JP2022015560A - Method of producing dispersion and dispersion - Google Patents

Abstract

To provide a method for producing a dispersion containing a powder of a tetrafluoroethylene-based polymer and a liquid compound having a low surface tension and to provide a dispersion containing a powder of a tetrafluoroethylene-based polymer, a liquid compound and a liquid solvent.SOLUTION: There are provided: a method for producing a dispersion in which a mixture is obtained by mixing a powder of a tetrafluoroethylene-based polymer and a liquid compound having a surface tension of 30 mN/m or less and then the mixture and a liquid solvent is mixed; and a dispersion having a solid content of 25 mass% or more which contains a liquid compound containing a powder of a tetrafluoroethylene-based polymer, a liquid compound which is at least one selected from the group consisting of an alcohol and a ketone and has a surface tension of 30 mN/m or less and a liquid solvent which is at least one selected from the group consisting of an amide and hydrocarbon and has a surface tension of 20 mN/m or more and 50 mN/m or less or water.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a dispersion containing a tetrafluoroethylene polymer powder and a dispersion containing a tetrafluoroethylene polymer powder.

The tetrafluoroethylene polymer has excellent physical properties such as electrical insulation, water and oil repellency, chemical resistance, and heat resistance, and the dispersion liquid in which the powder is dispersed in water or an oil solvent is a resist, an adhesive, etc. It is useful as a material for forming an electrically insulating layer, a lubricant, an ink, a paint, and the like. However, since the surface energy of the tetrafluoroethylene polymer is low and the powders tend to aggregate with each other, it is difficult to obtain a dispersion liquid having excellent dispersion stability.
Patent Document 1 discloses a non-aqueous dispersion of a tetrafluoroethylene polymer powder.

International Publication No. 2019/1653525

However, the dispersion liquid described in Patent Document 1 is not yet sufficient in terms of dispersion stability.
Further, the dispersion of Patent Document 1 is limited to non-aqueous dispersions.

The present inventors have studied a method for producing such a dispersion liquid in order to obtain a dispersion liquid containing a tetrafluoroethylene polymer powder and having excellent dispersion stability, and have completed the present invention.

An object of the present invention is to provide a method for producing a dispersion liquid containing a tetrafluoroethylene polymer powder and a liquid compound having a low surface tension, and a dispersion liquid containing a tetrafluoroethylene polymer powder, a liquid compound and a liquid dispersion medium. And.

The present invention has the following aspects.
[1]
A method for producing a dispersion, in which a powder of a tetrafluoroethylene polymer and a liquid compound having a surface tension of 30 mN / m or less are mixed to obtain a mixture, and the mixture and a liquid dispersion medium are mixed.
[2]
The method for producing a dispersion liquid according to the above [1], wherein the liquid compound is 100 parts by mass or less with respect to 100 parts by mass of the powder of the tetrafluoroethylene polymer.
[3]
The method for producing a dispersion liquid according to the above [1] or [2], wherein the liquid dispersion medium exceeds 100 parts by mass with respect to 100 parts by mass of the powder of the tetrafluoroethylene polymer.
[4]
The method for producing a dispersion according to any one of the above [1] to [3], wherein the liquid compound is at least one liquid compound selected from the group consisting of alcohols and ketones.
[5]
The method for producing a dispersion according to any one of the above [1] to [4], wherein the liquid dispersion medium is at least one liquid dispersion medium selected from the group consisting of water, amides and hydrocarbons.
[6]
The method for producing a dispersion liquid according to any one of the above [1] to [5], wherein the mixture is further kneaded and then mixed with the liquid dispersion medium.
[7]
The method for producing a dispersion liquid according to any one of the above [1] to [6], wherein at least one selected from the group consisting of an inorganic filler and an aromatic polymer is further mixed.
[8]
The method for producing a dispersion liquid according to any one of the above [1] to [7], wherein a fluorine-based surfactant is substantially not added.
[9]
Production of the dispersion liquid according to any one of the above [1] to [8], wherein the tetrafluoroethylene polymer is a tetrafluoroethylene polymer containing a unit based on perfluoro (alkyl vinyl ether) or a unit based on hexafluoropropylene. Method.
[10]
The method for producing a dispersion liquid according to any one of the above [1] to [9], wherein the tetrafluoroethylene polymer is a tetrafluoroethylene polymer having an oxygen-containing atomic group.
[11]
At least one selected from the group consisting of tetrafluoroethylene polymer powder, alcohol and ketone, and at least one selected from the group consisting of liquid compounds having a surface tension of 30 mN / m or less, and amides and hydrocarbons. A dispersion liquid containing a liquid dispersion medium or water having a surface tension of 20 mN / m or more and 50 mN / m or less and having a solid content of 25% by mass or more.
[12]
The dispersion according to the above [11], which comprises at least one selected from the group consisting of an inorganic filler and an aromatic polymer.
[13]
The dispersion liquid according to the above [11] or [12], which has a solid content of 50% by mass or more.
[14]
The dispersion according to any one of the above [11] to [13], which has a viscosity of 1000 to 100,000 mPa · s.
[15]
The dispersion according to any one of [11] to [14] above, which does not substantially contain a fluorine-based surfactant.

According to the present invention, a dispersion liquid containing a tetrafluoroethylene polymer powder and having excellent dispersion stability can be produced. Further, the dispersion liquid of the present invention has improved dispersibility and is excellent in dispersion stability.

The following terms have the following meanings.
The "tetrafluoroethylene-based polymer" is a polymer containing a unit based on tetrafluoroethylene, and is also simply referred to as "F polymer".
The "glass transition point (Tg) of the polymer" is a value measured by analyzing the polymer by the dynamic viscoelasticity measurement (DMA) method.
The “polymer melting temperature (melting point)” is the temperature corresponding to the maximum value of the melting peak measured by the differential scanning calorimetry (DSC) method.
“D50” is the average particle diameter of the particles, which is the volume-based cumulative 50% diameter of the particles obtained by the laser diffraction / scattering method. That is, the particle size distribution of the particles is measured by the laser diffraction / scattering method, the cumulative curve is obtained with the total volume of the particle population as 100%, and the particle size is the point where the cumulative volume is 50% on the cumulative curve.
“D90” is the cumulative volume particle size of the particles, and is the volume-based cumulative 90% diameter of the particles obtained in the same manner as in “D50”.
The "viscosity of the dispersion liquid" is a value measured for the powder dispersion liquid at room temperature (25 ° C.) and a rotation speed of 30 rpm using a B-type viscometer. The measurement is repeated 3 times, and the average value of the measured values for 3 times is used.
The "monomer-based unit" means an atomic group based on the monomer formed by polymerization of the monomer. The unit may be a unit directly formed by a polymerization reaction, or may be a unit in which a part of the unit is converted into another structure by processing a polymer. Hereinafter, the unit based on the monomer a is also simply referred to as “monomer a unit”.

The production method of the present invention (hereinafter, also referred to as this method) is an F polymer powder (hereinafter, also referred to as this powder) and a liquid compound having a surface tension of 30 mN / m or less (hereinafter, also referred to as liquid compound (1)). Is mixed to obtain a mixture, and the mixture is mixed with a liquid dispersion medium (hereinafter, also referred to as liquid dispersion medium (1)) to obtain a dispersion liquid (hereinafter, also referred to as main dispersion liquid (1)). .. The present dispersion liquid (1) is a dispersion liquid in which the present powder is dispersed in the form of particles.
Further, the dispersion liquid of the present invention (hereinafter, also referred to as the present dispersion liquid (2)) is at least one selected from the group consisting of the present powder, alcohol and ketone, and is a liquid compound having a surface tension of 30 mN / m or less. A liquid dispersion medium or water (hereinafter, also referred to as liquid compound (2)), which is at least one selected from the group consisting of amides and hydrocarbons and has a surface tension of 20 mN / m or more and 50 mN / m or less (hereinafter, also referred to as liquid compound (2)). Both are collectively referred to as a liquid dispersion medium (2)), and is a dispersion having a solid content of 25% by mass or more. The present dispersion liquid (2) is a dispersion liquid in which the present powder is dispersed in the form of particles.

According to this method, a dispersion liquid containing a tetrafluoroethylene polymer powder having excellent dispersion stability and handleability can be obtained. Further, from the present dispersion liquid (1) and the present dispersion liquid (2), it is possible to easily form a molded product having excellent physical properties based on a tetrafluoroethylene polymer such as electrical properties and coating film physical properties such as surface smoothness. ..
The reason is not always clear, but the mixing enhances the affinity between the F polymer having a low surface tension and the liquid compound (1) having a low surface tension, and a highly wet F powder is formed. It is considered that the aggregation of the F powder in the mixing with 1) was suppressed, and the dispersion stability and handleability of the present dispersion liquid (1) were improved.

The F polymer in this method is a polymer containing a unit (hereinafter, also referred to as TFE unit) based on tetrafluoroethylene (hereinafter, also referred to as TFE).
The fluorine content of the F polymer is preferably 70 to 76% by mass. The F polymer having a high fluorine content is excellent in physical properties such as electrical properties of the F polymer, but has a low surface tension, so that it has a low affinity with a dispersion medium. Therefore, when the dispersion is prepared, its dispersibility is further lowered. According to this method, even in such a dispersion liquid, the physical properties of the entire F polymer are not impaired, and a dispersion liquid having excellent dispersibility can be obtained.

The melting temperature of the F polymer is preferably 180 ° C. or higher, more preferably 200 ° C. or higher, and even more preferably 260 ° C. or higher. The melting temperature of the F polymer is preferably 325 ° C or lower, more preferably 320 ° C or lower. The melting temperature of the F polymer is particularly preferably 180 ° C. or higher and 325 ° C. or lower.
The glass transition point of the F polymer is preferably 50 ° C. or higher, more preferably 75 ° C. or higher. The glass transition point of the F polymer is preferably 150 ° C. or lower, more preferably 125 ° C. or lower.

F-polymers are based on polytetrafluoroethylene (PTFE), polymers containing TFE units and ethylene-based units, polymers containing TFE units and propylene-based units, TFE units and perfluoro (alkyl vinyl ether) (PAVE). Polymers containing units (PAVE units) (PFA), polymers containing TFE units and units based on hexafluoropropylene (FEP), polymers containing TFE units and units based on fluoroalkylethylene, TFE units and chlorotrifluoro Examples include polymers containing ethylene-based units, with PFA or FEP being preferred, with PFA being more preferred. The polymer may further contain units based on other comonomeres.
As the PAVE, CF ₂ = CFOCF ₃ , CF ₂ = CFOCF ₂ CF ₃ or CF ₂ = CFOCF ₂ CF ₂ CF ₃ (hereinafter, also referred to as PPVE) is preferable, and PPVE is more preferable.

The F polymer preferably has an atomic group containing an oxygen atom. The F polymer based on such an atomic group has excellent physical properties, and according to this method, a dispersion liquid having excellent dispersion stability can be obtained, which can sufficiently express the physical properties of the F polymer.
The atomic group may be contained in the monomer unit in the F polymer, or may be contained in the terminal group of the main chain of the polymer. Examples of the latter aspect include an F polymer having the atomic group as a terminal group derived from a polymerization initiator, a chain transfer agent, or the like.
The atomic group containing an oxygen atom is preferably a hydroxyl group-containing group or a carbonyl group-containing group, and a carbonyl group-containing group is particularly preferable.

The hydroxyl group-containing group is preferably a group containing an alcoholic hydroxyl group, more preferably -CF ₂ CH ₂ OH or -C (CF ₃ ) ₂ OH.
The carbonyl group-containing group is a group containing a carbonyl group (> C (O)), a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC (O) NH ₂ ), and an acid anhydride residue. Group (-C (O) OC (O)-), imide residue (-C (O) NHC (O)-etc.) or carbonate group (-OC (O) O-) is preferred, and acid anhydride residue. Is more preferable.

Suitable embodiments of the F polymer include a polymer (1) containing TFE units and PAVE units and having atomic groups containing oxygen atoms, or TFE units and PAVE units, with 2 PAVE units for all monomer units. Examples thereof include the polymer (2) containing 0.0 to 5.0 mol% and having no atomic group containing oxygen atoms. Since these polymers form microspherulites in the molded product, the characteristics of the molded product are likely to be improved.

The polymer (1) is preferably a polymer containing a TFE unit, a PAVE unit, and a monomer having a hydroxyl group-containing group or a carbonyl group-containing group. The polymer (1) has 90 to 99 mol% of TFE units, 0.5 to 9.97 mol% of PAVE units, and 0.01 to 3 mol% of units based on the above-mentioned monomers, respectively, with respect to all the units. It is preferable to include it. The monomer is preferably itaconic anhydride, citraconic anhydride or 5-norbornen-2,3-dicarboxylic acid anhydride (also known as hymic anhydride; hereinafter also referred to as "NAH").
Specific examples of the polymer (1) include the polymers described in International Publication No. 2018/16644.

The polymer (2) consists of only TFE units and PAVE units, and contains 95.0 to 98.0 mol% of TFE units and 2.0 to 5.0 mol% of PAVE units with respect to all the monomer units. Is preferable.
The content of PAVE units in the polymer (2) is preferably 2.1 mol% or more, more preferably 2.2 mol% or more, based on all the monomer units.
The fact that the polymer (2) does not have an atomic group containing an oxygen atom means that the atomic group containing an oxygen atom contained in the polymer has a ratio of 1 × 10 ⁶ carbon atoms constituting the polymer main chain. It means that the number is less than 500. The number of atomic groups containing oxygen atoms is preferably 100 or less, more preferably less than 50. The lower limit of the number of atomic groups containing oxygen atoms is usually zero.

The polymer (2) may be produced by using a polymerization initiator, a chain transfer agent, or the like that does not generate an atomic group containing an oxygen atom as a terminal group of the polymer chain, and may be an F polymer having an atomic group containing an oxygen atom. It may be manufactured by fluorination treatment. Examples of the fluorination treatment method include a method using fluorine gas (see JP-A-2019-194314).

This powder is a powder containing an F polymer, and the amount of the F polymer in the powder is preferably 80% by mass or more, more preferably 100% by mass.
The D50 of this powder is preferably 20 μm or less, more preferably 8 μm or less. The D50 of this powder is preferably 0.1 μm or more, more preferably 0.3 μm or more. Further, the D90 of this powder is more preferably 50 μm or less. If D50 and D90 of the present powder are in such a range, the surface area thereof becomes large, and the dispersibility of the present powder is likely to be further improved.

This powder may contain other resins or inorganic substances different from the F polymer.
Examples of other resins include aromatic polymer varnishes. Examples of the aromatic polymer include aromatic polyimides, aromatic maleimides, aromatic elastomers such as styrene elastomers, and aromatic polyamic acids.
Examples of inorganic substances are oxides, nitrides, simple metals, alloys and carbons, preferably silicon oxide (silica) and metal oxides (beryllium oxide, cerium oxide, alumina, soda alumina, magnesium oxide, zinc oxide and titanium oxide. Etc.), boron nitride, and magnesium metasilicate (steatite), and silica and boron nitride are preferable, and silica is more preferable.
This powder containing another resin or inorganic substance preferably has an F polymer as a core and another resin or inorganic substance in the shell.

The liquid compound (1) is a liquid compound having a surface tension of 30 mN / m or less. The liquid compound (1) is a compound having a viscosity of 10 mPa · s or less at 25 ° C. (hereinafter, “liquid” means a state having a viscosity of 10 mPa · s or less at 25 ° C.).
The surface tension can be measured by, for example, a surface tension meter. A method of measuring by the Wilhelmy method at 25 ° C. using a surface tension meter can be mentioned.

The surface tension of the liquid compound (1) is preferably 28 mN / m or less, more preferably 25 mN / m or less. The surface tension of the liquid compound (1) is preferably 10 mN / m or more.
Examples of the liquid compound (1) include alcohols, esters, ketones, ethers, and hydrocarbons having a surface tension of 30 mN / m or less. These may or may not be fluorinated. As the alcohol, methanol, ethanol, isopropanol, butanol and hexanol are preferable. As the hydrocarbon, pentane, hexane, heptane, octane, toluene and xylene are preferable. As the ketone, acetone, methyl ethyl ketone, diisobutyl ketone and methyl isobutyl ketone are preferable. As the ester, ethyl acetate, butyl acetate, ethyl benzoate, and butyl benzoate are preferable.
Among these compounds, at least one selected from the group consisting of alcohols and ketones is more preferable, and isopropanol or methyl ethyl ketone is even more preferable.
The liquid compound (1) may be one kind or a mixture of two or more kinds. The liquid compound (1) is preferably degassed from the viewpoint of reducing the uniformity of the component distribution of the molded product obtained by using the present dispersion (1) and suppressing voids.

In this method, the powder and the liquid compound (1) are mixed to obtain a mixture.
The mixing ratio of the powder and the liquid compound (1) is preferably 100 parts by mass or less with respect to 100 parts by mass of the powder. By mixing the liquid compound (1) having a mass smaller than that of the present powder, the surface of the present powder is wetted by the liquid compound (1), and when mixed with the liquid dispersion medium (1) described later, the dispersion stability is further improved. An excellent dispersion can be obtained.
The mixing ratio of the powder and the liquid compound (1) is more preferably 80 parts by mass or less, still more preferably 40 parts by mass or less, based on 100 parts by mass of the powder.
Further, the mixing ratio of the present powder and the liquid compound (1) is more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, based on 100 parts by mass of the present powder.

Examples of the method of mixing the present powder and the liquid compound (1) include a method of mixing the present powder and the liquid compound (1) together, and a method of mixing the present powder while sequentially adding the liquid compound (1). For example, a method of collectively adding and mixing the present powder to the liquid compound (1), a method of mixing the liquid compound (1) while continuously or intermittently adding the present powder, and the like can be mentioned.
Examples of the mixer used for mixing include a mixer with a stirring blade, a Henshell mixer, a ribbon blender, a swing type mixer, and a vibration type mixer.

The obtained mixture may be further kneaded to obtain a uniform liquid composition. The kneading may be performed after the mixing, or the mixing and kneading may be performed at the same time.
When kneading, it is preferable to knead in a closed system. It is preferable to knead the liquid compound (1) so that the liquid component does not evaporate during kneading. As a result, the present powder and the liquid compound (1) are uniformly kneaded to obtain a highly defoamed mixture.
When kneading, it is preferable to use a kneader equipped with a stirring tank and a uniaxial or multiaxial stirring blade. The number of stirring blades is preferably two or more in order to obtain a high kneading action. The kneading method may be either a batch method or a continuous method.

As the kneader used for the batch type kneading, a Henschel mixer, a pressurized kneader, a Banbury mixer or a planetary mixer is preferable, and a planetary mixer is more preferable. The planetary mixer has a biaxial stirring blade that rotates and revolves with each other, and has a structure for stirring and kneading the kneaded material in the stirring tank. Therefore, there is little dead space in the stirring tank where the stirring blades do not reach, the load on the blades can be reduced, and the liquid composition can be highly kneaded. Further, after the kneading is completed, the dispersion medium can be added as it is to the obtained mixture to produce the dispersion liquid as it is.

The mixture obtained by mixing the present powder and the liquid compound (1) and the liquid dispersion medium (1) are mixed to obtain the present dispersion liquid (1).
The liquid dispersion medium (1) is a dispersion medium having a viscosity of 10 mPa · s or less at 25 ° C., similar to the liquid compound (1).

The liquid dispersion medium (1) may be the same as or different from the liquid compound (1). The liquid dispersion medium (1) is preferably different from the liquid compound (1). The liquid dispersion medium (1) may be one kind or a mixed dispersion medium of two or more kinds. The liquid dispersion medium (1) is preferably degassed from the viewpoint of reducing the uniformity of the component distribution of the molded product obtained by using the present dispersion (1) and suppressing voids.

The liquid dispersion medium (1) used is a dispersion medium that does not react with the F polymer. The boiling point of the liquid dispersion medium (1) is preferably 75 ° C. or higher, more preferably 100 ° C. or higher. The boiling point of the liquid dispersion medium (1) is preferably 300 ° C. or lower, more preferably 250 ° C. or lower.
The liquid dispersion medium (1) may be water or a non-aqueous dispersion medium. Examples of the non-aqueous dispersion medium include amides, ketones, esters, hydrocarbons, glycols, glycol ethers and glycol acetates, and more specifically, N-methyl-2-pyrrolidone, γ-butyrolactone, cyclohexanone and cyclopentanone. , Glycol monoalkyl ether, glycol monoaryl ether, glycol monoalkyl ether acetate or glycol monoaryl ether acetate.
As the liquid dispersion medium (1), water, amide, ketone and hydrocarbon are preferable, and water, N-methyl-2-pyrrolidone, toluene and dimethylacetamide are more preferable. The liquid dispersion medium (1) may be used alone or as a mixture of two or more kinds.

The surface tension of the liquid dispersion medium (1) is preferably 20 mN / m or more, more preferably 30 mN / m or more, preferably 100 mN / m or less, more preferably 80 mN / m or less, still more preferably 50 mN / m or less. In such a case, the present dispersion (1) tends to have excellent blendability with the third component described later.
When the liquid compound (1) is protonic, it is preferable that the liquid dispersion medium (1) is also protonic. In this case, the surface tension of the liquid dispersion medium (1) is preferably 50 to 100 mN / m.
When the liquid compound (1) is aprotic, it is preferable that the liquid dispersion medium (1) is also aprotic. In this case, the surface tension of the liquid dispersion medium (1) is preferably 20 to 60 mN / m.

The mixing ratio of the powder and the liquid dispersion medium (1) is preferably more than 100 parts by mass with respect to 100 parts by mass of the powder. By mixing the present liquid dispersion medium (1) having a mass larger than that of the present powder, the present powder whose surface is wetted with the liquid compound (1) can obtain a dispersion liquid having more excellent dispersion stability.
The mixing ratio of the powder and the liquid dispersion medium (1) is more preferably 120 parts by mass or more, and further preferably 130 parts by mass or more, with respect to 100 parts by mass of the present powder.
The mixing ratio of the powder and the liquid dispersion medium (1) is more preferably 1000 parts by mass or less, and further preferably 300 parts by mass or less, with respect to 100 parts by mass of the present powder.

Mixing of the mixture with the liquid dispersion medium (1) is carried out by using an ultrasonic homogenized baint shaker, a ball mill, an attritor, a basket mill, a sand mill, etc. from the viewpoint of dispersibility and dispersion stability of the obtained dispersion liquid (1). Dispersers that use media such as sand grinders, dyno mills, dispermats, SC mills, spike mills or agitator mills, and dispersers that do not use media such as ultrasonic homogenizers, nanomizers, resolvers, dispersers, and high-speed impeller dispersers. Is preferable, and it is more preferable to use a disperser using a medium.

Further, since the dispersion stability is improved by mixing using a collision type disperser, it is preferable to use a collision type disperser. The collision-type disperser is a disperser that collides the pressurized dispersion medium with the mixture and disperses the mixture by its impact force or the like. As such a disperser, either a disperser in which the mixture and the dispersion medium are pressurized and collided with each other, or a disperser in which the dispersant medium pressurized with the mixture is collided with each other may be used. Examples of the former disperser include a nanomizer, Genus PY, an ultimateizer, Aqua, and a microfluidizer, and examples of the latter disperser include a homogenizer.

Further, as a method of mixing the mixture and the liquid dispersion medium (1), the same method as the above-mentioned mixing method of the present powder and the liquid compound (1) can be mentioned. When the powder and the liquid compound (1) are mixed and then further kneaded, the mixture may be taken out from the kneader and mixed with the liquid dispersion medium (1), or the liquid dispersion medium may be placed in the kneader. (1) may be added, and subsequently, the mixture and the liquid dispersion medium (1) may be mixed.

Since the surface energy of the F polymer is low and the powders tend to aggregate with each other, a fluorine-based surfactant may be generally added to the dispersion liquid in order to improve the dispersibility. The fluorine-based surfactant means a compound having a hydroxyl group, a carboxyl group, a sulfo group, a hydrophilic moiety having a group derived from these groups, and a hydrophobic moiety having a fluorine-containing organic group.
According to this method, even if such a fluorine-based surfactant is mixed with the liquid dispersion medium (1) without substantially adding it, the dispersibility is not impaired and the dispersion stability is excellent. (1) is obtained.
The fact that the fluorine-based surfactant is not substantially added means that the concentration of the fluorine-based surfactant in the dispersion liquid does not exceed 1% by mass, and fluorine in the obtained dispersion liquid is not added. The amount of the system-based surfactant is 1% by mass or less, and the amount of the fluorine-based surfactant is preferably 0.5% by mass or less, more preferably 0% by mass.

In this method, the temperature of the mixing of the powder and the liquid compound (1) and the mixing of the mixture and the liquid dispersion medium (1) is not particularly limited as long as the powder is uniformly dispersed, but is usually used. It is carried out at 20 ° C. or higher. Further, the mixing is carried out at a temperature lower than the lower boiling point of the liquid compound (1) or the liquid dispersion medium (1), and it is preferable to carry out the mixing at 100 ° C. or lower.

In this method, at least one selected from the group consisting of an inorganic filler and an aromatic polymer (hereinafter, also referred to as a third component) may be further mixed.
When the inorganic filler is mixed, the molded product formed from the present dispersion liquid (1) tends to be excellent in electrical characteristics and low linear expansion.
When the aromatic polymer is mixed, the molded product formed from the present dispersion (1) tends to have excellent adhesiveness and UV processability.
From the above viewpoint, the inorganic filler is preferably a nitride filler or an inorganic oxide filler, and is preferably a boron nitride filler, an aluminum nitride filler, a beryllia filler (a filler of an oxide of berylium), a silica filler, a wollastonite filler, or a talc filler. A silicate filler such as, or a metal oxide filler such as cerium oxide, aluminum oxide, magnesium oxide, zinc oxide, titanium oxide and the like is more preferable, and a silica filler is further preferable.
The inorganic filler is preferably surface-treated with a silane coupling agent.

The D50 of the inorganic filler is preferably 20 μm or less, more preferably 10 μm or less. The D50 is preferably 0.01 μm or more, more preferably 0.1 μm or more.
The shape of the inorganic filler may be granular, needle-shaped (fibrous), or plate-shaped. Specific shapes of the inorganic filler include spherical, scaly, layered, leafy, apricot kernel, columnar, chicken crown, equiaxed, leafy, mica, block, flat plate, wedge, rosette, and mesh. The shape and the prismatic shape can be mentioned.

Suitable specific examples of the inorganic filler are silica filler (“Admafine (registered trademark)” series manufactured by Admatex Co., Ltd.), zinc oxide surface-treated with an ester such as propylene glycol dicaprate (Sakai Chemical Industry Co., Ltd.). "FINEX (registered trademark)" series, etc.), spherical fused silica ("SFP (registered trademark)" series, etc. manufactured by Denka Co., Ltd.), titanium oxide coated with polyhydric alcohol and inorganic substances (manufactured by Ishihara Sangyo Co., Ltd.) "Typake (registered trademark)" series, etc.), rutile-type titanium oxide surface-treated with alkylsilane ("JMT (registered trademark)" series manufactured by Teika, etc.), hollow silica filler ("E" manufactured by Pacific Cement Co., Ltd.) -SPHERES "series, Nittetsu Mining Co., Ltd." Sirinax "series, Emerson & Cumming Co., Ltd." Ecocos Fire "series, etc.), Tarkufiller (Nippon Tarku Co., Ltd." SG "series, etc.), Steatite Filler (Steatite Filler) "BST" series manufactured by Nippon Tark Co., Ltd.), boron nitride filler ("UHP" series manufactured by Showa Denko Co., Ltd., "Denka Boron Night Ride" series manufactured by Denka Co., Ltd. ("GP", "HGP" grade), etc.) Can be mentioned.

The aromatic polymer is preferably an aromatic elastomer such as aromatic polyimide, aromatic maleimide, or styrene elastomer or an aromatic polyamic acid, with aromatic elastomers such as aromatic polyimide, aromatic maleimide, polyphenylene ether, and styrene elastomer being more preferable. Preferred, aromatic polyimides or aromatic polyamic acids are even more preferred. The aromatic polyimide may be thermoplastic or thermosetting. The thermoplastic polyimide means a polyimide that has been imidized and does not undergo a further imidization reaction.

Specific examples of aromatic polyimides include "Neoprim (registered trademark)" series (manufactured by Mitsubishi Gas Chemical Company), "Spixeria (registered trademark)" series (manufactured by Somar), and "Q-PILON (registered trademark)" series ( PI Technology Research Institute), "WINGO" series (Wingo Technology), "Toamide (registered trademark)" series (T & K TOKA), "KPI-MX" series (Kawamura Sangyo), "Yupia (" Registered trademark) -AT "series (manufactured by Ube Industries, Ltd.) can be mentioned.

Examples of the styrene elastomer include styrene-butadiene copolymer, hydrogenated-styrene-butadiene copolymer, hydrogenated-styrene-isoprene copolymer, styrene-butadiene-styrene block copolymer, and styrene-isoprene-styrene block copolymer. Examples thereof include a hydrogenated product of a styrene-butadiene-styrene block copolymer, a hydrogenated product of a styrene-isoprene-styrene block copolymer, and the like.

When the third component is mixed, the mixing method may be the same as the above-mentioned mixing method of the present powder and the liquid compound (1).
When the third component is mixed, the third component may be added at any stage of this method. For example, the third component may be mixed with the present powder and / or the liquid compound (1) in advance, or the third component may be added when the present powder and the liquid compound (1) are mixed. .. Further, when the mixture and the liquid dispersion medium (1) are mixed, the third component may be added and mixed together, or the third component may be added to the dispersion after obtaining the dispersion. The addition may be performed in a batch or in a divided manner, or may be added continuously or intermittently.

Further, in this method, a surfactant other than the fluorine-based surfactant may be added from the viewpoint of further improving the dispersion stability and the handleability. Surfactants other than fluorine-based surfactants are preferably nonionic.
The hydrophilic moiety of the surfactant other than the fluorine-based surfactant preferably has an oxyalkylene group or an alcoholic hydroxyl group.
The oxyalkylene group may be composed of one kind or two or more kinds. In the latter case, different types of oxyalkylene groups may be randomly arranged or may be arranged in blocks.
The oxyalkylene group is preferably an oxyethylene group.

The hydrophobic moiety of the surfactant other than the fluorine-based surfactant preferably has an acetylene group and a polysiloxane group. In other words, the surfactant is preferably an acetylene-based surfactant or a silicone-based surfactant.
When a surfactant other than the fluorine-based surfactant is contained, the content in the dispersion obtained by this method is preferably 1 to 15% by mass. In this case, the affinity between the components is increased, and the dispersion stability of the dispersion obtained by this method is likely to be further improved.

In this method, the thermosetting resin may be further mixed. When mixing the thermosetting resin, it is preferable to further mix the aluminum nitride filler. The molded product formed from the present dispersion liquid (1) further containing the thermosetting resin and the aluminum nitride filler is likely to be excellent in heat dissipation and low water absorption. Examples of the thermosetting resin include a thermosetting polyimide, a polyimide precursor, an epoxy resin, a thermosetting acrylic resin, a bismaleimide resin, and a thermosetting polyphenylene ether resin.

The present dispersion liquid (1) obtained by this method is in a liquid state containing the present powder, the liquid compound (1) and the liquid dispersion medium (1).
The solid content of the dispersion liquid (1) contains the powder, and when the third component is contained, these third components are also included in the solid content. The solid content of the dispersion liquid also includes other insoluble components in the main dispersion liquid (1) other than the present powder. The concentration of the solid content is preferably 25% by mass or more, more preferably 50% by mass or more, with the total mass of the dispersion liquid being 100% by mass. Further, from the viewpoint of dispersibility of the present dispersion liquid (1), the solid content concentration is preferably 80% by mass or less, more preferably 60% by mass or less. The amount of the present powder in the solid content is preferably 50% by mass or more, more preferably 70% by mass or more, with the total mass of the solid content being 100% by mass. The amount of this powder in the solid content is preferably 99% by mass or less.

Further, in this method, the present dispersion liquid (2) is obtained by using the liquid compound (2) as the liquid compound and the liquid dispersion medium (2) as the liquid dispersion medium and setting the solid content to 25% by mass. The liquid compound (2) is at least one liquid compound selected from the group consisting of alcohols and ketones, and has a surface tension of 30 mN / m or less. The liquid dispersion medium (2) is at least one liquid dispersion medium or water selected from the group consisting of amides and hydrocarbons having a surface tension of 20 mN / m or more and 50 mN / m or less. The liquids of the liquid compound and the liquid dispersion medium are as described above. The liquid compound (2) may be used alone or as a mixture of two or more kinds. The liquid dispersion medium (2) may be used alone or as a mixture of two or more kinds.

The present dispersion (2) may contain the above-mentioned third component.
The solid content in the dispersion liquid (2) is the powder as described above, and when the above-mentioned third component or other insoluble other components in the dispersion liquid (2) is contained, the powder and the third component and It is the total amount with other insoluble components. The solid content can be controlled by adjusting the addition amount in this method so that the total mass of the dispersion liquid (2) is 100% by mass and the solid content is 25% by mass or more. The solid content is preferably 50% by mass or more.

The viscosity of the dispersion liquid (2) is preferably 1000 mPa · s or more, and more preferably 2500 mPa · s or more. The viscosity of the dispersion liquid (2) is preferably 100,000 mPa · s or less, more preferably 50,000 mPa · s. Even in such a highly viscous range, the dispersion liquid (2) is excellent in handleability.

The thixotropic ratio of the dispersion liquid (2) is preferably 1.0 to 2.2. The present dispersion (2) having such a thixotropic ratio is excellent in coatability and homogeneity. The thixotropic ratio is calculated by dividing the viscosity of the dispersion liquid (2) measured under the condition of a rotation speed of 30 rpm by the viscosity of the main dispersion liquid (2) measured under the condition of a rotation speed of 60 rpm. To.
From the viewpoint of reducing the uniformity of the component distribution of the molded product obtained from the present dispersion (2) and suppressing voids, the foam volume ratio in the present dispersion (2) is preferably less than 10%, preferably less than 5%. More preferred. The foam volume ratio is preferably 0% or more.
The foam volume ratio is measured by measuring the volume ( _VN ) of the present dispersion liquid (2) at standard atmospheric pressure and 20 ° C. and the combined volume ( _VV ) of the foam when the pressure is reduced to 0.003 MPa. However, it is a value obtained by the following formula.
Foam volume ratio [%] = 100 × ( _{VV −} VN) / _VN .

The present dispersion liquid (2) is a dispersion liquid having excellent dispersion stability without impairing the dispersibility even if it does not substantially contain a fluorine-based surfactant.
The fact that the fluorine-based surfactant is not substantially contained means that the amount of the fluorine-based surfactant in the dispersion liquid (2) is 1% by mass or less, as described above, and the fluorine-based surfactant is not substantially contained. The amount of the above is preferably 0.5% by mass or less, more preferably 0% by mass.

The present dispersion (1) or the present dispersion (2) (hereinafter, both are collectively referred to as the present dispersion) is applied to the surface of the base material and heated to obtain a layer made of an F polymer (hereinafter, "". By forming (also referred to as "F layer"), a laminate having a base material and an F layer can be produced. Preferable embodiments of the laminate include a metal-clad laminate having a metal foil and an F layer formed on at least one surface thereof, and a multilayer film having a resin film and an F layer formed on at least one surface thereof. Can be mentioned.
The metal foil in the metal-clad laminate is preferably a copper foil. Such a metal-clad laminate is particularly useful as a printed circuit board material.
The resin film in the multilayer film is preferably a polyimide film. Such a multilayer film is useful as an electric wire coating material and a printed circuit board material.

In the production of the laminate, the F layer may be formed on at least one side of the surface of the base material, the F layer may be formed on only one side of the base material, and the F layer is formed on both sides of the base material. You may. The surface of the base material may be surface-treated with a silane coupling agent or the like. When applying this dispersion, the spray method, roll coat method, spin coat method, gravure coat method, micro gravure coat method, gravure offset method, knife coat method, kiss coat method, bar coat method, die coat method, fountain Mayer bar method , The slot die coat method can be used.

The F layer is heated by heating to form the liquid compound (1) or the liquid compound (2) (hereinafter, both are collectively referred to as the present compound), and the liquid dispersion medium (1) or the liquid dispersion medium (2) (hereinafter, the present invention). It is preferable to form the polymer by further firing the polymer by heating after removing (also referred to as the present dispersion medium), both of which are collectively referred to as the present dispersion medium. The temperature for removing the compound and the dispersion medium is preferably a temperature equal to or lower than the boiling point of the compound or the dispersion medium, and more preferably 50 ° C. to 150 ° C. lower than the boiling point. For example, when N-methyl-2-pyrrolidone having a boiling point of about 200 ° C. is used, it is preferable to heat it at 150 ° C. or lower, preferably 100 to 120 ° C. It is preferable to blow air in the step of removing the dispersion medium.

After removing the compound and the dispersion medium, it is preferable to heat the substrate to a temperature range in which the polymer is fired, and it is preferable to fire the polymer in the range of, for example, 300 to 400 ° C. The F layer preferably contains a fired product of the F polymer.
The F layer is formed through the steps of applying, drying, and firing the present dispersion as described above. These steps may be performed once or twice or more. For example, the present dispersion liquid is applied, and the present dispersion medium is removed by heating to form a film. The present dispersion may be further applied on the formed film, the present dispersion medium may be removed by heating, and the F polymer may be further fired by heating to form the film. From the viewpoint of easily obtaining a thick film having excellent smoothness, the steps of applying, drying and firing the present dispersion may be performed twice.
The thickness of the F layer is preferably 0.1 μm or more, and more preferably 1 μm or more. The upper limit of the thickness is 200 μm. In this range, the F layer having excellent crack resistance can be easily formed.
The peel strength between the F layer and the base material layer is preferably 10 N / cm or more, more preferably 15 N / cm or more. The peel strength is preferably 100 N / cm or less. By using this dispersion, such a laminate can be easily formed without impairing the physical properties of the F polymer in the F layer.
The porosity of the F layer is preferably 20% or less, more preferably 10% or less. The porosity is preferably 0.1% or more. The void ratio is determined by image processing to determine the void portion of the F layer from the SEM photograph of the cross section of the molded product observed using a scanning electron microscope (SEM), and the area occupied by the void portion is the area occupied by the F layer. It is the ratio (%) divided by the area. The area occupied by the void portion is obtained by approximating the void portion to a circle.

The material of the base material is a metal substrate such as copper, nickel, aluminum, titanium, a metal foil such as an alloy thereof, polyimide, polyarylate, polysulfone, polyallyl sulfone, polyamide, polyetheramide, polyphenylene sulfide, polyallyl ether. Examples thereof include resin films such as ketones, polyamide-imides, liquid polyesters, and liquid polyester amides, and prepregs which are precursors of fiber-reinforced resin substrates. Examples of the shape of the base material include a planar shape, a curved surface shape, and an uneven shape, and may be any of a foil shape, a plate shape, a film shape, and a fibrous shape. Specific examples of the laminate include a metal foil, a metal-clad laminate having an F layer on at least one surface of the metal foil, a polyimide film, and a multilayer film having an F layer on both surfaces of the polyimide film. Be done. These laminated bodies are excellent in various physical properties such as electrical characteristics, and are suitable as a printed circuit board material or the like. Specifically, the laminated body can be used for manufacturing a flexible printed circuit board or a rigid printed circuit board.

The structure of the laminate of the F layer and the other base material is as follows: metal substrate / F layer / other base material layer / F layer / metal substrate, metal substrate layer / other base material layer / F layer / other base. Examples include a material layer / metal substrate layer. Each layer may further contain a glass cloth or filler.
Such laminates are useful as antenna parts, printed substrates, aircraft parts, automobile parts, sports equipment, food industry supplies, paints, cosmetics, etc., and specifically, wire coating materials (aircraft wires, etc.), Electrical insulating tape, insulating tape for oil drilling, material for printed substrate, separation membrane (precision filtration membrane, ultrafiltration membrane, reverse osmosis membrane, ion exchange membrane, dialysis membrane, gas separation membrane, etc.), electrode binder (lithium II) Covers for next batteries, fuel cells, etc.), copy rolls, furniture, automobile dashboards, home appliances, etc., sliding members (load bearings, sliding shafts, valves, bearings, gears, cams, belt conveyors, food transport belts, etc.) Etc.), tools (shovels, shavings, cuttings, saws, etc.), boilers, hoppers, pipes, ovens, baking molds, chutes, dies, toilets, container coverings.

By impregnating the woven fabric with this dispersion and drying it by heating, an impregnated woven fabric in which the F polymer is impregnated into the woven fabric can be obtained. The impregnated woven fabric can also be said to be a coated woven fabric in which the woven fabric is coated with the F layer. The woven fabric is preferably a glass fiber woven fabric, a carbon fiber woven fabric, an aramid fiber woven fabric or a metal fiber woven fabric, and more preferably a glass fiber woven fabric or a carbon fiber woven fabric. Examples of the method of impregnating the woven fabric with the present dispersion include a method of immersing the woven fabric in the present dispersion and a method of applying the present dispersion to the woven fabric.

When the fibers are impregnated with this dispersion and dried by heating, an impregnated fiber impregnated with the F polymer is obtained. Examples of the fiber include high-strength and low-elongation fibers such as carbon fiber, aramid fiber, and silicon carbide fiber.

As described above, according to this method, the present dispersion liquid (1) having excellent dispersibility and dispersion stability can be obtained. Further, in this method, the present liquid compound (2) is used as the liquid compound, and the liquid dispersion medium (2) is used as the liquid dispersion medium, and the solid content is 25% by mass or more, so that the present dispersion has excellent dispersibility and dispersion stability. Liquid (2) is obtained.

Although the present method and the present dispersion have been described above, the present invention is not limited to the configuration of the above-described embodiment.
For example, this method may additionally have any other step in the configuration of the embodiment, or may be replaced with any step that produces the same action. Further, in the configuration of the embodiment, the present dispersion may be added with any other configuration or may be replaced with any configuration exhibiting the same function.

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto.
1. 1. Preparation of each ingredient [F powder]
F powder 1: A powder (D50: 2.1 μm) containing 97.9 mol%, 0.1 mol%, and 2.0 mol% of TFE units, NAH units, and PPVE units in this order and having a polar functional group. )

[Aromatic polymer]
Varnish 1: Varnish in which thermoplastic aromatic polyimide (PI1) is dissolved in NMP [surfactant]
Surfactant 1: Triethylene glycol monomethyl ether [liquid compound]
IPA: Isopropanol (surface tension: 20 mN / m)
MEK: Methyl ethyl ketone (surface tension: 25 mN / m)
NMP: N-methyl-2-pyrrolidone (surface tension: 41 mN / m)
[Liquid dispersion medium]
IPA: Isopropanol (surface tension: 20 mN / m)
NMP: N-methyl-2-pyrrolidone (surface tension: 41 mN / m)
Water (surface tension: 72 mN / m)

2. 2. Dispersion Liquid Production Example [Example 1]
First, powder 1 and IPA as a liquid compound were put into a pot, and zirconia balls were put into the pot. Then, the pot was rolled at 150 rpm for 1 hour to prepare a mixture containing powder 1 (80 parts by mass) and IPA (20 parts by mass). Further, varnish 1 (10 parts by mass) and NMP (40 parts by mass) as a liquid dispersion medium were added, and the pot was rolled at 150 rpm for 1 hour, and powder 1 (40 parts by mass) and PI1 (2 parts by mass) IPA. A dispersion 1 (viscosity: 8000 mPa · s) containing (10 parts by mass) and NMP (48 parts by mass) was obtained. Of the 48 parts by mass of NMP in the dispersion liquid 1, 8 parts by mass is derived from varnish 1.

[Example 2 to Example 6]
Dispersions 2 to 6 were prepared in the same manner as the dispersion 1 except that the types of the liquid compound and the liquid dispersion medium were changed as shown in Table 1. In the dispersion liquid 5, 5 parts by mass of triethylene glycol monomethyl ether was added as a hydrocarbon-based surfactant, and 35 parts by mass of water was used instead of 40 parts by mass of NMP of Example 1.

The components of the dispersions 1 to 6 obtained above are summarized in Table 1. In addition, the results of evaluating the dispersions 1 to 6 according to the following evaluation criteria and the results of evaluating the molded products obtained from the respective dispersions by the following methods according to the following evaluation criteria are also summarized in Table 1.

3. 3. Production Example of Molded Product A wet film was formed by applying the dispersion liquid 1 to the surface of a long copper foil (thickness 18 μm) using a bar coater. Next, the metal foil on which the wet film was formed was passed through a drying oven at 120 ° C. for 5 minutes and dried by heating to obtain a dry film. Then, the dry membrane was heated at 380 ° C. for 3 minutes in a nitrogen oven. As a result, a laminate 1 having a metal foil and a polymer layer (thickness 5 μm) as a molded product containing a melt-fired product of F powder 1 and PI1 on the surface thereof was produced.
The laminates 2 to 6 were manufactured in the same manner as the laminate 1 except that the dispersion 1 was changed to each of the dispersions 2 to 6.

4. Evaluation 4-1. Evaluation of Dispersion Stability of Dispersions After storing each dispersion in a container at 25 ° C., the dispersibility was visually confirmed and the dispersion stability was evaluated according to the following criteria.

[Evaluation criteria]
〇: Aggregates are not visible.
X: Adhesion of fine agglomerates is visually recognized on the side wall of the container.

4-2. Evaluation of Surface Smoothness of Laminates The surface smoothness of each polymer layer was visually confirmed, and the surface smoothness was evaluated according to the following criteria.

[Evaluation criteria]
〇: The entire surface of the polymer layer is smooth.
Δ: Unevenness due to lack of agglomerates or powder is visible on the edge of the surface of the polymer layer.
X: Unevenness due to lack of agglomerates or powder is visible on the entire surface of the polymer layer.

As is clear from the above results, the present dispersion (1) and the present dispersion (2) prepared by this method are excellent in dispersibility and dispersion stability. It is considered that the laminate formed from the present dispersion (1) or the present dispersion (2) has excellent component distribution uniformity and highly expresses the properties of the F polymer. Further, the laminated body is excellent in surface smoothness.

Claims (15)

A method for producing a dispersion, in which a powder of a tetrafluoroethylene polymer and a liquid compound having a surface tension of 30 mN / m or less are mixed to obtain a mixture, and the mixture and a liquid dispersion medium are mixed. The method for producing a dispersion liquid according to claim 1, wherein the liquid compound is 100 parts by mass or less with respect to 100 parts by mass of the powder of the tetrafluoroethylene polymer. The method for producing a dispersion liquid according to claim 1 or 2, wherein the liquid dispersion medium exceeds 100 parts by mass with respect to 100 parts by mass of the powder of the tetrafluoroethylene polymer. The method for producing a dispersion according to any one of claims 1 to 3, wherein the liquid compound is at least one liquid compound selected from the group consisting of alcohols and ketones. The method for producing a dispersion according to any one of claims 1 to 4, wherein the liquid dispersion medium is at least one liquid dispersion medium selected from the group consisting of water, amides and hydrocarbons. The method for producing a dispersion liquid according to any one of claims 1 to 5, wherein the mixture is further kneaded and then mixed with the liquid dispersion medium. The method for producing a dispersion according to any one of claims 1 to 6, wherein at least one selected from the group consisting of an inorganic filler and an aromatic polymer is further mixed. The method for producing a dispersion liquid according to any one of claims 1 to 7, wherein a fluorine-based surfactant is substantially not added. The method for producing a dispersion according to claims 1 to 8, wherein the tetrafluoroethylene polymer is a tetrafluoroethylene polymer containing a unit based on perfluoro (alkyl vinyl ether) or a unit based on hexafluoropropylene. The method for producing a dispersion liquid according to claims 1 to 9, wherein the tetrafluoroethylene polymer is a tetrafluoroethylene polymer having an oxygen-containing atomic group. At least one selected from the group consisting of tetrafluoroethylene polymer powder, alcohol and ketone, and at least one selected from the group consisting of liquid compounds having a surface tension of 30 mN / m or less, and amides and hydrocarbons. A dispersion liquid containing a liquid dispersion medium or water having a surface tension of 20 mN / m or more and 50 mN / m or less and having a solid content of 25% by mass or more. The dispersion according to claim 11, which comprises at least one selected from the group consisting of an inorganic filler and an aromatic polymer. The dispersion according to claim 11 or 12, wherein the solid content is 50% by mass or more. The dispersion liquid according to any one of claims 11 to 13, which has a viscosity of 1000 to 100,000 mPa · s. The dispersion liquid according to any one of claims 11 to 14, which does not substantially contain a fluorine-based surfactant.