JP6052094B2 - Method for producing polytetrafluoroethylene powder composition and method for producing resin composition containing the same - Google Patents

Description

  The present invention relates to a polytetrafluoroethylene powder composition, and more particularly, to an improved polytetrafluoroethylene powder composition in which a high degree of fluidity is imparted to polytetrafluoroethylene powder, which is used as a resin to prevent drip. It is related with the polytetrafluoroethylene powder composition which can improve a flame retardance and a drip prevention effect with a small quantity by mix | blending with a composition.

  Conventionally, in thermoplastic resin molded products used in homes, offices, factories, etc., for example, electrical appliances and OA equipment, most of the thermoplastic resins are flammable. There is a need for a device that can be added to improve the flame retardancy of a resin molded product.

  However, many flame retardants have the effect of making the resin difficult to burn, but once the combustion starts, the thermoplastic resin becomes liquid and drip (dripping) while burning, so the effect of preventing the spread of fire is poor. On the other hand, for example, in the standard of Underwriters' Laboratories (hereinafter abbreviated as UL) 94, as a grade of a fire test (Fire Test), a class (V-1, V, which has a high flame retardancy on the condition of anti-drip property) -0). Further, in order to prevent drip and further increase safety, polytetrafluoroethylene (PTFE) powder or an aqueous dispersion is melt-mixed with a flame retardant thermoplastic resin together with a flame retardant.

  Polytetrafluoroethylene is widely used as a coating agent because it is excellent in heat resistance, chemical resistance, and electrical insulation, and has unique surface properties such as water and oil repellency, non-adhesiveness, and self-lubricating properties. Also, since it has high crystallinity and low intermolecular force, it has the property of forming fibers with a slight stress. When blended with a thermoplastic resin, molding processability, mechanical properties, etc. are improved. It is also used as an additive.

  For example, Patent Document 1 includes a composition obtained by adding 0.1 to 5% (mass%, the same applies hereinafter) of polytetrafluoroethylene together with a flammable thermoplastic resin, a flame retardant, and non-flammable fibers. Is a composition in which a flame retardant and polytetrafluoroethylene are added to polyphenylene ether or styrene resin, and Patent Document 3 discloses a flame retardant of an organic alkali metal salt and / or an organic alkaline earth metal salt to an aromatic polycarbonate. A composition obtained by adding 0.01 to 2.0% of PTFE of 01 to 10% and ASTM D-1457 type 3 is disclosed in Patent Document 4 as an acrylonitrile-butadiene-styrene copolymer (ABS) with a flame retardant and polytetrafluoro. Compositions with added ethylene are disclosed.

  In addition, regarding a polymer alloy of an aromatic polycarbonate and a styrene resin, Patent Document 5 includes a composition in which an organic bromine compound and a flame retardant such as antimony or bismuth compound and PTFE are added, and Patent Documents 6 to 9 include A composition in which polytetrafluoroethylene is added together with a phosphorus compound, and Patent Document 10 discloses a composition in which polytetrafluoroethylene is added together with an alkali metal salt of an organic or inorganic acid. Regarding polyamide, for example, Patent Document 11 discloses a composition in which polytetrafluoroethylene is added together with a flame retardant such as a phosphate ester. Patent Documents 12 and 13 disclose resin compositions obtained by blending polytetrafluoroethylene with polyolefin. Patent Document 14 discloses a method for producing a polyolefin-based resin composition in which polytetrafluoroethylene and dispersion medium powder are mixed under high shear to fiberize polytetrafluoroethylene in advance and then mixed with polyolefin.

  Polytetrafluoroethylene for drip prevention is polytetraethylene powder obtained by coagulating and drying latex obtained by emulsion polymerization of tetrafluoroethylene (TFE) (usually called PTFE fine powder, standard specific gravity (SSG) In the range of 2.14 to 2.23 and classified as ASTM D-1457 type 3), or an aqueous dispersion (usually PTFE disperse) produced by adding a surfactant to the latex and concentrating and stabilizing it. Called John).

  The function of preventing drip is due to the fact that the polytetrafluoroethylene powder has the property of easily fibrillating. That is, when the thermoplastic resin is mixed with the polytetraethylene powder or the dispersion in a molten state, the polytetrafluoroethylene fine particles are fibrillated by the shearing force of the mixing, and the fibrils are dispersed in the thermoplastic resin. Drip at the time of combustion is prevented by leaving the fibrils dispersed in the final molded product of the thermoplastic resin.

  However, to mix the flammable thermoplastic resin and polytetrafluoroethylene, prior to melt mixing, the flammable thermoplastic resin powder, pellets or liquid, and the polytetrafluoroethylene powder or dispersion Need to be mixed. However, since the polytetraethylene powder is easily fibrillated even at room temperature, the agglomerates between the polytetraethylene powders are easily generated, and the handleability of the powder is inferior, which causes a serious problem in workability when mixing.

  As an anti-drip agent, a material having excellent powder handling properties is required. Furthermore, when adding to the raw material resin, it is necessary to premix the polytetrafluoroethylene powder and the raw material resin in advance. At this time, the mixed powder of the raw material resin and the polytetrafluoroethylene powder is mixed in the mixer or the extruder feeder. There was a problem of causing aggregation and blocking to significantly impair workability and productivity.

Therefore, attempts have been made to improve the flame retardancy of the thermoplastic resin composition by adding a mixture of polytetrafluoroethylene powder and organic polymer particles (PTFE-containing mixed powder) (Patent Documents 15 and 16). , Patent Document 17 etc.). That is, Patent Document 15 describes that flame retardancy is improved by adding a powder obtained by mixing and solidifying a polytetrafluoroethylene dispersion and an aromatic vinyl polymer dispersion. Has been. Patent Document 16 describes that a powder obtained by polymerizing an organic monomer in the presence of a polytetrafluoroethylene dispersion is excellent in handleability. Patent Document 17 describes that a thermoplastic resin composition comprising a polycarbonate, an acrylonitrile-styrene-butadiene copolymer and a polyorganosiloxane-containing composite rubber-based graft copolymer is excellent in flame retardancy and impact resistance. ing.
However, when the polytetrafluoroethylene-containing mixed powder as an anti-drip agent is added to the thermoplastic resin, it contributes to the anti-drip performance as compared with the case where the anti-drip agent of polytetrafluoroethylene alone is added in the same addition amount. Since the addition amount of polytetrafluoroethylene is small, it is difficult to obtain a sufficient anti-drip effect, and there is a problem that the addition amount of the anti-drip agent is increased to obtain a sufficient effect and the cost is increased.

  In addition, there is a polytetrafluoroethylene molding powder obtained by suspension polymerization of TFE (standard specific gravity is in the range of 2.13 to 2.23, classified as ASTM D-1457 type 4, 6, 7), It has also been proposed to use this as an additive for flammable thermoplastic resins (see, for example, Patent Document 18).

  Further, in Patent Document 19, when producing polytetrafluoroethylene powder from polytetrafluoroethylene latex, a powder flow that coagulates after a large amount of fluorosurfactant coexists in the polytetrafluoroethylene latex in advance. A method for producing polytetrafluoroethylene powder having a high apparent density of 0.52 g / ml or more, which is excellent in properties, has been proposed.

JP-A-50-44241 Japanese Patent Publication No.59-36657 Japanese Patent Publication No. 60-38418 Japanese Examined Patent Publication No. 62-58629 Japanese Patent Publication No. 1-60181 JP-A-61-55145 JP 61-261352 A Japanese Unexamined Patent Publication No. 63-278961 JP-A-2-32154 JP-A 61-127759 JP-A-5-186686 JP-A-5-214184 JP-A-6-306212 Japanese Patent Laid-Open No. 7-324147 JP 60-258263 A Japanese Patent Laid-Open No. 9-95583 Japanese Patent Laid-Open No. 10-310707 Japanese Patent Laid-Open No. 10-77378 International Publication No. 97/17382

  However, the conventional anti-drip agent using polytetrafluoroethylene powder still has a problem that it easily aggregates, and it cannot be said that the handleability is sufficient. In addition, since the dispersibility in the resin is not good, there is a case where an amount is required to exhibit a drip prevention effect.

  Accordingly, an object of the present invention is to provide a polytetrafluoroethylene powder composition having excellent handleability and good fluidity and dispersibility. Another object of the present invention is to provide a resin composition containing the polytetrafluoroethylene powder composition as an anti-drip agent.

  As a result of intensive studies in view of such circumstances, the present inventors have found that the following polytetrafluoroethylene powder composition solves the above-mentioned problems, and have completed the present invention. That is, the present invention is as follows.

<1> A powder in which silica fine particles in an amount of at least 0.01% by mass of the mass of the polytetrafluoroethylene powder are attached to the surface of the polytetrafluoroethylene powder,
The silica fine particles are
(A1) a step of obtaining hydrophilic spherical silica fine particles substantially consisting of SiO ₂ units by hydrolyzing and condensing a tetrafunctional silane compound, a partially hydrolyzed condensation product thereof, or a mixture thereof;
(A2) R ¹ SiO _3/2 unit (wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms) is introduced onto the surface of the hydrophilic spherical silica fine particles. Process,
(A3) introducing a R ² ₃ SiO _1/2 unit (wherein each R ² is the same or different and is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms). Manufactured by the method,
Hydrophobic spherical silica fine particles (1) having a particle size in the range of 0.005 to 1.00 μm, a particle size distribution D90 / D10 value of 3 or less, and an average circularity of 0.8 to 1. A polytetrafluoroethylene powder composition characterized by the above.

<2> The hydrophobic spherical silica fine particles (1)
(A1) General formula (I):
Si (OR ³ ) ₄ (I)
(In the formula, each R ³ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms)
By substantially hydrolyzing and condensing a tetrafunctional silane compound represented by the formula, a partial hydrolysis product thereof, or a mixture thereof in a mixture of a hydrophilic organic solvent and water in the presence of a basic substance, SiO 2 Obtain a mixed solvent dispersion of hydrophilic spherical silica fine particles consisting of ₂ units,
(A2) In the mixed solvent dispersion of the obtained hydrophilic spherical silica fine particles, the general formula (II):
R ¹ Si (OR ⁴ ) ₃ (II)
(Wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and each R ⁴ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms)
The surface of the hydrophilic spherical silica fine particles is treated with R ¹ SiO ₃ by adding a trifunctional silane compound represented by the formula, a partial hydrolysis product thereof or a mixture thereof to treat the surface of the hydrophilic spherical silica fine particles. _{/ 2} unit (R ¹ is as described above) to obtain a mixed solvent dispersion of the first hydrophobic spherical silica fine particles,
(A3) In the mixed solvent dispersion of the obtained first hydrophobic spherical silica fine particles, the general formula (III):
R ² ₃ SiNHSiR ² ₃ (III)
(In the formula, each R ² is the same or different substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms)
A silazane compound represented by the general formula (IV):
R ² ₃ SiX (IV)
(Wherein R ² is as defined in formula (III), X is an OH group or a hydrolyzable group), or a mixture thereof, The surface of the first hydrophobic spherical silica fine particles is thus treated, and R ² ₃ SiO _1/2 units (R ² is defined by the general formula (III) are formed on the surface of the first hydrophobic spherical silica fine particles. The polytetrafluoroethylene powder composition according to <1>, which is a hydrophobic spherical silica fine particle obtained as a second hydrophobic silica fine particle by introducing

  <3> The polytetrafluoroethylene powder is prepared by adding the hydrophobic spherical silica fine particles (1) to the polytetrafluoroethylene powder at 0.01 to 5.0% by mass of the polytetrafluoroethylene powder and mixing them. The polytetrafluoroethylene powder composition according to <1> or <2>, wherein the hydrophobic spherical silica fine particles (1) are attached to the surface.

  <4> An anti-drip agent for a thermoplastic resin comprising the polytetrafluoroethylene powder composition according to any one of <1> to <3>.

  <5> A resin composition containing the polytetrafluoroethylene powder composition according to any one of <1> to <3> in a thermoplastic resin.

  <6> Thermoplastic resin is polycarbonate, acrylonitrile-styrene resin, acrylonitrile-butadiene-styrene resin, (polycarbonate) / (acrylonitrile-butadiene-styrene) alloy resin, polybutylene terephthalate, polyethylene terephthalate, polyphenylene ether, polypropylene And the resin composition according to <5>, which is at least one resin selected from the group consisting of polystyrene.

<7> The resin composition according to <6>, wherein the thermoplastic resin is polycarbonate.

<8> The resin composition according to any one of <5> to <7>, further containing a flame retardant.

  Since the polytetrafluoroethylene powder composition of the present invention has good fluidity and stability, it is easy to handle, and when mixed with a resin, it uniformly disperses, so that it is suitable for resin in a small amount. An effect can be imparted.

The electron micrograph of the polytetrafluoroethylene powder composition of Example 2 in which spherical hydrophobic silica fine particles are adhered to the surface of the polytetrafluoroethylene powder is shown. The electron micrograph of the polytetrafluoroethylene powder composition of Example 4 in which spherical hydrophobic silica fine particles are adhered to the surface of the polytetrafluoroethylene powder is shown. The electron micrograph of the untreated polytetrafluoroethylene powder which does not add the spherical hydrophobic silica fine particles of Comparative Example 5 to the polytetrafluoroethylene powder is shown.

Hereinafter, the present invention will be described in detail.
<Polytetrafluoroethylene powder component>
Among the known powders, the polytetrafluoroethylene powder used in the present invention has an average particle size of 1-1000 μm, preferably 10-800 μm, and an apparent density of 0.20-1.00 g / cm ³ , preferably 0.25. ~0.95g / cm ^3, a standard specific gravity (SSG) is from 2.13 to 2.23, preferably is suitably used those from 2.14 to 2.20.

  Such polytetrafluoroethylene powder may include not only tetrafluoroethylene single suspension polymer powder but also various modified polytetrafluoroethylene powders. Examples of such modified polytetrafluoroethylene powder include modified monomers such as those described in JP-B-40-10428, JP-B-50-31524, JP-B-54-46794 or WO95 / 16126. 0.001 to 1.0% by weight is included. As the modified monomer, for example, fluoroolefins such as chlorotrifluoroethylene, hexafluoropropylene, fluoroalkylethylene, and perfluoro (alkyl vinyl ether) are preferable. In addition, PTFE molding powder (see Japanese Patent Publication No. 5-80490) obtained by a suspension polymerization system to which a small amount of a dispersant is added is also included. Further, granulated polytetrafluoroethylene powder obtained by pulverizing and granulating the particles obtained by suspension polymerization (Japanese Examined Patent Publication No. 44-22619, Japanese Examined Publication No. 58-14291, Japanese Examined Patent Publication No. 3-69927, Japanese Patent Examined Publication) 3-39105 gazette) can also be used.

The polytetrafluoroethylene (PTFE) used in the present invention preferably has a standard specific gravity (SSG) (ASTM D-1457) of 2.13 to 2.23, particularly 2.14 to 2.20. The smaller the standard specific gravity, the higher the molecular weight. When it exceeds 2.23 (the molecular weight is small), fibrillation tends to be insufficient. No matter how small the standard specific gravity is (no matter how large the molecular weight), the lower limit of the standard specific gravity depends on whether it is easy to manufacture. The number average molecular weight of PTFE having a standard specific gravity of 2.14 to 2.20 is about 15 × 10 ^{5 to} 9 × 10 ⁶ when calculated by the following formula.

Formula: log ₁₀ (number average molecular weight) = 31.83-11.58 × (standard specific gravity)

<Hydrophobic spherical silica fine particles>
The hydrophobic spherical silica fine particles attached to the surface of the polytetrafluoroethylene powder will be described in detail.
The hydrophobic spherical silica fine particles used in the present invention are
(A1) a step of obtaining hydrophilic spherical silica fine particles substantially consisting of SiO ₂ units by hydrolyzing and condensing a tetrafunctional silane compound, a partially hydrolyzed condensation product thereof, or a mixture thereof;
(A2) R ¹ SiO _3/2 unit (wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms) is introduced onto the surface of the hydrophilic spherical silica fine particles. Process,
(A3) introducing a R ² ₃ SiO _1/2 unit (wherein each R ² is the same or different and is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms). Manufactured by the method,
Hydrophobic spherical silica fine particles (1) having a particle size in the range of 0.005 to 1.00 μm, a particle size distribution D90 / D10 of 3 or less and an average circularity of 0.8 to 1.

  The hydrophobic spherical silica fine particles have a particle size of 0.005 to 1.00 μm, preferably 0.01 to 0.30 μm, and particularly preferably 0.03 to 0.20 μm. When the particle diameter is smaller than 0.005 μm, the polytetrafluoroethylene powder is agglomerated so that the polytetrafluoroethylene powder may not be taken out well. Moreover, when larger than 1.00 micrometer, favorable fluidity | liquidity and a filling property may not be provided to polytetrafluoroethylene powder, and it is unpreferable.

The value of D90 / D10, which is an index of the particle size distribution of the hydrophobic spherical silica fine particles, is 3 or less. Here, D10 and D90 are values obtained by measuring the particle size distribution. When the particle size distribution of the powder is measured, the particle size that accumulates 10% from the small side is referred to as D10, and the particle size that accumulates from 90% from the small side is referred to as D90. Since D90 / D10 is 3 or less, the particle size distribution of the hydrophobic spherical silica fine particles in the present invention is sharp. Thus, it is preferable that the particles have a sharp particle size distribution in that it is easy to control the fluidity of the polytetrafluoroethylene powder. The D90 / D10 is more preferably 2.9 or less.
In the present invention, the particle size distribution of the fine particles is measured by a dynamic light scattering method / laser Doppler nanotrack particle size distribution measuring apparatus (trade name: UPA-EX150, manufactured by Nikkiso Co., Ltd.), and the volume-based median diameter is determined. The particle diameter was taken. The median diameter is a particle diameter corresponding to 50% cumulative when the particle size distribution is expressed as a cumulative distribution.

  The average circularity of the hydrophobic spherical silica fine particles is preferably from 0.8 to 1, more preferably from 0.92 to 1. Here, “spherical” includes not only a true sphere but also a slightly distorted sphere. Such a “spherical” shape is evaluated by the circularity when the particles are projected two-dimensionally, and the circularity is in the range of 0.8 to 1. Here, the circularity is (peripheral length of a circle equal to the particle area) / (peripheral length of particle). This circularity can be measured by image analysis of a particle image obtained with an electron microscope or the like. The average circularity can be obtained by observing with an electron microscope, measuring 100 primary particles, and averaging them.

In the present invention, the hydrophilic spherical silica fine particle “consists essentially of SiO ₂ units” means that the fine particles are basically composed of SiO ₂ units, but are not composed solely of the units. , Which means that it has a large number of silanol groups at least on the surface as is generally known. In some cases, some of the hydrolyzable groups (hydrocarbyloxy groups) derived from the tetrafunctional silane compound and / or its partial hydrolysis-condensation product, which are raw materials, are not converted into silanol groups in a slight amount. It means that it may remain on the surface or inside.

  As described above, in the present invention, a small particle size sol-gel method silica obtained by hydrolysis of tetraalkoxysilane or the like is used as a silica base (silica before hydrophobization treatment), and a specific surface treatment is applied thereto. When obtained as a powder, the particle size after hydrophobization treatment maintains the primary particle size of the silica base, is not agglomerated, has a small particle size, and has good flow to polytetrafluoroethylene powder. Hydrophobic silica fine particles capable of imparting properties are obtained.

  The silica particle having a small particle size uses tetraalkoxysilane having a small number of carbon atoms in the alkoxy group, uses alcohol having a small number of carbon atoms as a solvent, raises the hydrolysis temperature, and hydrolyzes the tetraalkoxysilane. It can be obtained by changing the reaction conditions such as lowering the concentration of the catalyst and lowering the concentration of the hydrolysis catalyst.

  As described above and as will be described in more detail below, the silica particle having a small particle diameter is subjected to a specific surface treatment to obtain desired hydrophobic silica fine particles.

  Next, one method for producing the hydrophobic spherical silica fine particles will be described in detail below.

<Method for producing hydrophobic spherical silica fine particles (1)>
The hydrophobic spherical silica fine particles of the present invention are
Step (A1): Step of synthesizing hydrophilic spherical silica fine particles,
Step (A2): surface treatment step with a trifunctional silane compound,
Step (A3): Obtained by a surface treatment step with a functional silane compound, but each step will be described in more detail below.

Step (A1): Synthesis step of hydrophilic spherical silica fine particles General formula (I):
Si (OR ³ ) ₄ (I)
(In the formula, each R ³ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms)
Hydrophilic spherical silica is obtained by hydrolyzing and condensing a tetrafunctional silane compound represented by the formula, a partial hydrolysis product thereof, or a mixture thereof in a mixture of a hydrophilic organic solvent containing a basic substance and water. A mixed solvent dispersion of fine particles is obtained.

In the above general formula (I), R ³ is a monovalent hydrocarbon group having 1 to 6 carbon atoms, preferably a monovalent hydrocarbon group having 1 to 4 carbon atoms, particularly preferably 1 to 2 carbon atoms. is there. Examples of the monovalent hydrocarbon group represented by R ³ include an alkyl group such as a methyl group, an ethyl group, a propyl group, and a butyl group; and an aryl group such as a phenyl group, preferably a methyl group, An ethyl group, a propyl group, or a butyl group, particularly preferably a methyl group or an ethyl group.

  Examples of the tetrafunctional silane compound represented by the general formula (I) include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane; and tetraphenoxysilane, preferably , Tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane and tetrabutoxysilane, particularly preferably tetramethoxysilane and tetraethoxysilane. Examples of the partial hydrolysis-condensation product of the tetrafunctional silane compound represented by the general formula (I) include alkyl silicates such as methyl silicate and ethyl silicate.

The hydrophilic organic solvent is not particularly limited as long as it dissolves the tetrafunctional silane compound represented by the general formula (I), the partial hydrolysis-condensation product, and water. For example, alcohols ; Cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, cellosolve acetate; ketones such as acetone and methyl ethyl ketone; ethers such as dioxane and tetrahydrofuran, etc., preferably alcohols and cellosolves, particularly preferably Examples include alcohols. Examples of the alcohols include general formula (V):
R ⁵ OH (V)
[Wherein, R ⁵ is a monovalent hydrocarbon group having 1 to 6 carbon atoms].

In the general formula (V), R ⁵ is preferably a monovalent hydrocarbon group having 1 to 4 carbon atoms, particularly preferably 1 to 2 carbon atoms. Examples of the monovalent hydrocarbon group represented by R ⁵ include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group, preferably a methyl group, an ethyl group, a propyl group, and an isopropyl group. Preferably a methyl group and an ethyl group are mentioned. Examples of the alcohol represented by the general formula (V) include methanol, ethanol, propanol, isopropanol, butanol and the like, preferably methanol and ethanol. As the number of carbon atoms in the alcohol increases, the particle size of the spherical silica fine particles to be generated increases. Therefore, methanol is preferred in order to obtain the desired small particle size silica fine particles.

Examples of the basic substance include ammonia, dimethylamine, diethylamine and the like, preferably ammonia, diethylamine, and particularly preferably ammonia. These basic substances may be dissolved in water in a required amount, and the obtained aqueous solution (basic) may be mixed with the hydrophilic organic solvent.
The basic substance is used in an amount of 0.01 to 2 mol with respect to a total of 1 mol of the hydrocarbyloxy group of the tetrafunctional silane compound represented by the general formula (I) and / or its partial hydrolysis-condensation product. It is preferable that it is 0.02-0.5 mol, and it is especially preferable that it is 0.04-0.12 mol. At this time, the smaller the amount of the basic substance, the smaller the silica particle having a smaller particle diameter.

  The amount of water used in the hydrolysis and condensation is 0. 1 mol for the total of 1 mol of hydrocarbyloxy groups of the tetrafunctional silane compound represented by the general formula (I) and / or the partial hydrolysis condensation product thereof. It is preferably 5 to 5 mol, more preferably 0.6 to 2 mol, and particularly preferably 0.7 to 1 mol. The ratio of the hydrophilic organic solvent to water (hydrophilic organic solvent: water) is preferably 0.5 to 10 in terms of mass ratio, more preferably 3 to 9, and more preferably 5 to 8. Particularly preferred. As the amount of the hydrophilic organic solvent increases, silica particles having a smaller particle diameter can be obtained.

  Hydrolysis and condensation of the tetrafunctional silane compound represented by the general formula (I) can be carried out by a well-known method, that is, in a mixture of a hydrophilic organic solvent containing a basic substance and water in the general formula (I). It is performed by adding a tetrafunctional silane compound or the like shown.

  The concentration of silica fine particles in the mixed solvent dispersion of hydrophilic spherical silica fine particles obtained in this step (A1) is generally 3 to 15% by mass, preferably 5 to 10% by mass.

Step (A2): Surface treatment step with trifunctional silane compound In the mixed solvent dispersion of the hydrophilic spherical silica fine particles obtained in the step (A1), the general formula (II):
R ¹ Si (OR ⁴ ) ₃ (II)
Wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and each R ⁴ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms. To the surface of the hydrophilic spherical silica fine particles by adding a trifunctional silane compound or a partial hydrolysis product thereof, or a mixture thereof and treating the surface of the hydrophilic spherical silica fine particles thereby. ¹ SiO _3/2 unit (R ¹ is as described above) is introduced to obtain a mixed solvent dispersion of the first hydrophobic spherical silica fine particles.

  This step (A2) is indispensable for suppressing aggregation of silica fine particles in the subsequent concentration step. If the aggregation cannot be suppressed, the individual particles of the obtained silica-based powder cannot maintain the primary particle diameter, and the fluidity imparting ability is deteriorated.

In the general formula (II), R ¹ is preferably a monovalent hydrocarbon group having 1 to 3 carbon atoms, particularly preferably 1 to 2 carbon atoms. Examples of the monovalent hydrocarbon group represented by R ¹ include alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, butyl group and hexyl group, preferably methyl group, ethyl group, n -A propyl group or an isopropyl group, particularly preferably a methyl group or an ethyl group. Further, some or all of the hydrogen atoms of these monovalent hydrocarbon groups may be substituted with halogen atoms such as fluorine atom, chlorine atom, bromine atom, preferably fluorine atom.

In the general formula (II), R ⁴ is preferably a monovalent hydrocarbon group having 1 to 3 carbon atoms, particularly preferably 1 to 2 carbon atoms. Examples of the monovalent hydrocarbon group represented by R ⁴ include alkyl groups such as a methyl group, an ethyl group, a propyl group, and a butyl group, preferably a methyl group, an ethyl group, or a propyl group, and particularly preferably a methyl group. Or an ethyl group is mentioned.

  Examples of the trifunctional silane compound represented by the general formula (II) include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, and n-propyltriethoxy. Unsubstituted or halogen-substituted trisilane such as silane, isopropyltrimethoxysilane, isopropyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, hexyltrimethoxysilane, trifluoropropyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane Alkoxysilane, etc., preferably methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane and ethyltriethoxysilane, more preferably methyltrimethoxysilane Emissions and methyltriethoxysilane, or their partially hydrolyzed condensation products thereof.

  The addition amount of the trifunctional silane compound represented by the general formula (II) is 0.001 to 1 mol, preferably 0.01 to 0.1 mol, per mol of Si atom in the used hydrophilic spherical silica fine particles. Most preferably, it is 0.01-0.05 mol. If the added amount is less than 0.01 mol, the dispersibility of the resulting hydrophobic spherical silica fine particles will deteriorate, so that the effect of imparting fluidity to the polytetrafluoroethylene powder will not appear. Aggregation can occur.

  The concentration of the silica fine particles in the mixed solvent dispersion of the first hydrophobic spherical silica fine particles obtained in this step (A2) is usually 3% by mass or more and less than 15% by mass, preferably 5 to 10% by mass. If the concentration is too low, productivity may be reduced, and if it is too high, aggregation of silica fine particles may occur.

-Concentration step The first hydrophobic spherical silica is obtained by removing a portion of the hydrophilic organic solvent and water from the mixed solvent dispersion of the first hydrophobic spherical silica fine particles thus obtained and concentrating. It is preferable to use a mixed solvent concentrated dispersion of fine particles. At this time, the hydrophobic organic solvent may be added in advance (before the concentration step) or during the concentration step. In this case, the hydrophobic solvent used is preferably a hydrocarbon or ketone solvent. Specific examples of the solvent include toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone and the like, and methyl isobutyl ketone is preferable. Examples of the method for removing a part of the hydrophilic organic solvent and water include distillation and distillation under reduced pressure. The concentrated dispersion obtained preferably has a silica fine particle concentration of 15 to 40% by mass, more preferably 20 to 35% by mass, and particularly preferably 25 to 30% by mass. If the amount is less than 15% by mass, the surface treatment in the subsequent process may not proceed smoothly. If the amount is more than 40% by mass, the silica fine particles may be aggregated.

  In the concentration step, the silazane compound represented by the general formula (III) and the monofunctional silane compound represented by the general formula (IV) used as a surface treatment agent in the next step (A3) react with alcohol or water. In addition, the surface treatment becomes insufficient, and when the subsequent drying is performed, aggregation occurs, and the resulting silica powder cannot maintain the primary particle diameter, and has the significance of suppressing problems such as poor fluidity imparting ability. is there.

Step (A3): In the mixed solvent dispersion of the first hydrophobic spherical silica fine particles obtained in the surface treatment step (A2) with the functional silane compound, the general formula (III):
R ² ₃ SiNHSiR ² ₃ (III)
(In the formula, each R ² is the same or different substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms)
Or a silazane compound represented by formula (IV):
R ² ₃ SiX (IV)
(Wherein R ² is as defined in the general formula (III), X is an OH group or a hydrolyzable group), and a monofunctional silane compound or a mixture thereof is added, whereby By treating the surface of the first hydrophobic spherical silica fine particles and introducing R ² ₃ SiO _1/2 units (wherein R ² is as defined in the general formula (III)) to the surface of the fine particles, Two hydrophobic spherical silica fine particles are obtained. By the treatment in this step, R ² ₃ SiO _1/2 units are introduced to the surface in the form of triorganosilylation of silanol groups remaining on the surface of the first hydrophobic spherical silica fine particles.

In the general formulas (III) and (IV), R ² is preferably a monovalent hydrocarbon group having 1 to 4 carbon atoms, particularly preferably 1 to 2 carbon atoms. The monovalent hydrocarbon group represented by R ² is, for example, an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group or a butyl group, preferably a methyl group, an ethyl group or a propyl group, particularly preferably , Methyl group or ethyl group. In addition, some or all of the hydrogen atoms of these monovalent hydrocarbon groups may be substituted with a halogen atom such as a fluorine atom, a chlorine atom or a bromine atom, preferably a fluorine atom.

  Examples of the hydrolyzable group represented by X include a chlorine atom, an alkoxy group, an amino group, and an acyloxy group, preferably an alkoxy group or an amino group, and particularly preferably an alkoxy group.

  Examples of the silazane compound represented by the general formula (III) include hexamethyldisilazane and hexaethyldisilazane, preferably hexamethyldisilazane. Examples of the monofunctional silane compound represented by the general formula (IV) include monosilanol compounds such as trimethylsilanol and triethylsilanol; monochlorosilanes such as trimethylchlorosilane and triethylchlorosilane; monoalkoxy such as trimethylmethoxysilane and trimethylethoxysilane. Silanes; monoaminosilanes such as trimethylsilyldimethylamine and trimethylsilyldiethylamine; monoacyloxysilanes such as trimethylacetoxysilane; and preferred are trimethylsilanol, trimethylmethoxysilane, and trimethylsilyldiethylamine; Methoxysilane is mentioned.

  The amount of the silazane compound or / and functional silane compound used is 0.1 to 0.5 mol, preferably 0.2 to 0.4 mol, based on 1 mol of Si atoms in the used hydrophilic spherical silica fine particles. Most preferably, it is 0.25-0.35 mol. When the amount used is less than 0.1 mol, the dispersibility of the resulting hydrophobic silica fine particles is deteriorated, so that the effect of imparting fluidity to the polytetrafluoroethylene powder does not appear. When the amount used is more than 0.5 mol, it is economically disadvantageous.

  The hydrophobic spherical silica fine particles can be obtained as a powder by a conventional method such as atmospheric drying or reduced pressure drying.

<Polytetrafluoroethylene powder composition>
The polytetrafluoroethylene powder composition of the present invention is obtained by adding the hydrophobic spherical silica fine particles to the polytetrafluoroethylene powder, and physically adsorbing and adhering to the surface of the polytetrafluoroethylene powder. . The amount of the hydrophobic spherical silica fine particles added to the polytetrafluoroethylene powder is preferably 0.01 to 5.0% by mass of the polytetrafluoroethylene powder, more preferably 0.01 to 4. 0% by mass, in particular 0.01-3.0% by mass. When the amount added is less than 0.01% by mass, the fluidity of the polytetrafluoroethylene powder may not change, which is not preferable. Moreover, when this addition amount exceeds 5.0 mass%, it may not be preferable in terms of cost. The polytetrafluoroethylene powder of the present invention is usually a powder composed of the polytetrafluoroethylene powder and the hydrophobic spherical silica fine particles, but may optionally contain additives such as a colorant and a coupling agent.

  In order to adhere the hydrophobic silica fine particles to the polytetrafluoroethylene powder, a known mixing method may be used. A Henschel mixer, a V-type blender, a ribbon blender, a raking machine, a kneader mixer, a butterfly mixer, What is necessary is just to mix the predetermined amount of each component uniformly using the mixer by a propeller stirring bar. Then, hydrophobic silica fine particles can be easily attached to the surface of the polytetrafluoroethylene powder.

  The fluidity of the polytetrafluoroethylene powder composition was determined by measuring the basic fluidity energy, which is an index of powder fluidity. The basic fluidity energy is measured using a powder fluidity analyzer FT-4 (manufactured by Sysmex Corporation). The measurement principle of this apparatus will be described. A cylindrical container placed vertically is filled with powder, and while rotating two rotating blades (blades) provided at the tip of a vertical shaft rod in the powder, a certain distance (from height H1) Down to H2. The force received from the powder at this time is measured separately for the torque component and the load component, so that each work (energy) associated with the blade descending from H1 to H2 is obtained, and then the total energy of both Find the amount. The smaller the total energy measured in this way, the better the fluidity of the powder, so it can be used as an index of powder fluidity.

It can be judged that the smaller the value of the basic fluidity energy is, the better the fluidity of the powder is. However, if this value is 1000 mJ or less, it can be judged that the fluidity is excellent.
Especially preferably, it is 900 mJ or less, More preferably, it is 800 mJ or less.

  When this value is 1000 mJ or more, the tendency to deteriorate the fluidity is clearly seen, and the transferability of the powder is extremely deteriorated, the workability is deteriorated, and the dispersibility is deteriorated. Adverse effects such as not becoming desirable.

  The polytetrafluoroethylene powder composition of the present invention can be suitably used as an anti-drip agent for thermoplastic resins.

  The resin composition of the present invention contains an anti-drip agent, that is, a polytetrafluoroethylene powder composition in a thermoplastic resin. Since the resin composition of the present invention contains the anti-drip agent, the handleability is excellent.

  The resin composition of the present invention preferably contains 0.01 to 5 parts by mass of the anti-drip agent with respect to 100 parts by mass of the thermoplastic resin, particularly 0.03 to 2 parts by mass, and more preferably 0.05 to 1 part. It is preferable to contain part by mass. If the anti-drip agent is less than 0.01 parts by mass, the desired anti-drip property may not be obtained. Moreover, when it exceeds 5 mass parts, it may be disadvantageous in cost and is not preferable.

  The thermoplastic resin used in the present invention is preferably a flammable thermoplastic resin in terms of an excellent drip prevention effect. Examples of thermoplastic resins include polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers, and polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate, polycyclohexane terephthalate, polybutylene terephthalate (PBT), and polybutylene naphthalate. , Polycarbonate (PC), butadiene rubber graft copolymer (for example, ABS resin), acrylic rubber graft copolymer, silicone-acrylic composite rubber graft copolymer, ethylene propylene rubber graft copolymer, HIPS, AS and other styrene series Resin, vinyl chloride resin, polyacetal resin, polyphenylene sulfide resin, polyphenylene ether resin (PPE), polyamide resin such as nylon 6 and nylon 66 (P ), Acrylic resins such as PMMA, other one of various polymer alloy PET / PBT, PC / PBT, PBT / ABS, PC / ABS, PA / ABS, PPE / PBT, PPE / HIPS, PPE / PA, and the like. Among them, polycarbonate, acrylonitrile-styrene (AS) resin, acrylonitrile-butadiene-styrene (ABS) resin, (polycarbonate) / (acrylonitrile-butadiene-styrene) alloy resin, polybutylene terephthalate, polyethylene terephthalate, polyphenylene ether, polypropylene And at least one resin selected from the group consisting of polystyrene is preferred.

  Resin used for housing and various mechanical parts in applications with high flame retardant requirements such as home appliances and OA equipment, such as PC, PC alloy resin, polystyrene resin, polybutylene terephthalate, polyethylene terephthalate, polyphenylene ether, etc. When the resin is used as an object, the anti-drip agent of the present invention has an excellent anti-drip effect. For example, the thermoplastic resin is at least one resin selected from the group consisting of PC, PC / ABS alloy resin, PC / PBT alloy resin, AS resin, ABS resin, polybutylene terephthalate, polyethylene terephthalate, and polyphenylene ether. Corresponds to this. Among these, polycarbonate is particularly preferable.

  The resin composition of the present invention can further contain a flame retardant. By including a flame retardant, it can be suitably used as a flame retardant resin composition.

  In this invention, it is preferable to contain a flame retardant 0.001-40 mass parts with respect to 100 mass parts of thermoplastic resins, especially 0.01-30 mass parts. When the amount of the flame retardant is less than 0.001 part by mass, the flame retardant effect tends to be insufficient. When the amount of the flame retardant is more than 40 parts by mass, it is not economical and the mechanical properties (such as impact resistance) of the resin composition are low. It tends to decrease.

  Examples of the flame retardant include compounds containing Group 5B of the periodic table such as nitrogen, phosphorus, antimony, and bismuth, and compounds containing Group 7B halogen compounds. Among these, examples of the halogen compound include aliphatic, alicyclic, and aromatic organic halogen compounds such as bromine-based tetrabromobisphenol A (TBA), decabromodiphenyl ether (DBDPE), octabromodiphenyl ether (OBDPE), TBA epoxy / Examples include phenoxy oligomers, brominated cross-linked polystyrene, chlorinated chlorinated paraffins, and perchlorocyclopentadecane. Examples of phosphorus compounds include phosphate esters and polyphosphates. The antimony compound is preferably used in combination with a halogen compound, and examples thereof include antimony trioxide and antimony pentoxide. In addition, aluminum hydroxide, magnesium hydroxide, and molybdenum trioxide can also be used. These flame retardants can be arbitrarily selected in at least one kind and a blending amount according to the kind of the thermoplastic resin, but are not limited thereto.

  The resin composition of the present invention can be produced by blending the above components by a known method. However, the blending order, blending in a powder state or blending in a dispersion state, or the type and combination of blending machines. There are various methods such as, but not limited to. For example, after the flame retardant and the anti-drip agent of the present invention are blended in advance, they are supplied to the kneader together with the resin, or part or all of the thermoplastic resin that is an aqueous dispersion or organosol is added to the anti-drip of the present invention. Various blending methods are possible, such as blending agents.

  Further, known additives such as ultraviolet absorbers, antioxidants, pigments, molding aids, calcium carbonate, glass fibers and the like can be added to the resin composition of the present invention as necessary.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The following examples do not limit the present invention.

[Synthesis of hydrophobic spherical silica fine particles]
<Synthesis Example 1>
Step (A1): Step of synthesizing hydrophilic spherical silica fine particles 989.5 g of methanol, 135.5 g of water and 28% ammonia in a 3 liter glass reactor equipped with a stirrer, a dropping funnel and a thermometer 66.5 g of water was added and mixed. This solution was adjusted to 35 ° C., and 436.5 g (2.87 mol) of tetramethoxysilane was added dropwise over 6 hours while stirring. Even after the completion of the dropwise addition, the suspension was further stirred for 0.5 hours for hydrolysis to obtain a suspension of hydrophilic spherical silica fine particles.

Step (A2): Surface treatment step with trifunctional silane compound 4.4 g (0.03 mol) of methyltrimethoxysilane was added to the suspension obtained in the above step (A1) at room temperature over 0.5 hours. Dropping was continued, and stirring was continued for 12 hours after the dropping, and the dispersion of hydrophobic spherical silica fine particles was obtained by hydrophobizing the surface of the silica fine particles.

  Next, an ester adapter and a condenser tube are attached to a glass reactor, and the dispersion obtained in the previous step is heated to 60 to 70 ° C. to distill off 1021 g of a mixture of methanol and water. A mixed solvent concentrated dispersion was obtained. At this time, the content of hydrophobic spherical silica fine particles in the concentrated dispersion was 28% by mass.

Step (A3): Surface treatment step with a functional silane compound After adding 138.4 g (0.86 mol) of hexamethyldisilazane to the concentrated dispersion obtained in the previous step at room temperature, this dispersion The silica fine particles in the dispersion were trimethylsilylated by heating to 50-60 ° C. and reacting for 9 hours. Next, the solvent in this dispersion was distilled off at 130 ° C. under reduced pressure (6650 Pa) to obtain 186 g of hydrophobic spherical silica fine particles (1).

  The hydrophilic spherical silica fine particles obtained in the step (A1) were measured according to the following measuring method 1. Moreover, it measured according to the following measuring methods 2-3 about the hydrophobic spherical silica fine particle obtained through each step of said process (A1)-(A3). The obtained results are shown in Table 1.

[Measurement methods 1 to 3]
1. Particle size measurement of hydrophilic spherical silica fine particles obtained in the step (A1) Silica fine particle suspension was added to methanol so that the silica fine particles were 0.5% by mass, and subjected to ultrasonic waves for 10 minutes, The fine particles were dispersed. The particle size distribution of the fine particles treated in this way is measured with a dynamic light scattering method / laser Doppler nanotrack particle size distribution measuring device (trade name: UPA-EX150, manufactured by Nikkiso Co., Ltd.), and the volume-based median diameter is measured as particles. The diameter. The median diameter is a particle diameter corresponding to 50% cumulative when the particle size distribution is expressed as a cumulative distribution.

2. Measurement of particle diameter and measurement of particle size distribution D90 / D10 of hydrophobic spherical silica fine particles obtained in step (A3) Add silica fine particles to methanol so as to be 0.5% by mass and apply ultrasonic waves for 10 minutes. Thus, the fine particles were dispersed. The particle size distribution of the fine particles treated in this way is measured with a dynamic light scattering method / laser Doppler nanotrack particle size distribution measuring device (trade name: UPA-EX150, manufactured by Nikkiso Co., Ltd.), and the volume-based median diameter is measured as particles. The diameter. Measurement of the particle size distribution D90 / D10 is a value measured by setting D10 as the particle diameter at which accumulation is 10% from the smaller side and D90 at 90% from the smaller side in the distribution when the particle diameter is measured. To calculate D90 / D10.

3. Shape measurement of hydrophobic spherical silica fine particles The shape was confirmed by observation with an electron microscope (manufactured by Hitachi, trade name: S-4700 type, magnification: 100,000 times). The term “spherical” includes not only a true sphere but also a slightly distorted sphere. Note that the shape of such particles is evaluated by the circularity when the particles are projected two-dimensionally, and the circularity is in the range of 0.8 to 1. Here, the circularity is (peripheral length of a circle equal to the particle area) / (peripheral length of particle). The average circularity was observed with the electron microscope, 100 primary particles were measured, and the average value was used.

<Synthesis Example 2>
In Synthesis Example 1, hydrophobicity was similarly obtained except that the amounts of methanol, water and 28% ammonia water were changed to 1045.7 g of methanol, 112.6 g of water and 33.2 g of 28% ammonia water in the step (A1). 188 g of functional spherical silica fine particles (2) were obtained. Measurement was performed in the same manner as in Synthesis Example 1 using these hydrophobic spherical silica fine particles. The results are shown in Table 1.

<Synthesis Example 3>
-Process (A1):
In a 3 liter glass reactor equipped with a stirrer, a dropping funnel and a thermometer, 623.7 g of methanol, 41.4 g of water and 49.8 g of 28% aqueous ammonia were added and mixed. The solution was adjusted to 35 ° C., and 1163.7 g of tetramethoxysilane and 418.1 g of 5.4% aqueous ammonia were simultaneously added to the solution while stirring. The former was added dropwise over 6 hours and the latter over 4 hours. did. Even after the tetramethoxysilane was added dropwise, the mixture was stirred for 0.5 hours for hydrolysis to obtain a silica fine particle suspension.

-Process (A2):
To the suspension thus obtained, 11.6 g of methyltrimethoxysilane (molar ratio of 0.01 equivalent to tetramethoxysilane) was added dropwise at room temperature over 0.5 hours and stirred for 12 hours after the addition. Then, the surface of the silica fine particles was treated.

  An ester adapter and a condenser tube were attached to the glass reactor, and 1440 g of methyl isobutyl ketone was added to the dispersion containing silica fine particles that had been subjected to the above surface treatment. Distilled off over time.

-Process (A3):
To the dispersion thus obtained, 357.6 g of hexamethyldisilazane was added at room temperature, heated to 120 ° C., and reacted for 3 hours to trimethylsilylate the silica fine particles. Thereafter, the solvent was distilled off under reduced pressure to obtain 472 g of spherical hydrophobic silica fine particles (3).

  The silica fine particles (3) thus obtained were measured in the same manner as in Synthesis Example 1. The results are shown in Table 1.

<Synthesis Example 4>
Hydrophobic spherical silica fine particles (4) were obtained in the same manner as in Synthesis Example 3 except that the hydrolysis temperature of tetramethoxysilane was changed to 20 ° C. instead of 35 ° C. during the synthesis of the silica fine particles. 469 g was obtained. The same measurement as in Synthesis Example 1 was performed using this hydrophobic spherical silica fine particle (4). The results are shown in Table 1.

<Comparative Synthesis Example 1>
A 0.3-liter glass reactor equipped with a stirrer and a thermometer was charged with 100 g of deflagration silica (trade name: SOC1, manufactured by Admatechs), 1 g of pure water was added under stirring, and after sealing, an additional 60 Stir at 0 ° C. for 10 hours. Next, after cooling to room temperature, 2 g of hexamethyldisilazane was added with stirring, and after sealing, the mixture was further stirred for 24 hours. The temperature was raised to 120 ° C., and the remaining raw material and the produced ammonia were removed while ventilating nitrogen gas to obtain 100 g of hydrophobic spherical silica fine particles (5).

  The obtained silica fine particles (5) were measured in the same manner as in Synthesis Example 1. The results are shown in Table 1.

<Comparative Synthesis Example 2>
A 0.3-liter glass reactor equipped with a stirrer and a thermometer was charged with 100 g of deflagration silica (trade name: SOC1, manufactured by Admatechs), 1 g of pure water was added under stirring, and after sealing, an additional 60 Stir at 0 ° C. for 10 hours. Subsequently, after cooling to room temperature, 1 g of methyltrimethoxysilane was added with stirring, and after sealing, the mixture was further stirred for 24 hours. Next, 2 g of hexamethyldisilazane was added with stirring. After sealing, the mixture was further stirred for 24 hours. The temperature was raised to 120 ° C., and the remaining raw material and generated ammonia were removed while ventilating nitrogen gas to obtain 101 g of hydrophobic spherical silica fine particles (6). The obtained silica fine particles (6) were measured in the same manner as in Synthesis Example 1. The results are shown in Table 1.

<Examples 1-5, Comparative Examples 1-5>
Each of the above-mentioned hydrophobic spherical silica fine particles (1) to (6) was added in an amount shown in Table 2 to polytetrafluoroethylene powder (manufactured by Daikin Industries, Ltd., trade name: Polyflon TFE M-12. Average particle diameter: 25 μm, apparent The density was added to a density of 0.29 g / cm ³ and a standard specific gravity of 2.15), and the mixture was stirred and mixed for 3 minutes by a sample mill. The obtained powdery polytetrafluoroethylene powder composition was measured for basic fluidity energy, which is an index of powder fluidity. The results are shown in Table 2. The details of the measurement are as follows.
Moreover, the electron micrograph of the polytetrafluoroethylene powder composition in which the spherical hydrophobic silica fine particles of Examples 2 and 4 were adhered to the surface of the polytetrafluoroethylene powder and the spherical hydrophobic silica fine particles of Comparative Example 5 were converted to polytetrafluoroethylene. Electron micrographs of untreated polytetrafluoroethylene powder not added to the fluoroethylene powder are shown in FIGS. 1, 2 and 3, respectively.

  The fluidity was measured using a powder fluidity analyzer FT-4 (manufactured by Sysmex Corporation). The measurement principle of this apparatus will be described. A cylindrical container placed vertically is filled with powder, and while rotating two rotating blades (blades) provided at the tip of a vertical shaft rod in the powder, a certain distance (from height H1) Down to H2. The force received from the powder at this time is measured separately for the torque component and the load component, so that each work (energy) associated with the blade descending from H1 to H2 is obtained, and then the total energy of both Find the amount. The smaller the total energy measured in this way, the better the fluidity of the powder, so it is used as an index of powder fluidity. With this apparatus, the stability test of the polyimide resin composition was also conducted.

··conditions:
Container: A glass cylindrical container having a volume of 160 ml (inner diameter: 50 mm, length: 79 mm) was used.

  Blades: Two blades are attached horizontally to the tip of a stainless steel shaft rod inserted vertically into the center of the cylindrical container. A blade with a diameter of 48 mm is used. The length from H1 to H2 is 69 mm.

.. Fluidity test: As described above, the powder flow characteristics when the powder filled in the measurement container is allowed to flow from a static state are observed. The rotational speed of the blade tip is 100 mm / sec, and the total energy is measured 7 times continuously. Table 7 shows the total energy amount for the seventh time (referred to as basic fluidity energy because it is the most stable state). The smaller the total energy, the higher the fluidity.
.. Stability test: Following the fluidity test, the total energy amount is measured when the blade rotation speed is changed from 100 mm / sec → 70 mm / sec → 40 mm / sec → 10 mm / sec. As the FRI fluctuation index (FlowRateIndex) at that time is closer to 1, it can be said that the flow rate is more stable. Here, FRI variation index = (data of 10 mm / s) / (data of 100 mm / s).

<Note>
1) Particle diameter of hydrophilic spherical silica fine particles of dispersion obtained in step (A1) 2) Particle diameter of finally obtained hydrophobic spherical silica fine particles

Examples 6-11, Comparative Examples 6-11
PTFE powder prepared in Examples 1 to 5 and Comparative Examples 1 to 5 as a drip-preventing agent, 100 parts by mass of a polycarbonate resin (trade name Panlite L-1225W, manufactured by Teijin Chemicals Ltd.) as a flammable thermoplastic resin Compositions 1-10 as X parts by mass and flame retardant Tetrabromobisphenol A (manufactured by Teijin Chemicals Ltd., trade name Fireguard FG-7000) 22.5 parts by mass and antimony trioxide (Nippon Seiko Co., Ltd.) , Trade name ATOX-S) 7.0 parts by mass in a tumbler was premixed at room temperature for 10 minutes and charged into a screw feeder of a 40φ twin-screw kneading extruder. As the kneading and extruding conditions, an extrusion temperature of 290 ° C., a screw rotation speed of 130 rotations / minute, and a supply amount of 8 kg / hour were adopted to obtain a pellet-like flame-retardant resin composition of the present invention. The workability at this time was evaluated by the following points.

  Using this composition, strip test pieces (length 5 inches, width 1/2 inches, thickness 1/8 inch) were prepared using an injection molding machine (trade name SG50, manufactured by Sumitomo Heavy Industries, Ltd.). The flame resistance was investigated by performing a UL94 combustion test. The results are shown in Table 3.

Workability: Comprehensive evaluation based on the supply stability of the premixed raw material charged in the screw feeder of the extruder and the discharge stability of the strand from the extruder, and good when the work can be performed stably (+) When the supply of the raw material by the bridge is interrupted or the strand breaks, it is defined as defective (−).

Flame retardancy: The test was conducted according to UL94 (plastic flammability test method), and the materials were evaluated in three stages of UL94V-0, UL94V-1, and UL94V-2 based on the results of five test pieces. UL94V class and criteria are as follows.

UL94V-0: All of the following (a), (c), (e), (f) and (h) are satisfied.
UL94V-1: All of the following (b), (d), (e), (g) and (h) must be satisfied.
UL94V-2: All of the following (b), (d), (g) and (h) must be satisfied.

(A): Does not burn for more than 10 seconds after one flame contact.
(B): Does not burn for 30 seconds or more after one flame contact.
(C): The total burning time after flame contact for 5 times, 2 times each, 10 times in total, does not continue to burn within 50 seconds.
(D): The total burning time after flame contact 10 times a total of 5 times 5 times does not continue within 250 seconds.
(E): The absorbent cotton 12 inches below is not burned by dropping a fireball.
(F): Growing time after the second flame contact is within 30 seconds.
(G): Growing time after the second flame contact is within 60 seconds.
(H): Do not burn up to the clamp.

  From the results in Table 3, it can be seen that the product of the present invention has excellent workability and no drip.

Claims (8)

( A1) A step of obtaining hydrophilic spherical silica fine particles substantially composed of SiO ₂ units by hydrolyzing and condensing a tetrafunctional silane compound, a partial hydrolysis condensation product thereof, or a mixture thereof;
(A2) R ¹ SiO _3/2 units (wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms) are introduced onto the surface of the hydrophilic spherical silica fine particles. Process,
(A3) introducing a R ² ₃ SiO _1/2 unit (wherein each R ² is the same or different and is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms). by the method,
Hydrophobic spherical silica fine particles (1) having a particle size in the range of 0.005 to 1.00 μm, a particle size distribution D90 / D10 of 3 or less, and an average circularity of 0.8 to 1 are produced. ,
A method for producing a polytetrafluoroethylene powder composition , comprising adhering the hydrophobic spherical silica fine particles (1) of at least 0.01% by mass of the mass of the polytetrafluoroethylene powder to the surface of the polytetrafluoroethylene powder. A method for producing the hydrophobic spherical silica fine particles (1) comprises:
(A1) General formula (I):
Si (OR ³ ) ₄ (I)
(In the formula, each R ³ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms)
By substantially hydrolyzing and condensing a tetrafunctional silane compound represented by the formula, a partial hydrolysis product thereof, or a mixture thereof in a mixture of a hydrophilic organic solvent and water in the presence of a basic substance, SiO 2 A mixed solvent dispersion of hydrophilic spherical silica fine particles composed of ₂ units is obtained,
(A2) In the mixed solvent dispersion of the obtained hydrophilic spherical silica fine particles, the general formula (II):
R ¹ Si (OR ⁴ ) ₃ (II)
(Wherein, R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and each R ⁴ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms)
The surface of the hydrophilic spherical silica fine particles is treated with R ¹ SiO ₃ by adding the trifunctional silane compound represented by the formula, a partial hydrolysis product thereof or a mixture thereof to treat the surface of the hydrophilic spherical silica fine particles. _{/ 2} units (R ¹ is as described above) to obtain a mixed solvent dispersion of the first hydrophobic spherical silica fine particles,
(A3) In the mixed solvent dispersion of the obtained first hydrophobic spherical silica fine particles, the general formula (III):
R ² ₃ SiNHSiR ² ₃ (III)
(In the formula, each R ² is the same or different substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms)
A silazane compound represented by the general formula (IV):
R ² ₃ SiX (IV)
(Wherein R ² is as defined in formula (III) and X is an OH group or a hydrolyzable group), or a mixture thereof, The surface of the first hydrophobic spherical silica fine particles is thus treated, and R ² ₃ SiO _1/2 units (R ² is defined by the general formula (III) on the surface of the first hydrophobic spherical silica fine particles. The method for producing a polytetrafluoroethylene powder composition according to claim 1, wherein the second hydrophobic silica fine particles are obtained by introducing Wherein the hydrophobic spherical silica microparticles polytetrafluoroethylene powder (1) was added at 0.01 to 5.0 wt% of polytetrafluoroethylene powder, mix, according to claim 1 or 2 polytetra A method for producing a fluoroethylene powder composition. The resulting polytetrafluoroethylene powder composition by the method of any one of claims 1 to 3, the resulting polytetrafluoroethylene powder compositions, anti-drip method of thermoplastic resin added to the thermoplastic resin. The manufacturing method of the resin composition which obtains a polytetrafluoroethylene powder composition by the method of any one of Claims 1-3, and adds the obtained polytetrafluoroethylene powder composition to a thermoplastic resin . The thermoplastic resin is polycarbonate, acrylonitrile-styrene resin, acrylonitrile-butadiene-styrene resin, (polycarbonate) / (acrylonitrile-butadiene-styrene) alloy resin, polybutylene terephthalate, polyethylene terephthalate, polyphenylene ether, polypropylene and polystyrene. The method for producing a resin composition according to claim 5, wherein the resin composition is at least one resin selected from the group consisting of : The method for producing a resin composition according to claim 6, wherein the thermoplastic resin is polycarbonate. Furthermore, the manufacturing method of the resin composition of any one of Claims 5-7 containing a flame retardant.