Sizing agent, sized fiber, prepreg, and dispersion

Abstract

This invention provides a specific sizing agent capable of forming molded articles with good appearance such as good smoothness and suppression of bubbling during thermoforming, excellent adhesion and water resistance when used as laminates, fibers and prepregs treated with the sizing agent, and a dispersion containing a powder of a tetrafluoroethylene polymer that exhibits excellent dispersion stability even with reduced surfactant content. The sizing agent contains a powder of a hot-melt tetrafluoroethylene polymer with an average particle size of 0.1 to 200 μm, sizing treated fibers and a prepreg containing the fibers and a matrix resin, and a dispersion containing a powder of a hot-melt tetrafluoroethylene polymer with an average particle size of 10 to 100 μm, a surfactant, and a liquid dispersion medium, wherein the surfactant content is less than 0.01 parts by mass relative to 1 part by mass of the tetrafluoroethylene polymer powder.

Description

Technical Field

[0001] This invention relates to sizing agents containing tetrafluoroethylene polymers, sizing treated fibers, prepregs, and dispersions of powders containing tetrafluoroethylene polymers. Background Technology

[0002] Fiber-reinforced plastics are lightweight and durable. Inorganic fibers used as reinforcing fibers include glass fiber, carbon fiber, boron fiber, and metal fiber, while organic fibers such as aramid fiber, Zylon fiber (poly(p-benzodioxazole)), and polyethylene fiber offer high impact resistance. In particular, due to the excellent mechanical properties of carbon fiber, carbon fiber reinforced composites, obtained by reinforcing matrix resins with carbon fiber, can be widely used as metal substitutes in applications such as aircraft parts, spacecraft parts, automotive parts, and ship parts; sports applications such as golf clubs and fishing rods; and general industrial applications such as office equipment and computer applications (IC trays, laptop casings, etc.).

[0003] Various sizing agents have been studied to improve the affinity between the matrix resin and the reinforcing fiber, enhance interfacial adhesion, improve the strength of the composite material, and reduce damage and facilitate handling by covering and bundling the fibers. As sizing agents, thermosetting resins such as phenolic resin, melamine resin, bismaleimide resin, unsaturated polyester resin, and epoxy resin can be used, with epoxy resin generally being the main component.

[0004] Patent Document 1 discloses a prepreg obtained by impregnating carbon fibers with a specific epoxy resin composition as the matrix resin, wherein a sizing agent containing aliphatic epoxy compounds and aromatic epoxy compounds is attached to the carbon fibers. Patent Document 2 discloses carbon fibers coated with a sizing agent containing a polymer having any one of the following bonds in the main chain: ester bonds, urethane bonds, and carbonate bonds, and discloses a technical solution for obtaining a composite material with excellent mechanical properties from the carbon fibers.

[0005] Furthermore, due to the low surface energy of tetrafluoroethylene polymers, their powders are prone to agglomeration, which can easily lead to problems in their dispersion stability in dispersion liquids.

[0006] Patent document 3 discloses an aqueous dispersion containing a powder of a tetrafluoroethylene polymer.

[0007] Typically, dispersions contain surfactants to improve the dispersion stability of tetrafluoroethylene-based polymer powders. However, after coating the dispersion onto a substrate and drying it, surfactant residues may remain on the substrate surface, causing surface roughness and deterioration in appearance. Furthermore, residual surfactants on the substrate surface can sometimes reduce the electrical properties of the molded product or its adhesion to other substrates.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2014-40566

[0011] Patent Document 2: Japanese Patent Application Publication No. 2020-23770

[0012] Patent Document 3: Japanese Patent Application Publication No. 2019-52211 Summary of the Invention

[0013] The technical problem that the invention aims to solve

[0014] When molding fiber-reinforced composite materials containing ultra-heat-resistant resins, such as super engineering plastics, as the matrix resin, the molding temperature is higher than in the past. In this case, the sizing agent described in Patent Documents 1 and 2 decomposes thermally during heating and molding, producing volatile components that cause foaming in the molded article. This can sometimes lead to problems affecting the appearance of the resulting molded article, such as its smoothness, as well as its adhesion and peel strength.

[0015] After careful research, the inventors discovered that sizing agents containing hot-melt tetrafluoroethylene polymers of a specific particle size exhibit excellent interfacial adhesion to ultra-heat-resistant resins. When this sizing agent is appropriately dispersed in a liquid dispersion medium, the resulting dispersion is applied to fibers. The heat resistance of the tetrafluoroethylene polymers suppresses bubbling during heat molding, resulting in molded articles with excellent smoothness and appearance. Furthermore, the molded articles exhibit particularly good adhesion and water resistance when formed as laminates.

[0016] The inventors have discovered that if a powder containing a tetrafluoroethylene-based polymer with an average particle size within a specified range is used, a dispersion with excellent dispersion stability can be obtained even by reducing the amount of surfactant. This dispersion can be used as a sizing agent, thus completing the present invention.

[0017] The purpose of this invention is to provide a sizing agent that suppresses foaming during heating, sizing treated fibers, prepregs, a dispersion of a powder containing a tetrafluoroethylene polymer and a small amount of surfactant with excellent dispersion stability.

[0018] Technical solutions adopted to solve technical problems

[0019] The present invention has the following form.

[0020] <1> A sizing agent containing powder of a hot-melt tetrafluoroethylene polymer with an average particle size of 0.1 to 200 μm.

[0021] <2> like <1> The sizing agent, wherein the melting temperature of the tetrafluoroethylene polymer is 280–325°C.

[0022] <3> like <1> or <2> The sizing agent wherein the 5% weight reduction temperature of the tetrafluoroethylene polymer is above 360°C.

[0023] <4> like <1> ~ <3> The sizing agent of any one of the following, wherein the tetrafluoroethylene polymer is a tetrafluoroethylene polymer having perfluoro(alkyl vinyl ether)-based units and polar functional groups, or a tetrafluoroethylene polymer containing perfluoro(alkyl vinyl ether)-based units but not having polar functional groups in an amount of 2.0 to 5.0 mol% relative to all units.

[0024] <5> like <4> The sizing agent, wherein the tetrafluoroethylene polymer having polar functional groups is a tetrafluoroethylene polymer containing carbonyl groups, wherein the number of carbonyl groups is 1 × 10⁻⁶ relative to the number of carbon atoms in the main chain. 6 The number ranges from 10 to 5000.

[0025] <6> like <1> ~ <5> The sizing agent of any one of the following is formed from a dispersion containing a powder of the tetrafluoroethylene polymer and a liquid dispersion medium.

[0026] <7> like <6> The sizing agent comprises a powder of the tetrafluoroethylene polymer with an average particle size of 10 to 100 μm, a surfactant, and a liquid dispersion medium, wherein the content of the surfactant is less than 0.01 parts by mass relative to 1 part by mass of the tetrafluoroethylene polymer powder.

[0027] <8> A sizing-treated fiber with a hot-melt tetrafluoroethylene-based polymer attached to its surface.

[0028] <9> like <8> The sizing agent after sizing treatment, wherein the amount of the tetrafluoroethylene polymer attached is 0.1 to 10 parts by weight relative to 100 parts by weight of fiber.

[0029] <10> A prepreg comprising <8> or <9> The document describes sizing-treated fibers and matrix resins.

[0030] <11> A dispersion comprising a powder of a thermally fusible tetrafluoroethylene polymer with an average particle size of 10 to 100 μm, a surfactant, and a liquid dispersion medium, wherein the surfactant content is less than 0.01 parts by mass relative to 1 part by mass of the tetrafluoroethylene polymer powder.

[0031] <12> like <11> The dispersion of the surfactant has a surface tension of less than 28 mN / m.

[0032] <13> like <11> or <12> The dispersion, wherein the surfactant is a silicone surfactant, a fluorinated surfactant, a glycol surfactant, or an alkyl amide ether surfactant.

[0033] <14> like <11> ~ <13> The dispersion of any one of the following, wherein the content of the tetrafluoroethylene polymer is 25 to 60 parts by mass relative to 100 parts by mass of the liquid dispersion medium.

[0034] <15> A sizing agent, which is composed of <11> ~ <14> The dispersion of any one of the following is formed.

[0035] The effects of the invention

[0036] The prepreg of the present invention, comprising sizing treated fibers and matrix resin, exhibits excellent adhesion between the fibers and matrix resin. Furthermore, the prepreg of the present invention provides excellent adhesion between the fibers and matrix resin during molding, resulting in molded articles with suppressed foaming during heat molding, smoothness, and excellent water resistance.

[0037] Furthermore, the present invention provides a dispersion with excellent dispersion stability, comprising a powder of a tetrafluoroethylene-based polymer and a small amount of surfactant. The coated substrate obtained from this dispersion has less surface roughness and a good appearance. Additionally, the coated substrate exhibits good adhesion when bonded to other materials. In particular, by using fibers as a substrate, treating the fibers with a sizing agent formed from the dispersion of the present invention, and impregnating the sizing-treated fibers with a matrix resin, a prepreg with excellent adhesion between the fibers and the matrix resin can be obtained. Detailed Implementation

[0038] The following terms have the following meanings.

[0039] The "average particle size" of the powder is the cumulative 50% diameter of the volume of the object as defined by "D50" below.

[0040] "D50" is the cumulative 50% diameter of an object's volume as determined by laser diffraction and scattering. That is, by measuring the particle size distribution using laser diffraction and scattering, a cumulative curve is obtained with the total volume of the particle group as 100%, and the particle diameter at the point on the cumulative curve where the cumulative volume reaches 50%.

[0041] "D90" is the cumulative 90% diameter of the volume reference of the same measured object.

[0042] The D50 and D90 of the object were determined by dispersing the particles in water and analyzing them using a laser diffraction and scattering method with a laser diffraction and scattering particle size distribution measuring device (LA-920 measuring instrument manufactured by Horiba Seisakusho Co., Ltd.).

[0043] "The melting temperature (melting point) of a polymer" is the temperature corresponding to the maximum value of the melting peak as determined by differential scanning calorimetry (DSC).

[0044] The "5% weight loss temperature of the polymer" is determined according to JIS K7120, using a TGA measuring device, in a nitrogen atmosphere, by heating at a rate of 20°C / min within a temperature range of 23–900°C.

[0045] The glass transition temperature (Tg) of a polymer is a value obtained by analyzing the polymer using the dynamic viscoelasticity assay (DMA).

[0046] The viscosity of the dispersion was measured using a Type B viscometer at 25°C and a rotation speed of 30 rpm. The measurement was repeated three times, and the average of the three measurements was taken.

[0047] The "thixotropic ratio" is calculated by dividing the viscosity η1 measured at 30 rpm of the liquid composition by the viscosity η2 measured at 60 rpm. Each viscosity measurement was repeated three times, and the average of the three measurements was taken.

[0048] "Component sedimentation rate" refers to the value calculated using the following formula, after 18 mL of dispersion is placed into a 30 mL spiral tube and allowed to stand at 25°C for 14 days, based on the overall height of the dispersion and the height of the sedimentation layer (dispersion layer) in the spiral tube before and after standing. If no sedimentation layer is observed after standing and the state remains unchanged, the overall height of the dispersion is considered unchanged, and the component sedimentation rate is 100%. A higher sedimentation rate indicates better dispersion stability.

[0049] Component sedimentation rate (%) = (height of sedimentation layer) / (total height of dispersion) × 100

[0050] In polymers, a "unit" refers to a group of atoms based on one molecule of a monomer, formed through the polymerization of monomers. A unit can be formed directly through a polymerization reaction, or a portion of the unit can be converted into a unit with a different structure by processing the polymer. Hereinafter, units based on monomer A will also be abbreviated as "monomer A unit".

[0051] "Tetrafluoroethylene polymers" refers to polymers containing tetrafluoroethylene-based units.

[0052] The sizing agent of the present invention (hereinafter also referred to as "the sizing agent") contains a powder of a hot-melt tetrafluoroethylene polymer (hereinafter also referred to as "F polymer") with an average particle size of 0.1 to 200 μm.

[0053] By applying this sizing agent to fibers and subjecting them to heat treatment, sizing-treated fibers, preferably sizing-treated carbon fibers, can be obtained. The resulting sizing-treated fibers have an F polymer adhering to their surface.

[0054] When fibers treated with this sizing agent are molded with prepregs or fiber-reinforced composites containing ultra-heat-resistant resin as the matrix resin, decomposition products are less likely to be generated, and foaming during heat molding is suppressed. Therefore, molded products with particularly excellent smoothness, adhesion, and water resistance can be formed.

[0055] While the exact mechanism of action is not yet fully understood, it can be roughly estimated as follows: This sizing agent contains polymer F, which tends to form a denser and more uniform distribution on the surface of sizing fibers treated with this agent. Furthermore, polymer F readily forms microspheres, improving adhesion between the polymer and the sizing fibers and the matrix resin. Additionally, polymer F itself exhibits good heat and water resistance, thus it is not easily decomposed even during high-temperature molding, which contributes to improved properties of the resulting molded product.

[0056] The average particle size (D50) of the F powder in this sizing agent is 0.1 to 200 μm. The D50 of the F powder is preferably 50 μm or less, more preferably 30 μm or less. The D50 of the F polymer is preferably 0.03 μm or more, more preferably 0.1 μm or more.

[0057] Furthermore, the D90 of the F powder is preferably below 10 μm. Within this range of D50 and D90, the flowability of the F powder tends to be good, and the F powder is easily and uniformly distributed on the fiber surface. In addition, the heat resistance and electrical properties (such as low dielectric constant) of the F polymer are most easily exhibited.

[0058] In this sizing agent, from the perspective of ensuring uniform distribution of F powder on the fiber surface, the bulk density of F powder is preferably 0.15 g / m³. 2 The preferred bulk density of F powder is 0.50 g / m³.2 the following.

[0059] The F powder in this sizing agent may also contain resins or inorganic compounds other than the F polymer, but it is preferred that the F powder is the main component. The content of the F polymer in the F powder is preferably 80% by mass or more, and more preferably 100% by mass.

[0060] Examples of such resins include heat-resistant resins such as aromatic polyesters, polyamide-imide, thermoplastic polyimide, polyphenylene ether, and polyphenylene ether.

[0061] Examples of inorganic compounds include silicon dioxide and boron nitride.

[0062] F powder can form a core-shell structure with F polymer as the core and resin or inorganic compound other than F polymer as the shell, or it can form a core-shell structure with F polymer as the shell and resin or inorganic compound other than F polymer as the core.

[0063] The F polymer in this invention is a thermomeltable polymer containing tetrafluoroethylene (hereinafter also referred to as TFE unit)-based units. The fluorine content of the F polymer is preferably 70-76% by mass.

[0064] The melt temperature of polymer F is preferably above 180°C, more preferably above 200°C, even more preferably above 260°C, and particularly preferably above 280°C. The melt temperature of polymer F is preferably below 325°C, more preferably below 320°C. As the melt temperature of polymer F, 180–325°C is preferred, more preferably 260–325°C, and even more preferably 280–325°C. Under these conditions, the heat resistance of the molded article formed from this composition tends to be good.

[0065] The glass transition temperature of polymer F is preferably above 50°C, more preferably above 75°C, more preferably below 150°C, and even more preferably below 125°C. The glass transition temperature of polymer F is preferably 75–125°C, and more preferably 80–100°C.

[0066] Examples of F-polymers include polymers comprising TFE units and perfluoro(alkyl vinyl ether) (PAVE)-based units (PAVE units) (PFA), polymers comprising TFE units and hexafluoropropylene (HFP)-based units (FEP), polymers comprising TFE units and ethylene-based units (ETFE), and thermoplastic polytetrafluoroethylene (PTFE), preferably PFA and FEP, more preferably PFA. The polymers may also contain units based on other comonomers.

[0067] As PAVE, CF2 = CFOCF3, CF2 = CFOCF2CF3 and CF2 = CFOCF2CF2CF3 (hereinafter also referred to as PPVE) are preferred, with PPVE being the most preferred.

[0068] Polymer F preferably has polar functional groups, and more preferably has atomic groups containing oxygen atoms. Polar functional groups can be contained in units within the polymer F or in terminal groups of the polymer backbone. Examples of the latter include polymer F having polar functional groups as terminal groups derived from polymerization initiators, chain transfer agents, etc., and polymer F with polar functional groups obtained by plasma treatment or electrical discharge machining of the polymer F. Among the polar functional groups containing oxygen atoms, hydroxyl groups, carbonyl groups, and phosphonoyl groups are preferred. From the perspective of dispersion stability when this sizing agent is used as a dispersion liquid during fiber sizing, hydroxyl groups and carbonyl groups are more preferred, and carbonyl groups are even more preferred.

[0069] When polymer F contains carbonyl groups, the number of carbonyl groups in polymer F is 1 × 10⁻⁶ relative to the number of carbon atoms in the main chain. 6 The number of carbonyl groups in polymer F is preferably 10 to 5000, more preferably 100 to 3000. The number of carbonyl groups in polymer F can be quantified by means of the polymer composition or by means of the methods described in International Publication No. 2020 / 145133.

[0070] As a hydroxyl-containing group, it is preferred to be a group containing an alcohol hydroxyl group, more preferably -CF2CH2OH, -C(CF3)2OH and 1,2-ethylene glycol group (-CH(OH)CH2OH).

[0071] The carbonyl group is a group containing a carbonyl group (>C(O)). Preferably, the carbonyl group is a carboxyl group, alkoxycarbonyl group, amide group, isocyanate group, carbamate group (-OC(O)NH2), acid anhydride residue (-C(O)OC(O)-), imide residue (-C(O)NHC(O)-, etc.) or carbonate group (-OC(O)O-), and more preferably an acid anhydride residue.

[0072] As F polymers, polymers containing TFE units and PAVE units and having polar functional groups are preferred (1), and polymers containing TFE units and PAVE units and having PAVE units in a mol% ratio of 2.0 to 5.0 mol% relative to all units but without polar functional groups (2).

[0073] The powders of these F polymers not only provide excellent dispersion stability when used as a dispersion liquid, but also facilitate a denser and more uniform distribution on the surface of sizing fibers obtained by treatment with these sizing agents. Furthermore, they readily form microspheres in molded articles, improving adhesion between the sizing agents and the matrix resin. In addition, due to their excellent heat resistance, it is easier to obtain molded articles with excellent appearance (surface smoothness).

[0074] The polymer (1) is preferably a polymer comprising TFE units, PAVE units and units based on monomers having polar functional groups, and more preferably a polymer comprising 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 monomers having polar functional groups relative to all units.

[0075] Furthermore, itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as "NAH") are preferred monomers with polar functional groups.

[0076] As a specific example of polymer (1), the polymer described in International Publication No. 2018 / 16644 can be cited.

[0077] The polymer (2) is preferably composed only of 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 relative to all units. The content of PAVE units in the polymer (2) is preferably 2.1 mol% or more relative to all units, and more preferably 2.2 mol% or more.

[0078] Such polymers have greater molecular conformational freedom, making it easier to enhance the aforementioned mechanisms of action.

[0079] Furthermore, the fact that polymer (2) does not have polar functional groups means that, relative to the number of carbon atoms constituting the polymer backbone, 1 × 10⁻⁶. 6 The polymer has fewer than 500 polar functional groups. Preferably, the number of polar functional groups is less than 100, more preferably less than 50. The lower limit for the number of polar functional groups is typically 0.

[0080] The polymer (2) can be manufactured using polymerization initiators or chain transfer agents that do not generate polar functional groups that become end groups of the polymer chain, or it can be manufactured by fluorinating an F polymer having polar functional groups (such as an F polymer whose end groups of the polymer backbone have polar functional groups from the polymerization initiator). As a method of fluorination, the use of fluorine gas can be cited as an example (see Japanese Patent Application Publication No. 2019-194314, etc.).

[0081] In this sizing agent, it is preferable to use an F polymer that exhibits poor decomposition even at high temperatures. Specifically, the 5% weight loss temperature of the F polymer is preferably above 360°C, more preferably above 400°C. The 5% weight loss temperature of the F polymer is preferably below 600°C.

[0082] By using this F polymer, which exhibits poor decomposition even at high temperatures, bubbling during molding from the prepreg described later can be suppressed, and the appearance of the molded product, such as its smoothness, can be improved.

[0083] This sizing agent can be used as a sizing agent for reinforcing fibers in the technical field of fiber-reinforced plastics, including: glass fibers such as E glass, D glass, L glass, S glass, T glass, Q glass, UN glass, and NE glass; organic fibers such as aramid fibers, polyolefin fibers, modified polyphenylene ether fibers, vinylon fibers, rayon fibers, polyester fibers, and natural fibers; and boron fibers, carbon fibers, and metal fibers.

[0084] The fiber can be in the form of chopped filaments, drapes, rovings, or their felts, woven fabrics, nonwoven fabrics, etc. Furthermore, there are no particular restrictions on the fiber length and cross-sectional shape.

[0085] Preferably, this sizing agent is used as a sizing agent for carbon fiber.

[0086] Carbon fibers can be made from various materials, including pitch-based fibers, rayon-based fibers, polyacrylonitrile (PAN) fibers, single-layer carbon nanotubes, multi-layer carbon nanotubes, and carbon nanofibers. There are no particular restrictions on the fineness, strength, or other physical properties of carbon fibers.

[0087] From the perspectives of operability, engineering feasibility, and mechanical properties, acrylonitrile (PAN) based fibers are preferred. PAN-based carbon fibers are obtained, for example, by subjecting carbon fiber precursor fibers composed of PAN-based polymers to flame-resistant treatment in an oxidizing atmosphere at 200–300°C, followed by pre-carbonization treatment in an inert atmosphere at 500–1200°C, and then carbonization treatment in an inert atmosphere at 1200–2000°C.

[0088] This sizing agent can be in powder or liquid form. The liquid form of this sizing agent is formed from a dispersion (hereinafter also referred to as "this dispersion (1) liquid") containing powder of F polymer with an average particle size of 0.1 to 200 μm and liquid dispersion medium.

[0089] As a method for applying the sizing agent to the fiber, it is preferable to prepare the dispersion (1), attach it to the fiber, and heat it to allow the F polymer to adhere to the fiber surface.

[0090] As the dispersion medium for dispersing F powder in this dispersion (1), it is preferably an aprotic compound that is classified as polar at atmospheric pressure and is in a liquid state at 25 minutes, and more preferably a polar compound selected from amides, ketones and esters.

[0091] If this liquid dispersion medium is used, the dispersion stability of F powder in this dispersion is excellent.

[0092] The boiling point of the liquid dispersion medium is preferably in the range of 50–240°C. Two or more liquid dispersion media can be used together.

[0093] Examples of liquid dispersion media include water, N,N-dimethylformamide, N,N-dimethylacetamide, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide, N-methyl-2-pyrrolidone, γ-butyrolactone, cyclohexanone, cyclopentanone, butyl acetate, methyl isopropyl ketone, and methyl ethyl ketone.

[0094] In this invention, the content of the liquid dispersion medium in the dispersion (1) is preferably 30-90% by mass, more preferably 50-80% by mass.

[0095] In this invention, the content of F powder in the dispersion (1) is preferably 1% by mass or more, and more preferably 5 to 50% by mass, relative to the total mass of the dispersion (1).

[0096] This dispersion (1) may also contain various surfactants added from the perspective of imparting dispersibility. When this dispersion (1) contains surfactants, their content relative to the total mass of this dispersion (1) is preferably 1 to 15% by mass.

[0097] However, the F powder in this invention has excellent dispersion stability, so even without the use of surfactants, this dispersion (1) with excellent dispersion stability and operability can be prepared.

[0098] Anionic, cationic, and nonionic surfactants can be used as surfactants, with nonionic surfactants being preferred.

[0099] The hydrophilic site of the surfactant is preferably a polyoxyethylene or alcohol hydroxyl group. The hydrophobic site of the surfactant is preferably a polyoxyalkylene group formed from an acetylene group, a polysiloxane group, a fluorinated organic group (perfluoroalkyl, etc.), or an alkylene oxide with three or more carbon atoms. As surfactants, acetylene surfactants, silicone surfactants, fluorinated surfactants, alkyl amide ether surfactants, and glycol surfactants are preferred. Two or more of these surfactants may be used. When two or more surfactants are used, silicone surfactants and glycol surfactants are preferred.

[0100] As a silicone surfactant, it is preferred to use the same silicone surfactant as that in the dispersion (2) described later.

[0101] Specific examples of this surfactant include the "Ftergent" series (manufactured by Neos Corporation), the "Surflon" series (manufactured by AGC Seimei Chemical Co., Ltd.), the "MEGA FACE" series (manufactured by DIC Corporation), and the "Unidyne" series (manufactured by Daikin Industries, Ltd.).

[0102] In addition to the above-mentioned components, this dispersion (1) may also contain thixotropic agents, viscosity modifiers, defoamers, silane coupling agents, dehydrating agents, plasticizers, weathering agents, antioxidants, heat stabilizers, lubricants, antistatic agents, whitening agents, colorants, conductive agents, release agents, surface treatment agents, flame retardants, various inorganic fillers, various organic fillers, and other components, within the range that does not impair the effects of the present invention.

[0103] As a specific example of inorganic filler, the same filler that may be included in this dispersion (2) as described later can be cited.

[0104] In addition, from the perspective of improving the adhesion between the sizing agent and the matrix resin, this dispersion (1) may also contain resin materials other than F polymer.

[0105] The resin material can be thermosetting or thermoplastic, and can be modified to be soluble in this dispersion (1) or insoluble but dispersed in this dispersion (1). Examples of suitable resin materials include tetrafluoroethylene polymers other than F polymers, polyimide resins, polyamic acid as a polyimide precursor, polyamide-imide resins, maleimide resins, acrylic resins, phenolic resins, liquid crystal polyester resins, liquid crystal polyesteramide resins, polyolefin resins, modified polyphenylene ether resins, polyfunctional cyanate resins, polyfunctional maleimide-cyanate resins, polyfunctional maleimide resins, vinyl ester resins, urea-formaldehyde resins, diallyl phthalate resins, melamine resins, guanidine resins, melamine-uric acid cocondensation resins, styrene resins, aromatic elastomers, polycarbonate resins, polyarylate resins, polysulfones, polyallyl sulfones, aromatic polyamide resins, aromatic polyetheramides, polyphenylene sulfide, polyaryl ether ketones, polyamide-imide, polyphenylene ether, epoxy resins, etc. Among tetrafluoroethylene polymers other than F polymers, non-thermally meltable polytetrafluoroethylene is preferred from the perspective of improving the electrical properties of the sizing-treated fibers.

[0106] When the dispersion (1) contains resin material, its content is preferably 40% by mass or less relative to the total content of the dispersion (1).

[0107] Non-thermally fusible polytetrafluoroethylene (PTFE) is preferably included in this dispersion (1) as a powder of non-thermally fusible PTFE. With the content of F powder being 1, the content ratio of this powder in this dispersion (1) is preferably 1 or more, more preferably 2 or more. The ratio is preferably 10 or less, more preferably 5 or less.

[0108] The D50 of this powder is preferably 0.1 to 1 μm.

[0109] The viscosity of this dispersion (1) is preferably 75 to 10000 mPa·s. Under this condition, in addition to excellent dispersion stability, its workability and the homogeneity of fiber sizing treatment are easily improved. In addition, this dispersion (1) has higher miscibility with varnishes made of dissimilar resin materials.

[0110] The thixotropic ratio of this dispersion (1) is preferably 1.0 to 2.2, more preferably 1.5 to 2.0. In this case, in addition to excellent dispersion stability, it also has good workability and can easily improve the homogeneity of fiber sizing treatment. In addition, this dispersion (1) has higher miscibility with varnishes made of dissimilar resin materials.

[0111] Examples of methods for applying this sizing agent to fibers (sizing treatment methods) include: roller sizing method in which a portion of a roller is immersed in the dispersion (1), the dispersion (1) is attached to the surface of the roller, and then the fiber is brought into contact with the roller to allow the dispersion (1) to adhere; roller immersion method in which the fiber is directly immersed in the dispersion (1) and the clamping roller is passed through as needed to control the amount of the dispersion (1) adhering; and spraying method in which the dispersion (1) is atomized and sprayed onto the fiber bundle.

[0112] Roller impregnation is preferred because it is easy to apply the dispersion (1) even to each fiber bundle with a large number of individual fibers. In addition, the amount of sizing agent adhering can also be adjusted by adjusting the amount of the remaining dispersion (1) after application.

[0113] The amount of this sizing agent (1) adhering to the fiber, as described later in the heat treatment, is in the range of 0.1 to 10 parts by weight relative to 100 parts by weight of the fiber, more preferably in the range of 0.2 to 5 parts by weight.

[0114] The method for applying this sizing agent to the fiber can be either an intermittent method or a continuous method, but from the perspective of easily suppressing uneven distribution of the sizing agent on the fiber and improving productivity, the continuous method is preferred. Alternatively, the fiber can be vibrated using ultrasound during the application of the sizing agent.

[0115] Preferably, the fiber containing the dispersion (1) is heated to evaporate the dispersion medium, thereby obtaining a sizing-treated fiber with F polymer adhering to its surface. More preferably, the F polymer adhering to the fiber surface is a sintered product of the F polymer. The sizing-treated fiber with the sintered product of the F polymer adhering to its surface is obtained by evaporating the dispersion medium from the fiber containing the dispersion (1) and then heating it to sinter the F polymer.

[0116] The heat treatment for evaporating the dispersion medium is performed by drying the liquid film disposed on the fiber while maintaining the fiber containing the dispersion (1) at the evaporation temperature of the dispersion medium. The heat treatment for sintering the F polymer is performed by maintaining the dried film at a temperature higher than the melting temperature of the F polymer. Thereby, a sintered product of the F polymer is formed on the fiber surface. In addition, the drying temperature usually refers to the temperature of the drying atmosphere.

[0117] During drying, the dispersion medium does not need to be completely evaporated. Specifically, the amount of dispersion medium to be evaporated is preferably 50% or more by mass of the liquid dispersion medium contained in this dispersion (1).

[0118] Drying can be carried out in one step at a constant temperature, or in two or more steps at different temperatures. Drying methods include using an oven, using a ventilated drying furnace, or irradiating with heat rays such as infrared radiation, and can be either contact or non-contact methods.

[0119] Drying can be carried out under either normal or reduced pressure. The drying atmosphere can be any of the following: oxidizing gas atmosphere (oxygen, etc.), reducing gas atmosphere (hydrogen, etc.), or inert gas atmosphere (helium, neon, argon, nitrogen, etc.).

[0120] The preferred drying temperature is 50–280 degrees Celsius. The preferred drying time is 0.1–30 minutes.

[0121] The firing methods for polymer F can include methods using an oven, methods using a ventilated drying furnace, methods using infrared radiation or other heat rays, and methods combining infrared heating and hot air heating.

[0122] The firing of polymer F can be carried out under either atmospheric or reduced pressure. The firing atmosphere can be any of an oxidizing gas atmosphere, a reducing gas atmosphere, or an inert gas atmosphere. The firing temperature is preferably above the melting temperature of polymer F and below the 5% weight reduction temperature of polymer F, typically 300–380°C. The firing time is preferably 30 seconds to 30 minutes, more preferably 1 to 15 minutes.

[0123] If the F polymer is sintered under the above conditions, it is easy to suppress the generation of hydrofluoric acid caused by the decomposition of the F polymer while improving productivity.

[0124] After the dispersion (1) is prepared on the fiber, the dispersion medium can be evaporated by contact drying, for example, by contacting the carbon fiber with a heated roller, and then the F polymer can be sintered. The fiber introduced into the heated roller dries rapidly by being tightly pressed against the heated roller under tension, so that the flat shape of the fiber widened by the heated roller is easily fixed by the sizing agent. The flat fiber has a high fiber opening property because the contact area between individual fibers is small.

[0125] The sizing-treated fibers of the present invention are fibers with F polymer attached to their surface. The definition and scope of F polymer, including its preferred embodiments, are the same as the definition and scope of F polymer in the sizing agent described above.

[0126] The amount of F polymer attached to the sizing treated fiber is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, relative to 100 parts by weight of fiber.

[0127] The sizing-treated fibers of the present invention are preferably obtained from the sizing agent by the same method described above.

[0128] The sizing-treated fibers of the present invention have excellent adhesion to the matrix resin and high impregnation of the matrix resin in the fiber bundle. Therefore, it is easy to obtain prepregs and fiber-reinforced composite materials with excellent mechanical properties from these fibers.

[0129] Hereinafter, a prepreg containing the sizing-treated fibers (hereinafter also referred to as "sizing-treated fibers") of the present invention will be described.

[0130] This prepreg contains the aforementioned sizing-treated fibers and a matrix resin, typically with the matrix resin impregnated in the sizing-treated fibers. The prepreg can be prepared, for example, by impregnating the sizing-treated fibers with a matrix resin or a matrix resin composition and then drying it to allow it to partially cure.

[0131] Specifically, it can be manufactured by a wet process of dissolving the matrix resin or matrix resin composition in a solvent such as methyl ethyl ketone or methanol to reduce its viscosity and thus impregnate it, or by a hot melt process of reducing its viscosity by heating and thus impregnating it.

[0132] In the wet process, sizing fibers can be impregnated in a liquid containing a matrix resin and then lifted out. The solvent is then evaporated using an oven or similar means to produce a prepreg.

[0133] In the hot-melt method, prepregs can be prepared by: directly impregnating a matrix resin or matrix resin composition, which has been reduced in viscosity by heating, into sizing-treated fibers; or, first coating a matrix resin or matrix resin composition onto release paper or the like to form a film, then laminating the film from both sides or one side of the sizing-treated fibers, and heating and pressurizing to impregnate the sizing-treated fibers with the matrix resin. From the perspective of not leaving solvent residue in the prepreg, the hot-melt method is arguably the preferred method.

[0134] Sizing treated fibers can be used in the form of fiber bundles or as sheet-like reinforcing fibers. Sheet-like materials refer to materials in which fibers are aligned in one direction, fibrous materials formed into woven or nonwoven fabrics, and multi-axial fabrics. Sizing treated fibers can be used in the form of continuous or discontinuous fibers. When used as discontinuous fibers, they can be a mixture of fully opened monofilaments and partially opened fiber bundles as reinforcing fibers. Furthermore, fibers can be oriented in the same direction, or disordered mats oriented in random directions can be used.

[0135] There is no particular limitation on the thickness of the fibers formed into sheets. If it is for laminated board applications, the thickness is preferably in the range of 0.01 to 0.2 mm. From the perspective of dimensional stability, fabrics that have undergone super-opening or filling treatment are suitable.

[0136] Thermosetting resins or thermoplastic resins can be used as the base resin.

[0137] Examples of thermosetting resins include epoxy resins, unsaturated polyester resins, phenolic resins, vinyl ester resins, cyanate ester resins, polyurethane acrylate resins, phenoxy resins, alkyd resins, polyurethane resins, prepolymers of maleimide and cyanate ester resins, bismaleimide resins, polyimide resins with acetylene terminals and polyisoimide resins, and polyimide resins with nadic acid terminals. These thermosetting resins can be used alone or in combination of two or more. Furthermore, thermosetting resins can be thermosetting resin compositions containing various additives in addition to curing agents and curing accelerators.

[0138] Examples of thermoplastic resins include polysulfone, polyphenylsulfone, polyethersulfone, aromatic polyetherketones (polyetherketone, polyetheretherketone, polyetherketoneketone, polyetheretherketoneketone, etc.), polyamides, aromatic polyesters, aromatic polycarbonates, polyetherimides, polyarylates, thermoplastic polyimides, polyamide-imides, polyacetals, polyphenylene ethers, polyphenylene sulfides, liquid crystal polyesters, polyarylates, polyacrylonitrile, and polybenzimidazole. These thermoplastic resins can be used alone or in combination of two or more. Furthermore, thermoplastic resins can also be thermoplastic resin compositions containing various additives.

[0139] When thermosetting or thermoplastic resins are used as resin compositions, various additives include plasticizers, weather resistant agents, antioxidants, heat stabilizers, lubricants, antistatic agents, whitening agents, colorants, conductive agents, release agents, surface treatment agents, flame retardants, various inorganic fillers, and various organic fillers.

[0140] The matrix resin is preferably a heat-resistant resin selected from polysulfone, polyphenylsulfone, polyethersulfone, aromatic polyetherketone, polyetherimide, polyphenylene sulfide, and liquid crystal polyester. These are classified as ultra-heat-resistant resins, also known as super engineering plastics, which are more likely to enhance the effect of this sizing treatment on the fibers.

[0141] When the matrix resin has polar functional groups such as carbonyl, sulfone or ester groups in its structure and the F polymer of the present invention also has polar functional groups, it is presumed that the polar functional groups in the matrix resin and the polar functional groups in the F polymer interact, resulting in high adhesion, which is therefore preferred.

[0142] The fiber mass fraction in the prepreg is preferably 40-90% by mass, more preferably 50-80% by mass. If it is within the above range, the mass of the obtained fiber-reinforced composite material will not become excessive, and the advantages of the fiber-reinforced composite material with excellent specific strength and specific modulus of elasticity can be brought into play.

[0143] Prepregs containing fibers treated with this sizing agent can easily be impregnated with the matrix resin to be compounded, resulting in a high-quality material with less uneven mechanical properties.

[0144] Prepregs containing such reinforcing fibers may also contain various additives without compromising their original purpose.

[0145] The prepreg of the present invention, containing sizing treated fibers and matrix resin, has excellent adhesion to the matrix resin and a high impregnation rate of the matrix resin in the fibers, thus producing a fiber-reinforced composite material with excellent mechanical properties after molding.

[0146] When using this prepreg to form fiber-reinforced composite materials, a method can be used to form the laminate by laminating the prepreg and simultaneously heating the matrix resin under pressure. Methods of heating and pressurizing include pressure molding, autoclave molding, bagging molding, winding tape molding, and internal pressure molding. Winding tape molding and internal pressure molding are particularly preferred for sporting goods. For aircraft applications requiring higher quality and performance laminated composite materials, autoclave molding is preferred. For various vehicle exteriors, pressure molding is preferred.

[0147] In addition, when using this prepreg to form fiber-reinforced composite materials, resin transfer molding, filament winding molding, sheet winding molding, etc., can also be used.

[0148] Furthermore, by laminating the aforementioned prepregs and placing a metal substrate on one or both sides, a metal-clad laminate can be obtained. Specifically, the metal-clad laminate can be manufactured by laminating one or more sheets of the aforementioned prepregs, placing a metal substrate on one or both sides of the prepregs, and then laminating them. The metals constituting the metal substrate include iron, stainless steel, aluminum, copper, brass, nickel, zinc, titanium, and alloys of these metals.

[0149] The forming conditions can employ the methods commonly used for laminated and multilayer boards in printed circuit boards. For example, multi-stage presses, multi-stage vacuum presses, continuous forming machines, and autoclave forming machines can be used, with temperatures ranging from 180 to 350°C, heating times from 100 to 300 minutes, and surface pressures from 20 to 100 kg / cm². 2 Lamination is performed to produce metal-clad laminates.

[0150] Fiber composite materials can also be laminated with other substrates. Examples of other substrates include heat-resistant resin films and prepregs that serve as precursors for fiber-reinforced resin boards. Examples of fiber composite materials include fiber-reinforced composite materials having a heat-resistant resin film layer and fiber-reinforced composite materials having a prepreg layer.

[0151] A heat-resistant resin film is a film containing one or more heat-resistant resins. Examples of heat-resistant resins include those described above.

[0152] As a lamination method, one example is the hot pressing of a laminate obtained by heating a prepreg laminate with other substrates.

[0153] When other substrates are prepregs, the preferred hot pressing conditions are a temperature of 120–400°C, an atmosphere pressure of less than 20 kPa (vacuum), and a pressurization pressure of 0.2–10 MPa.

[0154] The fiber-reinforced composite material of this invention is suitable for applications requiring strength, abrasion resistance, chemical resistance, and flame retardancy. Examples include the interior and exterior trim of transportation equipment such as automobiles, two-wheeled vehicles, and aircraft; sliding parts such as gears and bearings; insulating parts; sporting goods such as rackets and bats; components of industrial machinery, robots, and medical equipment; oil drilling equipment; oil hoses; hydrogen storage tanks; hydrogen storage pressure vessels; and wind turbine blades.

[0155] Furthermore, the fiber-reinforced composite material of the present invention and the above-described laminate can also be used as low-vibration components. Examples of components requiring low vibration include rotating parts of motors, rotating parts of compressors, rotating parts of machine tools (lathes, milling machines, etc.), and interior and exterior trim of transportation equipment such as automobiles, two-wheeled vehicles, and aircraft.

[0156] Furthermore, since the fiber-reinforced composite material of the present invention has excellent mechanical properties at low temperatures, it can be used in components used at extremely low temperatures, such as liquid hydrogen tanks.

[0157] The average particle size of the F powder in this sizing agent is more preferably 10 to 100 μm. A dispersion containing F powder of this average particle size, a surfactant, and a liquid dispersion medium, wherein the surfactant content is less than 0.01 parts by mass relative to 1 part by mass of F powder of this average particle size (hereinafter also referred to as this dispersion (2)) exhibits particularly excellent dispersion stability and is suitable for use as this sizing agent. In addition, this dispersion (2) can also be used for purposes other than this sizing agent based on its characteristics.

[0158] The average particle size (D50) of the F powder in this dispersion (2) is 50 μm or less, preferably 40 μm or less. In addition, the average particle size of the F powder in this dispersion (2) is preferably 20 μm or more.

[0159] Furthermore, from the perspective of the dispersibility of this dispersion (2), the D90 of the F powder in this dispersion (2) is preferably 40 μm or more, more preferably 60 μm or more. Furthermore, the D90 of the F powder in this dispersion (2) is preferably 100 μm or less, more preferably 90 μm or less.

[0160] F powder has low surface energy and its powder particles are prone to agglomeration. Therefore, this dispersion (2) contains a surfactant. The surfactant content is less than 0.01% of 1 part by mass of F powder. The average particle size of F powder in this dispersion (2) is relatively large and the surface area is small. Therefore, a small amount of surfactant can be used to achieve high stabilization and dispersion in the dispersion medium. Thus, the dispersion (2) has excellent dispersion stability.

[0161] Furthermore, the surfactant content in this dispersion (2) is less than that in the F powder, therefore, when used in the manufacture of the coating substrate described later, the resulting coating substrate has less surface roughness and a better appearance. In addition, the resulting coating substrate exhibits excellent adhesion when bonded to other materials. In particular, when fibers are used as the substrate, and the fibers are treated with the sizing agent formed from this dispersion (2) and impregnated with the matrix resin, a prepreg with excellent adhesion can be obtained.

[0162] From the perspective of the surface appearance of the resulting coated substrate, the content of surfactant in this dispersion (2) is preferably 0.008 or less, more preferably 0.005 or less, relative to 1 part by mass of F powder. In addition, from the perspective of dispersibility, the content of surfactant is preferably 0.0001 or more, relative to 1 part by mass of F powder.

[0163] As the surfactants mentioned above, silicone surfactants, fluorinated surfactants, glycol surfactants, and alkyl amide ether surfactants are preferred. Two or more of these surfactants may be used. When using two or more surfactants, their total content should be within the range mentioned above. When using two or more surfactants, silicone surfactants and glycol surfactants are preferred.

[0164] The surface tension of the surfactant is preferably below 28 mN / m, more preferably below 26 mN / m. The surface tension of the surfactant is preferably above 20 mN / m. The surfactant is preferably a nonionic surfactant.

[0165] Silicone surfactants are surfactants in which a portion of a silicone, whose main backbone consists of alternating silicon and oxygen siloxane bonds, is introduced with hydrophilic substituents. Examples include organopolysiloxanes, polyether-modified polysiloxanes, polyester-modified polysiloxanes, aralkyl-modified polysiloxanes, and acrylic-modified polysiloxanes.

[0166] Fluorinated surfactants are surfactants that have a hydrophilic portion containing hydroxyl, carboxyl, sulfonyl, or groups derived from these groups, and a hydrophobic portion containing fluorinated organic groups. Examples include the "Ftergent" series (manufactured by Neos Corporation, Ftergent is a registered trademark), the "Surflon" series (manufactured by AGC Seimei Chemical Co., Ltd., Surflon is a registered trademark), the "MEGA FACE" series (manufactured by DIC Corporation, MEGA FACE is a registered trademark), and the "Unidyne" series (manufactured by Daikin Industries, Ltd., Unidyne is a registered trademark).

[0167] Diol surfactants are surfactants formed by the bonding of hydrophilic sites such as hydroxyl and ester groups with hydrophobic sites such as hydrocarbon groups. Examples include monoalkyl glycol ethers, monoaryl glycol ethers, monoalkyl glycol ether acetates, and monoaryl glycol ether acetates.

[0168] Alkylamide ether surfactants are nonionic surfactants formed by the bonding of carboxylic acids and polyoxyalkylamines. Examples include polyoxyethylene alkylamides and polyoxyethylene oleamides.

[0169] Among the surfactants mentioned above, silicone surfactants are preferred from the perspective of dispersion stability of this dispersion.

[0170] Among silicone surfactants, organopolysiloxanes are preferred, especially polyether-modified polysiloxanes, polyester-modified polysiloxanes, aralkyl-modified polysiloxanes, or acrylic-modified polysiloxanes.

[0171] Organopolysiloxanes may have an organopolysiloxane structure in their main chain, in their side chains, or in both their main chain and side chains. Preferably, the organopolysiloxane is a linear polymer. More preferably, it is a polydiorganosiloxane.

[0172] The organopolysiloxane is preferably a dimethylsiloxane unit ((CH3)2SiO) 2 / 2 The organopolysiloxane, more preferably an organopolysiloxane containing dimethylsiloxane units in the main chain and having polyoxyethylene at the end of the main chain (1), or an organopolysiloxane containing dimethylsiloxane units and formula (R) 1 (R) 2 SiO 2 / 2 The term represents an organopolysiloxane with two organosiloxane units (2). R in the formula... 1 The denoting alkyl group is preferred, with methyl being the most common. Furthermore, R in the formula... 2 This indicates the presence of a polyoxyethylene group, more preferably of the formula -X. 2 -OY 2 -Z 2 The group represented by X (where X is a radical) 2 It is an alkylene group, Y 2 It is a polyoxyalkylene group, Z 2 (It can be any one of a hydrogen atom, an alkyl group, or an acyl group).

[0173] The polyoxyalkylene contained in organopolysiloxane (1) or (2) may consist of only one alkenyl oxide or two or more alkenyl oxides. In the latter case, the different alkenyl oxides may be randomly linked or block-linked. The alkenyl oxides in the polyoxyalkylene are preferably oxyvinyl or oxypropylene groups.

[0174] The number of oxidized alkenyl units (degree of polymerization) in the polyoxyethylene is preferably 2 or more. The number of oxidized alkenyl units is preferably 100 or less, more preferably 50 or less, and even more preferably 20 or less.

[0175] The degree of polymerization of the organopolysiloxane is preferably 2 or higher. The degree of polymerization of the organopolysiloxane is preferably 1000 or lower, more preferably 100 or lower, and even more preferably 50 or lower.

[0176] The ratio of the number of dimethylsiloxane units to the number of diorganosiloxane units (degree of polymerization) in the organopolysiloxane (2) is preferably greater than 1. This ratio is preferably 20 or less.

[0177] The weight-average molecular weight of the organopolysiloxane is preferably 300 to 100,000, more preferably 500 to 10,000, and even more preferably 500 to 2,000.

[0178] The HLB content of organopolysiloxanes is preferably 8 to 18.

[0179] The HLB value is calculated using the Griffin formula, which is the sum of the molecular weights of the hydrophilic parts divided by the molecular weight and then multiplied by 20. In the case of organopolysiloxanes (1) or (2), the polyoxyethylene in the organopolysiloxane is the hydrophilic part, and the HLB value is 20 times the value obtained by dividing the molecular weight of the polyoxyethylene by the molecular weight of the organopolysiloxane.

[0180] Specific examples of organopolysiloxanes include “BYK-347”, “BYK-349”, “BYK-378”, “BYK-3450”, “BYK-3451”, “BYK-3455”, “BYK-3456” (manufactured by BYK Chemical Japan Co., Ltd.), “KF-6011”, and “KF-6043” (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0181] The boiling point of the liquid dispersion medium in this dispersion (2) is preferably above 75°C, more preferably above 100°C. The boiling point of the dispersion medium is preferably below 300°C, more preferably below 250°C.

[0182] The liquid dispersion medium can be water or a non-aqueous liquid dispersion medium, preferably a liquid dispersion medium selected from water, alcohol, amide, ketone, ester and hydrocarbon.

[0183] The non-aqueous liquid dispersion medium can be fluorinated or unfluorinated. Preferably, the alcohol is methanol, ethanol, isopropanol, butanol, or hexanol. Preferably, the amide is dimethylformamide, acetanilide, or N-methyl-2-pyrrolidone. Preferably, the ketone is acetone, methyl ethyl ketone, diisobutyl ketone, or methyl isobutyl ketone. Preferably, the ester is ethyl acetate, butyl acetate, ethyl benzoate, or butyl benzoate. Preferably, the hydrocarbon is pentane, hexane, heptane, octane, toluene, or xylene.

[0184] The liquid dispersion medium may also be a mixture of two or more. From the perspective of suppressing the decrease in the uniformity of the component distribution or the formation of voids in the molded body obtained by using this dispersion (2), it is preferable to degas the liquid dispersion medium.

[0185] Water is more preferred among these liquid dispersion media.

[0186] From the perspective of efficiently coating the substrate with a large amount of F powder when manufacturing the substrate described later, the amount of F powder in this dispersion (2) is preferably 25 to 100 parts by mass relative to 100 parts by mass of the liquid dispersion medium. Generally, F powder has a low surface energy and is prone to agglomeration, so the amount of F powder in the dispersion is controlled at a low level. However, even if the amount of F powder is increased, the dispersion stability of this dispersion (2) is very good. Therefore, even if the amount of F powder in the dispersion is increased, the stability of the dispersion and its impregnation and coating properties on the substrate are very good. Even if a large amount of F powder is coated or impregnated on the substrate, a substrate with excellent surface appearance can be obtained. From the above perspective, the amount of F powder in this dispersion (2) is more preferably 40 parts by mass or more relative to 100 parts by mass of the liquid dispersion medium.

[0187] This dispersion (2) is obtained by mixing F powder, a specified amount of surfactant, and a dispersion medium. Examples of mixing methods include mixing F powder, a specified amount of surfactant, and a dispersion medium together, or pre-mixing a specified amount of surfactant and dispersion medium and then adding F powder to it. The addition can be a one-time process, or it can be continuous or intermittent.

[0188] Examples of mixing equipment used for mixing include mixers with stirring blades, Henschel mixers, belt mixers, rocking mixers, and vibratory mixers.

[0189] The mixing method can be either intermittent or continuous.

[0190] As mixers for intermittent mixing, Henschel mixers, pressure kneaders, Banbury mixers, and planetary mixers are preferred.

[0191] The mixing temperature of powder F, a specified amount of surfactant, and dispersion medium is not particularly limited, but is generally above 20°C, as long as it allows for uniform dispersion of powder F. Furthermore, mixing is carried out at a temperature lower than the boiling point of the dispersion medium, preferably below 100°C.

[0192] This dispersion (2) may also contain at least one of inorganic fillers and aromatic polymers (hereinafter also referred to as the third component).

[0193] When inorganic coatings are present, the electrical properties and low linear expansion of the molded articles obtained by coating the substrate with this dispersion (2) tend to be better.

[0194] When containing aromatic polymers, the adhesion and UV processability of the molded articles obtained by coating the dispersion (2) onto the substrate tend to be better.

[0195] From the above perspective, as inorganic fillers, nitride fillers and inorganic oxide fillers are preferred, boron nitride fillers, aluminum nitride fillers, beryllium oxide fillers (beryllium oxide fillers), silica fillers, wollastonite fillers, talc fillers and other silicate fillers are more preferred, as well as cerium oxide, aluminum oxide, magnesium oxide, zinc oxide, titanium oxide and other metal oxide fillers, with silica fillers being even more preferred.

[0196] Inorganic fillers are preferably surface-treated with silane coupling agents.

[0197] 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.

[0198] Inorganic fillers can be granular, needle-like (fibrous), or plate-like in shape. Specific shapes of inorganic fillers include spherical, scaly, layered, leaf-like, almond-shaped, columnar, cockscomb-shaped, equiaxed, leaf-like, mica-like, blocky, flat, wedge-shaped, rosette-shaped, mesh-like, and square columnar.

[0199] Preferred examples of inorganic fillers include silica fillers (such as the "admafin" series manufactured by Admatex Co., Ltd.), zinc oxide surface-treated with esters such as propylene glycol didecanoate (such as the "FINEX" series manufactured by Sakai Chemical Industry Co., Ltd.), spherical fused silica (such as the "SFP" series manufactured by Denka Co., Ltd.), titanium dioxide coated with polyols and inorganic substances (such as the "TIPAQUE" series manufactured by Ishihara Sangyo Co., Ltd.), and rutile titanium dioxide surface-treated with alkylsilanes (such as those manufactured by Teika Co., Ltd.). Products include: JMT (registered trademark) series, hollow silica fillers (E-SPHERES series produced by Pacific Cement Corporation, SiliNax series produced by Nippon Steel Mining Corporation, Eccospheres series produced by Emerson Cumming Corporation, talc fillers (SG series produced by Nippon Talc Corporation, etc.), block talc fillers (BST series produced by Nippon Talc Corporation, etc.), and boron nitride fillers (UHP series produced by Showa Denko Corporation, Denka Boron Nitride series (GP, HGP grade) produced by Denka Corporation, etc.).

[0200] As aromatic polymers, aromatic elastomers such as aromatic polyimides, aromatic polyamides, aromatic polyamide-imides, aromatic maleimides, and styrene elastomers, as well as aromatic polyamic acids, are preferred; more preferably, aromatic elastomers such as aromatic polyimides, aromatic polyamide-imides, aromatic maleimides, polyphenylene ethers, and styrene elastomers are preferred; and even more preferably, aromatic polyimides, aromatic polyamide-imides, and aromatic polyamic acids are preferred. Aromatic polyimides can be thermoplastic or thermosetting. Thermoplastic polyimides refer to polyimides that have undergone imidization and will not undergo further imidization reactions.

[0201] Specific examples of aromatic polyimides include the "Neopulim" series (manufactured by Mitsubishi Gas Chemical Co., Ltd.), the "SPIXAREA" series (manufactured by Somaron Co., Ltd.), the "Q-PILON" series (manufactured by PI Technology Research Institute), the "WINGO" series (manufactured by WINGO Technology Co., Ltd.), the "Tohmide" series (manufactured by T&K TOKA Co., Ltd.), the "KPI-MX" series (manufactured by Kawamura Sangyo Co., Ltd.), and the "UPIA-AT" series (manufactured by Ube Industries Co., Ltd.).

[0202] Specific examples of aramid polyamide imides include "HPC-1000" and "HPC-2100D" (both manufactured by Showa Denko Materials Co., Ltd.).

[0203] Examples of styrene elastomers include styrene-butadiene copolymers, hydrogenated styrene-butadiene copolymers, hydrogenated styrene-isoprene block copolymers, styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, hydrides of styrene-butadiene-styrene block copolymers, and hydrides of styrene-isoprene-styrene block copolymers.

[0204] The dispersion (2) may also contain non-thermally fusible polytetrafluoroethylene (PTFE) powder as a third component. In this case, the electrical properties of the molded article formed from the dispersion (2) tend to be better. The mass ratio of the content of this powder in the dispersion (2) is preferably 0.5 or more, more preferably 1 or more, with the content of F powder being 1. The above ratio is preferably 10 or less, more preferably 5 or less.

[0205] The D50 of this powder is preferably 0.1 to 1 μm.

[0206] When mixing the third component, the mixing method may be the same as that described above.

[0207] When mixing the third component, it can be added at any stage of preparing the dispersion. For example, the third component can be pre-mixed with the F powder and / or a specified amount of surfactant, or it can be added while mixing the F powder, the specified amount of surfactant, and the dispersion medium. Alternatively, a pre-obtained mixture of the F powder, the specified amount of surfactant, and the dispersion medium can be mixed with a mixture of the third component and the dispersion medium, or the third component can be added to the dispersion after it has been obtained. It can be added all at once or in stages, continuously or intermittently.

[0208] The sedimentation rate of the components in the dispersion (2) obtained above is preferably 60% or more, more preferably 70% or more. The upper limit of the sedimentation rate is 100%. Due to the above-mentioned mechanism, the dispersion stability of the dispersion (2) tends to be good.

[0209] From the perspective of the coatability or impregnation of the substrate during the manufacturing of the coating substrate, as described later, the viscosity of the dispersion (2) obtained above is preferably 10 mPa·s or more, more preferably 20 mPa·s or more. The viscosity of the dispersion (2) is preferably 100,000 mPa·s or less, more preferably 10,000 mPa·s or less, and even more preferably 2,000 mPa·s or less. The viscosity of the dispersion (2) can be adjusted to the desired range by controlling the amount of F powder, the type and amount of the dispersion medium.

[0210] The thixotropic ratio of this dispersion (2) is preferably 1.0 to 2.2. This dispersion (2) with this thixotropic ratio has excellent coatability, impregnation and homogeneity. The thixotropic ratio is calculated by dividing the viscosity of this dispersion (2) measured at a rotation speed of 30 rpm by the viscosity of this dispersion (2) measured at a rotation speed of 60 rpm.

[0211] From the perspective of suppressing the decrease in uniformity of component distribution or the formation of voids in the molded article obtained from this dispersion (2), the foam volume fraction in this dispersion (2) is preferably less than 10%, more preferably less than 5%. The foam volume fraction is preferably 0% or more.

[0212] The foam volume fraction is determined by measuring the volume (V) of the dispersion (2) at standard atmospheric pressure and 20°C. N ) and the combined volume of the foam (V) when the pressure is reduced to 0.003 MPa V The value is obtained according to the following formula.

[0213] Foam volume fraction [%] = 100 × (V V -V N ) / V N

[0214] When the solid component of this dispersion (2) contains the aforementioned third component, these third components are also included in the solid component. The solid component of this dispersion (2) includes other insoluble components besides the F powder. With the total mass of the dispersion as 100% by mass, the concentration of the solid component is preferably 25% by mass or more, more preferably 50% by mass or more. From the perspective of the dispersibility of this dispersion (2), the concentration of the solid component is preferably 80% by mass or less, more preferably 60% by mass or less. With the total mass of the solid component as 100% by mass, the amount of F powder in the solid component is preferably 50% by mass or more, more preferably 70% by mass or more. Furthermore, the amount of F powder in the solid component is preferably 99% by mass or less.

[0215] In addition to the above-mentioned components, this dispersion (2) may also contain thixotropic agents, viscosity modifiers, defoamers, silane coupling agents, dehydrating agents, plasticizers, weathering agents, antioxidants, heat stabilizers, lubricants, antistatic agents, whitening agents, colorants, conductive agents, mold release agents, surface treatment agents, flame retardants, various organic fillers and other components.

[0216] When the dispersion (2) is brought into contact with a substrate and fired to form a layer composed of polymer F (hereinafter also referred to as "F layer"), a coated substrate covered by the F layer can be obtained. Examples of contact methods include: coating the dispersion (2) onto the surface of the substrate, immersing the substrate in the dispersion (2), impregnating the dispersion (2) in the substrate, spraying the dispersion (2) onto the substrate, etc.

[0217] Examples of substrates include metal foil, resin film, woven fabric, nonwoven fabric, and fiber. Preferred forms of coating substrates include a metal-coated laminate comprising a metal foil and an F layer formed on at least one surface thereon, a multilayer film comprising a resin film and an F layer formed on at least one surface thereon, and a coated fabric in which the dispersion (2) is impregnated in woven or nonwoven fabric and the fibers in the woven or nonwoven fabric are coated with the F layer. Alternatively, fibers may be directly contacted with the dispersion (2) and fired to coat the fibers with the F polymer.

[0218] The F layer can cover the entire surface of the substrate or only a portion thereof, as long as the F polymer adheres to the surface of the substrate. The F layer can be porous.

[0219] Examples of metal substrates that can be used as metal foils include those made of copper, nickel, aluminum, titanium, and their alloys. Examples of resin films that can be used as prepregs for fiber-reinforced resin substrates include: polyimide, polyarylate, polysulfone, polyallyl sulfone, polyamide, polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamide-imide, liquid crystal polyester, liquid crystal polyesteramide, F polymers, and non-thermally fusible tetrafluoroethylene polymers. Among the F polymers and non-thermally fusible tetrafluoroethylene polymers in the resin film, PTFE, PFA, and FEP are preferred. The shapes of these metal foils or resin films can be planar, curved, uneven, or any of the following: foil, plate, film, or fibrous.

[0220] Specific examples of the coated substrate include metal-clad laminates having a metal foil and an F layer on at least one surface of the metal foil, and multilayer films having a polyimide film and F layers on both surfaces of the polyimide film. These laminates possess excellent electrical and other physical properties, making them suitable as printed circuit board materials. Specifically, these laminates can be used to manufacture flexible printed circuit boards and rigid printed circuit boards.

[0221] The metal foil is preferably copper foil. Metal-clad laminates with copper foil as the substrate are particularly useful as printed circuit board materials.

[0222] The ten-point average roughness of the metal foil surface is preferably 0.01 to 0.05 μm.

[0223] The resin film is preferably a polyimide film or an F polymer film. Multilayer films based on such films can be used as wire coating materials and printed circuit board materials.

[0224] When manufacturing a metal-clad laminate or a multilayer film with an F layer, the F layer can be formed on at least one surface of the substrate. The F layer can be formed on only one side of the substrate or on both sides. The surface of the substrate can be treated with a silane coupling agent or similar agent. When coating this dispersion, various coating methods can be used, including spray coating, roller coating, spin coating, gravure coating, microgravure coating, gravure offset coating, blade coating, touch coating, bar coating, die coating, Mayer wire-wound bar coating, and slot die coating.

[0225] By impregnating the dispersion (2) into a fabric and then heating and drying it, a sizing-treated coated fabric with the fabric coated with layer F can be obtained. Preferably, the fabric is made of glass fiber, carbon fiber, aramid fiber, or metal fiber, with glass fiber and carbon fiber being more preferred. Examples of methods for impregnating the dispersion (2) into the fabric include immersing the fabric in the dispersion (2) and coating the fabric with the dispersion.

[0226] By contacting the dispersion (2) with the fiber surface and firing it, the F layer is attached to the fiber surface, resulting in coated fibers with the F layer. Examples of fibers that are the same as the reinforcing fibers that can use the sizing agent described above can be cited.

[0227] By coating the fibers with layer F, a sizing effect that inhibits fiber breakage and fuzzing can be obtained. When using this dispersion (2) as a sizing agent, necessary additives can be added to this dispersion (2) according to the type of fiber used. Fibers treated with this dispersion (2) exhibit excellent heat resistance and adhesion to other polymers.

[0228] Preferably, the surface tension of the substrate is greater than that of the surfactant. In this case, the substrate is easily wetted by the dispersion (2), and the surface of the coated substrate is less likely to become rough. The surface tension of the substrate is preferably 5 mN / m or more higher than that of the surfactant, more preferably 10 mN / m or more higher. For example, when the surface tension of the surfactant is 28 mN / m or less, a surface tension of 35 mN / m or more is particularly preferred.

[0229] The F layer is preferably formed by heating to remove the dispersion medium followed by sintering the F polymer. The temperature for removing the dispersion medium is preferably below the boiling point of the dispersion medium, more preferably 50 to 150°C below the boiling point. For example, when using N-methyl-2-pyrrolidone with a boiling point of approximately 200°C, heating to below 150°C is preferred, and heating to 100 to 120°C is preferred. Similarly, when using water with a boiling point of approximately 100°C, heating to below 90°C is preferred, and heating to 70 to 80°C is preferred. It is preferable to blow air into the dispersion medium during the removal process.

[0230] After removing the dispersion medium, the substrate is preferably heated to the firing temperature range of the F polymer to form the F layer, for example, the polymer is preferably fired in the range of 300 to 400°C. The F layer preferably comprises a fired product of the F polymer.

[0231] As described above, the F layer is formed through a process of contacting the dispersion (2) with the substrate, a process of removing the dispersion medium, and a process of firing the F polymer. These processes can be performed once or more. For example, the dispersion (2) is coated onto the substrate, and the dispersion medium is removed by heating to form a film. The dispersion (2) can be coated again on the formed film, the dispersion medium can be removed by heating, and then the F polymer can be fired by heating to form the F layer. From the perspective of easily obtaining a thick film with excellent appearance, the processes of coating, drying, and firing of the dispersion (2) can be performed twice.

[0232] The thickness of the F layer is preferably 0.1 μm or more, more preferably 1 μm or more. The upper limit of the thickness is 200 μm. Within this range, it is easy to form an F layer with excellent crack resistance.

[0233] The peel strength between the F layer and the substrate is preferably 10 mN / m or more, more preferably 15 mN / m or more. The peel strength is preferably 100 mN / m or less. By using this dispersion (2), such a laminate can be easily formed without impairing the physical properties of the F polymer in the F layer.

[0234] The porosity of layer F is preferably 20% or less, more preferably 10% or less. The porosity is preferably 0.1% or more. Furthermore, the porosity is a percentage (%) calculated by dividing the area occupied by the porosity portion by the area of ​​layer F, based on an SEM image of the cross-section of the molded article observed using a scanning electron microscope (SEM). The porosity portion is determined by image processing. The area occupied by the porosity portion is calculated by approximating the porosity portion as a circle.

[0235] As a structure of metal-clad laminates or multilayer films, examples include substrate / F layer / substrate / F layer / substrate, substrate / substrate / F layer / substrate / substrate, etc. The substrates can be the same or different, and the substrate or F layer may also contain glass cloth or fillers.

[0236] This metal-clad laminate can be used for antenna components, printed circuit boards, aircraft components, automotive components, sporting goods, food industry supplies, heat dissipation components, coatings, cosmetics, etc. Specifically, it can be used as wire sheathing material for aircraft wires, enameled wire sheathing material for motors in electric vehicles, electrical insulating tape, oil drilling insulating tape, printed circuit board materials, separation membranes such as precision filtration membranes, ultrafiltration membranes, reverse osmosis membranes, ion exchange membranes, dialysis membranes, and gas separation membranes, electrode adhesives for lithium secondary batteries and fuel cells, copier rollers, covers for furniture, automotive dashboards, and household appliances, load bearings, sliding shafts, valves, bearings, gears, cams, sliding parts for conveyor belts and food conveyor belts, tools such as shovels, files, awls, and saws, boilers, hoppers, pipes, ovens, baking molds, chutes, plastic molds, toilets, container coating, power devices, transistors, thyristors, rectifiers, transformers, power MOSFETs, CPUs, heat sinks or metal heat sinks.

[0237] More specifically, it can be used as a housing for personal computers and monitors, electronic equipment materials, automotive interior and exterior trim, sealing materials for processing machines that undergo heating treatment under low oxygen conditions, vacuum furnaces, plasma processing devices, etc., and heat dissipation components in processing units such as sputtering or various dry etching devices.

[0238] In addition, this dispersion (2) can also be used for impregnating the insulating layer of printed wiring boards, thermal interface materials, power module substrates, coils used in power devices such as motors, and forming a thermally conductive and heat-resistant coating after drying; for bonding ceramic and metal parts together in vehicle engines; or for imparting corrosion resistance to heat exchangers or the fins or tubes constituting heat exchangers.

[0239] Furthermore, this dispersion (2) is suitable for use as a sizing agent. When this dispersion (2) is used as a sizing agent, the fibers coated with the F layer have an excellent appearance. Therefore, the adhesion between the reinforcing fibers and the matrix resin in fiber-reinforced plastics containing reinforcing fibers and matrix resin is improved. Thus, the prepreg containing sizing-treated fibers and matrix resin obtained by contacting the fibers with this dispersion (2) has excellent mechanical properties. In addition, due to the excellent heat resistance of the F layer, the surface smoothness tends to improve even when processed at high temperatures.

[0240] Examples of reinforcing fibers include the same fibers described above, with carbon fiber, glass fiber, aramid fiber, and boron fiber being preferred.

[0241] The same matrix resin as that used in this prepreg can be used as the matrix resin.

[0242] Because of the excellent heat resistance of the F layer, it is not easy to decompose when heating is used to form the prepreg or to further process the prepreg, and the surface smoothness of the prepreg and its processed products tends to be better.

[0243] As a method for manufacturing prepreg obtained from this dispersion (2), a manufacturing method that is the same as the method for manufacturing prepreg obtained from the above-described dispersion (1) can be cited.

[0244] The prepreg obtained from this dispersion (2) can be further shaped into a fiber-reinforced composite material by the same method as described above for shaping this prepreg into a fiber-reinforced composite material.

[0245] As described above, this dispersion (2) exhibits excellent dispersion stability, and the surface appearance of the substrate coated with the F layer using this dispersion (2) is excellent, as is its adhesion to other substrates. In particular, by using this dispersion (2) to coat fibers with the F layer, a sizing effect that suppresses fiber breakage and fuzzing can be obtained. Therefore, this dispersion (2) is suitable for use as a sizing agent. When this dispersion (2) is used as a sizing agent, the appearance of the fibers coated with the F layer is excellent, and in fiber-reinforced plastics containing reinforcing fibers and matrix resin, the adhesion between the reinforcing fibers and the matrix resin is improved. Therefore, the prepreg containing sizing-treated fibers and matrix resin obtained by contacting the fibers with this dispersion (2) exhibits excellent mechanical properties.

[0246] The above describes the sizing agent, the dispersion (1), the sizing treated fiber, and the dispersion (2), but the present invention is not limited to the configuration of the above embodiments.

[0247] For example, the sizing agent, the dispersion (1), the sizing treated fiber and the dispersion (2) can be supplemented with other arbitrary components in the above embodiments, or can be replaced with any component that performs the same function.

[0248] Example

[0249] The present invention will now be described in detail with reference to embodiments, but the invention is not limited thereto. Details of each component are shown below.

[0250] <Example 1>

[0251] 1-1. Preparation of each component

[0252] [F powder]

[0253] F powder-11: composed of TFE units, NAH units, and PPVE units, respectively, containing 97.9 mol%, 0.1 mol%, and 2.0 mol%, respectively, with a carbon number of 1 × 10⁻⁶ in the main chain. 6 A powder (average particle size 2 μm, bulk density 0.18 g / m³) formed from a polymer with 1000 anhydride residues (melting temperature: 300 °C, 5% weight reduction temperature: above 400 °C) 2 )

[0254] F Powder-12: A powder (average particle size 2 μm, bulk density 0.19 g / m³) formed from a polymer containing 97.5 mol% and 2.5 mol% TFE units and NAH units respectively, but without polar functional groups (melting temperature: 305 °C, 5% weight reduction temperature: above 400 °C). 2 )

[0255] [Epoxy Resin]

[0256] Epoxy resin 1: "Epikote828" manufactured by Nippon Epoxy Resin Co., Ltd.

[0257] In the polymer of F powder-11, relative to the number of carbon atoms in the main chain of 1×10 6 Each has 1000 carbonyl groups.

[0258] [surfactant]

[0259] Surfactant A: Polyoxyethylene / polyoxypropylene / polyoxyethylene triblock copolymer (Pluronic F88 manufactured by Asahi Denka Co., Ltd.)

[0260] [Carbon fiber]

[0261] Carbon fiber 1: "MR50R" manufactured by Mitsubishi Chemical Corporation

[0262] [Liquid Dispersion Medium]

[0263] NMP: N-methyl-2-pyrrolidone

[0264] [membrane]

[0265] Membrane 1: A membrane obtained by melt extrusion of polyetherketoneketone (Kepstan 7003 manufactured by Arkema, France) (thickness: 15 μm).

[0266] 1-2. Preparation and application of the sizing agent dispersion onto carbon fibers.

[0267] [Example 1-1]

[0268] (1) First, put F powder-11 (10 parts by mass) and NMP (90 parts by mass) into a container, and then add zirconia balls. Then, roll the container at 150 rpm for 1 hour to make a dispersion (viscosity: 400 mPa·s).

[0269] (2) After the dispersion 11 obtained in (1) above is applied to the carbon fiber by roller impregnation, it is dried by passing it through a drying oven at 120°C for 5 minutes. Then, it is heated and sintered in a far-infrared furnace at 340°C for 10 minutes to obtain carbon fiber treated with sizing (hereinafter also referred to as carbon fiber T1) with F powder-11 attached to the surface of the carbon fiber.

[0270] (3) The unit area weight of carbon fiber T1 oriented in one direction is 75 g / m². 2 A prepreg 1 is prepared by laminating two films 1 on both sides of a sheet-like carbon fiber substrate and then hot-melting the two films 1 and impregnating them into the carbon fiber substrate.

[0271] After the prepreg 1 is cut to the specified size, it is laminated in a steel mold with the fiber axes of each prepreg aligned in one direction. The mold containing the laminate is then compressed for 30 minutes at 380°C and 5MPa using a two-stage heating and cooling press (manufactured by Shinto Metal Industries, Ltd., a 50-ton press), followed by cooling to 200°C for several minutes to obtain a laminate 1 with a thickness of approximately 2mm. The laminate 1 and a copper foil with a thickness of 18μm are then laminated and compressed under the same conditions to obtain a shaped body 1.

[0272] [Example 1-2]

[0273] Except for replacing F powder-11 with F powder-12, the same procedure as in Example 1-1 was followed to obtain the molded body 2.

[0274] [Example 1-3]

[0275] Epoxy resin 1 (80 parts by mass) and surfactant A (20 parts by mass) were mixed and subjected to phase inversion emulsification to obtain dispersion 12. The same procedure as in Example 1-1 was followed, except that dispersion 12 was used instead of dispersion 11, to obtain molded body 3.

[0276] 1-3. Assessment

[0277] The appearance, peel strength, and water resistance of molded bodies 1–3 were evaluated according to the following criteria.

[0278] <Appearance of the molded object>

[0279] Visually inspect the surface of the molded object and evaluate it as follows.

[0280] ○: The surface of the molded body is smooth and free of bubbles.

[0281] ×: Bubbles are visible on the surface of the molded body, indicating an uneven surface.

[0282] <Peel strength of molded parts>

[0283] The molded body was cut into a rectangular shape (length: 100 mm, width: 10 mm) to obtain a sample. Then, the sample was fixed at a position 50 mm away from one end along the length direction, and the copper foil was peeled off from the laminate at a 90° angle relative to the sample from the other end along the length direction at a stretching speed of 50 mm / min. The maximum load (N / cm) applied at this time was measured.

[0284] Based on the measured values, the peel strength is evaluated according to the following criteria.

[0285] ○: Above 10 N / cm

[0286] ×: Less than 10 N / cm

[0287] <Water resistance of molded parts>

[0288] In addition to preparing samples by maintaining the molded body at 85°C and 85% relative humidity for 72 hours, the peel strength of the molded body after water absorption was measured using the same procedure as described above for <Peel Strength of Molded Body>. For each molded body, the ratio of the peel strength of the molded body after water absorption to the peel strength of the molded body measured in <Peel Strength of Molded Body> was calculated and evaluated according to the following criteria.

[0289] 〇: More than 90%

[0290] ×: Less than 90%

[0291] Table 1 shows the evaluation results of molded bodies 1 to 3.

[0292] [Table 1]

[0293] example 1-1 1-2 1-3 Appearance 〇 〇 × Peel strength 〇 × 〇 Water resistance 〇 〇 ×

[0294] <Example 2>

[0295] 2-1. Preparation of each component

[0296] [F powder]

[0297] F Powder-21: A powder (D50: 25 μm) formed from a polymer (melting temperature: 300 °C, 5% weight reduction temperature: above 400 °C) containing 97.9 mol%, 0.1 mol%, and 2.0 mol% of TFE, NAH, and PPVE units, respectively, and having polar functional groups.

[0298] F Powder-22: A powder (D50: 28 μm) formed from a polymer containing 97.5 mol% and 2.5 mol% of TFE and PPVE units respectively (melting temperature: 305 °C, 5% weight reduction temperature: above 400 °C).

[0299] F Powder-23: A powder (D50: 2μm) formed from a polymer containing 97.5 mol% and 2.5 mol% TFE and PPVE units respectively (melting temperature: 305°C, 5% weight reduction temperature: above 400°C).

[0300] Furthermore, the polymer of F powder-21 has a relative main chain carbon number of 1×10 6 Each has 1000 carbonyl groups, and F powder-22 and F powder-23 do not possess polar functional groups.

[0301] [surfactant]

[0302] Surfactant 1: Polyoxyethylene modified polydimethylsiloxane (surface tension: 26 mN / m)

[0303] Surfactant 2: Polyoxyethylene modified polyorganosiloxane (surface tension: 30 mN / m)

[0304] [Liquid Dispersion Medium]

[0305] Water (surface tension: 72 mN / m)

[0306] [Substrate]

[0307] Substrate 1: Carbon fiber (surface tension: 38 mN / m)

[0308] Substrate 2: Hydrophilic treated resin fiber (surface tension: 25 mN / m)

[0309] 2-2. Example of Dispersion Preparation

[0310] [Example 2-1]

[0311] (1) First, powder 21, surfactant 1 and water as a liquid dispersion medium are put into a tank, and zirconia balls are added. Then, the tank is rolled at 150 rpm for 1 hour to prepare a dispersion 21 (viscosity: 30 mPa·s) containing powder 21 (50 parts by mass), surfactant 1 (0.2 parts by mass) and water (49.8 parts by mass).

[0312] [Example 2-2~Example 2-6]

[0313] Except that the types and amounts of F powder, surfactant, liquid dispersion medium, and surfactant were varied as described in Table 2, dispersions 22 to 26 were obtained by operating in the same manner as dispersion 21.

[0314] The composition of the dispersions 21 to 26 obtained above is summarized in Table 2. Furthermore, coated substrates were prepared using dispersions 21 to 26 according to the following methods and evaluated according to the evaluation criteria. The evaluation results of the coated substrates obtained from each dispersion based on the following evaluation criteria are also shown in Table 2.

[0315] 2-3. Examples of manufacturing coated substrates

[0316] A dispersion 21 is applied to the surface of a strip of copper foil (18 μm thick) using a rod coating method to form a wet film. The metal foil with the wet film is then passed through a drying oven at 120°C for 5 minutes to dry it, obtaining a dry film. The dry film is then heated at 380°C for 3 minutes in a nitrogen furnace. This process produces a coated substrate 1 having a metal foil and a polymer layer (thickness: 5 μm) of molten material containing powder 21 on its surface.

[0317] Except that dispersion 22 to 26 are used instead of dispersion 21, the same operation as with coated substrate 1 is performed to obtain coated substrates 2 to 6.

[0318] 2-4. Evaluation

[0319] 2-4-1. Evaluation of the dispersion stability of the dispersion

[0320] After storing each dispersion in a container at 25°C, visually confirm its dispersibility and evaluate its dispersion stability according to the following criteria.

[0321] [Evaluation Criteria]

[0322] 〇: No aggregates were observed.

[0323] △: Fine aggregates are visible adhering to the side wall of the container. Gently stir and then disperse evenly.

[0324] ×: Aggregates were also visible at the bottom of the container. The mixture was then sheared and stirred before being redispersed evenly.

[0325] 2-4-2. Evaluation of component sedimentation rate

[0326] Each dispersion (18 mL) was placed into a solenoid tube (internal volume: 30 mL). After standing at 25°C for 14 days, the sedimentation rate was calculated using the following formula based on the overall height of the dispersion and the height of the sedimentation layer (dispersion layer) in the solenoid tube before and after standing. If no sedimentation layer was observed after standing and the state remained unchanged, the overall height of the dispersion was considered unchanged, and the sedimentation rate was 100%.

[0327] Component sedimentation rate (%) = (height of sedimentation layer) / (total height of dispersion) × 100

[0328] [Evaluation Criteria]

[0329] 〇: The sedimentation rate of the components measured by the above method is above 70%.

[0330] △: The sedimentation rate of the components measured by the above method is less than 70% but more than 60%.

[0331] ×: The sedimentation rate of the components measured by the above method is less than 60%.

[0332] 2-4-3. Evaluation of the surface coating condition of the substrate

[0333] For each coated substrate, the smoothness of its surface was visually confirmed, and the surface smoothness was evaluated based on the following criteria.

[0334] [Evaluation Criteria]

[0335] 〇: The entire surface of the polymer layer is smooth.

[0336] △: The surface edge of the polymer layer shows unevenness caused by aggregates or missing powder.

[0337] ×: Unevenness or dents caused by aggregates or powder loss are visible on the entire surface of the polymer layer.

[0338] [Table 2]

[0339]

[0340] Industrial applications

[0341] The sizing agent, sizing-treated fibers, and prepreg formed from these fibers of the present invention can produce molded articles with suppressed foaming during heat molding, excellent smoothness and other appearance, and particularly good adhesion and water resistance when formed into laminates. The resulting molded articles are applicable to a wide range of fields, including printed circuit boards, aircraft parts, spacecraft parts, automotive parts, ship parts, civil engineering materials, oil excavation components, hydrogen storage tanks, hydrogen storage tank pressure vessels, wind turbine blades, and sporting goods.

[0342] Furthermore, the above results clearly demonstrate that this dispersion (2) exhibits excellent dispersibility and dispersion stability. Moreover, the surface uniformity of the coated substrate formed by this dispersion (2) is excellent, resulting in a good appearance. Therefore, it is believed that the coated substrate obtained by coating the substrate with this dispersion (2) can highly exhibit the properties of the F polymer. Additionally, when this dispersion (2) is used as a sizing agent, a sizing effect can be obtained. Prepregs containing fibers and matrix resin treated with this dispersion (2) exhibit excellent mechanical properties.

[0343] Hereinafter, the entire contents of the description, claims and abstract of Japanese Patent Application No. 2020-118558, filed on July 9, 2020 and Japanese Patent Application No. 2020-148433, filed on September 3, 2020, are incorporated herein by reference as disclosure of the present invention.

Claims

1. A sizing agent which is a sizing agent formed from a dispersion liquid containing a powder of a hot-melt tetrafluoroethylene-based polymer having an average particle diameter of 10 to 100 μm, a surfactant having a surface tension of 28 mN / m or less, and a liquid dispersion medium, the surfactant being a silicone-based surfactant, a glycol-based surfactant, or an alkyl amide ether-based surfactant, the content of the surfactant being 0.0001 mass part or more and 0.01 mass part or less with respect to 1 mass part of the powder of the tetrafluoroethylene-based polymer, the tetrafluoroethylene-based polymer being a tetrafluoroethylene-based polymer having a perfluoro(alkyl vinyl ether)-based unit and a polar functional group, or a tetrafluoroethylene-based polymer containing 2.0 to 5.0 mol% of a perfluoro(alkyl vinyl ether)-based unit with respect to the total units but not having a polar functional group.

2. The sizing agent of claim 1, wherein, the tetrafluoroethylene-based polymer having a melting temperature of 280 to 325°C.

3. The sizing agent of claim 1 or 2, wherein, the tetrafluoroethylene-based polymer having a 5% weight reduction temperature of 360°C or more as measured according to JIS K7120.

4. The sizing agent of claim 1, wherein, The tetrafluoroethylene-based polymer having a polar functional group is a tetrafluoroethylene-based polymer having a carbonyl group-containing group, the number of which is 10 to 5,000 relative to the number of main chain carbons. 6 10 to 5,000.

5. The sizing agent of claim 1, wherein, the content of the tetrafluoroethylene-based polymer being 25 to 60 mass parts with respect to 100 mass parts of the liquid dispersion medium.

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