TWI855051B - Powder dispersion, method for producing powder dispersion, and method for producing resin-coated substrate - Google Patents

Abstract

The present invention provides a powder dispersion having excellent defoaming and film-forming properties, a method for producing the same, and a method for producing a resin substrate having a polymer layer with a relatively high surface flatness. The powder dispersion of the present invention contains a tetrafluoroethylene polymer powder, a first liquid compound having a boiling point of 80 to 260°C, and a second liquid compound. The second liquid compound is different from the first liquid compound in that the evaporation rate of the second liquid compound is 0.01 to 0.3 when the evaporation rate of butyl acetate is set to 1, and the boiling point is 140 to 260°C. In addition, in the method for producing the powder dispersion of the present invention, the powder is mixed with a liquid composition containing the first liquid compound and the second liquid compound.

Description

Powder dispersion, method for producing powder dispersion, and method for producing resin-coated substrate

The present invention relates to a powder dispersion liquid in which a powder is dispersed in at least two liquid compounds, a method for producing the same, and a method for producing a resin-coated substrate using the powder dispersion liquid.

Tetrafluoroethylene polymers such as polytetrafluoroethylene (PTFE) have excellent physical properties such as chemical resistance, water and oil repellency, heat resistance, and electrical properties, and are used in various industrial applications by utilizing their physical properties. Among them, a powder dispersion containing a powder of a tetrafluoroethylene polymer can impart the physical properties of a fluoroolefin polymer to the surface if applied to the surface of various substrates, and is therefore useful as a coating agent (see patent documents 1 and 2). Prior art documents Patent documents

Patent document 1: International Publication No. 2016/159102 Patent document 2: International Publication No. 2018/016644

[The problem the invention is trying to solve]

From the perspective of improving the efficiency of preparation, this type of powder dispersion requires not only better defoaming properties, but also further improved film-forming properties when forming a coating. After intensive research, the inventors of this case found that the powder dispersion using a liquid compound (solvent) with a relatively low evaporation rate has excellent defoaming and film-forming properties. [Technical means to solve the problem]

The present invention has the following aspects. [1] A powder dispersion containing a tetrafluoroethylene polymer powder, a first liquid compound having a boiling point of 80 to 260°C, and a second liquid compound, wherein the second liquid compound is different from the first liquid compound in that its evaporation rate is 0.01 to 0.3 when the evaporation rate of butyl acetate is set to 1, and its boiling point is 140 to 260°C. [2] A powder dispersion as in [1], wherein the ratio of the mass of the second liquid compound contained in the powder dispersion to the mass of the first liquid compound is less than 1. [3] A powder dispersion as in [1] or [2], wherein the first liquid compound is a ketone, an ester, an amide or an aromatic hydrocarbon. [4] A powder dispersion as described in any one of [1] to [3], wherein the second liquid compound is diisobutyl ketone, 4-hydroxy-4-methyl-2-pentanone, isophorone, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, 2-ethoxyethyl acetate, 3-methoxy-3-methylbutanol, 3-methoxy-3-methylbutyl acetate, propylene glycol monopropyl ether, 3-methoxybutyl acetate, propylene glycol monomethyl ether propionate or diethylene glycol monobutyl ether. [5] A powder dispersion as described in any one of [1] to [4], wherein the second liquid compound is 4-hydroxy-4-methyl-2-pentanone, isophorone, 3-methoxy-3-methylbutanol, 3-methoxy-3-methylbutyl acetate or 3-methoxybutyl acetate.

[6] A powder dispersion as described in any one of [1] to [5], wherein the average particle size of the powder is 40 μm or less. [7] A powder dispersion as described in any one of [1] to [6], wherein the amount of the powder contained in the powder dispersion is 10% by mass or more. [8] A powder dispersion as described in any one of [1] to [7], wherein the tetrafluoroethylene polymer is a hot melt polymer having a melting temperature of 140 to 320°C. [9] A powder dispersion as described in any one of [1] to [8], wherein the tetrafluoroethylene polymer is a polymer having a unit based on tetrafluoroethylene and a functional group. [10] A powder dispersion as described in [9], wherein the polymer is a polymer having a unit based on tetrafluoroethylene and a unit based on a monomer having a functional group.

[11] A powder dispersion as described in any one of [1] to [10], further comprising a dispersant having a hydrophilic group and a hydrophobic group, wherein the hydrophilic group has a polyoxyalkylene group or a hydroxyl group, and the hydrophobic group has a perfluoroalkyl group, a perfluoroalkyl group having an ethereal oxygen atom, or a perfluoroalkenyl group. [12] A powder dispersion as described in any one of [1] to [11], wherein the viscosity of the powder dispersion at 25°C is 1000 mPa·s or less. [13] A method for producing a powder dispersion, which is a method for producing a powder dispersion as described in any one of [1] to [12], comprising mixing the powder with a liquid composition containing the first liquid compound and the second liquid compound to obtain a powder dispersion. [14] A method for manufacturing a resin substrate, comprising applying a powder dispersion as described in any one of [1] to [12] above to the surface of a substrate, heating the substrate to remove the first liquid compound and the second liquid compound, and baking the tetrafluoroethylene polymer to form a polymer layer containing the tetrafluoroethylene polymer, thereby obtaining a resin substrate having the substrate and the polymer layer. [15] A method as described in [14], wherein the thickness of the polymer layer is less than 20 μm. [Effect of the invention]

The powder dispersion of the present invention has excellent defoaming and film-forming properties. According to the method for producing the powder dispersion of the present invention, such a powder dispersion can be produced. According to the method for producing the resin-coated substrate of the present invention, a resin-coated substrate having a polymer layer with high surface flatness can be obtained.

The following terms have the following meanings. "Melt viscosity of polymer" is a value measured based on ASTM D1238, using a rheometer and a 2Φ-8L mold, applying a load of 0.7 mPa to a polymer sample (2 g) that has been heated at a measured temperature for 5 minutes, and maintaining the measured temperature. "Melting temperature of polymer" corresponds to the temperature of the maximum value of the melting peak measured by differential scanning calorimetry (DSC). "Average particle size of powder (D50)" is the volume-based cumulative 50% diameter obtained by the laser diffraction and scattering method. That is, the particle size distribution is measured by the laser diffraction and scattering method, the total volume of the particle cluster is set to 100%, and the cumulative curve is obtained. The particle size at the point where the cumulative volume is 50% on the cumulative curve. "D90 of powder" is the volume reference cumulative 90% diameter obtained by the laser diffraction and scattering method. That is, the particle size distribution is measured by the laser diffraction and scattering method, the total volume of the particle cluster is set to 100%, and the cumulative curve is obtained. The particle diameter at the point where the cumulative volume is 90% on the cumulative curve. The D50 and D90 of particles are obtained by dispersing the particles in water and analyzing them using the laser diffraction and scattering method using a laser diffraction and scattering particle size distribution measuring device (manufactured by Horiba, Ltd., LA-920 measuring device). "Viscosity of powder dispersion" is the value measured using a B-type viscometer at room temperature (25°C) and a rotation speed of 30 rpm. The measurement was repeated three times and the average value of the three measurements was taken as the value. The so-called "thickness ratio of the powder dispersion" refers to the value calculated by dividing the viscosity _η1 measured at a rotation speed of 30 rpm by the viscosity _η2 measured at a rotation speed of 60 rpm. The measurement of each viscosity was repeated three times and the average value of the three measurements was taken as the value. "(Meth)acrylate" is a general term for acrylate and methacrylate. The so-called "unit" constituting a polymer refers to the general term for the atomic group based on the above-mentioned monomer 1 molecule directly formed by the polymerization of the monomer, and the atomic group obtained by chemically converting a part of the above-mentioned atomic group. Units based on specific monomers are sometimes represented by adding "unit" to the name of the monomer.

The powder dispersion of the present invention contains a powder of a tetrafluoroethylene polymer (hereinafter also referred to as "F polymer"), a first liquid compound having a boiling point of 80 to 260°C, and a second liquid compound. The second liquid compound is different from the first liquid compound in that the evaporation rate of the second liquid compound is 0.01 to 0.3 when the evaporation rate of butyl acetate is set to 1, and the boiling point is 140 to 260°C. In addition, the evaporation rate of the liquid compound when the evaporation rate of butyl acetate is set to 1 is referred to as "evaporation rate" hereinafter. The powder dispersion has excellent defoaming and film-forming properties. The reason may not be clear, but it is considered to be the following.

The second liquid compound is a compound with a lower evaporation rate and a higher boiling point, and is generally a compound with a larger molecular weight having a hydrophobic portion and a polar portion. The second liquid compound is able to interact with both the F polymer and the first liquid compound. Therefore, it is believed that the second liquid compound itself functions as a dispersant for the powder. In addition, when the powder dispersion contains other dispersants, it is believed that it functions in a manner that enhances the dispersing effect of the powder obtained using the above-mentioned dispersants. The results are inferred: Since the surface tension of the powder dispersion as a whole is effectively reduced, the dispersion of the powder is promoted and the foaming of the powder dispersion is suppressed (showing good defoaming properties).

In addition, the evaporation rate of the second liquid compound is relatively low, and it can also be called a slow-drying solvent. It is believed that the first liquid compound gives the powder dispersion good fluidity, and promotes the formation of a coating with uniform thickness when the coating (liquid coating) is formed. On the other hand, it is believed that since the second liquid compound, which is a slow-drying solvent, evaporates slowly, it prevents the surface roughness of the coating caused by the rapid generation of bubbles accompanying the volatilization, and improves the surface flatness of the coating. In addition, it is also believed that the second liquid compound also functions as a leveling agent to improve the flatness of the coating when the coating is drying (preventing the formation of curved corners). It is speculated that through these synergistic effects, the powder dispersion exhibits excellent film-forming properties. In particular, it is considered that the interaction between the particles of the F polymer powder is weak, and the second liquid compound is easily present between them. Therefore, if the powder dispersion of the present invention is used, the above-mentioned effect can be more significantly exerted.

In the manufacturing method of the resin-attached substrate of the present invention, the powder dispersion is applied to the surface of the substrate, heated to remove the first liquid compound and the second liquid compound, and the F polymer is baked to form a polymer layer containing the F polymer, thereby obtaining a resin-attached substrate having a substrate and a polymer layer. The polymer layer of the resin-attached substrate obtained by the present invention is formed using the powder dispersion of the present invention, so the surface flatness is excellent. The above effect is more obviously manifested in the following preferred embodiment of the present invention.

The D50 of the powder in the present invention is preferably 40 μm or less, more preferably 20 μm or less, and particularly preferably 8 μm or less. The D50 of the powder is preferably 0.01 μm or more, more preferably 0.1 μm or more, and particularly preferably 1 μm or more. In addition, the D90 of the powder is preferably 80 μm or less, and further preferably 50 μm or less. The powder with D50 and D90 in this range has good fluidity and dispersibility, and is most likely to show the electrical properties (low dielectric constant, etc.) or heat resistance of the polymer layer. In addition, the defoaming and film-forming properties of the powder dispersion are further improved. The loose packing density of the powder is preferably 0.08 to 0.5 g/mL. The dense packing density of the powder is preferably 0.1 to 0.8 g/mL. When the sparse packing bulk density or dense packing bulk density is within the above range, the powder has excellent handling properties.

The powder of the present invention may contain resins other than F polymer. The powder of the present invention is preferably a powder containing F polymer as the main component. The content of F polymer in the powder is preferably 80% by mass or more, and more preferably 100% by mass. As the above-mentioned resin, aromatic polyester, polyamide imide, thermoplastic polyimide, polyphenylene ether, and polyphenylene oxide can be listed.

The F polymer in the present invention is a polymer containing units based on tetrafluoroethylene (hereinafter also referred to as "TFE"). The F polymer can be a homopolymer of TFE or a copolymer of TFE and a comonomer capable of copolymerizing with TFE. As the F polymer, it is preferably an F polymer containing 90 to 100 mol% TFE units relative to all units constituting the polymer. In addition, the fluorine content of the F polymer is preferably 70 to 76% by mass, and more preferably 72 to 76% by mass.

As F polymers, there are polytetrafluoroethylene (PTFE), copolymers of TFE and ethylene (ETFE), copolymers of TFE and propylene, copolymers of TFE and perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE") (PFA), copolymers of TFE and hexafluoropropylene (hereinafter also referred to as "HFP") (FEP), copolymers of TFE and fluoroalkylethylene (hereinafter also referred to as "FAE"), and copolymers of TFE and chlorotrifluoroethylene. The copolymers may further contain units based on other copolymer monomers. Furthermore, as PTFE, there are high molecular weight PTFE, low molecular weight PTFE, and modified PTFE having protofibrous properties. In addition, low molecular weight PTFE or modified PTFE also contains copolymers of TFE and extremely small amounts of copolymer monomers (HFP, PAVE, FAE, etc.).

As the F polymer, a F polymer having a TFE unit and a functional group is preferred. As the functional group, a carbonyl-containing group, a hydroxyl group, an epoxy group, an amide group, an amino group, and an isocyanate group are preferred. The functional group may be contained in a unit in the F polymer or in a terminal group of the main chain of the polymer. In addition, a polymer having a functional group obtained by subjecting the F polymer to plasma treatment or radiation treatment may also be used. As the F polymer having a functional group, from the viewpoint of the dispersibility of the powder in the powder dispersion, a F polymer containing a TFE unit and a unit having a functional group is preferred. As the unit having a functional group, a unit having the above-mentioned functional group is preferred. The monomer having a functional group is preferably a monomer having an acid anhydride residue, and more preferably itaconic anhydride, cisaconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride (also known as bicycloheptene dicarboxylic anhydride; hereinafter also referred to as "NAH") and maleic anhydride.

As suitable specific examples of the F polymer having a functional group, there can be cited the F polymer having the following units: TFE unit; HFP unit, PAVE unit or FAE unit; and a unit having a functional group _. As _PAVE , there can be cited _CF2 = _CFOCF3 , _CF2 = _CFOCF2CF3 , _CF2 = _{CFOCF2CF2CF3 (} hereinafter also referred to as " _PPVE "), _CF2 = _{CFOCF2CF2CF2CF3 , CF2 =} CFO( _CF2 ) _8F . As FAE, _CH2 =CH( _CF2 ) _2F , _CH2 =CH( _CF2 ) _3F , _CH2 =CH( _{CF2)4F, CH2=CF(CF2 ) 3H , CH2 =} CF( _CF2 ) _4H can be cited. As a specific example of the polymer F, an F polymer containing 90 to 99 mol% of TFE units, 0.5 to 9.97 mol% of HFP units, PAVE units or FAE units, and 0.01 to 3 mol% of units having functional groups, respectively, relative to all units constituting the polymer can be cited. As a specific example of the polymer F, a polymer described in International Publication No. 2018/16644 can be cited.

The melt viscosity of the F polymer at 380°C is preferably 1×10 ² to 1×10 ⁶ Pa·s, more preferably 1×10 ³ to 1×10 ⁶ Pa·s. The F polymer is preferably a heat-melting polymer, and more preferably a heat-melting polymer having a melting temperature higher than either the boiling point of the first liquid compound or the boiling point of the second liquid compound. The melting temperature of the heat-melting polymer is preferably 140 to 320°C, more preferably 200 to 320°C, and further preferably 260 to 320°C. When the F polymer is used, it is easy to form a polymer layer with better surface flatness.

The first liquid compound and the second liquid compound in the present invention are both 25°C liquid compounds, which can be aqueous solvents or non-aqueous solvents. As the first liquid compound, it is preferred to be a compound with a higher evaporation rate and not to evaporate instantly. The evaporation rate of the first liquid compound is preferably higher than the evaporation rate of the second liquid compound. In other words, the first liquid compound preferably has an evaporation rate exceeding 0.3. The boiling point of the first liquid compound is 80-260°C, preferably 100-250°C, and more preferably 120-240°C. Within this range, when the powder dispersion is applied to the surface of the substrate, good fluidity is imparted to the powder dispersion, and when the liquid component (solvent, etc.) is removed by heating and distilling from the powder dispersion, the first liquid compound is effectively volatilized. In addition, from the perspective of achieving a good balance between the fluidity of the powder and the viscosity of the powder dispersion, the viscosity of the first liquid compound at 20 to 25°C is preferably 5.0 mPa·s or less, and more preferably 4.0 mPa·s or less. The lower limit of the above viscosity is usually 0.1 mPa·s.

As the first liquid compound, ketones, esters, amides, alcohols, sulfones, glycol ethers and aromatic hydrocarbons are preferred, and ketones, esters, amides and aromatic hydrocarbons are more preferred. If the first liquid compound is used, it is easy to improve the film-forming property of the powder dispersion. Furthermore, two or more first liquid compounds can be used in combination. As suitable specific examples of the first liquid compound, there can be mentioned methyl ethyl ketone, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide, N-methyl-2-pyrrolidone, γ-butyrolactone, cyclohexanone, cyclopentanone, toluene, xylene, 1,2,4-trimethylbenzene and 1,2,3-trimethylbenzene, and more preferably methyl ethyl ketone, 3-methoxy-N,N-dimethylpropionamide, N-methyl-2-pyrrolidone and cyclohexanone. Furthermore, although the specific values of the evaporation rates of these compounds are unknown, they obviously have a higher evaporation rate than the second liquid compound described below.

The second liquid compound is a compound different from the first liquid compound and has a relatively low evaporation rate. Specifically, the evaporation rate of the second liquid compound is 0.01 to 0.3, preferably 0.03 to 0.20, and more preferably 0.05 to 0.15 when the evaporation rate of butyl acetate is set to 1. In addition, the boiling point of the second liquid compound is 140 to 260°C, preferably 160 to 240°C, and more preferably 180 to 220°C. If a second liquid compound having an evaporation rate and boiling point within the above range is used, even after the first liquid compound is removed by heating and distillation, a sufficient amount of the second liquid compound remains in the coating film, and then heating and distillation are performed at an appropriate rate to remove it. Therefore, the second liquid compound can better exert the effect of improving the surface flatness of the polymer layer. Furthermore, the difference between the boiling points of the first liquid compound and the second liquid compound is preferably within ±40°C, more preferably within ±30°C.

Examples of the second liquid compound include diisobutyl ketone (evaporation rate: 0.2, boiling point: 168°C), 4-hydroxy-4-methyl-2-pentanone (evaporation rate: 0.15, boiling point: 168°C), isophorone (evaporation rate: 0.026, boiling point: 215°C), ethylene glycol mono-n-butyl ether (evaporation rate: 0.08, boiling point: 170°C), ethylene glycol mono-tert-butyl ether (evaporation rate: 0.19, boiling point: 153°C), 2-ethoxyethyl acetate (evaporation rate: 0.21, boiling point: 156°C). ), 3-methoxy-3-methylbutanol (evaporation rate: 0.07, boiling point: 174°C), 3-methoxy-3-methylbutyl acetate (evaporation rate: 0.10, boiling point: 188°C), propylene glycol monopropyl ether (evaporation rate: 0.22, boiling point: 150°C), 3-methoxybutyl acetate (evaporation rate: 0.14, boiling point: 171°C), propylene glycol monomethyl ether propionate (evaporation rate: 0.19, boiling point: 160°C), and diethylene glycol monobutyl ether (evaporation rate: 0.004, boiling point: 230°C). Furthermore, these compounds can be used in combination of two or more. Among them, as the second liquid compound, 4-hydroxy-4-methyl-2-pentanone, isophorone, 3-methoxy-3-methylbutanol, 3-methoxy-3-methylbutyl acetate and 3-methoxybutyl acetate are preferred. These compounds can also be regarded as compounds that can function as surfactants (powder dispersants) and plasticizers, and can easily further improve the flatness of the polymer layer.

The ratio of the mass of the second liquid compound contained in the powder dispersion to the mass of the first liquid compound (content of the second liquid compound/content of the first liquid compound) is preferably less than 1, more preferably 0.1 to 0.9, and further preferably 0.2 to 0.8. When the first liquid compound and the second liquid compound are contained in an appropriate amount ratio, the powder dispersion can exhibit good defoaming properties and excellent film-forming properties in a balanced manner.

The powder dispersion of the present invention preferably further contains a dispersant from the viewpoint of further improving the dispersibility of the powder. The dispersant is a compound having a hydrophilic group and a hydrophobic group. As the dispersant, a fluorine-based dispersant, a silicone-based dispersant and an acetylene-based dispersant are preferred, and a fluorine-based dispersant is more preferred. In addition, as the dispersant, a non-ionic dispersant is preferred. As the above-mentioned hydrophilic group, polyoxyalkylene groups and hydroxyl groups are preferred. As the polyoxyalkylene groups, polyoxyethylene groups and polyoxyalkylene groups having an oxyethylene group and a polyoxyalkylene group having a carbon number of 3 or more are preferred. On the other hand, the hydrophobic group is appropriately selected according to the type of the dispersant. In the case of a fluorine-based dispersant, perfluoroalkyl groups, perfluoroalkyl groups having etheric oxygen atoms, and perfluoroalkenyl groups are preferred as hydrophobic groups. In this case, the dispersant has a balanced affinity for each component, which makes it easier to further improve the dispersibility of the powder in the powder dispersion and also to further improve its film-forming properties.

As the fluorine-based dispersant, fluorine monoalcohols and fluorine polyols are preferred, and fluorine monoalcohols having a fluorine content of 10 to 50% by mass and a hydroxyl value of 40 to 100 mgKOH/g, or fluorine polyols having a fluorine content of 10 to 50% by mass and a hydroxyl value of 10 to 35 mgKOH/g are more preferred. Examples of the fluorine monoalcohol include F(CF ₂ ) ₆ CH ₂ (OCH ₂ CH ₂ ) ₇ -(OCH ₂ CH(CH ₃ ))OH, F(CF ₂ ) ₆ CH ₂ (OCH ₂ CH ₂ ) ₁₂ -(OCH ₂ CH(CH ₃ ))OH, F(CF ₂ ) ₆ CH ₂ CH ₂ (OCH ₂ CH ₂ ) ₇ -(OCH ₂ CH(CH ₃ ))OH, F (CF ₂ ) ₆ CH ₂ CH ₂ (OCH ₂ CH ₂ ) ₁₂ -(OCH ₂ CH(CH ₃ ))OH, F(CF ₂ ) ₄ CH ₂ CH ₂ (OCH ₂ CH ₂ ) ₇ -(OCH ₂ CH(CH ₃ ))OH, F(CF ₂ ) ₄ CH ₂ CH ₂ (OCH ₂ CH ₂ ) ₁₂ -(OCH ₂ CH(CH ₃ ))OH.

Examples of the fluoropolyol include polymers containing units based on fluoro(meth)acrylate and units based on polyoxyalkylene glycol mono(meth)acrylate. The polymer is a polymer other than the F polymer.

Specific examples of the former (meth)acrylate include _CH2 =C( _CH3 )C( _{O ) OCH2CH2} ( _CF2 ) _6F , _CH2 =CHC(O ₎ OCH2CH2(CF2)6F, _CH2 =C( _CH3 )C(O)OCH2CH2( _CF2 ) _4F , _CH2 =CClC(O)OCH2CH2( _{CF2 ) 4F} , CH2=C( _CH3 )C(O)OCH2CH2CH2CH2OCF( _CF3 ) _{C( = C} (CF3) ₂ ) ₍ CF( _CF3 ) ₂ ), _CH2 =CH3C(O) _{OCH2CH2CH2CH2OCF} ( _CF3 )C(= _C ( _CF3 ) ₂ )(CF( _CF3 ) ₂ ), and _CH2 = _CH3C ( _{O )} OCH2CH2CH2CH2OCF( _CF3 )C(= _C ( _CF3 ) ₂ )(CF(CF ₃ ) ₂ ).

Specific examples of the latter (meth)acrylate include _CH2 =C( _CH3 )C(O)( _OCH2CH2 ) _4OH , _CH2 =C( _CH3 )C(O)(OCH2CH2) _9OH , _CH2 = _C ( _CH3 )C(O) _{(OCH2CH2)23OH, CH2 = C (} CH3 ₎ C(O)( _OCH2CH2 )66OH, _{CH2 =} C( _CH3 )C(O) _{(OCH2CH2 )} 90OH, _CH2 =C(CH3)C(O) ₍ OCH2CH2)120OH, _{CH2 = C} ( _CH3 )C(O) _{( OCH2CH2 )} 4OH, _{CH2 = C} (CH3 ₎ C(O)( _{OCH2CH2 ) 8OH .} OH, CH ₂ =C(CH ₃ )C(O)(OCH ₂ CH(CH ₃ )) ₄ OH, CH ₂ =C(CH ₃ )C(O)(OCH ₂ CH(CH ₃ )) ₈ OH, CH ₂ =C(CH ₃ )C(O)(OCH ₂ CH(CH ₃ )) ₉ OH, CH ₂ =C(CH ₃ )C(O)(OCH ₂ CH(CH ₃ )) ₁₃ OH, CH ₂ =C(CH ₃ )C(O)(OCH ₂ CH ₂ ) ₄ -(OCH ₂ CH(CH ₃ )) ₃ OH, CH ₂ =C(CH ₃ )C(O)(OCH ₂ CH ₂ ) ₁₀ -(OCH ₂ CH ₂ CH ₂ CH ₂ ) ₅ OH.

The ratio of the powder to the powder dispersion is preferably 10% by mass or more, more preferably 20 to 50% by mass. In this case, it is easy to form a polymer layer with excellent physical properties (especially electrical properties). The total ratio of the first liquid compound and the second liquid compound to the powder dispersion (the ratio of the solvent) is preferably 15 to 55% by mass, more preferably 25 to 50% by mass. In this case, the coating property of the powder dispersion is excellent, and the film-forming property is also easy to improve. In addition, when the powder dispersion contains a dispersant, the ratio relative to the powder dispersion is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass. In this case, the dispersibility of the powder in the powder dispersion is further improved, and the physical properties of the polymer layer are easy to further improve.

Furthermore, the powder dispersion may contain other materials within the range that does not impair the effect of the present invention. The other materials may be soluble in the powder dispersion or may not be soluble. The other materials may be non-hardening resins or hardening resins. As non-hardening resins, hot-melt resins and non-melting resins can be listed. As hot-melt resins, thermoplastic polyimide can be listed. As non-melting resins, hardened materials of hardening resins can be listed.

As the curable resin, there can be listed polymers having a reactive group, oligomers having a reactive group, low molecular weight compounds, and low molecular weight compounds having a reactive group. As the reactive group, there can be listed carbonyl-containing groups, hydroxyl groups, amino groups, and epoxy groups. Examples of the curable resin include epoxy resin, thermosetting polyimide, polyamide as a precursor of polyimide, curable acrylic resin, phenol resin, curable polyester resin, curable polyolefin resin, modified polyphenylene ether resin, polyfunctional cyanate resin, polyfunctional cis-1,1-diimide-cyanate resin, polyfunctional cis-1,1-diimide resin, vinyl ester resin, urea resin, diallyl phthalate resin, melanin resin, guanamine resin, and melamine-urea co-condensation resin.

Specific examples of epoxy resins include naphthalene type epoxy resins, cresol novolac type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, alicyclic epoxy resins, aliphatic chain epoxy resins, cresol novolac type epoxy resins, phenol novolac type epoxy resins, alkylphenol novolac type epoxy resins, aralkyl type epoxy resins, and biphenol type epoxy resins. Examples of the bis(cis-butylene) imide resin include the resin composition (BT resin) described in Japanese Patent Laid-Open No. 7-70315 and the resin described in International Publication No. 2013/008667. Polyamine generally has a reactive group capable of reacting with the functional group possessed by the F polymer. Examples of diamines and polycarboxylic acid dianhydrides that form polyamine include compounds described in [0020] of Japanese Patent No. 5766125, [0019] of Japanese Patent No. 5766125, [0055] and [0057] of Japanese Patent Laid-Open No. 2012-145676, etc.

As the hot melt resin, there can be listed thermoplastic resins such as thermoplastic polyimide and hot melt hardened materials of hardening resins. As the thermoplastic resin, there can be listed polyester resins, polyolefin resins, styrene resins, polycarbonate, thermoplastic polyimide, polyarylate, polysulfide, polyarylether sulfide, aromatic polyamide, aromatic polyether amide, polyphenylene sulfide, polyarylether ketone, polyamide imide, liquid crystalline polyester, polyphenylene ether, preferably thermoplastic polyimide, liquid crystalline polyester and polyphenylene ether. Furthermore, as the other materials, there can also be listed thixotropic agents, defoaming agents, inorganic fillers, reactive alkoxysilanes, dehydrating agents, plasticizers, weathering agents, antioxidants, thermal stabilizers, lubricants, antistatic agents, whitening agents, coloring agents, conductive agents, mold release agents, surface treatment agents, viscosity regulators, and flame retardants.

The viscosity of the powder dispersion at 25°C is preferably 1000 mPa·s or less, more preferably 50 to 1000 mPa·s, and further preferably 100 to 500 mPa·s. In this case, the powder dispersion not only has excellent dispersibility, but also has excellent coating properties or compatibility with varnishes of different types of resin materials. In addition, according to the present invention, it is easy to prepare (manufacture) such a relatively low viscosity powder dispersion. In addition, the thixotropic ratio (η ₁ /η ₂ ) of the powder dispersion is preferably 1 to 2.5, more preferably 1.2 to 2. In this case, the powder dispersion not only has excellent dispersibility, but also the homogeneity of the polymer layer is easy to improve.

The powder dispersion of the present invention can be manufactured by mixing the above-mentioned powder, the first liquid compound and the second liquid compound. The powder, the first liquid compound and the second liquid compound can be mixed together, or they can be mixed in sequence in any combination. The powder dispersion of the present invention is preferably prepared by pre-mixing the first liquid compound and the second liquid compound, obtaining a liquid composition containing them, and then mixing the powder with the liquid composition. That is, as a method for manufacturing the powder dispersion of the present invention, it is preferably a method of mixing powder and a liquid composition containing the first liquid compound and the second liquid compound. By mixing the powder, the first liquid compound and the second liquid compound in this order, the powder dispersion is not easy to foam.

The substrate used in the method for manufacturing the resin-attached substrate of the present invention is preferably a metal foil, and more preferably a copper foil such as a rolled copper foil or an electrolytic copper foil. On the surface of the metal foil, a rust-proof layer (such as an oxide film of chromate, etc.), a heat-resistant layer, a roughening treatment layer, and a silane coupling agent treatment layer may be provided. The ten-point average roughness of the surface of the metal foil is preferably 0.2 to 2.5 μm. In this case, the peeling strength (adhesion) between the metal foil and the polymer layer is easily improved. The powder dispersion can be applied to the substrate surface by spraying, roller coating, rotary coating, gravure coating, micro-gravure coating, gravure offset coating, doctor blade coating, contact coating, rod coating, die nozzle coating, fountain Meyer bar coating, slit die nozzle coating, and the like.

By applying the powder dispersion on the substrate surface, a film of the powder dispersion is formed on the substrate surface. Then, by heating to a temperature above the boiling point of the first liquid compound and the second liquid compound, the first liquid compound and the second liquid compound are removed from the film of the powder dispersion, and then by heating to the baking temperature of the F polymer, a polymer layer containing the baked F polymer is formed. The temperature used to volatilize and remove the liquid compound is preferably below the melting temperature of the F polymer, and the baking temperature of the F polymer is preferably above the melting temperature of the F polymer. Since the boiling point of the liquid compound and the melting temperature of the F polymer are usually different, the heating is preferably performed at a temperature of at least two stages. Furthermore, the baking temperature of the F polymer depends on the melting temperature of the F polymer, and is preferably below 400°C. As a heating method, there can be cited a method using an oven, a method using a ventilation drying furnace, and a method of irradiating with heat rays such as infrared rays. Heating can be performed under any state of normal pressure or reduced pressure. In addition, as a heating environment, it can be any of an oxidizing gas environment (oxygen, etc.), a reducing gas environment (hydrogen, etc.), and an inert gas environment (helium, neon, argon, nitrogen, etc.).

According to the manufacturing method of the resin substrate of the present invention, a resin substrate having a two-layer structure of a substrate and a polymer layer can be obtained, and the above-mentioned polymer layer is connected to one surface of the substrate. In addition, the obtained two-layer resin substrate can also be used to repeat the manufacturing method of the present invention to obtain a three-layer resin substrate having polymer layers on both surfaces of the substrate. The thickness of the polymer layer of the resin substrate obtained by the present invention is preferably less than 20 μm, more preferably less than 10 μm, and particularly preferably 0.1 to 8 μm. According to the present invention, even the thinner polymer layer can be formed with higher surface flatness. The polymer layer of the resin substrate obtained by the present invention also has a higher peeling strength from the substrate. The peel strength is preferably 7 N/cm or more, more preferably 10 N/cm or more, and further preferably 13 N/cm or more.

Furthermore, the resin-attached substrate obtained by the present invention can be laminated with other substrates using the surface of the polymer layer as a laminate surface to form a laminate having a layer structure of three or more layers. Examples of such laminates include laminates having a layer structure of substrate/polymer layer/other substrate and laminates having a layer structure of substrate/polymer layer/other substrate/polymer layer/substrate. Examples of other substrates include metal foils or resin plates.

The resin-attached substrate or the above-mentioned laminate obtained by the present invention has a polymer layer formed of F polymer powder, so it has excellent physical properties such as heat resistance, electrical characteristics, chemical resistance (etching resistance), and is useful as a printed wiring board material such as a flexible printed wiring board and a rigid printed wiring board. For example, if the substrate of the resin-attached substrate or other substrates of the above-mentioned laminate is a metal foil, a printed wiring board can be manufactured by a method of etching the metal foil to process it into a metal conductor wiring (transmission circuit) of a specific pattern, or a method of processing the metal foil into a metal conductor wiring by electroplating (semi-additive method, improved semi-additive method, etc.).

The printed wiring board has metal conductor wiring and a polymer layer in sequence. As the structure, metal conductor wiring/polymer layer, metal conductor wiring/polymer layer/metal conductor wiring can be listed. In the printed wiring board, an interlayer insulating film is formed on the metal conductor wiring, and the metal conductor wiring can also be further formed on the interlayer insulating film. The interlayer insulating film can also be formed by the above-mentioned powder dispersion. In addition, a solder resist or a cover film can also be stacked on the metal conductor wiring. The solder resist or the cover film can also be formed by the above-mentioned powder dispersion.

As a specific embodiment of the printed wiring board, a multilayer printed wiring board having the above-mentioned layer structure can be cited. As a suitable embodiment of the multilayer printed wiring board, an embodiment in which the outermost layer of the multilayer printed wiring board is a polymer layer and has a layer structure of one or more metal conductor wiring/polymer layers can be cited. The outermost layer of the multilayer printed wiring board of this embodiment has excellent heat resistance, and even if it is heated during processing, such as heating at 300°C in the reflow step, it is not easy to cause abnormalities.

If the polymer dispersion of the present invention is impregnated into a woven fabric, and then the woven fabric is heated and the powder is baked, a coated woven fabric of a baked product coated with powder can be obtained. The woven fabric is a heat-resistant woven fabric that can withstand heating. As the woven fabric, glass fiber woven fabric, carbon fiber woven fabric, aromatic polyamide fiber woven fabric and metal fiber woven fabric are preferred, and glass fiber woven fabric and carbon fiber woven fabric are more preferred. From the perspective of electrical insulation, a plain woven glass fiber woven fabric composed of E glass yarn for electrical insulation specified in JIS R 3410:2006 is further preferred. From the viewpoint of improving the close adhesion between the fabric and the baked material, the fabric can be treated with a silane coupling agent.

As a method for impregnating the powder dispersion of the present invention into a woven fabric, there can be cited a method of impregnating the woven fabric in the powder dispersion or a method of coating the powder dispersion on the woven fabric. Since the powder dispersion of the present invention contains the F polymer which has excellent adhesion to other materials, even if the number of impregnation or coating is small, a coated woven fabric with a high polymer content and a strong adhesion between the woven fabric and the F polymer can be obtained. The method of heating the woven fabric can be determined according to the type of liquid components contained in the powder dispersion. Generally, the method of drying in an environment of 80 to 260°C and then baking the powder in an environment of 300 to 400°C is adopted.

Since the calcined product contains F polymer, the obtained coated fabric has excellent properties such as high adhesion between the calcined product and the fabric, high surface flatness, and less deformation. The laminate obtained by hot-pressing the fabric and the metal foil has high peel strength and is not easy to warp, so it can be used as a printed circuit board material. In addition, if the powder dispersion of the present invention containing the fabric is applied to the surface of the substrate and heated, a coated fabric layer containing the calcined product and the fabric can be formed, and a laminated body in which the substrate and the coated fabric layer are sequentially laminated can also be manufactured.

The above is an explanation of the powder dispersion, the method for producing the powder dispersion, and the method for producing the resin-attached substrate of the present invention, but the present invention is not limited to the structure of the above-mentioned embodiment. For example, the powder dispersion of the present invention may have any other structure added to the structure of the above-mentioned embodiment, or may be replaced with any structure that produces the same effect. Furthermore, the method for producing the powder dispersion and the method for producing the resin-attached substrate of the present invention may have any other steps added to the structure of the above-mentioned embodiment, or may be replaced with any steps that produce the same effect. [Example]

The present invention is described in detail below by way of embodiments, but the present invention is not limited thereto. 1. Preparation of each component [F polymer] F polymer 1: A copolymer containing 98.0 mol%, 0.1 mol%, and 1.9 mol% of TFE units, NAH units, and PPVE units, respectively (melting temperature: 300°C, melt viscosity at 380°C: 3×10 ⁵ Pa・s) F polymer 2: A copolymer containing 97.5 mol%, 2.5 mol% of TFE units and PPVE units, respectively (melting temperature 305°C, melt viscosity at 380°C: 3×10 ⁵ Pa・s) [Powder] Powder 1: A powder containing F polymer 1 with a D50 of 1.8 μm and a D90 of 5.2 μm Powder 2: A powder containing F polymer 2 with a D50 of 18.8 μm and a D90 of 52.3 μm [Dispersant] Fluorine-based dispersant 1: A powder containing 81 mol%, 19 mol% of CH ₂ =C(CH ₃ )C(O)OCH ₂ CH ₂ (CF ₂ ) ₆ F units and units based on CH ₂ =C(CH ₃ )C(O)(OCH ₂ CH ₂ ) ₂₃ OH, a polymer having a fluorine content of 35 mass % and a hydroxyl value of 19 mgKOH/g

2. Preparation of powder dispersion (Example 1) First, prepare a dispersant solution containing fluorine-based dispersant 1 and 3-methoxy-3-methylbutyl acetate (evaporation rate: 0.10, boiling point: 188°C). Furthermore, the amount of fluorine-based dispersant 1 contained in the dispersant solution is set to 33% by mass. Second, mix the dispersant solution with N-methyl-2-pyrrolidone (NMP; boiling point: 202°C, viscosity (20°C): 1.89 mPa・s) to prepare a liquid composition. Then, add the liquid composition and powder 1 to a crucible, and then add a zirconia ball to the crucible. Thereafter, rotate the crucible at 150 rpm for 1 hour to disperse powder 1 in the liquid composition, and obtain a powder dispersion 1 (viscosity: 120 mPa・s). Furthermore, the amount of the powder 1 contained in the powder dispersion 1 was set to 40 mass %, the amount of the fluorine-based dispersant 1 was set to 5 mass %, the amount of 3-methoxy-3-methylbutyl acetate was set to 10 mass %, and the amount of NMP was set to 45 mass %.

(Example 2 (Comparative Example)) Except that NMP is used instead of 3-methoxy-3-methylbutyl acetate, a powder dispersion 2 (viscosity: 100 mPa・s) is obtained in the same manner as in Example 1. In addition, the amount of powder 1 contained in the powder dispersion 2 is set to 40% by mass, the amount of fluorine-based dispersant 1 is set to 5% by mass, and the amount of NMP is set to 55% by mass.

(Example 3) Except that powder 2 was used instead of powder 1, powder dispersion 3 (viscosity: 180 mPa・s) was obtained in the same manner as in Example 1.

(Example 4 (Comparative Example)) Except that triethylene glycol monobutyl ether (evaporation rate: less than 0.01, boiling point: 271°C) was used instead of 3-methoxy-3-methylbutyl acetate, a powder dispersion 4 (viscosity: 1500 mPa・s) was obtained in the same manner as in Example 3.

(Example 5 (Comparative Example)) Except that ethylene glycol monoethyl ether (evaporation rate: 0.38, boiling point: 136°C) was used instead of 3-methoxy-3-methylbutyl acetate, a powder dispersion 5 (viscosity: 800 mPa・s) was obtained in the same manner as in Example 3.

(Example 6 (Comparative Example)) Except that NMP is used instead of 3-methoxy-3-methylbutyl acetate, a powder dispersion 6 (viscosity: 80 mPa・s) is obtained in the same manner as in Example 3. In addition, the amount of powder 2 contained in the powder dispersion 6 is set to 40% by mass, the amount of fluorine-based dispersant 1 is set to 5% by mass, and the amount of NMP is set to 55% by mass.

3. Evaluation 3-1. Evaluation of defoaming properties When preparing (manufacturing) powder dispersion, confirm the time until the foam disappears and evaluate according to the following criteria. [Evaluation criteria] ○: less than 3 hours △: more than 3 hours and less than 6 hours ×: more than 6 hours

3-2. Evaluation of film-forming properties First, the powder dispersion was applied to the surface of a copper foil (substrate) with a thickness of 18 μm by roll-to-roll reverse gravure printing to form a liquid coating. Second, the copper foil with the liquid coating was placed in a drying oven at 120°C for 5 minutes and dried by heating. Thereafter, the dried coating was heated at 380°C for 3 minutes in a far infrared oven in a nitrogen environment. Thereby, a resin-coated copper foil with a polymer layer formed on the surface of the copper foil was manufactured. Furthermore, the thickness of the polymer layer was 4 μm.

Then, all the copper foil was removed from the obtained resin-coated copper foil by an acid solution to obtain a single polymer layer. Then, the central part of the polymer layer was visually observed under a fluorescent lamp, and the central part and the end of the polymer layer surface were observed using an optical interference microscope, and the thickness unevenness (whether the flatness is good) was evaluated according to the following criteria. [Evaluation criteria] ○: No thickness unevenness of the polymer layer was observed under a fluorescent lamp, and the film thickness difference between the central part and the end of the polymer layer surface observed using an optical interference microscope was less than 10%. △: No thickness unevenness of the polymer layer was observed under a fluorescent lamp, and the film thickness difference between the central part and the end of the polymer layer surface observed using an optical interference microscope exceeded 10%. ×: The thickness of the polymer layer was observed to be uneven under a fluorescent light. The difference in film thickness between the center and the end of the polymer layer surface observed using an optical interference microscope exceeded 10%.

The above results are shown in Table 1. [Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Defoaming ○ × △ △ × × Film forming properties ○ △ ○ - × × The powder dispersions of Examples 1 and 3 have good defoaming properties and film-forming properties. In contrast, the powder dispersions of Examples 2 and 4 to 6 have at least one of poor defoaming properties and film-forming properties. In addition, the coating formed using the powder dispersion of Example 4 under the conditions of "3-2. Evaluation of film-forming properties" was not sufficiently dried and could not be evaluated. [Industrial Applicability]

The powder dispersion of the present invention can be used for the manufacture of films, impregnations (prepregs, etc.), laminates (resin substrates such as resin copper foils), etc., and can be used for applications requiring mold release, electrical properties, water and oil repellency, chemical resistance, weather resistance, heat resistance, sliding, wear resistance, etc. In addition, the resin substrate can be processed into antenna parts, printed wiring boards, insulation layers of power semiconductors, aircraft parts, automotive parts, etc. Furthermore, all contents of the specification, patent application scope and abstract of Japanese Patent Application No. 2019-075499 filed on April 11, 2019 are cited in this article and introduced as the contents of the specification of the present invention.

Claims (9)

A powder dispersion liquid, comprising a tetrafluoroethylene polymer powder, a first liquid compound having a boiling point of 80-260°C, and a second liquid compound, wherein the second liquid compound is different from the first liquid compound, has an evaporation rate of 0.01-0.3 when the evaporation rate of butyl acetate is set to 1, and has a boiling point of 140-260°C, wherein the mass ratio of the second liquid compound contained in the powder dispersion liquid to the mass ratio of the first liquid compound is less than 1, the first liquid compound is a ketone, an ester, an amide or an aromatic hydrocarbon, and the second liquid compound is Diisobutyl ketone, 4-hydroxy-4-methyl-2-pentanone, isophorone, ethylene glycol mono-n-butyl ether, ethylene glycol mono-tert-butyl ether, 2-ethoxyethyl acetate, 3-methoxy-3-methylbutanol, 3-methoxy-3-methylbutyl acetate, propylene glycol monopropyl ether, 3-methoxybutyl acetate, propylene glycol monomethyl ether propionate or diethylene glycol monobutyl ether, the average particle size of the above powder is 40μm or less, the amount of the above powder contained in the above powder dispersion is 10% by mass or more, and the above tetrafluoroethylene polymer is a hot-melt polymer with a melting temperature of 140~320℃. The powder dispersion of claim 1, wherein the second liquid compound is 4-hydroxy-4-methyl-2-pentanone, isophorone, 3-methoxy-3-methylbutanol, 3-methoxy-3-methylbutyl acetate or 3-methoxybutyl acetate. The powder dispersion of claim 1 or 2, wherein the tetrafluoroethylene polymer is a polymer having units and functional groups based on tetrafluoroethylene. A powder dispersion as claimed in claim 3, wherein the polymer is a polymer having units based on tetrafluoroethylene and units based on monomers having functional groups. The powder dispersion of claim 1 or 2 further contains a dispersant having a hydrophilic group and a hydrophobic group, wherein the hydrophilic group has a polyoxyalkylene group or a hydroxyl group, and the hydrophobic group has a perfluoroalkyl group, a perfluoroalkyl group having an ethereal oxygen atom, or a perfluoroalkenyl group. For example, the powder dispersion of claim 1 or 2, wherein the viscosity of the powder dispersion at 25°C is less than 1000mPa‧s. A method for producing a powder dispersion, which is a method for producing a powder dispersion as described in any one of claims 1 to 6, wherein the powder is mixed with a liquid composition containing the first liquid compound and the second liquid compound to obtain the powder dispersion. A method for manufacturing a resin-attached substrate, wherein a powder dispersion as described in any one of claims 1 to 6 is applied to the surface of a substrate, heated to remove the first liquid compound and the second liquid compound, and the tetrafluoroethylene polymer is baked to form a polymer layer containing the tetrafluoroethylene polymer, thereby obtaining a resin-attached substrate having the substrate and the polymer layer. The manufacturing method of claim 8, wherein the thickness of the polymer layer is less than 20 μm.