and stirred to adjust the slurry liquid temperature to 55 ° C. The pH at the start of the reaction was 10.7. Next, dilute sulfuric acid (7N) was added as a mineral acid over 22 minutes while stirring until the alkali silicate neutralization rate became 33%, and a primary reaction was performed. Further, the slurry was heated and stirred until the liquid temperature of the slurry reached 93 ° C. and then held for 10 minutes. Thereafter, dilute sulfuric acid (7N) was added over 45 minutes until the pH reached 8.5, whereby silica composite regenerated particles of Example 1 were obtained. The obtained silica composite regenerated particles had a volume average particle size of 5 μm. While following the above measures, the solid content ratio between the regenerated particles and the alkali silicate, the concentration of the regenerated particles and the alkali silicate at the start of the reaction, the alkali silicate neutralization rate in the primary reaction, the reaction end pH, the addition rate of dilute sulfuric acid The silica composite regenerated particles having the volume average particle diameters shown in Table 1 were obtained by appropriately changing the amount and amount.

Example 1
80% by mass of disaggregated / deinked waste paper pulp (DIP) and 20% by mass of thermomechanical pulp (TMP) were added, and the freeness was 120 mLC. S. A pulp slurry adjusted to F (based on JIS-P8121) was obtained. To this pulp slurry, silica composite regenerated particles (average volume particle diameter 5.0 μm) are added so that the ash content becomes the value shown in Table 1 (13%), and after adjusting the pH to 6-7 with a sulfuric acid band, 0.07 parts by mass of a flocculant (Himo Rock ND270 manufactured by Hymo Co.) and 0.05 parts by mass of a coagulant (Himax SC 924 manufactured by Hymo Co.) are added per 100 parts by mass of the absolutely dry pulp, and the basis weight is measured with a twin wire paper machine. A newspaper base paper of 42 g / m ² was made.

Furthermore, as a surface treatment agent, a starch solution in which 90 parts by mass of oxidized starch (mass average molecular weight of 700,000 manufactured by Nippon Food Processing Co., Ltd.) and 10 parts by mass of hydroxyethylated starch (HES: mass average molecular weight of 150,000 manufactured by Penford) was mixed. A styrene-based sizing agent (“SS2712” manufactured by Seiko PMC Co., Ltd.) was blended in a solid content of 15 parts by mass of styrene-based sizing agent with respect to 100 parts by mass of starch (solid content concentration 6%, B-type viscosity 22 cps). This surface treatment agent was applied to both sides of the above-mentioned newspaper base paper having a surface temperature of 50 ° C. in a dry mass of 1.2 g / m ² to obtain the newspaper of Example 1.

(Examples 2 to 18 and Comparative Examples 1 to 3)
Example 2 was carried out in the same manner as in Example 1 except that the type of filler, the particle size of the filler, the mixing ratio of the two types of starch, the amount of ash, and the type of surface sizing agent were changed as shown in Table 1. To 18 and Comparative Examples 1 to 3 were obtained. However, in Example 17 and Example 18, the concentration of the surface treatment agent was adjusted so that the B-type viscosity shown in the table was adjusted.

  In Table 1, the regenerated particles and the silica-coated regenerated particles were obtained by the above production method. In Example 10 and Comparative Example 3, “Tama Pearl TP-121-6S” manufactured by Okutama Kogyo Co., Ltd. was used as calcium carbonate. Was used. In Example 11, as a calcium carbonate, “Tama Pearl TP-121-6S (volume average particle diameter 1.8 μm)” manufactured by Okutama Kogyo Co., Ltd. was used as a raw material and pulverized to have a volume particle diameter shown in Table 1 with a wet pulverizer. What was done was used. In Example 12, “SS2550” manufactured by Seiko PMC was used as the olefin sizing agent.

(Evaluation)
About each obtained newspaper paper, the ash content, whiteness, opacity, printing opacity, paper dust piling, and Nepari property were evaluated by the above method. The evaluation results are shown in Table 1.

  As shown in Table 1 above, it can be seen that the newsprint of the present invention is highly evaluated with respect to paper dust piling and Nepari property, and is excellent in printing workability. Furthermore, the newsprint of the present invention is also excellent in whiteness, opacity and printing opacity.

  The newsprint of the present invention is excellent in printing workability and can be suitably used for offset rotary printing and the like.

Claims (4)

Newspaper paper provided with newspaper base paper, and surface treatment agent applied to both sides of the newspaper base paper,
The surface treatment agent contains oxidized starch and hydroxyethylated starch,
The content ratio of the oxidized starch and hydroxyethylated starch is from 1: 9 to 9: 1 on a mass basis,
Newspaper with ash content of 5% or more and 20% or less.   The newsprint according to claim 1, wherein the surface treatment agent has a B-type viscosity of 5 cps to 80 cps.   The newsprint according to claim 1 or 2, wherein a filler having a volume average particle diameter of 0.1 µm to 15 µm is internally added. The filler is at least one selected from the group consisting of regenerated particles obtained from paper sludge as a main raw material and subjected to dehydration, heat treatment and pulverization steps, and silica composite regenerated particles obtained by coating the regenerated particles with silica. The newsprint according to claim 3, wherein the newsprint is a particle.