JP2003119695A - Printing coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printing coated paper which uses a recycled pigment recovered from papermaking sludge or the like and has high opacity and excellent print through resistance. SOLUTION: This printing coated paper produced by disposing a coating layer consisting mainly of a pigment and an adhesive on at least one side of base paper is characterized by using as the pigment a recycled pigment which is produced by carbonizing a mixture of organic substances with white inorganic particles and then subjecting the obtained carbonization product to a whitening treatment and has a specific surface area of 15 to 30 m<2> /g by BET method and a whiteness degree (according to JIS Z8722) of 60 to 90%. The recycled pigment is preferably pulverized to give a median diameter of 0.1 to 5 μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated paper for printing containing a recycled pigment made of waste as a raw material in a coating layer, and more specifically to a mixture containing organic matter such as papermaking sludge and white inorganic particles. The present invention relates to a coated paper for printing, which uses a recycled pigment having a high whiteness, has a high opacity, and is excellent in print strikethrough.

[0002]

2. Description of the Related Art White inorganic particles are a pesticide spreading agent, extender,
Modified pigments for printing inks, reinforcing agents for rubbers, fillers for plastics (molded products, films, fibers, etc.), modifiers,
It is also used as an internal filler and a coating pigment in the paper industry. Here, a usage example in the paper manufacturing industry in which the amount of kaolin or calcium carbonate used as the white inorganic particles is the largest will be described as a typical example.

Generally, in order to improve optical properties such as whiteness and opacity of paper, smoothness, etc., white inorganic particles as an internal filler are added to a paper material containing pulp as a main component. Is done. In addition, a pigment coating layer containing white inorganic particles and an adhesive as a main component is widely provided on paper (base paper) mainly for the purpose of improving printability.

Examples of white inorganic particles for papermaking used for such internal addition or coating include kaolin, calcined kaolin, calcium carbonate, zinc oxide, aluminum hydroxide, zinc sulfide, titanium dioxide, calcium sulfate, and sulfurous acid. Calcium, barium sulfate, satin white, talc,
An inorganic pigment (filler) such as silica is mainly used, and if necessary, one or more organic pigments called plastic pigments are appropriately mixed and used.

On the other hand, when recycling pulp from waste paper,
Depending on the required pulp quality and the quality of used paper materials, used paper is processed by combining processes such as disaggregation, beating, soaking, washing, flotation, and bleaching. In each process, it is diluted or dehydrated to the optimum concentration, but the squeezed liquid dehydrated in each process is called white water, which contains fine fibers derived from used paper, the printing ink attached to them, and the above white color. Contains inorganic particles.

Also in the papermaking process, fine fiber components such as pulp in the paper material, organic substances mainly composed of adhesives such as starch and synthetic adhesives and a part of the inorganic substances mainly composed of the above white inorganic particles are contained. It passes through the papermaking wire and flows out into white water. However, if white water containing a mixture of these organic substances and white inorganic particles is reused as it is as dilution water for pulp, the bulk and paper strength of the produced paper may be inferior. Therefore, white water is separated into solid content and clarified water by a solid content separation device utilizing precipitation or flotation, and the clarified water is used as dilution water for pulp, and the solid content is dehydrated by a centrifuge or dehydrator. After that, it has been disposed of. Further, when discharging white water or the like generated in the step of regenerating pulp from waste paper or the paper making step as waste water, biological treatment such as activated sludge treatment is generally performed. Excess sludge generated by the final biological treatment of solids and wastewater separated and collected by such wastewater treatment of white water and industrial wastewater is generally called papermaking sludge (hereinafter simply referred to as sludge).

[0007] In recent years, as the utilization rate of used paper has increased, the amount of sludge derived from the deinking process of used paper has increased. inside that,
Since waste newspaper and fine waste paper contain a small amount of inorganic substances (inorganic filler) in the waste paper, the amount of sludge generated is relatively small, and therefore the utilization rate of such waste paper is high. On the other hand, pigment-coated flyers and magazine waste paper contain a large amount of inorganic substances contained in the waste paper, and as a result, the amount of sludge generated increases, which is one of the reasons that the utilization rate of waste magazine paper is lower than that of newspaper wastepaper and high-quality wastepaper. It is a cause. In the future, in order to further promote the utilization of waste paper, it is necessary to improve the utilization rate of magazine waste paper. However, if the utilization rate increases, a new problem arises in that the amount of sludge generated increases.

Therefore, in order to cope with the large amount of sludge generation, sludge separated and collected from wastewater has been conventionally disposed of in landfill as it is after dehydration, whereas in recent years, it has been fluidized bed furnace or stoker furnace. At the same time, the organic matter in the sludge is burned in the incinerator to recover energy and at the same time, the volume of the sludge is reduced.

Combustion of sludge in an incinerator makes it possible to effectively extract and recover organic substances such as fibers, which have not been used conventionally and are discarded, as energy, but since sludge contains a large amount of inorganic substances, it can be burned after incineration. Has a problem that a large amount of residue (ash) remains. At present, some of the incinerated ash is mixed with cement and is also used as a soil conditioner, but most of it is landfilled as industrial waste. Therefore, if not only the organic matter recovered as energy by incineration but also the inorganic matter remaining as incineration ash can be reused as white inorganic particles for papermaking (filler for internal addition, pigment for coating), landfill disposal is required. It is thought that not only will the environmental load be reduced, but it will also lead to an improvement in the utilization rate of used magazine paper, which is currently low in utilization rate.

However, the whiteness of the incinerated ash becomes low depending on the state of combustion, or inorganic matter (incinerated ash)
However, there is a problem in that the particle size becomes uneven and the particle size becomes large, and it cannot be used as a filler or pigment for papermaking as it is. Under such circumstances, JP-A-10-0
In Japanese Patent No. 29818 and Japanese Patent Laid-Open No. 10-505055, it is proposed that ash remaining after burning organic matter in sludge in the presence of oxygen is re-supplied to a firing furnace to improve whiteness.

[0011]

There is an urgent need to reduce industrial waste due to the necessity of environmental protection, and also recycling of waste is required from the viewpoint of effective use of resources. Therefore, the present inventors collect an incineration residue (incineration ash) obtained by burning sludge, which is a mixture of an organic substance and an inorganic substance, discharged from a paper manufacturing process at a high temperature from an incinerator, and use it as a pigment for coated paper for printing. I tried to reuse it.

However, the method described in the above publication is to recover the incineration residue (ash) burned in the first stage heat treatment and improve the whiteness in the second stage firing furnace.
Since the ash obtained by the method of treating the first stage by combustion has a non-uniform whiteness, it was found that it is difficult to perform uniform firing in the second stage. As a result, it has been found that there is a drawback that the whiteness of the coated paper is reduced.

Further, it was found that the obtained incinerated ash changed into a form different from the filler or pigment itself usually contained in paper in chemical and physical properties. As a result, it has been found that the roll surface and the cutter blade are heavily worn at the time of manufacturing and processing the coated paper, which has a problem to be solved in manufacturing the coated paper.

An object of the present invention is to recover an inorganic substance, which has been conventionally discarded because it adversely affects the production of coated paper, from sludge as a recycled pigment capable of reducing adverse effects on the production of coated paper, and to apply it to a printing coating. The purpose is to propose a method that can be effectively used as a pigment for coating paper. More specifically, it is intended to provide a coated paper for printing which has a high opacity and is excellent in print strikethrough by treating the surface of the raw paper with a coating liquid containing such a recycled pigment.

[0015]

The coated paper for printing of the present invention is a coated paper for printing in which a coating layer containing a pigment and an adhesive as a main component is provided on at least one side of a base paper, A regenerated pigment produced by carbonizing a mixture of an organic substance and white inorganic particles, and then whitening the carbonized product obtained by the carbonization treatment, which has a specific surface area of 15 to 15 according to the BET method.
30m ² / g and whiteness (according to JIS Z8722)
Of 60 to 90% is contained in the recycled pigment.

The regenerated pigment is carbonized at a temperature of 1000 ° C. or lower at a temperature of 1000 ° C. or lower under a poor oxygen condition in which the presence of an oxygen-containing gas is restricted, and then a carbonized product obtained by the carbonization treatment is carried out. Temperature 450 ℃ ~ 10
A pigment produced by a whitening treatment step of decarbonizing in the presence of an oxygen-containing gas controlled to be oxidized in the range of 00 ° C. is a pigment having a well-balanced whiteness and opacity, which is preferable. In addition, when the regenerated pigment is used after being pulverized to have a median diameter of 0.1 to 5 μm,
It is preferable because the abrasion of the roll surface, the cutter blade and the like in the manufacturing process and the processing process of the coated paper for printing is further improved.
Furthermore, the whiteness of the base paper (based on ISO2470) and the whiteness of all the pigments constituting the coating layer containing the recycled pigment (JISZ
It is preferable that the absolute value of the difference from the above (according to 8722) is 10 points or less because a coated paper for printing without unevenness in whiteness can be obtained.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method of recycling pigments suitable for use in the coated paper of the present invention from sludge will be described. (Raw material) It demonstrates using the flow shown in FIG. In the present invention, the papermaking sludge 51 is used as a raw material for the recycled pigment. Papermaking sludge is a mixture of organic substances and white inorganic particles contained in dewatered white water called squeezed liquid in the used paper pulp manufacturing process and the papermaking process. More specifically, removal of contaminants in the used paper processing step, those generated during the deinking process and cleaning process, those generated during the cleaning process in the pulping process, and organic substances that flowed through the wire during papermaking into white water. And a mixture containing white inorganic particles can be used. In this embodiment, by collecting sludge from the white water in the disaggregation step, which is a step prior to the deinking step in the used paper recycling step, the load of deinking processing, bleaching processing, and cleaning processing in the used paper recycling step is reduced, In addition to the reduction of treatment cost, the load of wastewater treatment can be reduced, which is preferable.

In particular, in the used paper recycling step, a large amount of white inorganic particles derived from the used paper raw material flows out into white water, and the white water can be efficiently collected by coagulating the white water. For example, water can be obtained from a normal waste paper pulp manufacturing process, and if it is a disaggregation treatment, water squeezing from any conventionally known low-concentration pulper or high-concentration pulper can be used. Any known method can be used for the deinking treatment of waste paper, and water squeezing from a washing machine in each step can also be used. Further, in the case of white water obtained from a waste paper material having low whiteness, it is preferable to remove the ink particles from the white water by a flotation treatment of white water.

Further, in the present invention, sludge generated from sewage or industrial wastewater can be used as a raw material for the recycled pigment. Since sewage and industrial wastewater contain solids, they are settled and separated in a clarifier or coagulation settling tank before being discharged. At this time, the solid content contained in the wastewater as waste is recovered as sludge.

Apart from sludge, RPF (Reused Paper & Pl) mainly composed of low-grade waste paper which is difficult to reuse as a papermaking material and plastic accompanying it
Astic Fuel) can also be used as a raw material. In the present invention relating to use in coated paper for printing, since sludge derived from a papermaking material is a preferable raw material, an example using a papermaking sludge derived from a papermaking material will be described below. In this embodiment, by heat-treating the sludge, the recycled pigment suitable for manufacturing coated paper can be separated from the organic matter and recovered.

The iron content (Fe) in the sludge
Is 5.0% by weight or less, preferably 3.0 in terms of solid content.
It is preferably not more than mass%. Sludge containing a large amount of iron causes a problem that the whiteness is not sufficiently high. As a method of reducing the iron content, for example, it is preferable to use a coagulant that does not contain iron as a coagulant used for solid content separation in a paper mill wastewater treatment process. Furthermore, it is possible to install a magnet or the like in the classifier to remove iron pieces such as wires and nails that are mixed in the sludge, or to devise a method that does not mix them. In addition to this, it is preferable to remove foreign matters and coarse sintered mass as necessary. These foreign matter removing treatments are preferably installed between the treatment steps such as carbonization, decarbonization whitening, and crushing so that they can be efficiently removed according to the form of the sludge and the object to be removed. It is more preferable to remove it in the step.

It is also possible to granulate the sludge before heat treatment. By this granulation treatment, fine particles are integrated, the fine particles can be prevented from scattering, and the yield after heat treatment can be improved. Further, the variation in size is reduced, the heat treatment efficiency is increased, the organic substances are efficiently decomposed by heat, and the equipment can be downsized. Although the sludge in a water-containing state can be granulated by a tumbling granulation method, a stirring granulation method, or the like, a method of compression-molding a dried sludge is preferable because heat energy can be saved by heat treatment.

As a dry granulation method, it is preferable to use a compression molding machine such as a briquette machine or a roller compactor. These compression molding machines can perform compression molding by forcibly pushing sludge between two pressurized rolls with a screw and rotating the rolls.

(Carbonization Step) In the present invention, when the recycled pigment is produced from the sludge, the sludge passes through the carbonization step 52, whereby dry distillation gas is generated by thermal decomposition, resulting in high bulk and high specific surface area. It has been found that a pigment suitable as a coating pigment can be recovered. More specifically, the specific surface area of the carbide obtained after carbonizing sludge by the BET method is 15 m ² / g or more, preferably 20 m ²
/ G or more, and then treated so as to have a specific surface area of 15 to 30 m ² / g by the BET method after whitening treatment and slurrying and crushing, to give a recycled pigment having opacity preferable for coated paper for printing. Can be manufactured. The recycled pigment B
If the ET specific surface area is less than 15 m ² / g, the pigment becomes inferior in opacity, while if it exceeds 30 m ² / g, an adhesive is used to maintain the printing surface strength. It is not economically preferable because the amount increases.

As a result, the coated paper obtained according to the present invention is a printing paper having a bulky coating layer, a high scattering surface area and a high opacity. By passing through the carbonization process described below, the specific surface area of the carbide can be set to 15 m ² / g or more, preferably 20 m ² / g or more.

In the carbonization process, sludge is dried and carbonized by thermal decomposition. By recovering the white inorganic particles contained in the sludge through the carbonization treatment step and the whitening treatment step, the whiteness is high and the thermal transformation of the inorganic particles can be reduced as compared with the conventional incineration treatment. As a result,
It is possible to recover a recycled pigment that is preferable for paper production, in which abrasion of the roll surface and the cutter blade during production of coated paper and during processing is suppressed.

The solid content concentration in the sludge is usually 5 to 60% by weight because it depends on the capacity of the dehydrator. for that reason,
It is preferable to dry the hydrous sludge in the first half of the carbonization process. Pyrolysis can be efficiently performed by drying the sludge. Although it is possible to carry out carbonization treatment without distinguishing between drying and thermal decomposition of sludge, it is more preferable to provide separate temperature zones. That is, in the carbonization treatment of sludge, the drying and pyrolysis temperatures of organic substances are different, so that the sludge can be efficiently carbonized by providing the heating zones in two or more stages.

In the first half of the carbonization step, the water content in the sludge is evaporated at an atmospheric temperature of 400 ° C. or below, and in the latter half of the thermal decomposition, 400 ° C. to 1000 ° C., preferably 4 ° C.
By carrying out in the range of 50 ° C. to 700 ° C., the specific surface area of the carbide can be set to 15 m ² / g or more, preferably 20 m ² / g or more, and a recycled pigment suitable for coated paper production can be easily obtained. Therefore, it is preferable.

By the way, when the temperature in the furnace is lower than 400 ° C. due to the thermal decomposition in the latter half after the evaporation of water, the carbonization time becomes long,
At a high temperature of more than 1000 ° C., the melting and sintering of the white inorganic particles proceeds, making it difficult to finely pulverize after incineration, and it becomes difficult to recover a bulky recycled pigment. The carbonization time should be taken into consideration from the form, amount, water content, organic matter amount, economic effect, and environment of sludge, but it is generally preferably about 30 minutes to 2 hours.

In the carbonization process, if oxygen is present, the organic matter is burned along with the burning of the volatile matter contained in the sludge. As a result, the combustion temperature of the waste rises above the ambient temperature in the furnace due to the combustion of organic matter, causing undesired thermal modification of the pigment contained in the sludge, making it difficult to recover a bulky recycled pigment. turn into. Therefore, in the carbonization process, it is preferable to prevent the temperature increase above the atmospheric temperature in the furnace due to ignition of sludge by limiting the inflow of oxygen-containing gas (air). When the sludge is charged, it is preferable that the charging port has a minimum necessary size so that oxygen is not entrained in the sludge as much as possible. The oxygen-containing gas (air) that accompanies the sludge may exist in the furnace, but it is preferable to quickly replace it with water vapor or volatile components (carbon monoxide, hydrogen gas) generated from the sludge. Oxygen concentration in the furnace is 1 vo
It is more preferable that the oxygen content is 1% or less, and oxygen is substantially absent in the furnace.

As a method for heating the sludge, electric heating can be used, but heating with combustion gas of kerosene or heavy oil is economically preferable. It is possible to heat the sludge directly with combustion gas, but oxygen (air) contained in hot air
Since the sludge comes into contact with the sludge and the sludge ignites and burns, it is preferable to provide the partition wall so that the sludge does not come into direct contact with the hot air. Therefore, as equipment for carbonizing sludge, it is preferable to use a closed chamber in which the inflow of air is restricted. That is, it is more preferable that the carbonization device is a double structure indirect heating furnace including a closed sludge carbonization chamber and a heating chamber for heating the carbonization chamber.

As a heating method in carbonization, the sludge can be heated and dried by blowing combustion gas into the heating chamber. As the combustion gas, the combustion gas discharged from the existing incineration facility can be used. Examples of the incineration facility include a grate system (stoker furnace), a spray floating system, a material stirring system, a hot air combustion system, and the like. Of course, it is possible to directly heat the sludge heating chamber by providing a burner in the indirect heating chamber, and it is also possible to generate combustion gas by installing the burner outside the indirect heating furnace. .

By heating the dried sludge after drying the sludge, organic substances in the sludge are thermally decomposed. At this time, since a flammable gas such as carbon monoxide, methane, or ethane is generated, a bulky recycled pigment can be recovered. Further, since oxygen is not substantially contained in the furnace, it is possible to suppress combustion of organic substances. Combustible gas can be sucked into the hot air generator to serve as a heat source for sludge drying and carbonization.

(Whitening Treatment Step) Next, the whitening treatment step 53
The whitening is performed by decarbonizing the carbide. In the whitening treatment step by decarbonization, carbon derived from an organic substance contained in the carbide is oxidized and decarbonized to be whitened, and a regenerated pigment is recovered. Note that this process is also called a firing process.

Finally, the carbonized material is decarbonized, and the whiteness of the recycled pigment (according to JIS Z8722) is set to 60% to 90%, preferably 70 to 85%, so that the recycled pigment suitable for coated paper for printing is obtained. Can be manufactured. It should be noted that, depending on the type of white inorganic particles contained in the sludge, at a low temperature (700 ° C or lower) so that the white inorganic particles do not undergo thermal transformation.
It is possible to raise the whiteness to 90% by carrying out whitening treatment for a long time, but it is preferable to keep the whiteness to 85% in consideration of the scale of the apparatus, fuel cost and the like. In the present invention, the whiteness of the base paper used (in accordance with ISO2470) and the whiteness of all the pigments constituting the coating layer containing the recycled pigment (JISZ8
It is preferable to perform baking so that the absolute value of the difference from the above (in accordance with 722) is 10 points or less, because a coated paper for printing with less unevenness in whiteness can be obtained.

On the other hand, the higher the whiteness of the pigment particles constituting the coating layer, the lower the opacity of the coated paper, and the lower the whiteness, the higher the opacity of the coated paper. this is,
This is because it is affected by the absorption coefficient of the pigment. In the method that combines the carbonization treatment step and the whitening treatment step, a pigment with a large specific surface area can be obtained by carbonization, and by controlling the decarbonization rate in the whitening treatment step, the whiteness suitable for the coating pigment can be obtained. The advantage is that a recycled pigment having opacity can be produced. That is, the regenerated pigment with high opacity, which has been removed so as to partially leave the black carbide with high absorption coefficient, can be recovered in the whitening treatment step. At this time, the whiteness is preferably in the range of 78 to 83%.

By adjusting the atmospheric temperature and the treatment time of the white bottom treatment furnace, it is possible to adjust the residual carbon rate derived from any organic substance. When the whitening treatment temperature is 600 ° C. or lower, the burning rate of carbon and oxygen is low, so that the whiteness is low but the residual carbon ratio can be increased. On the contrary, by setting the treatment temperature to 650 ° C. or higher, preferably 700 ° C. or higher, a regenerated pigment having a high whiteness and a very low residual carbon rate can be obtained. By controlling the temperature of the whitening treatment as described above, the whiteness and the residual carbon ratio of the recycled pigment obtained in the present invention can be arbitrarily controlled according to the quality of paper.

Since the combustible gas having a large calorific value is already volatilized in the carbonization process in the first stage, in the whitening process, it is possible to suppress the combustion above the temperature in the furnace due to the combustion of the volatile content. As a result, it is possible to prevent undesired thermal denaturation of the white inorganic particles contained in the sludge due to the combustion of the organic matter. Therefore, in the whitening treatment step after the carbonization step, it becomes possible to sufficiently supply oxygen (air) necessary for oxidizing the carbide. This state is called oxygen rich state. After all, the white inorganic particles contained in the sludge can be recovered as the regenerated pigment under suitable conditions by combining the carbonization step and the whitening treatment step in the former stage.

In the whitening treatment step of decarbonizing the carbide, the whiteness of the regenerated pigment can be efficiently improved by heating the whitening chamber to a temperature in the range of 450 ° C to 1000 ° C. By the way, the whitening temperature is 4
If the temperature is lower than 50 ° C., the treatment time becomes long, and if the temperature is higher than 1000 ° C., the melting and sintering of the inorganic particles proceed, which makes it difficult to finely pulverize the regenerated pigment. Is not preferred. The treatment time should be taken into consideration not only in the form, amount, water content, and carbon content of carbides, but also in consideration of the economic effect and the environment.
Minutes to 2 hours is preferable.

In the whitening treatment step, rapid heating of the carbides is not preferable because melting and sintering of the inorganic particles proceed, carbon molecules are incorporated into the white inorganic particles, and whitening becomes difficult. It is possible to maintain a single temperature zone in the furnace,
In order to prevent rapid heating of the carbide, it is more preferable to perform the whitening treatment in a temperature range of two or more stages. In the whitening process, for example, 450 ° C to 600 ° C and 600 ° C to 100
It is more preferable to go through two or more heating zones such as 0 ° C. It is preferable to perform decarbonization in the latter stage of the heat treatment of two or more stages so that the temperature of the object to be treated does not rise above the ambient temperature. At this time, it is more preferable to control the temperature of the object to be treated itself. However, since it is difficult to measure the local temperature change of the object to be processed, a temperature sensor is installed in the whitening chamber and an oxygen-containing gas (air) is supplied so that the atmospheric temperature of the whitening chamber becomes 800 ° C or lower. However, it is preferable to control so that the temperature of the carbide itself does not suddenly rise due to self-combustion of the carbide.

When the whitening treatment is carried out in a temperature range where calcium carbonate is not decomposed, sludge-derived calcium carbonate is mixed in the depigmented regenerated pigment. Therefore, the residual carbon ratio in the regenerated pigment may be a high value even after the whitening treatment. The residual carbon ratio derived from organic matter was calculated by the elemental analysis after the calcium carbonate residual ratio was estimated from the calcium carbonate content ratio estimated from the amount of calcium contained in the raw material sludge and the calcium carbonate decomposition ratio estimated by X-ray diffraction after whitening treatment. It can be estimated by the value obtained by subtracting the carbon content derived from residual calcium carbonate from the total carbon content obtained by. It is preferable to make the residual carbon ratio derived from the organic matter as low as possible, and by setting it to 1% by weight or less, it is possible to recover a regenerated pigment suitable as a coating pigment. The residual carbon ratio derived from organic matter can be reduced to 1% by weight or less by performing a whitening treatment at a treatment temperature of 450 ° C. or higher, preferably 600 ° C. or higher until the whiteness reaches 70% or higher.

After carbonization and whitening treatment, the calcium carbonate contained in the raw material sludge is thermally decomposed into calcium oxide. The decomposition rate of calcium carbonate can be estimated by measuring the peak intensity ratio of the two and the calorific value of the slaking reaction after the whitening treatment using an X-ray diffraction analyzer. 50% for sludge with high calcium carbonate content
If the decomposition of calcium carbonate proceeds beyond the above range, the viscosity increases when the regenerated pigment is slurried, and it becomes difficult to carry out the transfer and coating operations. It is also possible to neutralize the slurry containing calcium hydroxide by adding carbon dioxide or sulfuric acid to reduce the viscosity, but the less decomposition of calcium carbonate saves the neutralization reaction tank, acid, time, etc. Connection is preferable. For this reason,
The decomposition rate of calcium carbonate is preferably 50% or less, 30
% Or less is more preferable. Specifically, the decomposition rate of calcium carbonate can be reduced to 50% or less, and more preferably 30% or less by setting the firing conditions in the whitening treatment apparatus not to exceed 800 ° C.

As a method for heating the carbide, it is possible to directly heat the carbide with combustion gas, but unburned carbon contained in the hot air comes into contact with the whitened white inorganic particles, resulting in a decrease in whiteness. It is more preferable to provide partition walls so that the sludge does not come into direct contact with hot air. That is, even in the whitening treatment step by decarbonization,
It is more preferable that the indirect heating furnace has a double structure including a whitening chamber and a heating chamber for decarburizing a closed type carbide as in the carbonization step.

Although it is possible to electrically heat the heating chamber, heating with a combustion gas of kerosene or heavy oil is economically preferable. Hot air obtained by recovering and burning the volatile gas derived from the sludge can also be used. In addition to this, it is also possible to use combustion gas discharged from an existing incinerator such as an incinerator. Examples of the incineration facility include a grate system (stoker furnace), a spray floating system, a material stirring system, a hot air combustion system, and the like.

In addition to this, a rotary kiln installed as a part of the wastewater treatment equipment in each paper mill or an existing incinerator (a cyclone furnace or a fluidized bed incinerator) can be used, but long-term decarbonization is possible. It is preferable to use a rotary kiln capable of whitening treatment by.

Between the carbonization treatment and the whitening treatment, the temperature of the object to be treated is once cooled to 400 ° C. or lower, and the subsequent treatment is carried out, so that the combustible gas derived from the organic matter thermally decomposed by the carbonization treatment is generated. It can be completely removed from the carbide. Further, by bringing water and / or steam into contact with the carbide during this period to cool the carbide, the specific surface area of the carbide can be increased, and a bulky recycled pigment having a high specific surface area can be recovered. Further, by doing so, the reaction efficiency with oxygen in the whitening treatment step is improved, and whitening by decarbonization can be efficiently performed.

When the carbonization treatment and the whitening treatment are continuously carried out, a screw and a stirring blade can be installed in each heat treatment chamber to forcibly transfer the sludge and the carbide. By adjusting the shape and size of the screw and the stirring blade, stirring can be promoted and heat treatment efficiency can be improved. Conversely, sludge and carbide can be transferred by rotating the polygonal carbonization chamber.

An example of a heat treatment apparatus that can be used when producing the recycled pigment used in the present invention will be described in detail with reference to FIG. FIG. 2 is a schematic system diagram of an example of a heat treatment apparatus that performs a carbonization step and a whitening treatment step by decarbonization. The carbonization process is performed by the first indirect heating furnace 1 and the second indirect heating furnace 6. The whitening treatment step by decarbonization is performed in the third indirect heating furnace 10. The first indirect heating furnace 1 is a drying zone in the carbonization process, and sludge is introduced from the sludge introducing port 2 of the first indirect heating furnace and dried in the sludge drying chamber 3. A hot air intake port 4a for heating the sludge drying chamber and a hot air, steam, and dry distillation gas discharge port 5a are provided. Although not shown, in the vicinity of the discharge port 5a, a minute opening is provided in the latter half of the sludge drying chamber 3 in order to discharge water vapor and the like generated from the sludge to the discharge port.

The second indirect heating furnace 6 is a pyrolysis zone in the carbonization process. A hot air intake port 4b for heating the sludge pyrolysis and carbonization chamber 7 of the second indirect heating furnace to carbonize the dried sludge is provided on the other side, and a hot air, steam, dry distillation gas discharge port 5b is provided on the other side. . Although not shown, in the vicinity of the discharge port 5b, a minute opening is provided in the latter half of the sludge pyrolysis / carbonization chamber 7 in order to discharge the dry distillation gas or the like generated from the sludge to the discharge port. . When the carbonization ends, the carbide is discharged from the carbide discharge port 8.

The carbide discharged from the carbide discharge port 8 is
It is transferred to the third indirect heating furnace 10 through the carbonized material flow path 9 and subjected to whitening treatment by decarbonization. Carbide is introduced from the carbide inlet 11 of the third heating furnace, an air inlet 12 for oxidizing the carbide, a whitening chamber 13 for decarbonizing the carbide, and a hot air inlet 4c for heating the whitening chamber for decarbonizing. , Hot air and steam outlets 5c are provided. The regenerated pigment that has been whitened by decarbonization is discharged from the regenerated pigment recovery port 14.

The carbonization step will be described with reference to FIG. The carbonizer is provided with a two-stage indirect heating zone. This is because the sludge drying and pyrolysis temperatures in the carbonization process are different. Sludge is dried in the first indirect heating furnace 1. When the ambient temperature of the sludge drying chamber 3 is 400 ° C. or lower, the water content in the sludge can be evaporated.

By blowing air from the hot air intake port 4a, the sludge can be indirectly heated and dried.
The steam and hot air generated from the sludge are discharged from the discharge port 5a. The hot air intake ports 4a, 4b, 4c and the exhaust ports 5a, 5b, 5c are respectively connected to a hot air generator (not shown), and the hot air supplied from the hot air generator has a temperature, a supply amount, and an exhaust amount. It can be adjusted. In addition to this, it is also possible to use combustion gas discharged from an existing incinerator such as an incinerator.

After the sludge is dried, the dried sludge is pyrolyzed and carbonized by the second indirect heating furnace 6. In the carbonization chamber 7 of the dry sludge, organic matter of the dry sludge is thermally decomposed. At this time, combustible gases such as carbon monoxide, methane, and ethane are generated, but since oxygen is not substantially contained in the furnace, combustion of organic substances can be suppressed. The flammable gas sucked from the fine openings provided in the latter half of the carbonization chamber is hot air, steam,
It is discharged together with hot air from the dry distillation gas discharge port 5b. A hot air generator (not shown) also burns those gases and can be used as a heat source for sludge drying and carbonization.

The temperature of the carbonizing chamber 7 is 400 ° C. to 1000 ° C.
By setting the temperature to preferably 450 ° C. to 700 ° C., it is possible to accelerate the thermal decomposition of organic matter at a temperature at which the white inorganic particles in the sludge do not undergo undesired thermal denaturation. These temperatures can be adjusted by the temperature, supply amount and discharge amount of the hot air generated by the hot air generator.

When continuously whitening by carbonization and decarbonization, the sludge can be forcibly transferred by installing a screw or a stirring blade in the heat treatment chamber. The sludge inlet has the minimum necessary opening to prevent air from entraining in the carbonization chamber. The amount of entrained air can be limited by forcibly pushing in with a screw. Further, the screw promotes stirring of the sludge, so that the thermal efficiency can be improved.

The carbonization time can be adjusted by measuring the amount of flammable gas generated by thermal decomposition using a gas detection device. At this time, the residence time of the sludge can be adjusted by adjusting the rotation speed of the screw. Although FIG. 2 shows an example in which the carbonization process is performed in two stages, it is also possible to perform the treatment in one stage. By using a twin-screw screw, it is possible to carbonize while crushing the carbide. As a result, carbon derived from organic matter is fixed carbonized,
Carbon derived from calcium carbonate is preferably retained as calcium carbonate and carbonized.

The whitening treatment step by decarbonization will be described with reference to FIG. The carbide transferred by the carbonized physical distribution passage 9 is
It is charged from a charging port 11 provided in the third indirect heating furnace 10. At this time, the air required for oxidizing the carbide can be taken in through the air intake 12. A flow controller can be installed at the intake to control the oxidation of carbides. The heating of the whitening chamber 13 by decarbonization can be performed by the combustion gas discharged from the existing incinerator such as an incinerator. In addition, it is preferable to adjust the supply amount of the oxygen-containing gas (air) or hot air (combustion gas) so that the carbides self-combust in the preferable temperature range. In particular, when the raw material sludge is unknown or has large fluctuations, it is preferable to observe the temperature change of the carbide in more detail by installing many more sensitive temperature sensors in the whitening device.

The whitening chamber 13 for decarbonization is 450 ° C. to 10 ° C.
By heating so as to be in the range of 00 ° C., the whiteness can be efficiently improved. At this time, it is preferable to adjust the temperature of hot air, the supply amount and the discharge amount, and the air flow rate so that the carbide is not rapidly heated. As a result, 2 of 450 ° C. to 600 ° C. and 600 ° C. to 1000 ° C.
It is preferable to provide heating zones in more than one stage. The regenerated pigment that has been whitened by decarbonization is discharged from the regenerated pigment recovery port 14.

FIG. 3 shows an example in which an internal combustion type rotary kiln is installed in place of the third indirect heating furnace used in the whitening process by decarbonization of FIG. 2 and a storage device 16 is installed in place of the carbonized material flow passage 9. . This will be described in detail with reference to FIG. Since the carbonization process is the same as the example shown in FIG. 2, the description is omitted.

This is an example of whitening treatment by decarbonization in the internal combustion type rotary kiln 15. Carbide is once stored in the carbide storage device 16 and is charged from the carbide charging port 17 of the internal combustion type rotary kiln. Decarbonization whitening treatment room 1
8, a burner 19 and a recycled pigment recovery port 20 are provided.

The carbide obtained by the carbonization step is stored in the storage device 16 without being directly sent to the whitening step by decarbonization. Here, it is preferable to cool the carbide once to completely evaporate the combustible gas. Furthermore, it is also possible to spray water in order to increase the specific surface area of the carbide. By spraying water pressurized with a pump using a spray nozzle, it is possible to carry out uniform spray processing. If a two-fluid nozzle that simultaneously ejects water and pressurized air is used, the size of water particles can be adjusted to 100 μm or less, and a more uniform spraying process becomes possible.

Next, a process using a rotary kiln in the whitening process by decarbonization will be described. The carbide introduced from the carbide inlet 17 of the internal combustion rotary kiln 15 is burner 1 installed near the recycled pigment recovery port 20.
Directly heated by 9. The temperature in the furnace is 450 ℃ ~ 10
By heating so as to be in the range of 00 ° C., the whiteness can be efficiently improved. At this time, it is preferable to adjust the temperature in the furnace by adjusting the fuel supplied to the burner 19 so that the carbide is not rapidly heated. By adjusting the number of rotations and the inclination angle of the rotary kiln 15, the whitening treatment time by decarbonization can be easily adjusted. The treatment time can be adjusted depending on the desired whiteness of the recycled pigment. Although not shown, the combustion gas discharged from the internal combustion type rotary kiln 15 is preferably treated by using an exhaust gas treatment device.

Although the charcoal-based material storage device 16 is used in FIG. 3, it is also possible to directly connect the indirect heating furnace in the carbonization processing step and the rotary kiln in the whitening processing step by decarbonization by the carbonized material flow passage 9. Further, in FIG. 2, it is possible to use the carbide storage device 16 instead of the carbonized material flow passage 9.

In addition to the internal combustion type rotary kiln used in FIG. 3, an existing incinerator (a cyclone furnace or a fluidized bed incinerator) installed as a part of the wastewater treatment equipment in each paper mill can be used. An indirect heating type rotary kiln can also be used, and the hot air can use combustion gas discharged from an existing incinerator such as an incinerator. In particular, although not shown, it is preferable to use a heat insulating material in the whitening treatment apparatus for carbonization and decarbonization to cover the surroundings to keep the apparatus warm. Further, as the material of the device, ceramics or alloys can be selected in consideration of processing temperature and economy.

(Slurrying / grinding process step) Next, referring to FIG.
The slurry forming / grinding process step 54 will be described. In the present invention, the recycled pigment recovered from the papermaking sludge can be used as it is, however, it is difficult to avoid the inclusion of coarse particles, and coating defects such as streaks may occur. It is preferable to use it after wet pulverization. In the present invention, the optimum particle size varies depending on the target coated paper, but the median size is 0.1
It is preferable to carry out the pulverization treatment so that the particle size falls within the range of ˜5 μm.

As a crushing method, crushing with only a dry crusher or crushing with only a wet crusher is possible, but it is preferable to appropriately combine a dry crusher and a wet crusher. It is also possible to provide a plurality of each crusher or only one of them. From the standpoint of pulverization efficiency, it is preferable to make the particles smaller by dry pulverization before wet pulverization. At this time,
If the particle size of the dry pulverized powder exceeds 35 μm, the dispersion of the powder in the disperser becomes poor, the pulverization efficiency in the pulverizer becomes poor, and the disperser and the pulverizer are abraded, resulting in regenerated pigment Whiteness decreases. In addition, powder is 2μm by dry pulverization.
It is economically unfavorable to pulverize the pulverized product to less than the following range.

As described above, the dry pulverizer and the wet pulverizer are combined, and the median diameter of the granules is 2 μm to 35 in the dry pulverization.
μm, preferably 2 μm to 10 μm, and wet pulverized as an aqueous slurry having a predetermined solid content concentration, for example, 50% or more, to efficiently reduce the whiteness due to abrasion of the disperser or the wet pulverizer. Fine particles can be crushed. If the crushing process is insufficient, there is a possibility that the roll surface may be worn at the time of manufacturing or processing the coated paper, or the blade of the cutter may be significantly worn, causing a serious problem.

The dry pulverizer will be described in more detail below. Examples of the crusher for crushing several mm to several tens of μm include a roll crusher, a roll mill, a stamp mill, an edge runner, a cutter mill, and a rod mill. A roller mill, a jet mill, a dry ball mill, an impact type crusher or the like is used as a dry fine crusher having a particle size of several μm or less suitable for a coating pigment. It should be noted that these dry crushers use wear-resistant steel, etc., and have taken into consideration wear.

Next, as a wet pulverizer, a sand mill,
Examples thereof include pulverizers such as a wet ball mill, a vibration mill, a stirring tank type mill, a flow tube type mill and a coball mill. In order to prevent the recycled pigment from being polluted (whitening) due to the abrasion of the crusher
It is desirable to coat the grinding zone of the grinder with an abrasion resistant material such as rubber or abrasion resistant plastic. The pulverization zone refers to the inner surface of the pulverization chamber, the outer surface of the stirring member, and the like, and is the zone where the powder in the slurry comes into contact during pulverization.
When a member such as a partition plate is provided in the crushing chamber, these also form a part of the crushing zone. It should be noted that in a wet pulverizer in which a grinding medium such as balls and beads is used, it is desirable to use abrasion-resistant grinding media such as wear-resistant ceramic balls and zirconium beads.

As the abrasion-resistant plastic, urethane resin and nylon resin can be exemplified.
Although it is desirable to coat it in a thickness of about m to 10 mm,
It can be appropriately selected depending on the frequency of use and the grinding conditions. Before and after the wet pulverization, it is possible to remove the hard-to-pulverize sinter through a screening device such as an open type vibrating screen, a multi-tube vibrating pressure filter or a mechanical pressure filter. Also, in the above-mentioned disperser, it is desirable to coat the dispersion zone with rubber, abrasion-resistant plastic, or the like as in the wet pulverizer.

At the time of wet pulverization, in order to uniformly disperse the powder, a dispersant is added to form a slurry. By adding a dispersant, it is possible to prevent an increase in viscosity even if the concentration of the slurry is increased, and it is possible to prevent an increase in viscosity due to wet pulverization and improve pulverization efficiency and handleability. Sulfonic acid group-containing polyacrylic acid salt has the advantage of being superior in salt resistance and heat resistance as compared with other dispersants. Therefore, a sulfonic acid group-containing polysulfone having a molecular weight of about 1000 to 10000 is used as a dispersant. The acid group-containing polyacrylate is added to the pigment in an amount of 0.05 to 3
It is advisable to add wt%. By the way, even if the amount added exceeds 3%, the effect of improving the dispersibility reaches a peak, and
% Or less, the dispersibility is poor and wet pulverization cannot be performed efficiently.

The pH of the suspension can be adjusted to 8 to 13 by using carbon dioxide when the regenerated pigment is made into a suspension in an aqueous medium or at the time of crushing treatment.

(Paint Preparation Step) Next, the coating solution preparation step 55 of FIG. 1 will be described. In the present invention, the proportion of the regenerated pigment in the pigment constituting the pigment coating layer is a single layer of the coating layer, a multilayer, or where in the multi-layer coating layer the regenerated pigment is used, Further, it can be appropriately adjusted according to the target quality of the intended coated paper for printing and is not particularly limited. However, in order to obtain the coated paper for printing with high opacity, which is the object of the present invention, 10% by weight or more, preferably 20% by weight or more, of all the pigments constituting the coating layer are recycled pigments. It is desirable to mix it with. In addition, the upper limit of the proportion of the recycled pigment used can be 100% by weight, for example, when blended in the undercoat coating layer, while the recycled pigment is used in the outermost layer of the single-layer coating layer or the multilayer coating layer. In the case of blending, considering the quality such as opacity and whiteness of the coated paper, 50 out of all pigments constituting the coating layer are included.
It is preferable that the recycled pigment is blended in an amount of about% by weight.

Pigments which can be used in combination with the recycled pigment include kaolin, clay, calcium carbonate, aluminum hydroxide, zinc oxide, which are used in the production of ordinary printing paper.
Examples thereof include inorganic pigments such as barium sulfate, calcium sulfate, silica, activated clay, talc, satin white, and lake, and organic pigments such as plastic pigments. In this case, the absolute value of the difference between the whiteness of the base paper and the whiteness of all the pigments forming the coating layer containing the recycled pigment is adjusted to be within 10 points, so that high opacity and whiteness unevenness are obtained. It is possible to obtain a coated paper with a small amount.

The coated paper for printing in the present invention includes newsprint. The whiteness of newsprint is generally about 50%, but the opacity of lightweight newsprint is 90%.
The above is required. Therefore, as a measure for the opacity of such newsprint, a processing layer (coating layer) containing a recycled pigment and an adhesive as main components can be provided on the newsprint. Since opacity is the most important paper quality in newsprint, the difference between the whiteness of the base paper and the whiteness of all the pigments constituting the coating layer may not be within ± 10 points.

In the coated paper for printing of the present invention, the adhesive used together with the pigment is not particularly limited, but for example, proteins such as casein, soybean protein and synthetic protein: styrene / butadiene copolymer Conjugated diene polymer latex such as polymer, acrylic polymer latex such as polymer / or copolymer of acrylic acid ester and / or methacrylic acid ester, vinyl polymer latex such as ethylene / vinyl acetate copolymer, or these Alkali-soluble or alkali-insoluble polymer latex obtained by modifying various polymer latexes of the above with a functional group-containing monomer such as carboxyl group: synthetic resin adhesives such as polyvinyl alcohol, olefin / maleic anhydride resin, melamine resin, etc. :
Positive starch, oxidized starch, enzyme modified starch, thermochemical modified starch,
Adhesives for ordinary coated papers, such as etherified starch, esterified starch, and cold water-soluble starch: cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, can be appropriately selected and used.

The compounding ratio of the adhesive is pigment 10 in comparison with the solid type.
5 to 25 parts by weight, more preferably 1 to 0 parts by weight
It is about 0 to 20 parts by weight. In the pigment coating composition, if necessary, a dispersant, a thickener, a water retention agent, a flow modifier,
Various auxiliaries such as defoaming agents, mold release agents, water resistant lubricants, bluing agents, antiseptics, lubricants, dyes, and pH adjusting agents can also be appropriately added.

In the coated paper for printing of the present invention, when a recycled pigment is used in the outermost coating layer, a fluorescent dye is added in an amount of 0.3 to 3.0% by weight based on the recycled pigment. Preferably.

The fluorescent dye absorbs light in the vicinity of 340 to 380 nm, and the absorbed energy is 430 to 440 nm.
It is a dye that enhances the whiteness of coated paper by emitting fluorescent light in the visible region. Specifically, the following compound system can be illustrated.
These may be used alone or in combination of two or more. 4,4'-bis (4,6-disubstituted-1,3,5
-Triazinyl-2-amino) stilbene-disulfonic acid type, α, β-bis (benzoxazolyl) ethylene type, alkoxynaphthalic acid-N-substituted imide type, benzoxazole type, coumarin type, thiophene type structure An organic compound having

In the present invention, as described above, it is also possible to form two or more pigment coating layers on one side of the base paper, and the coating layers are provided with functions such as smoothness, gloss, and acceptance of printing ink. Therefore, it is preferable to form two or more (normally two) coating layers. It is also possible to form the coating layer on both sides of the base paper. At this time, the recycled pigment may be added to any layer. In the present invention, it is essential that the whiteness of the recycled pigment used does not fall below 60%. However, when the whiteness is lower than this, the desired whiteness can also be obtained by adding a fluorescent dye. It is because it is difficult to obtain the coated paper for printing. The fluorescent dye can be added separately to each coating material of the multi-layer coating.

The solid content concentration of the coating material for forming the pigment coating layer is generally about 40 to 75% by weight, but in consideration of operability, it is preferably in the range of 45 to 70% by weight.

The paint prepared under the above conditions is, for example, a blade coater, an air knife coater, a roll coater, a reverse roll coater, a bar coater curtain coater, a die rod coater, a gravure coater, a champlex coater, a gate roll coater, and a size. Coating is performed by an on-machine or off-coater equipped with a known coating device such as a press. When finishing coated paper with high glossiness, it is preferable to employ a blade coater, a rod blade coater, or the like.

The coating amount of the coating material on the base paper can usually be appropriately adjusted within the range of about ² to 50 g / m ^{2 on} a dry weight basis. The coating amount is the total coating amount including the multilayer coating. The pigment coating layer is dried and then finished through a finishing device such as a super calender or a gloss calender.

In the present invention, waste paper pulp can be used as the pulp raw material constituting the raw paper, and examples of raw waste paper include newspaper waste paper, printing waste paper, magazine waste paper, OA waste paper and the like.
In addition to this, virgin pulp can be used, and there is no limitation on hardwood and softwood, and pulp obtained from both raw materials can be arbitrarily blended. Further, also in such a method for producing pulp, in addition to kraft pulp (KP) and sulfite pulp (SP) which are chemical pulping methods in which delignification is performed by a cooking liquor, ground wood pulp (GP) which is mechanically ground wood is also used. , Refiner pulp groundwood pulp (RGP),
Thermo-mechanical pulp (TMP), Chemi-thermo-mechanical pulp (CTMP), Chemi-ground pulp (CG)
Any of mechanical pulping methods such as P) and semi-chemical pulp (SCP) may be used. In addition, when blending waste paper pulp, it is possible to have an arbitrary blending ratio, but the absolute value of the difference between the whiteness of the base paper and the whiteness of all pigments forming the coating layer containing the recycled pigment, It is desirable to mix it within 10 points in order to obtain a coated paper without uneven whiteness.

Since the coated paper for printing of the present invention has the coating layer containing the regenerated pigment obtained by the specific method, it is characterized by a high scattering surface area and a high opacity.
At this time, as described below, by blending the raw paper with a high-whiteness waste paper pulp obtained by adding a bleaching step in addition to the normal deinking step, it was difficult to achieve high opacity and compatibility. A coated paper for printing with high whiteness can be obtained. Of course, even in this case, it is necessary to adjust the whiteness of the pigment and the base paper so that the difference between the whiteness of the base paper and the whiteness of all the pigments forming the coating layer containing the recycled pigment is within ± 10 points. Therefore, there is no difference in that a coated paper with less unevenness in whiteness can be obtained. Hereinafter, a method for producing used paper pulp (deinked pulp) suitable for use in the present invention will be described. Since such used paper pulp can be blended in the base paper at a high rate of 50% by weight or more. It is also preferable from the viewpoint of environmental protection and effective use of resources.

Generally, as a method for producing deinked pulp from waste paper, the pulp and the ink are treated by appropriately combining a (printing) waste paper disintegration step, an alkali soaking (alkaline immersion) step, a flotation step and a washing step. Separated. In the present invention, such a deinking step is further combined with a peroxide bleaching step, particularly a hydrogen peroxide bleaching step, so that a suitable deinking step for applying a coating liquid containing a specific regenerated pigment is achieved. Ink pulp can be manufactured.

In the peroxide bleaching step, it is more preferable to use a surfactant or an alkaline chemical in combination, because the pulp fibers can be swollen and the ink can be separated more easily. At this time, the peroxide also has an effect of preventing yellowing of the pulp due to alkali. Following the peroxide bleaching step, it is more preferable to attach the ink particles to the air bubbles by a flotation step to float the ink particles and separate the ink particles from the pulp.

By adding the peroxide bleaching step as described above, it is possible to easily obtain a deinked pulp having a whiteness of 70% or more, preferably 80% or more, which is suitable for the base paper of the present invention. The addition rate of peroxide in the peroxide bleaching step is 0.5 to 5% by weight, and preferably 1 to 3% by weight based on pulp. If the addition rate is less than 0.5% by weight, not only the whiteness improving effect is low, but also alkali yellowing may occur due to the alkali used in combination. On the other hand, even if added in excess of 5% by weight, the whiteness reaches an equilibrium level and reaches a ceiling, which is not economical. In addition, it is preferable to perform the peroxide bleaching treatment in a plurality of stages rather than adding a large amount of peroxide at one time because the whiteness can be efficiently improved.

As the peroxide used for peroxide bleaching, sodium peroxide, calcium peroxide, hydrogen peroxide, peracetic acid and the like can be used. Of these, hydrogen peroxide dissociates into peroxide ions, which act as a nucleophilic attack reagent under alkaline deinking conditions, and oxidatively decomposes the colored structure without damaging the fibers in the pulp to lighten the pulp. It is more preferable because it can be converted into

When a plurality of stages of peroxide bleaching are provided, it is preferable to appropriately combine the flotation step and the washing step. Furthermore, by combining peroxide bleaching with reduction bleaching, it is possible to more efficiently obtain a deinked pulp having a whiteness of 80% or more suitable for the base paper of the present invention.

The addition ratio of the alkaline chemicals in the peroxide bleaching step is generally 0.5 to 10% by weight based on the pulp. If the addition rate is less than 0.5% by weight, the effect of improving whiteness is low. On the other hand, if the addition rate is too high, alkali yellowing will occur. As the alkaline chemical, caustic soda, sodium silicate or the like is appropriately used, but it is also possible to add two or more kinds of alkaline chemicals in combination. As the deinking agent in the peroxide bleaching step, a nonionic hydrophilic surfactant, a cationic surfactant or an anionic surfactant usually used for alkali soaking can be appropriately selected and used.

In order to improve the effect of adding chemicals (liquid) in peroxide bleaching, the pulp concentration is preferably 5 to 35% by weight, preferably 10 to 20% by weight.
If the pulp concentration is less than 5% by weight, the reaction efficiency between the pulp fiber and the peroxide will be poor, and if the pulp concentration exceeds 25% by weight, uniform reaction will be difficult.

The temperature in peroxide bleaching is generally 30.
To 120 ° C, preferably 50 to 80 ° C. When the temperature is lower than 30 ° C, the bleaching reaction rate is low, and a sufficient dust (ink particle) reducing effect cannot be obtained. On the other hand, when the temperature exceeds 120 ° C., the decomposition reaction of the peroxide becomes large, the effective amount of peroxide with respect to the pulp decreases, and the radicals produced attack the pulp, resulting in a decrease in the degree of polymerization of the pulp and a decrease in strength. Is not suitable as it will occur.

The residence time of pulp in peroxide bleaching is in the range of 5 to 120 minutes, preferably 10 to 90 minutes. If the time is less than 5 minutes, the increase in whiteness is small, while if it exceeds 120 minutes, the whiteness reaches equilibrium.
Not only is it uneconomical because it reaches a ceiling, the residual amount of peroxide decreases, and yellowing of the pulp due to alkali also occurs.

The base paper filler used in the present invention is an inorganic filler such as heavy calcium carbonate, light calcium carbonate, talc, clay, kaolin, titanium dioxide, synthetic silica, and aluminum hydroxide, which are commonly used in paper production. Although it can be appropriately selected and used from synthetic polymer fine particles such as polystyrene resin and urea formaldehyde resin, the regenerated pigment used in the coating layer of the present invention can also be used. Of course,
Two or more of these may be used in combination. The amount of the filler added is preferably about 1 to 30% by weight based on the solid content of the entire stock. Further, in the paper material containing pulp and filler, as needed, a paper strengthening agent, a sizing agent, a dye, a fluorescent dye,
An antifoaming agent, a pitch control agent, a slime control agent and the like can be added as appropriate.

Using such a paper material, a base paper is manufactured by making a paper with a known paper machine. The base paper, if necessary,
A surface treatment agent such as starch can be size-pressed. The basis weight of the base paper is not particularly limited, but usually, when the base paper having a basis weight of about 30 to 100 g / m ² is used, the effect desired by the present invention is remarkably exhibited. Of course, it is also possible to coat on cardboard, cardboard, and other thick paper that exceeds this range.

In the present invention, since the recycled pigment having a large specific surface area recovered from the sludge by the carbonization treatment and the subsequent whitening treatment is used, the advantage that a coated paper for printing having a high opacity can be obtained, and the whitening treatment Since the carbon residual rate in the recycled pigment can be adjusted depending on the degree, there is an advantage that the whiteness and the opacity can be adjusted according to the intended coated paper.

When a general pigment is replaced by the recycled pigment used in the present invention, the weight of the coated paper can be reduced as compared with the coated paper having a constant opacity because the coated paper can be made smaller. You can Further, in the present invention, a method of adding a black dye to a pigment coating layer which is adopted as an opacity improving method in a part of lightweight coated paper having a basis weight of about 80 g / m 2 or less is also calcium carbonate. By substituting recycled pigment for some of the normal pigments such as 8
There is also an advantage that a coated paper for printing having a high opacity of 5% or more can be obtained.

[0099]

The present invention will be described in more detail with reference to the following examples, but of course the present invention is not limited thereto. In the following examples and comparative examples,
Parts and% mean parts by weight and% by weight, respectively.

Example 1 <Description of Raw Materials> A suspension of mixed waste paper containing newspaper and leaflets that had been disintegrated in advance was sent to a deinking tower and soaked at a temperature of 70 ° C. for 4 hours. The amount of deinking agent added is 0.8% of caustic soda, 2.5% of sodium silicate, as solid content in terms of pulp.
The hydrogen peroxide was 1.2% and the surfactant was 0.1%. Next, dilute the suspension taken out from the deinking tower with dilution water,
This diluted suspension was washed with a washing machine and dehydrated to a concentration of 25% to obtain waste paper pulp. Next, the used paper pulp was diluted to a pulp concentration of 1%, placed in a floatator and deinked.

To the pulp after deinking, 2.0% of caustic soda, 5.0% of sodium silicate, 0.15% of surfactant, and 1.5% of hydrogen peroxide were sequentially added as solid contents in terms of pulp. Hydrogen peroxide bleaching was carried out in a hydrogen peroxide bleaching tower at 60 ° C. for 120 minutes at a pulp concentration of 10%. After bleaching with hydrogen peroxide, it was washed and dehydrated, and the same bleaching with hydrogen peroxide was repeated. From the obtained bleached pulp, a handmade sheet was prepared based on ISO5269-1 (a method for preparing handmade paper for pulp test), and air-dried. Whiteness of the prepared handmade paper (ISO
2470) 80%, opacity (ISO2471)
(According to the above) was 82%.

<Preparation of Base Paper Blended with Waste Paper Pulp> Next, 60 parts of the waste paper pulp obtained above was exposed to a hardwood bleached pulp (own-made LBKP) having a whiteness of 83% and an opacity of 78%.
40 parts were blended, and as solid content in terms of pulp,
Precipitating calcium carbonate (self-made) 12%, sizing agent (Fibran 81 / Oji National Co., Ltd.) 0.02%, cationized starch (Ace K100 / Oji Cornstarch)
0.8%, acrylic amide polymer (Himoloc N
R12MLS / Himo Co.) 0.005% was added as a paper stock to prepare a base paper for coating having a basis weight of 48.0 g / m ^{2 using} a Fourdrinier paper machine. The obtained base paper had a whiteness of 81% and an opacity of 80%.

<Description of Carbonization Device> The device configuration in the embodiment will be described with reference to FIG. 4. Reference numeral 21 is a raw material hopper, and 22 is a cutting device installed below the raw material hopper. Reference numeral 23 is a device for conveying the cut out raw material to a drying device, and A is a raw material drying device. In the drying device A, 24 is a furnace main body, 25 is a hot air supply device to the drying device, and 26 is an in-furnace conveying device connected in two stages, upper and lower. Reference numeral 30a is a thermometer for measuring the temperature inside the drying apparatus furnace main body. B is a carbonization device installed directly below the drying device. In the carbonization device B, 27 is a furnace body, 28 is an in-furnace conveying device connected in three stages, and 29 is a hot air generator for the carbonization device. Thirty
b is a thermometer for measuring the temperature inside the furnace body of the carbonizer.

<Explanation of whitening device> Reference numeral 31 is a raw material carrying device for carrying the carbide discharged from the carbonizing device to the firing device (whitening device) C. In the firing apparatus C, 32 is a furnace body, and 33 is an in-furnace conveying device connected in two stages, upper and lower.
Reference numeral 34 is a hot air generator for supplying hot air to the firing device. Reference numeral 35a is a thermometer for measuring the temperature inside the furnace body of the baking apparatus.

<Supply of Sludge> Washing wastewater of waste paper pulp was supplied to a flotation machine and subjected to a flotation treatment to obtain white water. The obtained white water was sent to a screw press type dehydrator (Fukoku Manufacturing Co., Ltd.) to obtain sludge having a solid content concentration of about 50%. The sludge stored in the raw material hopper 21 is cut out from the cutting device 22 in a fixed amount. The cut-out raw material is dried by the conveying device 23 to the drying device A.
It is continuously charged inside. In this embodiment, 100 kg /
It cut out at hr.

<Drying and Carbonization of Raw Material> The raw material charged in the drying device is horizontally transported in the furnace body by the in-furnace transportation device 26. In the dryer A, the hot air generator 25
Indirect heating is performed by the hot combustion gas supplied from the inside to the inside of the furnace body to evaporate the moisture in the raw material. During this period, the oxygen-containing gas such as air in the carrier was replaced by the generated steam, and the oxygen concentration was less than 0.1%, resulting in a poor oxygen condition. The raw material after the drying treatment was continuously charged into the main body of the carbonization device. In the carbonization device, the raw material dried by the combustion hot gas supplied from the hot air generator 29 while horizontally moving in the transfer device is indirectly heated through the iron shell of the transfer device, and the furnace ambient temperature is set to 600 ℃ was made. During this period, the oxygen-containing gas such as air is completely replaced by the carbonization gas generated in the carbonization step, and the oxygen concentration is 0.1%.
%, Which is a reducing atmosphere under a poor oxygen condition and promotes carbonization of organic substances. In this example, the deinking papermaking sludge was continuously treated, and the residence time in the furnace in the carbonization device was set to 60 minutes. The proportion of fixed carbon derived from organic substances in the generated carbide was 8% (weight ratio) on average. The amount of raw material (carbide) discharged from the carbonization device was 30 kg / hr after the drying and carbonization treatment. The specific surface area of the obtained carbide by the BET adsorption method was 21 m2 / g.

<Whitening Treatment of Carbide> The carbide discharged from the carbonization chamber B is burned by the transfer device 31 (whitening device).
C was continuously charged. The oxygen concentration of the combustion gas introduced can be adjusted from 3% to 15% by the combustion air ratio and air addition by a blower fan. In this embodiment, the oxygen concentration in the furnace of the firing device C was set to 12%. . The temperature inside the furnace of the firing device C can be controlled. This temperature was 650 ° C. in this example. The object to be calcined was horizontally moved and stirred in this atmosphere gas by the screw mechanism of the conveying device to slowly perform the decarbonization reaction by oxygen. The residence time of the carbide in the firing device C was set to 120 minutes.
The amount discharged from the firing device C was 25 kg / hr.

<Regenerated pigment after whitening treatment> From the measurement results of calcium element using a fluorescent X-ray analyzer (XRF, Shimadzu Corporation), the estimated calcium carbonate content in the raw material sludge was found to be all white inorganic particles. On the other hand, it was 60%. Furthermore, from the measurement results of the regenerated pigment after the whitening treatment with an X-ray diffraction analyzer (XRD, Mac Science Co., Ltd.), the estimated decomposition rate of calcium carbonate due to the carbonization and the whitening treatment was 20%. Therefore, it is considered that the regenerated pigment after the whitening treatment contains about 50% of calcium carbonate. The remaining 50% is kaolin and calcium oxide.

<Pulverization> The regenerated pigment obtained above was mixed with a dispersant.
(A6028, Toagosei Co., Ltd.) Into water containing 1.0%, a slurry having a solid content of regenerated pigment of 60% was prepared and wet-milled using a bead mill (Ashizawa). The 50% particle size (median diameter) of the recycled pigment after one pass of the crusher is 0.5 μm, and the specific surface area (BET adsorption method) is 18 m ² / g.
Met. The particle size distribution of the regenerated pigment was measured using a cedigraph particle size distribution measuring device (Micromeritic).

<Measurement of Whiteness of Regenerated Pigment> After drying a part of the regenerated pigment pulverized as described above, about 10 g of it was sampled and pulverized in a mortar until coarse particles disappeared. Using a powder tablet molding machine consisting of a cylindrical column having a thickness, pressure was applied at 13 kgf / cm ² for 30 seconds for molding. The cylinder is placed and manipulated on a high gloss acrylic plate. The whiteness of the regenerated pigment was 82% as a result of measuring the whiteness with the tablet-like powder attached to the cylinder. The whiteness was measured according to JIS Z8722 using a spectral whiteness colorimeter (manufactured by Suga Test Instruments Co., Ltd.).

<Preparation of Pigment Coating Layer Coating Liquid> As a pigment mixture, starch (Ace A / Oji Corn Starch Co.) was added to 100 parts (solid content conversion) of the regenerated pigment after crushing treatment obtained above. A coating liquid was obtained by adding 3 parts (as solid content) and 7 parts (as solid content) of styrene-butadiene copolymer latex (JSR-0613 / JSR Co.). The total solid content concentration of the coating liquid was 56%.

<Preparation of coated paper for printing> Preparation of base paper containing waste paper pulp The above-prepared base paper for coating (basis weight 48.0 g / m ² ) was coated with the pigment obtained above. The coating liquid for layers was coated on both sides with a desktop blade coater so that the dry solid content was 10 g / m ² on one side, and dried to obtain coated paper for printing.

Example 2 The double-sided coated paper obtained in Example 1 was smoothed with a super calendar to obtain a coated paper for printing.

Example 3 In the coating liquid of Example 1, a fluorescent dye (Branco Hower ZSKN
/ Bayer Co., Ltd. to a pigment solid content (regenerated pigment) of 0.
A double-sided coated paper was prepared in the same manner as in Example 1 except that 5 parts (in terms of solid content) was added, and smoothed with a super calendar to obtain a coated paper for printing.

Example 4 In the preparation of the pigment coating layer coating solution of Example 1, 65 parts of the regenerated pigment was replaced with 65 parts of ground calcium carbonate (manufactured by-house),
Further, double-sided coating was performed in the same manner as in Example 1 except that 0.15 parts of fluorescent dye (Brancohower ZSKN / Bayer) was added to the pigment solid content (0.4 parts to the recycled pigment solid content). Paper was prepared, and the obtained double-sided coated paper was smoothed with a super calendar to obtain a coated paper for printing. The ground calcium carbonate used had a whiteness of 93%, 50%
The particle size (median diameter) was 0.9 μm, and the specific surface area measured by the BET method was 10 m ² / g. The whiteness of all the mixed pigments was 89%.

Example 5 A double-sided coated paper (before super calender treatment) obtained in Example 4 was coated with a top-coat paint having a dry solid content of 10 g / side.
Both sides were coated with a desktop blade coater so as to have a surface area of m ² and dried to obtain a coated paper, which was smoothed with a super calendar to obtain a coated paper for printing. As the topcoat paint, 60 parts of heavy calcium carbonate (made by itself) used in the coating liquid for the pigment coating layer of Example 3 and 40 parts of kaolin (HT / Engelhard)
Of starch (Ace A)
/ Oji Corn Starch Co., Ltd.) 3 parts (as solid content), styrene-butadiene copolymer latex (JSR-0613)
10 parts (solid content conversion) were blended. Kaolin has a whiteness of 79%, a particle size of 0.3 μm,
The BET specific surface area was 20 m ² / g.

Example 6 The base paper for coating used in Example 1 was a low whiteness base paper (whiteness 6
9%, opacity 89%, basis weight 48 g / m ² ) except that the coating was performed on both sides with a tabletop blade coater in the same manner as in Example 1 and dried to obtain a coated paper for printing. The low whiteness base paper is 100% recycled pulp, and contains 50% of the high brightness recycled pulp obtained in Example 1.

Example 7 In the whitening treatment of the carbide of Example 1, carbonization and firing were performed in the same manner as in Example 1 except that the whitening temperature of the firing device was 700 ° C. to obtain a regenerated pigment. The estimated calcium carbonate content of the regenerated pigment after the whitening treatment was 40%. The 50% particle size (median diameter) of the recycled pigment after one pass through the pulverizer was 0.5 μm as in Example 1, and the specific surface area (BET adsorption method) was 18 m ² / g. The whiteness of the regenerated pigment measured after pulverization and drying was 85%. A coated paper for printing was obtained in exactly the same manner as in Example 1 except that the above regenerated pigment was used.

Comparative Example 1 In the preparation of the coating liquid for the pigment coating layer of Example 1, except that the pigment composition was 100 parts of ground calcium carbonate (made by itself),
A coated paper for printing was prepared in exactly the same manner as in Example 1.

Comparative Example 2 A coating composition for printing was prepared in the same manner as in Example 1 except that the pigment formulation was changed to 100 parts of kaolin (HT / Engelhard) in the preparation of the pigment coating layer coating composition of Example 1. I made craft paper.

Comparative Example 3 The printing coated paper obtained in Comparative Example 1 was smoothed with a super calendar to obtain a printing coated paper.

<Measurement of Whiteness, etc. of Coated Paper> The whiteness, opacity and glossiness of the coated printing papers obtained in the above Examples and Comparative Examples were measured, and the results are shown in Table 1. .
The whiteness and opacity were measured in accordance with ISO2470 and ISO2471 using a spectral whiteness colorimeter (Suga Test Instruments Co., Ltd.). Also, the glossiness is measured by a gloss meter (MURAK
AMI COLOR RESEARCH LABOLA
(Tory Co., Ltd.) was used in accordance with ISO8254-1. Further, whiteness unevenness and print strike-through were visually evaluated, and the results are shown in Table 1. For printing strikethrough, print ink (GEO) on one side of the coated paper for printing.
0.2 cc of S-G and Dainippon Ink and Chemicals, Inc. was printed, and the back surface of the print was visually evaluated. "Evaluation criteria": Good: Somewhat inferior

[0123]

[Table 1]

[0124]

As is clear from the results of Table 1, the coated paper for printing of the present invention has a high opacity because it uses a specific recycled pigment made of sludge as a raw material in the pigment coating layer. ,
Moreover, it was a coated paper with excellent print-through.

[Brief description of drawings]

FIG. 1 is a process diagram conceptually showing a process for producing a coated paper for printing of the present invention.

FIG. 2 is a conceptual system diagram of an example of a heat treatment apparatus for performing a carbonization treatment step and a decarbonization whitening treatment step for producing a recycled pigment used in the coated paper for printing of the present invention.

FIG. 3 is a conceptual system diagram of another example of a heat treatment apparatus for performing a carbonization treatment step and a whitening treatment step by decarbonization for producing a recycled pigment used for the coated paper for printing of the present invention.

FIG. 4 shows an example of a heat treatment apparatus applied to an embodiment of the present invention.

[Explanation of symbols]

1: 1st indirect heating furnace (drying zone of carbonization process) 2: sludge input port 3: sludge drying chamber 4a: hot air intake port 5a: hot air, steam, carbonization gas discharge port 6: second indirect heating furnace (of carbonization process) Carbonization zone by pyrolysis 7: Sludge pyrolysis, carbonization chamber 4b: Hot air inlet 5b: Hot air, steam, carbonization gas outlet 8: Carbide outlet 9: Carbide distribution passage 10: Third indirect heating furnace (decarbonization) 11: Carbide charging port 12: Air intake port 13: Decarbonization whitening chamber 4c: Hot air intake port 5c: Hot air discharge port 14: Recycled pigment recovery port 15: Internal combustion rotary kiln (whitening band by decarbonization) 16 : Carbide storage device 17: Carbide charging port 18: Carbide oxidation chamber 19: Burner 20: Recycled pigment recovery port

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Nobuo Yamada             Prince, 3-3-1, Jokoji Temple, Amagasaki City, Hyogo Prefecture             Amagasaki Research Center, Paper Manufacturing Co., Ltd. (72) Inventor Yoshiki Kojima             Prince, 3-3-1, Jokoji Temple, Amagasaki City, Hyogo Prefecture             Amagasaki Research Center, Paper Manufacturing Co., Ltd. (72) Inventor Terunobu Fukui             Prince, 3-3-1, Jokoji Temple, Amagasaki City, Hyogo Prefecture             Amagasaki Research Center, Paper Manufacturing Co., Ltd. F-term (reference) 4L055 AA03 AC06 AC09 AG11 AG12                       AG27 AG47 AG48 AG63 AG73                       AG76 AG89 AG97 AG99 AH01                       AH02 AH09 AH16 AJ04 BE08                       EA11 EA16 EA17 FA30 GA19

Claims (5)

[Claims] 1. A coated paper for printing wherein a coating layer containing a pigment and an adhesive as a main component is provided on at least one side of a base paper, and a mixture of an organic substance and white inorganic particles is carbonized as the pigment, and then, A regenerated pigment produced by whitening a charcoal-based material obtained by carbonization, having a BET specific surface area of 15 to 30 m ² / g, and a whiteness (JIS Z8722).
The coated paper for printing is characterized by containing a recycled pigment of 60 to 90%). 2. The regenerated pigment comprises a mixture of an organic substance and white inorganic particles, which is subjected to a poor oxygen condition in which the presence of an oxygen-containing gas is restricted.
A step of carbonizing at a temperature of 1000 ° C. or lower, and then a carbide obtained by the carbonizing treatment at a temperature of 450 ° C. to 1000 ° C.
The coated paper for printing according to claim 1, which is a pigment produced by a whitening treatment step of decarbonizing in the presence of an oxygen-containing gas controlled to oxidize in the range of ° C. 3. The regenerated pigment has a median diameter of 0.1 to 5 μm.
The coated paper for printing according to claim 1 or 2, which is a pigment pulverized so that 4. Whiteness of base paper (according to ISO2470)
The absolute value of the difference between the whiteness (according to JIS Z8722) of all pigments constituting the coating layer containing the regenerated pigment is within 10 points, The printing according to any one of claims 1 to 3. Coated paper. 5. The coated paper for printing according to any one of claims 1 to 4, wherein the mixture containing an organic substance and white inorganic particles is at least one kind of waste mainly composed of papermaking sludge or waste paper.