JP2013170221A - Conductive porous polyamide microparticle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide conductive porous polyamide microparticles having improved electrical conductivity of the particles to reduce charge accumulation, improve handleability in powder handling, and reduce risk of dust explosion, etc.SOLUTION: There is provided a conductive porous polyamide microparticle having a conductive metal layer formed in a pore and on a surface of a porous microparticle of a polyamide having a spherocrystal structure.

Description

  The present invention relates to a conductive polyamide porous fine particle in which a conductive metal layer is formed in the pores and on the surface of a polyamide porous fine particle.

  By coating the surface of the polymer fine particles with a conductive component such as a metal, the fine particles provided with conductivity can be used for electromagnetic shielding materials, conductive adhesives, and antistatic measures for particles. It is used in many industrial fields. In addition, by blending a powder coated with a conductive metal component, particularly gold or silver, as a cosmetic raw material, a cosmetic having effects such as suppression of an increase in skin temperature due to reflection and absorption of infrared rays and ultraviolet rays and an ultraviolet protection function can be obtained. Are known. The shape of such conductive polymer fine particles is often such that a spherical, flaky or fibrous base material is coated with a conductive component by an electroless plating method or the like, and the fine particles having a porous structure are the base material. There are few examples.

  It is known that the polyamide porous fine particles have a large specific surface area and are excellent in light scattering properties and adsorption properties as compared with polyamide spherical particles having the same particle size. For this reason, the porous polyamide fine particles are used as a cosmetic / toiletries raw material by having a soft focus effect that suppresses shine, hides pores, spots, wrinkles, and a long lasting effect by absorbing sebum. However, since the specific surface area is large, it is easy to be charged, and it has become an industrial problem to pay special attention to the dangers of dust explosion and the like, and the handling property of the powder during processing is remarkably deteriorated. .

  Patent Document 1 describes a nylon powder obtained by treating a polyamide powder with a small specific surface area with Ni. However, the purpose is not to prevent charging by improving conductivity, but the conductivity is improved by Ni coating and the charging property is improved. The description is not seen. Further, Patent Document 2 discloses polyamide porous fine particles in which coloring is caused by localized plasmon (LPR) absorption and metal fine particles protected with a nitrogen-containing polymer are stably supported. Is colored by localized plasmon (LPR) absorption, and the supported metal nanoparticles do not have a continuous metal layer structure because they are segregated in the porous polyamide pores. It did not lead to improvement in handling and was not very effective in improving handling. Furthermore, as disclosed in Patent Document 3, the pores of polyamide porous fine particles obtained by combining fine particles of titanium oxide or fine particle zinc oxide on polyamide porous fine particles are crushed by mechanical impact during processing. The titanium oxide and zinc oxide in the pores were left in the pores in an isolated state, and the conductivity and chargeability were not improved for the blending amount.

JP-A-63-93872 JP 2008-88296 A JP 2010-185028 A

  The object of the present invention is to improve the conductivity of porous polyamide fine particles to make it difficult to be charged, improve the handling property when handling powder, and reduce the risk of dust explosion etc. It is to provide fine particles.

The present invention has been made to solve the above-described problems, and specifically has the following configuration.
(1) Conductive polyamide porous fine particles in which a conductive metal layer is formed in and on the porous pores of a polyamide porous fine particle having a spherulite structure.
(2) The conductive polyamide porous fine particles according to (1), wherein the polyamide porous fine particles have an average particle diameter in the range of 1 to 30 μm.
(3) The conductive polyamide porous fine particles according to any one of (1) to (2), wherein the specific surface area of the polyamide porous fine particles is in the range of 0.5 to 80 g / m ² .
(4) The conductive polyamide porous fine particles according to any one of (1) to (3), wherein the formed conductive metal layer is 1 to 900 parts by weight with respect to 100 parts by weight of the polyamide porous fine particles.
(5) The conductive polyamide porous fine particles according to any one of (1) to (4), wherein the volume resistivity is in the range of 10 ⁻³ to 10 ⁹ Ω · cm.
(6) The conductive polyamide porous fine particles according to any one of (1) to (5), wherein the metal forming the conductive metal layer is at least one selected from silver, copper, and nickel.

  The conductive polyamide porous fine particles of the present invention have a high conductivity and a remarkable antistatic effect because the surface of the particles and the inside of the pores are almost uniformly coated with the conductive metal layer. For this reason, the handling property and safety | security of particle | grains increase, and it can use for electronic components field | areas, such as cosmetics, a coating material, an electromagnetic wave shielding material, and a conductive adhesive, in comfort.

SEM photograph of conductive polyamide porous microparticles produced in Example 1 STEM photograph of the cross section of the conductive polyamide porous fine particles produced in Example 1

  The present invention is a conductive polyamide porous fine particle in which a conductive metal layer is formed in the pores and on the surface of a porous polyamide fine particle having a spherulite structure.

The polyamide constituting the polyamide porous fine particles used in the present invention includes those obtained by ring-opening polymerization of cyclic amide, polycondensation of amino acids, polycondensation of dicarboxylic acid and diamine, and the like. Examples of raw materials used for ring-opening polymerization of cyclic amides include ε-caprolactam, ω-laurolactam, and the like, and raw materials used for polycondensation of amino acids include ε-aminocaproic acid, ω-aminododecanoic acid, ω- Examples of the raw material used for polycondensation of dicarboxylic acid and diamine include dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, 1,4-cyclohexyldicarboxylic acid, and derivatives thereof, ethylenediamine, hexa Examples include diamines such as methylene diamine, 1,4-cyclohexyl diamine, pentamethylene diamine, and decamethylene diamine.
These polyamides may be further copolymerized with a small amount of an aromatic component such as terephthalic acid, isophthalic acid, and m-xylylenediamine.

  Specific examples of polyamides include polyamide 6, polyamide 46, polyamide 66, polyamide 610, polyamide 612, polyamide 11, polyamide 12, polyamide 6/66, polynonamethylene terephthalamide (polyamide 9T), polyhexamethylene adipa. Polyamide / polyhexamethylene terephthalamide copolymer (polyamide 66 / 6T), polyhexamethylene terephthalamide / polycaproamide copolymer (polyamide 6T / 6), polyhexamethylene adipamide / polyhexamethylene isophthalamide copolymer (polyamide 66 / 6I) ), Polyhexamethylene isophthalamide / polycaproamide copolymer (polyamide 6I / 6), polydodecamide / polyhexamethylene terephthalamide copolymer (polyamide 12 / T), polyhexamethylene adipamide / polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (polyamide 66 / 6T / 6I), polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (polyamide 6T / 6I), Examples thereof include polyhexamethylene terephthalamide / poly (2-methylpentamethylene terephthalamide) copolymer (polyamide 6T / M5T), polyxylylene adipamide (polyamide MXD6), and mixtures or copolymer resins thereof. Among these, polyamide 6, polyamide 46, polyamide 66, polyamide 610, polyamide 612, polyamide 11, polyamide 12, or polyamide 6/66 copolymer resin is preferable, and polyamide 6 is particularly preferable from the viewpoint of material handleability.

  The molecular weight of the polyamide is preferably 2,000 to 100,000, more preferably 5,000 to 40,000. If the molecular weight of the polyamide is too small, the conditions for forming the porous fine particles are narrowed, making the production difficult. On the other hand, if the molecular weight of the polyamide is too large, primary aggregates are easily formed during production, which is not preferable.

  The polyamide porous fine particles used in the present invention have a sphere equivalent number average particle diameter of 1.0 to 30 μm, preferably 1.5 to 20 μm. When the number average particle diameter is smaller than 1 μm, the particles are easily charged, and the metal plating is coated in an agglomerated state even during the conductive metal plating treatment, which is not preferable. If it is larger than 30 μm, it is not preferable because the conductive polyamide porous fine particles are roughened when used as a cosmetic raw material.

  In the sphere equivalent particle size distribution, the ratio of the volume average particle size (or volume reference average particle size) to the number average particle size (or number reference average particle size) is preferably 1 to 2.5. More preferably, it is 1-1.5. When the ratio of the volume average particle diameter to the number average particle diameter (particle size distribution index PDI) is larger than 2.5, the handling as a powder becomes worse.

  The polyamide porous fine particles used in the present invention preferably have a porous structure. The porous structure is preferable because it exhibits functions such as light scattering effect, oil absorption, and adsorption effect even after imparting conductivity.

BET specific surface area, 0.5m ² / g~80m ² / g, ^{preferably, 1m 2 / g~50m 2 / g} , and more preferably from 3m ² / g~30m ² / g. When the specific surface area is lower than 0.5 m ² / g, it becomes difficult to provide a catalyst in the electroless plating pre-process, and thus it becomes difficult to form a uniform conductive metal plating layer. Further, it is not preferable because the conductive polyamide porous fine particles after the conductive metal plating treatment are less likely to exhibit functions such as light scattering effect, oil absorption and adsorption effect. On the other hand, if it is larger than 80 m ² / g, the amount of catalyst in the pre-electroless plating process increases, which is not preferable.

  The average pore diameter is 0.01 μm to 0.5 μm, preferably 0.01 to 0.3 μm. When the average pore diameter is smaller than 0.01 μm, it may be difficult to apply the catalyst in the pre-electroless plating process.

  The porosity index (RI) is preferably 5 to 100. Here, the porosity index (RI) is defined as the ratio of the specific surface area of the porous spherical particles to the specific surface area of the smooth spherical particles having the same diameter. If the porosity index is less than 5, it is not preferable because the light scattering ability of the porous particles decreases. When the porosity is greater than 100, it becomes difficult to handle as a powder.

  The polyamide porous fine particles used in the present invention have a single particle itself as a whole or locally a spherulite structure which is a crystal structure peculiar to a crystalline polymer, or a partially deficient spherulite structure (C type, Tilde structure) and a deficient axial spherulite structure (dumbbell shape). The spherulite structure is preferable because the light scattering effect is increased. Moreover, the particle | grains which mixed the particle | grains of these various structures may be sufficient depending on a use.

  "Single particles themselves have a global or local spherulitic structure" means that polyamide fibrils grow three-dimensionally or radially from single or multiple cores near the center of a single particle. The term “local” means that the particle has a part of the structure.

  The polyamide porous fine particles used in the present invention preferably have a crystallinity measured by DSC of 40% or more. More preferably, it is 45% or more, more preferably 50% or more. The crystallinity of polyamide can be determined by X-ray analysis, DSC measurement, or density. The DSC measurement is preferred. The degree of crystallinity of the polyamide crystallized from the ordinary melt is at most about 30%. A crystallinity of 40% or more is preferable because the light scattering property increases and the ultraviolet scattering effect and soft focus property are improved. If the degree of crystallinity is low, the contrast of the difference in refractive index between the particles and the substrate is lowered, and the light scattering performance is lowered.

  The polyamide porous fine particles used in the present invention preferably have a crystallite size determined by wide-angle X-ray diffraction of 10 nm (nanometers) or more. More preferably, it is 12 nm (nanometer) or more. The larger the crystallite size, the higher the light scattering property of ultraviolet light and the higher the booster effect. On the other hand, if it is less than 12 nm, the light scattering property tends to decrease.

  Moreover, the polyamide porous fine particles can be produced by dissolving the polyamide in a good solvent for the polyamide, lowering the solubility of the solution in the polyamide, and precipitating the polyamide.

  The preferred method for producing the polyamide porous fine particles is a polyamide non-solvent at a low temperature, but a solvent that dissolves the polyamide at a high temperature is used. After the polyamide is dispersed in the solvent, the temperature is increased and the solubility of the solvent in the polyamide is increased. It can be prepared by a method of precipitating polyamide by lowering the solubility of the solvent with respect to polyamide by lowering the temperature of the solution after increasing the temperature.

  Although it is a non-solvent for polyamide at low temperatures, examples of the solvent that dissolves polyamide at high temperatures include polyhydric alcohols and mixtures thereof. Examples of the polyhydric alcohol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, glycerin, propylene glycol, dipropylene glycol, 1,5-pentanediol, hexylene glycol, and the like. Is mentioned.

  In order to promote dissolution in the solvent or to lower the dissolution temperature, an inorganic salt may be added. Examples of the inorganic salt include calcium chloride and lithium chloride. The above is not limited as long as the metal salt is an inorganic salt that acts on the hydrogen bond portion of the polyamide to promote dissolution.

  As a more preferable method for producing the polyamide porous fine particles, the above-mentioned high-temperature polyamide solution is mixed with a low-temperature solvent that acts as a non-solvent for the polyamide at least at a low temperature, whereby the entire polyamide solution is uniformly and rapidly determined. It is preferable to cool to temperature. The solvent that can be used here is a non-solvent at least at a low temperature with respect to polyamide as long as it is highly compatible with the solvent, but it is composed of the same components as the solvent, or in the case of a mixed solution Are more preferably the same composition. In the case of different components and compositions, when collecting the particles and then reusing the solvent, a lot of labor may be required for fractional collection and the like. The particles created by this method are either a single particle itself or a spherulite structure that is a crystal structure peculiar to a crystalline polymer, either locally or partially (Spherical structure, C-type). Furthermore, it has a deficient axial crystal spherulite structure (dumbbell shape).

  As said solvent, the polyhydric alcohol similar to a solvent, and mixtures thereof are mentioned. Specifically, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, glycerin, propylene glycol, dipropylene And glycol, 1,5-pentanediol, hexylene glycol and the like. These may be used as a mixture.

  The temperature and amount of the solvent used for cooling are determined by the temperature and volume of the polyamide solution to be cooled. The temperature difference between the solution and the non-solvent used for cooling is preferably within 150 ° C. When the temperature difference is larger than 150 ° C., the precipitation of polyamide starts during the addition of the non-solvent, and aggregation or the like occurs, which is not preferable. The final polyamide concentration after mixing the two liquids is preferably 15% or less. If the polyamide concentration at the time of precipitation is too high, the particles are aggregated, and in severe cases, the solution may solidify, which is not preferable.

  The mixing of the high temperature polyamide solution and the low temperature solvent may be performed by adding a low temperature solvent to the high temperature polyamide solution or adding the high temperature polyamide solution to the low temperature solvent. It is preferable to stir until. The stirring time is most preferably within 3 minutes, preferably within 2 minutes, and more preferably within 1 minute. Whether or not the two liquids are sufficiently mixed can be determined by observing the concentration fluctuation due to the difference in refractive index between the two liquids or by keeping the temperature of the liquid mixture constant within ± 1 ° C.

  Another preferable method for producing polyamide porous fine particles is a non-solvent in which polyamide cannot be dissolved in the vicinity of room temperature in a polyamide solution (A) in which polyamide is dissolved in a good solvent in which polyamide is dissolved in the vicinity of room temperature. There is a method of mixing (B). This method is a method for producing polyamide porous fine particles by reducing the solubility in polyamide. The particles created by this method are also composed of a spherulite structure, which is a crystal structure unique to a crystalline polymer, either entirely or locally, or a partially deficient spherulite structure (C-type, jade structure). Furthermore, it has a deficient axial crystal spherulite structure (dumbbell shape).

  As the good solvent in the vicinity of room temperature of the polyamide, a phenol compound or formic acid is preferable. Specifically, phenol, o-cresol, m-cresol, p-cresol, cresolic acid, chlorophenol and the like are preferable as the phenol compound. These are preferable because the crystalline polyamide is dissolved or accelerated by heating at room temperature or at a temperature of 30 to 90 ° C. Particularly preferred is phenol. Phenol is less toxic than other solvents and is safe for work. Further, it is convenient because it is easily distilled off from the obtained porous fine particles.

A freezing point depressant may be added to the polyamide solution. As the freezing point depressant, a non-solvent of polyamide can be used as long as the polyamide in the polyamide solution is not precipitated. Examples of freezing point depressants include water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-pentanol, Mention may be made of 1-hexanol, ethylene glycol, triethylene glycol, propylene glycol, glycerol and diglycerol.
By adding a freezing point depressant, the polyamide solution can be brought to a lower temperature and the polyamide porous fine particles can be precipitated.

  In order to promote dissolution in the polyamide solvent, an inorganic salt may be added to improve the solubility of the polyamide. Examples of the inorganic salt include calcium chloride and lithium chloride. The above is not limited as long as the metal salt is an inorganic salt that acts on the hydrogen bond portion of the polyamide to promote dissolution.

  The polyamide concentration in the polyamide solution (A) is preferably in the range of 0.1 to 30% by weight, more preferably in the range of 0.2 to 25% by weight. If the proportion of polyamide in the polyamide solution exceeds 30% by weight, it may be difficult to dissolve or a uniform solution may not be obtained. Moreover, even if it melt | dissolves, since the viscosity of a solution will become high and it will become difficult to handle, it is unpreferable. When the proportion of polyamide is lower than 0.1% by weight, the polymer concentration tends to be low and the product productivity tends to be low.

  The non-solvent near the room temperature of the polyamide is preferably one that is at least partially compatible with the good solvent of the polyamide solution. Examples of the non-solvent include water and / or a polyamide-insoluble organic solvent. The non-solvent may be a mixture of two or more solvents. The non-solvent is preferably one that does not dissolve 0.01% by weight or more of the polyamide in the polyamide solution at a liquid temperature of 25 ° C.

  Examples of the polyamide-insoluble organic solvent near room temperature include alkylene glycols such as ethylene glycol and propylene glycol.

  Other examples of the polyamide-insoluble organic solvent near room temperature include monohydric alcohols, dihydric alcohols, trihydric alcohols, and ketones. The monohydric alcohol is preferably a monohydric alcohol having 1 to 6 carbon atoms. It may be linear or branched. Examples of monohydric alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-pentanol, 1- Examples include hexanol. Examples of the dihydric alcohol include ethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and the like. Examples of the trihydric alcohol include glycerin. Examples of the ketone include acetone.

  When polyamide 6 is used as the polyamide, the non-solvent is preferably a mixture containing water and a polyamide-insoluble solvent (preferably a monohydric alcohol). When the polyamide is polyamide 12, it is a mixture containing alkylene glycol and a polyamide-insoluble organic solvent other than alkylene glycol (preferably a trihydric alcohol) in a non-solvent.

  In order to prepare polyamide porous fine particles, a method in which a solution and a non-solvent are mixed to temporarily form a uniform mixed solution and then allowed to stand can be used. By this operation, polyamide porous fine particles are precipitated. . The liquid temperature of the mixed solution when the polyamide porous fine particles are precipitated is preferably in the range of 0 to 80 ° C, and particularly preferably in the range of 20 to 40 ° C.

  A thickener may be added to the mixed solution of the polyamide solution and the non-solvent of the polyamide to increase the viscosity of the mixed solution for the purpose of preventing aggregation of the precipitated polyamide particles. Examples of the thickener include polyalkylene glycols having a number average molecular weight of 1000 or more (particularly in the range of 1100 to 5000). Examples of polyalkylene glycols include polyethylene glycol and polypropylene glycol. As a method of adding a thickener, either a method of adding a thickener simultaneously with mixing a polyamide solution and a non-solvent (B), or a method of adding a thickener to a mixed solution immediately after adjustment It may be a method. Two or more polyalkylene glycols can be used in combination.

  The polyamide porous fine particles prepared by the above method can be solid-liquid separated by a method such as decantation, filtration or centrifugation.

In the above method, the prepared polyamide porous fine particles can be washed with a low-viscosity solvent, which is a non-solvent of polyamide, at around room temperature in order to remove the non-solvent present on the surface and in the particles. Examples of these solvents include compounds selected from the group consisting of aliphatic alcohols, aliphatic or aromatic ketones, aliphatic or aromatic hydrocarbons, and water. Examples of the aliphatic alcohol include monovalent aliphatic alcohols having 1 to 3 carbon atoms such as methanol, ethanol, 1-propanol, and 2-propanol. Examples of the aliphatic ketone include acetone and methyl ethyl ketone. Examples of aromatic ketones include acetophenone, propiophenone, and butyrophenone. Examples of aromatic hydrocarbons include toluene and xylene. Examples of aliphatic hydrocarbons include heptane, hexane, octane, and n-decane.

  The separated and washed polyamide porous fine particles can finally be made into a dry powder through a drying step. As a drying method, general-purpose powder drying methods such as vacuum drying, constant temperature drying, spray drying, freeze drying, and fluidized tank drying can be used.

  The amount of residual solvent in the dry powder is preferably less than 10,000 ppm. If it is 10000 ppm or more, the particles themselves are liable to cause secondary agglomeration, lose the smooth feeling, and feel sticky.

  The conductive polyamide porous fine particles of the present invention can be produced by forming a conductive metal layer with a conductive metal so as to cover the surface of the polyamide porous fine particles and the inside of the pores.

  The conductive metal in the present invention is silver, gold, nickel, copper, chromium, iron, cobalt, zinc, aluminum, tin, platinum, and alloys thereof. Among these, silver, nickel, and copper are preferable from the viewpoints of coating stability and conductivity.

  The method for coating the polyamide porous fine particles is not particularly limited, and examples thereof include a mechanical support composite method such as a hybridization system (Nara Machinery Co., Ltd.), vacuum deposition, electroplating method, and electroless plating method. Among these, the electroless plating method includes a displacement plating method and an autocatalytic plating method. As a method for coating the polyamide porous fine particles, a vacuum deposition method, a mechanical support composite method, and an electroless plating method are preferable, and an electroless plating method is most preferable.

  In the case of performing the electroless plating method, the electroless plating step is performed after performing pretreatment steps such as an etching step and a catalyst applying step.

  An etching process is for raising the adhesiveness of an electroconductive metal, and is implemented as needed. The etching solution is not particularly limited, but in general, an alkaline aqueous solution such as caustic soda or an aqueous acid solution such as an aqueous chromic anhydride solution can be used.

  The catalyst application step is a step of forming a catalyst layer in the porous pores and on the surface of the polyamide porous fine particles. The method includes a method of repeating a sensitizing treatment using stannous chloride and hydrochloric acid and an activation treatment using palladium chloride and hydrochloric acid alternately several times through washing with water, or catalyzing using a colloidal substance of tin or palladium. A method of repeating the treatment and the activation treatment of tin removal using hydrochloric acid, sulfuric acid or the like several times through washing with water can be mentioned.

  The electroless plating step is a step of forming a conductive metal layer by immersing the polyamide porous fine particles on which the catalyst layer has been formed by these pretreatment steps in an electroless metal plating solution.

  In the present invention, the coating amount of the conductive metal with respect to 100 parts by weight of the polyamide porous fine particles is preferably 1 to 900 parts by weight. If the amount is 1 part by weight or less, it is difficult to improve the conductivity, and if it is 900 parts by weight or more, the conductive metal layer may fill the polyamide porous pores, thereby impairing the characteristics as porous fine particles. Furthermore, the cost increases due to an increase in the amount of metal used.

  The average particle size of the conductive polyamide porous fine particles of the present invention is almost the same as the average particle size of the original polyamide porous fine particles, and the sphere equivalent number average particle size is 1.0 to 30 μm, preferably 1.5 to 20 μm. Is preferred.

  The conductive polyamide porous fine particles of the present invention can be dispersed in a binder and a solvent to produce a conductive paste. The conductive paste can be used for electromagnetic shielding materials and conductive adhesives.

  Examples of the binder used for the conductive paste include known thermosetting resins and thermoplastic resins. For example, a methacryl resin, a polystyrene resin, a polycarbonate resin, a polyester resin, a polyolefin resin including a ring, a urethane resin, and the like can be given. The blending ratio of the conductive polyamide porous particles is preferably 0.1 to 60% by weight with respect to the total of the binder and the porous particles.

  The conductive polyamide porous fine particles of the present invention can be used as cosmetic compositions in skin care products such as foundations, facial cleansers, sunscreen agents, skin lotions, and hair shampoos.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. The crystallinity, particle diameter, average pore diameter, porosity, specific surface area, light scattering characteristics of the particles, etc. were measured as follows.

(Crystallinity)
The degree of crystallinity was measured by DSC (differential scanning calorimeter). Specifically, in a nitrogen stream at a flow rate of 40 ml / min, the heat of crystal fusion determined from the area of the endothermic peak at a heating rate of 10 ° C./min and a temperature range of 120 to 230 ° C., and the heat of crystal fusion of a known polyamide It calculated | required from ratio (the following formula). The heat of fusion of polyamide 6 is R.V. It was set to 45 cal / g according to the description of Vieweg et al., Kunststoffe IV polyamide, page 218, Carl Hanger Verlag, 1966.
χ: Crystallinity (%)
ΔHobs; heat of fusion of sample (cal / g)
ΔHm: heat of fusion of polyamide (cal / g)

(Crystallite size)
Using a RGA 2500 rotating cathode X-ray diffractometer RINT2500, using CuKα rays, tube voltage 40 kV, tube current 130 mA, scanning speed 10 ° / min, slitting conditions: DS (divergence slit) / SS (scattering slit) / A diffraction pattern was obtained in a scanning range of 15 to 40 ° under the condition of RS (light receiving slit) = 0.5 ° / 0.5 ° / 0.15 mm. From the obtained diffraction pattern, the crystallite size D when the Scherrer constant K was set to 1 was calculated from the Scherrer equation represented by the following equation.

(Where λ is the measurement wavelength, β is the half width, θ is the diffraction peak position, K is the Scherrer constant. If there are multiple diffraction peaks, the crystallite size is calculated at each peak, and the average value is calculated as the crystal Child size.)

(Average particle size)
The average particle size and particle size distribution were measured as an average value of 50000 fine particles using a Coulter counter (CC). The number average particle size, volume average particle size, and particle size distribution index (PDI) are expressed by the following equations.
Number average particle size:
Volume average particle size:
Particle size distribution index:
Here, Xi: individual particle diameter, n is the number of measurements.

(Specific surface area)
The specific surface area was measured at three points by the BET method using nitrogen adsorption.

(Average pore diameter / porosity)
The average pore diameter was measured with a mercury porosimeter. The average pore diameter was determined in the measurement range of 0.0036 to 14 μm. The porosity of the polyamide porous fine particles represents the ratio of the volume of polyamide to the volume of space in one particle. Here, the density of polyamide can be represented by ρ, and the porosity can be expressed by the following equation. here,
Vp: pore volume in the particle,
Vs: Intraparticle polymer volume.
In other words, if the cumulative pore volume in the particle (P1)
It is represented by
From the graph of the cumulative pore volume with respect to the pore diameter, the intra-particle cumulative pore volume is calculated, and the intra-particle porosity is calculated according to the following equation. At this time, the density ρ of the polyamide fine particles was obtained from the crystallinity χ, the crystal density ρc, and the amorphous density ρa obtained by DSC. Here, the crystal density (ρc) of the polyamide 6 was 1.23 cm 3 / g, and the amorphous density (ρa) was 1.09 cm 3 / g.

The degree of porosity (RI) of the polyamide porous fine particles can be expressed by the ratio of the specific surface area value Sp0 when assuming spherical particles with the same particle diameter and the BET specific surface area Sp in the case of porous fine particles. Also,
Is required. d is the diameter of the particle and ρ is the density.

(Measurement of volume resistivity)
The volume resistivity of each powder was measured as follows. Each powder was molded into a 10 mmφ cylindrical shape using a tableting machine at a pressure of 25 MPa, and then conductive silver paste (Dotite D-362: manufactured by Fujikura Kasei: volume resistivity 7 × 10 ⁻⁴ Ω · cm) Was coated on both sides, and then the resistance value was measured using a multimeter (2700 MULTITIMER: manufactured by Keithley) to determine the volume resistance value (Ω · cm).
For high resistivity powders, the deposition resistivity was determined using a powder conductivity measurement system (Hiresta UP, Mitsubishi Chemical Analytic Co.).

(Measurement of charge amount)
The charge amount of each particle was measured using a coulomb meter (NK-1002: manufactured by Kasuga Denki).

(Production Example 1)
Polyamide 6 solution having a concentration of polyamide 6 of 20% by mass by dissolving polyamide 6 (manufactured by Ube Industries: molecular weight 11,000) in a solution containing phenol and 2-propanol (IPA) in a mass ratio of 9: 1. Was prepared. To this polyamide solution, a mixed solution in which IPA and water were mixed at a mixing ratio of 3: 2.6 was added. The temperature was 20 ° C. The mixture was allowed to stand for 24 hours to complete the precipitation. Thereafter, the polymer was isolated by centrifugation, and then centrifugal dehydration was performed while applying IPA at 50 ° C. 100 times the amount of fine particles, and the particles were washed and dried. When the obtained polymer particles were observed with a scanning electron microscope, they were relatively uniform spherical porous particles having a number average particle diameter of 5.5 μm and a volume average particle diameter of 6.5 μm. The average pore size was 0.05681 μm, PDI was 1.18, the specific surface area was 21.4 m ² / g, the porosity index RI was 42.1, and the crystallinity of the polymer particles was 51.7%. The crystallite size determined from wide-angle X-ray diffraction was 11.3 nm. In the porous particles, nylon fibrils grew three-dimensionally radially from a single or a plurality of nuclei at the center, and the single particles themselves had a spherulite structure.

Example 1
10 g of the polyamide porous fine particles obtained in Production Example 1 were added to a 1% by weight palladium sulfate solution and stirred at 30 ° C. for 30 minutes to fully adsorb palladium ions in the pores and on the surface of the polyamide porous fine particles. . The particles were washed with distilled water and then added to a 0.5% by weight dimethylamine borane solution to perform palladium activation treatment. The obtained powder cake is sufficiently dispersed in distilled water, and then stirred at 50 ° C., and electroless plating solution comprising silver sulfate 50 g / L, sodium hypophosphite 40 g / L, and citric acid 50 g / L. (PH 7.5) was gradually added to perform electroless silver plating. After the addition of 1.2 L, the addition of the plating solution was stopped, the alcohol was replaced, and then dried at room temperature to prepare conductive polyamide porous fine particles. FIG. 1 shows an SEM photograph of the particles prepared. The surface is silver-plated and the presence of porous pores can be confirmed. FIG. 2 shows a cross-sectional STEM photograph. It can be confirmed that the pores and the surface of the particles are silver-plated. The prepared conductive particles had a number average particle size of 5.6 μm and a volume average particle size of 6.6 μm, and no significant variation in the particle size due to plating treatment was observed. The silver coating amount of the prepared conductive particles was about 5 g. Further, the volume resistivity was 6.1 × 10 ⁻¹ Ω · cm, and the charge amount of the particles was below the measurement range of 1 nC (nanocoulomb) or less, and was almost not charged. For this reason, there was no problem in the handleability of the powder.

(Comparative Example 1)
The volume resistivity of the polyamide porous fine particles in Production Example 1 was measured and found to be 4.8 × 10 ¹³ Ω · cm. The charge amount of the powder was 40 to 100 nC (nanocoulomb), and the powder was charged, and the handleability of the powder was poor.

(Example 2)
In Example 1, conductive polyamide porous fine particles were prepared by changing the addition amount of the plating solution to 2.7 L. The coating amount of silver was about 7 g from the weight of the prepared conductive particles. The prepared conductive particles had a number average particle size of 5.6 μm and a volume average particle size of 6.7 μm, and no significant variation in the particle size due to plating treatment was observed. Further, the volume resistivity was 6.4 × 10 ⁻² Ω · cm, and the charge amount of the particles was below the measurement range of 1 nC (nanocoulomb) or less and was almost not charged. For this reason, there was no problem in the handleability of the powder.

(Example 3)
In Example 1, the plating solution was a 1: 2 mixed solution of electroless nickel plating solution concentrates A and B (Top Nicolon F-153A and Top Nicolon F-153B, manufactured by Okuno Pharmaceutical Co., Ltd.) 1 L, and pure water As a mixed solution consisting of 30 L, plating was performed at 63 ° C. using 3 L. The coating amount of nickel was about 1 g from the weight of the prepared conductive particles. The prepared conductive particles had a number average particle size of 5.6 μm and a volume average particle size of 6.7 μm, and no significant variation in the particle size due to plating treatment was observed. The charge amount of the particles was below the measurement range of 1 nC (nanocoulomb) or less and was almost not charged. For this reason, there was no problem in the handleability of the powder.

Example 4
In Example 1, the plating solution is 3.6 L as a mixed solution composed of an electroless copper plating solution OPC700 mixed solution (MK-A, MK-B, MK-C, manufactured by Okuno Pharmaceutical Co., Ltd.) 4 L and pure water 21 L. And plated at 23 ° C. From the weight of the prepared conductive particles, the coating amount of copper was about 4 g. The produced conductive particles had a number average particle size of 5.5 μm and a volume average particle size of 6.7 μm, and no significant variation in the particle size due to the plating treatment was observed. Further, the volume resistivity was 1.4 × 10 ⁷ Ω · cm, and the resistance value was high. The charge amount of the particles was below the measurement range of 1 nC (nanocoulomb) or less and was almost not charged. For this reason, there was no problem in the handleability of the powder.

(Example 5)
In Example 4, conductive polyamide porous fine particles were prepared by changing the addition amount of the plating solution 8.5L. From the weight of the prepared conductive particles, the coating amount of copper was about 7 g. The prepared conductive particles had a number average particle size of 5.6 μm and a volume average particle size of 6.7 μm, and no significant variation in the particle size due to plating treatment was observed. Further, the volume resistivity was 5.1 × 10 ⁻² Ω · cm, and the charge amount of the particles was below the measurement range of 1 nC (nanocoulomb) or less, and was almost not charged. For this reason, there was no problem in the handleability of the powder.

  The conductive porous polyamide fine particles of the present invention have a spherulite structure, improve the conductivity of the polyamide porous fine particles having a specific particle diameter and specific surface area, make them difficult to be charged, and handle when handling powder Can be improved. Further, by imparting electrical conductivity, the risk of dust explosion and the like can be reduced, and it can be supplied as an electronic material or cosmetic raw material.

Claims (6)

Conductive polyamide porous fine particles in which a conductive metal layer is formed in the pores and on the surface of polyamide porous fine particles having a spherulite structure. The conductive polyamide porous fine particles according to claim 1, wherein the polyamide porous fine particles have an average particle diameter in the range of 1 to 30 μm. 3. The conductive polyamide porous fine particles according to claim 1, wherein the specific surface area of the polyamide porous fine particles is in the range of 0.5 to 80 g / m < ² >. The conductive polyamide porous fine particles according to any one of claims 1 to 3, wherein the formed conductive metal layer is 1 to 900 parts by weight with respect to 100 parts by weight of the polyamide porous fine particles. The conductive polyamide porous fine particles according to any one of claims 1 to 4, wherein the volume resistivity is in the range of 10 ^-3 to 10 ⁹ Ω · cm. The conductive polyamide porous fine particles according to any one of claims 1 to 5, wherein the metal forming the conductive metal layer is at least one selected from silver, copper, and nickel.