JP2003049389A - Method for producing composite particle and method for producing loading material-added paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a bulky loading material improving yielding percentage, capable of expressing bulkiness with a little pulp without inhibited interfiber bondings caused by loading material particles distributed among the fibers and simultaneously improving whiteness and opacity and provide loading material-added paper. SOLUTION: Inorganic fine particle-silica composite particles are produced by adding and dispersing the inorganic particles in an aqueous alkali silicate solution to prepare a slurry, subsequently heating and agitating the slurry and adding an acid while keeping the temperature of the slurry at 60-100 deg.C to produce a silica sol and adjusting the pH of the final reaction solution in the range of a neutral to a weak alkaline value. Paper is produced by adding the same as a loading material inside a pulp slurry.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing a composite filler and a method for producing a paper in which a filler is internally added. Particularly, the bulkiness, the whiteness and the opacity are high, and the decrease in paper strength due to the internal addition of the filler occurs. The present invention relates to a method for producing a filler-containing paper with a small amount and a high filler yield.

[0002]

2. Description of the Related Art In recent years, it has been required to reduce the weight of paper from the viewpoint of protection of forest resources, resource conservation, and reduction of environmental load including garbage. When aiming to reduce the weight of paper, especially in the fields of printing paper, wrapping paper, etc., various fillers are internally added and manufactured in order to improve whiteness, opacity and printability. Conventionally, as a method of improving whiteness and opacity of paper by internally adding fillers, a method of internally adding fillers having a large refractive index such as titanium dioxide to increase scattering efficiency and white clay, talc, calcium carbonate, organic pigments, etc. A method of internally adding a filler having a refractive index of around 1.5 to suppress the adhesion between pulp fibers and increase the scattering surface area is adopted.

Further, in order to cope with the weight reduction of paper, methods such as simply lowering the basis weight or increasing the ratio of deinking pulp have been used so far. However, according to this method, the paper becomes thin, the whiteness and opacity are lowered, and the printability such as strike-through deteriorates. Opacity and strike-through are closely related to the thickness of the paper, and thus far, bulky paper has been manufactured by using excess pulp or bulky pulp.

[0004]

However, most of the fillers such as calcium carbonate having a small particle size as described above flow out into white water during papermaking and have a problem that they are very poorly retained in the paper layer. It was Further, such small filler particles are distributed between pulp fibers, which impedes binding between fibers and reduces paper strength.

The object of the present invention is to improve the yield of the filler, and to prevent the interfiber bond from being hindered by the filler particles distributed between the fibers, so that even a small amount of pulp can be made bulky.
"Light and thick paper" that can improve whiteness and opacity at the same time
It is to provide a method for producing a bulky filler and a filler-added paper that can be produced.

[0006]

[Means for Solving the Problems] The above-mentioned problems are solved by adding and dispersing inorganic fine particles in an aqueous alkali silicate solution to prepare a slurry, and then stirring while heating and maintaining the liquid temperature in the range of 60 to 100 ° C. to add an acid. , Silica sol was generated, and the pH of the final reaction solution was adjusted to be in the neutral to weakly alkaline range to produce inorganic fine particles / silica composite particles, which was internally added as a filler to the pulp slurry.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, silica sol fine particles of about several nm, which are produced by adding an acid such as dilute sulfuric acid to a sodium silicate solution, are thinly adhered to the entire surface of the inorganic fine particles, and the silica sol crystal growth is accompanied. A bond is formed between the silica sol fine particles on the surface of the inorganic fine particles and the silica sol fine particles on the surface of another inorganic fine particle to form an aggregate of the inorganic fine particle / silica composite particles.

For this reason, the pH of the final reaction solution is an important factor, and the pH is set in the range of neutral to weakly alkaline so that hydrated silicic acid (white carbon) is not generated in the reaction system.
It is necessary to control H. The preferred pH is in the range 8-11. If sulfuric acid is added until the pH is less than 7 and acidic condition is added, white carbon is generated instead of silica sol, and the white carbon surrounds the aggregate of inorganic fine particles in a spherical shape. The optical characteristics appear preferentially, and the optical characteristics of the inorganic fine particles in the core are not exhibited at all. p
When H exceeds 11, the production of silica sol is insufficient and it is difficult to obtain an aggregate of the inorganic fine particle / silica composite of the present invention.

The silica sol produced during the reaction in the present invention is prepared by using sodium silicate (water glass) as a raw material and sulfuric acid,
Particle size 10 to 20 obtained by hydrolysis reaction and polymerization of silicic acid by reacting with dilute solution of mineral acid such as hydrochloric acid and nitric acid at high temperature
nm silica sol particles.

The alkali silicate solution used in the present invention is not particularly limited, but a sodium silicate solution (No. 3 water glass) is preferable in terms of availability. The concentration of the silicic acid alkali solution is preferably 3 to 10% by weight in terms of silicic acid content (SiO2 conversion) in the aqueous solution. When the content exceeds 10% by weight, the composite formed is not an inorganic fine particle / silica composite aggregate, but the above inorganic fine particles are encapsulated with white carbon, and the optical characteristics of the inorganic fine particles in the core are not exhibited at all. . On the other hand, if the amount is less than 3% by weight, the amount of silica component in the composite particles decreases, and it becomes difficult to form aggregate particles.

The inorganic fine particles used in the present invention include:
Examples thereof include light calcium carbonate, heavy calcium carbonate, talc, kaolin, clay, calcined kaolin, titanium dioxide, aluminum hydroxide, etc., which are fillers for papermaking. The particle size, considering the particle size of the composite aggregate particles to be formed, 0.
05-50 microns is desirable.

Since these inorganic fine particles have a function as a dispersant in the sodium silicate solution, they are used after being dispersed in the sodium silicate solution in advance. However, if the dispersibility of the particles is not good at the time of dispersion, the filler may be dispersed in water containing a dispersant, and then the sodium silicate solution may be added later. In particular, since titanium dioxide has a small particle size and easily aggregates, it is preferable to use a dispersant. Examples of the dispersant include sodium hexametaphosphate, sodium pyrophosphate, sodium polycarboxylate and the like.

The above-mentioned inorganic fine particles may be used alone, but it is also possible to produce a highly functional composite filler by using two or more kinds of inorganic fine particles in combination.

Examples of the acid used in the present invention include dilute sulfuric acid, dilute hydrochloric acid, dilute solutions of mineral acids such as dilute nitric acid, acetic acid, carbon dioxide and the like, but dilute sulfuric acid is most preferable in terms of price and handling. Further, when dilute sulfuric acid is used, the concentration at the time of addition is preferably 0.2 to 1.0 molar.

The reaction temperature during the production of the inorganic fine particle / silica composite particles in the present invention is preferably in the range of 60 to 100 ° C. The reaction temperature affects the formation of silica sol, the crystal growth rate, and the mechanical strength of the formed inorganic fine particle / silica composite aggregate particles. When the reaction temperature is less than 60 ° C, the formation and growth rate of silica sol is slow, and the bond strength of the formed inorganic fine particles / silica composite aggregate particles is weak, so the aggregate tends to break due to the high shear that occurs during the papermaking process of the paper with filler inside. . Ten
If the temperature exceeds 0 ° C, the reaction process is complicated because an autoclave must be used because it is a water-based reaction. The optimum reaction temperature is 70-90 ° C.

Further, in the case of producing inorganic fine particles / silica composite particles, the inorganic fine particles are added and dispersed in an alkali silicate aqueous solution to prepare a slurry, and the slurry concentration is 3 to 3
5% by weight is desirable. By adjusting the slurry concentration, the particle size of the formed inorganic fine particle / silica composite aggregate particles is controlled, and at the same time, the composition ratio of the inorganic fine particles and silica is determined.

Further, the yield of the filler can be increased by setting the average particle size of the inorganic fine particle / silica composite aggregate particles to a large particle size of 10 to 60 microns. The following three methods can be mentioned as the method for controlling the particle size. The concentration of the filler slurry obtained by adding inorganic fine particles to an aqueous solution of alkali silicate having a concentration of 3.61% as the silicic acid content is 3.2.
~ 9.6% by weight. 2-10 with large particle size as raw material
Micron inorganic particles are used. The solid obtained by air-drying or heat-drying the slurry of the inorganic fine particle / silica composite aggregate particles is dry or wet pulverized. With the above method, it is possible to control the particle size to a size of 10 to 60 microns.

In the present invention, inorganic fine particles are added to and dispersed in an aqueous alkali silicate solution to prepare a slurry, and then the liquid temperature is maintained within the range of 60 to 100 ° C. with stirring to add an acid to form a silica sol. The pH of the reaction solution is adjusted to neutral to weakly alkaline, preferably in the range of 8 to 11 to produce inorganic fine particles / silica composite particles, and the slurry is filtered.
A wet cake is obtained by washing with water.

This wet cake is again dispersed in water to obtain a filler slurry, which is internally added to the pulp slurry at the time of papermaking to obtain a filler internally added paper. At this time, the wet cake of the inorganic fine particles / silica composite particles is air-dried or heat-dried to obtain dry fine particles, and then the dry slurry or wet pulverizer is used again to prepare the filler slurry having the particle diameter adjusted during the papermaking process. When the filler-added paper is internally added to the composition, the bulkiness, which is the effect of the present invention, can be dramatically improved. Examples of the wet pulverizer include known homomixers, homogenizers, and sand grinders.

In the present invention, as the known fillers, inorganic fillers such as clay, silica, talc, calcined kaolin, calcium carbonate and the like, or vinyl chloride resins, polystyrene resins, urea formalin resins, melamine-based fillers are used within the range not impairing the effects of the present invention. An organic filler produced from a resin or a synthetic resin such as a styrene / butadiene copolymer resin may be used in combination.

If necessary, a paper-strengthening agent such as polyacrylamide-based polymer, polyvinyl alcohol-based polymer, cationized starch, urea / formalin resin, melamine / formalin resin; acrylamide / aminomethylacrylamide copolymerization. Salts or cationized starch, polyethyleneimine, polyethylene oxide, acrylamide / sodium acrylate copolymer etc. drainage or retention aids; aluminum sulfate (sulfate band),
You may contain auxiliary agents, such as a water-proofing agent, a UV inhibitor, and an anti-fading agent.

[0022]

EXAMPLES The present invention will now be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In addition, in description, a percentage shows a weight percentage.

Bulkiness, whiteness, opacity, breaking length, and filler retention of the neutral high-quality papers produced in Examples and Comparative Examples were measured by the following methods. Bulkiness: Paper density was calculated from basis weight and paper thickness. The lower the density, the higher the bulkiness. -Measurement of whiteness: Whiteness was measured with a Hunter whiteness meter based on JIS P 8123. -Measurement of opacity: Opacity was measured using a Hunter reflectometer based on JIS P 8138. -Filler yield: 10 x 10 cm pieces of paper were cut from the handmade sheet (blank) that did not contain the filler and the handmade sheet that contained the filler, which was made in advance, and cut at 105 ° C.
× After drying for 3 hours, weigh the absolute dry weight. Next, the ash content contained in the sheet is obtained by baking this absolutely dried paper piece in an electric furnace at 575 ° C for 2 hours. The filler yield (%) was calculated by the following formula. Filler yield = {(sheet ash weight with filler / same dry weight-
Blank ash weight / absolute dry weight)} / filler mixture ratio × 100 ・ Rearing length: Determined by the following formula according to JIS P 8113. Breaking length = tensile strength / (width of test piece x basis weight of test piece) x 100
0 ・ Ash content: Based on JIS P 8128, the ashing temperature was 575 ℃. -Ratio of composite particles: The component ratio of the composite particles was measured by fluorescent X-ray analysis. A comprehensive quality evaluation was performed based on the above measurement results. The evaluation was made into the following three stages. ◎: Very good: Good ×: Inferior

<Synthesis Example 1> 30 g of powder of calcium carbonate (TP-121 manufactured by Okutama Kogyo Co., Ltd.) was added to 312 g of an aqueous solution of sodium silicate (3.61% as silicic acid content), and a homomixer was used to rotate at 20 rpm at 3000 rpm. The dispersion treatment was performed for 1 minute to prepare a calcium carbonate slurry. Next, this slurry was placed in a 1 L four-necked flask equipped with a stirrer, a temperature sensor, and a reflux condenser, and heated to 75 ° C. in an oil bath while stirring. Next, while maintaining the slurry in the container at 75 ° C., 276 g of 0.36 N sulfuric acid was dropped using a microtuning pump at a dropping rate of 1.53 ml / min for 3 hours to obtain calcium carbonate / silica composite agglomerated particles. . The pH of the reaction solution at this time is 10.3
Met. Furthermore, a wet cake of calcium carbonate / silica composite agglomerated particles was obtained by filtering with a No. 2 filter paper, washing with water, and filtering again. When a 50% volume average particle diameter was measured by a laser diffraction / scattering method using a particle size distribution measuring apparatus Mastersizer S (manufactured by Malvern Instruments Ltd.), the average particle diameter was 8 microns, and the ratio of calcium carbonate to silica was It was 70:30.

<Synthesis Example 2> Calcium carbonate / silica composite agglomerated particles were obtained in the same manner as in Synthesis Example 1, except that the powder of calcium carbonate (TP-121 manufactured by Okutama Kogyo Co., Ltd.) was changed to 70 g. . The pH of the reaction solution at this time was 10.2. The average particle size of the obtained calcium carbonate / silica composite agglomerated particles was 5.4 μm, and the ratio of calcium carbonate to silica was 86:14.

<Synthesis Example 3> The calcium carbonate / silica composite agglomerated particles obtained in Synthesis Example 1 were heated and dried at 105 ° C. for 5 hours. Next, the dry powder was wet-milled with a sand grinder to obtain calcium carbonate / silica composite agglomerated particles having an average particle diameter of 2.0 μm.

<Synthesis Example 4> 18 g of powder of calcium carbonate (TP-121 manufactured by Okutama Kogyo Co., Ltd.) and 12 g of titanium dioxide (FA-50 manufactured by Furukawa Co., Ltd.) were used as an aqueous sodium silicate solution (as silicic acid content).
3.61%) to 312 g, and using a homomixer to perform dispersion treatment at a rotation speed of 3000 rpm for 20 minutes, calcium carbonate,
A mixed slurry of titanium dioxide was prepared. Next, this slurry was added with a stirrer, a temperature sensor, and a reflux condenser.
The mixture was placed in an L four-necked flask and heated to 75 ° C. in an oil bath while stirring. Next, while keeping the slurry in the container at 75 ° C,
276 g of 0.36N sulfuric acid was added dropwise using a microtuning pump at a dropping rate of 1.53 ml / min for 3 hours to obtain calcium carbonate / titanium dioxide / silica composite agglomerated particles.
The pH of the reaction solution at this time was 10.1. Furthermore, a wet cake of calcium carbonate / titanium dioxide / silica composite agglomerated particles was obtained by filtering with a No. 2 filter paper, washing with water, and filtering again. The average particle size is 4.9 microns and the ratio of calcium carbonate to titanium dioxide to silica is 5
It was 2:34:14.

<Synthesis Example 5> 30 g of powder of kaolin (Amazon 88SD manufactured by CADAM) was added to 312 g of an aqueous solution of sodium silicate (3.61% as silicic acid content) and dispersed for 20 minutes at 3000 rpm using a homomixer. A kaolin slurry was prepared by treatment. Next, this slurry was placed in a 1 L four-necked flask equipped with a stirrer, a temperature sensor, and a reflux condenser, and heated to 75 ° C. in an oil bath while stirring. Next, while keeping the slurry in the container at 75 ° C, 276 g of 0.36N sulfuric acid was added using a microtuning pump at a dropping rate of 1.53
The mixture was added dropwise at 3 ml / min over 3 hours to obtain kaolin / silica composite agglomerated particles. The pH of the reaction solution at this time was 8.5. Furthermore, a wet cake of kaolin / silica composite agglomerated particles was obtained by filtering with a No. 2 filter paper, washing with water, and filtering again. The average particle size was 12.7 microns and the ratio of kaolin to silica was 70:30.

<Synthesis Example 6> The kaolin-silica composite agglomerated particles obtained in Synthesis Example 5 were heated and dried at 105 ° C. for 5 hours. Next, the dry powder was wet-milled with a sand grinder to obtain kaolin-silica composite agglomerated particles having an average particle diameter of 2.5 microns.

<Synthesis Example 7> Calcium carbonate / silica composite agglomerated particles were obtained in the same manner as in Synthesis Example 1 except that the amount of calcium carbonate powder was changed to 20 g. The pH of the reaction solution at this time was 10.2. The average particle size of the obtained calcium carbonate / silica composite agglomerated particles was 10.0 microns, and the ratio of calcium carbonate to silica was 65:35.

<Synthesis Example 8> Calcium carbonate-silica composite agglomerated particles were obtained in the same manner as in Synthesis Example 1 except that the powder of calcium carbonate was changed to 10 g. The pH of the reaction solution at this time was 10.1. The average particle size of the obtained calcium carbonate / silica composite agglomerated particles was 30.5 microns, and the ratio of calcium carbonate to silica was 60:40.

<Synthesis Example 9> Kaolin / silica composite agglomerated particles were obtained in the same manner as in Synthesis Example 5, except that the amount of kaolin powder was changed to 20 g. The pH of the reaction solution at this time was 9.8. The average particle diameter of the obtained kaolin / silica composite agglomerated particles was 15.0 microns, and the ratio of kaolin to silica was 70:30.

<Synthesis Example 10> Kaolin / silica composite agglomerated particles were obtained in the same manner as in Synthesis Example 5, except that the amount of kaolin powder was changed to 10 g. The pH of the reaction solution at this time was 9.6. The average particle size of the obtained kaolin-silica composite agglomerated particles was 35.5 microns, and the ratio of kaolin to silica was 68:32.

<Synthesis Example 11> 30 g of powder of calcium carbonate (TP-121 manufactured by Okutama Kogyo Co., Ltd.) was added to 312 g of an aqueous sodium silicate solution (3.61% as silicic acid content), and a homomixer was used to rotate at 20 rpm at 3000 rpm. The dispersion treatment was performed for 1 minute to prepare a calcium carbonate slurry. Next, this slurry was placed in a 1 L four-necked flask equipped with a stirrer, a temperature sensor, and a reflux condenser, and heated to 75 ° C. in an oil bath while stirring.
Next, while maintaining the slurry in the container at 75 ° C, 180 g of sulfuric acid with a concentration of 10% by weight was dropped using a microtuning pump at a dropping rate of 1.0 ml / min over 3 hours to form calcium carbonate-silica composite particles. Obtained. The pH of the reaction solution at this time is
It was 5.7. Furthermore, a wet cake of calcium carbonate / silica composite particles was obtained by filtering with a No. 2 filter paper, washing with water, and filtering again. The average particle size was 9 microns, the ratio of calcium carbonate to silica was 25:75, and the ratio of silica was higher than that of calcium carbonate. When the composite particles were observed with an electron microscope, the particles were spherical and the calcium carbonate was completely covered with white carbon.

<Synthesis Example 12> 30 g of powder of kaolin (Amazon 88SD manufactured by CADAM) was added to 312 g of an aqueous solution of sodium silicate (3.61% as silicic acid content) and dispersed for 20 minutes at 3000 rpm using a homomixer. A kaolin slurry was prepared by treatment. Next, this slurry was placed in a 1 L four-necked flask equipped with a stirrer, a temperature sensor, and a reflux condenser, and heated to 75 ° C. in an oil bath while stirring. Next, while maintaining the slurry in the container at 75 ° C, sulfuric acid with a concentration of 10% by weight was added.
180 g of the kaolin-silica composite particles was obtained by using a micro-tuning pump and dropping at a dropping rate of 1.0 ml / min over 3 hours. The pH of the reaction solution at this time was 6.5. Furthermore, a wet cake of kaolin-silica composite particles was obtained by filtering with a No. 2 filter paper, washing with water, and filtering again. The average particle size was 9.5 micron, the ratio of kaolin to silica was 20:80, and the ratio of silica was higher than that of kaolin. When the composite particles were observed with an electron microscope, the particles were spherical and the kaolin was completely covered with white carbon.

[Example 1] Hardwood bleached pulp (LBKP CSF407
ml) slurry (concentration 1.00%), the composite aggregate particle slurry of Synthesis Example 1 was added to 10% of the dry weight of pulp, and after stirring for 1 minute, a sulfuric acid band was added to the dry weight of 1%. did. Further, after stirring for 1 minute, 100 ppm of cationic PAM (Himoloc DR-1500) was added as a retention aid based on the total dry weight of pulp and filler, and the mixture was stirred. A trace amount of sulfuric acid band was added to adjust the pH to 8.0-8.5. did. Using this refined pulp slurry, a target hand weight of 64 g / m ² ,
Paper was made so that the ash content in the paper would be 10% by weight, dehydrated by a press, and then dried by a blow dryer (50 ° C., 1 hour) to prepare a sheet sample. The density, whiteness, opacity and breaking length of this sheet were measured and shown in Table 1.

Example 2 Synthesis Example 2 in Example 1
A sheet was produced under the same conditions except that the composite agglomerated particles of 1 were used. The physical properties were measured and evaluated in the same manner as in Example 1 with the obtained sheet, and the results are shown in Table 1.

[Embodiment 3] Synthesis Example 3 in Embodiment 1
A sheet was produced under the same conditions except that the composite agglomerated particles of 1 were used. The physical properties were measured and evaluated in the same manner as in Example 1 with the obtained sheet, and the results are shown in Table 1.

[Example 4] Synthesis Example 4 in Example 1
A sheet was produced under the same conditions except that the composite agglomerated particles of 1 were used. The physical properties were measured and evaluated in the same manner as in Example 1 with the obtained sheet, and the results are shown in Table 1.

Comparative Example 1 A sheet was produced under the same conditions as in Example 1, except that the powder of calcium carbonate (TP-121 manufactured by Okutama Kogyo Co., Ltd.) was used. The physical properties were measured and evaluated in the same manner as in Example 1 with the obtained sheet, and the results are shown in Table 1.

Comparative Example 2 Synthesis Example 1 in Example 1
A sheet was produced under the same conditions except that the composite particles of No. 1 were used. The physical properties were measured and evaluated in the same manner as in Example 1 with the obtained sheet, and the results are shown in Table 1.

[Embodiment 5] Synthesis Example 5 in Embodiment 1
A sheet was produced under the same conditions except that the composite agglomerated particles of 1 were used. The physical properties were measured and evaluated in the same manner as in Example 1 with the obtained sheet, and the results are shown in Table 1.

Example 6 Synthesis Example 6 in Example 1
A sheet was produced under the same conditions except that the composite agglomerated particles of 1 were used. The physical properties were measured and evaluated in the same manner as in Example 1 with the obtained sheet, and the results are shown in Table 1.

Comparative Example 3 A sheet was prepared under the same conditions as in Example 1 except that kaolin (Amazon 88SD manufactured by CADAM) was used. The physical properties were measured and evaluated in the same manner as in Example 1 with the obtained sheet, and the results are shown in Table 1.

[Comparative Example 4] Synthesis Example 1 in Example 1
A sheet was produced under the same conditions except that the composite particles of No. 2 were used. The physical properties were measured and evaluated in the same manner as in Example 1 with the obtained sheet, and the results are shown in Table 1.

Table 1 shows the evaluation results of the physical properties of Examples 1 to 6 and Comparative Examples 1 to 4 described above.

Example 7 Hardwood bleached pulp (LBKP CSF4
07 ml) of slurry (concentration 1.00%) to which the composite aggregate particle slurry of Synthesis Example 7 was added so as to be 10% per pulp dry weight, and after stirring for 1 minute, a sulfuric acid band was added at 1% per dry weight.
Was added. Furthermore, after stirring for 1 minute, as a retention aid,
Cation PAM (Himoloc DR-1500) was added and stirred at 100 ppm per total dry weight of pulp and filler, and a small amount of sulfuric acid band was added so that the pH became 8.0 to 8.5. A target basis weight of 64 g /
A sheet sample was prepared by making a paper so that the ash content in the paper was m ² and the ash content in the paper was 10% by weight, dehydrated by a press, and dried by a blow dryer (50 ° C., 1 hour). The density, whiteness,
The opacity, breaking length and filler yield were measured and are shown in Table 2.

[Embodiment 8] Synthesis Example 8 in Embodiment 7
A sheet was produced under the same conditions except that the composite agglomerated particles of 1 were used. The physical properties were measured and evaluated in the same manner as in Example 7 with the obtained sheet, and the results are shown in Table 2.

Example 9 Synthesis Example 9 in Example 7
A sheet was produced under the same conditions except that the composite agglomerated particles of 1 were used. The physical properties were measured and evaluated in the same manner as in Example 7 with the obtained sheet, and the results are shown in Table 2.

Example 10 A sheet was produced under the same conditions as in Example 7, except that the composite agglomerated particles of Synthesis Example 10 were used. The physical properties were measured and evaluated in the same manner as in Example 7 with the obtained sheet, and the results are shown in Table 2.

Examples 7 to 10 and Comparative Examples 1 and 2 above
Table 2 shows the results of evaluation and evaluation of physical properties.

[0052]

[Table 1]

As shown in Table 1, Example 1 and Example 2
In the calcium carbonate-silica composite particles produced by using calcium carbonate as a raw material, the density of the paper was reduced by 4 to 6% as compared with the case of only calcium carbonate of Comparative Example 1, and bulkiness was recognized. In addition, the whiteness increased by 0.8-1.0 point, the opacity increased by 0.7-0.8 points, and the breaking length was 27%.
It was higher and there was little decrease in paper strength due to internal addition of filler.

The heat-dried calcium carbonate of Example 3
When the silica composite particles were pulverized with a sand grinder, the paper density was reduced by 10%, and extremely high bulkiness was recognized. Furthermore, the whiteness is 1.6 points and the opacity is
It increased by 1.3 points, the breaking length increased by 47%, and the decrease in paper strength was extremely small.

In the calcium carbonate / titanium dioxide / silica composite particles of Example 4, the density of the paper was reduced by 6%, and high bulkiness was recognized. Furthermore, since titanium dioxide was compounded, both whiteness and opacity increased by 2.5 points, the breaking length increased by 47%, and the decrease in paper strength was extremely small.

Further, in the case where the pH of the final reaction liquid of Comparative Example 2 was in the acidic region of 5.7, the ratio of calcium carbonate to silica was 25:75, the ratio of silica was higher than that of calcium carbonate, and calcium carbonate was Since it is a spherical body completely covered with white carbon, it has no bulkiness and its whiteness is reduced by 0.4 points and opacity is reduced by 1.4 points. The breaking length is almost unchanged.

In the kaolin / silica composite particles produced using kaolin of Example 5 as a raw material, the density of the paper was reduced by 8%, and high bulkiness was recognized, as compared with the case of using only kaolin of Comparative Example 3. . Furthermore, the whiteness increased by 1.2 points and the opacity increased by 1.9 points, and the breaking length also increased by 40%, and the decrease in paper strength was small.

When the heat-dried kaolin-silica composite particles of Example 6 were crushed with a sand grinder, the paper density was 12 as compared with the case of using only kaolin of Comparative Example 3.
%, And high bulkiness was recognized. Furthermore, the whiteness increased by 1.5 points and the opacity increased by 2.4 points, the breaking length increased by 47%, and the decrease in paper strength was small.

In the case where the pH of the final reaction solution of Comparative Example 4 was adjusted to 6.5 in the acidic range, the ratio of kaolin to silica was 2
It is 0:80, the ratio of silica is higher than that of kaolin, and since kaolin is a spherical body completely covered with white carbon, there is no bulkiness, whiteness is reduced by 0.2 points, and opacity is reduced by 1.0 point. . The breaking length is almost unchanged.

[0060]

[Table 2]

As shown in Table 2, when the particle size of the composite particles of Examples 7 to 10 is 10 μm or more, the bulkiness, whiteness and opacity are high, the paper strength is not significantly reduced, and the filler yield is 43. It was very high at ~ 47%.

[0062]

[Effects of the Invention] Inorganic fine particles are added to and dispersed in an aqueous solution of alkali silicate to prepare a slurry, which is then heated and stirred, while maintaining the liquid temperature in the range of 60 to 100 ° C, to which an acid is added to form a silica sol for the final reaction. By internally adding the inorganic fine particle / silica composite particles formed by adjusting the pH of the liquid to the range of neutral to weakly alkaline, a filler-added paper having the following characteristics was obtained. 1) Light and thick paper with high bulkiness can be obtained 2) Excellent optical properties such as whiteness and opacity 3) Bulkiness and excellent paper strength (tear length, tear strength) 4) High yield of filler

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[Procedure amendment]

[Submission date] September 18, 2001 (2001.9.1)
8)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09C 1/42 C09C 1/42 3/06 3/06 // C01B 33/12 C01B 33/12 A C01F 11 / 18 C01F 11/18 G (72) Inventor Kei Matsumoto 5-21-1 Oji, Kita-ku, Tokyo Inside Technical Research Institute, Nippon Paper Industries Co., Ltd. (72) Inventor Mitsutoshi Nakamura 5-21-1 Prince, Kita-ku, Tokyo F-Term in Technical Research Laboratories, Nippon Paper Industries Co., Ltd. AH02 EA16 EA25 EA31 FA12 FA16

Claims (7)

[Claims] 1. An inorganic fine particle is added to and dispersed in an aqueous solution of alkali silicate to prepare a slurry, which is then heated and stirred, while maintaining the liquid temperature in the range of 60 to 100 ° C. to add an acid to form a silica sol, and a final reaction. A method for producing inorganic fine particles / silica composite particles, which is formed by adjusting the pH of a liquid to a neutral to weakly alkaline range. 2. The inorganic fine particles are calcium carbonate, talc,
The method for producing inorganic fine particle-silica composite particles according to claim 1, which is a single material or a mixture of two or more kinds of clay, kaolin, calcined kaolin, titanium dioxide and aluminum hydroxide. 3. The concentration of the alkali silicate aqueous solution is 3 to 10% by weight.
The method for producing inorganic fine particle-silica composite particles according to claim 1, wherein the method is (converted to SiO2). 4. The method for producing inorganic fine particle-silica composite particles according to claim 1, wherein the pH of the final reaction liquid obtained by adding an acid after dispersing the inorganic fine particles in an aqueous solution of alkali silicate is in the range of 8 to 11. 5. A method for producing a filler-containing paper by adding a filler to a pulp slurry for papermaking, wherein the filler is the inorganic fine particle-silica composite particles according to claim 1. 6. A method for producing a paper with a filler inside by making a paper by adding a filler to a pulp slurry, wherein the filler is a fine powder with a pulverizer after the inorganic fine particles / silica composite particles according to claim 1 are dried. A method for producing a filler-added paper that has been prepared. 7. A 50% volume average particle diameter by laser diffraction / scattering method is 10 to 60 microns.
Item 2. A method for producing the inorganic fine particle-silica composite particle and the method for producing the filler-added paper.