JP2018059032A - Solid molding of fluorine resin and metal oxide, and method for producing the solid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide various round-bar solid moldings, such as films or rods, formed by mixing fluororesin fine particles with metal oxide fine particles, and a method for producing the solid.SOLUTION: The present invention provides a fluorine resin-metal oxide solid mixture in which fluorine resin fine particles with a particle size of 100-500 nm and fine particles of one or more metal oxides with a particle size of 5-200 nm are uniformly dispersed mixedly.SELECTED DRAWING: Figure 1

Description

The present invention relates to various round bar molded body solids such as films and rods composed of a mixture of fluororesin fine particles and metal oxide fine particles, and a method for producing the solids.

  Conventional fluoropolymers are superior in heat resistance and cold resistance compared to ordinary plastics such as polyethylene and polypropylene, and organic polymers, and have high resistance to various chemicals including acid and alkali, that is, chemical resistance and corrosion resistance, and are nonflammable. In addition, it has high electrical insulation and low dielectric loss, and is non-adhesive and non-wetting, repels water and oil, and has low friction and moderate elasticity, so it can be used for molds, containers, wires, and thermometers. It is widely used for coating various materials and product surfaces such as various sensors, gaskets and packings, and frying pans. This type of coating is usually performed by lining a fluororesin film, coating or impregnating a dispersion of fluororesin fine particles. (For example, patent document 1).

However, the conventional fluororesin is incombustible and excellent in heat resistance as compared with a normal organic polymer, but its thermal expansion coefficient is approximately an order of magnitude larger than that of a normal organic polymer resin and is soft. For example, the thermal expansion coefficient at room temperature (x10 ⁻⁶ / ° C.) is acrylonitrile butadiene styrene (ABS) resin, polyamide (PA), polyimide (PI), polycarbonate (PC), polyethylene terephthalate (PET), polyvinyl chloride (PVC) and epoxy resin (EP) are 74, 80, 54, 70, 60, 70 and 62, respectively, whereas conventional fluororesins are 200-790. For this reason, in the fluororesin, the dimension at the time of shaping | molding was not stabilized, and it was difficult to give surface treatments, such as a coating and modification useful for multifunctionalization and high functionality.

  Conventional fluororesins are also extremely excellent insulating materials and are very easily charged. In fact, it is positioned as a substance that is most likely to be negatively charged in the charge train. Since electrification can cause flammable explosions of flammable gases and solvents and dielectric breakdown of fluororesin products themselves, antistatic and antistatic measures for fluororesins were extremely important.

The removal of the charge is usually performed by attaching a ground to the fluororesin and its product or mixing a conductive material with the fluororesin, but such a method is often difficult. For example, surface coating or modification is an operation or process that is frequently or indispensably performed to achieve multiple functions and high performance, but in the case of fluororesins that are extremely easily and strongly charged, the coating solution Is often played and cannot be coated. At this time, even if the earth is used, the workability is poor, and if mixed with the current conductive material, that is, carbon black (CB), carbon fiber (CF), carbon nanotube (CNT) or metal fine powder, the mixture thereof The resulting surface may not be compatible with subsequent coatings or modifications.

Furthermore, although the non-wetting property and non-adhesiveness of the fluororesin have a great advantage that they are difficult to get dirty, the coating solution is difficult to be applied to surface coating and modification, which is a major obstacle.

In conventional fluororesins, inorganic fillers are added to improve and improve wear resistance, compression resistance, cold flow characteristics, sliding characteristics, electrical conductivity, etc., and glass fiber, carbon fiber, graphite, carbon CNT, molybdenum disulfide, silica and the like are used.
However, these are not intended to modify the surface properties for multifunctional / high functionality of fluororesin, such as adjustment and improvement of wettability, adhesiveness, and chargeability. It was difficult to say that it was consistent with the modification of surface characteristics.

Conventional filler-containing fluororesin solids are usually obtained by evaporating and drying an aqueous dispersion of fluororesin fine particles in which filler components have been added and mixed in advance, kneading fluororesin powder and filler powder, and It is obtained by a subsequent molding process. In general, the degree of mixing, that is, the mixing and dispersibility of the particles, is expected to be higher by evaporating and drying the mixed dispersion than by kneading the powders. It is essential that the fluororesin fine particles and the filler component are uniformly dispersed and mixed in the mixed solution. However, there are very few types of fillers that become a homogeneous mixed dispersion by adding and mixing the filler to the fluororesin fine particle aqueous dispersion.

In Patent Document 2-4, colloidal sol solution of inorganic fine particles, specifically silica, titanium oxide, zeolite, aluminum oxide (alumina), zinc oxide, antimony pentoxide, as an additive that is uniformly dispersed by mixing with a fluororesin emulsion. , Silicon carbide, silicon nitride, aluminum nitride, lead oxide, tin oxide, magnesium oxide, and the like, and many types of additives are said to be suitable for preparing a homogeneous mixed dispersion with a fluororesin emulsion. However, in the examples in the above-mentioned patent documents, the preparation of homogeneous mixed dispersions is all limited to silica, and there are no examples of colloidal solutions of inorganic fine particles other than silica.

Further, most of the additives that are uniformly dispersed by mixing with the fluororesin emulsion are silica sol and organosilicate solution having excellent viscosity stability, and alumina sol is known to some extent (Patent Documents 1-6). In addition, these additions are aimed at improving the mechanical strength, heat resistance, dimensional stability, compression creep properties and melt moldability of the fluororesin solids finally obtained. Not intended.

In addition, the fluororesin-metal oxide mixed solution in which the fluororesin emulsion and the metal oxide are mixed is immediately after mixing, even if the metal oxide is uniformly dispersed, if it is left for a while, liquid-liquid separation or solid-liquid There was a disadvantage of causing separation.
Therefore, it is difficult to obtain mixed dispersions as well as solid materials such as filler-containing fluororesin powders and films intended to modify and adjust the surface properties of the fluororesin.

JP 2006-117900 A JP2007-119769A JP 2008-115335 A JP 2008-115336 A JP-A-8-258228 JP2012-219126

  In view of the above problems, it is an object to provide a solid material in which a fluororesin emulsion and a metal oxide are uniformly dispersed, and a method for producing the same.

  In order to solve the above-mentioned problems, the inventors have extensively searched for a combination of a fluororesin fine particle aqueous dispersion or emulsion and a metal oxide colloidal sol, and repeatedly conducted trial and error on their blending and blending methods. Repeated. The inventors quickly dried the liquid that was mixed and stirred to obtain a uniform state, whereby the fluororesin fine particles having a particle size of 100 to 500 nm and one or more metal oxide fine particles having a particle size of 5 to 200 nm were uniformly mixed and dispersed. Have discovered a fluororesin-metal oxide mixed solid having improved and improved wettability, adhesiveness and chargeability on the surface of solids such as films, coating films and bulk, and a method for producing the same.

The invention according to claim 1 is a fluororesin-metal oxide mixed solid in which fluorine resin fine particles having a particle size of 100 to 500 nm and one or more metal oxide fine particles having a particle size of 5 to 200 nm are uniformly mixed and dispersed. About.

The invention according to claim 2 is a polymer or copolymer of monomers in which the fluororesin fine particles are selected from tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, perfluoro (alkyl vinyl ether), vinylidene fluoride and vinyl fluoride. 2. The fluororesin-metal oxide mixed solid according to claim 1, which is a resin fine particle composed of a coalescence and has a molecular weight of 1 × 10 ⁴ to 1 × 10 ⁷ .

The invention according to claim 3 is characterized in that the metal oxide is one or more metal oxides selected from alumina, titanium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, cerium oxide, iron oxide, tin oxide and niobium oxide. The fluororesin-metal oxide mixed solid according to claim 1, which is a product.

In the invention according to claim 4, the fluororesin content in the fluororesin-metal oxide mixed solid is 3 to 100 times the metal oxide content in weight ratio. The fluororesin-metal oxide mixed solid described in 1.

According to a fifth aspect of the invention, an aqueous dispersion of fluororesin fine particles and a metal oxide fine particle sol are fluorine at a weight ratio with respect to the content of metal oxide fine particles in the liquid at a temperature of 5 to 300 ° C. under normal pressure. A step of obtaining a uniform mixed dispersion by mixing resin fine particles 3 to 100 times and water 10 to 120 times and further adding a surfactant or without adding a surfactant;
A step of producing a uniformly mixed powder by spray-drying the uniformly mixed dispersion liquid, wherein the fluororesin-metal oxide mixed solid according to any one of claims 1 to 4 is used. It relates to a manufacturing method.

In the invention according to claim 6, the method for producing the fluororesin-metal oxide mixed solid from the homogeneously mixed powder includes a doctor blade method, pressurization, pressurization / heating, melting, and an extrusion or stretching operation thereof. The process for manufacturing a fluororesin-metal oxide mixed solid according to claim 5, comprising a treatment step selected from the group consisting of:

In the fluororesin-metal oxide mixed solid of the present invention, the fluororesin and metal oxide fine particles are uniformly mixed and dispersed with each other. That is, the original size or a size close to the original size, in other words, the nanoparticles are uniformly dispersed and mixed at the size level. Therefore, it can be easily formed into a film or a bulk body of a desired shape by heat and / or pressure. Further, the method for producing a mixed solid of the present invention is based on the content of the metal oxide fine particles in the liquid at a temperature of 5 to 300 ° C. under normal pressure with an aqueous dispersion of fluororesin fine particles and a metal oxide fine particle sol. Because it is manufactured by mixing fluororesin fine particles 3 to 100 times and water 10 to 120 times by weight ratio and spray drying, it is simple, energy-saving, extremely safe and extremely economical. .

It is a SEM photograph in one embodiment of the fluororesin-metal oxide mixed solid of the present invention. It is a SEM photograph in other embodiments of the fluororesin-metal oxide mixed solid of the present invention.

<Configuration of fluororesin-metal oxide mixed powder>
The fluororesin-metal oxide mixed solid of the present invention is basically obtained by mixing a fluororesin fine particle dispersion (emulsion) and a metal oxide fine particle dispersion (sol) and instantaneously spray-drying. The fluororesin fine particles and the metal oxide fine particles are uniformly dispersed and mixed at the particle size level.

The fluororesin fine particle in the present invention is a resin composed of a polymer or copolymer of a monomer selected from tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, perfluoro (alkyl vinyl ether), vinylidene fluoride and vinyl fluoride. Fine particles which are dispersed in water are used for preparing the fluororesin-metal oxide mixed solid of the present invention.

The metal oxide fine particles in the present invention are titanium oxide (titania), zirconium oxide (zirconia), lanthanum oxide (lanthana), neodymium oxide, cerium oxide (ceria), yttrium oxide (yttria), tin oxide, iron oxide, niobium oxide. , And aluminum oxide (alumina), and an aqueous colloidal sol of these fine particles is used to obtain the fluororesin-metal oxide mixed solid of the present invention.

In order to increase the degree of mixing of the fluororesin and the metal oxide, it is preferable that the fluororesin fine particles and the metal oxide fine particles have a small molecular weight and a small size. More specifically, the fluororesin fine particles preferably have a molecular weight of 1 × 10 ⁴ to 1 × 10 ⁷ and a particle size in the range of 100 to 500 nm, and the metal oxide fine particles preferably have a size of 2 to 150 nm, preferably Is preferably in the range of 2 to 50 nm.
The molecular weight of the fluororesin fine particles is preferably 1 × 10 ⁴ to 1 × 10 ^7, more preferably 2 × 10 ⁴ to 1 × 10 ⁷ .
When it is smaller than this range, the coating film tends to be brittle, and when it is larger than this range, the melt viscosity is too high and the PTFE particles tend to be hardly fused.

The content of the fluororesin in the fluororesin-metal oxide mixed powder is appropriately determined according to the use of the mixed powder, but if the content of the fluororesin is too small, flexibility and flexibility are lost. On the other hand, if the amount is too large, the surface does not exhibit wettability and adhesiveness, and is easy to be charged and the amount thereof increases, so the amount of mixed metal oxide and fluororesin content is the weight ratio of fluororesin content. It is 1 to 500 times, preferably 3 to 100 times the metal oxide content. At this time, the type of metal oxide to be mixed may be one type or two or more types, and may be appropriately selected according to the purpose.

<Method for producing fluororesin-metal oxide mixed solid>
The fluororesin-metal oxide mixed solid of the present invention is produced by mixing an aqueous dispersion of fluororesin fine particles and a metal oxide fine particle sol, and spraying and drying. In addition, the composition of the mixed solution at this time is 1 to 500 times, preferably 3 to 100 times, and 5 to 200 times, preferably 10 to 120 times as much as the fluororesin fine particles, by weight ratio with respect to the content of the metal fine particles. It is desirable to prepare so that it may become the range.
The aqueous dispersion of fluororesin fine particles may be pure fluororesin powder dissolved in water or a commercially available aqueous dispersion.

The mixing is not particularly defined as long as the mixed liquid of the fluororesin fine particle aqueous dispersion and the metal oxide fine particle sol becomes a homogeneous mixed dispersion even if it is instantaneous. Therefore, a mixed powder in which the fluororesin fine particles and the metal oxide fine particles are uniformly mixed and dispersed is usually obtained simply by spraying and drying a uniform mixed dispersion having an appropriate viscosity at room temperature under normal pressure. Of course, if the viscosity of the liquid mixture is too high, the spraying / drying process will not proceed smoothly. For this reason, to achieve an appropriate viscosity, dilution, temperature and pressure should be made higher or lower than room temperature and normal pressure, respectively. May be adjusted.

Similarly, when the mixed liquid of the aqueous dispersion of fluororesin fine particles and the metal oxide fine particle sol easily forms a uniform mixed dispersion liquid, and when liquid-liquid separation occurs without being mixed well, A mixed powder in which fluororesin fine particles and metal oxide fine particles are uniformly mixed and dispersed can be easily obtained. It is easy to make a liquid mixture that has been liquid-liquid separated by stirring, especially high-speed stirring, or by jet-jet mixing of liquid-liquid separated solutions to form a uniform mixed dispersion. In this state, spray and dry operations should be performed. Thus, a uniformly mixed and dispersed powder is obtained.
In addition, even a liquid mixture that undergoes liquid-liquid separation if a surfactant is not added, it is easy to make a uniform mixed dispersion by stirring, particularly high-speed stirring, or by jet-jet mixing of liquid-liquid separated solutions. In this state, by performing the spraying / drying operation, a uniformly mixed and dispersed powder can be obtained, so that a uniformly mixed and dispersed powder without a surfactant can be produced.
In the present invention, a surfactant may or may not be added to the aqueous dispersion of fluororesin fine particles and the metal oxide fine particle sol.
Surfactants are blended to increase intermolecular force. However, because of the effect, the powders tend to become agglomerated, so the inventors of the present invention added 10% alumina sol to the Teflon dispersion without any surfactant. When mixed and sprayed and dried, a good powder was obtained.
This homogeneous mixed powder is a fluororesin-metal oxide mixed solid by a treatment process selected from the group consisting of a doctor blade method, pressurization, pressurization / heating, melting, and a combination thereof with an extrusion or stretching operation. Manufacturing.

Precipitation and gelation are caused by aggregation / aggregation of particles and huge cross-linking between particles with a solvent or the like interposed between the particles. Therefore, in order to prevent precipitation and gelation, it is necessary to first prevent aggregation / aggregation and cross-linking of particles. As a measure for this, it is usually to repel particles or increase the distance between particles. Done. Specifically, the particles are given the same charge (charged) to repel each other, the particles are surrounded by a surfactant to form a composite micelle, or more simply diluted with a solvent.
In the case of a metal oxide colloid, even when a composite micelle is formed, the particles are repelled and dispersed by charging.

In general, the charge amount of the particles is closely related to the pH of the solution. In other words, it is extremely sensitive to pH. Therefore, the pH of the oxide sol used for the preparation of the fluororesin-metal oxide mixed dispersion of the present invention also has an appropriate range for preventing the aggregation, and this varies depending on the metal species. Thus, the pH of the metal oxide sol used in the present invention is 2.5 to 13.5, preferably 3 to 13 for titania, 6.5 to 9, preferably 7 to 8.5 for zirconia, and 7 to 10 for lantana. 7.5 to 9.5, 7 or more preferably 7 to 10 for neodymium oxide, 6 to 10 preferably 7 to 9 for ceria, 2 to 12 preferably 2 to 11 for tin oxide, 5.5 to iron oxide 8.5, preferably 6-8, and alumina, 3.4-9.5, preferably 4.7-8.5. If the pH of each metal oxide sol is out of the above range, gelation or precipitation occurs in mixing with the fluororesin fine particle aqueous dispersion, depending on the type of fluororesin fine particle aqueous dispersion used. This makes it easier to spray from the nozzle.

  The preparation of the fluororesin-metal oxide mixed dispersion used in the spraying / drying process is greatly influenced not only by the pH of the metal oxide sol used but also by the pH of the fluororesin fine particle aqueous dispersion. This is because the pH of the mixture produced by mixing the metal oxide sol and the fluororesin fine particle aqueous dispersion changes, and at the same time, depending on the metal oxide sol used, precipitation occurs or gelation occurs due to the change in pH. Therefore, the pH of the fluororesin fine particle aqueous dispersion used for preparing the fluororesin-metal oxide mixed dispersion is generally preferably 10 or more, although it depends on the metal oxide sol used.

  The aggregation / aggregation of fine particles is closely related to the concentration. When the concentration is high, not only thickening and coagulation / gelation are likely to occur, but also aggregation and precipitation are likely to occur. Therefore, solvent dilution that is usually performed is also effective. However, if diluted too much, that is, if the particle concentration is too low, it is uneconomical because it consumes a great deal of energy for the evaporation and scattering of the solvent in the spraying / drying process. preferable. From this viewpoint, as described above, the fluororesin fine particles are 1 to 500 times, preferably 3 to 100 times, and water is preferably 5 to 200 times, by weight with respect to the content of the metal oxide fine particles in the whole liquid. It is desirable to be in the range of 10 to 120 times.

<About raw materials>
The aqueous fluororesin fine particle dispersion used in the present invention may be a commercially available product, for example, 31-JR (PTFE solid content: 60% by weight, average molecular weight: 2 × 10 ⁴ to 1 × 10 ⁷ , PTFE primary particles, manufactured by Mitsui Fluoro. Average particle size: 0.25 μm, pH: 10.5), manufactured by Daikin, polyflon D-111 (PTFE solid content: 60% by weight, average molecular weight: 2 × 10 ⁴ to 1 × 10 ⁷ , average particle of PTFE primary particles Diameter: 0.25 μm, pH: 9.7), manufactured by Asahi Glass, AD911E (PTFE solid content: 60 wt%, average molecular weight: 2 × 10 ⁴ to 1 × 10 ⁷ , average particle size of PTFE primary particles: 0.25 μm PH: 10) may be used, but is not limited thereto.
As the metal oxide sol, Tynoch A-6 manufactured by Taki Chemical (TiO ₂ wt%: 6, average particle diameter nm: 10-20, pH: 11-13), Viral Zr-C20 (ZrO ₂ wt%: 20) , Average particle diameter nm: 20, pH: 7), viral Nb-G6000 (Nb ₂ O ₃ wt%: 6, average particle diameter nm: 15, pH: 8), viral Al-L7 (Al 2 O 3 wt%: 7, An average particle diameter nm: 5-10, pH: 8) may be used, but is not limited thereto.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by this Example.

[Example 1]
In Example 1, a fluororesin-metal oxide mixed solid was produced by mixing alumina sol as a metal oxide in an aqueous fluororesin fine particle dispersion.
The mass concentration and the number of atoms of the mixed solid are summarized in Table 1.

[Example 2]
In Example 2, a fluororesin-metal oxide mixed solid was prepared by mixing alumina sol as a metal oxide with niobium, which is a metal that can easily cause phase separation, in the fluororesin fine particle aqueous dispersion.
Table 2 summarizes the mass concentration and the number of atoms of the mixed solid.

As shown in FIG. 1, it can be understood that the fluororesin fine particles and the metal oxide fine particles are uniformly mixed and dispersed by using the method of the present invention.
Further, as shown in FIG. 2, in the mixing of the fluororesin fine particle aqueous dispersion and the metal oxide sol, even if the liquid-liquid phase separation occurs, the metal oxide fine particles can be obtained by spray-drying immediately after stirring at high speed. It can be seen that the fluororesin fine particles are uniformly mixed and dispersed. Therefore, it turns out that spray drying is a very important essential operation.

  According to the present invention, by mixing with an aqueous dispersion of fluororesin fine particles, metal oxide sols that are likely to be separated, or that are separated immediately when stirring is stopped, are vigorously stirred and immediately spray-dried, A powder in which fluororesin fine particles and metal oxide fine particles are uniformly mixed and dispersed can be obtained.

According to the present invention, the thermal expansion and charging of the fluororesin are suppressed, and since the water contact angle is small, the hydrophobicity is weakened and the wettability and adhesiveness are improved. It has become possible to increase the functionality and functionality of the resin surface. In addition, the incorporation of the metal oxide according to the present invention hardens the fluororesin and increases the heat resistance, and at the same time has the effect of becoming a scratch-resistant surface.

A powder in which each of titania, zirconia, lantana, ceria, tin oxide and alumina is uniformly mixed and dispersed in fluororesin fine particles by the method of the present invention is manufactured, and these films are pressure-bonded to a SUS film to form a coating film. It was confirmed that various liquids and sols were uniformly wetted and a good coating film was formed. On the other hand, in the conventional fluororesin film containing no metal oxide, all the sols tried were repelled. The surface of a conventional fluororesin alone is soft, so that it is easily scratched when it comes into contact with a hard material. When a molecular paint (which may be a molecular paint) was applied and dried, a very hard coating film was formed on the film surface, and the surface became very difficult to be damaged.

  The fluororesin-metal oxide mixed solid of the present invention is a fluororesin film, mold material, bulk fluororesin molded body, etc., which has improved / adjusted physical properties of conventional fluororesins, specifically wettability, adhesiveness, heat resistance Therefore, it is suitable for the production of a fluororesin that requires these characteristics and a molded product thereof. In addition, since the powder and film according to the present invention have the above-mentioned characteristics, as a surface coating material or lining having good adhesion and high heat resistance and high degree, specifically, an electric wire, a thermometer, various sensors, a gasket, In addition to being used as a coating film and lining for various materials and product surfaces such as packing, it exhibits extremely excellent performance as an undercoating material in multi-layer and multi-stage coating for multi-function and high-function.

Claims (6)

A fluororesin-metal oxide mixed solid in which fluorine resin fine particles having a particle size of 100 to 500 nm and one or more metal oxide fine particles having a particle size of 5 to 200 nm are uniformly mixed and dispersed. The fluororesin fine particles are resin fine particles comprising a polymer or copolymer of a monomer selected from tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, perfluoro (alkyl vinyl ether), vinylidene fluoride and vinyl fluoride, and 2. The fluororesin-metal oxide mixed solid according to claim 1, which has a molecular weight of 1 × 10 ⁴ to 1 × 10 ⁷ . The metal oxide is one or more metal oxides selected from alumina, titanium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, cerium oxide, iron oxide, tin oxide, and niobium oxide. The fluororesin-metal oxide mixed solid according to any one of the above. The fluororesin-metal according to any one of claims 1 to 3, wherein a fluororesin content in the fluororesin-metal oxide mixed solid is 3 to 100 times the metal oxide content by weight. Oxide mixed solid. The aqueous dispersion of fluororesin fine particles and the metal oxide fine particle sol are used at a temperature of 5 to 300 ° C. under normal pressure, and the fluororesin fine particles are added 3 to 100 times in weight ratio to the content of the metal oxide fine particles in the liquid A step of obtaining a homogeneous mixed dispersion by mixing water at 10 to 120 times, further adding a surfactant or without adding a surfactant,
A step of producing a uniformly mixed powder by spray-drying the uniformly mixed dispersion liquid, wherein the fluororesin-metal oxide mixed solid according to any one of claims 1 to 4 is used. Production method. The method for producing the fluororesin-metal oxide mixed solid from the uniformly mixed powder is selected from the group consisting of a doctor blade method, pressurization, pressurization / heating, melting, and a combination of these and extrusion or stretching operations. The manufacturing method of the fluororesin-metal oxide mixed solid of Claim 5 characterized by including the processing process which comprises.

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