JP2009040612A - Calcium carbonate-silica composite material and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a calcium carbonate-silica composite material which has high oil absorbing property so as to improve printability and high bulking effect on paper when it is used as a filler in the paper. <P>SOLUTION: The calcium carbonate-silica composite material is characterized in that (1) the molar ratio of calcium carbonate to silica is within a range of 25:75 to 40:65, and (2) in the case when its pore radius r is expressed by formula (I) and the pore volume Va is measured by a mercury penetration method within a range of a of -3 to 23, the comparison of the pore volume Va in each pore radius range partitioned so that the difference between the values of a is 1 shows that the range of pore radius where Va is maximum is within a partition range where a is >12 and ≤16, and the total pore volume of pores each having a pore radius at which a is ≤16 is within a range of 1.6-2.5 cc/g. The calcium carbonate-silica composite material is produced by mixing sodium silicate with a slurry containing calcium chloride and calcium sulfate in a prescribed ratio to obtain calcium silicate and reacting the calcium silicate with carbon dioxide. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a calcium carbonate-silica composite material having both the excellent characteristics of calcium carbonate and the excellent characteristics of synthetic silica, and a suitable production method thereof. Specifically, a silica-calcium carbonate composite material characterized by combining the excellent functions of calcium carbonate such as high whiteness and the excellent functions of silica such as high specific surface area and high oil absorption, and suitable production thereof Regarding the method.

  In papermaking, fine particles made of inorganic materials other than pulp fibers are often added for the purpose of paper modification. Inorganic materials used in these are called inorganic fillers, which improve optical properties such as whiteness, prevent ink from penetrating during printing due to the high oil absorption of the filler itself, and improve paper smoothness. According to the purpose of improving, etc., it is used for each application depending on the characteristics of each type of inorganic filler.

  In recent years, demand for paper with low density (bulk) and high printability has increased due to the need to address environmental issues, the need for cost reduction during transportation, and the demand for quality improvements from paper users. Development of fillers that improve the performance is desired. As a method for making low-density paper, there is a method in which a bulky filler having many pores is inserted between pulp fibers and the paper has pores derived from the filler.

  In addition, as a method of improving the printability of paper, a method of improving the whiteness and opacity of paper using a filler having high whiteness, or a method of absorbing ink during printing using a filler having high oil absorption. There is a method for improving the effect of preventing ink back-through and bleeding. Patent Document 1 discloses that the oil absorption of the filler depends on the distribution of the pore volume of the filler and the pore volume. In order to obtain the ink absorption effect due to the high oil absorption, the pore radius is disclosed. Ink absorption through pores of 10,000 Angstroms or less is important.

  Fillers used for papermaking include talc, clay, titanium oxide, calcium carbonate, and silica. In recent years, there has been a shift from acidic papermaking, which produces paper near pH 4.5, to neutral papermaking, which produces paper at pH 7.0 to 8.5. Calcium carbonate is not used under acidic papermaking conditions because it reacts and decomposes with acid, but neutral papermaking is less expensive than other fillers and is widely used because of its high whiteness. ing.

  Calcium carbonate includes heavy calcium carbonate obtained by crushing and classifying crystalline limestone mined in a mine, and light calcium carbonate produced by carbonating calcium hydroxide with carbon dioxide or sodium carbonate. . This light calcium carbonate has three types of crystals: aragonite crystals, calcite crystals, and vaterite crystals. The crystal shapes are needle-like aragonite crystals, cube-like calcite crystals, and vaterite crystals. Become spherical. The aragonite crystal can be further agglomerated into a corn shape, thereby improving the yield in papermaking. Vatelite crystals have a high light scattering effect and an even higher effect of improving paper opacity. Furthermore, light calcium carbonate is less likely to reduce the strength of the paper when added as a filler than silica, which will be described later. Therefore, it is easy to blend lightly, and a bulky effect can be obtained. Because of its various crystal shapes, low cost and excellent economic efficiency, high whiteness, and high stability in the neutral range, neutral papermaking contains a lot of light calcium carbonate. It's being used.

  However, the printability of paper made with calcium carbonate has a great effect of preventing show-through due to improved whiteness and opacity of the paper, but the ink absorbability is insufficient due to insufficient ink absorption. There is a problem that the improvement against the strikethrough is insufficient.

  On the other hand, silica is also used as a paper filler in neutral papermaking. Silica used as a filler is generally produced by a neutralization reaction between alkali alkali silicate and a mineral acid typified by sulfuric acid. That is, the silica produced in this manner is a secondary aggregated particle having an amorphous structure in which primary particles are aggregated, and therefore does not have a fixed shape and is a porous material. Due to this characteristic of porosity, it has a high specific surface area, high liquid adsorption ability, and high adsorption power. Therefore, when paper is made using silica as a filler, it is possible to make a paper that is bulky compared to other fillers and has a high effect of preventing ink penetration during printing. However, silica is less white than calcium carbonate.

  Research has been conducted for the purpose of obtaining a material having high whiteness and oil absorption by making use of the characteristics of both calcium carbonate and silica. For example, a material has been proposed in which an alkali silicate is neutralized with a mineral acid in the presence of calcium carbonate and silica is supported or coated on the surface of the calcium carbonate particles (see, for example, Patent Documents 2 to 4). However, since a temperature raising step is required for aging, and in order to make the pH from the time of reaction to the end of the reaction alkaline, the precipitated primary particles of the silica become too large and the oil absorption is not increased. Since the pore volume does not increase, there is a problem in that it is difficult to produce a bulky effect of paper. Further, in the above production method, when sulfuric acid, which is a general mineral acid, is used, a reaction with calcium carbonate occurs, and calcium sulfate is generated and precipitated as an impurity together with silica precipitation, which causes scaling, and hydrochloric acid is added. When used, there is a problem that calcium carbonate is eluted as calcium chloride by reaction.

  Furthermore, a technique for producing a calcium carbonate-silica composite by adding silica particles during the process of producing calcium carbonate by carbonizing calcium hydroxide with carbon dioxide has been proposed (see, for example, Patent Document 5). However, in this method, the amount of silica that can be supported on calcium carbonate is small, and the molar ratio of calcium carbonate to silica is 55:45 to 99: 1. When the ratio of silica to calcium carbonate is low, the pore volume of the composite is reduced, and there is a problem in that the ink absorbency and bulk effect when paper is made are reduced.

  In addition, as another technique for obtaining a material using calcium carbonate and silica, calcium carbonate-silica is obtained by obtaining calcium silicate by a reaction between a calcium raw material and sodium silicate and reacting the calcium silicate with carbon dioxide gas. There are techniques for obtaining composites.

  However, in this method, when calcium chloride is used as the calciumaceous raw material, the obtained calcium carbonate-silica composite has a peak in a small range of a pore radius of 1000 to 3000 angstroms in the pore size distribution, It has only a low pore volume.

  In addition, when calcium sulfate is used as the calciumaceous raw material, the obtained calcium carbonate-silica composite has a pore size distribution peak in the range of a pore radius of 10,000 angstroms or more. Therefore, although the total pore volume is increased, the pore volume having a pore radius of 10,000 angstroms or less that contributes to oil absorption is low, and it is difficult to obtain high oil absorption.

  In addition, the technology of changing the crystal quality of calcium silicate obtained by the reaction of calcium sulfate and sodium silicate by hydrothermal reaction to increase the pore volume has been studied. There existed a problem that cost, such as this calorie | heat amount and pressure | voltage resistant equipment, became high.

Japanese Patent No. 3084125 JP 2006-307229 A JP 2007-70164 A JP 2005-281925 A JP 2003-20223 A

  Accordingly, an object of the present invention is to provide a calcium carbonate-silica composite material that has high oil absorption and high bulkiness effect of paper used as a filler in order to improve printability.

The present inventors have continued intensive studies to solve the above problems. In a method of obtaining calcium carbonate-silica composite material by obtaining calcium silicate by reaction of calcium raw material with sodium silicate and reacting the calcium silicate and carbon dioxide, calcium chloride and sulfuric acid are used as calcium raw materials. Use calcium in the reaction at a specific mixing ratio, concentration of calcium-based raw material, molar ratio (SiO ₂ / Na ₂ O) and silica (SiO ₂ ) concentration in sodium silicate, calcium-based raw material and sodium silicate As a result of examining the conditions such as the reaction time, the composite material has a high pore volume with a pore radius of 10000 angstroms or less, and an optimum filler for neutral papermaking has been found, and the present invention has been completed.

That is, the present invention is a calcium carbonate-silica composite,
(1) Calcium carbonate and silica are in a molar ratio of 25:75 to 40:60,
(2) The pore radius r of the pores of the composite is represented by the following formula: r = 10 ^{(16 + a) / 8} angstrom, and a is a pore having a pore radius in the range of −3 to 23 When the volume is measured by mercury intrusion method,
(2-1) If the difference in a compares the pore volume V _a of each pore radius range divided to be 1, the pore radius range the V _a is the maximum is greater than a 12 The sum of the pore volumes of pores having pore radii that are within the range of 16 or less and (2-2) a is 16 or less is in the range of 1.6 to 2.5 cc / g.
This is a calcium carbonate-silica composite.

  The present invention is a composite having many pores and high oil absorbency due to the effects of the constituent calcium carbonate and silica. Since it is highly oil-absorbing, it is excellent in ink absorbability, and since it has many pores, it is bulky, so when it is made as a filler, it is possible to obtain a paper that is bulky and has high printability.

  The present invention is a composite material composed of calcium carbonate and silica, not simply a mixture of calcium carbonate and silica, but a composite in which particles are formed in a state where calcium carbonate and silica are aggregated with each other. is there.

  Since the silica constituting the present invention is amorphous and has many pores, it exhibits high oil absorption. However, if the proportion of silica constituting the calcium carbonate-silica composite of the present invention (hereinafter also simply referred to as “composite”) is large, the amount of oil absorption does not increase, and calcium carbonate and silica are in a molar ratio. When the ratio is 25:75 to 40:60, more preferably 25:75 to 30:70, a high oil absorption can be obtained. This is presumed to be because the pore distribution of the composite is in a state suitable for oil absorption due to the balance of pores derived from calcium carbonate and silica. In other words, if the ratio between calcium carbonate and silica is out of the above range, a composite having a pore distribution and volume as described below cannot be obtained, and thus a high oil absorption cannot be obtained.

The composite of the present invention has a pore radius in the range of −3 to 23 when the pore radius r of the pore of the composite is expressed by the following formula: r = 10 ^{(16 + a) / 8} angstrom the pore volume of the pores, as measured by mercury porosimetry, a comparison of the pore volume V _a of each pore radius range difference a is divided to be 1, the V _a is at most A pore radius range is in a segment range where a is greater than 12 and less than or equal to 16.

Pore radius range the V _a is maximum, a = 12 since the smaller the total volume of pores in the case in (r = 3162 angstroms) below the pore radius range in addition to a decrease in oil absorption Both bulkiness is also reduced. Moreover, since the following pore pore radius 10000 Å contributes to the oil-absorbing, pore radius range the _{V a} is the maximum is in the range exceeding the a = 16 (r = 10000 Å) In this case, the entire pore volume becomes large and the composite becomes bulky, but the pore volume of 10,000 angstroms or less becomes small, and the oil absorption of the composite decreases. The pore radius range in which V _a is the maximum in that a better oil absorption amount and a bulky effect can be obtained is a segment range in which a is greater than 13 (r = 4217 angstroms) and not greater than 15 (r = 7499 angstroms). It is preferable that it exists in.

  The composite of the present invention is in the range of 1.6 to 2.5 cc / g when the total pore volume of pores having pore radii where a in the above formula is 16 or less. When a composite having a pore volume with a total pore volume of less than 1.6 cc / g is used for papermaking as a filler, the pore volume of the entire composite is low. As a result, the bulk specific volume is reduced, and the bulky effect of the paper cannot be expected. In addition, the oil absorbability is reduced, and the effect of preventing ink back-through and bleeding is insufficient, so that the printability is reduced. On the other hand, in the study by the inventors of the present invention, in the composite of calcium carbonate and silica, the total value of the pore volumes of pores having a pore radius with a being 16 or less is 2.5 cc / g. It is virtually impossible to do this. In view of obtaining a higher oil absorption and a bulky effect, it is preferable that the total value of the pore volume of pores having a pore radius with a being 16 or less is 1.7 cc / g or more. Moreover, what is 2.0 cc / g or less is easier to manufacture.

  Of the components constituting the composite of the present invention, the crystalline structure of calcium carbonate is usually composed of aragonite crystals that are acicular crystals and / or vaterite crystals that are spherical crystals, and is cubic. The calcite crystal of crystal structure is not included. When calcite crystals are included, the pore volume tends to decrease, and the pore pattern and volume that the composite of the present invention has are unlikely. In the composite of the present invention, in many cases, aragonite crystals and vaterite crystals are in the range of 0: 100 to 90:10 (mass ratio). In order to add to the composite particles the improvement in yield due to the aragonite crystals and the whiteness and opacity improvement effects due to the light scattering properties of the vaterite crystals, it must contain both aragonite crystals and vaterite crystals. In particular, the aragonite crystal and the vaterite crystal are preferably 50:50 to 85:15.

  Since the composite of the present invention has a pore distribution and volume as described above, it exhibits a high oil absorption, and the oil absorption is usually 150 to 200 [mL / 100 g] or more, preferably 160 [mL / 100 g] or more. It is also possible. When the amount of oil absorption is 150 [mL / 100 g] or more, when paper is used as a filler, the effect of ink back-through and bleeding is sufficient. In addition, in the composite of calcium carbonate and silica, it is difficult to make the oil absorption more than 200 [mL / 100 g], and in many cases, it is 170 [mL / 100 g] or less.

  The complex of the present invention has a large apparent specific volume, usually 3.7 mL / g or more. Therefore, a good bulky effect can be obtained when used as a paper filler.

  Next, the method for producing the calcium carbonate-silica composite of the present invention will be described below. However, the calcium carbonate-silica composite of the present invention is not limited to that produced by this production method, and is not limited to any production method. It may be manufactured.

A preferred production method for producing the composite of the present invention is to mix a sodium silicate aqueous solution with a slurry containing calcium chloride and calcium sulfate in a molar ratio of 30:70 to 55:45. This is a method in which calcium silicate is produced and then the calcium silicate and carbon dioxide are reacted (hereinafter, this production method is also referred to as “production method of the present invention”). In the following description, the concentration of Ca, Na, and the like may be expressed as a converted value as an oxide (CaO, Na ₂ O, etc.) regardless of the actual existence form.

  In this method, first, a calcium raw material composed of calcium chloride and calcium sulfate is dispersed in water to obtain a slurry (hereinafter also referred to as “calcium raw material slurry”). The calcium raw material slurry has a molar ratio of calcium chloride to calcium sulfate of 30:70 to 55:45, and more preferably 40:60 to 50:50. When the ratio of calcium chloride and calcium sulfate is outside this range, the maximum peak position of the pore volume is outside the preferred range, making it difficult to obtain a composite of the present invention, and high oil absorption and bulkiness. It cannot be a complex that can be exhibited.

  The calcium-based raw material slurry is preferably 6 to 9 [g / 100 mL] as a CaO equivalent concentration. If the CaO equivalent concentration is less than 6 [g / 100 mL], it is not preferable because calcite crystals are produced in the constituent ratio of the calcium carbonate crystals after carbonation, and if it exceeds 9 [g / 100 mL], the slurry viscosity during the reaction Becomes high and sufficient stirring cannot be obtained. The method for preparing the calcium-based raw material slurry is not limited, but it can be easily prepared to a slurry having a target concentration by a method of adjusting the capacity by adding water after calcium sulfate is dispersed in a calcium chloride aqueous solution.

  In the production method of the present invention, a sodium silicate aqueous solution is mixed with the above calcium raw material slurry. This mixing produces calcium silicate in the reaction solution (mixed solution). On the contrary, when the calcium raw material slurry is mixed with sodium silicate, an agglomerate having the calcium raw material as a core is generated, causing a problem that the reaction becomes incomplete.

  When mixing sodium silicate, a method of obtaining a calcium silicate slurry by adding sodium silicate continuously to the calcium-based raw material slurry while stirring sufficiently is preferable.

As sodium silicate to be mixed, the molar ratio of SiO ₂ and Na ₂ O is preferably SiO ₂ / Na ₂ O = 2.0 to 3.0, more preferably 2.2 to 2.7. is there.

The amount of sodium silicate is preferably added so that the molar ratio of Na ₂ O with respect to CaO is _CaO / Na 2 O = _1.0~1.2. Thereby, it becomes easy to make the molar ratio of calcium carbonate and silica of the composite finally obtained be in the range of 25:75 to 40:60. As described above, when the molar ratio of calcium carbonate and silica is out of the above range, the pore volume distribution is affected, and when the molar ratio of calcium carbonate increases, the distribution of large pore radii of 10,000 angstroms (a = 16) or more. As a result, the total pore volume increases, but the pore volume with a pore radius of 10,000 angstroms or less that contributes to oil absorption decreases. On the contrary, when the molar ratio of silica increases, the volume of pores of 10,000 angstroms or less increases, but the overall pore volume decreases, so that bulkiness cannot be expected.

The sodium silicate of silica (SiO ₂₎ concentration is preferably 5.0~15.0 [g / 100mL]. If the amount is less than 5.0 [g / 100 mL], the amount of the sodium silicate solution to be added increases, which is not realistic. If the amount exceeds 15.0 [g / 100 mL], the concentration of the calcium silicate slurry generated by the reaction is high. This is not preferable because the viscosity of the slurry rises and stirring becomes insufficient.

  The reaction for obtaining the calcium silicate can be performed at room temperature. If the reaction is performed at a slurry temperature of less than 10 degrees Celsius or greater than 60 degrees Celsius, the crystal ratio after carbonation changes and the abundance ratio of calcite crystals increases, which is not preferable.

  In addition, it is preferable to carry out the reaction by adding the sodium silicate in a time of 50 to 70 minutes. This affects the production rate of the calcium silicate. When the addition reaction of the sodium silicate is completed in less than 50 minutes or more than 70 minutes, the pore volume distribution after carbonation is suitable. This is not preferable because it is out of range.

  In the production method of the present invention, the calcium silicate obtained as described above and carbon dioxide (carbon dioxide gas) are reacted (carbonation reaction) to obtain a calcium silicate-silica composite.

  In the carbonation reaction, the method of reacting calcium silicate and carbon dioxide gas is not particularly limited. Preferably, the calcium silicate slurry obtained by mixing sodium silicate with the calcium-based raw material slurry as described above is used. The raw material can be used as it is, and carbon dioxide gas can be blown into it.

  In the carbonation reaction by blowing carbon dioxide, it is preferable to blow carbon dioxide with sufficient stirring at room temperature. Since the carbonation reaction proceeds sufficiently at room temperature, there is no need for temperature operation. Rather, carbon dioxide gas is difficult to dissolve in a high-temperature slurry, and the carbonation reaction takes a very long time, which is not efficient.

  The blowing of carbon dioxide gas may be performed until substantially all of the calcium silicate is converted to calcium carbonate (and silica). The end point of the carbonation reaction can be grasped by monitoring the pH of the reaction solution that the neutralization reaction in the slurry has been completed.

  The calcium carbonate-silica composite thus obtained becomes a suspension of particles in which calcium carbonate and silica are aggregated with each other. This suspension may be used as it is in the papermaking process, but it is preferable to perform solid-liquid separation by filtration using a filter paper or membrane filter for a small scale and a belt filter or drum filter for a large scale. This is for the purpose of removing salts that are by-products generated by the carbonation reaction, and excess salts may change into insoluble metal salts in the papermaking process, which may cause troubles such as scale. Because. In addition, it is more preferable to perform an operation for removing excess salt, such as washing the cake obtained by solid-liquid separation.

  Depending on the use of the obtained calcium carbonate-silica composite, for example, when used as a filler in a papermaking process, a coarse particle exceeding 150 μm is used by using a vibrating sieve or a screen in order to remove large grains. Is preferably removed. Of course, the particle diameter for sieving may be appropriately set according to the use of the calcium carbonate-silica composite.

  According to the production method of the present invention, the average particle size of the obtained composite is usually 25 to 45 μm. When used as a filler for neutral papermaking, the yield to pulp fibers is best when the average particle size is in this range. On the other hand, it is also possible to control the particle shape by the stirring strength during production, and the structure of the particle is a mixture of calcium carbonate and silica, so the composite obtained after the reaction is wet pulverized You may adjust to an arbitrary average particle diameter by a machine.

  Further, the calcium carbonate-silica composite of the present invention can be used for other purposes than fillers for neutral paper such as rubber fillers and thermal paper fillers.

  EXAMPLES Hereinafter, examples will be shown to describe the present invention more specifically, but the present invention is not limited to these examples. The measuring method of each characteristic value of the plasma calcium carbonate-silica composite material in the present invention is shown below.

  Molar ratio of calcium carbonate to silica: Analysis was performed using a fluorescent X-ray analyzer (ZSX Primus II manufactured by Rigaku).

Measurement of pore volume distribution: Measured according to JIS R1655 using a mercury porosimeter (Thermo Electron Pascal 240). The evaluation of the measurement results was performed by dividing the pore radius r by the following formula: r = 10 ^{(16 + a) / 8} angstrom, the a in the range of −3 to 23, and the difference of a in the above formula being 1. each pore radius range, was calculated pore volume V _a in each classification range. That is, the pore volume (V ₋₂ ) of pores having a pore radius (42 to 56 angstroms) where a is −3 to −2 and the pore radius (56 to 75) where a is −2 to −1. pore volume of pores having a _{angstroms) (V -1), ····,} a pore volume of pores having a pore radius (56,234 to 74,989 Å) to be 22 to 23 a _{(V 23)} I asked for each. In the calculation of each section pore volume V _a, the pore volume of pores having a pore radius which is a segment point is included in the pore volume of the side having a smaller pore radius than the said section points It was supposed to be. The significant number in this measurement is 3 digits.

  Oil absorption: According to JIS K5101-13-1.

  Crystalline identification: Analysis was performed using an X-ray diffractometer (RINT-1400, manufactured by Rigaku).

  Apparent specific volume: The powder obtained by drying the sample is aligned with a particle size of 150 um sieve and then tamped using a graduated cylinder, and the volume is measured. The volume of was measured.

Example 1
A slurry composed of 1.4 L of a calcium chloride aqueous solution having a CaCl ₂ concentration of 10.65 [g / 100 mL] and 240 g of calcium sulfate (dihydrate gypsum) and having a molar ratio of CaCl ₂ and CaSO ₄ of 50:50 was added to the reaction vessel ( The inner diameter was 190 mm, the height was 320 mm, and the baffle plate was attached. Dilution water was added so that the total amount was 2 L. Sodium silicate (SiO ₂ / Na ₂ O = 2.65, SiO ₂ concentration of 10.97 [g / 100 mL] so that the molar ratio CaO / Na ₂ O = 1.1 is obtained with sufficient stirring at room temperature. ] 3.2 L was continuously added over 1 hour to obtain a calcium silicate slurry.

  4 L of the obtained calcium silicate slurry was put in a carbonation container (inner diameter 125 mm, height 495 mmH, with baffle plate), and carbon dioxide gas was 0.36 [L / L from the bottom of the tower with sufficient stirring at room temperature. min. The carbonation reaction was carried out. The reaction was terminated when the pH of the slurry reached 6.5.

The obtained calcium carbonate-silica composite slurry was separated with a sieve having an opening of 150 μm and coarse particles were filtered, then filtered with a commercially available 5A filter paper, and dried overnight with a 110 ° C. drier. Various physical properties of this dried product were evaluated. As a result, the pore volume of pores having a pore radius in which the molar ratio of calcium carbonate to silica is 29:71 and a is in the range of ₋₃ to ₂₃ (total value from V ₋₂ to V ₂₃ ) is 1. .91 is a [cc / g], of which _(the total value from _{V -2} to _{V 16)} a pore volume of pores having a pore radius in the range of -3～16 is 1.76 [cc / G]. When comparing pore volume V _a of each segment range in this range, the V _a is maximum 13 <pore volume (V ₁₄₎ of the pores having a pore radius which becomes a ≦ 14 met It was. The pore volume (V _a ) in each of these division ranges is shown in Table 1.

  The calcium carbonate-silica composite had an oil absorption of 165 [mL / 100 g], an apparent specific volume of 4.1 [mL / g], and a calcium carbonate crystalline ratio of aragonite: batelite = 80: 20.

Example 2
Example 1 A slurry composed of 1.1 L of a calcium chloride aqueous solution having a CaCl ₂ concentration of 10.65 [g / 100 mL] and 290 g of calcium sulfate (dihydrate gypsum) and having a molar ratio of CaCl ₂ and CaSO ₄ of 40:60 It was put in the same reaction vessel as that used in the above and diluted water was added so that the total amount was 2 L. Sodium silicate (SiO ₂ / Na ₂ O = 2.57, SiO ₂ concentration 10.27 [g / 100 mL] so that the molar ratio CaO / Na ₂ O = 1.1 is obtained with sufficient stirring at room temperature. ) 3.3 L was continuously added over 1 hour to carry out the reaction to obtain a calcium silicate slurry.

  4 L of the obtained calcium silicate slurry was put in the same carbonation vessel as that used in Example 1, and carbon dioxide gas was 0.36 [L / min from the bottom of the tower while stirring sufficiently at room temperature. . The carbonation reaction was carried out. The reaction was terminated when the pH of the slurry reached 6.5.

The obtained calcium carbonate-silica composite slurry was separated with a sieve having an opening of 150 μm and coarse particles were filtered, then filtered with a commercially available 5A filter paper, and dried overnight with a 110 ° C. drier. Various physical properties of this dried product were evaluated. As a result, the pore volume of pores having a pore radius in which the molar ratio of calcium carbonate to silica is 30:70 and a is in the range of ₋₃ to ₂₃ (total value from V ₋₂ to V ₂₃ ) is 1. The pore volume (the total value from V- ₂ to V16) of pores having a pore radius in which a is in the range of _-3 to ₁₆ is 1.73 [cc / g]. / G]. When comparing pore volume V _a of each segment range in this range, the V _a is maximum 14 <pore volume (V ₁₅₎ of the pores having a pore radius which becomes a ≦ 15 met It was. The pore volume (V _a ) in each of these division ranges is shown in Table 1.

  The calcium carbonate-silica composite had an oil absorption of 160 [mL / 100 g], an apparent specific volume of 3.8 [mL / g], and a calcium carbonate crystalline ratio of aragonite: batterite = 60: 40.

Example 3
Example 1 A slurry composed of 1.4 L of a calcium chloride aqueous solution having a CaCl ₂ concentration of 10.15 [g / 100 mL] and 240 g of calcium sulfate (dihydrate gypsum) and having a molar ratio of CaCl ₂ and CaSO ₄ of 50:50 It was put in the same reaction vessel as that used in the above and diluted water was added so that the total amount was 2 L. Sodium silicate (SiO ₂ / Na ₂ O = 2.22, SiO ₂ concentration 9.68 [g / 100 mL] so that the molar ratio CaO / Na ₂ O = 1.1 is obtained with sufficient stirring at room temperature. ) 3.3 L was continuously added over 1 hour, and a calcium silicate slurry was obtained by reaction.

  4 L of the obtained calcium silicate slurry was put in the same carbonation vessel as that used in Example 1, and carbon dioxide gas was 0.36 [L / min. The carbonation reaction was carried out. The reaction was terminated when the pH of the slurry reached 6.5.

The obtained calcium carbonate-silica composite slurry was separated with a sieve having an opening of 150 μm and coarse particles were filtered, then filtered with a commercially available 5A filter paper, and dried overnight with a 110 ° C. drier. Various physical properties of this dried product were evaluated. As a result, the pore volume (total value from V- ₂ to V23) of pores having pore radii in which the molar ratio of calcium carbonate to silica is 30:70 and a is _-3 to ₂₃ is 2.45. [cc / g] of which the pore volume (the total value from V- ₂ to V16) of pores having a pore radius in which a is in the range of _-3 to ₁₆ is 1.92 [cc / g ]Met. In this range, when the pore volume V _a in each division range is compared, the maximum value of V _a is the pore volume (V ₁₄ ) of a pore having a pore radius satisfying 14 <a ≦ 15. there were. The pore volume (V _a ) in each of these division ranges is shown in Table 1.

  The calcium carbonate-silica composite had an oil absorption of 155 [mL / 100 g], an apparent specific volume of 4.1 [mL / g], and the calcium carbonate crystal was only vaterite.

Example 4
Example 1 A slurry composed of 1.4 L of a calcium chloride aqueous solution having a CaCl ₂ concentration of 10.15 [g / 100 mL] and 240 g of calcium sulfate (dihydrate gypsum) and having a molar ratio of CaCl ₂ and CaSO ₄ of 50:50 It was put in the same reaction vessel as that used in the above and diluted water was added so that the total amount was 2 L. Sodium silicate (SiO ₂ / Na ₂ O = 2.74, SiO ₂ concentration 12.97 [g / 100 mL] so that the molar ratio CaO / Na ₂ O = 1.1 is obtained with sufficient stirring at room temperature. ) 2.9 L was continuously added over 1 hour, and a calcium silicate slurry was obtained by reaction.

  4 L of the obtained calcium silicate slurry was put in the same carbonation vessel as that used in Example 1, and carbon dioxide gas was 0.36 [L / min. The carbonation reaction was carried out. The reaction was terminated when the pH of the slurry reached 6.5.

The obtained calcium carbonate-silica composite slurry was separated with a sieve having an opening of 150 μm and coarse particles were filtered, then filtered with a commercially available 5A filter paper, and dried overnight with a 110 ° C. drier. Various physical properties of this dried product were evaluated. As a result, the pore volume (total value from V- ₂ to V23) of pores having a pore radius in which the molar ratio of calcium carbonate to silica is 26:74 and a is in the range of _-3 to ₂₃ is The pore volume of the pores having a pore radius of 2.21 [cc / g], of which a is −3 to 16, was 1.65 [cc / g]. When comparing pore volume V _a of each segment range in this range, the V _a is maximum 14 <pore volume (V ₁₅₎ of the pores having a pore radius which becomes a ≦ 15 met It was. The pore volume (V _a ) in each of these division ranges is shown in Table 1.

  The oil absorption of this calcium carbonate-silica composite was 150 [mL / 100 g], the apparent specific volume was 4.1 [mL / g], and the calcium carbonate crystal was only vaterite.

Comparative Example 1
The same reaction vessel as that used in Example 1 was charged with 2.0 L of calcium chloride aqueous solution having a CaCl ₂ concentration of 14.53 [g / 100 mL], and diluted water was added so that the total amount was ₂ L. Sodium silicate (SiO ₂ / Na ₂ O = 2.52, SiO ₂ concentration 10.79 [g / 100 mL] so that the molar ratio CaO / Na ₂ O = 1.1 with sufficient stirring at room temperature ) 3.3 L was continuously added over 1 hour to carry out the reaction to obtain a calcium silicate slurry.

  4 L of the calcium silicate slurry obtained here is put in the same carbonation vessel as that used in Example 1, and carbon dioxide gas is 0.36 [L from the lower part of the tower while sufficiently stirring at room temperature. / Min.] To perform carbonation by blowing. The reaction was terminated when the pH of the slurry reached 6.5.

The obtained calcium carbonate-silica composite slurry was separated with a sieve having an opening of 150 μm and coarse particles were filtered, then filtered with a commercially available 5A filter paper, and dried overnight with a 110 ° C. drier. Various physical properties of this dried product were evaluated. As a result, the pore volume (total value from V- ₂ to V23) of pores having a pore radius in which the molar ratio of calcium carbonate to silica is 39:61 and a is in the range of _-3 to ₂₃ is 1. .48 [cc / g], and the pore volume (total value from V- ₂ to V16) of pores having a pore radius in which a is in the range of _-3 to ₁₆ is 1.35 [ cc / g]. When comparing pore volume V _a of each segment range in this range, the V _a is maximum 9 <pore volume (V ₁₀₎ of the pores having a pore radius which becomes a ≦ 10 met It was. The pore volume (V _a ) in each of these division ranges is shown in Table 1.

  The calcium carbonate-silica composite had an oil absorption of 130 [mL / 100 g], an apparent specific volume of 3.5 [mL / g], and a calcium carbonate crystalline ratio of aragonite: calcite = 10: 90.

Comparative Example 2
Example 1 A slurry comprising 2.0 L of a calcium chloride aqueous solution having a CaCl ₂ concentration of 11.38 [g / 100 mL] and 100 g of calcium sulfate (dihydrate gypsum) and having a molar ratio of CaCl ₂ and CaSO ₄ of 80:20 In the same reactor used in 3.5 L of sodium silicate (SiO ₂ / Na ₂ O = 2.61, SiO 2 concentration 9.84 [g / 100 mL]) so that the molar ratio CaO / Na ₂ O = 1.2 is obtained while sufficiently stirring at room temperature. Was continuously added over 1 hour to carry out the reaction to obtain a calcium silicate slurry.

  4 L of the obtained calcium silicate slurry was put in the same carbonation vessel as that used in Example 1, and carbon dioxide gas was 0.36 [L / min. The carbonation reaction was carried out. The reaction was terminated when the pH of the slurry reached 6.5.

The obtained calcium carbonate-silica composite slurry was separated with a sieve having an opening of 150 μm and coarse particles were filtered, then filtered with a commercially available 5A filter paper, and dried overnight with a 110 ° C. drier. Various physical properties of this dried product were evaluated. As a result, the pore volume (total value from V- ₂ to V23) of pores having a pore radius in which the molar ratio of calcium carbonate to silica is 32:68 and a is in the range of _-3 to ₂₃ is 1. .31 [cc / g], of which the pore volume (total value from V- ₂ to V16) of pores having a pore radius in which a is in the range of _-3 to ₁₆ is 1.29 [cc / g ]Met. When comparing pore volume V _a of each segment range in this range, the pore volume (V ₁₁₎ of the pores of V _a is maximum with a pore radius which is a 10 <a ≦ 11 met It was. Pore volume in each of these divided ranges (V _a) are shown in Table 1.

  The calcium carbonate-silica composite had an oil absorption of 135 [mL / 100 g], an apparent specific volume of 3.7 [mL / g], and a calcium carbonate crystalline ratio of aragonite: calcite = 70: 30.

Comparative Example 3
CaCl ₂ concentration 10.65 [g / 100mL] calcium chloride solution 1.7 L, made of calcium sulfate (gypsum) 200 g, implementing the slurry molar ratio of CaCl ₂ and CaSO ₄ becomes 60:40 Example 1 The same reaction vessel as that used in the above was added, and diluted water was added so that the total amount was 2 L. Sodium silicate (SiO ₂ / Na ₂ O = 2.57, SiO ₂ concentration 10.27 [g / 100 mL] so that the molar ratio CaO / Na ₂ O = 1.1 is obtained with sufficient stirring at room temperature. ) 3.3 L was continuously added over 1 hour to carry out the reaction to obtain a calcium silicate slurry.

  4 L of the obtained calcium silicate slurry was put in the same carbonation vessel as that used in Example 1, and carbon dioxide gas was 0.36 [L / min from the bottom of the tower while stirring sufficiently at room temperature. The carbonation reaction was carried out. The reaction was terminated when the pH of the slurry reached 6.5.

The obtained calcium carbonate-silica composite slurry was separated with a sieve having an opening of 150 μm and coarse particles were filtered, then filtered with a commercially available 5A filter paper, and dried overnight with a 110 ° C. drier. Various physical properties of this dried product were evaluated. As a result, the pore volume of pores having a pore radius in which the molar ratio of calcium carbonate to silica is 27:73 and a is in the range of ₋₃ to ₂₃ (total value from V ₋₂ to V ₂₃ ) is 1.69 [cc / g], of which the pore volume (the total value from V- ₂ to V16) of pores having a pore radius in which a is in the range of ₋₃ to ₁₆ is 1.60 [cc / g g]. When comparing pore volume V _a of each segment range in this range, the pore volume (V ₁₃₎ of the pores of V _a is maximum with a pore radius which is a 12 <a ≦ 13 met It was. The pore volume (V _a ) in each of these division ranges is shown in Table 1.

  The oil absorption of this calcium carbonate-silica composite was 145 [mL / 100 g], the apparent specific volume was 4.0 [mL / g], and the calcium carbonate crystal was aragonite: calcite = 90: 10.

Comparative Example 4
Example 1 A slurry comprising 0.5 L of an aqueous calcium chloride solution having a CaCl ₂ concentration of 11.38 [g / 100 mL] and 390 g of calcium sulfate (dihydrate gypsum), and having a molar ratio of CaCl ₂ and CaSO ₄ of 20:80 It was put in the same reaction vessel as that used in the above and diluted water was added so that the total amount was 2 L. Sodium silicate (SiO ₂ / Na ₂ O = 2.57, SiO ₂ concentration 10.27 [g / 100 mL] so that the molar ratio CaO / Na ₂ O = 1.1 is obtained with sufficient stirring at room temperature. ) 3.3 L was continuously added over 1 hour to carry out the reaction to obtain a calcium silicate slurry.

  4 L of the obtained calcium silicate slurry was put in the same carbonation vessel as that used in Example 1, and carbon dioxide gas was 0.36 [L / min from the bottom of the tower while stirring sufficiently at room temperature. The carbonation reaction was carried out. The reaction was terminated when the pH of the slurry reached 6.5.

The obtained calcium carbonate-silica composite slurry was separated with a sieve having an opening of 150 μm and coarse particles were filtered, then filtered with a commercially available 5A filter paper, and dried overnight with a 110 ° C. drier. Various physical properties of this dried product were evaluated. As a result, the pore volume (total value from V- ₂ to V23) of pores having a pore radius in which the molar ratio of calcium carbonate to silica is 37:63 and a is in the range of _-3 to ₂₃ is 2.11 [cc / g], of which the pore volume (the total value from V- ₂ to V16) of pores having a pore radius in the range of ₋₃ to ₁₆ is 1.11 [ cc / g]. When comparing the pore volume V _a in each section within this range, the maximum V _a is the pore volume (V ₁₃ ) of pores having a pore radius satisfying 17 <a ≦ 18. It was. The pore volume (V _a ) in each of these division ranges is shown in Table 1.

  The oil absorption of this calcium carbonate-silica composite was 120 [mL / 100 g], the apparent specific volume was 3.6 [mL / g], and the calcium carbonate crystal was aragonite: batterite = 30: 70.

Comparative Example 5
A slurry composed of 450 g of calcium sulfate (dihydrate gypsum) was placed in the same reaction vessel as used in Example 1, and diluted water was added so that the total amount was 2 L. Sodium silicate (SiO ₂ / Na ₂ O = 2.52, SiO ₂ concentration 10.79 [g / 100 mL] so that the molar ratio CaO / Na ₂ O = 1.1 with sufficient stirring at room temperature ) 3.3 L was continuously added over 1 hour to carry out the reaction to obtain a calcium silicate slurry.

4 L of the obtained calcium silicate slurry was put in the same carbonation vessel as that used in Example 1, and carbon dioxide gas was 0.36 [L / min from the bottom of the tower while stirring sufficiently at room temperature. The carbonation reaction was carried out. The reaction was terminated when the pH of the slurry reached 6.5. Thereafter, the slurry was separated into coarse particles with a sieve having an opening of 150 μm, filtered through a commercially available 5A filter paper, and dried overnight with a dryer at 110 degrees Celsius. Various physical properties of this dried product were evaluated. As a result, the molar ratio of calcium carbonate and silica 40: 60, _(total value from _{V -2} to _{V 23)} a pore volume of pores having a pore radius in the range of -3～23 is 0.643 [cc / g], of which the pore volume (the total value from V- ₂ to V16) of pores having a pore radius where a is in the range of _-3 to ₁₆ is 0.354. [Cc / g]. When comparing pore volume V _a of each segment range in this range, the V _a is maximum 19 <pore volume (V ₂₀₎ of the pores having a pore radius which becomes a ≦ 20 met It was. The pore volume (V _a ) in each of these division ranges is shown in Table 1.

  The calcium carbonate-silica composite had an oil absorption of 75 [mL / 100 g], an apparent specific volume of 2.0 [mL / g], and the calcium carbonate crystal was only vaterite.

Comparative Example 6
Light calcium carbonate was slurried, coarse particles were separated with a sieve having an opening of 150 μm, filtered through a commercially available 5A filter paper, and dried for a whole day and night in a dryer at 110 degrees Celsius. Various physical properties of this dried product were evaluated. As a result, the pore volume (the total value from V- ₂ to V23) of pores having a pore radius in which a is in the range of _-3 to ₂₃ is 0.953 [cc / g], of which The pore volume (total value from V- ₂ to V16) of pores having a pore radius where a is in the range of _-3 to ₁₆ was 0.908 [cc / g]. When comparing pore volume V _a of each segment range in this range, the V _a is maximum 14 <pore volume (V ₁₅₎ of the pores having a pore radius which becomes a ≦ 15 met It was. The pore volume (V _a ) in each of these division ranges is shown in Table 1.

  The oil absorption of the calcium carbonate was 65 [mL / 100 g], the apparent specific volume was 2.0 [mL / g], and the calcium carbonate crystalline ratio was aragonite: calcite = 30: 70.

Comparative Example 7
Precipitated calcium carbonate 150g dispersed in water in the same reaction vessel as that used in Comparative Example 1, wherein the SiO ₂ concentration 16.03 [g / 100mL], Na 2 O concentration 5.69 of [g / 100 mL] After adding 955 mL of sodium silicate solution, water was added to make the total volume 3 L. The mixed slurry was heated with sufficient stirring to 85 ° C.

A 10% sulfuric acid solution was added to the mixed slurry. The sulfuric acid was added at a constant rate so that the final pH after addition of sulfuric acid was 7.5 and the total sulfuric acid addition time was 120 minutes. The slurry was separated from the coarse particles with a sieve having an opening of 150 μm, filtered with a commercially available 5A filter paper, and dried overnight with a dryer at 110 degrees Celsius. Various physical properties of this dried product were evaluated. As a result, the pore volume (total value from V- ₂ to V23) having a pore radius where a is in the range of _-3 to ₂₃ is 1.12 [cc / g], of which a is- The pore volume (total value from V- ₂ to V16) having a pore radius in the range of 3 to ₁₆ was 0.799 [cc / g]. When comparing pore volume V _a of each segment range in this range, the V _a is maximum 16 <pore volume of pores having a pore radius which becomes a ≦ ₁₇ (V ₁₇₎ met It was. Pore volume in each of these divided ranges (V _a) are shown in Table 1.

  The calcium carbonate-silica composite had an oil absorption of 120 [mL / 100 g], an apparent specific volume of 2.5 [mL / g], and a calcium carbonate crystalline ratio of aragonite: calcite = 30: 70.

  The composition of each raw material in Examples 1 to 4 and Comparative Examples 1 to 6 is shown in Table 2, and the physical properties of the obtained calcium carbonate-silica composite are shown in Table 3.

2 is a histogram showing the pore volume distribution of the calcium carbonate-silica composite obtained in Example 1. 6 is a histogram showing the pore volume distribution of the calcium carbonate-silica composite obtained in Example 2. 6 is a histogram showing the pore volume distribution of the calcium carbonate-silica composite obtained in Example 3. 6 is a histogram showing the pore volume distribution of the calcium carbonate-silica composite obtained in Example 4. 6 is a histogram showing the pore volume distribution of the calcium carbonate-silica composite obtained in Comparative Example 1. 6 is a histogram showing the pore volume distribution of the calcium carbonate-silica composite obtained in Comparative Example 2. 6 is a histogram showing the pore volume distribution of the calcium carbonate-silica composite obtained in Comparative Example 3. 6 is a histogram showing the pore volume distribution of the calcium carbonate-silica composite obtained in Comparative Example 4. 6 is a histogram showing the pore volume distribution of the calcium carbonate-silica composite obtained in Comparative Example 5. The histogram which shows the pore volume distribution of the calcium carbonate shown in the comparative example 6. FIG. 8 is a histogram showing the pore volume distribution of the calcium carbonate-silica composite obtained in Comparative Example 7.

Claims (5)

A calcium carbonate-silica composite,
(1) Calcium carbonate and silica are in a molar ratio of 25:75 to 40:60,
(2) The pore radius r of the pores of the composite is represented by the following formula: r = 10 ^{(16 + a) / 8} angstrom, and a is a pore having a pore radius in the range of −3 to 23 When the volume is measured by mercury intrusion method,
(2-1) If the difference in a compares the pore volume V _a of each pore radius range divided to be 1, the pore radius range the V _a is the maximum is greater than a 12 The sum of the pore volumes of pores having pore radii that are within the range of 16 or less and (2-2) a is 16 or less is in the range of 1.6 to 2.5 cc / g.
A calcium carbonate-silica composite characterized by the above.   2. The calcium carbonate-silica composite according to claim 1, wherein the calcium carbonate component comprises aragonite crystals and / or vaterite crystals.   The calcium carbonate-silica composite according to claim 1 or 2, which is a filler for neutral paper.   A sodium silicate aqueous solution is mixed with a slurry containing calcium chloride and calcium sulfate in a molar ratio of 30:70 to 55:45 to produce calcium silicate, and then the calcium silicate and carbon dioxide are mixed. A method for producing a calcium carbonate-silica composite, characterized by reacting.   The method according to claim 4, wherein the calcium carbonate-silica composite is a filler for neutral paper.

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