JP3998793B2 - Precipitated silica and method for producing the same - Google Patents

Description

【００９７】
用途例１〜７、比較用途例１、２
本発明の沈降シリカを充填剤として使用した場合の補強効果を確認するため、実施例、比較例の各沈降シリカを以下の配合で混練りし、加硫物について応用物性を測定した。
【００９８】
ＳＢＲ１７１２ ９６．２５重量部
ＢＲ０１ ３０．０ 重量部
沈降シリカ ７０．０ 重量部
シランカップリング剤Ｓｉ６９ ７．０ 重量部
ステアリン酸 ２．０ 重量部
パラフィンワックス １．０ 重量部
芳香族系プロセスオイル ７．０ 重量部
老化防止剤６Ｃ １．０ 重量部
亜鉛華 ４．０ 重量部
加硫促進剤 ＣＺ １．５ 重量部
硫黄 ２．０ 重量部
この配合物を１６０℃、１５分間の条件で加硫した。
【００９９】
応用物性値として、レオメトリックス社製動的粘弾性測定装置ＡＲＥＳにより、２５℃、周波数１５Ｈｚの条件で歪み分散を測定し、歪み１％のときの貯蔵弾性率（Ｅ’）を採用した。また、ＪＩＳ Ｋ６２５１ に準拠して引っ張り試験を実施し、伸び３００％時の引っ張り応力（Ｍ300）を採用した。
【０１００】
表２には、応用物性の測定結果を比較例１の沈降シリカについての測定値を１００とした場合の相対値で併記した。実施例１〜７の沈降シリカについてはいずれも１００以上の値であって、Ｅ’とＭ300を両立していることが理解される。
【０１０１】
【表２】

【０１０２】
【発明の効果】
以上の説明により理解されるように、本発明の沈降性シリカは、種々の基材、特に、樹脂、エラスマー等に充填材として添加した場合に、動的粘弾性と引っ張り強度を両立してバランスのとれた補強効果を発現する。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel precipitated silica and a method for producing the same. Specifically, it is a precipitated silica that exhibits excellent reinforcing performance, particularly when filled in a base matrix such as an elastomer or a resin.
[0002]
[Prior art]
Silicon dioxide obtained by neutralizing alkali silicate with acid and collecting and drying solid components in the obtained reaction slurry is called precipitated silica or white carbon, and is a reinforcing filler for various elastomers, especially synthetic rubber, It is used in a wide range of applications, such as agrochemical carriers, newsprint fillers, synthetic resin compounding agents, thickeners such as paints, adhesives and printing inks, and toothpaste compounding agents.
[0003]
Precipitated silica is required to exhibit balanced performance in its reinforcing effect, particularly when used as a filler for elastomers and resins among the above applications.
[0004]
It has been pointed out that conventional precipitated silica, particularly silica having a large specific surface area due to fine particle size, works effectively for one of the physical properties of elastomers and resins, but deteriorates other physical properties instead. . As an example, even when silica having a fine particle size was produced for the purpose of increasing the storage elastic modulus, which is a dynamic physical property, the tensile strength was lowered, and a balanced reinforcing performance could not be obtained.
[0005]
[Problems to be solved by the invention]
Accordingly, there has been a demand for the development of precipitated silica having a balanced reinforcing performance capable of achieving both a high storage elastic modulus and an improvement in tensile strength when filled in a base matrix such as an elastomer or a resin.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have found that the pore distribution of precipitated silica and the effect of silica on the base material when mixed in a base material matrix such as an elastomer or a resin The following findings were obtained regarding the relationship with the reinforcing effect of
[0007]
In the conventional method for producing precipitated silica, when the specific surface area of silica is increased, the particle diameters of the silica particles tend to be uniform. For this reason, the pore size distribution (hereinafter referred to as “pores”) formed by aggregation of the silica particles. There is a tendency for the distribution to be sharp.
[0008]
According to the confirmation of the present inventors, S (CTAB) is 180 to 270 m.²One of the conventional silicas in the / g range is for pores with a peak pore radius between 70 and 100 angstroms, with pore radii between 50 and 70 angstroms before or after, or 100 to 150 angstroms. The volume ratio was relatively small.
[0009]
The reason why such a relationship between the specific surface area and the pore distribution occurs is presumed to be due to the following mechanism. That is, the production process of precipitated silica synthesized by neutralization of an alkaline silicate aqueous solution with a mineral acid is generally divided into three stages. First, (1) nuclear particles are generated. This occurs when the concentration of silica produced by the neutralization reaction exceeds a certain concentration determined by conditions such as the temperature and pH of the reaction system. Next, (2) aggregation occurs after the core particles have grown to some extent. Thereafter, (3) the particle growth further proceeds to obtain the final silica. Silica having a large specific surface area, that is, silica having a small particle diameter, is a silica in which the particle growth of (3) is not sufficiently progressed, and such silica is unlikely to have a difference in particle diameter. There is no difference in the size of the pores, which are voids between particles, and the pore distribution becomes sharp.
[0010]
The reason why the conventional precipitated silica having a large specific surface area cannot achieve balanced reinforcement performance is that the pore distribution becomes sharper. It has been found that when a base matrix such as an elastomer or a resin is filled, it can be improved in the direction of achieving both high storage elastic modulus and improved tensile strength as applied physical properties.
[0011]
Further, such precipitated silica having a large specific surface area and broad pore distribution is obtained by simultaneously adding an aqueous alkali silicate solution and a mineral acid into an aqueous alkali silicate solution at a low temperature to precipitate the silica. After aggregating, it was confirmed that it was obtained by a method of raising the temperature to a high temperature, and the present invention was completed.
[0012]
  That is, the present invention has a specific surface area (S (CTAB)) measured by adsorption of cetyltrimethylammonium bromide (CTAB) of 180 to 270 m.²As for the pore distribution measured by the mercury intrusion method, the ratio of the volume of pores having a pore radius of 50 angstroms or more and 70 angstroms or less to the pore volume having a pore radius of 400 angstroms or less is 10-30%, the volume of pores having a pore radius of more than 70 angstroms and having a pore radius of 100 angstroms or less, 20-40%, and the volume of pores having a pore radius of more than 100 angstroms and less than 150 angstroms Is in the range of 10-30%And the ratio S (BET) / S (PO) of the specific surface area (S (BET)) measured by the nitrogen adsorption method and the specific surface area (S (PO)) measured by the mercury intrusion method is 0.8 to Having a specific surface area of 1.0A precipitated silica is provided.
[0014]
Further, as another advantageous embodiment of the precipitated silica of the present invention, with respect to the pore distribution measured by mercury porosimetry, pores having a pore radius of not less than 50 angstroms and not more than 150 angstroms occupying the pore volume having a pore radius of 400 angstroms or less. Also provided are those having a volume ratio of pores having a radius of 50% or more.
[0015]
  Furthermore, in the present invention, as a method for producing such precipitated silica, the temperature of the reaction system is adjusted to 40 to 7 with an alkali silicate aqueous solution and a mineral acid in an alkali silicate aqueous solution.0At the same time, while keeping the temperature, the silica was precipitated to confirm the aggregation of the silica, and then the temperature of the reaction system was raised to 90-100 ° C.And control the pH to the alkali side.A method for producing precipitated silica is provided.
[0016]
Precipitated silica produced by the method described above has a broad pore distribution despite its large specific surface area. Therefore, when it is filled in an elastomer or resin, it has two properties: dynamic viscoelasticity and tensile strength. It is compatible and can achieve a balanced reinforcement effect in that sense.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The precipitated silica of the present invention has S (CTAB) of 180 to 270 m.²/ G, preferably 190-260 m²/ G is good, more preferably 200 to 250 m²/ G.
[0018]
That is, the value of S (CTAB) is generally an index that is easily correlated with the physical property values of elastomers and resins. Therefore, S (CTAB) is 180m²If it is smaller than / g, the reinforcing effect by silica becomes insufficient, such being undesirable. 270m²When S (CTAB) is greater than / g, the surface activity of the silica is increased, the silica is strongly agglomerated, making it difficult to disperse appropriately, as well as deterioration in filtration performance and adhesion to the container. This is not preferable because it tends to occur and is difficult to handle.
[0019]
The precipitated silica of the present invention has a pore distribution measured by the mercury intrusion method, and has a pore radius having a pore radius of 50 angstroms or more and 70 angstroms or less occupying the volume of pores having a pore radius of 400 angstroms or less. A volume fraction of 10-30%, greater than 70 angstroms, and a pore volume fraction having a pore radius of less than 100 angstroms, 20-40%, and a pore radius greater than 100 angstroms, with a pore radius of less than 150 angstroms The greatest feature is that the volume ratio of the pores is in the range of 10 to 30%.
[0020]
Unlike the conventional silica, the precipitated silica of the present invention that satisfies the specific range described above with respect to the pore distribution measured by the mercury intrusion method represents that the pore distribution is broad while being fine particles.
[0021]
Accordingly, silica having a sharp pore distribution whose ratio of the specific pore volume is outside the range of the present invention has an effect on its reinforcing effect when filled in a base matrix such as elastomer or resin. The two performances of mechanical viscoelasticity and tensile strength cannot be achieved. Moreover, it is difficult to produce precipitated silica having a broader pore distribution than the above values.
[0022]
In the precipitated silica of the present invention, pores having a pore radius exceeding 400 angstroms are not particularly limited.
[0023]
That is, pores having a pore radius of 400 angstroms or less affect the process in which fine silica aggregate particles of the same size are dispersed in an elastomer or resin, but pores having a pore radius larger than 400 angstroms In particular, it was confirmed that pores in excess of 1000 angstroms have no substantial effect on such dispersion processes.
[0024]
The precipitated silica of the present invention is not particularly limited as long as it satisfies the above-described characteristics, but the following aspects are particularly preferable as the precipitated silica of the present invention.
[0025]
In the present invention, the ratio of the volume of pores having a pore radius of 50 angstroms or more and 150 angstroms or less to the volume of pores having a pore radius of 400 angstroms or less is preferably 50% or more. Such a range of pores is an effective factor for dispersing the precipitated silica in the base matrix, and the higher the ratio, the better.
[0026]
In addition, the precipitated silica of the present invention has a specific surface area ratio S (BET) / S of a specific surface area (S (BET)) measured by a nitrogen adsorption method and a specific surface area (S (PO)) measured by a mercury intrusion method. (PO) is preferably from 0.8 to 1.0, particularly preferably from 0.85 to less than 1.0.
[0027]
That is, when the ratio S (BET) / S (PO) of the specific surface area is in the range of 0.8 to 1.0, the precipitated silica is well-kneaded with the elastomer or resin, and the elastomer or resin It is preferable because it is easily broken and dispersed in the kneading process.
[0028]
In general, the size of the nitrogen molecule is considered to be about 4 angstroms. In the nitrogen adsorption method, it is said that the adsorption phenomenon occurs when nitrogen enters the pores having the same size as that of the sample. On the other hand, in the mercury porosimeter of the present invention, since pressure can be applied up to 2000 bar, pores up to a pore radius of 37.5 angstroms are measured. For this reason, in a conventional substance having a fine pore structure such as precipitated silica, the S (BET) value is generally larger than the S (PO) value.
[0029]
On the other hand, in the precipitated silica of the preferred embodiment of the present invention, the S (PO) value is greater than or equal to the S (BET) value, and such silica has fine pores inside the aggregated particles. It is considered that this is a silica with a closed pore, that is, silica having a closed pore in that sense. This is because in the process of silica production described later, fine particles on the outer surface of the aggregated particles are dissolved and the unevenness disappears, and at the same time, the dissolved components precipitate near the pore inlet and block the pore inlet. It is presumed that fine particles and fine pores formed by the fine particles are encapsulated inside. In a simple model, it is envisioned that a thin silica layer is formed on the outer surface of the agglomerated particles. In the measurement of the specific surface area by the nitrogen adsorption method, it is considered that the nitrogen molecules are adsorbed only on the outer surface thin film portion and cannot enter the fine pores confined inside, and the specific surface area value is reduced accordingly. On the other hand, in the mercury intrusion method, a maximum pressure of 2000 bar is applied, so that the pores are measured while breaking the thin-film silica layer on the outer surface of the aggregated particles, and the measurement range extends to the included fine pores. Therefore, it will be larger than the specific surface area by the nitrogen adsorption method.
[0030]
In addition, the following values can be given as preferable powder properties of the precipitated silica of the present invention.
[0031]
Regarding the specific surface area of the silica of the present invention, S (BET) is 180 to 280 m.²/ G and S (PO) are 180 to 300 m²Generally, it is in the range of / g.
[0032]
The volume of pores having a pore radius of 400 angstroms or less of the silica of the present invention is in the range of 0.7 to 2.0 mL / g, preferably in the range of 0.9 to 1.6 mL / g. In this range, moderate dispersion of the silica aggregate particles having the same size as the pore diameter is easily achieved.
[0033]
The dibutyl phthalate oil absorption (hereinafter abbreviated as “DBP oil absorption”) is preferably 100 to 300 ml / 100 g. Within this range, good dispersibility can be obtained during kneading.
[0034]
Furthermore, the apparent specific gravity is preferably in the range of 0.20 to 0.35 g / ml. When in this range, good workability can be obtained during kneading.
[0035]
Furthermore, the water content is preferably 3 to 10 wt%. Within this range, good workability during kneading and good reactivity with the silane coupling agent can be obtained.
[0036]
In the present invention, the method for producing the precipitated silica as described above is not particularly limited, but the following method can be exemplified as a typical production method.
[0037]
That is, the alkali silicate aqueous solution and the mineral acid were simultaneously added to the alkali silicate aqueous solution while keeping the temperature of the reaction system at 40 to 75 ° C. to precipitate silica, and after confirming the aggregation of the silica, the temperature of the reaction system was changed. Examples thereof include a method for producing precipitated silica, characterized in that the temperature is raised to 90 to 100 ° C.
[0038]
As described above, the precipitated silica of the present invention is produced by a so-called wet method in which an alkali silicate is used as a starting material and a mineral acid is added thereto to neutralize and precipitate.
[0039]
The method for producing precipitated silica according to the present invention is a method in which an alkali silicate aqueous solution and a mineral acid are simultaneously added to an alkali silicate aqueous solution whose temperature has been adjusted in advance so that the alkali concentration in the liquid becomes constant and neutralized and precipitated. In contrast to known methods, the method is particularly characterized by a method for controlling the temperature of the reaction system.
[0040]
  In the following description, the temperature of the reaction system is set to 40 to 7 for convenience.0The step of simultaneously adding the alkali silicate aqueous solution and the mineral acid to the alkali silicate aqueous solution while maintaining the temperature is denoted as “low temperature reaction”, and the step of maintaining the temperature at 90 to 100 ° C. after the temperature rise is denoted as “high temperature reaction”.
[0041]
As the alkali silicate aqueous solution used in the method of the present invention, those generally used can be used without any limitation. For example, sodium silicate, potassium silicate, etc. can be used, and sodium silicate is common and preferred. Molar ratio of silica to alkali dissolved in alkali silicate aqueous solution SiO₂/ M₂O (M represents an alkali metal, eg, M = Na, K, etc.) is generally SiO 2₂/ M₂O = 2 to 4 can be used, SiO₂/ M₂O = 3.0 to 3.5 is preferred. The concentration used in the reaction is SiO₂When expressed as a concentration, 10 to 200 g-SiO 2₂It is desirable to dilute to / L with water. In addition, SiO₂Against Al₂O_Three0.1 to 1.0% by weight-Al₂O_Three/ SiO₂It is also possible to use an alkali silicate aqueous solution contained in a concentration of Furthermore, an electrolyte, generally sodium sulfate, may be mixed in the alkali silicate aqueous solution in an amount of about 1 to 100 g / L.
[0042]
The mineral acid used in the method of the present invention is not particularly limited as long as it causes a neutralization reaction with an alkali silicate aqueous solution. Sulfuric acid, hydrochloric acid, nitric acid and the like can be used, and among these, sulfuric acid is versatile and preferable. Generally used sulfuric acid is 200 to 250 g-H.₂SO_FourUsed diluted with water to a concentration of / L.
[0043]
The method for supplying the alkali silicate aqueous solution and the mineral acid to be added is not particularly limited as long as the temperature and pH of the reaction system during the simultaneous addition reaction and the silica concentration in the reaction solution or the reaction slurry can be controlled. That is, an alkali silicate aqueous solution and a mineral acid having appropriate concentrations may be dropped into the reaction solution or reaction slurry from the top, or the supply port may be directly put into the reaction solution. Further, in order to adjust the concentration, water may be separately supplied in addition to the alkali silicate aqueous solution and the mineral acid.
[0044]
Moreover, it is desirable to stir the reaction solution or the reaction slurry so that the concentration of the reaction system becomes uniform. As the stirring method, known methods can be used without particular limitation. For example, the stirring method may be performed by mixing with a stirring blade, or a circulating device that takes out a part of the reaction liquid and mixes it with another part may be used. May be.
[0045]
In the method of the present invention, it is desirable to add the aqueous alkali silicate solution and the mineral acid at the same time so that the alkali concentration in the reaction solution or reaction slurry is constant. Moreover, when this alkali concentration is represented by pH, it is pH 9-11, Preferably, it is pH 9.2-10.5. Therefore, it is desirable to balance the addition concentration, addition rate, etc. of the alkali silicate aqueous solution and the mineral acid so that the pH is in such a range.
[0046]
The method of the present invention is characterized in that the aggregated particles having a broad pore distribution are generated in the low temperature reaction and the fine particles on the outer surface of the aggregated particles are dissolved in the high temperature reaction, but the pH value of the reaction system is set to the alkali side. Control is preferable because the desired pore distribution can be easily obtained and the dissolution of the fine particles can be more easily proceeded.
[0047]
  In the method of the present invention, in the low temperature reaction, when the alkali silicate aqueous solution and the mineral acid are simultaneously added to the alkali silicate aqueous solution, the temperature of the reaction system is set to 40 to 40.70Must be kept at ℃. The temperature is preferably from 45 to 45.70° C, more preferably 50-70 ° C.
[0048]
  When the temperature of the low-temperature reaction is lower than 40 ° C., the reaction rate becomes small and it becomes difficult to control the reaction, which is not preferable. 70If it is higher than ℃, the desired broad pore distribution cannot be obtained..
[0049]
In general, in the production of precipitated silica by simultaneous addition, the particle diameters of silica particles formed are uneven as the temperature of the reaction system is lower. On the contrary, as the temperature increases, silica with a uniform particle size is generated. This is explained by the fact that the higher the temperature of the reaction system, the larger the precipitation limit particle diameter of the silica produced, and the smaller particles dissolve at that temperature. In order to produce a precipitated silica having a pore distribution as defined in the present invention, it is necessary that the particle diameters are moderately irregular. For this reason, it is important to control the temperature in a low-temperature reaction.
[0050]
In the method of the present invention, it is necessary to carry out the high temperature reaction by raising the temperature after confirming that the silica precipitated by the low temperature reaction has aggregated.
[0051]
In general, in the production of precipitated silica by simultaneous addition, when a certain silica concentration according to the temperature and pH of the reaction system is reached, aggregation of precipitated silica particles occurs. Such agglomeration of silica can be confirmed by a sudden viscosity increase phenomenon of the reaction slurry.
[0052]
When the temperature of the reaction system is increased before the silica is aggregated, the fine particles generated by the low-temperature reaction are dissolved before being encapsulated in the aggregated particles, and it is difficult to obtain a desired broad pore distribution.
[0053]
The temperature increase described above may be started at any time as long as it is after silica agglomeration, and the temperature is increased after completion of the addition of a predetermined amount of the alkali silicate aqueous solution and the mineral acid, and the aging time is taken. A high temperature reaction may be carried out.
[0054]
That is, in the high temperature reaction in the method of the present invention, the alkali silicate aqueous solution and the mineral acid may be simultaneously added at 90 to 100 ° C., or the maturation is performed in the sense that the same temperature is maintained without addition. Also good.
[0055]
Aging has the purpose of stabilizing the precipitated precipitated silica, and the time of the high temperature reaction is 30 minutes or more in total of the time of simultaneous addition of the alkali silicate aqueous solution and mineral acid at 90 to 100 ° C. and the time of aging. Thus, it is preferable to take an aging time. More preferably, it is about 35 to 120 minutes.
[0056]
In the method of the present invention, the temperature can be raised without any limitation by any method. For example, steam may be blown into the reaction solution or reaction slurry, or a heating element may be placed in the reaction vessel and heated. Or you may heat with the steam or a heat generating body from the exterior of reaction container.
[0057]
In the method of the present invention, the temperature of the high temperature reaction after the temperature rise needs to be 90 to 100 ° C. Preferably, 92-98 degreeC is good.
[0058]
When the temperature is lower than 90 ° C., the dissolution of the fine particles on the outer surface of the aggregated particles is insufficient and unevenness remains, and the initial biting when kneaded into the elastomer or resin is deteriorated. In addition, it is difficult to achieve conditions exceeding 100 ° C., which is not preferable in terms of heat cost.
[0059]
In the high-temperature reaction, fine particles on the outer surface of the aggregated particles composed of silica particles with irregular particle sizes generated by the low-temperature reaction are dissolved, and the components are deposited near the inlet of the pores of the aggregated particles to form the pores. Presumed to be occluded. As a result, as explained in the model covered with a thin-film silica layer, it is considered that aggregated particles are formed in which pores with a broad pore distribution formed by silica particles with irregular particle sizes are confined inside. .
[0060]
In the present invention, for the purpose of stabilizing the precipitated silica, it is preferable to complete the neutralization reaction by adding only the mineral acid until the pH of the reaction solution becomes 2 to 6 after carrying out the high temperature reaction.
[0061]
In the production method of the present invention, the silica concentration in the reaction slurry at the time when the neutralization reaction is completed and all the silica is precipitated is preferably 30 to 80 g / L, and more preferably 40 to 70 g / L. This is because S (CTAB) can be easily set in the target range.
[0062]
In the present invention, the precipitated silica obtained as described above has an appropriate bulk specific gravity and DBP oil absorption by post-treatment such as filtration, washing and drying. The post-treatment method is not particularly limited, and a known method can be adopted.
[0063]
For example, a method of standing and drying the cake obtained by filtering and washing the reaction slurry with a filter press, a method of spray drying the slurry with an appropriate concentration after filtering and washing the reaction slurry with a filter press, etc. Can be mentioned.
[0064]
In addition, for the purpose of adjusting the bulk specific gravity to a size suitable for the reinforcing filler, pulverization treatment or granulation treatment can be performed using a known method. Furthermore, in order to impart unique performance as a reinforcing filler, it is possible to modify the surface with a silicone oil or the like using a known method.
[0065]
The following are representative embodiments of the method of the present invention.
[0066]
  First, a certain amount of alkali silicate aqueous solution prepared in advance to a predetermined concentration is put in a reaction tank, and 40-70Adjust to the target temperature of ℃. While stirring, the simultaneous addition of the alkali silicate aqueous solution and the mineral acid is started so that the alkali concentration in the liquid becomes constant. First, after confirming that nuclei are precipitated and then agglomeration occurs to increase the viscosity of the reaction slurry, simultaneous addition is temporarily stopped at an arbitrary time, and the temperature is raised. When the target temperature of 90 to 100 ° C. is reached, the simultaneous addition of the alkali silicate aqueous solution and the mineral acid is resumed, or aging is performed at the same temperature. Thereafter, only the mineral acid is added as necessary, and the pH of the reaction slurry is adjusted to 2-6. Finally, the precipitated silica is recovered by filtration, washed with water and dried. Furthermore, a pulverization process, a granulation process, and a surface modification process are performed as needed.
[0067]
[Action]
The precipitated silica provided by the present invention has a high specific surface area and a broad pore distribution. Therefore, when filled in a substrate matrix such as a resin or elastomer, it is appropriately dispersed and balanced in application properties. Is presumed to be expressed.
[0068]
【Example】
The features of the present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the following examples.
[0069]
The measuring method of each physical property value implemented by this invention is shown.
[0070]
(1) Measurement of specific surface area (S (CTAB)) by adsorption of cetyltrimethylammonium bromide (CTAB)
This was carried out in accordance with the method described in ASTM D3765-92.
[0071]
However, since the method of ASTM D3765-92 is a method of measuring S (CTAB) of carbon black, it is a method with some improvements. That is, the carbon black standard ITRB (83.0 m²/ G), prepare a CTAB standard solution separately, standardize the aerosol OT solution, and determine the specific surface area from the amount of CTAB adsorbed by setting the adsorption cross section per molecule of CTAB to 35 square angstroms on the silica surface. Calculated. This is because carbon black and silica have different surface states, and it is considered that there is a difference in the amount of CTAB adsorbed even with the same specific surface area.
[0072]
(2) Measurement of pore distribution and specific surface area (S (PO)) by mercury porosimetry
Measured with a Porosimeter 2000 model manufactured by Carlo Elba. In this apparatus, the contact angle θ = 141.3 ° and the mercury surface tension σ = 480 dyne / cm are employed in the Washburn relational expression. As the pressure was increased to 2000 bar, the measurement range was a pore radius of 37.5 to about 75000 angstroms.
[0073]
(3) Measurement of specific surface area (S (BET)) by nitrogen adsorption method
Based on the theory described in S. Brunauer, PH Emmett, E. Teller, J. Am. Chem. Soc. 60 (1), 309 (1938), it is generally designed and marketed as a simple measurement method called a one-point method. Measuring device (Rapid surface area measuring device SA-1100, manufactured by Shibata Kagaku Kikai Kogyo Co., Ltd.).
[0074]
(4) Measurement of DBP oil absorption
The measurement was performed according to JIS K6220.
[0075]
(5) Measurement of apparent specific gravity
The measurement was performed according to JIS K6220.
[0076]
(6) Measurement of moisture content
The weight change after the sample was dried for 2 hours in a dryer at 105 ° C. was measured and expressed in terms of weight reduction rate.
[0077]
Example 1
Silica to alkali molar ratio SiO₂/ Na₂First, 2.2 L of a sodium silicate solution having a silica concentration of 10 g / L was charged into a 10 L reactor using sodium silicate having O = 3.35. While sufficiently stirring the reaction solution with a stirring blade, the temperature of the reaction solution is heated to 65 ° C., and while maintaining this temperature, a sodium silicate solution having a silica concentration of 90 g / L at the same molar ratio is 36 mL / min. The addition of sulfuric acid having a concentration of 220 g / L was simultaneously started at an addition rate of 6.2 mL / min. After 60 minutes, since it was confirmed that the viscosity in the reaction vessel had increased, the simultaneous addition of the sodium silicate solution and sulfuric acid was interrupted, and the temperature was raised. After 30 minutes, the temperature of the reaction slurry reached 95 ° C. While maintaining this temperature, the simultaneous addition of sodium silicate solution and sulfuric acid was resumed. The addition rate was the same as the reaction at 65 ° C., and the simultaneous addition at 95 ° C. was performed for 65 minutes. After completion of the simultaneous addition, stirring was continued while maintaining 95 ° C., and aging was performed for 5 minutes. Thereafter, sulfuric acid was added at 95 ° C. until the pH reached 3.5. At this time, the silica concentration in the reaction slurry (hereinafter referred to as final silica concentration) was 56 g / L. The reaction slurry was filtered and washed with water, and the recovered silica cake was dried in a 150 ° C. drier.
[0078]
S (CTAB) of the obtained silica is 201m²/ G and S (BET) is 217m²/ G, S (PO) is 231m²/ G. The specific surface area ratio S (BET) / S (PO) is 0.94. In the pore distribution by the mercury porosimeter, the volume of the pores having a pore radius of 400 angstroms or less is 1.27 mL / g, and the proportion of the volume of the pores of 50 to 70 angstroms occupying therein is 11%, 70 to 70%. The volume ratio of 100 angstrom pores was 23%, the volume ratio of 100-150 angstrom pore volumes was 29%, and thus the total ratio of 50-150 angstrom pore volumes was 63%.
[0079]
The above powder physical properties are summarized in Table 1.
[0080]
Example 2
Precipitated silica was produced in the same manner as in Example 1 except that the temperature of the low temperature reaction was 55 ° C. and the simultaneous addition time at high temperature (95 ° C.) was 70 minutes. The final silica concentration of the reaction slurry was 56 g / L.
[0081]
The powder physical properties of the obtained silica are shown in Table 1.
[0082]
Example 3
Precipitated silica was produced in the same manner as in Example 1 except that the temperature of the high temperature reaction was 98 ° C. and the simultaneous addition time at high temperature was 60 minutes. The final silica concentration of the reaction slurry was 55 g / L.
[0083]
The powder physical properties of the obtained silica are shown in Table 1.
[0084]
Example 4
Precipitated silica was produced in the same manner as in Example 1 except that the temperature of the high temperature reaction was 90 ° C., the simultaneous addition time at high temperature was 60 minutes, and the aging time after completion of the simultaneous addition was 20 minutes. The final silica concentration of the reaction slurry was 55 g / L.
[0085]
The powder physical properties of the obtained silica are shown in Table 1.
[0086]
Example 5
Precipitated silica was produced in the same manner as in Example 1 except that the simultaneous addition time at a high temperature (95 ° C.) was 37 minutes and the aging time after completion of the simultaneous addition was 23 minutes. The final silica concentration of the reaction slurry was 52 g / L.
[0087]
The powder physical properties of the obtained silica are shown in Table 1.
[0088]
Example 6
Same as Example 1 except that the simultaneous addition time in the low temperature (65 ° C.) reaction was 90 minutes, the simultaneous addition time in the high temperature (95 ° C.) was 30 minutes, and the aging time after completion of the simultaneous addition was 40 minutes. Precipitated silica was produced by this method. The final silica concentration of the reaction slurry was 55 g / L.
[0089]
The powder physical properties of the obtained silica are shown in Table 1.
[0090]
Example 7
Example: Except that the low temperature reaction temperature was 55 ° C. and simultaneous addition was carried out for 130 minutes at low temperature, then the temperature was raised and simultaneous addition was not carried out at high temperature (95 ° C.), but instead the aging time was 110 minutes. In the same manner as in No. 1, precipitated silica was produced. The final silica concentration of the reaction slurry was 56 g / L.
[0091]
The powder physical properties of the obtained silica are shown in Table 1.
[0092]
Comparative Example 1
The precipitated silica was prepared in the same manner as in Example 1 except that the reaction temperature was constant at 85 ° C., the simultaneous addition time was 115 minutes, and the aging time at the same temperature (85 ° C.) after completion of the simultaneous addition was 10 minutes. Manufactured. The final silica concentration of the reaction slurry was 55 g / L.
[0093]
Table 1 shows the powder physical properties of the obtained silica.
[0094]
Comparative Example 2
Silica to alkali molar ratio SiO₂/ Na₂Using sodium silicate of O = 3.00, first, 7.5 L of a sodium silicate solution having a silica concentration of 40 g / L and 172 g of anhydrous sodium sulfate were charged into a 10 L reaction vessel. While sufficiently stirring the reaction solution with a stirring blade, the reaction solution is heated to a temperature of 40 ° C., and with this temperature maintained, sulfuric acid with a concentration of 220 g / L is added at an addition rate of 20 mL / min for 15 minutes. did. Thereafter, the reaction solution was heated to 95 ° C. in 50 minutes. It was confirmed that the viscosity in the reaction vessel increased during the temperature increase. To the reaction slurry kept at 95 ° C., the same concentration of sulfuric acid was again added for 90 minutes at an addition rate of 4.9 mL / min. The pH of the reaction slurry after completion of the addition of sulfuric acid was 5.5, and the silica concentration in the reaction slurry was 36 g / L. The reaction slurry was filtered and washed with water, and the recovered silica cake was dried in a 150 ° C. drier.
[0095]
Table 1 shows the powder physical properties of the obtained silica.
[0096]
[Table 1]

[0097]
Application examples 1-7, comparative application examples 1, 2
In order to confirm the reinforcing effect when the precipitated silica of the present invention was used as a filler, the precipitated silicas of Examples and Comparative Examples were kneaded with the following composition, and applied physical properties of the vulcanizates were measured.
[0098]
SBR1712 96.25 parts by weight
BR01 30.0 parts by weight
Precipitated silica 70.0 parts by weight
Silane coupling agent Si69 7.0 parts by weight
Stearic acid 2.0 parts by weight
Paraffin wax 1.0 parts by weight
Aromatic process oil 7.0 parts by weight
Anti-aging agent 6C 1.0 part by weight
4.0 parts by weight of zinc white
Vulcanization accelerator CZ 1.5 parts by weight
2.0 parts by weight of sulfur
This blend was vulcanized at 160 ° C. for 15 minutes.
[0099]
As applied physical property values, strain dispersion was measured under the conditions of 25 ° C. and a frequency of 15 Hz using a rheometrics dynamic viscoelasticity measuring device ARES, and the storage elastic modulus (E ′) at a strain of 1% was adopted. Further, a tensile test was carried out in accordance with JIS K6251 and a tensile stress (M300) at an elongation of 300% was adopted.
[0100]
In Table 2, the measurement results of applied physical properties are also shown as relative values when the measured value for the precipitated silica of Comparative Example 1 is taken as 100. All of the precipitated silicas of Examples 1 to 7 have values of 100 or more, and it is understood that both E 'and M300 are compatible.
[0101]
[Table 2]

[0102]
【The invention's effect】
As understood from the above description, the precipitated silica of the present invention balances dynamic viscoelasticity and tensile strength when added as a filler to various substrates, particularly resins and elastomers. Appears excellent reinforcement effect.

Claims (3)

The specific surface area (S (CTAB)) measured by adsorption of cetyltrimethylammonium bromide (CTAB) is 180 to 270 m ² / g, and the pore distribution measured by the mercury intrusion method is fine with a pore radius of 400 angstroms or less. The ratio of the volume of pores having a pore radius of 50 angstroms or more and 70 angstroms or less to the volume of pores is 10 to 30%, and the ratio of the volume of pores having a pore radius of more than 70 angstroms and 100 angstroms or less but 20-40%, and beyond 100 angstroms, Ri range near the proportion of 10-30% of the pore volume with the following pore radius 150 Å and a specific surface area measured by the nitrogen adsorption method (S (BET)) and the specific surface area (S (PO)) measured by mercury porosimetry. BET) / S (PO) is precipitated silica characterized by having a specific surface area to be 0.8 to 1.0. Respect pore distribution measured by mercury porosimetry, according to claim 1 Symbol proportion of pore volume having a pore radius of 50 to 150 Å occupying the volume of the following pore pore radius 400 Å is 50% or more Precipitated silica. Added simultaneously while maintaining the alkali silicate aqueous solution and a mineral acid in the alkali silicate aqueous solution the temperature of the reaction system to forty to seven 0 ° C. silica allowed the precipitate, after confirming the agglomeration of the silica, the temperature of the reaction system 90 the temperature was raised to to 100 ° C., and method for producing a precipitated silica, characterized in that controlling the pH to the alkaline side.