JP2013067875A - Polytetrafluoroethylene porous body and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polytetrafluoroethylene porous body, and to provide a method for producing the same.SOLUTION: The polytetrafluoroethylene porous body is formed by integrating particulates of polytetrafluoroethylene and ultra fine fibers. The method for producing the polytetrafluoroethylene porous body comprises giving mechanical shearing force to a water dispersion of the particulates of polytetrafluoroethylene.

Description

  The present invention relates to a polytetrafluoroethylene porous body and a method for producing the same.

  Conventionally, polytetrafluoroethylene fiber production methods include a matrix spinning method (for example, see Patent Documents 1 to 3), a split peeling method, a paste extrusion method (for example, see Patent Documents 3 and 4), and the like. With the matrix spinning method, viscose, polyvinyl alcohol, sodium alginate and the like are used as a matrix and discharged into a coagulating liquid with a mixed liquid of an aqueous dispersion of a polytetrafluoroethylene resin, and then washed and refined. Bake. In the split peeling method, polytetrafluoroethylene powder is compressed by a cylinder, sintered, split peeled, and stretched. The paste extrusion method is a method of kneading polytetrafluoroethylene powder with a wax-like lubricant to form a paste, extruding it from a die and forming it into a rod or film, then removing the lubricant and stretching it. Baking according to In these methods, it is difficult to produce fine fibers having a diameter of about 1 μm or less, and therefore it is also difficult to produce a porous body containing fine fibers.

  As a polytetrafluoroethylene porous body, a production method is disclosed in which a mixture of polytetrafluoroethylene powder and a pore-forming agent is extruded or compression-molded and then the pore-forming agent is removed (for example, Patent Document 5). , 6). These porous bodies are suitable as thick products, and a porous body containing fine fibers having a diameter of about 1 μm or less could not be produced.

JP 2006-207097 A Japanese Patent No. 2571379 Japanese Patent No. 3327027 JP-A-8-296114 Japanese Patent Laid-Open No. 11-124458 JP 2009-197147 A

  The subject of this invention is providing the polytetrafluoroethylene porous body and its manufacturing method.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found a polytetrafluoroethylene porous body in which polytetrafluoroethylene fine particles and ultrafine fibers are integrated and a method for producing the same.

  According to the present invention, a specific porous body formed by integrating polytetrafluoroethylene fine particles and ultrafine fibers can be produced.

An example of the surface electron micrograph (10000 magnification) in the polytetrafluoroethylene porous body produced in Example 1 of the present invention is shown. An example of the electron micrograph (10000 magnification) of the surface in the polytetrafluoroethylene porous body produced in Example 2 of this invention is shown. An example of the electron micrograph (10000 magnification) of the surface in the polytetrafluoroethylene porous body produced in Example 5 of this invention is shown. An example of the electron micrograph (10000 magnification) of the surface in the polytetrafluoroethylene porous body produced in Example 6 of this invention is shown. It is an example of the electron micrograph (5000 magnifications) of the polytetrafluoroethylene used in the comparative example 1 of this invention.

  The polytetrafluoroethylene porous body in the present invention means a porous body formed by integrating polytetrafluoroethylene fine particles and ultrafine fibers. That is, polytetrafluoroethylene ultrafine fibers exist between the polytetrafluoroethylene fine particles, and the fine particles and the ultrafine fibers form a three-dimensional network. It is not always necessary for each fine particle to be connected to an ultrafine fiber. The fine particles may be linearly connected or may be aggregated with two or more widths. Only one ultrafine fiber may be formed between two fine particles, or a plurality of ultrafine fibers may be formed. The ultrafine fiber may be branched. The size of the fine particles is preferably 1 to 1000 nm in diameter, more preferably 10 to 500 nm, and even more preferably 50 to 500 nm. If the thickness is less than 1 nm, the production efficiency of the porous body may deteriorate. If it is larger than 1000 nm, the aggregate area of the fine particles may be larger than necessary, and if the aggregated portion is pressure-bonded, a film may be formed. The ultrafine fiber preferably has a diameter of 0.1 to 800 nm, more preferably 1 to 500 nm, and still more preferably 10 to 200 nm. If the thickness is less than 0.1 nm, the fibers are thin and weak, so that they are easily cut. If the thickness is larger than 800 nm, the pore size of the porous body may be larger than necessary.

  The polytetrafluoroethylene porous body of the present invention can be produced by applying a mechanical shearing force to an aqueous dispersion of polytetrafluoroethylene fine particles. The polytetrafluoroethylene fine particles are preferably prepared by emulsion polymerization. The aqueous dispersion may contain a surfactant. The surfactant is preferably nonionic. The solid content concentration of polytetrafluoroethylene in the aqueous dispersion is preferably 0.1 to 70% by mass, more preferably 1 to 60% by mass, and still more preferably 10 to 50% by mass. If it is less than 0.1% by mass, the addition efficiency of the mechanical shearing force may deteriorate. When it is more than 70% by mass, the self-bonding force after drying is strong and may become too hard.

  Examples of the device that generates the mechanical shear force include a paint conditioner, a paint shaker, a high-pressure homogenizer, a high-speed homogenizer, a stone mortar, a grinding device, and a mill. Although the details of the mechanism of the formation of the porous body of the present invention are not known, it was previously aggregated and adhered in the aqueous dispersion by applying a mechanical shearing force to the aqueous dispersion of the polytetrafluoroethylene fine particles. It is considered that the fine particles are torn apart to form ultrafine fibers between the fine particles, and a porous body in which the fine particles and the ultrafine fibers are integrated is formed. The polytetrafluoroethylene porous material of the present invention may be stored in a dry state or in a wet state.

  The polytetrafluoroethylene porous material of the present invention may be used alone, mixed with other materials, or combined with other molded products. When used alone, it may be processed into a fiber shape, a sheet shape, or other molded products. For compounding with other moldings, polytetrafluoroethylene porous material can be added, mixed, encapsulated, embedded, encased, coated, impregnated into other molded products, or polytetrafluoroethylene porous material can be It refers to molding into a fiber shape, a sheet shape, or other shapes, and laminating and bonding these with other molded products and fitting them into a predetermined frame. The polytetrafluoroethylene porous body may be fired as necessary regardless of whether it is a single, a mixture, a single molded product, or a composite molded product. The firing time when not used alone may be before or after mixing with other materials, before or after making a single molded product, or before or after making a composite molded product. The firing temperature is preferably 280 to 450 ° C, more preferably 300 to 420 ° C, and further preferably 320 to 400 ° C. Firing may be performed in an atmosphere at a predetermined temperature.

  FIGS. 1-4 is an example of the electron micrograph of the polytetrafluoroethylene porous body produced in the Example of this invention. It can be confirmed that a porous body formed by integrating fine particles of polytetrafluoroethylene and ultrafine fibers is formed. The diameter of the fine particles forming the porous body of FIGS. 1 to 4 is about 200 nm, and the diameter of the ultrafine fiber is about 40 to 100 nm.

  FIG. 5 is an example of an electron micrograph of the polytetrafluoroethylene fine particles used in the present invention. Since no mechanical shearing force was applied, the fine particles were in an aggregated state, and no ultrafine fibers were present between the fine particles, indicating that a porous body in which the fine particles and the ultrafine fibers were integrated was not formed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a present Example.

Example 1
An aqueous dispersion of polytetrafluoroethylene (manufactured by Daikin Industries, Polyflon (registered trademark) PTFE D-210C, solid content concentration 60% by mass) was treated with a paint conditioner for 5 hours. Alumina balls having a diameter of 4 mm were used. After the treatment, the alumina balls were removed to obtain a wet polytetrafluoroethylene porous body.

(Example 2)
It processed with the paint conditioner like Example 1 except having added ion-exchange water to the polytetrafluoroethylene aqueous dispersion used in Example 1, and having changed solid content concentration into 30 mass%. After the treatment, the alumina balls and the supernatant were removed, and a wet polytetrafluoroethylene porous body was recovered.

(Example 3)
It processed with the paint conditioner like Example 1 except having added ion-exchange water to the polytetrafluoroethylene aqueous dispersion used in Example 1, and having changed solid content concentration into 10 mass%. After the treatment, the alumina balls and the supernatant were removed, and a wet polytetrafluoroethylene porous body was recovered.

Example 4
It processed with the paint conditioner like Example 1 except having added ion-exchange water to the polytetrafluoroethylene aqueous dispersion used in Example 1, and having changed solid content concentration into 1 mass%. After the treatment, the alumina balls and the supernatant were removed, and further centrifuged to precipitate a solid, and the supernatant was removed to collect a wet polytetrafluoroethylene porous material.

(Example 5)
It processed with the paint conditioner like Example 1 except having added ion-exchange water to the polytetrafluoroethylene aqueous dispersion used in Example 1, and having changed solid content concentration into 0.6 mass%. After the treatment, the alumina balls and the supernatant were removed, and further centrifuged to precipitate a solid, and the supernatant was removed to collect a wet polytetrafluoroethylene porous material.

(Example 6)
It processed with the paint conditioner like Example 1 except having added ion-exchange water to the polytetrafluoroethylene aqueous dispersion used in Example 1, and having changed solid content concentration into 0.1 mass%. After the treatment, the alumina balls and the supernatant were removed, and further centrifuged to precipitate a solid, and the supernatant was removed to collect a wet polytetrafluoroethylene porous material.

(Example 7)
The sample was treated with a paint conditioner in the same manner as in Example 1 except that ion-exchanged water was added to the polytetrafluoroethylene aqueous dispersion used in Example 1 to change the solid content concentration to 0.06% by mass. After the treatment, the alumina balls and the supernatant were removed, and further centrifuged to precipitate a solid, and the supernatant was removed to collect a wet polytetrafluoroethylene porous material.

(Example 8)
The polytetrafluoroethylene aqueous dispersion used in Example 2 was treated with a high-speed homogenizer at 6400 rpm for 60 minutes. After the treatment, a solid was precipitated by centrifuging, and the supernatant was removed to recover a wet polytetrafluoroethylene porous material.

(Comparative Example 1)
The aqueous dispersion of polytetrafluoroethylene used in Example 1 was centrifuged to precipitate a solid. The supernatant was removed, the precipitate was dried, and polytetrafluoroethylene was recovered.

[Evaluation]
As a result of observing the polytetrafluoroethylene porous body produced in the examples of the present invention and the polytetrafluoroethylene collected in the comparative example with an electron microscope, the polytetrafluoroethylene porous bodies produced in Examples 1 to 8, It was confirmed that the polytetrafluoroethylene fine particles and the ultrafine fibers were integrated. On the other hand, the polytetrafluoroethylene of Comparative Example 1 was composed only of fine particles, and a porous body in which the fine particles and ultrafine fibers were integrated was not formed.

  Applications of the polytetrafluoroethylene porous material of the present invention include filters, separators, artificial blood vessels, and heat insulating materials.

Claims (2)

  A polytetrafluoroethylene porous body, wherein polytetrafluoroethylene fine particles and ultrafine fibers are integrated.   A method for producing a porous polytetrafluoroethylene comprising applying a mechanical shearing force to an aqueous dispersion of polytetrafluoroethylene fine particles.