JP2006082985A - Apatite sol and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide apatite sol excellent in dispersion stability containing apatite particles of ≤100 nm average particle diameter, and a method for producing it. <P>SOLUTION: This apatite sol comprises apatite particles of ≤100 nm average particle diameter, and contains a polymerized phosphate and an aluminate. The average particle diameter of the apatite particles is 100 nm or smaller, the maximum particle diameter is 300 nm or smaller and the particle diameter of 80% or more particles in the total falls in the range of 20-100 nm. The method for producing the apatite sol by reacting sodium phosphate and a soluble calcium salt comprises a step of obtaining apatite slurry with ≤1 mass% concentration by reacting sodium phosphate and a soluble calcium salt, a step of concentrating the apatite slurry, and adding polymerized phosphate and an aluminate to the apatite slurry. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apatite sol and a method for producing the same, and more particularly to an apatite sol useful as a dispersant for suspension polymerization and a dispersant for suspension polymerization of toner, and a method for producing the same.

  The use of inorganic fine particle slurry as a polymerization dispersant in suspension polymerization is widely known, and as a polymerization dispersant, in addition to calcium phosphate and apatite, calcium carbonate, magnesium hydroxide, precipitated barium sulfate, and the like are used. in use. Among them, calcium phosphate and apatite are used as a dispersant for suspension polymerization of many resins because the solubility of the dispersant adhering to the surface of the polymer particles in the acid washing step after the completion of polymerization is the best.

  For example, it is used as a dispersant for suspension polymerization of styrene resin, AS resin (acrylonitrile / styrene), ABS resin (acrylonitrile / butadiene / styrene), acrylic resin, and the like. Usually, the particle diameter of the polymer particles obtained by suspension polymerization is around 100 μm, and the particle diameter of the dispersant for suspension polymerization is about 0.5 to 5 μm (see Patent Document 1). .

  On the other hand, toner used as an electrophotographic copying or printer developer has been conventionally produced by a pulverization method. That is, after melting the base polymer, the magnetic powder and the colorant are mixed and kneaded, and the kneaded product is cooled, ground and classified. However, in the production of toner by the pulverization method, there is a limit to the miniaturization of particles after pulverization, and enormous energy is required for pulverization and classification. The particle size of the pulverized toner thus obtained was about 10 μm even if the particle size was fine.

  In recent years, in the field of copying machines, the demand for higher image quality has increased, and the transition from analog copying machines to digital copying machines is rapidly progressing. A digital copying machine performs copying by reading an optical image with a CCD (Charge Coupled Device), converting it into digital image information, and irradiating the drum with a laser beam. For this reason, in a digital copying machine, it is necessary to reduce the particle size of toner in order to faithfully reproduce fine dots drawn on a photosensitive drum and obtain a high-quality hard copy.

  With toner particles obtained by the pulverization method, there is a limit to reducing the particle size of the toner, and research and development of a suspension polymerization method toner has been started as a toner production technique that replaces the pulverization method. As a method for producing a toner by a polymerization method, for example, a solution in which a styrene monomer is mixed with a pigment, a dye, a magnetic powder, a polymerization initiator, and the like is prepared, and a monomer mixed solution is added to an aqueous slurry in which calcium phosphate is dispersed, While performing high-speed shearing stirring with a homomixer or the like, the monomer is polymerized by continuing stirring for a predetermined temperature and time. After completion of the polymerization reaction, an acid is added to dissolve calcium phosphate adhering to the surface of the polymer particles, and then neutralized, washed with water, separated and dried to obtain a polymerized toner. The particle diameter of the polymerized toner thus obtained is 5 to 10 μm, and a toner having a sharp particle size distribution of 5 μm or less is desired. (See Patent Document 2)

Although there is no clear relationship between the particle size (Dr) of the polymerized toner obtained by the suspension polymerization method and the particle size (Dd) of the polymerization dispersant, one criterion is that Dr / Dd = 100 or more. It is said. That is, when polymer particles having a size of about 10 μm are obtained from suspension polymerization, the particles of the suspension polymerization dispersant need to have an average particle size of 0.1 μm (100 nm) or less.
Japanese Patent Laid-Open No. 7-102005 JP 2001-249491 A

  Apatite and calcium phosphate particles are obtained by drying a precipitate formed by reacting sodium phosphate with a calcium salt. Aggregation occurs by drying, and apatite or calcium phosphate particles having an average particle size of 100 nm or less are dried particles. It is difficult to get as.

  On the other hand, apatite or calcium phosphate having an average particle size of 100 nm or less can be obtained as a sol or a suspension. However, suspensions of apatite and calcium phosphate tend to agglomerate and gelate when the particle size is small, and change with time is large. So far, it has been difficult to maintain a sol-like suspension in a stable state. Met.

The present invention has been made in view of such background art, and provides an apatite sol excellent in dispersion stability containing apatite particles having an average particle diameter of 100 nm or less and a method for producing the same.
The present invention also provides a dispersant for suspension polymerization comprising the apatite sol.
Furthermore, the present invention provides a dispersant for suspension polymerization of a polymerized toner comprising the above apatite sol.

  That is, the present invention is characterized by containing apatite particles having an average particle size of 100 nm or less, a maximum particle size of 300 nm or less, and a particle size of 80% or more of the total particles in the range of 20 to 100 nm. It is an apatite sol.

In addition, the present invention is an apatite sol characterized in that it contains apatite particles having an average particle diameter of 100 nm or less, and contains a polymerized phosphate and an aluminate.
The content of the apatite particles is preferably 3 to 15% by mass.
It is preferable that the polymerized phosphate is sodium hexametaphosphate and the aluminate is sodium aluminate.

The present invention also provides a process for producing an apatite sol by reacting sodium phosphate with a soluble calcium salt to obtain an apatite slurry having a concentration of 1% by mass or less by reacting sodium phosphate with a soluble calcium salt, A method for producing an apatite sol, comprising a step of concentrating a slurry and a step of adding a polymerized phosphate and an aluminate to an apatite slurry.
The apatite slurry is preferably concentrated by ultrafiltration.

Furthermore, the present invention is a dispersant for suspension polymerization comprising the apatite sol described above.
Furthermore, the present invention is a suspension polymerization dispersant for polymerized toner comprising the apatite sol.

ADVANTAGE OF THE INVENTION According to this invention, the apatite sol excellent in long-term dispersion stability containing the apatite particle | grain with an average particle diameter of 100 nm or less can be provided.
The present invention can provide a production method for easily obtaining the apatite sol having excellent long-term dispersion stability.
The present invention can provide a dispersant for suspension polymerization comprising the apatite sol and a dispersant for suspension polymerization of a polymerized toner.

Hereinafter, the present invention will be described in detail.
The apatite sol of the present invention contains apatite particles having an average particle size of 100 nm or less, and can contain a stable phosphate state by containing a polymerized phosphate and aluminate as a dispersion stabilizer. It is characterized by.

The apatite in the present invention is hydroxyapatite (3Ca ₃ (PO ₄ ) ₂ · Ca (OH) ₂ ).
The average particle diameter of the apatite particles is 100 nm or less, preferably 30 to 70 nm. If it is larger than 100 nm, the monomer droplets are coalesced during suspension polymerization, and the polymer particle size becomes large.

  The apatite particles have an average particle size of 100 nm or less, a maximum particle size of 300 nm or less, preferably 30 to 70 nm, and a particle size of 20 to 100 nm in the range of 80% or more, preferably 90% or more. More preferably, it contains 95% or more of particles. When the particle diameter is within this range, it is suitable for stably dispersing the droplet diameter of the monomer during suspension polymerization between 1 to 10 μm.

  The content of the apatite particles contained in the apatite sol of the present invention is 3 to 15% by mass, preferably 5 to 10% by mass. If it is less than 3% by mass, the monomer concentration at the time of suspension polymerization reaction becomes low and the efficiency of the reactor deteriorates, which is not preferable, and if it exceeds 15% by mass, the apatite particles are easily gelled and the stability is deteriorated.

  In the method for producing an apatite sol of the present invention, it is important to use a soluble phosphate and a soluble calcium salt as raw materials. For example, when slaked lime is used, it is not preferable because a precipitate of calcium carbonate is generated in part. Usually, phosphoric acid, sodium hydroxide and calcium chloride are used. While adding sodium hydroxide and stirring the calcium chloride aqueous solution adjusted to basic, the aqueous phosphate solution adjusted to basic is added dropwise to produce apatite precipitate.

  In this case, the reaction temperature may be around room temperature. When the reaction is carried out under heating conditions, the particle size of the resulting apatite becomes large, which is not preferable. The slurry concentration of apatite obtained from the reaction is 1% by mass or less, and the reaction is preferably carried out in a dilute aqueous solution. After completion of the reaction, the slurry is allowed to stand to separate the supernatant and the precipitate. Next, after adding polymerized phosphate and aluminate as a dispersant stabilizer to the separated precipitate and stirring uniformly, the precipitate is further concentrated by an ultrafiltration membrane, and the apatite concentration is 3% by mass or more. A slurry is obtained.

  According to the study results of the present inventors, apatite particles having an average particle size of 100 nm or less are very active, and when concentrated and the slurry concentration is increased, the particles agglomerate and lose fluidity, and gelled into a purine form. End up. Therefore, as a result of intensive studies on the prevention of gelation, it was found that the combined use of polymerized phosphate and aluminate is effective in preventing gelation. Although the mechanism of preventing gelation is not clearly understood, a change in the pH of the slurry during the long-term storage has been observed with polymerized phosphate alone. It seems that maintaining the pH in the alkaline region and sufficiently performing mechanical dispersion treatment does not cause pH change during long-term storage, and as a result, maintains a stable fluid state.

  The content of the polymerized phosphate contained in the apatite sol of the present invention is 5 to 20% by mass, preferably 8 to 15% by mass, based on the solid content. The content of aluminate is 0.5 to 5% by mass, preferably 0.5 to 3% by mass, based on the solid content.

  The apatite slurry of the present invention can be used as a dispersant for suspension polymerization in monomer suspension polymerization. As a monomer to be subjected to suspension polymerization, for example, one or two or more types of suspension polymerization which are selected from substituted or unsubstituted styrene, (meth) acrylic acid esters, acrylonitrile, vinyl esters and olefins are possible. A monomer etc. can be mentioned.

  The amount of the dispersant for suspension polymerization used varies depending on the physical properties and the conditions for suspension polymerization, but in many cases the apatite (in terms of solid content) is 0.1 to 1.0% by mass, preferably 0.8. The range of 15 to 0.8 mass% is desirable. In addition, when using the dispersant for suspension polymerization of the present invention, other stabilizers, for example, water-soluble polymer compounds such as polyvinyl alcohol, CMC, gelatin, and surface activity such as sodium dodecylbenzenesulfonate are used. An agent, a pH adjuster, a specific gravity adjuster, a viscosity adjuster, or the like may be used in combination as appropriate.

  The apatite slurry of the present invention can be used as a suspension polymerization dispersant for polymerized toner. Specifically, after mixing raw materials such as monomers such as styrene and acrylic acid, colorants (pigments, dyes), charge control agents, polymerization initiators, etc., high-speed shearing with a homomixer, etc. This solution is added to an aqueous solution containing an apatite sol and heated while stirring to conduct a polymerization reaction. After the polymerization reaction is completed, the polymer particles are washed with acid, washed with water, and then dried. Thus, polymerized toner particles can be obtained.

Hereinafter, the present invention will be described more specifically with reference to examples. % Is based on mass unless otherwise specified.
Example 1
(1) 147 g of calcium chloride dihydrate is dissolved in 50 L of deionized water. After complete dissolution, 160 g of 25% NaOH aqueous solution was slowly added to adjust the basicity. The basic calcium chloride aqueous solution thus obtained is designated as solution A.
(2) Dilute 100 g of 85% phosphoric acid with 10 L of deionized water. Further, 320 g of 25% NaOH aqueous solution was added to adjust the basicity. The basic phosphoric acid aqueous solution thus obtained is designated as solution B.
(3) While vigorously stirring the liquid A, the entire amount of the liquid B was quickly added to carry out the reaction. The reaction was performed at room temperature.
(4) After addition of the entire amount, the mixture was further stirred for 10 minutes, and then the reaction solution was allowed to stand to precipitate the resulting apatite precipitate.
(5) After allowing to stand until the volume of precipitation becomes 20 L or less, the supernatant liquid is taken out, 200 g of 10% sodium hexametaphosphate and 40 g of 10% sodium hydroxide are added to the precipitated phase, and stirring is performed to obtain a uniform suspension. did.
(6) Concentrate the calcium phosphate suspension obtained in (5) above using an ultrafiltration membrane (Asahi Kasei Co., Ltd., ultrafiltration module SIP-1013) until the suspension becomes 1 L or less. It was.
(7) 100 g of 10% sodium hexametaphosphate solution, 40 g of 10% sodium hydroxide solution and 20 g of 10% aqueous sodium aluminate solution (Na / Al: 1.5) were added to the calcium phosphate suspension obtained in (6) above. After the addition, dispersion was performed with an ultrasonic homogenizer to obtain an apatite sol in which apatite was uniformly dispersed.

Example 2
In Example 1, an apatite sol in which apatite was uniformly dispersed was obtained in the same manner as in Example 1 except that 10 g of the 10% sodium aluminate aqueous solution (Na / Al: 1.5) in Step (7) was added. It was.

Reference example 1
In Example 1, an apatite sol was obtained in the same manner as in Example 1 except that the sodium aluminate solution was not added in Step (7).

Comparative Example 1
Apatite slurry (manufactured by Nippon Kagaku, supertite: apatite concentration 10%, average particle size 1.42 μm (1420 nm)) was wet crushed with a bead mill (manufactured by Ashizawa Finetech, bead size 0.5 mm). When the slurry 20L was subjected to 6-pass pulverization at a supply rate of 350 m1 / min, the average particle size was 0.37 μm (370 nm). From this result, even when wet milling with a bead mill was repeated 6 times, particles having an average particle size of 100 nm or less, which was the object of the present invention, were not obtained, and it was impossible to produce an apatite sol by grinding.

Test analysis After the prepared apatite sol was dissolved in hydrochloric acid, the contents of Ca and P were measured by ICP emission analysis. Using this measurement result, the CaO content and PO ₄ content were determined.
The slurry concentration is a value estimated from the CaO content considering that the calcium content in the liquid is present as Ca ₃ (PO ₄ ) ₂ .

Analysis Method 5 ml of the prepared apatite sol was collected, dissolved in 5 ml of hydrochloric acid, and deionized water was added to the surface of the 100 ml volumetric flask. 10 ml of this solution was collected, and deionized water was added to the surface of the 100 ml volumetric flask. Further, 10 ml of this solution was collected, and deionized water was added to the surface of the 100 ml volumetric flask. This is used as a test solution.

  In the measurement, a calibration curve was prepared using a standard solution containing 10 ppm, 5 ppm, and 1 ppm of Ca and P, and the contents of Ca and P in the test solution were determined. Each measurement wavelength is Ca: 317.933 nm and P: 177.495 nm.

CaO content (%) = Ca (ppm) × 56.08 / 40.08 × 0.2
PO ₄ content (%) = P (ppm) × 94.97 / 30.97. × 0.2
Slurry concentration (%) = CaO (%) ÷ 3 × 310.17 / 56.08
Table 1 shows the analysis values thus obtained.

Measurement of pH The pH of the slurry was measured with a glass electrode type hydrogen ion concentration meter (IM-22P) manufactured by Toa Denpa Kogyo Co., Ltd.

Particle size distribution The particle size distribution of the apatite sol was measured under the condition of a refractive index of 1.63 using Microtrac (UPA) manufactured by Nikkiso Co., Ltd. The results are shown in Table 1 and FIGS. 1 shows Example 1, FIG. 2 shows Example 2, and FIG.

Stability The apatite sol prepared in each example and reference example was allowed to stand at room temperature and a stability test was performed. The time until the sol loses fluidity and gels is that the gel prepared in Reference Example 1 gels in 7 days, whereas the gel prepared in Examples 1 and 2 exhibits fluidity even after 28 days. And had improved stability.

Example 3
Production Method of Polymerization Toner 40 parts of the apatite sol (abatite concentration 10%) of Example 1 was mixed with 300 parts of ion-exchanged water to obtain a uniform aqueous solution. (Liquid A)
70 parts of styrene, 30 parts of butyl methacrylate, 7 parts of carbon black, 1 part of a dye, and 6 parts of a polymerization initiator (succinic peroxide) were mixed and further dispersed with a ball mill to obtain a uniform mixed solution. (Liquid B)

  Liquid B was added to liquid A, and high-speed shearing stirring was performed with a homomixer while maintaining the pH of the liquid at 9 or more, and liquid B was finely dispersed in water. Next, this dispersion was transferred to a reaction vessel equipped with a stirrer, and polymerization was performed at 80 ° C. for 6 hours with stirring. After the polymerization, the polymer dispersion slurry was neutralized with hydrochloric acid to dissolve the apatite adhering to the polymer particles. The polymer particles were separated, washed with water, separated and dried to obtain a polymer toner having an average particle diameter of 7 μm.

  Since the apatite sol of the present invention contains apatite particles having an average particle diameter of 100 nm or less and has excellent dispersion stability, it can be used as a suspension polymerization dispersant and a suspension polymerization dispersant for polymerized toner. it can.

FIG. 3 is a graph showing the particle size distribution of the apatite sol of Example 1. 6 is a graph showing the particle size distribution of an apatite sol of Example 2. FIG. FIG. 4 is a view showing a particle size distribution of an apatite sol of Reference Example 1.

Claims (9)

  An apatite sol comprising an apatite particle having an average particle size of 100 nm or less, a maximum particle size of 300 nm or less, and a particle size of 80% or more of the total particles in a range of 20 to 100 nm.   An apatite sol comprising apatite particles having an average particle diameter of 100 nm or less and containing a polymerized phosphate and an aluminate.   The apatite sol according to claim 1 or 2, wherein the content of the apatite particles is 3 to 15% by mass.   The apatite sol according to claim 2, wherein the polymerized phosphate is sodium hexametaphosphate.   The apatite sol according to claim 2, wherein the aluminate is sodium aluminate.   In the method for producing an apatite sol by reacting sodium phosphate and a soluble calcium salt, a step of reacting sodium phosphate and a soluble calcium salt to obtain an apatite slurry having a concentration of 1% by mass or less, a step of concentrating the apatite slurry, A method for producing an apatite sol, comprising a step of adding a polymerized phosphate and an aluminate to an apatite slurry.   The method for producing an apatite sol according to claim 6, wherein the apatite slurry is concentrated by ultrafiltration.   A dispersant for suspension polymerization comprising the apatite sol according to any one of claims 1 to 5.   A dispersant for suspension polymerization of a polymerized toner comprising the apatite sol according to any one of claims 1 to 5.

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