JP2006028246A - Method for producing phenolic resin/silica composite spherical fine particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing composite spherical fine particles whose structure comprising a phenolic resin and silica is controlled, which have silica layers having proper hardness, and whose silica contents are easily controlled. <P>SOLUTION: This method for producing the phenolic resin/silica composite spherical fine particles is characterized by adding an aqueous solution containing an emulsion stabilizer (D) to an organic phase comprising a phenolic resin (A), a silicon compound (B) and an organic solvent (C) to invert and emulsify the organic layer phase, and then thermally curing the obtained fine particles. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing composite spherical fine particles comprising a phenol resin and silica.

As a method of obtaining spherical fine particles in which an organic material and an inorganic material are combined, a method of coating the surface of the spherical fine particles of the organic material with an inorganic material has been proposed (see, for example, Patent Documents 1 and 2). In Patent Document 1, sodium silicate is neutralized with hydrochloric acid in a water suspension of organic polymer spherical fine particles to form silica hydrate. At this time, silica hydrate is precipitated and adsorbed on the surface of the polymer fine particles in the suspension to obtain organic polymer / silica composite spherical fine particles. Further, in Patent Document 2, a phenol resin / silica composite spherical particle having a silica coating layer formed on the surface of the phenol resin particle is obtained by adding a silica sol solution to an aqueous dispersion of the phenol resin spherical particle. In these methods, it is necessary to contain a large amount of sodium silicate or silica sol solution contained in an aqueous suspension or dispersion, which has a disadvantage of being wasted. In addition, the composite spherical fine particles obtained by these methods have a problem that the amount of silica adsorbed on the surface thereof cannot be controlled and the adsorbed silica is easily detached.
On the other hand, it is known that a mixed solution composed of silicon alkoxide, a phenol resin and a solvent is dropped into a basic aqueous solution and hydrolyzed to obtain phenol resin / silica composite fine particles (see Patent Document 3). However, this method has the disadvantage that spherical composite fine particles cannot be obtained, and fusion between the fine particles is likely to occur.

Japanese Patent Application No. 63-25902 Japanese Patent Laid-Open No. 6-23718 JP 9-208210 A

  An object of the present invention is to provide a method for producing composite spherical fine particles in which a structure composed of a phenol resin and silica is controlled, a silica layer having an appropriate hardness is provided, and the silica content is easily controlled. .

As a result of intensive research aimed at achieving the above object, the present inventors have added a water phase to an organic phase composed of a phenol resin and a silicon compound, so that the organic phase is phase-inverted and emulsified to cause phenol resin / silica. The inventors have found that composite spherical fine particles are formed, and have completed the present invention.
That is, in the present invention, an aqueous solution containing an emulsion stabilizer (D) is added to an organic phase containing a phenol resin (A), a silicon compound (B), and an organic solvent (C) to phase-emulsify the organic layer. The present invention relates to a process for producing phenolic resin / silica composite spherical fine particles, wherein the fine particles obtained by heating are cured by heating.
Further, in the present invention, the silica is continuously distributed from the surface to the inside of the phenol resin / silica composite spherical fine particles in which a silica layer or a silica layer containing a resin (high silica-containing layer) is formed in the vicinity of the surface. The present invention relates to a method for producing phenol resin / silica composite spherical fine particles.

  The phenol resin / silica composite spherical fine particles obtained in the present invention have a silica layer with an appropriate hardness on the surface, and are suitably used as a sliding material or a friction material, for example, abrasive grains. Further, in the method for producing spherical fine particles according to the present invention, the silica content of the silica layer can be easily controlled and the fine structure of the silica layer can be controlled as compared with the conventional colloidal silica.

  The phenol resin (A) used in the present invention is obtained by polycondensation of phenols and aldehydes with one of an acidic catalyst or a basic catalyst, followed by vacuum dehydration without neutralization or neutralization. Novolak or resol type phenolic resin. Moreover, a resol type phenol resin is preferable from the viewpoint of easy preparation of spherical fine particles.

  Here, examples of phenols include phenol, cresol, xylenol, m-cresol, m-ethylphenol, resorcin, catechol, hydroquinone, bisphenol A, and the like, and these can be used alone or in combination of two or more. Examples of aldehydes include formalin, paraformaldehyde, trioxane, acetaldehyde, benzaldehyde and the like, and these can be used alone or in combination of two or more.

Examples of the silicon compound (B) used in the present invention include silicon alkoxide, alkyl group-substituted silicon alkoxide and partial polycondensates thereof, silica sol, and silica nanoparticles.
Here, as the silicon alkoxide and the alkyl group-substituted silicon alkoxide, those generally used in silica production by a sol-gel method can be used. Specific examples of the silicon alkoxide include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. Alkyl group-substituted silicon alkoxides include methyltrimethoxysilane, ethyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, phenyltrimethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane. Examples include ethoxysilane and diphenyldiethoxysilane.

  The partial polycondensate can be obtained by a method in which the above silicon alkoxide or alkyl group-substituted silicon alkoxide is mixed and stirred with water, a solvent, and, if necessary, an acid or base catalyst. The polycondensate synthesized in this way is preferably used. From the viewpoints of economy and versatility, commercially available silicon alkoxides or partial polycondensates of alkyl group-substituted silicon alkoxides, for example, Mitsubishi Chemical Corporation Poly (tetramethoxysilane) “MS-51” manufactured by Tama Chemical Co., Ltd. and poly (methyltrimethoxysilane) “MTMS-A” manufactured by Tama Chemical Co., Ltd. are more preferably used.

  The content of the silicon compound (B) in the present invention is defined by the mass% of silica with respect to spherical fine particles having a silica amount contained in the used silicon compound. The content of silica with respect to the composite spherical fine particles is 0.5 to 30% by mass, preferably 0.8 to 20% by mass, and particularly preferably 1 to 15% by mass. When the content is less than 0.5% by mass, it is difficult to form a uniform silica layer on the surface of the spherical fine particles. When the content exceeds 30% by mass, the solution tends to gel during phase inversion emulsification, and spherical fine particles cannot be obtained. There is.

  As the organic solvent (C) in the present invention, an organic solvent that dissolves the phenol resin and is compatible with the silicon compound and water is used. Examples thereof include lower alcohols such as methanol, ethanol and isopropanol, acetone, tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide and the like. These can be used individually or in mixture of 2 or more types. The amount of the organic solvent used is preferably 100 to 500 parts by mass with respect to 100 parts by mass of the phenol resin (A).

  The emulsion stabilizer (D) used in the present invention is used as a protective colloid, and examples thereof include hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, gum arabic, tragacanth rubber, polyvinyl alcohol, sodium alginate and the like. The amount used is preferably 0.04 to 5% by mass, more preferably 0.05 to 3% by mass, and particularly preferably 0.07 to 1% by mass with respect to the phenol resin. The above emulsion stabilizer is preferably prepared in an aqueous solution of 0.03 to 1% by mass and used as an aqueous phase.

  Moreover, in order to easily phase-invert and emulsify the organic layer composed of the above-described phenol resin, silicon compound, and organic solvent, a surfactant can be appropriately added. The surfactant is not particularly limited as long as it is a cationic surfactant, an anionic surfactant, or a nonionic surfactant that can be dissolved in the organic solvent (C). Examples thereof include n-hexadecyltrimethylammonium chloride, n-dodecyltrimethylammonium chloride, and sodium n-dodecylsulfate.

The composite spherical fine particles in the present invention can be produced, for example, as follows. That is, a methanol solution of a silicon compound is dropped into a methanol solution of a phenol resin to form an organic phase. While stirring the organic phase, an aqueous emulsion stabilizer solution (aqueous phase) is slowly added dropwise. The solution gradually became cloudy and gradually became an opaque homogeneous suspension. Next, the obtained suspension is poured into water, a fine powder is precipitated, and the composite spherical fine particles are recovered by centrifugation. Furthermore, the collected spherical fine particles are cured by heating in a water or air fluidized bed.
Further, in order to easily cure the obtained composite spherical fine particles, it is preferable to add a curing agent to the organic phase in advance, and it may be essential. For example, in the case of a novolac type phenol resin, it is necessary to add hexamine. On the other hand, in the case of a resol type phenol resin, it can be cured by heating, but it can also be cured at a low temperature by adding various organic or inorganic strong acids. In this case, toluenesulfonic acid or phenolsulfonic acid is particularly preferably used.

When silicon alkoxide and / or silica sol is used in the above production method, phenol resin / silica composite spherical fine particles having a silica layer formed on the surface are obtained. Still, when alkyl group or phenyl group-substituted silicon alkoxide is used, phenolic resin / silica composite spherical fine particles in which a silica layer containing a resin (high silica-containing layer) is formed near the surface or silica continuously from the surface to the inside And spherically distributed phenolic resin / silica composite spherical particles are obtained. The size of the spherical fine particles can be controlled by the contents of the silicon compound and the emulsion stabilizer. That is, the larger the content of silicon compound and emulsion stabilizer, the smaller the spherical fine particles.
When silica sol or silica nanoparticle is used, the suspension obtained by the above production method can be appropriately diluted with water as it is and used as a polishing liquid.

  Next, the formation mechanism of the phenol / silica composite spherical fine particles of the present invention will be described. That is, when an aqueous phase containing a poor solvent water of a phenol resin is dropped into an organic phase composed of a phenol resin, silicon alkoxide, and an organic solvent, the phenol resin gradually phase-inverts and precipitates as fine particles. In parallel with this, silicon alkoxide contained in the organic phase undergoes hydrolysis and polycondensation to produce silica. Hydrophilic silica gradually moves to the surface of the phenol resin (interface with water) and aggregates. As a result, phenol resin / silica composite spherical fine particles having a silica layer formed on the surface are obtained. On the other hand, when an alkyl group-substituted silicon alkoxide is used, the generated silica contains an alkyl group, so that the hydrophobicity is increased and the surface of the phenol resin is less likely to aggregate. As a result, a phenol resin / silica composite spherical fine particle in which a silica layer containing a resin (high silica-containing layer) is formed in the vicinity of the surface or a phenol resin / silica composite in which silica is continuously distributed from the surface to the inside Spherical fine particles are obtained.

  The phenolic resin / silica composite spherical fine particles obtained by the present invention usually have a diameter of 0.1 to 100 μm, a silica content of 0.5 to 30% by mass, and the silica layer or the silica-containing layer. The thickness is in the range of 5 nm to 1000 nm, and the size of silica contained in the particles is in the range of 5 nm to 1000 nm.

  Moreover, since the surface hardness of the phenol resin / silica composite spherical fine particles obtained in the present invention can be easily controlled by changing the silica content and the fine structure of the silica layer, they are suitably used as abrasive grains. For example, when a suspension obtained by dispersing composite spherical fine particles in an aqueous solution containing a surfactant or an emulsion stabilizer is used as a CMP (mechanochemical polishing) polishing liquid, compared to conventional colloidal silica polishing liquid Thus, the abrasive part is less likely to be deformed by polishing and has the advantage of suppressing the occurrence of scratches.

  Hereinafter, the present invention will be described in more detail with reference to examples. In the following examples, S-430 manufactured by Hitachi, Ltd. was used for observation by a scanning electron microscope (SEM), and JEM-200CX manufactured by JEOL Ltd. was used for observation by a transmission electron microscope (TEM).

(Example 1)
Phenolite J325 (manufactured by Dainippon Ink & Chemicals, Inc., resol type phenolic resin, methanol solvent, solid content 60%) 33.3 g, low condensate MS-51 of 30 g of methanol and tetramethoxysilane (manufactured by Mitsubishi Kasei Corporation, A solution consisting of 4.75 g of a molecular weight of about 500) was dropped and mixed to obtain an organic phase. On the other hand, 0.12 g of humanoxyethyl cellulose HEC Daicel SP800 (manufactured by Daicel Chemical Industries, Ltd.) was added to 20 g of distilled water, and dissolved by stirring to obtain an aqueous phase. Next, the aqueous phase was slowly dropped with a simple pipette while stirring the organic phase. When about 13 g of the aqueous phase was dropped, the solution became turbid and gradually became opaque. This was due to the phase inversion emulsification of the organic phase phenol resin and the like. The light transmittance of the solution was about 11% before phase inversion emulsification, but decreased to 0.2% after phase inversion emulsification. When the addition of the aqueous phase was completed, 20 g of distilled water was further added dropwise to obtain a homogeneous suspension.
Subsequently, while stirring 500 g distilled water, the above suspension was poured into water to precipitate a fine powder. The supernatant solution was removed by centrifugation, and the resulting fine powder was further washed twice with water. This fine powder was dispersed in water, heated and cured at 100 ° C. for 24 hours, and then centrifuged and vacuum dried to obtain 14.1 g of phenol resin / silica composite fine particles at a yield of 57% based on the raw material. When the obtained composite fine particles were baked at 1000 ° C. for 2 hours in an air atmosphere, the white ash content (SiO 2) was 13.6% by mass.
The composite fine particle sample was surface-coated to a thickness of 5 nm using platinum on a scanning electron microscope sample stage, and morphology observation was performed using a scanning electron microscope. As a result, it was found that the fine particles were spherical particles having an average particle diameter of 2 μm. A transmission electron micrograph of the obtained spherical fine particles embedded in an embedding resin and observed as an ultrathin section with a microdome shows that a silica layer with a thickness of about 50 nm is formed on the surface of the spherical fine particles. It was.

The abbreviations listed in Table 1 mean the following.
Phenolic resin
J325: Resol type phenol resin Phenolite J325 (Dainippon Ink Chemical Co., Ltd.)
Silicon compounds
MS-51: Tetramethoxysilane low condensate MKC silicate (Mitsubishi Chemical Corporation)
TMOS: Tetramethoxysilane (Tokyo Chemical Industry Co., Ltd.)
MeTMOS: Methyltrimethoxysilane LS-530 (Shin-Etsu Chemical Co., Ltd.)
PhTMOS: Phenyltrimethoxysilane (Tokyo Chemical Industry Co., Ltd., reagent grade)
GTMOS: 3-glycidoxypropyltrimethoxysilane LS-2940 (manufactured by Shin-Etsu Chemical Co., Ltd.)
Methanol silica sol: Silica sol (manufactured by Nissan Chemical Industries, Ltd., solid content 30%, particle size 10-20 nm, methanol solvent)
MA-ST-M: Silica sol (manufactured by Nissan Chemical Industries, solid content 40%, particle size 20-30nm, methanol solvent)
Emulsion stabilizer
HEC: Humanoxyethyl cellulose, HEC Daicel SP-800 (manufactured by Daicel Chemical Industries, Ltd.)
(4) Surfactant
HTAC: n-hexadecyltrimethylammonium chloride (manufactured by Kanto Chemical Co., Ltd., deer grade 1)
DSNa: Sodium n-dodecyl sulfate (manufactured by Wako Pure Chemical Industries, Ltd., reagent grade 1)

(Examples 2 to 4)
Example 2 uses 0.06 g of SP800, Example 3 uses 0.03 g of SP800, Example 4 uses 0.015 g of SP800, and otherwise the phenol resin / silica composite spherical shape is the same as in Example 1. Fine particles were prepared. As shown in Table 1, the spherical fine particles were enlarged by reducing the amount of hydroxyethyl cellulose charged.

(Examples 5 to 7)
In Example 5, composite spherical fine particles were prepared in the same manner as in Example 1 except that 2.46 g of MS-51 was used. As shown in Table 1, the spherical fine particles were enlarged by reducing the amount of silicon compound charged.
The composite spherical fine particles were prepared in the same manner as in Example 5 except that 0.06 g of SP800 was used for Example 6, 0.03 g of SP800 was used for Example 7, and other than that. The results are shown in Table 1.

(Examples 8 to 10)
For Example 8, 1.2 g of MS-51 was used, for Example 9, 0.58 g of MS-51 was used, for Example 10, 1.2 g of MS-51 and 0.2 g of HTAC were used, and otherwise, Example 1 was used. Similarly, composite spherical fine particles were prepared.
In addition, in the transmission electron micrograph of the spherical fine particles obtained in Example 8 embedded in an embedding resin and observed as an ultrathin section with a microdome, a silica layer having a thickness of about 10 nm is formed on the surface of the spherical fine particles. Showed that.

(Examples 11 to 17)
In Examples 11-17, various fine silicon compounds were used instead of MS-51 alone or in combination with MS-51, and composite fine particles were prepared in substantially the same manner as in Example 1 with the amounts shown in Table 1. It was adjusted. The obtained fine particles are all spherical fine particles, and the particle size and yield are shown in Table 1.
Further, the spherical fine particles obtained in Examples 8 and 15 were embedded in an embedding resin, an ultrathin section was prepared with a microdome, and the spherical fine particle cross section was exposed. Next, using a transmission electron microscope, an electron beam beam having a diameter of 500 nm was applied to the outer surface and the inside of the obtained spherical fine particle cross section, and elemental analysis of Si was performed. The results are shown in Table 2.

  As shown in Table 2, in Example 8 using the silicon alkoxide low condensate MS-51, silica aggregated on the surface of the spherical fine particles, and there was almost no silica inside the sphere. In contrast, in Example 15 using a part of the relatively hydrophobic methyl group-substituted silicon alkoxide MeTMOS, a considerable amount of silica remained not only on the surface of the obtained spherical fine particles but also inside the sphere.

SEM photograph (magnification: 1000) of spherical fine particles of phenol resin / silica composite obtained in Example 3 TEM photograph (magnification: 100,000) of the phenol resin / silica composite spherical fine particles obtained in Example 8

Claims (13)

Fine particles obtained by adding an aqueous solution containing an emulsion stabilizer (D) to an organic phase containing a phenol resin (A), a silicon compound (B), and an organic solvent (C) and phase-inverting the organic layer. A method for producing spherical fine particles of a phenol resin / silica composite, characterized by being heat-cured. The method for producing spherical fine particles of a phenol resin / silica composite according to claim 1, wherein the silicon compound (B) is a silicon alkoxide, an alkyl group or a phenyl group-substituted silicon alkoxide, a low condensate thereof, or a silica sol. The silicon alkoxides, alkyl group or phenyl group-substituted silicon alkoxides contained in the silicon compound (B), or a low condensate thereof are subjected to hydrolysis and polycondensation reaction during phase inversion emulsification. 2. The method for producing a spherical fine particle of phenol resin / silica composite according to 2. The said phenol resin (A) is a resol type phenol resin, The manufacturing method of the phenol resin / silica composite spherical fine particle in any one of Claims 1-3 characterized by the above-mentioned. The said organic solvent (C) is a thing containing a lower alcohol, The manufacturing method of the phenol resin / silica composite spherical fine particle in any one of Claims 1-4 characterized by the above-mentioned. The method for producing spherical fine particles of a phenol resin / silica composite according to any one of claims 1 to 5, wherein the emulsion stabilizer (D) is hydroxyethyl cellulose. The method for producing spherical fine particles of a phenol resin / silica composite according to any one of claims 1 to 6, wherein the diameter is 0.1 to 100 µm. Silica content rate is 0.5-30 mass%, The manufacturing method of the phenol resin / silica composite spherical fine particle in any one of Claims 1-7. The method for producing a phenol resin / silica composite spherical fine particle according to any one of claims 1 to 8, wherein the particle surface has a silica layer or a silica-containing layer. The method for producing phenol resin / silica composite spherical fine particles according to claim 9, wherein the thickness of the silica layer or the silica-containing layer is in the range of 5 nm to 1000 nm. The manufacturing method of the phenol resin / silica composite spherical fine particles according to any one of claims 1 to 10, wherein the particles contain silica. 12. The method for producing phenol resin / silica composite spherical fine particles according to claim 11, wherein the silica in the silica layer or the silica-containing layer and the silica in the particles are continuous. The method for producing spherical fine particles of a phenol resin / silica composite according to claim 11 or 12, wherein the silica contained in the particles has a size in the range of 5 nm to 1000 nm.

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