JP2960001B2 - Manufacturing method of filler-filled paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing paper with a filler added, and more particularly to a method for producing a paper with a filler, which is excellent not only in opacity of white paper but also in opacity after printing and has little decrease in paper strength. It is about.

[0002]

2. Description of the Related Art From the standpoint of protecting forest resources and reducing the environmental burden including the problem of waste, there is a need to reduce the weight of paper. Weight reduction reduces the weight of wood fibers needed to convey the same amount of information, as well as the amount of waste. Especially for newsprint, the weight per unit area is 50 g / m ² to 43
Some have shifted to 40 or less. At the time of such weight reduction, the optical properties of paper, particularly opacity and opacity after printing are deteriorated, and so-called "through strike-through" becomes a problem. This problem is the same not only in newsprint paper but also in general lightweight printing paper. However, these papers are bulky (thick) due to weight reduction.
It is also a big problem that the number is reduced. Conventionally, to solve these problems, hydrated silicic acid or calcined clay called white carbon has been used. The hydrated silicic acid for internal addition is a porous filler having a primary particle diameter of about 0.01 to 0.05 μm, usually agglomerated, and having a particle diameter of 5 to 10 μm when measured by a Coulter counter. Because of its excellent properties, it is effective in preventing strikethrough caused by penetration of oil-based printing ink. However, the ability to scatter incident light is low due to the relatively large particle size. That is, there is the ability to maintain the opacity after printing, but the ability to improve the opacity of blank paper is small. On the other hand, other internal fillers for papermaking represented by titanium dioxide have a small particle size and a high ability to scatter light, but a low ability to suppress the penetration of printing ink. Usually, these fillers are used alone or in combination to satisfy required quality in printing paper such as newsprint. Also,
In general, the mineral filler has a specific gravity larger than the apparent specific gravity of the cellulose fiber, so the higher the filler content in the paper,
The density of the paper increases and the bulk decreases. Since the above-mentioned white carbon, the same kind of hydrated silicate, and special precipitated calcium carbonate are porous, the bulk increases as the filler content in the paper increases.

[0003]

However, in the case of extremely light weight as described above, it is not possible to achieve both the opacity of blank paper and the opacity after printing with any combination of conventional fillers. In addition, fillers such as white carbon have a large particle diameter, which significantly impairs inter-fiber bonding, resulting in a decrease in strength. The present invention has a large pore volume,
Focusing on the fact that hydrated silicic acid with extremely fine particle properties is more effective in preventing strike-through of paper than existing hydrated silicic acid and hydrated silicate, the addition of this filler maintains the strength while maintaining the opacity of white paper. The present invention provides a method for producing paper having high opacity and opacity after printing.

[0004]

The hydrated silicic acid used to achieve the above object is a hydrated silicic acid obtained by neutralizing an aqueous solution of sodium silicate with a mineral acid, and has an oil absorption of 250 to 150%.
350ml / 100g, total pore volume is 4.0-6.0c
The average pore radius is in the range of 200 to 400 angstroms in c / g, and the average particle diameter is 3.0 to 15 μm as measured by a laser method, 2.0 to 4.0 μm as measured by a Coulter method, or centrifugation. It is characterized by having a particle property in a range of 0.5 to 3.5 μm as measured by a sedimentation method.

As the characteristic values of the hydrated silicic acid according to the present invention, values obtained by the following measuring methods are used.

(1) Oil absorption; according to JIS K5101 (2) BET specific surface area: powdered hydrated silica sample 0.0
5 to 0.1 g of "Flow Soap 23" manufactured by Shimadzu Corporation
It is measured under deaeration conditions at 300 ° C. for 30 minutes using “00S / N type”.

(3) Total pore volume: A 0.05 g sample of powdered hydrated silicic acid was degassed under vacuum for 30 minutes, and then mercury was injected and pressurized to 1 to 1900 bar to bring the pore volume into mercury. It is measured by a method (used equipment: Mercury porosimeter 200, manufactured by Carlo Elba). The measured pressure corresponds to a pore radius of 75,000 Å to 39 Å.
(4) Average pore radius: From the specific surface area S and the total pore volume V obtained in the measurement of the total pore volume, the radius (r) = V /
It is determined by the value calculated in S.

(5) Particle size distribution measurement; (a) Laser method: A sample slurry of hydrated silicic acid is dropped and mixed in pure water to which 0.2% by weight of dispersant sodium hexametaphosphate has been added to form a uniform dispersion. The particle size is measured using a method particle size analyzer [using equipment; manufactured by Nikkiso Co., Ltd., using “Microtrac 9220FRA type”).

(B) Coal tar method: A sample hydrated silicate slurry is dropped in 3 drops of 50 ml of pure water containing 0.2% by weight of sodium hexametaphosphate, and a homogenous dispersion obtained by ultrasonic dispersion for 3 minutes is used as a Coulter counter TA type. (Coulter Electronics Co., Ltd.) to measure the particle size.

(E) Centrifugal sedimentation method: A sample hydrated silicate slurry is dropped into a pure water solution containing 0.2% by weight of sodium hexametaphosphate and measured as a measurable concentration (use equipment: “Micron ™” manufactured by Seishin Enterprise Co., Ltd.). Photosizer SK
(N-1000 type) is used. The portion having a particle size of 1 ml or less is measured by centrifugation, and the portion having a particle size of 1 ml or more is measured by gravity sedimentation.

The fine hydrated silica according to the present invention has the following particle properties:
First, it is characterized in that the total pore volume is 4.0 to 6.0 cc / g and the average pore radius is in the range of 200 to 400 angstroms. This total pore volume is located at a higher level than the hydrated silicic acid obtained by the conventional method of wet-milling the reaction-completed slurry, which is at most 4 cc / g, and has a porous structure. . Therefore, when used as a filler for paper, it effectively functions to efficiently absorb the ink liquid. If the total pore volume is less than 4.0 cc / g, the absorption capacity is insufficient and the strike-through preventing effect is not effectively provided. If the total pore volume exceeds 6.0 cc / g, other properties are impaired. Invite.

The total pore volume is related to the pore radius of the pores distributed in the tissue.
Since the pores smaller than Å are always filled with the equilibrium water for adsorption, they do not function for adsorption, and the adsorbing power becomes weaker than 104 Å and does not contribute to the adsorbability. The hydrated silica of the present invention having a total pore volume in the range of 4.0 to 6.0 cc / g has an average pore radius of about 100 to 40.
0 Angstroms (the center pore radius at 50% pore volume is 1500-3500 Angstroms);
It is located in a range where the adsorptivity is superior to conventional hydrated silica. For this reason, it is suitable not only for paper filler but also for various uses as described below.

The second particle property requirement of the finely hydrated silica according to the present invention is that the average particle diameter of the finely hydrated silica is 3.0 to 15 μm as measured by a laser method and measured by a Coulter method. This is a point in a range of 2.0 to 4.0 μm or 0.5 to 3.5 μm as measured by a centrifugal sedimentation method. The particle size of hydrated silica shows different measured values by the laser method, the Coulter method and the centrifugal sedimentation method. This is considered to be because the silica particles are porous and strongly hydrated. The hydrated silicic acid according to the present invention is characterized in that it is a fine particle as compared with the conventional silicate, and tends to take a particularly small value when measured by a centrifugal sedimentation method. The relatively large value in the measurement by the laser method is because particles having a size of 1 μm or less tend to be transparent and not detected, and are significant as an evaluation of the particle size of relatively large secondary particles. . Furthermore, the hydrated silica according to the present invention has an oil absorption of 250 to 3 in combination with the above-mentioned particle characteristics.
The feature is also in the range of 50 ml / 100 g, which is a relatively large value compared to the conventional one. This property is also one of the preferable properties as a paper filler.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A hydrated silicic acid having the above-mentioned particle properties is produced by adding a mineral acid to an aqueous solution of sodium silicate to produce a hydrated silicic acid by a neutralization reaction.
After adding a mineral acid in an amount corresponding to 30 to 50% of the neutralization equivalent to 6 to 10% by weight of sodium silicate as _{2 at} a temperature of 70 ° C. or higher and the boiling point of the reaction system, a strong shear force is applied within the aging time. First to perform a thorough wet grinding process based on
A second step of adding a substantial residual amount of mineral acid at a temperature equal to or higher than the temperature of the previous step and then aging to precipitate almost all of the silica, and further adding a mineral acid to raise the pH of the slurry to 5 to 5. And a third step of adjusting to a range of 3.

The first step is a step of heating the aqueous solution of sodium silicate while adjusting the concentration, adding the first stage mineral acid, and performing wet grinding and aging. The sodium silicate solution is SiO ₂ / Ma ₂ O
Is preferably 2.9 to 3.4, and the silica concentration needs to be set in the range of 6 to 10% by weight. If the silica concentration exceeds 10% by weight, uniform stirring cannot be performed when the viscosity increases in the first step, and silica having good particle characteristics cannot be obtained. If the concentration is as low as less than 6% by weight, the production efficiency deteriorates.
The sodium silicate solution whose concentration has been adjusted is heated to a temperature range from 70 ° C. to the boiling point of the solution or lower. If the temperature is lower than 70 ° C., the deposition rate of silica becomes slow, and it takes a long time to complete the first-stage reaction.

As the mineral acid to be subjected to the neutralization reaction, it is preferable to use sulfuric acid. The concentration of sulfuric acid is not particularly limited, but if it is too thin, the reaction system becomes too thin and the capacity becomes too large, so that it is not industrial. High-concentration 98% sulfuric acid generates a large amount of heat and can be used energetically if sufficient mixing can be performed at the addition position. The amount of the mineral acid added in the first step is 35 to 5 of the neutralization equivalent of sodium silicate.
It is set in the range of the amount corresponding to 0%. This addition range is related to the structure of the hydrated silicic acid, and if it is less than 35% or more than 50%, the high structure of the precipitated silica is impaired, preventing the strike-through when used as a paper filler. The effect and the yield are reduced. The time required for the addition is preferably a relatively short time of 5 to 20 minutes, and it is preferable to complete the addition before the precipitation of silica. Further, as the temperature and the silica concentration are higher and the amount of the mineral acid added is larger, the silica is precipitated in a shorter time, so that it is desirable to adjust the addition rate according to those conditions. Addition within 5 minutes results in insufficient uniform reaction system configuration.

A particularly important operating requirement in the first step, in addition to the above reaction conditions, is to carry out a thorough wet milling based on strong shearing forces immediately after the addition of the mineral acid. The wet pulverization has a pulverizing effect even after the silica after addition of the mineral acid is precipitated, but it is preferable that the silica pulverization starts immediately before or immediately before the precipitation. In the study of the inventors, it has been found that pulverization from the beginning of precipitation is effective. Therefore, the pulverization proceeds simultaneously with the aging treatment performed after the addition of the mineral acid. This process step in the prior art is referred to as a maturation operation, which has been performed only to promote the precipitation of silica by continuing a normal stirring operation under heating for a predetermined time. By thoroughly conducting the reaction, the reaction system becomes extremely homogenized, and the pulverization efficiency is remarkably improved, so that preferable particles are produced. The aging time depends on the temperature, but 80 ° C
For 2 to 3 hours, and at 90 ° C. for 1 to 2 hours. The wet pulverization is completed within the aging time, and is not performed after the second step. Therefore, the ripening in this step will be performed during the thorough grinding process after the partial neutralization.

Here, the thorough wet pulverization means an operation of using a pulverizer or a disperser capable of applying a strong shearing force to prevent agglomeration of the produced silica particles as much as possible. For this reason, depending on the pulverizer to be used, it is desirable to carry out the pulverization treatment continuously and repeatedly throughout the aging time. It is particularly preferable that the silica particles (dispersion degree) generated in this step have an average particle diameter in the range of 2.0 to 1.0 μm according to the Coulter method.

Examples of the pulverizer used for the wet pulverization include a ball mill in a broad sense such as a ball mill and a rod mill, a medium stirring type pulverizer such as a tower mill, an attritor, a sately mill, a sand grinder, an annular mill, a colloid mill, a homomixer, and an in-line mill. High-speed rotary crusher. Since the silica particles precipitated in the present invention are very fine, and particularly the silica precipitated in the first step is easily pulverized, the silica particles can be pulverized with a disperser or an emulsifier in addition to the above-mentioned pulverizer. May be used in combination with a crusher.

In the second step, while maintaining the slurry temperature from 80 ° C. to a temperature not higher than the boiling point of the solution, at a temperature not lower than the temperature of the previous step, a substantially residual amount of the mineral acid is dividedly added as a second stage and almost the entire amount is added. This is a step of precipitating silica and strengthening the connection of the silica particles precipitated in the first step. That is, the neutralization rate of the mineral acid in this step is preferably controlled so that the neutralization rate is 80 to 95% as the first stage addition, and the addition is generally performed over 15 to 30 minutes. After the addition, it is preferable to perform aging for a while under normal conditions to complete the reaction.

The particle size of the final hydrated silica after the second step is surprisingly substantially equal to that after the first step. The fact that the particle diameter does not change in the second step as described above means that nucleation, particle growth, particle aggregation,
This indicates that the control of the coagulation diameter by thorough wet pulverization and the strengthening of the bond in the coagulation particles in the second step smoothly proceed to synthesize a high-structure hydrated silicic acid having the above characteristics. Therefore, the pulverizing process in the second and subsequent steps is not performed. The reason for this is that it breaks the highly structured silica structure that has been bent. Further, although the viscosity of the slurry is high at the stage of the first step, the viscosity of the slurry is reduced to about 1/5 after the second step, which is advantageous for handling.

The third step is a step of adjusting the pH of the slurry to a range of 5 to 3 by further adding a mineral acid subsequent to the second step. At this stage, the addition of the mineral acid causes the alkali component contained in the hydrated silicic acid to elute, causing the pH to return, and since the change in this pH range is large, it takes about 30 to 60 minutes to slowly add the mineral acid. It is preferred to do so. Therefore,
The only operational difference between the second and third steps is the rate of addition of the mineral acid, and the other conditions are substantially the same. Using a low concentration of sulfuric acid to accurately adjust the pH is also a good method. The addition of the mineral acid here is exclusively for adjusting the pH of the reaction system, and the reaction is substantially completed in the previous step.
%, Preferably about 5%. Operationally, it is a gradual addition process with intermittent operation in view of the relationship with the previous process.

The hydrated silica obtained in the third step includes:
Since sodium sulfate produced as a by-product may be mixed in, it is preferable to perform filtration, washing with water and repulp treatment.

The hydrated silicic acid according to the present invention is, as described above,
Even if the compounding amount in the paper is small, the ink has high absorbency of the printing ink, and thus has an excellent strike-through prevention effect. That is, when mixed with paper, the opacity after printing is improved. However, with regard to the opacity of the white paper, the hydrated silica does not contribute to the increase in the opacity of the paper unless it is added in an amount of at least 3% by weight per pulp. Hydrated silicic acid as a filler for papermaking is expensive compared to other papermaking raw materials, and it causes paper dust when blended at a high level. Less than percent. Thus, the hydrated silica hardly contributes to the increase in the opacity of the paper. Then, in order to maintain the opacity of the white paper and improve the opacity after printing, the following method is generally considered.

(1) A pulp raw material having high opacity, such as GP, is blended or the degree of beating is adjusted.

(2) In order to increase the light scattering ability of paper, the basis weight is increased, or the bonding between fibers is reduced by adjusting the wet pressure, chemicals, or the like.

(3) In order to increase the light absorption coefficient of paper, a colored raw material having low whiteness is used or the paper is colored.

(4) In order to increase the light scattering coefficient of paper,
A filler having a high light scattering coefficient is blended.

Although the methods (1) to (3) are effective for improving the opacity of the paper, there is a possibility that the properties of the paper are greatly changed. The method (4) is the simplest method. However, since the filler having a high light scattering coefficient is expensive not only for inorganic and organic substances, it is expensive to use it for printing paper such as general newsprint. This causes the price to rise, which is not desirable in social ethics. Therefore, as a result of intensive studies, a method was devised to improve both opacity after printing and opacity of white paper by combining inexpensive fillers such as talc and kaolin with the hydrated silica of the present invention. First, the hydrated silicic acid according to the present invention is dispersed in water, and is pre-agglomerated with a sulfuric acid band or a cationic polyelectrolyte coagulant. Examples of the cationic polymer flocculant include cationic polyacrylamide derivatives, cationic starch and the like. At this time, firm coagulation degrades formation, which has an adverse effect on opacity improvement. That is, in this case, the sulfate band or the cationic polyelectrolyte coagulant plays an auxiliary role, and when the hydrated silicic acid coagulates due to the presence of a cationized substance in white water or the like in the papermaking process, these coagulants are used. Can be used in small quantities. When many cations are already present, use of a nonionic or anionic dispersant may be considered. In the normal papermaking process, a hydrodynamic shearing force is applied by a stirrer or pump at this stage, so apparently no agglomeration has occurred at this stage. 3.5 to 18 μm in value
It is preferable that the particles be aggregated so as to be in the range of. After this dispersion, it is added to the stock to form a paper. In this stock, general-purpose fillers other than those described above are mixed in advance with pulp, chemicals and the like. For example, it is any of hydrated silicic acid / hydrated silicate called white carbon, talc, clay, kaolin and the like, or a mixture thereof. Either mechanical pulp or chemical pulp or a mixture thereof may be used as the pulp. Any of a sulfuric acid band, a retention agent, a paper strength agent, and a sizing agent, or a mixture thereof may be used as an additive chemical. Usually, in such a system, when pulp and filler are mixed at the same time and paper is made, due to physical filtration action and surface chemical interaction,
Non-uniform millimeter-scale flocs are formed, which causes a reduction in opacity. In the present invention, the hydrated silicic acid according to the present invention acts not only as an opacity improving agent after printing but also as a microscopic dispersant for floc. Originally, anionic polymeric dispersants have been used for this type of treatment, but this agent does not have the ability to increase opacity. By using fine hydrated silicic acid for coagulation adjustment to the extent that formation is not deteriorated, voids effective for light scattering are formed between coarse fillers such as talc and kaolin. The same effect is exhibited by interposing between pulp and fine fibers. Naturally, if the hydrated silicic acid is too much interposed between the fibers, the inter-fiber bonding will be hindered, and in order to prevent a decrease in the strength of the paper, the addition rate must be 5% by weight or less. However, A. J. Hayes is Paper Tec
hnology ahd Industry magazine (4) 1
As shown in 985, the filler is coagulated in advance with the cationic polyelectrolyte and then added to the stock to reduce the paper strength little. Therefore, according to the present invention, the hydrated silicic acid according to the present invention requires 25% by weight. Additions of up to 25% by weight are possible with other fillers combined with this hydrated silica. Further, the minimum addition ratios that contribute to the opacity and the strike-through value are each 0.05% by weight or more.
Naturally, highly opaque and expensive fillers such as calcined clay, calcined kaolin, and titanium dioxide may be used, but in the present invention, even with low-cost fillers such as talc and kaolin, an effect of improving opacity can be expected by the above mechanism.

The hydrated silica according to the present invention has a total pore volume of 4.0 to 6.0 cc / g and an average pore radius of 200 to 40.
While having a high level of porous structure in the range of 0 Angstroms, the average particle size measured by the laser method is 3.
0 to 15 μm, 2.0 to 2.0 as measured by the Coulter method
4.0 μm or 0.5 to 0.5 μm as measured by the centrifugal sedimentation method.
It is in any of the fine ranges of 3.5 μm, and exhibits a lightweight and excellent strike-through prevention effect, especially when applied as a filler for paper, and exhibits a high filler yield. Therefore, in many cases, the specific surface area is in the range of 100 to 200 m ² / g, and the oil absorption is 250 to 350 ml / 100 g. Further, by adding the hydrated silicic acid according to the present invention to a stock composed of other fillers and pulp, paper having not only opacity after printing but also white opacity can be produced.

[0031]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples. In measuring the properties of the hydrated silicic acid, the total pore volume was measured using a mercury porosimeter 200 manufactured by Carlo Elba.
Type 0, laser method average particle size is Nikkiso Co., Ltd. Microtrac 9220FRA type, Coulter method average particle size is Coulter Electronics Co., Ltd. Coulter Counter TAII type, centrifugal sedimentation method average particle size is microphotosizer SKN manufactured by Seishin Enterprise Each of -1000 was used, and the measurement of the paper strike-through prevention effect and the filler yield was performed according to the following methods.

Measurement of paper strike-through prevention effect: NBK was used as a papermaking raw material with an orientation paper machine manufactured by Kumagai Riki Kogyo Co., Ltd.
P: TMP: GP: DIP = A pulp slurry having a mixing ratio of 20: 30: 20: 30 was used. The filler slurry obtained in each Example was used as a filler, and the basis weight was 40 g / m ² ,
Paper so that the ash content in the paper is 1-4 weight percent,
After dehydration with a press, the sheet was dried with a cylinder dryer to prepare a sheet sample. To this sheet sample, a newspaper ink for keyless offset [Toyo Ink Co., Ltd. N
ew King VANTEAN black]. After standing in an atmosphere of 20 ° C. and 65% RH for 24 hours, the reflectance of the printed back surface was measured with a Macbeth reflection densitometer, and the strike-through value (opacity after printing) was calculated by the following equation.

The strike-through value = (reflectance of printed back surface / reflectance of unprinted back surface) × 100 (%) Based on the strike-through value of a sheet sample prepared by adding the filler slurry of Comparative Example 1, The rise from the value was taken as the strike-through prevention effect.

Measurement of filler yield: Calculated by dividing the ash content in paper measured according to JIS P8128 by the addition ratio of filler slurry added during sheet making.

The opacity was measured using a Hunter reflectometer manufactured by Kumagai Riki Co., Ltd. in accordance with JIS-P8138.

The tensile strength was measured by a tensile tester manufactured by Toyo Seiki Co., Ltd. in accordance with JIS-P8113.

Production Example of Hydrated Silicic Acid Slurry Commercially available No. 3 sodium silicate (SiO ₂ : 20.
2% by weight, Na ₂ O: 9.5 wt%)
Was diluted with water to prepare a 6.7 weight percent diluted sodium silicate solution as SiO ₂ . First, as the first step,
After the sodium silicate solution was heated to 90 ° C., sulfuric acid (concentration: 95% by weight) corresponding to 40% of the neutralization equivalent was added over 7 minutes with sufficient vigorous stirring without generating a coarse gel. The liquid after the addition of sulfuric acid was transparent and no solid matter was observed. After the addition was completed, the obtained partially neutralized solution was transferred to a high-speed rotary pulverizer type mixer. During this liquid transfer, a large amount of silica precipitated and became a slurry. The crushing treatment was performed for 2 minutes. After the pulverization, the slurry was returned to the original reaction vessel, the temperature was reheated to 90 ° C., and the mixture was kept under stirring for 2 hours to ripen. A small amount of the slurry after aging was collected, and the particle size was measured by the Coulter method.

Next, as a second step, the slurry temperature was adjusted to 9
The temperature was raised to 5 ° C., sulfuric acid having the same concentration as in the first step was added to 85% of the neutralization equivalent over 15 minutes, and the mixture was aged for 15 minutes.

Subsequently, as a third step, 1N sulfuric acid was added to the aged slurry over 30 minutes to adjust the pH of the slurry to 4.5.

After the completion of the third step, the slurry was filtered, washed with water, and a 10% by weight slurry of hydrated silicic acid repulped in pure water was recovered. The obtained slurry was filtered and dried to measure the total pore volume, the average pore radius, the BET specific surface area and the oil absorption. The results are shown in Table 1 in comparison with the applied fluctuation conditions.

Example 1 A sulfuric acid band was added to the obtained hydrated silica slurry,
The pH was adjusted to 4.5 and a moderate stirrer was maintained at 300 rpm with a laboratory stirrer. Pulp separately
2 parts of Chinese talc (average particle size of 5-1
0 μm) was mixed and dispersed, and immediately before papermaking, a hydrated silica slurry containing a sulfuric acid band was added so as to have a total ash content of 3% by weight to produce a sheet. The strikethrough value and opacity of this sheet were measured and are shown in Table 1.

Example 2 A sheet was prepared under the same conditions as in Example 1 except that kaolin for internal filling manufactured by Huber was used instead of Chinese talc. The physical properties of the obtained sheet were measured and evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 3 In Example 1, in addition to Chinese talc, a kaolin for internal filling made by Huber was blended at 1% by weight per pulp, and a sheet was produced under the same conditions except for that. The physical properties of the obtained sheet were measured and evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 4 A sheet was prepared under the same conditions as in Example 1 except that 100 ppm of a cationic polymer flocculant (Himoloc NR11L, manufactured by Himo) was added instead of the sulfate band added to the hydrated silica. . Example 1 was obtained for the obtained sheet.
Physical properties were measured and evaluated in the same manner as described above, and the results are shown in Table 1.

Comparative Example 1 In Example 1, no filler other than the hydrated silicic acid obtained in the preparation example of the hydrated silicic acid slurry was added, and the filler in the paper was adjusted to 2% by weight. A sheet was produced under the same conditions. Example 1 was obtained for the obtained sheet.
Physical properties were measured and evaluated in the same manner as described above, and the results are shown in Table 1.

COMPARATIVE EXAMPLE 2 In Example 1, Chinese talc, Huber's internal kaolin and the hydrated silica obtained in the above-mentioned production example were simultaneously blended in an amount of 1% by weight per pulp.
Otherwise, a sheet was produced under the same conditions. The physical properties of the obtained sheet were measured and evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 3 A hydrated silicic acid slurry was produced under the same conditions as in Example 1 except that the pulverization treatment in the first step in the production example of the hydrated silicic acid slurry was not performed. A sheet was produced from the obtained slurry under the same conditions as in Comparative Example 1. The physical properties of the obtained sheet were measured and evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 4 The hydrated silicic acid obtained in Comparative Example 3 was used instead of the hydrated silicic acid obtained in the above-mentioned production example of the hydrated silicic acid slurry in the preparation of the sheet of Example 3, except that the same conditions were used. To prepare a sheet. The physical properties of the obtained sheet were measured and evaluated in the same manner as in Example 1, and the results are shown in Table 2.

From the results shown in Tables 1 and 2, the hydrated silicic acids of the examples satisfying the requirements of the total pore volume and the average particle diameter according to the present invention show strikethrough as compared with Comparative Examples 3 and 4, which are the reference. It is recognized that the prevention effect is excellent, and it can be seen that combining with other fillers increases not only the opacity after printing but also the opacity of white paper. In this case, simply mixing the hydrated silicic acid according to the present invention with another filler,
Since the effect of improving opacity is slightly low and the reduction in paper strength is large, it is recognized that it is desirable to add hydrated silica immediately before papermaking after mixing other fillers. However, it is obvious that the reduction in paper strength can be improved by using a combined pulp and a paper strength enhancer, and in such a system, not the low filler addition rate used in this example, but hydrated silica and other fillers. High addition rates, in each case above 20% by weight per pulp, are also possible.

[0050]

As described above, according to the present invention, not only opacity after printing but also white paper having high opacity can be manufactured. Therefore, this method not only contributes greatly to the papermaking industry, but also reduces the pulp, which is a wood resource, while maintaining not only the opacity after printing but also the opacity of white paper with the filler component using this method. As a result, it greatly contributes to the protection of forest resources and the environment. The method for producing paper using the hydrated silicic acid of the present invention is not limited to newsprint, for example, general high-quality or medium-quality printing paper, lower-grade paper,
It is also useful for producing coated paper base paper, PPC paper, foam paper, ink jet paper, thermal paper base paper, carbonless paper base paper, and the like.

[0051]

[Table 1]

[0052]

[Table 2]

Continuation of the front page (72) Inventor Takashi Ochi 5-21-1, Oji, Kita-ku, Tokyo Nippon Paper Industries Central Research Laboratory (56) References JP-A-8-91820 (JP, A) (58) Survey Field (Int.Cl. ⁶ , DB name) D21H 17 / 68,21 / 26

Claims (3)

(57) [Claims] 1. A method for producing a filler-filled paper by adding a hydrated silicic acid slurry to a stock containing pulp and a filler selected from the group consisting of talc, clay and kaolin. Silicic acid has the following A to C: B. oil absorption is 250 to 350 ml / 100 g; B. the total pore volume is 4.0-6.0 cc / g, the average pore radius is in the range of 200-400 angstroms; The average particle diameter is 3.0 to 1 as measured by a laser method.
5 μm, 2.0 to 4.0 μm as measured by the Coulter method
m, which satisfies the particle characteristics of any of 0.5 to 3.5 μm as measured by a centrifugal sedimentation method. 2. The method for producing a filler-filled paper according to claim 1, wherein the hydrated silica slurry is a mixture with a cationic polyelectrolyte or a sulfate band. 3. The method according to claim 1, wherein the filler is 0.05 to 2 with respect to the pulp.
5% by weight, said hydrated silica is 0.05 to 2
3. The method for producing a filler-filled paper according to claim 1, wherein 5% by weight is added.