WO2013005756A1

WO2013005756A1 - Method for producing white pigment, white pigment produced by the method, and high-grade paper comprising said white pigment

Info

Publication number: WO2013005756A1
Application number: PCT/JP2012/067039
Authority: WO
Inventors: 五十一川口; 幸一郎川口
Original assignee: 五條製紙株式会社
Priority date: 2011-07-06
Filing date: 2012-07-04
Publication date: 2013-01-10
Also published as: TWI466958B; TW201305281A; JP2013014726A; JP4878657B1

Abstract

Provided is a method for producing a white pigment, comprising a first step of burning a sludge at 600-800˚C to produce paper-making sludge ashes, a second step of adding an aluminum processing sludge to the paper-making sludge ashes or adding the paper-making sludge ashes to the aluminum processing sludge, and subsequently adding/mixing water to/with the water-added mixture and then subjecting the resultant mixture to a hydrothermal reaction to produce a slurry-like material or, alternatively, adding/mixing water to/with the resultant mixture to produce a slurry-like material without a hydrothermal reaction, and a third step of subjecting the slurry-like material to a wet milling procedure to produce the white pigment. The method enables the production of a white pigment having a whiteness degree of 80% or more, which is a whiteness degree required for high-grade paper, at low production cost using PS and AS as raw materials.

Description

White pigment production method, white pigment produced by the production method, and high-grade paper using the white pigment

The present invention relates to a method for producing a white pigment from two types of industrial waste, a white pigment produced by the production method, and a high-grade paper using the white pigment, and more specifically, two types of industrial waste A white pigment using a paper sludge and an aluminum sludge as a raw material, a white pigment as a papermaking filler or a coating pigment produced by the production method, and a papermaking filler or a coating pigment The present invention relates to high-grade paper using a white pigment.

In recent years, a shift to a resource recycling industrial structure has been desired from the viewpoint of environmental protection, and a countermeasure for reusing paper sludge (hereinafter referred to as “PS”) is also desired in the paper manufacturing industry. PS is an excess sludge that has been discharged without being used in inorganic particles such as pulp fibers and white pigment, which are contained in the wastewater in the papermaking process. Although this PS may be reused as an iron-forming forming agent or cement extender after combustion, most of it is still disposed of by landfill treatment. The burden of expenses for this disposal process is enormous. In addition, tightness of the final disposal site is also an issue, and PS reuse is urgently desired.
On the other hand, as in the paper manufacturing industry, a countermeasure for reusing aluminum processing sludge (hereinafter referred to as “AS”), which is a waste liquid for surface treatment of aluminum products, is also desired in the aluminum processing industry. AS is sludge that is agglomerated and agglomerated of an aluminum-containing waste liquid produced in the aluminum surface treatment step. As an AS disposal method, AS is incinerated and discarded as incinerated ash, or AS is not incinerated, but is mixed with other incinerated ash and discarded. The problem of disposal processing of this AS is becoming serious, and the burden of expenses for this disposal processing is great. Thus, attempts have been made to reduce the amount of waste by dehydrating and drying AS, dissolving it, reusing it as an aluminum raw material, wastewater treatment chemicals, etc., and the reuse of AS is urgently desired.
Therefore, with regard to PS, PS can be reused as a white pigment for papermaking and coating pigments, and AS can be reused as zeolite for reducing industrial waste and Many studies have been proposed to reduce the amount of raw materials used.

Patent literature relating to a method for producing a white pigment of PS is described below.
Production in which unburnt organic residue generated when baking PS significantly reduces the whiteness of paper sludge ash (hereinafter referred to as “PS ash”), and thus achieves high whiteness by performing an oxidation process in multiple stages. A method has been proposed (see Patent Document 1). Further, a manufacturing method has been proposed in which papermaking sludge is fired while forcibly removing the unburned organic residue with a fan (see Patent Document 2). When the temperature of the PS becomes too high when the PS is fired, the hardness of the white pigment to be produced increases, and it has been pointed out that there is an adverse effect on the degree of wire wear in the pulverization process and papermaking process. There has been proposed a production method in which a calcium hydroxide aqueous solution is added to a suspension and mixed, and carbon dioxide is blown and light calcium carbonate is deposited on the surface of PS ash (see Patent Document 3). Furthermore, after the PS ash is added to the aluminum sulfate aqueous solution and mixed, it is contacted with carbon dioxide to produce calcium trisulfoaluminate to produce inorganic particles (see Patent Document 4). A method for producing a high whiteness PS ash in which a compound is added and heat treated to increase whiteness has been proposed (see Patent Document 5).

As a patent document relating to a method for producing AS zeolite, it is reported that a production method for producing zeolite from AS generated by anodizing treatment, and that the produced zeolite can be used for applications such as detergent builders and various fillers. In addition, there is a manufacturing method in which an aqueous alkali solution is added to AS to form a slurry by adding zeolite to AS, and the manufactured zeolite is used as, for example, a concrete additive, an adsorbent, a soil improver, etc. It has been reported that it can be used (see Patent Document 7). Furthermore, a production method for producing zeolite using coal ash, which is waste, as a main raw material and using an SiO ₂ source or an Al ₂ O ₃ source as a secondary raw material, has been reported. As the secondary raw material, Al ₂ O ₃ such as AS is used. It has been reported that industrial wastes are included, and that the produced zeolite can be used in large quantities in large-scale fields such as agricultural soil improvement and drainage water purification (see Patent Document 8).
However, in the paper manufacturing industry, it was an urgent task to recycle PS, so no attempt was made to produce white pigments using AS in the aluminum processing industry, and PS and AS were used. No report has been made on the production method of white pigments.

JP 2001-026727 A JP 2008-001591 A JP 2002-233851 A JP 2007-106654 A JP 2003-278092 A JP 11-314912 A JP 2006-044978 A Japanese Patent Laid-Open No. 2004-224687

The white pigment obtained by the above-described conventional production method requires a lot of cost and energy, so the production cost is high, and it can be used as a paper filler or coated paper pigment on high-grade paper. However, since the whiteness of the white pigment is low, the required blending ratio must be considerably suppressed, and there is a problem that the whiteness required for high-grade paper cannot be obtained. The whiteness of the white pigment used for high-grade paper needs to be 80% or higher.
Furthermore, when PS is baked, the inorganic pigment in PS melts at a high temperature and the hardness becomes very high, which adversely affects the pulverization process and wire wear, and many of them do not reach the quality as papermaking materials. .
And as mentioned above, as a processing method for discarding the current PS, dehydration and baking are performed in the hope of reducing the volume, and most of the discharged PS ash is landfilled. The burden of is great. Only a part of the waste is reused by blending it with a forming agent for steel making, a cement extender, and a soil conditioner, and no technology that can recycle 100% PS has been developed. Also, the current disposal method of AS is incinerated and discarded as incinerated ash, or AS is not incinerated, but is mixed with other incinerated ash and disposed of. The burden is enormous, and a method for producing a white pigment produced using AS as a raw material has not been known to date.

Therefore, the present invention has the above-mentioned problems of the prior art, the high production cost of white pigments produced from PS, the low whiteness of high-grade paper, and the cost of disposal of PS. Considering the great burden, the production cost can be reduced by using PS and AS as raw materials, the white pigment having a whiteness of 80% or more necessary for high-quality paper can be obtained, and the cost for disposal of PS can be reduced. It is an object of the present invention to provide a production method for producing a white pigment that can be eliminated, a white pigment that is a white pigment for papermaking and coating produced by the production method, and a high-grade paper using the white pigment. .

In order to increase the whiteness of the white pigment obtained by reusing PS, the present inventor added PS, which is mainly composed of aluminum hydroxide and caustic soda, and then mixed with water. Stir and hydrothermally react to make a slurry, or add water to mix and stir to make a slurry without hydrothermal reaction, and the white pigment obtained by wet pulverization of the slurry is white The present invention was completed by finding that the degree was 80% or more.
The method for producing a white pigment of the invention according to claim 1 is a method for producing a white pigment using papermaking sludge as a raw material, wherein the sludge is calcined at 600 to 800 ° C. to obtain papermaking sludge ash, After adding the aluminum sludge to the paper sludge ash, or after adding the paper sludge ash to the aluminum sludge, add water and mix and stir to hydrothermal reaction to make a slurry, or add water and mix It is characterized by comprising a second step of stirring to make a slurry without hydrothermal reaction, and a third step of wet grinding the slurry to make a white pigment.
In the method for producing a white pigment according to the second aspect of the present invention, the ratio of adding the aluminum processing sludge to the papermaking sludge ash, or the ratio of adding the papermaking sludge ash to the aluminum processing sludge is based on the sludge total weight solids. The aluminum processing sludge is 20 to 80%.
The method for producing a white pigment of the invention according to claim 3 is characterized in that the hydrothermal reaction in which the water is added and stirred to form a slurry is mixed and stirred at a temperature of 85 to 95 ° C. for 1 to 4 hours. To do.
The white pigment production method of the invention according to claim 4 is characterized in that a part of the slurry is made of a zeolitic component.
The method for producing a white pigment of the invention according to claim 5 is characterized in that the aluminum-processed sludge is mainly composed of aluminum hydroxide and caustic soda or caustic potash.
The method for producing a white pigment of the invention according to claim 6 is characterized in that after the second step, a step of removing unreacted alkali content of the slurry-like material by washing with water is provided.
A white pigment according to a seventh aspect of the present invention is manufactured by the white pigment manufacturing method according to any one of the first to sixth aspects.
The white pigment of the invention according to claim 8 is characterized in that the zeolitic component according to claim 4 carries sodium or potassium in the component.
The high-grade paper of the invention according to claim 9 is characterized in that the white pigment according to claim 7 is used as a filler for papermaking.
The high-grade paper of the invention according to claim 10 is characterized in that the white pigment according to claim 7 is used as a coating pigment on the paper surface.

The method for producing a white pigment according to the present invention enables recycling of cheaper and more stable PS and AS as a white pigment, thereby reducing the production cost, and the whiteness of 80% or more required for high-quality paper. A white pigment having a water content can be obtained, and the cost for disposal treatment of PS can be eliminated, and the amount of treated sludge to be landfilled can be further reduced.
The white pigment produced by the method for producing a white pigment of the present invention maintains a whiteness of 80% or more required for high-quality paper, and when used as a paper filler, it is a high-grade expensive filler used conventionally. Can be an alternative to talc. In addition, due to partial zeolitization by alkaline hydrothermal reaction, the whiteness increased from the white pigment before the reaction, the paper density decreased and the paper became bulky, and the opacity increased. In addition, when used as a pigment for paper coating, it is possible to replace calcium carbonate, which is a white pigment that has been used in the past. As a result, the ink setting property can be improved while maintaining the printing gloss.
Since the white pigment of the present invention has a whiteness of 80% or more required for high-grade paper, it can be used as a high-grade paper pigment.

PS is used as a raw material that has been subjected to precipitation treatment by known methods such as coagulation sedimentation and activated sludge process for wastewater discharged from each process such as pulping, papermaking, coating, and used paper recycling. can do.
A method for drying and firing the recovered PS is not particularly limited, but a fluidized bed, a stoker furnace, a rotary kiln, or the like can be used. Above all, the firing temperature of the sludge in the heating furnace can be made uniform, unburned organic residue is not generated as much as possible, the equipment maintenance is as simple as possible, the driving energy is low, and the cost performance is high. It is preferable to use a rotary kiln.

If the firing temperature of PS is low, unburned organic residue is produced and the whiteness is lowered. If the firing temperature is high, the hardness of the fired product is increased, which not only hinders the subsequent grinding process, but also affects the degree of wire wear. As the quality becomes lower. Further, the energy cost for maintaining the combustion temperature is excessive, which is not preferable. That is, an unburned organic residue is generated at a temperature of 500 ° C. or lower, and the whiteness of the fired product to be produced is lowered. On the other hand, at a temperature of 900 ° C. or higher, the pigment surface partially melts and a hard fired product is generated. Therefore, the firing temperature of the present invention is preferably 600 ° C. or higher and 800 ° C. or lower, and more preferably 650 ° C. or higher and 750 ° C. or lower.

The method for producing a white pigment according to the present invention includes a step of adding AS to PS ash in order to increase the whiteness of a papermaking pigment made from PS ash. AS does not specifically limit the sludge generation process, but it is a large amount of sludge discharged from an aluminum processing factory and generated as a result of alkaline cleaning of the aluminum surface or of alkaline cleaning waste liquid from the surface of the aluminum extrusion factory die. The waste is disposed without being reused, and the waste liquid and the precipitated sludge are preferable from the viewpoint of effective use of waste. Further, the precipitated sludge is mainly composed of aluminum hydroxide and also contains caustic soda used for cleaning. This caustic soda is also a component necessary for the alkaline hydrothermal reaction described later. The addition ratio of PS ash and AS is added so that AS becomes 20 to 80% with respect to the sludge total weight solid content, and dispersed in water. At that time, the whiteness of the white pigment increases as the AS increases, but the PS ash is not effectively used. Therefore, it is preferably 25 to 75%, more preferably 45 to 55%.

The PS ash / AS additive may proceed to the wet pulverization process as it is, but a part of the PS ash / AS additive may be zeoliteized through a hydrothermal process. As the conditions for the zeolite hydrothermal process, it is preferable to carry out the reaction under a generally known alkaline condition at a temperature of 85 to 95 ° C. for 1 to 4 hours, and the formation of porous particles by zeolitization is expected. .
In addition, potassium chloride may be added as a zeolitic reaction accelerator. Thus, when used as a filler for paper, not only whiteness but also increased opacity and bulkiness can be expected, and when used as a coating pigment, an improvement in printing ink set can be expected. When PS ash is low in silica and zeoliticization cannot be expected at all, water glass (sodium silicate), silica ash and fine silica sand (discharged from the glass production process) are used as silica supplements. Waste), rice husk incineration ash, and the like may be added during the baking of PS.

For the wet pulverization step of the present invention, the pulverization method is not particularly limited, but a wet ball mill, vibration mill, stirring tank type mill, flow tube type mill, coball mill, homogenizer, etc. can be used, and finally paper When used as a filler, it is pulverized to have an average particle size of 1.0 to 20.0 μm, and when used as a coating pigment, it is finely pulverized to have an average particle size of 0.1 to 2.0 μm. . By the way, when it is used as a filler, if it is attempted to obtain a particle size of less than 1.0 μm, the yield during paper making is poor, and if the particle size is 20 μm or more, there is a possibility of causing poor adhesion and poor appearance. When it is used as a coating pigment, if it is intended to obtain a particle size smaller than 0.1 μm, it takes a long processing time and a lot of energy is required. Moreover, if the particle diameter is 2.0 μm or more, there is a possibility of causing poor appearance such as poor smoothness.
In addition, you may add a water-washing process as needed in order to remove an unreacted alkali content before a wet grinding process.

Examples are shown below, but these examples show one example of the present invention, and the present invention is not limited in any way by the following examples.
(Comparative example)
(Paper sludge combustion temperature)
Conventionally, white pigments for plain paper have been manufactured using PS ash that has been baked for about 30 minutes at a temperature of 500-900 ° C in a rotary kiln. Therefore, white pigments are manufactured at the following three firing temperatures. This example was used as a comparative example.
(Comparative Example 1)
For PS, wastewater discharged from the paper mill of Gojo Paper Co., Ltd. was precipitated, concentrated and dehydrated by the coagulation sedimentation method. This PS was baked for 30 minutes at a baking temperature of 700 ° C. in an electric external heat rotary kiln.
(Comparative Example 2)
The same PS as in Comparative Example 1 was used, and this PS was baked for 30 minutes at a baking temperature of 500 ° C. in an electric external heat rotary kiln. At first glance, the PS ash after firing had unburned residue and was in a state of low whiteness.
(Comparative Example 3)
The same PS as in Comparative Example 1 was used, and this PS was baked at an calcination temperature of 900 ° C. for 30 minutes in an electric external heat rotary kiln.

(Example)
In Examples 1-1 to 3-2, PS ash of Comparative Examples 1 to 3 was coarsely pulverized with a homogenizer (IKA Works Magic Lab) so that the average particle size was about 50 μm at 30% concentration. Example 1-1, Example 2-1 and Example 3-1 are examples in which a hydrothermal reaction is performed, and Example 1-2, Example 2-2 and Example 3-2 are examples of hydrothermal reaction. This is an example in which no reaction is performed.
Example 1-1
Using the coarsely pulverized PS ash of Comparative Example 1, AS (aluminum sludge discharged from Furukawa Sky Co., Ltd.) was added so as to be 25% with respect to the sludge total weight solid content, and the solid content was 30%. It was made to disperse | distribute to water. The Si / Al ratio at that time was 0.87. Thereafter, for alkaline hydrothermal reaction, the mixture is held at 90 ° C. for 3 hours with stirring, and after the slurry is treated so that a part of the slurry becomes a zeolitic component, the slurry is wet pulverized to give white A pigment was produced.
As a result of analysis, the AS used was 47.2% aluminum hydroxide, 10.2% sodium hydroxide, 86.5% whiteness, and an average particle size of 1.5 μm.

Example 2-1
The PS ash that was coarsely pulverized in Comparative Example 1 was used, and AS in Example 1 was added to 50% of the sludge total weight solids, and dispersed in water so that the solids would be 30%. The Si / Al ratio at that time was 0.5. Thereafter, for alkaline hydrothermal reaction, the mixture is held at 90 ° C. for 3 hours with stirring, and after the slurry is treated so that a part of the slurry becomes a zeolitic component, the slurry is wet pulverized to give white A pigment was produced.
Example 3-1
The PS ash that was coarsely pulverized in Comparative Example 1 was used, and AS in Example 1 was added to 75% of the sludge total weight solids, and dispersed in water so that the solids would be 30%. The Si / Al ratio at that time was 0.2. Thereafter, for alkaline hydrothermal reaction, the mixture is held at 90 ° C. for 3 hours with stirring, and after the slurry is treated so that a part of the slurry becomes a zeolitic component, the slurry is wet pulverized to give white A pigment was produced.

Example 1-2
Using the coarsely pulverized PS ash of Comparative Example 1, the AS of Example 1 was added to 25% of the sludge total weight solid content, and water was added and dispersed so that the solid content was 30%. After the slurry was formed, the white pigment was produced by wet pulverizing the slurry without hydrothermal reaction.
(Example 2-2)
Using the coarsely pulverized PS ash of Comparative Example 1, the AS of Example 1 was added to 50% of the sludge total weight solid content, and water was added to disperse the solid content to 30%. After the slurry was formed, the white pigment was produced by wet pulverizing the slurry without hydrothermal reaction.
(Example 3-2)
Using the coarsely pulverized PS ash of Comparative Example 1, the AS of Example 1 was added to 75% of the sludge total weight solid content, and water was added and dispersed so that the solid content was 30%. After the slurry was formed, the white pigment was produced by wet pulverizing the slurry without hydrothermal reaction.

Table 1 summarizes the manufacturing conditions of the comparative example and the example described above.

The silica-alumina ratio (Si / Al ratio) of PS ash of Comparative Example 1 was 2.10 as a result of analysis (measured by Fuji Inspection Center Co., Ltd.).
At first glance, the PS ash after firing in Comparative Example 2 had an unburned residue and had a low whiteness.
In Comparative Example 3, although whiteness was improved as compared with Comparative Example 1, the combustion particles were coarse and yellowish.

(Confirmation of zeolite component)
A part of the slurry obtained by the hydrothermal reaction contains a zeolite component, and the silica / alumina ratio is smaller than 1, so that it is expected to produce A-type zeolite supporting sodium.
In order to confirm the zeolite component, the white pigment after alkaline hydrothermal reaction was washed with pure water repeatedly. After the sodium content was not detected, nitric acid was added to break the zeolite and analyze the supported sodium. In all of Examples 1-1 to 3-1, a sodium content was detected (Fuji Inspection Center Co., Ltd.). In addition, when potassium hydroxide is used for the cleaning liquid in the aluminum processing step and potassium chloride is used as a zeolitic reaction accelerator, a zeolite carrying potassium having a higher ionization tendency than sodium is produced.

(Whiteness of white pigment)
The white pigments of Comparative Examples 1 to 3 and the slurry materials of Examples 1-1 to 3-1 and Examples 1-2 to 3-2 were wet pulverized to produce white pigments.
The wet pulverization was performed using a wet ball mill using zirconia beads as a medium (WANO Dynomill KDL) so that the average particle size was about 10 μm. Thereafter, the whiteness of each white pigment was measured.
(Measurement of whiteness)
The whiteness was measured according to a spectral color whiteness meter (PF10 manufactured by Nippon Denshoku Industries Co., Ltd.) and “Measurement method of ISO whiteness (diffuse blue light reflectance)” of JIS P8148.
The particle diameter was measured with a laser diffraction particle measuring instrument (LA-500 manufactured by Horiba, Ltd.).

An uncoated paper was prepared as follows using the white pigment of the present invention as a filler for papermaking.
First, LBKP adjusted to Freeness 300CC (Canadian standard freeness) is used as a raw material pulp, and 0.5 parts by mass of rosin sizing agent, 1.0 part by mass of cationized starch, and a sulfate band per 100 parts by mass of pulp. Of 1.0 part by mass was added to obtain a pulp slurry.
The white pigments of Comparative Examples 1 to 3, the white pigments of Examples 1-1 to 3-1 and Examples 1-2 to 3-2, and titanium dioxide (TA100 manufactured by Fuji Titanium Industry Co., Ltd.) as a comparison. , Adding 10 parts by weight of talc (Toyo Kasei Co., Ltd.), and using a round sheet machine (manufactured by Tester Sangyo Co., Ltd.) to create a handsheet to a basis weight of 100 g / m ² did.

(Measurement and evaluation of uncoated paper)
The whiteness was measured according to the above-mentioned spectral color whiteness meter (PF10 manufactured by Nippon Denshoku Industries Co., Ltd.), JIS P 8148 “Measurement method of ISO whiteness (diffuse blue light reflectance)”. In the evaluation, 80 or more was marked with ◯, 70 or more and less than 80 was marked with Δ, and less than 70 was marked with x.
The opacity was measured using a Hunter whiteness meter (TR-600, manufactured by Tokyo Denshoku Co., Ltd.), Japan Tape No. It was measured according to 69 “Paper-Hunter Opacity Test Method”.
The density is measured by measuring the paper basis weight (g / m ² ) and the paper thickness (μm). The paper basis weight (g / m ² ) ÷ paper thickness (μm) = density (g / cm ³ ) Calculated as In the evaluation, a mark having a lower density (bulkyness) than talc or titanium dioxide, which is generally used as a filler, was marked with a circle.

Table 2 shows the results obtained by measuring the non-coated paper and the evaluation results.
In addition, the value shown in the following table | surfaces is calculated | required by the arithmetic average by setting the number of samples to N = 3.

Table 2 shows that the density of Examples 1-1 to 3-1 is lower than that of talc and titanium dioxide, and is bulky. In addition, the opacity of Examples 1-1 to 3-2 is similar to that of talc and titanium dioxide. In particular, the whiteness of the white pigments of the examples is as high as 80% or more compared to the comparative examples. The whiteness of the non-coated papers of Examples 1-1 to 3-2 was as high as 80% or more compared to the comparative example, and Examples 3-1 and 3-2 showed the same whiteness as talc. ing.

(Preparation of coated paper)
The white pigments obtained by wet-grinding the white pigments of Comparative Examples 1 to 3 and the slurries of Examples 1-1 to 3-1 and Examples 1-2 to 3-2 were applied to high-grade paper. Coated paper was prepared as a pigment.
For the wet pulverization, a wet ball mill using zirconia beads as media (Dynomill KDL from WAB) was used, and the average particle size was about 1 μm.
Regarding Comparative Example 3, because of its high hardness, it could not be finely pulverized to about 1 μm, and the evaluation of the coating pigment was stopped.
As a comparison, Ca carbonate (Carbital 90, manufactured by Imeris Co., Ltd.), which is a general coating pigment, was also performed.
Create a paint with the following composition on high-quality paper 81.4g / m ² (manufactured by Oji Paper Co., Ltd.) and apply it with a bar coater to a coating amount of 20g / m ^2. I passed through the calendar.

Coating liquid blended Ca carbonate (Carbital 90, manufactured by Imeris Co., Ltd.) 20 parts Ca carbonate (NS2300, manufactured by Nitto Flour Industry Co., Ltd.) 20 parts Ca carbonate (TP123, manufactured by Okutama Kogyo Co., Ltd.) 10 parts Kaolin ( Astra Coat, manufactured by Imeris Co., Ltd.) 25 parts White pigment (Example, Comparative Example) 25 parts Latex (Smartex, manufactured by Nippon A & L Co., Ltd.) 12 parts Starch (MS4600, manufactured by Nippon Food Chemical Co., Ltd.) 2 parts Lubricant (SN Coat 204, manufactured by San Nopco Co., Ltd.) 0.5 part Printability agent (PA646NF, manufactured by Seiko PMC Co., Ltd.) 0.5 part Dispersant (Aron T-50, manufactured by Toagosei Co., Ltd.) Trace amount Defoaming agent (SN deformer, San Nopco)

(Measurement and evaluation of coated paper)
The whiteness was measured according to a spectral color whiteness meter (PF10 manufactured by Nippon Denshoku Industries Co., Ltd.) and “Measurement method of ISO whiteness (diffuse blue light reflectance)” of JIS P8148. In the evaluation, 80 or more was marked with ◯, 70 or more and less than 80 was marked with Δ, and less than 70 was marked with x.
The glossiness of the blank paper was measured according to a gloss meter (Nippon Denshoku Industries Co., Ltd., VGP5000), JIS P 8142 “Paper and paperboard—Measurement method of 75 ° specular gloss”.

(RI printing tester evaluation method)
0.4 cc of oil-based offset printing ink “TK High Unity SOY Ai (made by Toyo Ink Manufacturing Co., Ltd.)” is kneaded with a rubber roll for 1 minute and printed at a rotation speed of 40 rpm. In some cases, the printed gloss after drying for 24 hours is measured in the same manner as the above-mentioned white paper glossiness, and in part, the printed surface is transferred to white paper before drying, and the cyan density of the transferred ink is measured by Macbeth reflection densitometer ( Ink setability was evaluated by measuring with a Japanese lithographic equipment (X-Rite 404). The ink setting property was better when the density (optical density: OD value) was lower, and a value less than 0.2 was marked with a circle.

Table 3 shows the results obtained by measuring the coated paper and the evaluation results.
In addition, the value shown in the following table | surfaces is calculated | required by the arithmetic average by setting the number of samples to N = 3.

From Table 3, the whiteness of the coated papers of Examples 1-1 to 3-2 is higher than that of 80.2 of Comparative Example 1, and Example 3-1 has the same degree as Ca carbonate. It indicates whiteness. The OD values of the ink sets of Examples 1-1 to 3-1 are lower than those of Ca carbonate, indicating that they are excellent.

Claims

A method of producing a white pigment from papermaking sludge,
A first step of calcining the sludge at 600 to 800 ° C. to produce papermaking sludge ash;
Add aluminum processing sludge to the papermaking sludge ash, or add the papermaking sludge ash to the aluminum processing sludge, then add water and mix and stir to hydrothermal reaction to make slurry, or add water and mix and stir A second step of making a slurry without hydrothermal reaction;
A third step of wet-grinding the slurry to obtain a white pigment;
A method for producing a white pigment, comprising:
The ratio of adding the aluminum-processed sludge to the papermaking sludge ash or the ratio of adding the papermaking sludge ash to the aluminum-processed sludge is 20 to 80% of the aluminum-processed sludge with respect to the total sludge solid weight. The method for producing a white pigment according to claim 1.
The method for producing a white pigment according to claim 1 or 2, wherein the hydrothermal reaction in which water is added and stirred to form a slurry is mixed and stirred at a temperature of 85 to 95 ° C for 1 to 4 hours. .
4. The method for producing a white pigment according to claim 3, wherein a part of the slurry is made of a zeolitic component.
The method for producing a white pigment according to any one of claims 1 to 4, wherein the aluminum-processed sludge contains aluminum hydroxide and caustic soda or caustic potash as main components.
The method for producing a white pigment according to claim 5, wherein a step of removing unreacted alkali content of the slurry-like material by washing with water is provided after the second step.
A white pigment produced by the method for producing a white pigment according to any one of claims 1 to 6.
A white pigment, wherein the zeolitic component according to claim 4 carries sodium or potassium in the component.
A high-grade paper, wherein the white pigment according to claim 7 is used as a filler for papermaking.
A high-grade paper, characterized in that the white pigment according to claim 7 is used as a coating pigment on the paper surface.